Board logo

Shock Absorber Travel Question
woodsy144 - 19/8/19 at 11:02 PM


I am looking at building a mid engined bike powered vehicle, so light weight. I am HOPING 300kg....... (slightly optimistic but have to aim high)
I am currently thinking suspension travel to be around 60mm ( in bump & rebound (120mm total)

During my sourcing travels, I have been very fortunate enough to be given 4 Yamaha R6 shock absorbers. Great light weight units with adjustable damping.
Issue is travel, they have approx 45mm of travel total (before hit bump stop)

So a motion ratio of about 0.375 to 1
Question is, is it worth while creating a bell crank or place them in a position to use these shocks (ie create a motion ratio suitable).
Or is the motion ratio way to small to chase?

coyoteboy - 20/8/19 at 11:59 AM

I'd be wanting to know what the motion ratio and loading was in the normal operation - if you're going from 2:1 to 0.3:1 you might find your damping doesn't have the adjustability you require.

woodsy144 - 20/8/19 at 12:54 PM

this is the shock in its 'natural environment'. Looking at this setup it appears to be a very low motion ratio set up.

SPYDER - 20/8/19 at 07:41 PM

The bike rear wheel will have a similar travel. Make up a crank system as you propose and it should be OK. You may need to change the springs though. The standard spring is probably in the 400-500 lb range. You might be lucky depending on your crank geometry. I have R1 shocks all round on my Phoenix. No crank arrangement but consequently a limited wheel travel which is OK for track use. I fitted different springs. The range of damping adjustment on the R1 shock is huge. Hopefully the R6 shock has a similar range.

MikeRJ - 20/8/19 at 08:23 PM

Note that these monoshock swing arms have a massively rising rate, approaching infinity at the end of the range.