First Engine Elmer's #29

[RCGUY]

I finished milling the body of the cylinder. The last step is to round the back of the cylinder. I just purchased a 4" round table to do that job but I will have to wait a week for a #2 MT insert to mount my chuck on the table.

What size end mill would work the best for rounding the back side? I used a 1/2" to mill down the sides.

Ed

 

[Ogaryd]

Hi Ed,

Your doing a beautiful job, keep up the good work. :bow:

Gary

 

[arnoldb]

The cylinder looks great so far Ed Thm:

The 1/2" end mill should work just fine for rounding over - just do it with light cuts.

Kind regards, Arnold

 

[mzetati]

I finished milling the body of the cylinder. The last step is to round the back of the cylinder. I just purchased a 4" round table to do that job but I will have to wait a week for a #2 MT insert to mount my chuck on the table.

Ed,

You could make a MT2 mandrel to mount the cylinder on the table. A plate with a boss would do, too.

Marcello

 

[b.lindsey]

Ed, hope you had a nice vacation!! Glad to see you back working on the #29 again too

Bill

 

[RCGUY]

Thanks for the kind words and support. I should have more progress in a week or so.

Ed

 

[RCGUY]

UPS delivered my new rotary table and a MT2 arbor with a 1/2"-20 TPI end to mount my 4 jaw chuck. I mounted the cylinder and started cutting with a 1/2" 4 flute end mill. I finally ended up using a 1/4" 2 flute. The cut was not very smooth, I think it was my aluminum arbor causing the problem. Next time I will use an arbor like Marcello suggested in a previous post. I was able to use some 400 and 600 grit W/D sand paper to smooth the rounded back.

Ed

I also did some buffing on the cylinder using Black, Red and White buffing compound.

 

[RCGUY]

I milled down a piece of brass to 15/16 X 15/16 and spotted the 6 holes then went back and drilled out the 6 mounting holes with a #43 drill. I originally planned on getting the cross-head guide, lower and upper head out of this piece of brass. So I drilled the 6 mounting holes deep enough for all 3 pieces. Well I messed up and had the bolt circle off center. So I flipped it over to the other side and was able to get the cross-head guide and lower head only.

Should I use a gasket between the heads and cylinder or is lapping OK?

Ed

First I made the Cross-Head Guide

After cutting the Guide off I faced the brass and made the lower head.

While I had the lower head on the lathe I used some 800 grit lapping compound to hold the cylinder to it and seat it.

 

[Shopguy]

Looking good.
You've really got the polishing down pat.
regards
Ernie J

 

[Swift752]

She sure is pretty! Where do I get the plans? Thanks. Swift752

 

[RCGUY]

I made the piston out of aluminum which I understand is a bad choice. But this engine will only run on air and spend most of it's life on display. My choice for the piston rod is 3/32 drill rod that was threaded with a 3-48 die. I lapped the piston to the cylinder with clover silicon carbide (800 grit) compound. The piston drops into the cylinder nice and smooth. When I cover the intake and exhaust ports the piston drops down the cylinder slowly all the way to the bottom.

Ed

 

[RCGUY]

swift752,

Here are the plans for Elmer's # 29 it is a PDF file.

http://www.john-tom.com/ElmersEngines/29_mineEngine.pdf

Ed

 

[RCGUY]

UPPER CYLINDER HEAD

I started out with a block of brass that is milled to 15/16 square. Then drilled the bolt circle with a #43 drill.

I then centered the block in the 4 jaw chuck.

When I cut the profile of the upper side I was careful to size the upper boss to 5/16th.

Next I installed the head in the 3 jaw chuck and cut the profile on the under side.

Next I used a piece of scrap aluminum to hold the upper head, I drilled a hole with a 5/16 end mill. With the upper head snug in the 5/16 hole I know the part will be centered to drill the hole for the piston rod.

Next I installed the back stop and removed the aluminum jig. I removed the head and installed it on the under side of the aluminum. After putting it back into position I drilled the larger hole and tapped it for 3/16-40.

Looking back I should have centered the 5/16 hole in the aluminum from front to back. I had a small problem installing the parallel bar on the back when I installed the head on the bottom side.

Ed

 

[RCGUY]

The packing nut for the cylinder has caused me more problems the any other piece so far. When I drilled the hole it was always off center a little. I finally mounted it in the 4 jaw chuck and centered it, cut it down and threaded it. Then moved it to the mill and used a 3/32 2F end mill then followed it with a #41 drill.

What is the best material to use for packing around the piston rod?

Ed

 

[Inky Engines]

Ed

I've used a 1/16" graphite yarn for packing on Elmer's Grasshopper, Mill and Factory engines, but its fiddly getting it under the nut, and imho it achieves little or nothing. On this scale any advantage gained in terms of air containment is lost in extra friction.

I'm really enjoying your build log.

Kind regards

Geoff at Inky Engines

 

[rleete]

Cut off about 2 inches of teflon thread tape. Using your fingers, roll it up into a string. Wrap that around the shaft, and cut off the extra.

 

[RCGUY]

Thanks for the reply and advice.

I visited the local hardware store and found the graphite yarn and some solid teflon rope. Both seemed rather large, so I used 2 strips of teflon tape then twisted it to form a rope. This option seems to work, time will tell.

Ed

 

[RCGUY]

Found some time to work on the engine. I milled the Crosshead Guides and made some filing buttons. The guides still need to be cleaned up some. It felt good to get back in the shop and work on the engine.

Ed

 

[rleete]

Very nice work.

 

[110samec]

Why is aluminium a bad choice for pistons? I always thought it was OK to use