Project Wishbone Comes Out Of The Closet At Long Last...

[jacobs53 0]

Right, since early November a team of student (including myself) have been doing looking for a topic for our product improvement module. Well I can now tell you all that we are on the final stages of developing a adjustable 205gti wishbone...... (your probabily thinking , not this crap again!)

 

Well this wishbone is slightly different to all them bodged welded rose jointed ones. we did alot of research into customer requirements (with the help of AB motorsport) and it seemed that the wishbone was a major deisgn fault of the peugeot 205gti. So we asked 100 competitors to list everything they wanted to be improved.

 

Customer Requirements

 

*Must have adjustable length to allow changes in camber angle

*Must be able to withstand additonal focres applied under suspension travel

*Must fit the original location on vehicle and be compatible with existing components

*Must use commonly available off the shelf service parts

*Must be lighter than the original component

*Must reduce compliance in the moving components

*Must be corrosion resistant

*Needs to be affordable

 

So we produced a product specification which was written to standards of BS 7373, to design and produce a new wishbone which included all (or most) of the above requirements

 

Alot of additional research was conducted after the report into materials (tensile strengths, expansion rates etc..) ball joints, rose joints, hub adapters. We also thought about making the wishbone interchangable between a ball joint and a rose joint, but unfortantly we ran out of time to find a suitable ball joint, which matched the rose joint thread size (but we will hopefully find one)

 

So i can reveal the CAD drawings of the finished component, it will encorpriate the use of the standard bush to bolt to the subframe (so either OE bushes or powerflex) The rose joint provides up to 21mm of adjustement, 6mm of positive camber gain, 15mm of negative camber gain. The hub adpater is designed to allow the standard hub to be used and comprimises of two parts, one is a locking pin, the other is a rose joint insert.

 

I hope you find these drawings intresting, and I want your comments

 

http://img.photobucket.com/albums/v459/jacobs53/1.jpg

http://img.photobucket.com/albums/v459/jacobs53/2.jpg

http://img.photobucket.com/albums/v459/jacobs53/3.jpg

http://img.photobucket.com/albums/v459/jacobs53/4.jpg

http://img.photobucket.com/albums/v459/jacobs53/5.jpg

http://img.photobucket.com/albums/v459/jacobs53/6.jpg

 

cheers lee

[engine killer 5]

first of all, thanks for sharing.

 

after seeing these two

 

http://img.photobucket.com/albums/v459/jacobs53/5.jpg

http://img.photobucket.com/albums/v459/jacobs53/6.jpg

 

can the rose joint be even more user friendly like this:

 

http://community.webshots.com/photo/540539...084130750SzMDIn

http://community.webshots.com/photo/540539...084130750tsjkZE

http://community.webshots.com/photo/540539...084130750mgZPyF

http://community.webshots.com/photo/540539...084130750GSYTyO

http://community.webshots.com/photo/540539...084130750NDnfHs

 

well, yes they failed after about 20km but i guess a much stronger / thicker screw may solve the problem. i just haven't got any more spare arm to play around with.

[M3Evo 0]

Crumbs DM!

 

Obviously you've done your calcs on the design, but isn't there gonna be one hell of a bending moment under braking in the long straight leg of the wishbone?!

[Craigb 2]

One question is why continue with a necked pin and pinch bolt ..

 

This is a major area of weakness of the std one hence the reason why a GPN one has a partially machined pin and a GPA one has a reversed pin with a head that helps when hubs start to go oval..

[jacobs53 0]

cheers for the replies guys.......

 

first of all, thanks for sharing.

 

after seeing these two

 

http://img.photobucket.com/albums/v459/jacobs53/5.jpg

http://img.photobucket.com/albums/v459/jacobs53/6.jpg

 

can the rose joint be even more user friendly like this:

 

http://community.webshots.com/photo/540539...084130750SzMDIn

http://community.webshots.com/photo/540539...084130750tsjkZE

http://community.webshots.com/photo/540539...084130750mgZPyF

http://community.webshots.com/photo/540539...084130750GSYTyO

http://community.webshots.com/photo/540539...084130750NDnfHs

 

well, yes they failed after about 20km but i guess a much stronger / thicker screw may solve the problem. i just haven't got any more spare arm to play around with.

 

The screw thread on the rose joint is 15.62mm, it is encased inside a machined threaded adpater which is 25mm thick so it has a wall thickness of 4.69mm each side of the thread. To increase the factor of safety we also obtained the longest threaded rose joint we could in the order of 46mm, and decided under full extend (or maximum negative camber) there will be at least 23mm of the threaded section remaining inside the threaded insert. Along with this we also will include a small lock nut on the thread.

 

Crumbs DM!

 

Obviously you've done your calcs on the design, but isn't there gonna be one hell of a bending moment under braking in the long straight leg of the wishbone?!

 

We have simulated the same design as above in solidworks, and simulated a forces of 5g on the hub adapter and wishbone assembly, and the weakest point of the whole design is the bush locations. The tube of the wishbone is 25mm dia, with 5mm thickness. We noticed the smaller you make the thickness the weaker it becomes (obvesiously) and we thought 5g of force and load was the maxmium you would ever exceed. (considering braking and steering over a pothole of depth 100mm produces 2.5g of force)

 

One question is why continue with a necked pin and pinch bolt ..

 

This is a major area of weakness of the std one hence the reason why a GPN one has a partially machined pin and a GPA one has a reversed pin with a head that helps when hubs start to go oval..

 

As above really.... We did think this would be a weak point, so we considered with using a bolt with lock nut above. But the problem is that the maximum dia the bolt can be is 16mm to enable it to be used with the standard hub. Don't worry though we thought about every problem, and thats why we ran a simulation.

