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Author Topic: Mk2 golf VW Custom Suspension Uprights hubs Motorsport design  (Read 4609 times)

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Offline Tonyb

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Re: Custom Suspension Uprights
« Reply #15 on: November 10, 2013, 05:33:03 pm »
Interesting subject. I'm in the process of developing a new front suspension set up for the Tatty Golf for when it has the sequential box fitted. I was planning on using one of the available alloy VW hubs with the push in type of damper mounts. This is the way race cars seem to be going. All the adjustment will be in the upper mount and the rose jointed wishbone at the bottom.

Obviously the geometry is critical to this and any std alloy hubs need modifying. First thing is to bolt it on and decide strut sizes etc. I'm hoping to get an off the shelf solution to the dampers from one of the special purpose saloon race cars. Might be easier to machine something up to take one of the composite type of bolt in wheel bearings?

I need to decide the parameters that I'll be working to so this thread seems ideal to establish some baselines. The one thing I notice is that you seem to be comparing back to original suspension geometry Tom. Surely the original geometry is designed and made to suit a very different brief to that of a track/race car?

What works for a universal car that has to do shopping/winter driving/caravan towing etc. etc. is going to be quite a way from what will be wanted on a track/race car I'd have thought?

I'd have though it better to decide what geometry a FWD race/track car uses and then work back from that to make the Golf suspension fit the brief.

Would be good if anyone has some 'proper' FWD geometry info from VWMS or Seat Sport from either a track or Tarmac rally car and compare that to the std VW geometry and see what is different and what is similar.

Offline RobT

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Re: Custom Suspension Uprights
« Reply #16 on: November 10, 2013, 05:39:31 pm »
Pretty much everything is available for the leon racecars, got the specs somewhere.......
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Offline Smudge

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Re: Custom Suspension Uprights
« Reply #17 on: November 10, 2013, 07:32:17 pm »
Hi Tony

I completly agree with you about replicating std geo for a race car. I want to use the best geometry I can for the suspension, working out what this maybe is difficult, it always seems there are positives and negatives and driver feel to each which ever way you go. As for the Roll Centre, the only data I have found is that for saloons above ground at 15-30% of the CofG, but the substance of these figures is not substantiated.

Real data from works cars would be like gold.

I think the front RC is the only one I have linked back to factory, but I am more than keen for others to give ideas and discussion about them. Very much an open brain storming thread here. I imagine after I build my first set of hubs I will change and develop them more than once! - seems to always be the way.

The settings I'm am looking at achieving with my upright design are:

Caster: 9 degrees
Camber: 2.5 degrees (but adjustable from 2-3.5)
KPI: around 12 degrees (would like it to be closer to the caster 9 degrees)
Scrub: close to zero
Front roll centre: ATM 80mm above ground
« Last Edit: November 10, 2013, 07:34:40 pm by Smudge »
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Offline Tonyb

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Re: Custom Suspension Uprights
« Reply #18 on: November 10, 2013, 08:45:19 pm »
Yes, I have been looking at the Supercopa racers Rob as they are probably the best base, short of full works spec but far removed from 'normal'.

I think much of the spec might be on Seatsport web site. Handy if you have the info Rob.

I was discussing this yesterday Tom and somewhere over 9 degrees seemed to be a minimum. Have to be careful with the rules for my sport but want to move the top mounts and  get some proper castor.

Haven't considered the other figs with the exception of camber. I'm intending running crossply hill climb tyres so camber will be close to zero, maybe 1 degree negative. Probably run 9j rims so so will have to play with a few things.

Also going to run an arb on the front, that I don't now so I'll have to look in to spring rates as well.

Offline Smudge

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Re: Custom Suspension Uprights
« Reply #19 on: November 10, 2013, 09:47:18 pm »
I have had a copy of the supercopa for a few years, it has some very interesting and useful data. But, it does not mention the roll centre heights at all  :(

I'm with you on the subject of caster, more the merrier, but you are limited by the turret position and the wheel, to wheel arch room. The only way to get more is to, as you say, move the turret but this does not always fit in with regs and is the easier way of achieving more caster. Running larger track you will have to think hard to keep the KPI to a sensible angle, you may have to move the turret further out.

Some useful pages below from the supercopa.





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Offline Smudge

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Re: Custom Suspension Uprights
« Reply #20 on: November 10, 2013, 10:21:55 pm »
Yep, 16mm above ground he said. Btcc engineer and lecturer in automotive engineering. Rear is 40mm.

I guess this is effected largely by wheel and tyre sizes. The rear seems low, any idea how this was measured?
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Offline Smudge

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Re: Custom Suspension Uprights
« Reply #21 on: November 10, 2013, 11:20:47 pm »
Just stumbled over this document, lots of info in there about torsion beams for you all.

http://c315221.r21.cf1.rackcdn.com/ULSAS_EngRpt_Twistbeam_Design.pdf
See my MK2 Golf 16v in the members section.


