Paddleducks
Other Marine Models => Live steam => Topic started by: kvom on March 26, 2010, 08:55:25 AM
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I started my build of this model engine the past few days. This will likely be a very long term project, but you have to start somewhere. This is the same engine "JimmiBondi" built in an earlier thread that has unfortunately lost its photos.
I have gotten my new CNC mill mostly straightened out and myself through the early learning process. The first two useable parts produced with the mill are the outer frame plates. There are two earlier attempts in the scrap heap.
(http://www.pbase.com/kvom/image/122991386/large.jpg)
I also made a start on the inner frames by preparing the stock blanks (5"x10"x3/8") and drilling the many holes:
(http://www.pbase.com/kvom/image/123032286/large.jpg)
The frame plates are 6061 aluminum rather than the steel used in the original. By milling the hornblocks integral with the frame the issue of attaching them is eliminated.
I also made a "trial" cylinder in aluminum before doing the actual ones in cast iron.
(http://www.pbase.com/kvom/image/122683196/large.jpg)
(http://www.pbase.com/kvom/image/122683201/large.jpg)
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Very nice! i have had my eyes on this build at HMEM but great that you are posting you're build here! i will definitely follow this, what type of mill are you using? any pictures ?
hope for more updates SOON!
Regards// Victor
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kvom.......& welcome to PD's.......I think many members will :whistle & watch your posings :crash with great interest ..... :hammer Derek :beer
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Good luck with your build, it should be a very nice engine.
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I machined the first inner frame yesterday. No real problems and the trial cylinder fits nicely into the through slot.
(http://www.pbase.com/kvom/image/123074912/large.jpg)
(http://www.pbase.com/kvom/image/123074913/large.jpg)
Unfortunately I didn't have as much luck today on the second. The work raised up from the fixture plate cutting the outline and unfortunately the endmill was in a critical areal where I couldn't save it. :( This will have to wait as I have no more suitable aluminum stock.
Guess I'll just work on finishing the CI cylinders next.
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I built this engine from castings supplied by Reeves. I only had a unimat 3 lathe at the time I have yet to fit it into a boat. One thing I found, on my plan the bolts holding the cylinder, frame and steam chest coincide with the cylinder end plate bolts. R.G.Y
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Thanks for the heads-up. There is quite a bit of material around the bore, so it might be possible to alter the bolt circle or the start angle to avoid the interference. I'll check when I draw up the back of the cylinder. I am thinking to use 8 bolts on the rear cover for appearances rather than the 6 shown in the plan.
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I redid my drawing of the cylinder face incorporating the clearances for the mounting studs. Indeed a 6 hole bolt circle gives only a 1/16" clearance between the two lower face holes and the front/rear studs. If I use a 8-hole bolt circle, only the bottom face hole has a problem. And on the front cover that hole is countersunk to provide for the guide bars. So I plan to use the 8-hole pattern omitting the bottom hole on the front cover and using a dummy bolt on the rear.
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Today I decided to skip any CNC work and actually turn the cranks for a change. I decided to make the valve slides as I had some suitable material. It is a lump of the mystery brass I used previous in Bogs' engine. It's a lot harder than 360 and needs smaller cuts too.
So the first task was to square two blocks and then reduce to size: 7/8 x 13/16 x 5/8.
(http://www.pbase.com/kvom/image/123109955/medium.jpg)
Next I machined out the 1/16" deep valve pocket, which is 5/8" square. I used a centercutting .25" endmill to plunge to depth in the center, then moved along the perimeter.
(http://www.pbase.com/kvom/image/123109957/medium.jpg)
Next I cut the 3/8" slot. As I broke my last remaining 3/8" endmill I used a 5/16 to cut to depth, then widened it with the side flutes. Then with the same endmill I made the cheek cuts.
(http://www.pbase.com/kvom/image/123109958/medium.jpg)
Last is the 1/8" slot to hold the eccentric rod. I used a 1/8" endmill to cut to depth, then a ball-endmill to round the bottom of the slot.
(http://www.pbase.com/kvom/image/123109961/large.jpg)
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Yes I moved the covers around one six of a turn, on the blank end. Had to fill one set of holes in the rod end cover, the one where I found the mistake. As of course can't turn that end. R.G.Y
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My CNC mill decided to go on the fritz (limit switches not registering properly), so I started looking at materials needed for future parts as well as parts to make on the lathe in the interim. While I did do have brass stock for the cylinder covers, it is a bit larger than required, and I hate to have to machine away 25% or more. I found some 1-5/8" round 260 brass online and ordered a foot, so that will need to wait.
I do not have any brass or CI suitable for the steam chest other than some 2" round, which means losing most of it to swarf. I do have CRS and aluminum barstock that would work. Is there any reason not to use steel or aluminum for the steam chest?
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Rather than machining, I spent a good deal of time yesterday reading over the magazine articles again and doing some planning. I also drew up some of the parts in CAD.
The part that's giving me a problem is the lifting link shown on page 476 of the 22 March 56 issue. The scanned drawing is very hard to decipher. Does anyone have the original plans and can scan that page?
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The plans for the engine are in our Downloads section....
http://www.paddleducks.co.uk/smf/index.php?action=downloads;sa=view;down=197
Regards
Eddy
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Thanks Eddy. Your scanned copies are much clearer than the site from which I downloaded the plans.
Having decided to make the steam chests from 6061 because of material availability, I started on the first one by squaring a suitable block and milling it oversize in all 3 dimensions. Then I center drilled both ends to hopefully end up with a straight line for the valve rod. Next I chucked in the 4-jaw and used a live center in the tailstock to align the block with the center holes. It was not really necessary to be extra precise as I will be drilling and reaming the holes on the mill later. The objective here is just to turn the round boss that will later hold the packing gland. The face of the boss will serve as the datum for further machining.
(http://www.pbase.com/kvom/image/123199067/large.jpg)
Here's the blank ready for milling, along with the blank cover plate that will also be milled to fit.
(http://www.pbase.com/kvom/image/123199070/large.jpg)
The mill has some issues with the limit switches, so I'm waiting for the vendor to come up with a fix. So using the manual mill and lathe in the interim. The block of aluminum I have for the other chest is a bit bigger, so I decided to put it off for another afternoon.
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I worked on the cylinders the past two afternoon; after fubaring one I had to restart that one with a new strategy. I used the manual mill to reduce the round bar to size on 5 sides, then milled the round top on the CNC mill. It was slow going squaring the sides as CI needs slow SFM (400 rpm, 5/8 endmill), slow feed (4 IPM), and a modest DOC (.100 shook the mill a little too much for comfort, but .075 seemed OK). Here's the result of those ops:
(http://www.pbase.com/kvom/image/123458984/large.jpg)
Then I did the bases. I'd already run the CNC program with the aluminum trial cylinder, so this part went smoothly:
(http://www.pbase.com/kvom/image/123458985/large.jpg)
The holes were drilled .101 to be tapped for 5-40 studs. The next job will be to drill the bore and the cover mounting holes (also 5-40).
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Some more work on the cylinders after watching the Masters golf:
First I used the CNC mill to center drill all the holes in one face each cylinder, then a #38 drikll 1/4" deep for the cover mounting studs. Next I moved to the manual mill to drill the bore 11/32 and then ream .376". I preferred to drill manually for feel. The bore holes now had a sliding fit with a piece of 3/8" drill rod.
