Bicycle transmaission maximum torque

[Nipash]

Hi, I am thinking of mounting a motor like this: 125CC FULLY AUTO ENGINE MOTOR ATV PIT BIKE ATC 70 XR 50 CRF 50 SDG on my GT LTS and running the power through a modified SBP jackshaft and a rear derraileur system. So, the chain would be a standard 8-speed and the cassete and derraileur Shimano xt. Does anyone have any experience with putting this much power through a standard bicycle transmission? The reason I am doing this is because I want my MB to be legal but still have a transmission. It seems to me that the things that would be the main problem would be the maximum force the chain could withstand, breaking the teeth off of the gears and ghost shifting under power. I've read around a little and haven't found anyone who has put this much power through a chain-derraileur system. So I could always just try it and see what happens...

 

[happyvalley]

I think WAY too much power not only for a bicycle drive train but a bicycle frame, wheels and brakes as well. But that all might be besides the point since you wrote you want to be legal. Is this WA state and for use on the street?
I ask because my son is out there and he recently sent me this from the WA.gov:

"Moped" means a motorized device designed to travel with not more than three wheels in contact with the ground and having an electric or a liquid fuel motor with a cylinder displacement not exceeding fifty cubic centimeters which produces no more than two gross brake horsepower (developed by a prime mover, as measured by a brake applied to the driving shaft) that is capable of propelling the device at not more than thirty miles per hour on level ground.

http://apps.leg.wa.gov/RCW/default.aspx?cite=46.04.304

 

[Nipash]

Yes I am planning to use it on the street About legality, I spent around a month calling the DMV, WSP and talking to cops and everyone came up with a different answer. I also did a lot of reading here: Title 46 RCW: Motor vehicles and came to the conclusion that there is no law regarding gas powered mb's, just electric ones. So really, the most (legally speaking) they can do is impound it, which is not really a problem because I'll mostly be riding it on logging roads.

Also, I definitely made sure to beef up the other components on the LTS:

Front fork: Marzocchi Super Monster T Fork
Wheels: Modified 21" motorcycle wheels
Brakes:Hope Tech X2 Hydraulic Disc Brake at JensonUSA.com
Shock: FOX / Bike / Shocks / DHX Air 5.0
Motor mounts: Custom made out of plate steel similar to the SPB kit

I think the frame is up to the job as well, considering easyrider put a morini with similar power output on his: http://motorbicycling.com/f47/ezrs-full-suspension-summer-project-1286.html

I did some more researh and found that I could just use a Rohloff speedhub with a BMX chain, which could handle the torque (M55 use it on their high powered e-bike: M55 - Electric bikes with a torque figure of 50 nm compared to my 7 nm) but it would be way too expensive.

 

[Ibedayank]

Web moped2.org

Washington Moped Laws
Minimum age to ride a moped: sixteen.

Moped definition

"Moped" means a motorized device designed to travel with not more than three sixteen-inch or larger diameter wheels in contact with the ground, having fully operative pedals for propulsion by human power, and an electric or a liquid fuel motor with a cylinder displacement not exceeding fifty cubic centimeters which produces no more than two gross brake horsepower (developed by a prime mover, as measured by a brake applied to the driving shaft) that is capable of propelling the device at not more than thirty miles per hour on level ground.

The Washington state patrol may approve of and define as a "moped" a vehicle which fails to meet these specific criteria, but which is essentially similar in performance and application to motorized devices which do meet these specific criteria.

 

[Nipash]

Yes, I've read that definition on the Washington State Patrol website. Trouble is, I just feel like i've been getting the run around by the gov't because everyone outside the DMV (i.e. the Washington State Patrol) say just get it registered as a moped. But I tried to get one of the mb's i'd built registered as a moped but they said they could not do it because it needed to have a VIN and the vehicle be deemed "made to be motorized" by a major manufacturer with a vehicle manufacturers license. So they said go to the Washington State Patrol for an inspection. Which said the could not inspect it because it is a moped, and I should get it registered as one. And so the loop continues. So basically that's why I'm going for a simple design with an automatic transmission and low levels of noise, so wherever I go there will be as little attention as possible given to me.
Also, according to wikipedia: Roller chain - Wikipedia, the free encyclopedia the maximum working load defined by ANSI for a bicycle chain (size 40) is 810 lbs. So, I guess if I hook an engine up to it with 5.16 ft/lbs of torque there is no way it could break? Also, according to this forum thread: Maximum Human Torque [Archive] - Bike Forums pro cyclists produce on average 80 ft/lbs of torque but over a very narrow rev range (which is why the horsepower figure is so low). So, according to this, an engine would actually be more gentle on the drivetrain than a human? Then again I do not have much experience with this and there is the question of the speed and vibrations produced by the engine.

 

[bowljoman]

I use KMC-510 and its friggin' nice. It fits 410 and 40 sprockets.

What I have experienced...
You have three options for alternative gas transportation.

1) To ride like you own the road, all streets up to 35 MPH:
Bicycle as moped, and YOU ARE the manufacturer. The vin is the frame serial number + a bunch of zeros to make it long enough. You need a moped plate, and if the motor is more than 50CC you need a motorcycle endorsement. If you are lucky, you wont need DOT rims and rubber. If they look at everything, you'll also need mirrors on both sides, tach, speedo, turn signals, headlight, tail light, and plate illumination.

2) To ride on all side streets at or under 25 MPH with risk of ticket:
Play ignorant, and have helmet,lights, etc, and LIE LIE LIE about the engine size being under 50CC. Show that it is peddle assist. Cross your fingers that they are cool..

3) To ride Legally on all side streets at or under 25 MPH with NO risk of ticket:
Follow laws for being a Motorized foot scooter. This is where I am with a recumbent build. As long as I hide engine size, shifter, and top speed, Im legal

Always remember that the spirit of the law for Washington is not to impound, but enable new forms of transportation. The law allows impounding only after multiple grooss offenses, or an offense by a minor until the parent picks up the vehicle. The maximum penalty is 125$. Motorized foot scooters are allowed the same access to state highways as bicycles.