RE: Beef up your TVR's suspension
Monday 8th May 2006
Beef up your suspensionSuspension specialist Powerflex has recently launched a new range of polyurethane bushes for the TVR Griffith and Chimaera.
Beef up your TVR's suspension
Powerflex launches new suspension bushes
Beef up your suspension
Several versions are available, one including special stainless steel sleeve for weld spot on wishbones, and another with a heat shield kit to protect the bush from exhaust heat.
Polyurethane bushes can improve your car's road-holding and chassis performance by controlling unwanted suspension flex. It means the tyres have greater contact with the road at all times, improving safety and performance.
Why it matters
Suspension bushes are some of the most highly stressed components fitted to a motor car. They undergo enormous strains and in the most arduous of conditions with no maintenance or lubrication. Standard rubber bushes are made from a rubber compound containing natural products which deteriorate with age. The material becomes softer and more pliable, resisting the forces placed on it less and less and allowing increasing movement of suspension components, providing less control over the suspension geometry.
Powerflex reckons that technological advances in polyurethane, which is harder than rubber, have overcome the common problem of increased noise. By correctly engineering the polyurethane compound, bushes can be made 25-30 per cent stiffer than new rubber items but with the same noise absorbing properties.
Discussion
To describe a bush as a means of isolating the vehicle from noise and vibration is an enormous oversimplification.
The stiffness of the bushes, in terms of both fore/aft and lateral compliance, is always considered when the suspension is designed. There seems to be little evidence that powerflex bushes are designed with an equivalent amount of engineering care - rather, it's the max power school of thought: Stiffer is always better (btw, it isn't always), becuase racing cars have dead stiff suspension.
The stiffness of the bushes, in terms of both fore/aft and lateral compliance, is always considered when the suspension is designed. There seems to be little evidence that powerflex bushes are designed with an equivalent amount of engineering care - rather, it's the max power school of thought: Stiffer is always better (btw, it isn't always), becuase racing cars have dead stiff suspension.
trackcar said:
.. axe to grind ... ?
no, I don't sell bushes (rubber or otherwise), and don't have anything against Powerflex per se.
I suppose as an (ex) engineer I'm biased against things that don't look like much analysis has gone into them - and this view (regarding hard aftermarket bushes) was backed up by a number of dynamics engineers who used to work for me.
NDT
I'm interested in your point of view. I know a bit about suspension but not much. I do understand that getting it right is what matters, not the max power approach which can easily slow you down unless you are on a Formula 1 track.
Are you saying that the standard fit items for the Griff are right? Or if not, is there a replacement that you think has been properly engineered?
Incidently, I have upgraded the Griff with slightly firmer springs and Gaz shocks which have really improved things, at least from my perspective - I had specific issues with the existing handling that I wanted sorted.
gooner
I'm interested in your point of view. I know a bit about suspension but not much. I do understand that getting it right is what matters, not the max power approach which can easily slow you down unless you are on a Formula 1 track.
Are you saying that the standard fit items for the Griff are right? Or if not, is there a replacement that you think has been properly engineered?
Incidently, I have upgraded the Griff with slightly firmer springs and Gaz shocks which have really improved things, at least from my perspective - I had specific issues with the existing handling that I wanted sorted.
gooner
Do you have any first-hand experience of the TVR bushes that these PF versions replace? You seem to be very forceful in your post so I'd love to hear some of the back to back testing you've done on the std TVR bush the PF version that leads you to these conclusions.
Incidently it was me who approached PF to make these bushes, so as you can imagine : I'm all-ears!
Incidently it was me who approached PF to make these bushes, so as you can imagine : I'm all-ears!
Thanks for all the comments on the TVR bushes.
We certainly agree with NDT that bushes are not designed on NVH alone. The Griff and Chim bushes were developed over a period of about 3 months with on and off vehcile testing and computer analysis in order to engineer the correct compound of polyurethane. Our bushes are not based on stiffening the suspension as such, more allowing for greater control over suspension geometry in order to make the vehcile more predictable. In turn, limits the amount of uncontrolled suspension geometry change.
In order to allow for this control, our TVR bushes have been designed to incorporate a glacier bearing which creates an almost frictionless joint with negligable stick-slip whilst still incorporating all the advantages of polyurethane. This works well in this instant as most double wishbone arrangement suspension doesnt have that much side movement and almost describes a 2D arc, not a 3D arc.
The small amount of thrust movement (under braking and acceleration) is absorbed through adding polycarbonate washers at the ends of the bushes - similar to the original TVR ones. Again this limits the amount of uncontrolled suspension geometry change.
The other benefits of the glacier bearing are the high static and dynamic load capabilities, no lubrication, low wear rate and seizure resistance.
All 800 or so of our parts, from TVR to 70's Alfas, are designed in this way. Suspension is a system, not an individual part that needs 'stiffening up'. The range of parts and stiffness we have available demonstates this.
All parts are designed by engineers with experience across a range of industries.
Tim (BEng, CEng, Eur Ing, MIMechE)
We certainly agree with NDT that bushes are not designed on NVH alone. The Griff and Chim bushes were developed over a period of about 3 months with on and off vehcile testing and computer analysis in order to engineer the correct compound of polyurethane. Our bushes are not based on stiffening the suspension as such, more allowing for greater control over suspension geometry in order to make the vehcile more predictable. In turn, limits the amount of uncontrolled suspension geometry change.
