ET Westbury Side Paddle Engine

[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-eneded 1/6" 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

 

[kustomkb]

very nice work on your parts kvom. They look great!

If I may offer an alternative to clamping in the vise;

A fixture plate can be drawn up in your CAD/CAM program with spaced out tapped holes.

then bore a hole off in a corner, or centre, to clock in with your dial as your XY Zero.

now you part can be moved around in your computer to get it close to your preexisting holes for clamping. Also you can clearance drill through to retain a slug knowing there is a hole allready tapped underneath.

When you add new holes like removeable dowel pins, update your model for the next job.

parts can be milled a half a profile at a time by flipping the clamps around, without worrying about distortion.

To minimize end mill breakage, I use a general rule of 10% diameter step down per pass or when ramping down.

sorry for the lecture,

Have fun!

 

[kvom]

Kevin,

A fixture plate like that is certainly useful, and I ought to make one. Good photos. I did use something similar, though cruder, for the frame plates. I needed to use the softjaws for these parts since the sides are not flat.

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.

 

[SAM in LA]

KVOM,

Great looking parts.

You may want to reconsider adding the radius rather than leaving that corner square.

That square corner between the rod and clevis will be a weak point.

Just my unsolicited $0.02.

Regards,

SAM

 

[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.

 

[kvom]

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.

 

[don-tucker]

Do you really want to go away for all that time Kvom,I want to see this engine completed now I am back home from Rhodes.It has the precise look of machined parts you can only get from a CNC.Excellent.
Don

 

[kvom]

Rhodes? Hope they aren't rioting there.

I'll also be gone the entire months of September and October, so if I get this done by the end of the year I'll be happy. I still have to tap all 28 holes in each of the cylinders, and not having tapped cast iron before I would hate to break a tap in one of them. I'm also not sure what kind of main bearings I want to use. I'm thinking about using some needle bearings rather than the split bushings called for in the plans.

Nonetheless, the parts box is pleasantly full after only a couple of months sporadic work.

 

[zeeprogrammer]

I'll also be gone the entire months of September and October, so if I get this done by the end of the year I'll be happy.

Not acceptable. ;D I can't sit on the edge of my seat that long.

 

[don-tucker]

Rhodes? Hope they aren't rioting there.

I'll also be gone the entire months of September and October, so if I get this done by the end of the year I'll be happy. I still have to tap all 28 holes in each of the cylinders, and not having tapped cast iron before I would hate to break a tap in one of them. I'm also not sure what kind of main bearings I want to use. I'm thinking about using some needle bearings rather than the split bushings called for in the plans.

Nonetheless, the parts box is pleasantly full after only a couple of months sporadic work.

Nope no trouble in Rhodes,lovely people,Please please don't use needle bearings for the mains,I wouldn't be able to face my brother if I told him that,he would say it would be like putting PVC windows in an Edwardian mansion ;D .
Cast iron is good to tap with a bit of patience and clearing the hole with a jet of air now and then ( like to see you CNC that job .
Don

 

[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 abd 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.

 

[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.

 

[don-tucker]

looking good Kvom,glad to see you back at work.
Don

 

[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.

 

[ariz]

great work so far Kirk :bow:

keep it up

 

[kvom]

Don & Ariz, thanks for looking in.

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:

 

[don-tucker]

You are red hot with that CNC,you must forgive my little cracks and jibes,I would love to be able to do that.
Don

 

[kvom]

Thanks for dropping in, Don.

Latest progress was the staybolts and weigh shaft to connect the 4 frame plates together.

The next pieces I have in mind are the mounting brackets for the feet and the crank bearings.

 

[kvom]

Finished the mounting plates for the rear of the inner frames. These took quite a bit longer than I expected.

For the front I need 4 longer ones.