- chain pulling the rear hub towards the idler
- reaction force of tyre on the road
- chain deflection force on the idler
With HP Velotechnic's "no-squat" rear suspension design these forces produce the following reactions:
- chain line constrained to always pass above the pivot point, lifting the rear hub to bring it nearer the idler
- tyre reaction force lifting the rear hub
- chain deflection force lifting the rear of the trike, assuming the idler is behind the centre of mass of trike and rider
This is why I find it hard to believe that HPV rear suspension is particularly efficient. Of course the forces are changing all the time with pedaling and suspension response.