Elmer's Oscillating Cylinder Engine #42

[EricB]

I was using a pin vise for the small holes. Now I see I need to make Joe Pie's small tapping tools and one of those spring loaded guides, and also not try to go too fast.

Eric

[derekwarner]

Eric....

Apologies if I have missed it, but will you not need a steam sealing n O-ring groove & O-ring on each side of each fixed bearing block?....

Derek

[EricB]

Hi Derek,

This design has the seal in the steam connection in the area shown. Elmer's directions say use "graphited asbestos packing." I think I'll use something else. The exhaust side just stays open.

Eric

[RReid]

Elmer's directions say use "graphited asbestos packing." I think I'll use something else.

I have used Glide brand dental floss as packing with success in my live steam locomotive. This is made from an expanded form of Teflon (ePTFE) and is somewhat similar to miniature Teflon tape.

My two previous Elmer's engines run on compressed air without any packing or piston rings, relying only on a thin film of oil for sealing.

[EricB]

I guess I'll have to get some of that glide floss and give it a try. I use them pre-strung flossers.

Today I "finished" the sub-base, which consisted of finishing the top surface, squaring the sides, and drilling holes.

The problem I had to solve was how to hold it to finish the surface. I thought about making some low profile side clamps and fix it to the table but I didn't really like that idea. My solution was to CA glue it to another block held in the vise. After I surfaced the block with the fly cutter, I covered it with a layer of painters tape and rubbed that down. I then covered the bottom surface of my part with tape and rubbed it down the same way. After that I spread a layer of CA glue on the block in the vise, placed my part on top using a parallel to align the back edge with the front face of the mill column (Sherline). I've found using the front face of the column is a convienient way to align things with the table. Anyway, after the part was in place I put some weight on it and let the glue cure for a few minutes. It held incredibly well. I was able to flycut the top and mill the sides square without any problems. It came loose with a little pressure applied between the top of the vise and the bottom edge of the part.

To drill the holes I cut some spacers from 1/2" bar, taped over the top surface I had just finished and clamped it top down onto the mill table. Again I used a parallel against the mill column for alignment. After that it was spot drill, twist drill, and countersink for the six holes that hold the base and frame together. The three holes for mounting the engine to a plinth were drilled last.

I think I drilled the holes through the base a day or two after the tapping work on the frame but I didn't record any of that.

Still needed is the bearing bracket for the outboard end of the crankshaft to complete the base. That should be a straight forward task. It just needs to be the same height as the inboard bearing block.

One more puzzle I haven't worked out yet is the base should have a 5.5 degree angle on all the sides to simulate the draft of a cast part.

Eric

[crueby]

Looking great!




Several ways to do that angle on the edges. One would be to clamp it to the table, like you just did, with a piece of thin stock along the edge of the table to tilt it, and run an end mill down the side of the part. A little trigonometry will tell the thickness of the shim to use. Lots of other ways, fun to work out which is best for what tools you have.


 

[cnr6400]

As Chris says, many ways to do the angle on the base. For those with a few dollars left in the tool budget (no idea who has that), and who are lazy in setups (like me) you can buy endmills with a taper angle ground on. The example at the link below is 5 degrees. Suppliers have many angles, but usually in increments of a full degree. With these tapered mills, you make a normal endmill cut and the surface is cut at the taper angle. Very handy for mould and pattern making. Hope this info helps. 

https://www.mcmaster.com/8936A37/

[crueby]

As Chris says, many ways to do the angle on the base. For those with a few dollars left in the tool budget (no idea who has that), and who are lazy in setups (like me) you can buy endmills with a taper angle ground on. The example at the link below is 5 degrees. Suppliers have many angles, but usually in increments of a full degree. With these tapered mills, you make a normal endmill cut and the surface is cut at the taper angle. Very handy for mould and pattern making. Hope this info helps. 

https://www.mcmaster.com/8936A37/

Never seen those before - nice!

[Flyboy Jim]

Might be a good time to add a Tilting Angle Table to your tooling: https://www.sherline.com/product/3750-tilting-angle-table/ I use mine a lot.

Nice looking engine.

Jim

[RReid]

Might be a good time to add a Tilting Angle Table to your tooling:

That's one of the handy Sherline accessories I just got. They were part of the Sale of the Month, last month. Sorry Eric.

The trig and shim method is potentially very precise, if done carefully. For the cosmetic job at hand you could get away with less careful but still with good results.

[RReid]

Your use of CA and tape for work holding is clever. I've used CA for holding blanks in wood turning, but never in metal work. I'll keep that idea in mind! I have used carpet tape on a mill table for fly cutting and light grooving of plastic and graphite. Worked well for that, but cleaning off the goo was a pain, and I wouldn't trust it for heavier work.

[Kim]

I've used this double-sided tape quite a bit to hold things together while working them - both metal and wood. And it works quite well.  I've never had a problem with it.  It holds tight, is very think and doesn't leave a sticky residue when you peel it off.  Probably won't hold up to well at high temp, but as I said, I've done some milling work while holding with this sticky tape and haven't had a problem.

https://www.amazon.com/Spectape-ST501-Double-Adhesive-Length/dp/B003ASGL02/ref=sr_1_1?dchild=1&keywords=Spectape&qid=1621355148&sr=8-1

Kim

[EricB]

I can't take credit for the glue setup. I found it here: <a href="https://www.youtube.com/watch?v=r6DCvtcU8_M" target="_blank">http://www.youtube.com/watch?v=r6DCvtcU8_M</a>
They do a lot more cleaning in the video to make sure the glue sticks, but as easily as it holds my oily fingers together I figured that was overkill.

Double sided tape would probably work just as good, but how would you know for sure it's making good contact with the parts?

I have the tilting angle table. I picked it up during one of their monthly specials back in early 2020. Set to a low angle it limits my Y travel so I can't get to the entire edge of the part. Set to a high angle the part gets in the way. It isn't designed to mount with angle parallel to the mill's X axis, which would solve the problem. I'd need to drill some more mounting holes in it. Still thinking about it.

Eric

[crueby]

Eric, try turning the vise around on the tilt table, so the fixed jaw is back by the other end of the tilting plate, that gives more room to the sides of the vise. I don't remember if I had to drill more holes in the tilting plate to do that or not, was long ago and not very far away...!

[EricB]

Hi Chris,
My experience with the tilt table is that the farther the work is from the angle center, the more the table flexes.

I think I'm going to try it with the spindle horizontal. With the fixed vise jaw close to the angle center both the tilt table and the part clear the column, the mill cutter can reach the part, and I can get the full Y travel. The short sides will be fun. I'll need to practice with this a bit first.

Eric