decisions on motor bike configuration

[bigoilbob]

Thanks keatonx, I was trying to account for Fabian's enhanced low end torque mods.

I think these numbers are very valuable to those of us who don't want to repair/replace over and over. For both engines and other drive components. Wouldn't it be nice if there was a place for them to repose? Like a forum or something? I'm either working my *** off in another land, or sitting on it here in south St. Louis, so I might try and help out here, as Loquin did with state regs.

 

[Fabian]

Rock Solid Engines has a dyno for these small engines and the best (stock) 66cc engine has produced 1100 watts, or 1.5 horsepower, on a good day.
I found a formula somewhere on the net which allowed me to calculate rear wheel power from my top speed and total vehicle weight.

At that stage my bike engine was stock standard with a modified muffler and optimised jetting. It put out 750 watts at the rear wheel or 1 horsepower "on a good day", and there were other days that it would run like a dog, only pushing out 600 watts at the rear wheel.

For this reason, i don't believe a word of the 2.5 or 3.0 horsepower engine claims.

Even now with all of my engine modifications, it doesn't give any meaningful extra peak power but has noticeably improved low and midrange torque; the engine can fall back to 2,200 rpm and it doesn't want to quit, and it will drop all the way to 1,600 rpm before it stalls.
Prior to the modifications, engine torque would fall off a cliff after 3,000 rpm.

 

[Fabian]

Stock HT maxxes out at around 5500rpm, so assuming the engine makes max power at 5000rpm or so

That's closely mirrors my experience with peak engine power, as mine makes max power at 4,800 rpm and max torque (with my engine modifications) is 3,500 - 3,800 rpm; tractoring away nicely at 3,500; my bike sits in top gear most of the time with the engine spinning between 2,800 and 3,800 rpm.

 

[Fabian]

@ bigoilbob

This information may be useful: http://www.fatigue.org/minutes/Spring-2005/DowlingBrasilPaper.pdf

 

[bigoilbob]

Thx Fabian. These are the referenced Goodman stresses, under another name. But all those partial differential equations are too much like my every other month day and night job. I would be happy with a table of max allowable and continuous duty torques/tensile stresses for commonly used MB drive components. Maybe available in a user forum......

 

[butterbean]

If you power shift a lot (power shifting means shifting under load, not disengaging the clutch or slowing down) I think an internally geared hub is likely to self destruct quicker than a cassette. On a cassette, the chain will skip gears, jump or even snap many times before the cassette will break (doesn't mean the cassette won't break, but the spring in the derailleur is likely to absorb at least some of the extra load, but eventually the casette may and probably will self-destruct if consistently shifting under heavy load) but with an internally geared hub, there is nothing to absorb any of the force and the planetary gears inside will just strip teeth or snap under the force. Whether you go with a cassette or internally geared hub, your best bet is to go with something heavy duty and try not to power shift whenever possible.