rear suspension ?

[retromike3]

I was thinking of setting up my new ride with a rear suspension. Does anybody know how you could set it up so you could keep the rear end from diving when you hit the gas? I know it can be done but I am a bit confused on how you can isolate the drive train.

thanks, Mike.

 

[Ludwig II]

You could get clever and try a prallelogram swing arm.

http://farm4.static.flickr.com/3660/3490171732_2bc6c4cedf_o.jpg

More simply, a higher rated spring and a proper damper unit will help a bit.

 

[Ludwig II]

Is the engine to be on the frame? Try getting the top chain run to go as close to the swing arm pivot point as you can, that's how motorcycles do it.

 

[Deleted member 12676]

The pivot point for the swingarm would need to be on level with the tensed half of the chain. When it is lower then the suspension is compressed when gassing it, and when it is higher then the opposite happens.

 

[professor]

Mike- there is no problem with the suspension diving.
The problem (as pointed out above) is the keep the drive chain or belt from either slacking or tensioning with the swing of the rear arm.
I am using full suspension (a wonderful thing) on bike 2 doing what they said.

I remember seeing a pic where the builder raised the pivot point up in line with the sprocket output of the engine- motorcycle style. He ran the pedal sprocket down in the normal place with a chain up to a jackshaft then to the pedal drive. Great idea.

 

[wheelbender6]

Fix it NASCAR style. Insert a spring rubber in the shock (spacer).

 

[motorbikemike45]

This thread is confusing me. This IS the rack mounted drive train section, so exactly why is their any question about the engine being frame mounted? In a rack mounted engine the engine and drive system most often pivot up and down with the rear wheel if there is a rear suspension on the bike, or it would need to have a large chain/belt tensioner to account for the differential motion between the bike frame cantilever rack mounted engine and the wheel going up and down. Any 'squat' caused by the drive chain/belt pulling the axle upwards during acceleration is sort of the nature of the beast if the engine is mounted on a rack rigidly attached to the non-suspended part of the bike frame above the suspended rear axle. To eliminate squat the best solution is to mount the engine on a rack that is attached to the seat post via a pivot and braced to the rear axle via pivots. The braces hold the engine-axle a constant distance apart, thus eliminating accelleration caused squat other than the normal weight transfer squat inherent on any suspended bike. That would allow the engine to move up and down with the rear wheel, maintaining constant tension and distance/length on the chain/belt, and not pulling the rear axle up during acceleration. Drive could be routed to a pivot point at the pivot point of the rear suspension via idler sprockets/pulleys or a jack shaft, but the complexity and weight of such a system puts me off. When it comes to motored bikes, I go with the "keep it simple, stupid" school of design.