Philip Duclos Fire Eater

[CFLBob]

way to think outside the box!

The box came back as my safety to keep from accidentally putting a finger where it'll get hurt.

Plain old cardboard box. I'd like to take credit, but it's my wife's idea. One flap is folded into it and the two pieces of cardboard make it thick enough that it wedges behind the lever with B and C on it. Yeah, I can push the box out of the way, but not the kind of brush against it that I might do by accident.

I'm hoping that if I'm wrong someone searching the web for "SC4 threading" or "LMS3540 threading" comes along and tells me how to do it better.

The graphite piston is cut slightly oversized, hollowed, drilled through and slightly oversized. Now comes the meticulous part of putting it on the push rod, trying to fit, taking it off the push rod, turning a little more and so on.

 

[CFLBob]

The piston is done and the size tweaked in. I can feel it pull a vacuum when I pull it or push it in the cylinder.

Since the advise here wasn't unanimous, I decided to leave the piston walls 1/8" thick. No particular real reasons. The only portion of the piston made exactly to the plans for a metal piston say is the middle of the cap where making it too thick would keep the three threads on the yoke from sticking through.

I'm really not sure what percentage done this makes me, but there's a handful of very intricate little parts that have to be done. The cam, cam roller, roller shaft, roller fork, valve and a few others.

I'll say somewhere around half done.

 

[werowance]

Hi bob, was just reading your build. concerning the graphite piston, I just wanted to throw this out there:
I just finished a flame eater and like to have never got it to run, the final solution was this:

my cylinder was 303 stainless, the piston and valve were graphite. the 303 would expand so much when up to operating temp that it wouldn't run.
solution was to make the piston and valve so tight that when cold the engine was completely seized up. but once warm it spun freely. I think the stainless expands so much more than graphite does that it was leaking to much vacume.

but your build is coming along nicely. and looking good

 

[werowance]

and on the piston yoke, that was the hardest part on mine to make as well. looks almost identical

 

[deverett]

I'm really not sure what percentage done this makes me, but there's a handful of very intricate little parts that have to be done. The cam, cam roller, roller shaft, roller fork, valve and a few others.

I'll say somewhere around half done.

If you are anything like me, with 50% done that leaves only about 90% to go with all the forgotten bits to make and remake!

Dave
The Emerald Isle

 

[CFLBob]

Hi bob, was just reading your build. concerning the graphite piston, I just wanted to throw this out there:
I just finished a flame eater and like to have never got it to run, the final solution was this:

my cylinder was 303 stainless, the piston and valve were graphite. the 303 would expand so much when up to operating temp that it wouldn't run.
solution was to make the piston and valve so tight that when cold the engine was completely seized up. but once warm it spun freely. I think the stainless expands so much more than graphite does that it was leaking to much vacume.

but your build is coming along nicely. and looking good

Interesting... My cylinder is aluminum, so expansion will be different. Probably worse, because I think aluminum has a higher CTE than 303. The piston pulls a vacuum. If I put my thumb over the slot on the cylinder I can definitely feel the pressure both pushing into and pulling out of the cylinder. There's a slight rough spot about halfway down the cylinder, but I'm not going to do anything about it, yet.

If you are anything like me, with 50% done that leaves only about 90% to go with all the forgotten bits to make and remake!

I always thought the last 10% of the work took 90% of the time. That's how it was when I was working. I hope to finish by December.

 

[CFLBob]

I need to ask for help of the members that have built one of these Duclos engines.

The week was a bit slow, as I had to wait on a tool I needed to order, and the only part I finished was the valve. For this, I moved over to my Sherline CNC system. (Disclaimer: none of those scars in the vise have been made in the last couple of years)

I'm starting on the cam and some of the small, fiddly bits. I come across this screw:

I'm stumbling over this. Notice over the left where it points out the thread as 4-40 and then shows lines extending over the threads and dimensioned .156.

Those don't go together. A 4-40 screw has a major diameter of .112 by my tables. .156 is between #6 and #8. The lines aren't extending from it, but is that supposed to be the OD of the shoulder? There's nothing else that seems to indicate the diameter of that section.

How would you make such a thing? I'm tempted to get a flat headed 4-40 screw and put a .188 long clearance sleeve on it. If I have to flatten the head of the screw in the lathe, or on a belt sander to make it .032 high, that's probably easier than threading that 1/8" long section.

One of the parts I cut a few weeks ago was a piece that's like the sleeve I'd need to make if I did this but larger in diameter - if that .156 applies there. A #34 drill bit is 0.111, which would clear most #4 screws. Looking at the book, I don't see where this sleeve goes.

Looking through the chapter on this engine, I don't really see any mention of where these parts go, or how to put it together.