Offline Smudge

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Re: Custom Suspension Uprights
« Reply #22 on: November 11, 2013, 10:59:52 pm »
Ok, found out how to measure the role centre for the rear torsion beam, I will have to take some measurements when it's dry and in the hours of day light, who knows when this might next be  ??? Hopefully the weekend. Anyway here is the process:

Quote
Now, where is the roll center in a twist beam system?  It is not at the height of whatever provides lateral location, except in the case where the twist beam is exactly in the axle plane (the vertical, transverse plane containing the wheel axis).
 
To locate the roll center on a drawing board, here's what we do: in a side view of the system, draw a vertical line from the center of the trailing arm pivot down to the ground.  Insert or establish a point where this line meets the ground.  We're going to call this point A.
 
Draw another vertical line from the wheel center to the ground, and also upward a ways from the wheel center.  This represents the axle plane, in edge view.
 
Draw a third vertical line through the twist axis of the beam or deDion tube.  This represents the twist axis plane (the vertical, transverse plane containing the twist axis), in edge view.
 
Now find the lateral force coupling point between the twist beam assembly and the sprung structure.  Note that this is usually not the roll center, but it is a definable point.  In a VW Rabbit/Golf rear suspension, it is the trailing arm pivot.  In the Rover system, it is the diff axis, or more precisely the inboard U-joint center.  In the Mercedes W125 system, it is the center of the roller.  Draw a horizontal line from this coupling point to the axle plane.  Insert a point at that intercept.  We're going to call this point B.
 
Draw a line passing through points A and B, long enough so that it passes through the twist axis plane.  Find the intersection of this line and the twist axis plane, and insert or define a point there.  We're going to call this point C.
 
The height of point C is the roll center height.  In the Mercedes or the Rover system, point C will be above point B.  In the VW system, point C will be below point B.



Taken from the link below.

http://www.auto-ware.com/ortiz/ChassisNewsletter--October2006.htm
See my MK2 Golf 16v in the members section.


Offline JMR

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Re: Custom Suspension Uprights
« Reply #23 on: November 12, 2013, 12:48:48 am »
Great find Tom!

Offline RobT

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Re: Custom Suspension Uprights
« Reply #24 on: November 12, 2013, 08:10:13 am »
Heres the drawing I did last year when I was considering this - my mistake - 4" not 40mm, (points A/B/C shown) - went to look for it when you raised the topic again

This is with an ibiza beam which is shorter in the arms than a golf beam, and 3.8" assumes the beam is horizontal, which mine is not quite, it slopes up a touch, hence the note approx 4.0" RC

Initial sketch



Scale drawing (albeit not as nice as Dave's creations)  ;D

« Last Edit: November 12, 2013, 08:17:07 am by RobT »
2008 Audi A6 2.0TDI S-Line
2004 Audi A4 Avant 1.8T Quattro S-Line
1996 Seat Ibiza 16V F1.5 Race car

Offline Smudge

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Re: Custom Suspension Uprights
« Reply #25 on: November 12, 2013, 08:31:31 am »
Because you work in inches for the rear does that mean the front role centre is 1.6" or 40mm?

Great sketches, I will see if I can pop them into CAD for you if you like?
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Offline RobT

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Re: Custom Suspension Uprights
« Reply #26 on: November 12, 2013, 08:36:43 am »
Fill y boots bud. Cad has to be better than my scribble. It would be nice to know rc's at different angles of beam/ as the suspension moves.

Checked front rc notes....that was 16mm he said. Which i agree doesnt sound right the way we are thinking about them, but the guy should know his onions.....maybe there is something not being understood. I will see if i can get hold of him again.
2008 Audi A6 2.0TDI S-Line
2004 Audi A4 Avant 1.8T Quattro S-Line
1996 Seat Ibiza 16V F1.5 Race car

Offline Smudge

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Re: Custom Suspension Uprights
« Reply #27 on: November 12, 2013, 08:58:43 am »
Fill y boots bud. Cad has to be better than my scribble. It would be nice to know rc's at different angles of beam/ as the suspension moves.

Checked front rc notes....that was 16mm he said. Which i agree doesnt sound right the way we are thinking about them, but the guy should know his onions.....maybe there is something not being understood. I will see if i can get hold of him again.

It could be right, but it does seem low. However, you run larger wheels? I could see how running larger wheels on the mk2 drawing effects RC, (I know it's not the same as your setup but it could give us an idea of how the wheel sizes effect it.)
See my MK2 Golf 16v in the members section.


Offline RobT

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Re: Custom Suspension Uprights
« Reply #28 on: November 12, 2013, 09:07:27 am »
Yep. 17x8, about et10/11 i think.....
2008 Audi A6 2.0TDI S-Line
2004 Audi A4 Avant 1.8T Quattro S-Line
1996 Seat Ibiza 16V F1.5 Race car

Offline Smudge

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Re: Custom Suspension Uprights
« Reply #29 on: November 12, 2013, 09:38:59 am »
See my MK2 Golf 16v in the members section.


 

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