(http://www.pbase.com/kvom/image/123520133/large.jpg)
Now I used the drill rod in the lathe tailstock to position the cylinder body in the 4-jaw chuck:
(http://www.pbase.com/kvom/image/123520137/large.jpg)
Then I used a 23/32" drill with a MT2 shank that I borrowed from school to drill the bore. 400 RPM and a slow hand feed with frequent pecking.
(http://www.pbase.com/kvom/image/123520139/large.jpg)
Then reaming to 3/4" with the reamer held in a chuck in the tailstock:
(http://www.pbase.com/kvom/image/123520141/large.jpg)
Now they're ready to drill the steam input and exhaust holes.
(http://www.pbase.com/kvom/image/123520142/large.jpg)
The plans show 6 studs for the cover plates, but as drawn the two bottom holes interfere with mounting holes in the base. So I went with an 8-hole pattern omitting the bottom hole, which would interfere with the steam inlets.
Spent a few hours more working on the cylinders this afternoon. This time it was drilling the inlet and exhaust holes. The inlet holes on each side are drilled from the lower "lip" of the borem on each side to intersect with the pockets milled in the base. Westbury thankfully drew the plans so that the angle of the inlet holes is 30 degrees relative to the bore. This means that the cylinder can be positioned in the milling vise with a simple 30-60-90 angle bar.
(http://www.pbase.com/kvom/image/123549265/large.jpg)
I first needed to mill a flat at the bottom of the bore, then center drill the three holes separated by 3/32". Then a 3/32" drill for the inlet holes. Repeat on each end of each cylinder.
(http://www.pbase.com/kvom/image/123549266/large.jpg)
The exhaust hole connects one side of each cylinder to the central pocket, and once again a 30-60-90 angle bar serves to set the cylinder in the vise. the exhaust passage is 3/8" diameter, and intersects with one of the stud holes. However, there is enough material left to thread for a stud.
(http://www.pbase.com/kvom/image/123549267/large.jpg)
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It's coming along very nicely Kvom, especially when you consider the modifications that have to be made because of errors in the drawings!
Regards
Eddy
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Beautiful work! you are getting some really neat cylinders here! it's hard not to be jealous! for some parts i wish i had a cnc mill he he!
Keep on with the good work you doing!
// Victor
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To those who responded or are following along, thanks for the support. I'm going to need it.
My back is sore from bouncing around in a friend's Jeep this weekend, so I'm limiting the amount of time standing up in the shop in front of the machinery until it calms down. Today I went for a fairly simple part, the steam chest covers, for which I had already sized up stock blanks previously.
The CNC mill had 4 operations: spot drill the mounting holes, drill them, mill a 1/32" pocket on one side with a 3/16" endmill, and then finish the pocket with a 1/16" endmill to get the corners as close to square as possible.
(http://www.pbase.com/kvom/image/123585049/large.jpg)
The holes are drilled with a #30 bit to clear the 5-40 studs that will connect the cylinders, steam chest, and cover.
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With my back still a bit sore, I spent yesterday evening drawing up a few more parts in CAD. I had previously drawn the eccentric strap, and having formulated a plan for the machining process I decided to givem this a shot today. The first task was to mill two pieces of 1/4' thick 360 brass to size, 1.5"x.75".
The first step is milling the profiles on both pieces. Since there is only .25" of the .75" width left chucked in the vise afterwards, I decided to put softjaws in the vise and milled a slot to clamp the pieces:
(http://www.pbase.com/kvom/image/123621701/medium.jpg)
The first pass on the profiles was done with a 1/2" endmill to remove the majority of the material, followed by a 1/8" endmill for a finishing pass. Here's the result:
(http://www.pbase.com/kvom/image/123621702/medium.jpg)
Next clearance holes for 2-56 screws were drilled manually.
(http://www.pbase.com/kvom/image/123621703/medium.jpg)
Here progress had to stop as I have no 2-56 nuts to clamp the two pieces together for future milling. Once I obtain the nuts, I will use them to clamp the two pieces securely together, then face mill both sides flat to a final thickness of 3/16", and then bore the central 1" hole for the eccentric. After that it remains to drill the oil hole on the right side piece and drill/tap holes for mounting the eccentric rod on the left.
In the meantime I'll try to locate some more brass for the second strap.
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Today's parts are the "weigh shaft arms", which form part of the reversing linkage. They are a press fit on the weight shaft and are connected to the lifting links via a screw. So the first order of business was to make a fixture plate with a piece of 3/16" drill rod and a clearance hole for a 5-40 screw. The holes are 1.5" apart. The larger hole was drilled 1/64 small and then reamed .001 under for a press fit.
The blank stock was milled square. Then the 3/16 hole was drilled and reamed to match the fixture, and the smaller hole was tapped 5-40 on the tapping stand:
(http://www.pbase.com/kvom/image/123647628/large.jpg)
Next the blank was pressed onto the drill rod, and the other end attached from the bottom with a 5-40 SHCS. The piece was thus held down to the fixture plate securely.
(http://www.pbase.com/kvom/image/123647629/large.jpg)
The fixture and stock were all prepared on the manual mill, but now the fixture plate wasm mounted on the CNC mill to mill the final form.
(http://www.pbase.com/kvom/image/123647630/large.jpg)
The first one on the right came out "off center". It would still be useable since the holes are correctly spaced, but I'll plan to make another one later. I have no idea why there is a discrepancy in setting the zero. For the second one I eyeballed a .003 correction in the Y direction.
Since all the milling was done with a 1/4" 2-flute endmill, no tool changes were needed, so the milling takes only a couple of minutes at most. The prep and setup tool a couple of hours.
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Why did you not do the drilling of the holes with the CNC ?
Regards,
Gerald.
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Gerald,
In retrospect that might have been better. Since I have a DRO on the manual mill I expected to have an accurate registration. Drilling the parts manually is fine, but it would be better to drill the fixture on the CNC using a vise stop. The fixture needs to be removed to press the work onto the fixture and then reclamped in the vise.
Today I made a start on the crossheads. I decided to make these from 6061 Al rather than brass as I had the right size material. So the guide bars will be brass to provide a good sliding surface. The crosshead requires machining on three sides, so this is the left side where the piston rod attaches. Material is 1x1x3/8" with 1/8" spigot. CNC milled the spigot and drilled to tap for 10-32 thread.
(http://www.pbase.com/kvom/image/123671237/large.jpg)
Once again the CAD/CAM work takes the most time, then sizing the stock on the manual mill. The actual spindle time on the CNC mill is less than a minute, as most of the time is setting the zeros, changing tools, etc.
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Spent a little bit of time after dinner in the shop to machine the top side of the crossheads. Here there are two crossed oil grooves 1/16" wide by 1/32" deep, plus a 1/8" oil hole (which presumably allows oil to reach the conrod link pin). As usual, programming and setup take all the time, and the machining is rapid.
(http://www.pbase.com/kvom/image/123700338/large.jpg)
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I finished the 3rd machining operation on the crossheads this morning. Drill 4 #30 holes for mounting the side plates and then mill then space for the conrod to swivel vertically.
(http://www.pbase.com/kvom/image/123717467/large.jpg)
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Nice! Please keep us posted.
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Today's contribution is fabrication of the expansion links, wich form part of the reversing mechanism, one link per cylinder. A link is connected to 4 other parts.
1) The circular slot is connected to the end of the valve rod, which slides along the slot;
2) The center hole is connected to a lifting link that is in turn connected to a weigh shaft arm.
