ET Westbury Side Paddle Engine

[Eddy Matthews]

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

[granath]

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

[kvom]

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.



The holes are drilled with a #30 bit to clear the 5-40 studs that will connect the cylinders, steam chest, and cover.

[kvom]

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:



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:



Next clearance holes for 2-56 screws were drilled manually.



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.

[kvom]

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:



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.



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.



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. 

[steamboatmodel]

Why did you not do the drilling of the holes with the CNC ?
Regards,
Gerald.

[kvom]

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.



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.

[kvom]

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.

[kvom]

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.

[kno3]

Nice! Please keep us posted.

[kvom]

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.



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.

[kvom]

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. 



I still have drilling and tapping to do on both, and the first one is a bit thicker than in the drawing.

[granath]

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

[kvom]

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:





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").





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.



These little parts took the best part of two afternoons in the shop, not counting CAD/CAM time.

[granath]

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!