A "Poppin" for Christmas

[gabby]

still here JL still here

 

[AussieJimG]

Don't give up JLeatherman, I can't offer technical advice but I am sure that if you persist, it will run. Others have got their engines to run and so will you.

If all else fails, ask for advice on Model Engine Maker and hope that Bogstandard will reply.

Jim

 

[ninefinger]

At the moment I'm running my burner on white gas (Coleman fuel) which is blackening the cylinder had a bit but has not caused any residue inside the engine. I'll dump it out and change to pure alcohol as soon as I find some.

The fuel and flame can make the difference. Ask me how I know! I originally tried some 70% isopropyl alcohol that I had and my poppin wouldn't quite run - almost but not quite. I put a BIG (comparatively speaking) flame on it from a propane torch (turned all the way to almost off) and it started running very happily so I sourced some 99% technical grade alcohol and now it runs very nicely.

Keep it up - it will run someday soon.

Mike

 

[JLeatherman]

Mike, I tried a propane flame once from my mini soldering torch. It immediately warped the .002" valve. I'll try a different fuel once I get the head cleaned back up and the engine on a riser. Hopefully I'll have some time this weekend to play around with it.

 

[gabby]

just a small observation, is the bearing that runs on the cam much bigger in diameter than the roller on the drawing ? that may have some "bearing" on the no run problem as the cam should be altered to compensate for the extra wide opening and closing, what I am trying to say is, with the cam as per the drawing and you time it from the opening point, then the closing point would be delayed and if it was timed from the closing point then the opening point would be advanced.
have you tried a bearing of the same size as the drawing roller ?.
just a thought.
Cheers

 

[bob shutt]

Hi J
First off nice looking engine. What I ran into on mine was the seal from the shim stock. I made a steel disc .325 dia by .040 thick with a .060 stem. I drilled the shim stock and peened over the stem. the suction will hold it over the opening better. Another deisign is to make another plate and space it out over the head the thickness on the shim stock. Try the disc and if that does not work I can give you more information on the plate. I also use Gas line Antifreeze (Methyl alcohol) for fuel with a PM research burner.
Bob

 

[JLeatherman]

Bob, that's a great idea. I'm working on a spacer for the engine so I can get the burner closer, and I've picked up some 99.8% pure isopropanol. Next step, failing that, is a new valve arrangement.

Up next "A poppin for valentines day"

 

[GT53]

Hi, looks like a very well made engine and I'm sure you will get it running with a little
experimentation. I also had problems getting mine going but finally ended up where it
will run until the fuel runs out.

Here are a few additional ideas which may help you.

I found the cam timing needed to be quite precise, 5 degrees either side of the sweet
spot and the engine would not run. Start at the recommneded timing and then move
5 deg at a time until you find the best spot.

My engine takes a couple of minutes to warm up before it will run. Until then, the hot
air drawn in on the down stroke is cooled too much by the cylinder and head before
the valve closes. I used cast iron for the piston and cylinder and steel for the head,
wonder if your aluminium construction is conducting even more heat away.

The cooling of the hot air in the cylinder once the valve closes will result in the
cylinder pressure being less than atmospheric. This will remain lower for most of the
piston travel towards TDC and consequently the valve will remain tight against the
cylinder head. Close to TDC the pressure will equalize and the final travel of the
piston will cause the pressure to be above atmospheric and the valve to 'pop' away
from the head. The lower the initial temperature of the trapped air in the cylinder the
earlier the valve will pop away from the head on the up stroke. You noted that air
wheezed from the valve on the upstroke when you retarded the timing. It may well
be that the timing was OK but the air trapped in the cylinder was not initially hot
enough to keep the valve closed during the up stroke.

I eventually settled on a 0.004" valve blade cut from a feeler gauge. I found a 0.002"
valve warped very quickly. An 0.003" valve warped in use but returned to flat when
cooled. Although a 0.006" valve worked fine for a while it eventually fractured. Even
now the valve is not perfectly flat but the low pressure in the cylinder is enough for
the blade to flex and seal tight.

I use ethanol for the fuel with a Zippo wick. The wick is teased open into a large
head to produce a large, wide flame. The top of the flame reaches just past the top
of the valve so that on the downstroke, the tip of the flame is drawn in over the top
of the valve and into the cylinder.


I'm sure you are very close. Keep at it and you will get there. I will keep watching
this post for the good news.

Gordon.

 

[JLeatherman]

Just a quick update. Here's a shot of the engine, burner, and base (unfinished):

Still not running. The burner is filled with 99.8% Isopropanol now, still nothing. I'll spend a few more nights playing with the timing before I tear it apart for cleaning and make a new valve.

 

[JLeatherman]

It runs!!!! Sorry, no video (stupid dog chewed the "record" button off the camera) but I assure you it runs beautifully. I promise to get a fideo up once I've finished the base and made the cap for the burner and loctited all the screws in place.

What was wrong, you ask? Piston-to-cylinder fitment. I made the mistake of assuming the round/smooth graphite rod I purchased was actually round. I made the cylinder until it was a good fit to the rod as-shipped and called it a day. Turns out the rod was .0010"-.0015" out of round. I pulled apart my engine and found three or four contact points on the piston, and I noticed you could see daylight around it at places. Unfortunately I needed to make a new cylinder too, once I turned the material round. I made the cylinder from steel this time, just to increase my chances that I was going to have a runner. I think an aluminum cylinder would still work fine with the graphite piston if the fitment was done properly. My new graphite piston/steel cylinder has a little drag when cold, but fire off after just a few seconds of warmup. This is still the same head, valve, and timing I had before.

I'm just glad I can now move onto a Farm Boy engine with a clear conscience

 

[rleete]

Congratulations!

 

[chucketn]

Congrats JLeatherman! I'm rebuilding my Poppin that I couldn't get running now. I hope I'm as sucessfull!

Chuck

 

[JLeatherman]

Ok, I coaxed my phone to take a video. The sound is a bit off and stops partway through, but I have proof that it runs. This was a room-temp startup. One flick was all it took. Initially the piston was snug, but I've run it for probably 5 or 10 minutes total now and it's limbered up and even cold it turns smoothly now. A much better video will be posted in the finished section, once I've lacquered the base and made the plug for the burner and such.

But, it runs!

http://www.youtube.com/watch?feature=player_detailpage&v=taq6-_tfe1M

PS I couldn't embed this video using either Photobucket or YouTube. Hence the link. Could someone tell me how to embed this?