The Shape of Things to Run - First Fo Mi Chin Pics

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larry cottrill
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The Shape of Things to Run - First Fo Mi Chin Pics

Post by larry cottrill » Tue Aug 03, 2004 6:13 pm

Fo Mi Chin, from front plate welding through finished engine shell.

All comments welcome.

L Cottrill
Attachments
Fo_Mi_Chin_designer1_crop1.jpg
Daliesque view of engine and designer. Photo Copyright 2004 Larry Cottrill
(76.41 KiB) Downloaded 845 times
Fo_Mi_Chin_shell_fully_welded_crop1.jpg
The fully welded shell - detail of tailpipe/intake/chamber junction. Photo Copyright 2004 Larry Cottrill
Fo_Mi_Chin_shell_fully_welded_crop1.jpg (50.48 KiB) Viewed 7124 times
Fo_Mi_Chin_fitting_pipe_to_chamber_crop1.jpg
Fitting tailpipe/intake assembly to chamber; note slight notch at the top of the rim to clear the intake. Photo Copyright 2004 Larry Cottrill
Fo_Mi_Chin_fitting_pipe_to_chamber_crop1.jpg (55.44 KiB) Viewed 7122 times
Fo_Mi_Chin_intake_in_hand_crop1.jpg
The finished intake, welded, flared and flattened. Photo Copyright 2004 Larry Cottrill
Fo_Mi_Chin_intake_in_hand_crop1.jpg (37.11 KiB) Viewed 7122 times
Fo_Mi_Chin_front_plate_plug_crop1.jpg
Front plate welded all around, with spark plug temporarily mounted. Photo Copyright 2004 Larry Cottrill
Fo_Mi_Chin_front_plate_plug_crop1.jpg (44.46 KiB) Viewed 7122 times

steve
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Post by steve » Tue Aug 03, 2004 6:23 pm

but does every man really want it? :-)
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Post by Mark » Tue Aug 03, 2004 6:23 pm

Not bad. Not bad at all. I like the surreal look too, the asymetric plug and ordinary household objects finding other uses.
Mark

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Post by larry cottrill » Tue Aug 03, 2004 6:25 pm

steve wrote:but does every man really want it? :-)
Not if he has to build it himself -- only the masochists among us will line up to try one on that basis.

L Cottrill

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Post by steve » Tue Aug 03, 2004 6:35 pm

compared to the electra the construction on this one is probably more trouble then it is worth.

ignition might be difficult with the plug so far away from the intake stream: I'm thinking the CC area may be dead air during startup but I am probably wrong.

looks great!
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Post by Mark » Tue Aug 03, 2004 6:50 pm

I don't know why everyone likes to weld the spark plug on when you could just put a nut on the opposite side and tighten it down in the manner the Dynajet and Tigerjet do. A long ratchet with extension would do the trick to get inside the can. You might could get away with leaving the bottom of the can, (or top of the jet) alone and not invert it or beat it flat or beat it/hammer it concave.
I think Larry's prototype looks nice regardless.
Mark

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Post by larry cottrill » Tue Aug 03, 2004 6:54 pm

steve wrote:ignition might be difficult with the plug so far away from the intake stream: I'm thinking the CC area may be dead air during startup but I am probably wrong.
Yes, Steve, I think this is wrong [and I certainly hope so!]. If that were the case, it wouldn't roar for me -- and it does, even if I just have the slightest trickle of high-speed air going in. I don't have problems during startup [meaning with supplemental air running], just when I try to take the air away. Of course, the long path length might have something to do with that. The length of the chamber wall is only five inches, though, and the intake is shorter than on the Elektra, so the total length the air/fuel stream has to travel isn't all that different.

L Cottrill

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Post by jmhdx » Tue Aug 03, 2004 8:22 pm

I'm impressed, thats a very memorable image, foam can indeed.
Is this the first engine we've seen with the "gap" after acceleration?.
Obviously reynst and the bcvp have this function but this is a single chamber two pipe motor with gap after acceleration which for my money should stop it getting out the intake. Gas moving rapidly in one direction
cannot expand fast enough to exert as much pressure in a perpendicular plane as if it was static. Hopefully atmospheric pressure will continue to push air down the intake even during expansion phase.
Am I talking out of my *rse?
Mike.

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Post by steve » Tue Aug 03, 2004 10:04 pm

Larry Cottrill wrote:
steve wrote:ignition might be difficult with the plug so far away from the intake stream: I'm thinking the CC area may be dead air during startup but I am probably wrong.
Yes, Steve, I think this is wrong [and I certainly hope so!]. If that were the case, it wouldn't roar for me -- and it does, even if I just have the slightest trickle of high-speed air going in. I don't have problems during startup [meaning with supplemental air running], just when I try to take the air away. Of course, the long path length might have something to do with that. The length of the chamber wall is only five inches, though, and the intake is shorter than on the Elektra, so the total length the air/fuel stream has to travel isn't all that different.

