Friction Drive Drivetrain Clutch Diagram

[Nehmo]

This is a diagram (not to scale) of my next plan of putting a 79cc Predator on a bike.
The idea is that the roller is on a frame that is pivoted at the intermediate shaft (jackshaft); thus, the clutch can engage or disengage without the belt distance changing.
Critique?

[cannonball2]

Thats a similar thing I did on my Schwinn Point Beach remake. Though the belt slack was handled by a spring loaded idler. You asked for critique so here it is: Unless you are doing an inframe or something similar, you are basically defeating the purpose of the FD which is simplicity. I favor direct FDs if you are going to have a rudimentary drive why complicate it? The FDs beauty(in direct mode) is there is no formal trans, ie nothing to break if properly made(I have destroyed one roller out of all I have tried). Also roller changes are fast less than a minutes as I have said earlier. Thats even faster than the variably adjustable pulley I have tried. Now if you threw in a CVT that would be way cool! This is just my opinion. What I love about this hobby is the experimentation, sometimes we build stuff just to see how and if it works. From this perspective more power to ya, get to building and good luck!

[happyvalley]

Originally Posted by cannonball2

the purpose of the FD which is simplicity. I favor direct FDs if you are going to have a rudimentary drive why complicate it? The FDs beauty(in direct mode) is there is no formal trans, ie nothing to break if properly made

Agreed....

[Nehmo]

Originally Posted by cannonball2

...is simplicity. ..

This is simple. I need to improve my diagramming abilities. The way I have it shown makes it look more complicated than it is.

I don't like "direct" drive (if you mean the motor shaft being what holds the roller) because to get an appropriate gear ratio means a roller with a small diameter (perhaps less than 2 inches). This give inadequate engagement to cause the stopped tire to intern kill the engine. Thus, on some occasions, the roller will grind into the tire.

I'll provide an improved diagram of my plan in a bit.

[happyvalley]

Originally Posted by Nehmo

the stopped tire to intern kill the engine. Thus, on some occasions, the roller will grind into the tire.

Not with a centrifugal clutch and pretty sure that's what CB2 was talking about as well.

[cannonball2]

Here is a pictorial explanation of my point. The yellow bike is one of my oldest MBs. I wanted a full suspension traveling bike. FD was the easiest way to make it happen. This bike has gone through such an evolution to make it totally useable for long trips, even trailer pulling. It has a hand clutch like a m/c using a scissiors lift, very easy to use. The only advantage of your system I can see is a larger slower turning roller and the possible use of a cent. clutch. The rest is complexity that adds weight and failure points-belts, bearings etc. If Im gonna be a long way from home(and I have been) it will be with this bike because of its reliability. This bike is very simple just loaded with stuff for traveling like a 5qt fuel tank that makes it look complex. The link is to an inframe Schwinn Preddy build. It uses a similar drive concept and a 3.5" roller. Worked very well. You havent indicated where the engine will be mounted, inframe or rear.http://motorbicycling.com/showpost.p...0&postcount=33

[Nehmo]

Originally Posted by cannonball2

... your system I can see is a larger slower turning roller and the possible use of a cent. clutch. The rest is complexity that adds weight and failure points-belts, bearings etc...

When I use the term FD, I mean Friction Drive without any other qualifications. Consequently, a FD with a centrifugal clutch and one with a movable-roller clutch are two different systems.

I mean this arrangement to be a FD, and the roller will be on a frame (not the bike frame) that is moveable.
The diagram is a top view. The purple pieces form the movable frame that pivots on the outside bearings (swinging above and below the page).

The motor will be mid-frame somewhere I've yet to decide. I haven't even picked a bike yet.

My existing ICEmotor-bike works, and it's what I'm using, but main thing I learned with its construction is that its design needs improvement. So, I want to start afresh.

I'll use the 79cc HF 4 stroke. No centrifugal clutch.

Yes, I certainly want a larger roller (perhaps around 150 mm, 6") because I want sufficient engagement to allow the braked tire to kill the engine as a precautionary feature.
Regarding simplicity, using the roller as both the clutch and a drive member is the mechanical simplification I'm using. (The belt to the roller shaft doesn't need to grow or shrink with a change in position of the roller shaft.) I reckon the additional failure rate of additional bearings will impact only trivially on reliability.
Regarding weight, the idea of using this system of moving the roller is to avoid weight on the clutch. The overall weight seem tolerable to me.