In order to allow for this control, our TVR bushes have been designed to incorporate a glacier bearing which creates an almost frictionless joint with negligable stick-slip whilst still incorporating all the advantages of polyurethane. This works well in this instant as most double wishbone arrangement suspension doesnt have that much side movement and almost describes a 2D arc, not a 3D arc.
The small amount of thrust movement (under braking and acceleration) is absorbed through adding polycarbonate washers at the ends of the bushes - similar to the original TVR ones. Again this limits the amount of uncontrolled suspension geometry change.
The other benefits of the glacier bearing are the high static and dynamic load capabilities, no lubrication, low wear rate and seizure resistance.
All 800 or so of our parts, from TVR to 70's Alfas, are designed in this way. Suspension is a system, not an individual part that needs 'stiffening up'. The range of parts and stiffness we have available demonstates this.
All parts are designed by engineers with experience across a range of industries.
Tim (BEng, CEng, Eur Ing, MIMechE)
This is getting a bit technical for me now, I only understand electrons...
Isn't the main point missed by 'NDT' that the TVR front top rubber bushes seem to get cooked by the exhaust and deteriorate really quickly on Griffs/Chims and the polyurethane ones don't?
Chris BEng, CEng, MIET Etc...
Isn't the main point missed by 'NDT' that the TVR front top rubber bushes seem to get cooked by the exhaust and deteriorate really quickly on Griffs/Chims and the polyurethane ones don't?
Chris BEng, CEng, MIET Etc...
chris_chim said:
This is getting a bit technical for me now, I only understand electrons...
Isn't the main point missed by 'NDT' that the TVR front top rubber bushes seem to get cooked by the exhaust and deteriorate really quickly on Griffs/Chims and the polyurethane ones don't?
Chris BEng, CEng, MIET Etc...
,that and the glacier bearing are the two biggest selling points as far as i'm concerned.I bought mine from Trackcar a little while ago now and theyre such an improvement.Mike Cse(x4) and City & Guilds
>> Edited by mongoose on Wednesday 10th May 14:52
Surely the main benefit of using bushes like these is the inclusion of the glacier bearing allowing much smoother up and down movement for the suspension instead of having to overcome the resistance of twisting rubber in conventional bushes? This has the added benefit of allowing firmer bushes so restricting lateral movement and enabling the suspension to behave more as the designer intended?
Of course I maybe talking complete b
x!!
Mike MBSc
(Motor Bike and Sidecar!!)
Of course I maybe talking complete b
x!! Mike MBSc
(Motor Bike and Sidecar!!)
Just stumbled across this thread - have a passing interest as I've just had Gaz Golds all round but on original bushes..
Anyway on to the real reason for posting, check out my qualifications too!
Radar Love CEng, Msc, BEng(hons), MIMechE
>> Edited by Radar Love on Wednesday 10th May 16:14
Anyway on to the real reason for posting, check out my qualifications too!
Radar Love CEng, Msc, BEng(hons), MIMechE
>> Edited by Radar Love on Wednesday 10th May 16:14
Longbow - I do have some shockingly metallic blue suspension arms from a Cerbera. We will have them measured up this week/early next. We currently anticipate that the bushes will be a similar design to the Griff and Chim ones but we haven't done any testing yet.
It's our next project and when they become available, I'll post on the forum.
PS. Good to see there are so many intelligent people out there!!!!
It's our next project and when they become available, I'll post on the forum.
PS. Good to see there are so many intelligent people out there!!!!
pftim said:
PS. Good to see there are so many intelligent people out there!!!!
Yeah, just a shame that none of them posted on this thread
Congrats to Powerflex on investing time and effort in attempting to help us improve our babies.
Well done to NDT for raising questions which needed to be asked.
I have to say the publicity lacked the required technical level of explanation and sounded more like Dr. Voodoo's miracle cure for coughs, colds and sore feet !
PJ (7 O' levels - None in Metal or Woodwork)
>> Edited by Mr.Cerbera on Thursday 11th May 09:23
I'm confused. I've had my bushes replaced with poly ones (three times as two melted in short succession) and I thought they were Powerflex ones. Is Superflex a seperate company or is there another supplier of bushes that sounds similar?
Ian A (I glanced at a book in a bookshop once that mentioned engineering).
Ian A (I glanced at a book in a bookshop once that mentioned engineering).
powerflex and superflex are different companies, different countries! superflex are made in australia .. fantastic bushes except i could never get hold of enough of them .. i would order 1000 pounds worth and only 300 pounds worth would turn up .. with a 3 month turnaround time it wasn't workable. Very pleased to work with powerflex now, they rock!
B19GRR said:
What the hell is a glacier bearing when it's at home?!!
Rob (2 x Drop out)
ps Hiya Joolz!!!
'ey up Rob
It's a twin concentric sleeve arrangement with very low friction, essentially replicating the action of a rose joint but in a form which can be pressed into teh existing arm with some poly in there so not completely rigid. It ws apparently developed for light cars like caterhams where the resistance to twist of a conventional rubber bush is a significant proportion of the suspension resistance.
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