3) The two outer holes are connected to two eccentrics.
In operation, the weigh shaft is turned causing the lifting link to raise or lower. This in turn rotates the expansion link which reverses the timing of the eccentrics, thus reversing the engine's rotation.
These parts are seemingly ones where CNC gains the most in terms of effort. To make manually would require a lot of filing to achieve the contours, as well as the rotab to make the slot accurately. Once the CAD/CAM was complete, each part took less than an hour to machine, mainly because of numerous tool changes.
(http://www.pbase.com/kvom/image/123764895/large.jpg)
The part on the right shows where material was left on each end after CNC work; this was necessary to keep the work secured in the milling vise. I programmed a shallow radial cut to indicate the final contour. The ends were then finished on the manual mill using this cut as a guide for positioning the piece in the vise.
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I am making parts in a "random" order as the spirit guides me, or as I have material or tools to do do. Today I decided to work on the steam chests some more. First I drilled and pocketed the one I started some time ago, and then started on the second one. This time I milled the circular spigot rather than turning on the lathe.
(http://www.pbase.com/kvom/image/123805168/large.jpg)
I still have drilling and tapping to do on both, and the first one is a bit thicker than in the drawing.
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looks great,
I do the same, do parts as i feel, it helps, sometimes you have motivation for doing one thing and the next day something else, i posted some pictures of my progress on the engine I'm making in my "Scott boiler" build thread check it out if you feel to!
keep those pictures coming :)
// Victor
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Victor, I did see your thread. Looks good! The engine has a lot of similarities to the Bogs' engine I built, although yours is more pleasing to the eye. the round cylinder blocks and crosshead guides are more attractive for sure.
My next effort is the "big ends", or crankhead bearing as Westbury termed it. Starting material is some 1" diameter brass rod. On the lathe I faced, then parted off 4 pieces about .7" long, and then milled the parted side flat. To hold the pieces repeatably and securely in the CNC milling vise, I milled a 1" diameter pocket .2" deep in the aluminum soft jaws:
(http://www.pbase.com/kvom/image/123858729/large.jpg)
(http://www.pbase.com/kvom/image/123858730/large.jpg)
Then the side profile could be milled as well as the mounting holes. Once removed from the vise, the round holding stub was milled from the bottom and each piece brought to size (5/16").
(http://www.pbase.com/kvom/image/123858731/large.jpg)
(http://www.pbase.com/kvom/image/123858732/large.jpg)
The 5-40 threaded rod I will use to connect the bearing halves and the conrod measured .118", so I drilled the holes with a #31 (.120) for a close fit.
Finally the pairs were clamped in the milling vise to finish the sides. After milling the round boss, the crank hole was created by drilling 11/64" and then reaming .376 for a sliding fit on the 3/8" crank.
(http://www.pbase.com/kvom/image/123858734/large.jpg)
These little parts took the best part of two afternoons in the shop, not counting CAD/CAM time.
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Thanks Kvom,
the "big ends" look great, really nice with the edge on the side. could you post a picture of the mill you are using? could be fun to see!
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Here's a pic of the mill:
(http://www.pbase.com/kvom/image/123884026/large.jpg)
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No CNC work at all as I try to make a conrod to ET's plan.
Rather than steel, this is some 1" diameter brass rod, of which I have 7' and thus enough to screw up many times. Mounted in the lathe, I turned the following piece:
(http://www.pbase.com/kvom/image/123918501/large.jpg)
Not having a ball turner, I used Marv Klotz's ball turning program to output a schedule for turning a 1/2" diameter ball using 5 degree angle increments. The shaft was turned to 3/8" with the neck nearest the ball grooved to 1/4". From the end of the ball to the end of the shaft is 3.25".
Next the piece was mounted in the Bridgeport vise held between two V-blocks. A 1/4" endmill was used to make a flat on the side of the ball plus cut a flat that will be the finar form of that end of the rod. The ball was then center drilled, drilled, and reamed to 1/4" diameter.
(http://www.pbase.com/kvom/image/123918504/large.jpg)
A second flat was milled on the large end to provide a reference for clamping to bill the large end on the opposite side.
(http://www.pbase.com/kvom/image/123918506/large.jpg)
The next operation will be to put it back in the lathe and use the taper attachment to taper the shaft from 3/8 to 1/4 over its length.
*** edit ***
Looking at the drawing and doing an eyeball fit, I realized that the sides of the ball end need to be milled flat in order to fit the crosshead. Luckily it is easy to do this at this stage this morning. Had I waited until assembly chucking might have been a problem, and certainly I would have needed to do it by filing.
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Thanks for lookig ariz.
Today I decided to try to finish the first conrod, so after a much needed vacuuming of the machinery I set up the Monarch's taper attachment. Setting the little indicator on the 2-degree mark, I measured the actual taper angle as calculated from the XY DRO reading: 2.02 degrees, close enough!
After cutting the taper as close to the ball end as possible, I gave the shaft a quick polish with some 320 grit paper and than Scotchbrite. On this machine it's better to cut a taper toward the large end to take up any backlash in the crossfeed screw.
(http://www.pbase.com/kvom/image/123979712/large.jpg)
Earlier I had been worried about whether I could easily clamp the conrod vertically to drill the mounting holes and mill it to length, as it's over 1" longer than the jaws are deep. Luckily the vise jaws overhand enough to do so.
(http://www.pbase.com/kvom/image/123979713/large.jpg)
Finished with the big end bearing attached:
(http://www.pbase.com/kvom/image/123979714/large.jpg)
I thought it interesting to find that Reeves in England still sells casting for this engine (at 550 pounds, $800 :o). Their website didn't saw which parts are included.
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Yesterday I made the second conrod taking advantage of lessons learned in making the first. The main change on the lathe was turning the shaft to 1/2", the diameter of the ball end, rather than the final major diameter of 3/8. So after cutting and filing the ball as before, I could place the shaft into a 1/2" 5C collet and the square collet block.
(http://www.pbase.com/kvom/image/124034997/large.jpg)
The 4.10" workpiece was just long enough so that the ball and part of the end were visible. Then I was able to mill flats on both ends, taking 1/32" off the ball and .200 off the end. After drilling and reaming the hole in the ball, I could flip the collet block and mill matching flats on the opposite sides.
(http://www.pbase.com/kvom/image/124034998/large.jpg)
Next I reversed the piece in the collet so that the large end was fully exposed, and used the height gauge on the surface plate to set the milled flat horizontal:
(http://www.pbase.com/kvom/image/124034999/large.jpg)
Now I could mill parallel flats to form the sides of the large end of the conrod. Then it was back to the lathe to reconnect the taper attachment and turn the shaft taper as before.
The remaining tasks were to mill the large end down to final length and drill the mounting holes. I discovered that it was easier to clamp the piece between two parallels than to use the tops of the vise jaws. In order to keep the parallels tight against the jaws, I inserted some pieces from my gauge block set in the opposite end.
(http://www.pbase.com/kvom/image/124035000/large.jpg)
Final result:
(http://www.pbase.com/kvom/image/124035001/large.jpg)
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I'm really enjoying this thread! Keep it coming please!
All the best
Stuart
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I goofed off all afternoon, so after dinner I decided to knock out the 4 cheek plates of the crossheads.
