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r500 suspension design
Dangle_kt - 31/8/09 at 08:34 AM

Was having a rummage through a few pics, and found this of the r500 front suspension:

Now what are your thoughts on the design of the top and bottom wishbones?

it makes alot of the wishbones we run look positivly agricultural don't you think? now i know caterham know what they are doing, so are our wishbones seriously over engineered, or just very basic in engineering terms vs theres?

Also they use outboard shocks on what is meant to be their best caterham - so is all the fuss over inboard suspension just for pub banter?


Guinness - 31/8/09 at 08:43 AM

Yes, most locost wishbones are positively agricultural compared to a Caterham set.

They also have additional bracing across the bottom bone and the upper bones are a different design to my MK ones.

The outboard shocks, are very nice outboard shocks

I think they've had years and years of development and probably use a better grade of material to save weight / size?

Mike


RichardK - 31/8/09 at 08:43 AM

Just wondering if they are for a race car version, ie track not road with pot holes etc

Rich


rusty nuts - 31/8/09 at 08:43 AM

The shock absorber is also upside down but their car is supposed to be the benchmark against which all others are compared


Dangle_kt - 31/8/09 at 08:52 AM

quote:
Originally posted by rusty nuts
The shock absorber is also upside down but their car is supposed to be the benchmark against which all others are compared


they are designed to run that way I've just read...


mackei23b - 31/8/09 at 08:53 AM

This is to reduce unsprung weight.


quote:
Originally posted by rusty nuts
The shock absorber is also upside down but their car is supposed to be the benchmark against which all others are compared


scootz - 31/8/09 at 09:52 AM

quote:
Originally posted by rusty nuts
The shock absorber is also upside down but their car is supposed to be the benchmark against which all others are compared


It's 'de riguer' these days!

As for inboard??? Caterham still subscribe to the Chapman philosophy of less is more, 'simplify and lighten'.


Richard Quinn - 31/8/09 at 09:54 AM

Please note that shocks have to be design and built to run upside down. Don't just turn them over to reduce unsprung weight!


Neville Jones - 31/8/09 at 10:06 AM

Protech shocks will run 'upside down' quite happily, if you tell Protech that they will be used that way. The only difference, according to the man who designs the Protech stuff, is that they are careful to fill them up to the top, if they are to be run 'inverted.'

Cheers,
Nev.


Richard Quinn - 31/8/09 at 10:18 AM

They said that about running them on their sides too when we went through a phase of inboard shocks on Autograss front ends. They might work quite happily initially but they weren't happy for long compared to the intended orientation.


mark chandler - 31/8/09 at 10:34 AM

Upside down forks have been on bikes for years.

You can use thinner wishbones if the shock points at the lower ball joint as the bone is no-longer a lever. This is the correct way to do it, 1/3 way in is historic when shocks were not so easy to come by so adapted to suit lengths available cheaply.

Inboard shocks reduce unsprung weight and air resistance, running like this you gain a little more on the unsprung side as no extra rods and levers required, although gain air resistance but its still a brick so not that much affect.

Nothing really special then, just much better quality control applied.


flak monkey - 31/8/09 at 10:44 AM

They are about a good as you can get given the space limitations.

Some other companies would be wise to take a leaf or 2 our of caterhams book.

I think they run nirton shocks (which are about the same price EACH as a fulls et of protechs...) and they will run in any orientation.


prawnabie - 31/8/09 at 11:06 AM

Standard shockers are bilsteins as pictures - nitrons are an upgrade.


PAUL FISHER - 31/8/09 at 12:31 PM

quote:
Originally posted by Dangle_kt
Also they use outboard shocks on what is meant to be their best caterham - so is all the fuss over inboard suspension just for pub banter?

Caterhams top of the range model is the CSR that has inboard suspension


Volvorsport - 31/8/09 at 02:03 PM

i would have run outboard shocks , but mine turned out to be 4" too short , so i went inboard .

the trick is gettig the damper position as close to the BBJ as possible - reducing the bending load on the tube .


Canada EH! - 31/8/09 at 02:43 PM

I was of the opinion that Bilstien only made gas filled shocks


StevieB - 31/8/09 at 03:30 PM

The wishbones on the R500 are the same as the ones you get on any caterham - though they are the wide track option.

My mate runs a '57 series 2, and the wishbones are pretty mush the same on that (the uppers are a little different as they were a single arm with the ARB forming the triangle, though he has the upgrade kit from Caterham to sort this out).


iank - 31/8/09 at 04:09 PM

One thing that I believe contributes a lot to their light weight is the bracing across the body side of the bottom bone.

Chassis are best made from triangles to keep them strong and light it seems obvious that wishbones should be constructed along the same lines.


Liam - 1/9/09 at 10:31 PM

quote:
Originally posted by iank
One thing that I believe contributes a lot to their light weight is the bracing across the body side of the bottom bone.

Chassis are best made from triangles to keep them strong and light it seems obvious that wishbones should be constructed along the same lines.


Locost wishbones are pretty well triangulated by being bolted to the chassis! The only purpose I can see for that tube on the caterham bones is to aid consistent manufacture. Even jigged up, my wishbone ends moved slightly after welding and a tube like this would have prevented this.

Liam


MikeRJ - 2/9/09 at 12:26 PM

quote:
Originally posted by iank
One thing that I believe contributes a lot to their light weight is the bracing across the body side of the bottom bone.


The main improvement that the Caterham design offers is the large reduction in bending moment by having the shock mounted very close to the bottom ball joint. This means the main tubes can be made lighter.


iank - 2/9/09 at 01:51 PM

quote:
Originally posted by Liam
quote:
Originally posted by iank
One thing that I believe contributes a lot to their light weight is the bracing across the body side of the bottom bone.

Chassis are best made from triangles to keep them strong and light it seems obvious that wishbones should be constructed along the same lines.


Locost wishbones are pretty well triangulated by being bolted to the chassis!
...
Liam


Not true I'm afraid and a common misconception.

At least where you have compliant bushes at the chassis end the two wishbone ends can move relative to one another by anything up to a few mm. The upshot is a wishbone without the cross piece needs to be much thicker and stronger in order survive without cracking due to the constant, invisible to the eye, flexing of the arms.

You also need the shock mounted in the right place as MikeRJ rightly says, but if you want them to survive 1000's of miles without wheels falling off you need everything correctly engineered.

I suspect the original design was copied from 'proper' racing cars where you use rose joints which aren't compliant (to anything like the same degree) and wishbones are frequently checked for cracks - where it would be fine, and the design beefed up over the years due to failures.