for a new project im thinking of starting soon, i want to set the bones up as show in the attached diagram. They will be rosejointed, and i guess the two legs will have to be joined by rod ends too. The reason i want to do this is its easier to mount the bones to the chassis, and it gives more adjustability (castor, specifically).

Does anyone have any experience or pictures of this done please? I need inspiration.

'twill also have pushrod suspension and an antiroll bar

[Edited on 23/8/05 by JoelP]

Main snag is the axis of rotation of the inner ends of the wishbones should be on the same line and parallel to the centre line of the car or the castor and wheelbase vary with each bounce. Bit too adjustable.
Rescued attachment wish.jpg

it'll be quite stiff, plus the extra length of the 'trailing' arm minimizes the amount it pulls the other arm off course.

Its called a compression strut and has been used on a few road cars as well as race cars. As usual I can't find any decent photos but here's one on a Datsun Z240.



Formula 1 used a similar wishbone set up for years, but on the top rear link. Look at almost any car from the DFV era and you'll see the radius arm.

Joel if you are going for bones that are a bit different have you thought about putting some anti dive into the front I have about 5 degrees in my build but its still early days so I do not yet know how effective it will be

doing this, you could make adjustable antidive by adding in a few brackets for the rearmost legs good point.

My main problem is how to prevent the arms twisting, and how to mount the ball joints.

Here is a better picture.


There should not be any twisting moment on the wishbones.

Hi Joel,

How about finishing the one car!

Then using those 50 odd motorbike engines for an aeroplane,

And then opening a Ford Sierra Spares warehouse,

Then building another car!

Pat

Looking at tha diagram it would appear you won't be going round tight corners!

quote:

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Originally posted by Kissy
Looking at tha diagram it would appear you won't be going round tight corners!

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sorry about the huge pic, but I have this setup on the front of the grasser.

Yes, it does slightly compromise steering lock............but.......I still have about 75 degrees!!!!!!

see my avatar........if you need more lock than that then something is wrong.



grasser 3

useful pic that one, cheers

Looking through your archive, is the lower bone a normal one? is it just the upper one thats in two pieces?
What hubs does it use? Im thinking of using cortinas to start with so that i can upgrade to the raceleda ones once finished.

Do you every adjust the upper bone to change castor, or have you done it this way primarily to send loads into the chassis better?

cheers

I was going to have both wishbones adjustable, but mounting the shocker made that tricky on the lower one so that one is non-adjustable. It is still the same design (i.e. long compression leg and short transverse leg) but is one-piece.

Yes, I use the compression link on the top 'bone to set the castor, in fact the castor is "skewed" to assist the car on right hand turns (autograss is r/h oval).

You can easily adjust castor and camber with this setup, though as has been mentioned, it is also easy to set everything wrong (only took me two meetings to get it handling right though, about 10 mins racing, no practice allowed in grassing)

The uprights are cortina, and the balljoints are transit ones (same as locost upper one) used top and bottom both sides (car is quite light, you can pick it up at the front!!)

The steering arms are modded to get quicker steering and more ackerman but otherwise std cortina uprights.

The rose joints are all 5/8"x5/8" cheapo "Carborace" ones from Rally Design.

The compression links are mounted on single shear stubs. These are EN8 bright bar, turned to a "top hat" type fitting, then drilled and tapped M8 in the outer end for a retaining bolt and washer to hold on and clamp the joint, and then the inner end of the fittings were accurately sawn off at the correct angle to weld onto the chassis rails. Didn't like the single shear idea but they have proved excellent. Have hit things hard enough to knock chunks out of the alloys in the pic and the mounts are fine.

i noticed the single shear bolts, but didnt question it cos i guess the proofs in the pudding!

oh yeah, is the lower taper naturally the same as the transit rod end, or does it need reaming? cheers

[Edited on 24/8/05 by JoelP]

I'm sure the tapers are the same top and bottom, but I'll double check the ones on the 7 when I get home, I know I haven't modded those!!

The bolts are not in single shear on the compression struts, the welded on stubs are, the bolts just retain and stop the joints rotating.

see crap drawing below that I just did in paint, the red blobs are weld and the threads on the rose joint are pointing the wrong way but you get the idea!



susp1

I'm sure you've already thought about this but just in case you haven't (we all overlook the obvious till it's too late) looking at the diagrams it doesn't look like you are leaving yourself much room for the wheel under steering.

It looks fine when you turn right but when you turn left aren't you going to foul the trailing suspension arm?

Here is one Eric Broadley preared earlier :-)

62 Lola F1 car
This Layout was used by a few chassis designer in thr 60s and 70s
The only major downside of this layout is the strut part of the wishbone can punch back into the cockpit as a resut of an impact -- err quite nasty !

[Edited on 24/8/05 by britishtrident]
Rescued attachment Flola.jpg

quote:

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Originally posted by DorsetStrider
I'm sure you've already thought about this but just in case you haven't (we all overlook the obvious till it's too late) looking at the diagrams it doesn't look like you are leaving yourself much room for the wheel under steering.

It looks fine when you turn right but when you turn left aren't you going to foul the trailing suspension arm?

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quote:

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Originally posted by britishtrident
Here is one Eric Broadley preared earlier :-)

62 Lola F1 car
This Layout was used by a few chassis designer in thr 60s and 70s
The only major downside of this layout is the strut part of the wishbone can punch back into the cockpit as a resut of an impact -- err quite nasty !

[Edited on 24/8/05 by britishtrident]

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Race wishbones nowadays have a cross piece in to prevent them going through the cockpit sides.
Rescued attachment Flola.jpg

The original Sylva lower wishbone setup on the Fury used Mk II Escort Track Control Arms with Compression strut....

http://www.cantcatchme.net/galleries/2003/stoneleigh.html

saw this today, beautiful and working well on a racecar. Imagine it with a pushrod.
Rescued attachment bonessmall.jpg

well as long as you dont need to do any three point turns you'll be grand!

Im guessing this is trackday only stuff your planning though!

See NS Dev's post. I've seen him move his grasser onto the trailer - its got plenty of lock. Its all relative. Put your road car on full lock and see what angle you've got. Design your car to have something similar to that and i bet you still get a decent amount of rear-ward-ability with the rear wishbone.

its basically a compromise, i believe it will be easy to set it up with enough lock and still get away with a good angle on the rear bone leg. Im thinking of using 25x2mm for the front part, and 19x2mm for the rear bit, as the shocker doesnt press on it directly. It will also use a transit draglink bottom and top, i think it will easily be strong enough as its a bec dedicated chassis. People have used astra balljoints in the past, which arent designed for that loading either. Still waiting for someone to confirm that cortina/raceleda hubs have the same taper top and bottom!