scootz
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| posted on 20/2/13 at 11:57 AM |
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Single Seater Ride Heights
The normal ride height on a single seater is 40mm. Not much use on our roads. 
I can get another 20mm ride height through choosing the right tyres. Alas, 60mm is still a little short of where I want to be.
So, my question to anyone who has dabbled with modern single-seaters is... how much (sensible) height adjustment would there be in the front end of a
monoshock equipped car? Could I sneak another 20mm without completely destroying the handlng?
It's Evolution Baby!
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ceebmoj
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| posted on 20/2/13 at 12:18 PM |
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Is this for the trike?
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scootz
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| posted on 20/2/13 at 12:23 PM |
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Yup
It's Evolution Baby!
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designer
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| posted on 20/2/13 at 12:47 PM |
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For a monoshock the easiest way is to lengthen the push/pull rods.
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Benzo
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| posted on 20/2/13 at 12:55 PM |
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quote:
Originally posted by designer
For a monoshock the easiest way is to lengthen the push/pull rods.
when we had our Judd Pilbeam with inboard suspension, all height adjustments where done through the pushrods, not the platforms.
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Talon Motorsport
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| posted on 20/2/13 at 01:06 PM |
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If you can not fit landrover tyres and you come to the point that the suspension angles are getting silly why not make some Z shaped wishbones? Then
you can get as much ride as you want then with in reason.
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scootz
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| posted on 20/2/13 at 01:06 PM |
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Cheers guys. That makes sense!
It's Evolution Baby!
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russbost
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| posted on 20/2/13 at 01:25 PM |
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You can obviously gain some movement by lengthening the pushrods, but you may find that the suspension joints themselves run out of movement - this
was certainly the problem I had when doing something similar, finished up having to modify wishbones to ensure everything worked at sensible angles
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Theshed
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| posted on 20/2/13 at 03:16 PM |
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Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by
changing tyres. Extending the pushrods to give an extra 20mm is a big adjustment and the wishbones would be on a very different arc.
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scootz
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| posted on 20/2/13 at 04:10 PM |
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quote:
Originally posted by Theshed
Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by
changing tyres.
Surely using larger diameter tyres wouldn't affect the geometry???
It's Evolution Baby!
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v8kid
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| posted on 20/2/13 at 05:02 PM |
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quote:
Originally posted by scootz
quote:
Originally posted by Theshed
Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by
changing tyres.
Surely using larger diameter tyres wouldn't affect the geometry???
Think it would.
Think of the geometry when you construct the roll center diagram. The point where they intersect the road has just been shifted 20mm downwards.
Anyhow you have altered the balance by converting to a trike and I presume you will be upping the front roll stiffness since there will be no help
from the rear so it should not move much anyhow. 
Was it Chapman who said you could make any suspension geometry great as long as the springs were so stiff it never moved?
Cheers!
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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Sam_68
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| posted on 20/2/13 at 05:03 PM |
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quote:
Originally posted by scootz
quote:
Originally posted by Theshed
Unless you move the pick up points any alteration in ride height will alter the geometry. I discovered that when I tried to gain ride height by
changing tyres.
Surely using larger diameter tyres wouldn't affect the geometry???
It will potentially alter the roll centres (the RC is defined by projecting lines from the wishbones until they intersect, then drawing a line back to
the tyre contact patch... with bigger tyres, the wishbone angles remain the same, but the tyre contact patch moves downward relative to the
wishbones).
It will also change the king pin offset (scrub radius) and caster trail dimension on the ground.
Since you're also going to be using completely different tyre construction, weight distribution and dynamics (3 vs. 4 wheels for a start!) from
those the geometry was designed for, these may or may not be catastrophic. 
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Sam_68
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| posted on 20/2/13 at 05:06 PM |
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quote:
Originally posted by v8kid
Was it Chapman who said you could make any suspension geometry great as long as the springs were so stiff it never moved?
He's OK on that score, at least - it's a monoshock set-up, so the total roll compliance will be measured in millimetres! 
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phelpsa
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| posted on 20/2/13 at 05:08 PM |
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The problem will be that single seater suspension is designed to operate within very small adjustment ranges. So you'll find problems like
massively non-linear motion ratios and binding bearings start to come into play.
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Sam_68
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| posted on 20/2/13 at 05:25 PM |
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quote:
Originally posted by phelpsa
The problem will be that single seater suspension is designed to operate within very small adjustment ranges. So you'll find problems like
massively non-linear motion ratios and binding bearings start to come into play.
As I understand it, the suggestion at the moment is simply to increase the rolling diameter of the tyres, so the motion ratios should not be
affected?
You will certainly need to ensure that the total range of suspension movement is not substantially increased, otherwise, yes, not only will the
motion ratios move out of their designed envelope, but you'll almost certainly find that the suspension will run out of movement somewhere or
other and bind. Joking aside, you'll find that the Dallara monoshock has very limited roll compliance, whatever you do. I assume you have a copy
of the Dallara manual for the car, which gives the damper open and closed dimensions (which in turn control maximum bump and droop movement, of
course)?
Slightly different problem, but I know from the bitter experience of being asked to design an all-pushrod actuated suspension for a road car because
it was 'sexy' that what works well for a single seater with a total suspension movement of 30mm doesn't work out quite so easily for
a road car with a total range of 120mm movement, particularly if you want to maintain sensible motion ratios on your dampers!
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Sam_68
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| posted on 20/2/13 at 05:43 PM |
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quote:
Originally posted by Benzo
quote:
Originally posted by designer
For a monoshock the easiest way is to lengthen the push/pull rods.
when we had our Judd Pilbeam with inboard suspension, all height adjustments where done through the pushrods, not the platforms.
Another quirk of monoshock suspension is that standard practice is to adjust the ride height on the spring platform, not the pushrods, the
reasons for which will hopefully be obvious - you need to keep the pushrod lengths exactly equal, otherwise the roll shuttle will be off-centre and
you'll end up with asymmetric roll compliance.
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scootz
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| posted on 20/2/13 at 06:36 PM |
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Thanks for the replies.
I think I've said it elsewhere... I'm not looking for razor sharp handling. I just want the trike to look right, have Gucci components and
to not try and kill me on every bend!
Just an interesting concepty-typy-thingy!
It's Evolution Baby!
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scootz
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| posted on 20/2/13 at 06:37 PM |
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PS - yes, I downloaded a copy of the Dallara manual.
It's Evolution Baby!
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phelpsa
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| posted on 20/2/13 at 08:37 PM |
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quote:
Originally posted by Sam_68
quote:
Originally posted by phelpsa
The problem will be that single seater suspension is designed to operate within very small adjustment ranges. So you'll find problems like
massively non-linear motion ratios and binding bearings start to come into play.
As I understand it, the suggestion at the moment is simply to increase the rolling diameter of the tyres, so the motion ratios should not be
affected?
I believe scootz is asking how to gain more, even after changing the tyre diameter.
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