Suspension power losses/savings

For discussions about bikes and equipment.
Samuel D
Posts: 2670
Joined: 8 Mar 2015, 11:05pm
Location: Paris

Re: Suspension power losses/savings

Postby Samuel D » 9 Feb 2019, 2:50pm

atlas_shrugged wrote:This makes me think that any light, frictionless, and simple technique for making a bike glide over the boulders that our UK roads have become will provide a big speed advantage.

You’ve just described fat, supple tyres!

User avatar
squeaker
Posts: 3514
Joined: 12 Jan 2007, 11:43pm
Location: Sussex

Re: Suspension power losses/savings

Postby squeaker » 9 Feb 2019, 5:58pm

atlas_shrugged wrote:I ride a recumbent (~20mph) and in winter a conventional hybrid (~15mph).
Similar wheel sizes / tyre section ? :wink:
"42"

Brucey
Posts: 33848
Joined: 4 Jan 2012, 6:25pm

Re: Suspension power losses/savings

Postby Brucey » 9 Feb 2019, 6:07pm

on a recumbent you can't easily decouple your mass from the bike which makes the bike jiggle around less and makes your body absorb a lot more energy; more suspension losses if you like.

A simple way of reducing these losses (potentially by about half) is simply to decouple the body and its contact points from 'the chassis' in terms of vertical movement. The wheels can then ride the bumps without moving the CoG so much and potentially pedalling is not affected.

The earliest example of this approach is the 'the whippet' of 1888

Image

but -despite the obvious benefits on offer- I don't think this approach has been applied to a recumbent machine..... unless someone knows different?

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
[XAP]Bob
Posts: 16858
Joined: 26 Sep 2008, 4:12pm

Re: Suspension power losses/savings

Postby [XAP]Bob » 9 Feb 2019, 6:18pm

On an upeightbisnt that done by taking more weight on the pedals.. pretty sure some bents have ‘seat’ suspension don’t they?
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

Brucey
Posts: 33848
Joined: 4 Jan 2012, 6:25pm

Re: Suspension power losses/savings

Postby Brucey » 9 Feb 2019, 6:26pm

[XAP]Bob wrote:On an upeightbisnt that done by taking more weight on the pedals.. pretty sure some bents have ‘seat’ suspension don’t they?


there are all kinds of suspension on 'bents, but AFAICT not that particular one, i.e. where all the rider contact points are rigidly coupled within one structure and both wheels are rigidly coupled in another, separate one.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

User avatar
fausto99
Posts: 384
Joined: 19 Sep 2011, 10:06am

Re: Suspension power losses/savings

Postby fausto99 » 9 Feb 2019, 10:16pm

Samuel D wrote:You’ve just described fat, supple tyres!
:shock:
Compare a ride on a narrow tyre-ed Moulton to a Raleigh 20 (shopper or chopper) you'll know what riding through treacle is like. :lol:

User avatar
fausto99
Posts: 384
Joined: 19 Sep 2011, 10:06am

Re: Suspension power losses/savings

Postby fausto99 » 10 Feb 2019, 11:28am

Brucey wrote:However what is less obvious is that just pedalling hard tends to excite a type a) resonance and this tends to absorb energy all the time, even when the suspension has little or no work to do. Hence my earlier comments about needing to pedal in a specific fashion. I have yet to meet a rider that could pedal smoothly at 10/10ths aerobic effort up a draggy climb without bobbing like crazy on a suspension bike, which is why lockouts were invented. On many suspension bikes without lockout, trying to ride out of the saddle is basically a complete waste of time.

+1
precisely why I sold my Moulton AM7 but still have my Moulton Safari. The AM7 space-frame suspension was underdamped (friction dampers) and bobbed all the time when climbing - specially out of the saddle. Much more effort required for climbing (not mitigated enough by the great descending!) The Safari F-frame rubber damped suspension much reduced bobbing I can live with when climbing, while the vibration reduction and descending is still good. Shame about the weight though.

I know the later Moulton NSs had a front suspension lock of sorts but it seemed a bit of a bodge to me considering they are very silly money. I'd have thought a handlebar fine damping control should have been incorporated for the price.