ET Westbury Side Paddle Engine

[kvom]

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.



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.



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.



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

[kvom]

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.



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.



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. 





Finally, with the rod held in the pocket I drilled the 1/8" hole where it will connect to the expansion link.



Here's the stopping point for the night.



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

[kvom]

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:





With the slots done, it was back to use the pocket in the vise jaws to face off the other side of the rod:



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.



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.

[kvom]

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.



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.



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.

[kvom]

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.



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.



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.

[derekwarner_decoy]

  ....a 6 jaw self centering lathe chuck?............shows my machining days were many years ago ....    - Derek

[kvom]

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.   

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.



So I came up with this setup on the mill to remove the radii:



With the rod now mountable a loose assembly of partial valve components looks like this:



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.   

[kvom]

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.



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.

[PeeWee]

Looks like shes coming along nicely.  great looking work

[kvom]

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.



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.

[kvom]

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.

[derekwarner_decoy]

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 & keep us posted with  as you progress ....Derek

 

[kvom]

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.

[kvom]

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:



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.



Having set the X and Y axis zero, a final check to ensure that all is well using the prior bad part.



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.



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.



Now the through hole for the cylinder was roughed with a .25" endmill.



And then a finish pass with a 1/16" endmill:



Next the 1" hole iwas milled;



And the outline completes the CNC milling.



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:



Some milling, filing, and deburring completed the frame:

[Eddy Matthews]

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