Hydroformed exhausts. Expansion chambers and Megaphones

[Billy Golightly]

Power Pros? The reason I said what I did is because, if you look at all the aftermarket pipes that are not coned sections, you will see they have a weld lines that are relatively flat. I'll use my FMF 250R pipe for an example. Because your only working on one plane, you have cut out and Hydroform the pipe in sections, and then weld it together. Thats where the multiple pieces come in the design. Actually stamped pipes, like a stock 250R one, have an external thin ridge that runs the full length of the pipe, usually like a1/4 inch high. Those are stamped.

[Bryan Raffa]

Dynoport stamps them out with the curve of the pipe in it .. they just weld it together.. that seems simpler , Im shure that how the stockers are done

[XL-erate]

Thanks, Billy, excellent info!

DON'T USE AIR!

As mentioned in Michael Moore's article in footnotes, air is compressible, water is not [at the pressures dealt with here]. Most common pellet guns seen today use the 'spring air' principle. A spring attached to a rod & piston in a cylinder is cocked, or compressed. Piston pressure outlet is into barrel, with a pellet in front of piston's air outlet. Pulling the trigger releases the spring, ramming piston forward in its bore and compressing all the air behind pellet. You know what happens next.

Using air to hydroform is similar to pointing the pellet gun at you head, cocking the trigger and hoping it doesn't go off! Because you're compressing the air it builds up and stores kinetic energy, behind the steel, just like a huge spring. A materials or weld failure then ruptures steel and it's just like pulling the trigger, to suddenly release all that 'air spring' pressure and rip metal into shrapnel chunks. Metal fragments are like the pellet. At 1,000 psi you can shoot and kill a deer or human with a single spring-air fired .22 cal pellet, smaller than a pencil eraser. Make sense?

Steel has a modulus of elasticity that allows it to maintain its molecular strength while bending, so this amount of elastic property actually holds the metal's molecules together as if it was in a die stamping form. The water pressure builds up against the interior surface, same as air, but the liquid doesn't compress: therefore no compressed 'air spring'.

Sorry I can't explain it better but bottom line: gas/air pressure accumulates energy and its explosive force can maim and kill; water pressure immediately dissipates only surface pressure, not stored energy. Please, don't experiment with air in this type of project, it's Russian Roulette!

[Billy Golightly]

http://www.jalopyjournal.com/forum/s...ad.php?t=77692

I stumbled across this link on another forum I lurk for their tech (great stuff too) and I figured I'd post it up.

[NOS_350X]

I realy think that to make something decent will take TONS of work. But The cr500 in my 400ex chassis was going to get trashed because i keep braking pipes. SO im going to try and make me a OOF drag pipe for it. See if it willstay together then.

[NOS_350X]

i got a quick question, From what your reading do you have to get a pump that will pump only water? If so can i modify the tip on my presure washer? OR can i fill up with water put a cap with a shrader valve on it and preasureize with air??

[Billy Golightly]

No, DO NOT USE AIR! It needs to be pressurized from start to finish with water only. I suppose you could use a pressure washer, unless its a really big one I'm not sure it'd have enough pumping power to get the job done but it might.

[NOS_350X]

Ok, well i made up my template for my OOF pipe for my cr500 conversion. Mocked all the same tapers and size of the inframe pipe i had made. Im just going to use a thicker guage steel. going to get it all built and then figure out how to presurize it. Plumbers around here seem to have no idea wtf i could use.

[Billy Golightly]

Atleast with the pump you can take your time and see where the leaks are before they blow apart. Don't have that ability with the pressure washer, its gonna be putting out an awful lot of water when you pull the trigger.

[hondahaulic]

going to get it all built and then figure out how to presurize it. Plumbers around here seem to have no idea wtf i could use.

Know any farmers that live near, or someone with a tractor? Tractors have hydraulic pumps that pump oil to raise/lower hydraulic cylinders on equipment. These things put out a great deal of pressure. If you could get a male hydraulic coupler on one end of your pipe, I would bet it should work. By doing this, you would be using hydraulic fluid instead of water.

heres a link to a pic. of the couplers i was refering to. http://www.snap-tite.com/snaptite_QD...ages/L_60s.jpg

[NOS_350X]

I have a tractor with a front loader, and the hydraulic pressure it would push in would be WAY too much. Need a handheld hydrulic pump.

[money89tractors]

Reason water is used over air is because water/liquids dont compress. Air would simply make these pipes a small air tank with very thin walls and ready to explode. Water will simply push out in all directions without compressing.

Someone mentioned making a gas tank this way. It could be done. Biggest problem with it is if you want a flat panel on the bottom. You would have to make any flat areas out of a thinker steel to the rest of the metal will "form" to shape before the flat areas begin to "form".

-Phil

[Dirtcrasher]

Could a brake master cylinder be used as a pump for the water??

Just trying to think of things that build up pressure, like a grease gun.....

[NOS_350X]

I think the master cyl is a decent idea, would just take a long while of pumping to build up enough pressure. Ive already thought of a grease gun. But inside your pipe your going to have a ton of grease and water in a nasty mess. And figured it woudnt be worth it.

[SWIGIN]

well when water is in your brake lines it does compress....so use a master cly and cheap dot 3 fluid

im thinking like a truck MC not a atv MC