Looking for any advice on these parts I can get.

 

[fcheslop]

You can make the major diameter to what ever you like within reason and then bore/ream the roller to match.Again the thread canbe what ever is available my engine is a BA size.
The pin screws into the forked L shaped part that carries the valve spindle and carries the cam follower
Not sure about the bushing and would have to check just cannot remember
I can do a wee pic if needed of my old banger

 

[CFLBob]

This screw goes into the cam roller, right? It says to ream the center to 5/32 which is .156, so I can see where that number comes from.

I'm still trying to figure out how to make that piece, given what I've got to work with. I get what you're saying about it can be anything as long as the parts match. What I'm concerned about is that the thread is drawn all the way up to the .156 portion, and I don't think I can work right up to it. I have a small 60 degree thread cutter, 1/4" shank, but I think that still takes a corner off that .156 shoulder. Or else I stop one or two turns away from it.

Pics would be cool, but maybe I can just ask how much of that thread extends out of the nut when it's put together. On the wrist pin yoke, there were only three threads sticking through the piston and the nut took up all three of them. If this is the same way, I'm less concerned about my cutter taking a bit off that .156 shoulder.

 

[Cogsy]

I could be/probably am, completely wrong, but looking at it the shoulder is given as 5/16" isn't it ("5/16 under the head")? I would then assume the 4-40 is a female thread into the .156 projection. I have no idea if this makes sense as a part but it makes sense (to me) based on the drawing.

 

[fcheslop]

On my engine from memory I counter bored the part it screws into or under cut at the threads shoulder
I simply turned the pin to what ever I decided on at the time (20 plus years ago) then reversed in the chuck to face the head and cut the slot by hand now I would set it up and use a slitting saw
The threaded portion has no nut as its for the tapped hole and on my engine one thread protrudes
The head of the screw is ony 1/4 dia but it canbe bigger

 

[fcheslop]

Just checked and I did counter bore for the cam followers pin and also undercut the thread on the pin by around 1/32 wide.Just enough to allow it to seat properly

 

[CFLBob]

Thanks for taking it apart and grabbing those pictures. Like they say, a picture is worth a thousand words.

I'm less concerned about cutting that thread, now. I usually leave some slop at the end of the threaded part, so that I don't have to stop it exactly at the same point every time. Like in my picture of the parts in post 57. That cutoff tool I used was too wide, but that's the general idea.

 

[fcheslop]

Glad thats cleared up and good luck with the rest of the build
It is a great design and my engine has done many hours running at shows and still fires up easily despite a few rough edges. It was the first of many flame gulper engines I built
I keep promising to to tidy it up but never get round to it
Just grind up a short thin parting tool for those jobs it will last for ages or make one from a wee bit of old slitting saw blade
I have a bit of square key steel drilled and tapped with a simple shouldered bolt and often use this with a slitting saw mounted to it for cutting grooves.A wee bit rough ar++d but it works even for cutting fins and the small slitting saws are cheap enough and you can stack them together .
cheers

 

[CFLBob]

Done except for parting off.

The metal scale was to prove to myself that it was cut through properly.

Either the cam roller or the cam roller shaft (screw) is next.

 

[CFLBob]

Just checked and I did counter bore for the cam followers pin and also undercut the thread on the pin by around 1/32 wide.Just enough to allow it to seat properly

Back to this little screw again. I just made the Cam Roller, and since I didn't have a 5/32 reamer in my set, I just drilled it to 5/32. The drawing for the screw says to make that shoulder 0.156 and the calculator says 5/32 is 0.15625. I figured I'd machine the screw to match the roller.

Does the Cam roller spin on this shoulder or is it press fit on?

 

[fcheslop]

It spins
If you dont have a reamer a slot drill will do the job or better still make a D bit much cheapness and very usefull bits of tooling

 

[CFLBob]

It spins
If you dont have a reamer a slot drill will do the job or better still make a D bit much cheapness and very usefull bits of tooling

Thanks. I'll turn it to a loose fit in the cam roller.

The cam roller came out pretty cool looking in the rotary table. I was trying to figure out how to cut that relief between the hub and the outer rim, and a friend said "you're going to put it on the rotary table to drill those holes, can you just mill a ring there?" I used a 1/8" HSS end mill and it worked fine.

Edit for writing error. 1628 EDT

 

[CFLBob]

This took longer to do than it should, but I did everything on my micro lathe (Sherline) and had to spend an extra couple of days trying to remember how to set up the threading attachment and then make a couple of practice pieces.

 

[CFLBob]

Next part; the roller fork alongside that screw. Relatively enormous by comparison. It could use lapping on some sandpaper.