(http://www.pbase.com/kvom/image/124045992/large.jpg)
The CNC milling/drilling took only a half hour. Squaring the pieces, milling the jaws, and tapping took a couple of hours altogether. While the 5-40 SHCS are good for now, I think either studs/nuts or hex head screws will look better in the end.
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I was supposed to go on a 2-day offroad event, but tweaked my back and decided it was not for the best to go. Since I can stand without discomfort, I spent the afternoon in the shop. Today's goal was to make progress on the cylinder covers.
Having obtained a length of 1.5" brass rod, the process on each of the 4 covers was to start on the lathe:
1) face
2) facing cut to create a .75" spigot .06" deep, to serve as a seal for the cylinder bore
3) part off
The rest was done on the CNC mill. A 1.5" round pocket .100" deep was milling in the soft jaws of the vise to hold each cover and to ensure that each was centered. From then on it was a matter of milling and drilling.
The end result of the days's effort is shown here:
(http://www.pbase.com/kvom/image/124091600/large.jpg)
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Hi PD's...... personally I suggest that kvom's effort :hammer ... in his machine shop :clap is far better time spent than any two day jaunt tracking off road :41 ...... but :shhh him :whistle - Derek
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I have about as much invested in the Jeep as I do in machinery, so it should get equal time to be fair. 8)
Nevertheless, it was back to the shop.
This afternoon's effort was to make the two slide-bar brackets. These attach to the inner frame and secure the far end of the bars on which the crosshead slides (the other end of the bars attach to the cylinder cover).
(http://www.pbase.com/kvom/image/124113807/large.jpg)
The machining sequence was as follows:
1) square 2 pieces 1x1.5x.375 inches on the manual mill
2) CNC the main "pocket" using a 7/16 endmill
3) CNC the inner profile with a 1/8" endmill
4) Back to the manual mill to make the outer 45-degree cut.
5) Drill the clearance holes for the 5-40 screws that will attach the bars.
To be done: file the edges of the inner slots where the bars attach, and drill/tap holes in the sides to attach to the frame. This latter operation will be done once the positions of the brackets are known exactly (i.e., the crosshead slides smoothly between the bars with no binding).
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I had been trying to decide which thread to use for the cylinder gland nuts. ET specified 1/2-26, which is not a unified thread. The choice is between 1/2-20 UNF and 1/2-28 UNEF. I recently acquired a 1/2-28 tap, and it appears that a finer thread makes for easier adjustment of the gland. But not having a matching die, I needed to know if I could cut a good external thread for the nut on the lathe.
Today I decided to do a little experiment before cutting any metal in anger.
I chucked up a small piece of aluminum rod, drilled it 31/64, and used the thread-forming 1/2-28 tap to thread the hole. This was the first time I'd used such a tap, and in aluminum it worked great. No chips to clear, and with such a small thread depth in softer metal it went rapidly. So now I had a "nut" to test with.
The second part of the experiment was to cut some external threads in steel to match the nut. In the past for small threads like 5-40 and 6-32, I'd cut partial threads on the lathe to ensure that they were straight, and then finish them with a die. Since I don't have a 1/2-28 die, I'd need to cut the entire thread on the lathe. I turned some 12L14 rod down to .500" and cut the thread in about 6-7 passes, with the last couple being a thousandth DOC.
Here's the result:
(http://www.pbase.com/kvom/image/124152343/large.jpg)
So it looks as if I ought to be able to make the gland nuts with this thread.
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Latest parts made are the two valve forks that connect the valve rod to the die block, which slides inside the link.
(http://www.pbase.com/kvom/image/124184541/large.jpg)
The screws show where the threaded valve rod attach via 5-40 threads, plus a lock nut for adjusting the valve travel.
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Nice work!
Regarding this engine, some suggested to me that it would be better to build it so that the cylinder valve covers face outwards. This allows much easier adjustment and maintenance and should be easy enough to do at this stage.
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You couldn't just move the cylinder to the other side of the frame. But you could switch the two engines left to right so that the outer frame becomes inner and vise-versa. Then the cylinder is on the inside and the valve/eccentrics on the outside.
On the face of it that could work. You'd need to change the staybolt and weigh shaft lengths. The downside is that the engine would be quite a bit wider and might not fit well in a typical boat.
Today's parts are the valve rods and the valve buckle. Rods are 1/8" drill rod threaded 5-40. For the setscrew on the buckle, I drilled and tapped for a 2-56 screw and countersunk for a SHCS.
(http://www.pbase.com/kvom/image/124215693/large.jpg)
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You couldn't just move the cylinder to the other side of the frame. But you could switch the two engines left to right so that the outer frame becomes inner and vise-versa. Then the cylinder is on the inside and the valve/eccentrics on the outside.
That's exactly what I meant.
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My task for the past two days was to make the two cylinder gland nuts. No CNC work for these. :P
I had a short piece of 3/4" diameter brass, so the first task was to turn down the outer ends to 1/2" and thread them 1/2-28. By doing the threads at each end I was able to have a nice amount of material held in the lathe collet, and as well I knew the DRO DOC settings for the second thread once the first was done.
(http://www.pbase.com/kvom/image/124246952/large.jpg)
I had previously tapped an aluminum "nut", so I had something to test when the thread was good. Next each end was parted off:
(http://www.pbase.com/kvom/image/124246953/large.jpg)
The nut now comes in handy again. I parted off each end, then threaded the gland into the nut so that the parted end could be cleaned up:
(http://www.pbase.com/kvom/image/124246954/large.jpg)
Now the nut/gland/collet were transferred to the hex collet block on the mill to drill the 6 radial holes for tommy bars (used to tighten the nut onto the gland):
(http://www.pbase.com/kvom/image/124246955/large.jpg)
The drilled nuts:
(http://www.pbase.com/kvom/image/124246956/large.jpg)
The hole for the piston rod will be drilled with the nut screwed into the cylinder cover to ensure concentricity.
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Over the past three days I've been trying to make progress on the eccentric straps, all the while having life get in the way. I recently found a slotting saw via Craigslist, so it was a big help in cutting out the blanks for the straps from some 1/8' thick brass sheet. Each of the 8 pieces was machined to 1.5x.75". All three dimensions are slightly larger than the final target size.
(http://www.pbase.com/kvom/image/124447971/medium.jpg)
I should have made a spare as I later ruined one and had to go back and make another. :'(
Then each piece has a profile cut on the CNC mill: roughing cut with a .25" endmill, and a finish cut with a 1/8" endmill. I had previously made another but it was messed up since I had a poor design for clamping in the vise. This time I left a flat on each side; on the forward side this will later be milled away.
(http://www.pbase.com/kvom/image/124447973/large.jpg)
Then the mounting holes were drilled. Here I used softjaws on the vise to machine a holding pocket. This allowed the hole spacing to be quite precise. Now I'm able to screw the two halves together with 2-56 screws and nuts. The screws will be trimmed at some point.
(http://www.pbase.com/kvom/image/124447975/large.jpg)
Remaining to be done:
1) Bore 1" diameter hole in each to contain the eccentrics
2) Mill straps to 3/16" thickness (or to match slot in the eccentric disks), and remove 1/16" from rod mounting surface
3) Drill and tap mounting holes for the eccentric rods (4-40)
4) Finish profile and drill oil hole
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Today was the most shop time I've put in for quite a while: over 7 hours. Too much like work?
The first task was to mill out the eccentric bores. I did a "circle mill" on the CNC mill rather than use a boring bar. I expect this will be accurate enough, although there was a few thousands variation after the operations were done. I suspect the brass spring back a bit after being compressed by the vise.
