Philip Duclos Fire Eater

[CFLBob]

Much to my surprise, the graphite rod just arrived in the morning's mail. I was expecting no earlier than Monday.

Time to remake the piston with a tighter fit.

 

[werowance]

good luck, cant wait to see if this fixs it.

 

[CFLBob]

good luck, cant wait to see if this fixs it.

You'll find this interesting: before taking the engine apart, I sprayed the cylinder with one of those compressed air in a can dusters. If you turn those upside down, you get out the propellant, which is a refrigerant and it will chill what you're working on down below zero (F). Did that for a while, and then put the lamp next to the valve opening. It ran for over 10 seconds. Long enough for me to grab my phone and start fumbling with it to take a video.

And then it slowed down and stopped. It must have seen the camera.

 

[fcheslop]

Thats good news glad you are on the way to a runner
cheers

 

[Cogsy]

Seems like you've found the problem. Not long now and the trouble you've had will make the first run even sweeter!

 

[CFLBob]

Unfortunately, as they say at NASA, I screwed the pooch on this and my replacement was barely better than the original. Still wouldn't run, but I could tell it was too loose before I tried.

I had already started on the third attempt at a graphite piston before this occurred to me, but if this doesn't work I think I'm going to use the CRS bar I bought to make the piston in the first place. If the CTE is so different that I need to make the piston virtually stuck in the cylinder until the cylinder is heated up, I think maybe the original material is a better choice the graphite.

 

[minh-thanh]

Pistons can be made of cast iron or brass with steel cylinder (I also tried aluminum pistons, it was ok with little oil )

 

[minh-thanh]

I need to make the piston virtually stuck in the cylinder until the cylinder is heated up, .

I do not know if it's okay or not, I just try to make the piston sealed but move in the cylinder as smooth as possible.

 

[CFLBob]

After a lot of delicate sanding, my third graphite piston just wouldn't get into the cylinder. I tried heating the cylinder with my butane torch to get the piston into the cylinder before I assembled it and still couldn't get the piston to fit.

Back to the lathe, a strip of 400 grit sandpaper and then a few seconds of sanding and now it's too small. I don't think I took off more than .0005.

This is way too sensitive for me. Before I take it outside and drive my car over it to turn it into a bunch of misshapen scrap, I'll try making a piston out of CRS or something.

The bar of CRS I bought is marked that it's 4130 steel. Is that a reasonable alloy, or should I try to find a bar of cast iron or what? The drawing in Duclos' book says, bronze, cast iron or CRS. Since those aren't materials so much as families of materials, I got whatever CRS that Online Metals had in stock.

Oh, BTW, before I put everything back together, I lapped the area around the valve opening on sand paper on a block. 400, 1000, 2000. It looks pretty nice and the wear pattern was very flat. No high or low spots.

 

[fcheslop]

Hi Bob, a bit late .To polish a graphite piston use brown paper bag or the rough side of cardboard
Iv used graphite in the past but gave up on the mucky stuff it has its advantages but for this engine Im not convinced
The alloy cylinder may expand a wee bit while the graphite wont expand much
My engine and Little Blazer has pistons from Bronze Alloy horrible stuff to machine and tough as the hobs of hell but has ran many hours and the material was free from an old stop valve spindle
Try CRS as you have it
Keep plodding on the grin will be from ear to ear when it eventually runs well

 

[CFLBob]

Test of my third graphite piston. This is about as good as it gets, and that's after chilling the cylinder with "freeze mist" until it's frosty (which doesn't last long in the 80 degree garage).



After I stopped the video, I played with it a little more and got another 3 or 4 seconds out of it.

 

[Gedeon Spilett]

wow, you have got it, nice ! congratulations !
the engine stops when starting from cold as water from the combustion condenses inside, and increases drag, this is usual...
once the temperature of the engine reaches its running temp, in 2-3 min, the engine runs indefinitely....

 

[CFLBob]

the engine stops when starting from cold as water from the combustion condenses inside, and increases drag, this is usual...
once the temperature of the engine reaches its running temp, in 2-3 min, the engine runs indefinitely....

I've never heard that!

Does it help to warm the cylinder first? Is there something that can be done to reduce or eliminate that 2-3 minutes, so that it starts and keeps running?

A friend asked me if chilling the cylinder before starting the engine worked by shrinking it or changing the temperature difference across the engine. I had never thought of that, and don't have an answer for him.

 

[Gedeon Spilett]

Yes, it helps a lot to preheat the engine with the hot air gun...
this problem with condensation is something well known and often discussed...
you're not far from a good runner !

 

[werowance]

hi bob, what I did (and I know its against the rules) is I hand sanded the last bit off my piston with a piece of emory and then I used scotch bright pad in my hand - scotch bright actually removes a lot of material when using it against graphite, using the piston rod as a handle I spun it in my hand and had to force it in the cylinder. yes I know that doesn't generate a perfectly round or square edged piston but it worked for me. here is a video showing how tight my piston is when cold it wont budge, any movement you see is just slack in the wrist pin and crank journal to rod fit. that graphite isn't budging



next video shows it starting up after a little preheat, then you will notice after it gets warmer it speeds up, then it passes that perfect fit and gets a little to big and slows down a bit but still tight enough to keep it running

 

[CFLBob]

Can't thank you enough for those videos. I was just about where the first one is, except that I couldn't push the piston into the cylinder. I had visions of breaking the top out of the piston by pushing on the rod. That's when I put it back on the lathe and took a few turns against sandpaper (400 grit). It's still loose enough to move in the cylinder and not as tight as yours shows, so it may be that mine is stopping because it's losing compression and not condensation in the cylinder.

I'll experiment with it some more, try my hot air gun to warm the cylinder up a few degrees above room temp and see if it runs any better.

 

[CFLBob]

Heating in advance doesn't seem to work, based on a few tries.

 

[werowance]

when fitting the new piston, might heat the cylinder a little bit to get a measurement from. just a thought that it might make it easier to get that tight fit, but then again holding that hot metal might not be fun to hold....

 

[werowance]

and on the heating in advance to reduce condensation - on mine I don't have to wait for it to get that hot, I will often start mine up with a little condensation still showing. I run it a lot, practicly anyone who comes by to visit and will stand still long enough for me to get it out lol and I have not gummed it up yet. now yes when trying to first get it running I gummed it up often but it seems that with mine now if I run a tank of fuel out any gum or buildup is either burned out or something because I did disassemble it after many many runs and a paper towel soaked in alcohol came out clean when wiping it out.

 

[CFLBob]

Started on the CRS piston yesterday and got called out of the shop. I'll get that fitted later.

Last night I found that if I just let it sit at room temp, it will start up on its own, run a few seconds until it warms up and then stop. It's so close ... Not even sure I need the new piston, but I haven't cracked the code that lets it run for a few minutes.