How does this bike suspension work?

[joelwideqvist]

Hi!
I've moved outside my safety zone and picked up a Revell RM Chopper. Should be a fun build but I need some help.

Can someone explain how a suspension like this one works on a 1:1 bike? I have an idea that the swing arm is bolted in the upper rear end of the frame and that it then works like a cradle without any bolts through the lower rear end of the frame...but that's just my guess.

My idea is to scratch build a new suspension as I have to redo the swing arm.

Any help appreciated.





/Joel

[MPWR]

Bikes are made with and without rear suspension- soft tails and hard tails. Hard tails are simpler and lighter, and are often seen on choppers, as they are easier to fabricate. I believe RM's choppers are all hard tails.

The two bits there look a bit like dampers, and that they might work as part of a bellcrank system (similar to what is seen in F1 cars and many GP and street bikes). However, the rear frame looks like a solid welded one piece, with no separate swing arm.

[ales]

Joel,

That could be a representation of a rigid frame (no movable rear suspension) or the one pivoted in the middle (link)

Edit: now that Andy has pointed out the shocks I'm pretty much convinced that it's the hidden shock frame.

[CrateCruncher]

It's a late-model Harley Davidson suspension. It reminds me of a Tamiya 1/6 Fat Boy I built. Fortunately, I saved the instructions. The pivot point needs to be in the same plane as the drive cog and rear axle to prevent the belt from stretching. Here's how Tamiya did it:

[its not unusual]

its a softail frame not rigid.

http://www.cscycleservice.com/softai...80%9D%20Tubing


Aleks

[joelwideqvist]

Ok, thanks for your quick replies, and for the links as I see I have to do some studying to get this right...
/Joel

[joelwideqvist]

The forces working on such a swing and taking into account the mounting place of the suspension parts must imply that this is a progressive damper, right?

[Twowheelsrule]

Originally Posted by joelwideqvist

The forces working on such a swing and taking into account the mounting place of the suspension parts must imply that this is a progressive damper, right?

It is only a little progressive simply because the swing arm doesn't travel very far. In case you don't know the damper gets longer when the bike hits a bump which is opposite compared to a motogp style suspension.


Mark