(http://www.pbase.com/kvom/image/124475262/large.jpg)
Next I decided to tackle the eccentric rods, which are possibly the trickiest parts to make of all. The first operation was to CNC mill the side profile .200" deep in some aluminum. I did two of them in some scrap pieces, and the other two in some material I cut to size.
(http://www.pbase.com/kvom/image/124475265/large.jpg)
Next I milled a pocket in the vise's soft jaws to match the profile. Broke one end of a 2-ended 1/16" carbide endmill taking too deep a cut. :( the pocket was milled .125" deep. Now I could invert the work pieces, hold them precisely in the vise, and mill the other half.
(http://www.pbase.com/kvom/image/124475267/large.jpg)
(http://www.pbase.com/kvom/image/124475269/large.jpg)
Finally, with the rod held in the pocket I drilled the 1/8" hole where it will connect to the expansion link.
(http://www.pbase.com/kvom/image/124475271/large.jpg)
Here's the stopping point for the night.
(http://www.pbase.com/kvom/image/124475273/large.jpg)
Still to do:
1) Mill the top profile
2) Mill the slot for the expansion link
3) Drill mounting holes for attaching to the eccentric strap
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To finish the eccentric rod this afternoon, I first milled the 3/16" wide slots. Since I made the links thicker than called for in the plans, I would need to either mill them thinner or else make this slot wider. I looked at the assembly elevation, and it looks as if there is not a lot of space. So I will need to thin the links and the eccentric straps.
My setup for milling the slots was a little non-standard, since one side of the rod isn't flat:
(http://www.pbase.com/kvom/image/124499669/large.jpg)
(http://www.pbase.com/kvom/image/124499670/large.jpg)
With the slots done, it was back to use the pocket in the vise jaws to face off the other side of the rod:
(http://www.pbase.com/kvom/image/124499671/large.jpg)
Westbury milled a radius between the "head" and the shaft, although I rather like it the way it is.
Finally, I drilled the strap end with a #32 drill for the 4-40 mounting studs.
(http://www.pbase.com/kvom/image/124499672/large.jpg)
Normally I would want to turn the eccentrics next, but since they need to be fitted to the straps, the next task will be milling the straps to 3/16" thickness.
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The past few shop hours were devoted to making the guide bars; in theory a simple task. Four brass pieces ~4"x3/8"x1/8" with a few through holes and a slight bevel on one end of each. However, the only suitable brass stock I possessed was a couple of feet of 1/2" square bar. Not wanting to mill away 3 quarters of the brass, I decided to use my new little slotting saw to cut the bar in two lengthwise. While I succeeded eventually, the geometry of the saw/vise/parallels required a semi-bizarre setup and most of an afternoon to accomplish the cuts.
Once I had 4 rough pieces, the final dimensions need to be fairly precise so as to allow the crosshead to slide smoothly and straight. So I proceeded using quite small cuts on the mill with frequent repeated measurements. The bevel on the ends is needed to provide clearance to the conrod when the crank journals are at their highest and lowest points. While I expect that they may need to be adjusted at assembly time by filing, I decided to
try to use my sine bar setup for the first time to mill the 15 degree angle.
(http://www.pbase.com/kvom/image/124680693/large.jpg)
For many here, use of a sine bar to set a precise angle is old hat. I had done it once before at school, but this was the first use at the home shop. Since the sine bar is 5" long, I needed to elevate the free end with gauge blocks equal to 5" x sin(15), or 1.294". To do this, I wrung together gauge blocks of thickness .05, .144, .1, and 1 and lowered the bar onto the stack. After locking the joint, the top of the bed was at a quite precise 15 degrees.
Once I had drilled the mounting holes in the bars, I did a quick "finger assembly" to check out the fit of the associated parts.
(http://www.pbase.com/kvom/image/124680694/large.jpg)
The support brackets on the other end of the bars need to be filed so that the bars fit closely. That's a task for another time.
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Today I made a bit more progress on the eccentric straps. The first task was to machine the thickness to 3/16". I had previously taken off about .030" from one side on the mill, but found that for the other side I was not getting a secure hold in the vise. Thanks to a suggest by Ed Taylor, I turned a mandrel from some 1-1/4" aluminum round, forming a 1" diameter spigot to match the bore of the straps.
(http://www.pbase.com/kvom/image/124723040/large.jpg)
Each strap in turn was tightened onto the spigot, with the back edge providing alignment. Then I was able to remove the excess width taking small cuts of .005-.009" per pass.
(http://www.pbase.com/kvom/image/124723039/large.jpg)
Next, the half that attached to the eccentric rod was milled to a height of 11/16 from 3/4, and the mounting holes were drilled and tapped for 4-40 screws.
(http://www.pbase.com/kvom/image/124723041/large.jpg)
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:a102 ....a 6 jaw self centering lathe chuck?............shows my machining days were many years ago .... :c017 - Derek
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Derek, that 6-jaw Cushman chuck was sold by Monarch along with my 1942 10EE lathe. So it and the lathe are 78 years old. ;D
Today I did a trial assembly of an eccentric strap to its rod. I discovered soon enough that the radius I milled between the staft and the base interferes with the 5-40 nut.
(http://www.pbase.com/kvom/image/124744631/large.jpg)
So I came up with this setup on the mill to remove the radii:
(http://www.pbase.com/kvom/image/124744632/large.jpg)
With the rod now mountable a loose assembly of partial valve components looks like this:
(http://www.pbase.com/kvom/image/124744633/large.jpg)
I need to figure out the best way to make the "studs" cut from some 4-40 allthread look good. This time I used a dremel-type cutoff wheel and then passed a die over the cut end. I also only threaded the strap holes with a plug tap, and in the 3/16" deep holes I get 4 full threads. I can make a bottoming tap by grinding the tip off a second plug tap if that's not enough; doing so would get me 6-7 full threads.
The engine won't get any further progress for a while, as I will be vacationing in Utah for 3 weeks starting on the 25th. I'm driving out towing my Jeep for some offroading at Moab. 1800 mile drive each way. :P
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Back from travelling, so time to start up the build again. :)
Today's parts are the valve rod tail supports, which screw into the back of the steam chest and support the end of the valve rod.
While these parts are pretty simple, they took quite a while. All operations are manual.
(http://www.pbase.com/kvom/image/126258403/large.jpg)
Started with some 3/8" brass rod and turned the closed end down to 1/4, then rounded the end with a form tool. Then parted off for as total length of 3/4".
With the closed end chucked in a 1/4 collet, I turned the open end down to 1.4 diameter for 1/4 length, then drilled 1/8" hole 5/8 deep. Next threaded 1/4-20 ( don't have a 1/4-28 die, must get one).
Finally milled the hex portion using hex collet block.
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Looks like shes coming along nicely. great looking work
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Today I made some progress on finishing the steam chests. Basically drilled and tapped the holes on either end for the valve rods: 1/4-20 for the back end and 5/16-24 for the glands. With the rod supports in place, here's a trial loose assembly photo.
(http://www.pbase.com/kvom/image/126324486/large.jpg)
I need to ream the rod support holes with the +.001 reamer to get smooth sliding fit and adjust a few things for better fit, but once the glands are made the steam chest/valve assembly will be complete.
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Having (at long last) replaced my broken 10-32 tap, I decided to continue on with the piston and piston rod (piston is machined while attached to the rod to ensure concentricity).
