GP460 Engine On Friction Drive

[DetonatorTuning]

ah......................... no, i'd not say 2.3#'s/ft @ 8,000rpm is particularly weak torque for a 46cc 11:1 2 stroke.

i'm just not getting the explanation across in an understandable way.

what i mean to say is that 26:1 and above this engine revs very fast and easy, because of that, coupled with the fact that the gearing is only going to let you go 32mph @ 11,000rpm, the sound that the 460 will be making, compared to the speed, will make it seem like it must be spinning loose.

steve

 

[5-7HEAVEN]

Not to worry, Detonator. I have all the spindle sizes; it should be no problem to swap rollers to match engine rpm and speed.

Since the engine channel is only .125" thick, extra "meat" might need to be added near the outboard bearing for more support.

The Dominator pipe arrived today. Removing the mounting bracket allows the pipe to bolt on and clear everything. Rewelding the bracket at a 90-degree angle permits the exhaust to be secured to the top of the engine channel.

Extra support struts will be added to triangulate front mounting U-bracket.

Goped tank will bolt onto the outboard side of the engine channel. It needs to be drilled to accommodate its petcock, and a fuel line to a reserve tank.

Happy time teardrop reserve tank will mount on the bike frame's top bar.

So maybe a 1.25" roller at 23:1 gearing might be a better starting point, Steve.

 

[fetor56]

It's going to be interesting to see how loud & powerful this engine is with the pipe & also how much torque......imagine it's going to rev pretty freely.

 

[DetonatorTuning]

much is going to depend on the total weight of bike and rider in full gear, added to the terrain, how much you're willing to pedal away from stops, and the yet unknowable issue of keeping the contact constant without excess downpressure and tire deflection losses cancelling out the power available.

i'd go with the 1.25" as a starting point.

when i was using the GEBE, i could beat traffic across the intersection on the pedals then throw in the gas and STAY ahead. that was at 19:1 and just 11:1 CR.

i gained a noticable amount of midrange torque just replacing my base gasket.

5-7's engine at 13:1 is going to be pretty stout and have the topend advantage of the Dom. pipe. most people are surprised that the Dom. is quieter than the stock muffler.

steve

 

[5-7HEAVEN]

I just bought a 2005 Giant Rincon bike in mint condition for this project. The original wheels will go for my exercise bike at work. New high-performance rims and tires need to be built by Eki Cyclery. It's a bike shop three blocks from my workplace that I give mY business to. If my bike needs work I strip the motorized components before taking it in.

The bike weighs under 33 pounds, which is 12 pounds less than what "The Dragon Lady" started out as, I think. Total motorized bicycle should weigh about 50lbs. That is 41 pounds less than my twin-engined girlie cruiser.

If and when this Giant bike uses two engines, its total weight would be under 70lbs.

That'd be more than 20lbs LESS THAN the "The Dragon Lady. Well, maybe with heavier wheels this bike might weigh 55lbs/single engine or 70lbs/twin engines.

Rider in full gear would weigh about 215lbs.

I PRESUMED that davesmotors would send me the lower compression dome, but it's outa stock. My engine has 15:1 cr which is too high for 91octane gas. I might just order a GP460 with stock compression from this vendor to finish this single engine install. When the 13:1 dome becomes available I might do the twin engine project.

Steve, with my motorized bike I pedal my single-speed bike furiously and throttle both engines simultaneously. Then around 27mph it's all engine.

With 21 speeds I'll probably be pedalling at 30-something mph with the engine.

 

[DetonatorTuning]

the TS heads, domes, reed cages etc. have been "out of stock " for some time.

you might try simpson racing direct but i think he got out of the loose parts end.

gopednation's "for sale" forum would be my first stop, you might be able to make a trade.

when i was running the GEBE i found i never used the gears on my bike. just left it 42T- 17T, .40:1. this low enough to get the jump on traffic and enough to still pedal at about 20mph if i ever wanted too, which wasn't often, 12mph and engine ON.

steve

 

[kerf]

One thing I've noticed on the 460 is the torque curve is flat at low RPM. The engine doesn't get into the power till you get over 6K, where most are topping out. 7 - 8K things start getting interesting. I still believe the friction drive will be the weak link although, I've seen Honda 50's on them.

 

[DetonatorTuning]

me too saddly, but the experiment is interesting and important in that it could lead to some interest in providing an enhanced friction configuration to handle this kind of power.

a stronger more efficient friction system would be good all the way around.

steve

 

[5-7HEAVEN]

Detonator, thanks for tips on finding that compression dome.

kerf, time will tell if the friction drive will be the weakest link. Personally I feel the clutch and roller will withstand the torture. As you've pointed out, this engine produces power at a very high rpm. A low-winding engine produces its torque at the low end. This is where power engagement components would be placed to the test. Parts fail when the clutch grabs and tries to put the power to the ground. However, centrifugal clutches engage gradually, there is less stress to break parts. This is especially if the rider pedals vigorously from a standstart.

It's like doing a rolling start instead of a standing start at the beginning of a dragrace.

It would seem to me that the only weak link would be friction roller and tire engagement. Since this engine is not noted for its massive torque I don't foresee any problems at all.

Disciplined throttle control will be the key to success.

 

[kerf]

I hope all works out. My experience with friction drives, of which I have three, is the tire becomes the weak point. Optimum roller tension, per my experience and David Staton's recommendation, is just enough tension to prevent slippage while holding the bike @ WOT. With the TLE43, this is a good range as it doesn't induce excess drag. You will need a lot more tension to achieve that standing lockup. Don't sell the 460 short.