no I didn't weld the cones together wrong... haha. The pipe is based on specs for another rapido pipe. I just threw some angles in there to make more room to use the rear brake lever (right side shifting) and pull the pipe in closer to the bike. originally i planned on making an underseat exhaust but scrapped that idea due to the lack of room for an expansion chamber. a low pipe would be difficult as well thanks to the centerstand. i think the chamber should work just fine the way i have it and its still better than running the bike with no exhaust...i've still yet to run it with the new exhaust(fabricating brackets for it). i may very well build another exhaust in time.
1969 Aermacchi-Harley Davidson 125cc Rapido Cafe Racer
- Thread starter CAD_MOTO
- Start date
That's what i was thinking...just constructive criticism here...I think you did a beautiful job. Just saying it's probably not going to function as a expansion chamber is supposed to. http://en.wikipedia.org/wiki/Expansion_chamber
I was prepared for the constructive criticism haha. thats why i did my homework before the design process. i still appreciate your comments
excerpt from 2 stroke tuners handbook by gordon jennings
"Should this consideration of inconvenient bulk lead you to depart from the dimensions required by my formulae, think twice before you succumb to the temptation to flatten the expansion chamber. In the first place, you'll upset all the area progressions through the diffuser; an 8-degree diffuser, flattened ever so slightly, is no longer an 8-degree diffuser. Moreover, even if you calculate the areas so that you have a rounded wedge with the correct inlet/outlet area proportions, wave energy recovery will still suffer. Those waves simply do not like being puffed through anything but a cone; even less do they like a cone that has been dented or notched to clear a frame tube or to provide ground clearance. They can "feel" every change in cross-section in the containing vessel. They are, however, willing to follow even the most abrupt jog in the system: you can resection the diffuser cone and kink it all over the place to make the expansion chamber fit the motorcycle, and the wave will never know the difference. Sonic waves may be able to feel even the most minute changes in section; they will make any turn you can build into the system without slowing or losing any of their energy.
The only part of the system where you must be careful to provide smooth turns is up at the lead-in pipe and at the entry to the diffuser. Through that section, gas velocity is very high, and while the wave won't care about sharp jogs, such jogs will have a bad effect on gas flow - which is a different matter entirely ( gas flow involves the movement of matter; a wave is just energy, and being without mass, is also without inertia and therefore cares nothing about sharp corners. At least, that is very substantially the case here, where the velocities, etc. involved are low enough to fall within the scope of Newtonian physics; Einstein's unified field work is hardly applicable at wave speeds of such limited magnitude)."
excerpt from 2 stroke tuners handbook by gordon jennings
"Should this consideration of inconvenient bulk lead you to depart from the dimensions required by my formulae, think twice before you succumb to the temptation to flatten the expansion chamber. In the first place, you'll upset all the area progressions through the diffuser; an 8-degree diffuser, flattened ever so slightly, is no longer an 8-degree diffuser. Moreover, even if you calculate the areas so that you have a rounded wedge with the correct inlet/outlet area proportions, wave energy recovery will still suffer. Those waves simply do not like being puffed through anything but a cone; even less do they like a cone that has been dented or notched to clear a frame tube or to provide ground clearance. They can "feel" every change in cross-section in the containing vessel. They are, however, willing to follow even the most abrupt jog in the system: you can resection the diffuser cone and kink it all over the place to make the expansion chamber fit the motorcycle, and the wave will never know the difference. Sonic waves may be able to feel even the most minute changes in section; they will make any turn you can build into the system without slowing or losing any of their energy.
The only part of the system where you must be careful to provide smooth turns is up at the lead-in pipe and at the entry to the diffuser. Through that section, gas velocity is very high, and while the wave won't care about sharp jogs, such jogs will have a bad effect on gas flow - which is a different matter entirely ( gas flow involves the movement of matter; a wave is just energy, and being without mass, is also without inertia and therefore cares nothing about sharp corners. At least, that is very substantially the case here, where the velocities, etc. involved are low enough to fall within the scope of Newtonian physics; Einstein's unified field work is hardly applicable at wave speeds of such limited magnitude)."
pacomotorstuff
Coast to Coast
Not to steal this thread or anything, but your boss's Yamaha dirt tracker - is it a vintage Ascot Scrambler or something like that? Maybe your boss would like to post something about the bike on the trackers child board.
Glad the Rapido pipe dimensions were helpful.
Regards,
Pat Cowan.
Glad the Rapido pipe dimensions were helpful.
Regards,
Pat Cowan.
pacomotorstuff
Coast to Coast
Start a new thread. If its an Ascot or even a build of an Ascot, I'd love to see some photos - and I know a lot of the other guys would, too. They were a great bike back in the day.
Thanks,
Pat.
Thanks,
Pat.
CUNNINGHAMMER
Active Member
I don't know anything about 2 strokes, but I do love this bike. Keep the pics coming!