The first of two is shown here. Unfortunately I messed up the other rod when threading one end crooked, and that was the last of my 1/4" drill rod supply. >:(
The piston is down to less than .001 greater then the .750 cylinder bore, so finishing will wait until they can be worked together.
Picture shows the attachment to the crosshead.
(http://www.pbase.com/kvom/image/126506641/large.jpg)
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Hi PD's......& a few question for kvom ....
I see the partially finished piston & noted as 0.001"oversize [to the 3/4" cylinder bore]
1. on P72 of Side 5 we see the piston listed as 3/4"OD
2. having read the text I did not pick up the final piston OD to cylinder ID tolerancing
3. do you lap the brass piston [secured on the piston rod & held in the tailstock] to the cast iron cylinder when supported in the headstock chuck?
4. is any rotational speed involved or just longitudinal movement involved?
5. will you use Brasso only as the lapping medium?
6. will you attempt to attain the old adage of say 0.001" per inch on piston to bore clearance?
Keep up the brillant work :bravo & keep us posted with :kewlpics as you progress ....Derek :beer
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The article specifies a moderate sliding fit. My intent will be to use some teflon packing in the piston groove unless someone advises a better solution. In any case the piston is easy to remake if something doesn't work.
In past engines I used toothpaste as a lapping compound, but those were for much smaller bores. I machined the bores with a good quality 3/4" reamer, so the current finish is quite good. I would normally try to get a tight sliding fit by using scotchbrite on the piston mounting in the lathe.
At some point I need to drill the gland and gland screw and gland so that the hole is centered in the bore. My plan is as follows:
1: Mount cylinder on the lathe with 4 jaw chuck so that the bore is centered
2: Screw gland to cylinder face
3: Tap gland to match gland nut, screw in nut
4: drill hole for piston rod
Once I have this done the cylinder will positioned for lapping.
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Yesterday I finally got around to remaking the inner frame piece that I had messed up a few months ago. This long post shows the improved CNC fixture setup I came up with to result in a good part. Previously I tried holding the part to the fixture block with 2-sided carpet tape, clamps, and bolts. This time I am using a holding tab feature to hold the outline cut attached to the surrounding metal. The first step was to secure the aluminum fixture plate in the pair of milling vises using soft jaws:
(http://www.pbase.com/kvom/image/126590088/large.jpg)
The soft jaws are a bit too tall above the hard jaws and have a tendency to bend outward under hard clamping. I decided to level it with the 1.25" endmill skimming a few thou.
The material for the frame and the fixture plate had been previously drilled, so I bolted the work onto the fixture using 4 .25" bolts, without removing the fixture from the vise.
(http://www.pbase.com/kvom/image/126590089/large.jpg)
Having set the X and Y axis zero, a final check to ensure that all is well using the prior bad part.
(http://www.pbase.com/kvom/image/126590090/large.jpg)
The first milling step is this pocket .25" deep, which covers all of the thin part of the frame except the curved postion under the hornblock. I used a .682" 2 flute endmill for this operation in two passes.
(http://www.pbase.com/kvom/image/126590092/large.jpg)
Next the hornblock profile was cut with a .437" endmill, the same that will be used to mill the final outline. Using this endmill here ensures that the rest of the frame profile will blend smoothly with the hornblock. Once this is done, all the numerous holes in the frame were drilled.
(http://www.pbase.com/kvom/image/126590094/large.jpg)
Now the through hole for the cylinder was roughed with a .25" endmill.
(http://www.pbase.com/kvom/image/126590096/large.jpg)
And then a finish pass with a 1/16" endmill:
(http://www.pbase.com/kvom/image/126590097/large.jpg)
Next the 1" hole iwas milled;
(http://www.pbase.com/kvom/image/126590098/large.jpg)
And the outline completes the CNC milling.
(http://www.pbase.com/kvom/image/126590099/large.jpg)
I used a small endmill on the manual mill to cut through the 3 tabs along the top and free the frame from the surroundings material. Turned out the bottom tabs weren't needed:
(http://www.pbase.com/kvom/image/126590100/large.jpg)
Some milling, filing, and deburring completed the frame:
(http://www.pbase.com/kvom/image/126597754/large.jpg)
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An aweful lot of wasted material making that part Kvom..... Couldn't the hornblock be made as a seperate item and bolted to the main frame?
Regards
Eddy
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An aweful lot of wasted material making that part Kvom..... Couldn't the hornblock be made as a seperate item and bolted to the main frame?
Regards
Eddy
That's the way ET made it using steel, with rivets and solder to hold the blocks. However, this method seems to offer better accuracy in lining up the crank bearings later on. This is one of four frames with the same configuration.
I should also add that I got the material for all the frames for free. ;D
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Latest progress was the staybolts and weigh shaft to connect the 4 frame plates together.
(http://www.pbase.com/kvom/image/126707665/large.jpg)
The next pieces I have in mind are the mounting brackets for the feet and the crank bearings.
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Finished the mounting plates for the rear of the inner frames. These took quite a bit longer than I expected.
(http://www.pbase.com/kvom/image/126730296/large.jpg)
For the front I need 4 longer ones.
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Once you see the frames assembled it starts to give an idea of just how BIG this engine is!!
Regards
Eddy
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Made another pair of feet this evening. Still surprising how much time these simple parts take.
(http://www.pbase.com/kvom/image/126765047/large.jpg)
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Some small progress on the engine the past few days.
Made the front feet for the inner frames; no pics for these, but similar to the others.
The next goal is to make the bearings for the crankshaft. I decided to make these as 1 piece and fit the crank to them before mounting to the frames. This is possible as there are separate crankshafts for each cylinder. These will be milled from some 1" round brass bar. I tried the first via CNC milling yielding a .6"x.8"x1" blank. Afterwards I thought up a better/quicker way that I'll document in a later post. The first step is facing the end of the bar on the lathe via a 1" collet, then mounting the bar and collet in a square collet block.
(http://www.pbase.com/kvom/image/126854090/large.jpg)
The CNC mill then carves out a .8x.6 profile 1" deep.
(http://www.pbase.com/kvom/image/126854093/large.jpg)
I then "whittled" out slots on the side and bottom to fit one of the frame hornblocks using the Bridgeport. I screwed up and made the side slots too wide, so this will be scrapped. Once the block will slide fully onto the hornblock, I measure the amound the top extends beyond the hornblock and then mill it flat.
(http://www.pbase.com/kvom/image/126854095/large.jpg)
The bearings are held in place by a strap across the top of the hornblock. It's necessary to drill and tap two holes for the screwing the strap to the hornblock. Here's the setup in the milling vise:
(http://www.pbase.com/kvom/image/126854097/large.jpg)
I managed to get a second bearing block fitted before leaving the shop, as well as drilling and tapping all 4 hornblocks.
(http://www.pbase.com/kvom/image/126854099/large.jpg)
Next time out I'll try to fit three more bearing blocks and make the retaining straps. Then it's back to the CNC to bore and ream the holes for the crankshafts.
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A bit of progress today. I finished sizing the remaining three bearing blocks to their respective hornblocks, and made one of the retaining straps.
(http://www.pbase.com/kvom/image/126922786/large.jpg)
The center of the straps need to be drilled for an oil cup, but until I know how I'll make those I just center drilled a spot for a marker.
