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BLACK BELT
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6,913 Posts
Discussion Starter #362
You're doing some good stuff Smoker.
Thanx, bro.

Taking a short time-out, but can't resist doing a little work now and then. :D

The only chambers I have are '87 stockers and Toomey pipes, so I'm using the dimensions of the Toomey pipes to rough design some (MX) up-pipes.

Next, I'll assemble the cardboard cutouts on the armature wire and see what shape I come up with.



 

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GURU
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8,827 Posts
are you going to buy some bashed mx pipes and use parts to make one or are you going completely from scratch? I saw a good site years ago where guys were building expansion chambers by thermo-forming them using pressure washers. I havent been able to find it but it was interesting to say the least.

If you are going from scratch may i suggest making yourself some nice hammer-forms out of wood
 

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V4's FTW
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10,492 Posts
If you are going from scratch may i suggest making yourself some nice hammer-forms out of wood
C'mon Matt, how's the man ever gonna finish if he stands around beating his wood?? :wtf: :oops:







:LolLolLolLol:
 

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BLACK BELT
Joined
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6,913 Posts
Discussion Starter #366
are you going to buy some bashed mx pipes and use parts to make one or are you going completely from scratch? I saw a good site years ago where guys were building expansion chambers by thermo-forming them using pressure washers. I havent been able to find it but it was interesting to say the least.

If you are going from scratch may i suggest making yourself some nice hammer-forms out of wood
New from scratch.

Yeah, not sure what the best way is to form rings and cones out of flat stainless.

I'll probably do the basic design - but hope a two-stroke pipe expert can fabricate and weld the actual pipes. I may be able to form the pipes, but wouldn't attempt the welding.
 

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BLACK BELT
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6,913 Posts
Discussion Starter #367
Working on the up-pipe design, so I can mock up the "V"-shaped radiator and front engine cradle, then make sure it all fits together with enough front wheel clearance.






In this pic, the front wheel is turned all the way to the right, showing where the radiator will go between the forks and the pipes.

 

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Ridin' Dirty
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6,773 Posts
Looks great man.

Can you make any other curves or anything so that the largest portion of the pipe can be a little lower? Seems like once the pipe is headed up, it goes straight up. Like maybe a curve toward the rear of the bike midway up the vertical section?


How much do you know about expansion chamber design? Can there be turbulence because of strange shapes of pipes, or is the air already turbulent, so all that matters is the diameter vs the distance from cylinder?
 

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V4's FTW
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10,492 Posts
Looks great man.

Can you make any other curves or anything so that the largest portion of the pipe can be a little lower? Seems like once the pipe is headed up, it goes straight up. Like maybe a curve toward the rear of the bike midway up the vertical section?


How much do you know about expansion chamber design? Can there be turbulence because of strange shapes of pipes, or is the air already turbulent, so all that matters is the diameter vs the distance from cylinder?
I'm gonna say right off the bat that I've never tried to design a 2-stroke pipe, but that pipe with the 90º bend right in the middle of the fat part just doesn't look conducive to proper tune?
 

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GURU
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8,827 Posts
The bends arent really all that crucial. What is crucial is the straight section before it expands, the volume of the expanded section and its transition to and from straight again(convergent and divergent sections). The idea is to create a negative pressure zone next to the heat(transition from small diameter to larger) to help suck out the exhaust gases. If you kept the shape the same between several pipes but only changed the length of the straight section right out of the head you would be shifting the power band around a little. A shorter section might produce a good "hit" up top while a longer section would shift that down into the low/mid range more.


Smoker, isnt that a knee melter there?:) Its very cool looking
 

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BLACK BELT
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6,913 Posts
Discussion Starter #372
Looks great man.

Can you make any other curves or anything so that the largest portion of the pipe can be a little lower? Seems like once the pipe is headed up, it goes straight up. Like maybe a curve toward the rear of the bike midway up the vertical section?


How much do you know about expansion chamber design? Can there be turbulence because of strange shapes of pipes, or is the air already turbulent, so all that matters is the diameter vs the distance from cylinder?
I think adding curves would be detrimental to the performance. ;)

The general shape if the pipes is dictated by the frame, radiator, coolant hose, etc. The diameter of the sections is no problem to change, and the length of the sections can be altered somewhat to better match the engine characteristics. Those recommendations will have to come from pipe experts, I just used the Toomey pipe dimensions to get started.

I know a fair amount about expansion chamber design and construction. Getting pipes dialed in for a specific engine takes a lot of dyno time and rebuilding the pipes many times over. I'm just hoping my pipes will be in the ballpark and give a fair result.
 

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BLACK BELT
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6,913 Posts
Discussion Starter #373
I'm gonna say right off the bat that I've never tried to design a 2-stroke pipe, but that pipe with the 90º bend right in the middle of the fat part just doesn't look conducive to proper tune?
Almost all MX pipes have right angle bellies. Late model pipes have more curve than bend, but right angle bellies have been around for many years.

 

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BLACK BELT
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6,913 Posts
Discussion Starter #374
Smoker, isnt that a knee melter there?:) Its very cool looking
These pipes are gonna sear that delicate inner thigh area above the knees.:fire:

Will also be cooking my shins, the radiator and coolant, the fuel tank and fuel, the electronics, the paint on the frame, and most likely my nuts. :letsride:

Hopefully, I can make things tolerable with the use of heat-shielding.
 

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BLACK BELT
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6,913 Posts
Discussion Starter #375
Don't know if you can tell from these pics, but when I sit naturally - the converging cone fits right between my leg and the frame.



 

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GURU
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8,827 Posts
yeah i dont know about that one. I know my mx pants have some heavy duty material there but not that high up. The worst bike I had was an 86 rm250 where the chamber stuck up pretty high and it was a little toasty. Thats considering you are standing up most of the time and only sitting down in turns. With this your leg will be there the whole time.
 

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Ridin' Dirty
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6,773 Posts
+1 to saber and shift


I think you need to add a serious half loop or something under the bike to get the meat of the chamber lower.


What about having the pipes cross, aka, left dump on right, right dump on left?
 

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BLACK BELT
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6,913 Posts
Discussion Starter #379
Not too worried about the heat. Plan to use header wrap and carbon fiber heat shielding. I can also change the shape and routing of the pipe somewhat, but I want to retain as much performance as possible.


Chopped a couple of brackets that were in the way of the mockup radiator. Will clean up the frame later.



I think the radiator needs to be about 1/2 inch wider on each side.



 
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