View Full Version : Chain driven trailing arm

01-18-2007, 12:40 PM
Just another idea I am kicking around. Drive shafts do limit the amount of suspension travel you can get on a mini buggy so I am thinking of a chain driven trailing arm. The thing that may cause problems is the torque reaction on the trailing arm.
About 15 years ago I built a buggy very much on a budget using a yamaha 650 twin to power it and for simplicity I went for a quad type swinging arm and axle with chain and sprockets. when it came to the swinging arm pivot point I thought the best place would be on the same center line as the front drive sprocket so thats what I did. When it was finished I took it out and as soon as I pulled off the rear end lifted up in the air (taking up the sag in the rear suspension) and when I hit a bump whilst on the power it was like the rear end was ridgid but if I put the clutch in and coasted the rear suspension worked fine. I am not sure what happened on a trailing throttle but I think it pulled the rear end down a bit.
I had a good look at it and thought the swinging arm may be at too much of an angle and the rear wheels were trying to go under the buggy under acceleration so I raised the upper shock mount *so that the swinging arm was almost horizontal but it made no differance. It was torque reaction that was causing the problem and I had learned the hard way.
I now see why the front sprocket on a motorcross bike or a quad is just in front of the swing arm pivot for a reason. but what is the calculation method for the pivot point, I would of thought you need to take in to account swing arm length and sprocket sizes.
I know some production road race bikes like ZX 7RR have adjustable swing arm point, but only a few millimetres in any direction and can make a big difference to the bikes handling.
ATK made a motocross bike which had an arrangement mounted by the swing arm pivot point and the chain looped around it I think it was called" torque" something, anyone know what that was for, something to do with torque reaction I would of thought.
With a chain driven trailing arm if I keep the chain close to the tyre it would be good in deep ruts which we get a lot of where I ride

01-18-2007, 03:35 PM
Maybe it had more to do with eliminating the need for a chain tensioner.
With the sprocket being on the pivot, the length to the rear sproket would remain constant.
Whereas that the distance ( from engine sprocket to rear wheel sprocket) would vary with the movement of the swingarm through its travel in what would be seen as the "normal" configuration.

The chain in a swingarm/trailing arm is used in the Tomcar,

see previous post

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01-18-2007, 03:44 PM
Its been talked about here 10 times already, nothing new..

01-18-2007, 05:01 PM
Thanks Bug,

01-18-2007, 05:52 PM
If the center of the sprocket is in line with the pivot, there will be no effect on suspension, besides that it will make it a little tighter. When the sprocket is above the pivot, it will lift the rear whels up, or try to, resulting in the rear sinking. I have put a shaft in a larger tube, bure it out for some bearings, and capped it for some of my early go karts.

01-18-2007, 06:04 PM
BTW, don't nother with those loop things. They are called AMP links. I've been riding atv's for a while, and no one has said anything positive for the price.