To make the rough bearing blocks from 1" round bar, here's the setup I used:
(http://www.pbase.com/kvom/image/126922783/large.jpg)
With that 1.25" endmill I could easily take .100" DOC, so it took only 6 passes to get the oblong. Then it was off to the bandsaw to cut it off. A smaller mill could still use this approach with smaller endmills and cuts.
I also spent some time tapping the base mounting holes on one of the cylinders. I found that the cast iron tapped quite easily with light finger pressure on the tapping stand, which was a relief.
Before milling and boring the bearings, I need to do an assembly of the frames on each side to see how much room is there initially to fit the crank and conrod, and adjust accordingly. I start out with the length of the outer staybar, and from that subtract the thickness of the hornblocks and the amount the bearings extend. The distance from the inner frame to the center of the crank needs to be pretty close in order for the drive components (piston/rod/crosshead/conrod) to line up. It's not clear how close the tolerances need to be.
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Some nice progress there.
what mill are you using? is it one of the chinease imports?
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Some nice progress there.
what mill are you using? is it one of the chinease imports?
CNC mill is Novakon 200, a Chinese import. Manual mill is a Bridgeport.
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Got in 6 hours or so in the shop doing "little stuff", so not much to show photographically. Also found one big "boo-boo". Might be fixable.
The first job was to drill the cover mounting holes on one side of both cylinders. The other side was done via CNC when milling the profile. For this side I just centered the bore under the Bridgeport quill and used the DRO to locate the holes. Still took a long time to be sure of everything. After tapping all the remaining cylinder holes, I got the rear covers and one front cover to fit after some filing. Any opinions on using those 5-40 set screws as studs? Seems to look OK.
(http://www.pbase.com/kvom/image/126980876/large.jpg)
Notice anything wrong? The front cover needs to go on at a 90-degree angle from what's shown, meaning I'm missing one mounting hole and have an extra. I think I can put a dummy bolt in the extra hole and use the part.
In any case I drilled and tapped the holes in the front cover for mounting the crosshead guides. There was no dimension for locating the holes; I did a finger assembly and discovered that the end of the guides bars need to be flush to the front of the cover, so 5/32" out. With two bars attached, one crosshead slides very smoothly, but the other is a fraction tight at the near end.
(http://www.pbase.com/kvom/image/126980900/medium.jpg)
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Hi PD's........kvom...I think it would be a pity to...... shall we say spoil the :no1b build by showing the internal hex of your 5-40 hollow pointed grub screws......but :thinking...there would be no challange in reversing them & driving them in with a double 5-40 lock nut , then remove the double nuts & your cylinder studs would be depicted as original solid studs...... :clap .....Derek
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Good idea derek. Thy will be done! ;)
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My "plan" now is to use the grub screws as short studs but reverse them so that the hex hole in the end is not seen. By using two nuts as locks I can tighten them into the cylinder and other short blind 5-40 holes. Thanks to Derek for the idea. I have ordered some hex-head bolts from American Model Engineering that will be used to connect the cylinder to steam chest to cover. I also have some 5-40 threaded rod to use in other places as needed. Those model-scale nuts and bolts cost $0.30 each, so the model will have a lot of expense just in nuts and bolts.
This weekend I bit the bullet and redid the inner cylinder covers to orient the mounting holes correctly. I also decided I could use the CNC mill to get accurate centering of the holes for the piston rod. The first order of business was a skim cut on some 1.5" diameter brass rod, yielding a diameter of 1.491". Without removing the rod, face, then turn the inner spigot of the cover to a close fit with the cylinder bore. Then drill a pilot hole and part off. Repeat for the second piece.
(http://www.pbase.com/kvom/image/127073492/large.jpg)
Next use the CNC mill to create a soft jaw pocket to match the diameter. Afterwards the Z-axis of the mill is centered on the pocket and thus the workpiece that's mounted in it. Now I can face the parted end, mill the profile, drill the mounting holes and the hole for the gland screw, and tap the hole for the screw using the 1/2-28 forming tap. Then screw in the gland screw and drill through it. Hopefully everything ends up concentric. I didn't have my .251" reamer handy, so that will be done later.
(http://www.pbase.com/kvom/image/127073495/large.jpg)
The last operation is manually drilling and tapping the holes for the crosshead guides, as shown in an earlier post. With everything assembled for a trial fit:
(http://www.pbase.com/kvom/image/127073501/large.jpg)
Of course, everything didn't go as smoothly as the above sequence would suggest. Biggest issue was that the gland scews would not go into cover more than 1/2 turn. The screws do go into the aluminum nut I made with the same tap, and the tap turns easily in the covers' threads. I tried to set up the lathe to potentially recut the threads a smidge deeper, but couldn't get the screws perfectly straight in the collet chuck. I finally decided to run a small triangular file into the threads while the lathe was turning slowly, and in addition put a slight bevel on the ends. Now I can get about 2 turns of the screw, so I'll just have to put enough packing into the glands.
My list of parts to finish is getting smaller:
Mill and bore crank bearings
One piston rod and piston
Crankshafts and the connector
Conrod pins
Lifting links
Remake one weigh link, plus some lever mechanism to move the weigh shaft
Eccentric discs
Remake one staybar
Some sort of base
Air plumbing to steam chest inlets
Got an order into Enco for materials plus some roll pins.
Then lots of filing, adjusting, cussing, and remaking anything that proved inadequate. One month to go before my 2-month trip, so it will be close.
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Today's mini-project was making the conrod pins that connect the rod end to the crosshead. I chucked some 3/8" drill rod in the collet chuck, faced it, and turned to 1.4" diameter for a length of 1/2". The conrod ends have been reamed to .251, so I took off a couple of thou at a time until I had a nice sliding fit on the rod end:
(http://www.pbase.com/kvom/image/127138383/large.jpg)
Next, center drilled, drilled and tapped the end 5-40 for to depth of 3/8".
(http://www.pbase.com/kvom/image/127138384/large.jpg)
Next parted off leaving a "head" 1/16" thick. After making two, I reversed the pins in a 1/4" collet to smooth off the partoff tit.
Not having done so previously, I needed to drill and ream the center hole in the outside crosshead cheaks. With a 5-40 grubscrew stud screwed into the end of the pin, the crosshead and conrod assembly looks like this:
(http://www.pbase.com/kvom/image/127138386/large.jpg)
Eventually the SHCSs will be replaced with studs & nuts too.
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Today I started on the cranks, and did not have a good day. Here's the photo evidence:
(http://www.pbase.com/kvom/image/127225399/large.jpg)
The shafts are all 3/8" drill rod. The webs are 3/16" thick and need to be separated by 1/2". After drilling and reaming the webs .001" oversize, my process was to hold the webs and the crank pin together in a vise with a .500" gauge block clamped between the webs for spacing. I would then fix the crank pin to the webs with 1/16" roll pins.
I had two errors with this plan. First, I had made the crank pin slightly too long, so that when I clamped the vise the webs and the gauge block were a bit loose. I ended up with the webs about .04" too close together. The second error was where I drilled for the roll pins, which need to be in the ends of the web rather than the side. With the pins where they are the webs can move slightly side to side around the roll pins.
I also discovered that the crankshaft pieces I had cut will be hard to get straight, as the oversize hole and thin web make it possible to move slightly.
So my rework plan is as follows:
1) Make the crank pin slightly less wide than the width of the crank, allowing use of the gauge block to set the web separation.
2) Make the crankshaft one piece and use for aligning the webs.