L Cottrill
I didn't read the other thread untill after I wrote this, hence the unfounded concerns. Lets hope the actual problems with it are easy to remedy!
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Post by larry cottrill » Tue Aug 03, 2004 10:24 pm

jmhdx wrote:Is this the first engine we've seen with the "gap" after acceleration?.
I hope so ...
jmhdx wrote:Obviously reynst and the bcvp have this function but this is a single chamber two pipe motor with gap after acceleration which for my money should stop it getting out the intake. Gas moving rapidly in one direction cannot expand fast enough to exert as much pressure in a perpendicular plane as if it was static. Hopefully atmospheric pressure will continue to push air down the intake even during expansion phase. Mike.
That is exactly the point of the design -- absolute cutoff during the expansion phase. To get it, you put it at the point where the flow is at maximum velocity and the static pressure is at minimum as the gas goes by. True Reynst breathing -- it is supposed to be better than the Chinese in that particular respect, though the Chinese has a smoother flow path along the bottom chamber wall toward the front.

L Cottrill
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Post by larry cottrill » Tue Aug 03, 2004 10:29 pm

Mark wrote:I don't know why everyone likes to weld the spark plug on when you could just put a nut on the opposite side and tighten it down in the manner the Dynajet and Tigerjet do. A long ratchet with extension would do the trick to get inside the can. You might could get away with leaving the bottom of the can, (or top of the jet) alone and not invert it or beat it flat or beat it/hammer it concave.
I think Larry's prototype looks nice regardless.
Mark
Mark, in this case you'd have a lot of fun hitting the spot with a minimum 26-inch extension and a socket that has to get past the part of the intake that's dropped halfway across the tailpipe where it joins the chamber.

Of course, with an engine this exotic, we could just design something for that and sell it for $97.95 US as Tool FMC-208-36F17-C and bring in a little extra income. Maybe not a bad plan.

L Cottrill

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Post by Mark » Tue Aug 03, 2004 11:41 pm

I guess I was thinking you could put the plug in before the can was welded to the exhaust tube. If you welded the nut to the can then you could replace the plug anytime it fouled.
I would opt to keep the side port from intruding into the high traffic area and go with a traditional merger where the side port is flush but not blocking the in/out flow. I don't know though, it might do fine and certainly fresh air coming in the side port will offer some cooling.
Mark

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Post by larry cottrill » Tue Aug 03, 2004 11:48 pm

Mark wrote:I guess I was thinking you could put the plug in before the can was welded to the exhaust tube. If you welded the nut to the can then you could replace the plug anytime it fouled.
I would opt to keep the side port from intruding into the high traffic area and go with a traditional merger where the side port is flush but not blocking the in/out flow. I don't know though, it might do fine and certainly fresh air coming in the side port will offer some cooling.
Mark
Mark -

The idea for that location is to get it at the maximum velocity zone in the stream. The fact that the lower end of the intake tube also takes up space forming a 'pinch' is also supposed to help maximize velocity in that section of the pipe. It does, of course, also have the effect of increasing tailpipe impedance, as you are suggesting.

L Cottrill

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Re: The Shape of Things to Run - First Fo Mi Chin Pics

Post by Bruno Ogorelec » Sun Aug 15, 2004 12:48 pm

Reminds me of the thoughts I had when perusing the Burns Stainless catalog, and which Dave Long (?) of Buffalo had before me -- why not put this Y-collector at the end of a can (preferrably connecting the two with a diffuser cone) and have one arm of the Y serve as the intake and the other as exhaust? Use a short straight tube for intake and a long straight tube for exhaust. Or use Lockwood-style cones or Escopette-style bustles or whatever else you think might work. A quick way to get a valveless engine. Should make for an interesting mixing pattern on intake.
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Post by larry cottrill » Tue Aug 17, 2004 3:34 pm

Larry Cottrill wrote:
steve wrote:ignition might be difficult with the plug so far away from the intake stream: I'm thinking the CC area may be dead air during startup but I am probably wrong.
Yes, Steve, I think this is wrong [and I certainly hope so!]. If that were the case, it wouldn't roar for me -- and it does, even if I just have the slightest trickle of high-speed air going in. I don't have problems during startup [meaning with supplemental air running], just when I try to take the air away. Of course, the long path length might have something to do with that. The length of the chamber wall is only five inches, though, and the intake is shorter than on the Elektra, so the total length the air/fuel stream has to travel isn't all that different.

L Cottrill
Steve et al -

I just realized that I haven't revealed an important bit of observation -- the heat pattern visible on the chamber as this critter runs.

The hot zone is along the bottom and running up against the front dome, leaving the rest of the chamber dark. It is as if combustion is starting as soon as the fuel/air mix hits the bottom side of the can and then pours across lengthwise and smashes up against the front end, like huge ocean waves coming in against a cliff and exploding upward in plumes of spray. Very odd pattern, and one that could be indicative [perhaps] of inadequate breathing for the size of the chamber, it seems to me.

What do you think of it? Too bad I don't have a photo of it, but my description is about as accurate as anything I could think of.

L Cottrill

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