3) Secure both the crank pin and crank shaft with loctite and let set
4) Drill and insert roll pins and the ends of the webs after the loctite dries.
5) Machine out the center section of the crankshaft.
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Hi PD's.......& I understand kvom a little of the inherent inaccuracies when using C-Lok pins
1. Never use a hammer to tap home a C-Lok pin...they are RC 45+ so will act as a broaching tool as they guide their own way toward miss alignment
2. Whilst the SPS Technologies [Unbrako Group] now Indian owned...do not reference.......the geometry of the chamfer on the C-Lok pin ends as it is not conducive to correct alignment even when gently pressing the said pins home & such pressing of an off axis C-Lok pin will crack the Loctite bond...... :oops
3. Could I suggest miniature BS Standard taper pins inserted to taper reamed holes [between components] would offer unsurpassed accuracy :trophy ......
4. After some trial assembly & confirmation of ZERO [0.000"] miss alignment you can gently press the taper pins out & reinstall with Loctite Super Stud Lock........ the taper pins will last last a million years +.....so :06 .....Derek
kvom will know.....but here is a link for other members http://shopswarf.orconhosting.net.nz/taperpin.html
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I started to remake one of the cranks today, this time using some 12L14 for the webs and shouldering the pin:
(http://www.pbase.com/kvom/image/127285331/large.jpg)
I have put some loctite on the pin ends to set up until tomorrow. The total width measured from the outside of the webs is .04" oversize. This is "semi" on purpose as my rod ends are .03" too wide. I think I can safely take off .02 from the outer side of each web if needed.
(http://www.pbase.com/kvom/image/127285334/large.jpg)
I won't fix the crankshafts until the engine is ready for a trial fit.
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The first task today was to drill and pin the crank webs to the pin. This went well. I started the roll pins by tapping with a hammer, but then pressed them in fully with the vise jaws. One of the conrods was test fitted:
(http://www.pbase.com/kvom/image/127346290/large.jpg)
Next I undertook drilling the first pair of bearings.
Here's the setup in the milling vise, with the inner frame being clamped by the hornblocks.
(http://www.pbase.com/kvom/image/127346286/large.jpg)
There is a couple of thousands play between the bearing and the hronblock, so I used a shim from a soda can to clamp down the bearing with the retainer plate. Note that I obtained the center from measuring the inner edge of the hornblock.
Then drilled and reamed:
(http://www.pbase.com/kvom/image/127346287/large.jpg)
Then the the same with the outer frame, although clamping in the vise was trickier because of the curve leading into the hornblock. Still it seems to be all good as the drill rod passed through the assembled frames turns pretty easily:
(http://www.pbase.com/kvom/image/127346289/large.jpg)
Before leaving the shop I set some drill rod for the crankshaft into the webs with loctite; next time, after it cures, I'll pin it to the webs. Also need to make the other crank and drill the other two bearings.
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Spent a good part of the afternoon in the shop. The first task was to drill and pin the crankshaft to the crank webs, then mill out the portion of the shaft between the webs. Then I finished drilling the bearings for the other two frames, allowing a test setup of the four frames. Here's the result, including the crank:
(http://www.pbase.com/kvom/image/127390763/large.jpg)
The good news is that with the two center staybolts in place, the 3/8" length of drill rod turns smoothly while passed through all four bearings. \
The bad news is that the holes for the outer staybolts in the outer frames seem to be ~.04" higher than in the inner frames. I checked my CAD drawings and they are correct, so I have no idea how they became displaced. I can still install the outer staybolts, but that causes the frames to flex slightly and jam the alignment rod. I will enlarge the holes in the inner frames slightly to correct this. As shown in the photo, the height of the staybolts varies on .004" from one end to the other, so the engine is quite level side to side.
Now that I have a crank and can connect the frames for testing fits, I proceeded to mount one of the cylinders to get an idea of how much the bearing sides will need to be trimmed. To do this, I needed to finish fitting the previously turned piston to that cylinder.
That's when I discovered that the conrod threads were crooked on one end. I had cut the threads with a die on the lathe, but that wasn't good enough. So I proceeded to make two new piston rods with the 10-32 threads on each end single-pointed to ensure they are concentric. Once they were done, I needed to remake the piston, which needs to be turned "in situ" on the piston rod. So this meant facing/turning/drilling/tapping some 1" brass rod, then parting off and screwing onto the piston rod. Then the final diameter is turned with the piston rod chucked in a collet.
(http://www.pbase.com/kvom/image/127402054/large.jpg)
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I'm now on a 2-month trip, so any engine progress will be deferred until November at the earliest.
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I got back from Nepal a week ago, but a combination of jetlag and a chest cold have kept me out of the shop until this weekend. Today's goal was to rough out the two lifting links, pieces that connect the lift arms to the expansion links. These are somewhat "delicate" as ET says, so it took me some thought as to how to make them.
Material is 1/4" diameter drill rod. First a length is chucked in the lathe collet, and i faced the end and center drilled it.
(http://www.pbase.com/kvom/image/130137587/medium.jpg)
The rod and collet were then transferred to a square collet block and secured in the mill vise. A vise stop was used to ensure repeatability. A 1/4" carbide endmill then milled a flat .055" deep 1/8" from the end of the rod. Leaving the spindle locked, I turned the block over, positioned against the vise stop, and milled a matching flat on the opposite side of the rod. Next a 1/8" hole is drilled through the rod.centered on the flat.
Next the collet block is moved to the surface plate, and the drill rod is pulled out ~ 2". The height gauge is used to set the milled flat parallel to the plate.
(http://www.pbase.com/kvom/image/130137588/medium.jpg)
Back to the mill vise. I used the 1/8" drill bit in the existing hole to zero the DRO, then moved the X-axis 1.625" to establish the location of the flat/hole on the other end.
(http://www.pbase.com/kvom/image/130137589/medium.jpg)
The collet and rod are then placed back on the lathe to turn down the shaft between the flats. The non-chucked end is supported by a live center. First I used a parting tool to turn down the right end of the shaft to provide space for a turning tool.
(http://www.pbase.com/kvom/image/130137590/medium.jpg)
Then the rest of the shaft was turned.
(http://www.pbase.com/kvom/image/130137591/medium.jpg)
After some polishing of the shaft with emery cloth and scotchbrite, I parted off the link. After the first one, it took only about 15 minutes to make the second.
(http://www.pbase.com/kvom/image/130137592/medium.jpg)
In my next shop session I will grind off the center-drilled portion and do some cleanup filing on the ends.
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A bit more progress this afternoon, although nothing picture-worthy. The first job was to mill the sides of the main bearings to plan, and test fit the crank and outer staybolt for spacing between the frame. By measurement it looks good, but the true test will be when the entire drivetrain is in place.
After that, I found a piece of 12L14 in the material drawer and used that to mill the webs for the second crank. Afterwards, I used 3/8" drill rod as before for the crankshaft and pin, setting them in place with loctite and using a .500 gauge block to set the spacing between the webs. The assembly will cure overnight, and then will be fastened permanently with roll pins. Essentially the same construction as the first crank.
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Looking at the cylinders I must ask why are they so big in relation to the piston diameter? There is a huge amount of metal in there for such small pistons.
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The plans and the subsequent castings have the body of the cylinders necked down in the center, making the cylinder less bulky looking. I machined the trial aluminum cylinder that way, but decided that I like this look better.