 

Sorry theres no dimensions, obvesiously we don't want people stealing our design

 

cheers lee

[Craigb 2]

But the problem is that the maximum dia the bolt can be is 16mm to enable it to be used with the standard hub.

cheers lee

 

why is 16mm a problem , are you saying that with your design you need to modify the hub ?

[Guest Tidybri]

Could be very interesting what sort of price are they going to be?

 

Surely more than other inferior parts if its going to be that much better nothing is ever better and cheaper!?

[jonah 1]

*Must be able to withstand additonal focres applied under suspension travel

Is that another way of saying "must be stronger than the standard wishbone"? Because, from a rallying perspective at least, that should be the number one priority.

 

When you say you have simulated 5g of force... is that 5g acting on the total mass of a 205, or just the front corner weight, or something else? How did you get a figure of 2.5g for a 100mm pothole??

 

I think you may have underestimated how much force goes through the wishbone. I know of a replacement wishbone on the market that is rated at 35000lb of hub loading... that's equivalent to about 18g acting the entire mass of a 205!

[M3Evo 0]

Was gonna say, my very old book on suspension design by Colin Chapman says something about mounting 4" kerbs at high speed imposing over 6g on the suspension.

 

I'm really not trying to pick holes here and am only asking because this looks very interesting, but why have such a large cantilever when the material could be used so much more efficiently with a bit more triangulation, or just a larger second moment of area?

 

Boo, no dims on the drawings Was gonna run an FEA on it with the 35000lb load.

Edited May 12, 2006 by M3Evo

[jacobs53 0]

why is 16mm a problem , are you saying that with your design you need to modify the hub ?

 

16mm is the internal dia. of the standard 205 hub, where the ball joint fits in. No the standard hub does not need modifying at all, that was one of the main aims of the project to keep all the standard manufactures components.

 

Could be very interesting what sort of price are they going to be?

 

Surely more than other inferior parts if its going to be that much better nothing is ever better and cheaper!?

 

actually there not too bad, parts wise only your looking at around aprox 100.00 per side (this is a pure estimate at the present though)

 

Is that another way of saying "must be stronger than the standard wishbone"? Because, from a rallying perspective at least, that should be the number one priority.

 

When you say you have simulated 5g of force... is that 5g acting on the total mass of a 205, or just the front corner weight, or something else? How did you get a figure of 2.5g for a 100mm pothole??

 

I think you may have underestimated how much force goes through the wishbone. I know of a replacement wishbone on the market that is rated at 35000lb of hub loading... that's equivalent to about 18g acting the entire mass of a 205!

 

we applied the force from the top and side of the hub adapter, then applied the same force to the wishbone assembly. And that force was not applied with the 205's weight. The figure was taken from a designing performance suspension book, can't remember the author at present. The wishbone is aimed at all types of competition use, from track day to serious competition use. The idea was to produce the wishbone with a interchangable ball joint and rose joint so that either could be used, making it very user-friendly for the track-day driver.

 

Was gonna say, my very old book on suspension design by Colin Chapman says something about mounting 4" kerbs at high speed imposing over 6g on the suspension.

 

I'm really not trying to pick holes here and am only asking because this looks very interesting, but why have such a large cantilever when the material could be used so much more efficiently with a bit more triangulation, or just a larger second moment of area?

 

Boo, no dims on the drawings Was gonna run an FEA on it with the 35000lb load.

 

The 205 wishbone is perfectly flat, until the ball joint where a 20 degree angle is included in the design. So to keep the geometry correct we have placed the adapter in the exact same place. We could of reduced the angle but this actually changes the geomtry, not when the car is level, but when the suspension is compressed.

 

No dims, first thing i took off.....

 

cheers for the feedback guys, im writing all this down to present to the group.

 

lee

[Henry Yorke 269 3 Cars]

I'm no techy, but a consideration to bear in mind is that on full extent, what is the impact on the driveshaft seating in the hub? There have been numerous posts about 1.9 shafts perishing when fitted in conjunction with 309 wishbones and especially as the rally boys will be the ones on full lock with their foot to the floor and they are the target market I assume.

 

Like I say, it is just an idea and one to add to your risk register / assumption list for this project

[Adam B 0]

To add to Henry's comment,

a faulty wishbone from GSF (put the hub about 10mm further out at its base) destroyed a brand new 1.9 driveshaft in under a mile.

Would 309 shafts be long enough at maximum negative camber?

Looks good though from where I'm sat.

Edited May 12, 2006 by Adam B

[jacobs53 0]

I'm no techy, but a consideration to bear in mind is that on full extent, what is the impact on the driveshaft seating in the hub? There have been numerous posts about 1.9 shafts perishing when fitted in conjunction with 309 wishbones and especially as the rally boys will be the ones on full lock with their foot to the floor and they are the target market I assume.

 

Like I say, it is just an idea and one to add to your risk register / assumption list for this project

 

cheers for that reply.... We did take into consideration the driveshaft because we knew that it was an issue. This is where we lack a little bit of information, As we don't have a full car to work with. From the research we have found the driveshaft drops from the differential unit when the steering is either full lock, or when the suspension is under maximum travel.

 

Now we had a few idea's One was being using the 309 gti driveshafts (pretty obvesious really) but this will cost the competitor more money, and if the class demands standard drivetrain then your buggered. Another idea we had even though we haven't researched into it as yet, is to use the 205 gti driveshafts and machine a spacer whicch sits behind the hub over the top of the driveshaft splines before it engters the hub splines. We knew straight away this was limited on a few factors

 

1) less contact patch between the the driveshaft splines and the hub splines

2) less thread for the hub nut to lock onto

 

Or the other idea was to limit the amount of negative camber to the safe operating limits of the driveshaft.

 

I have been in contact with Ab motorsport who should be lending us a 205gti for day to test the wishbones, and hopefully we can iron out this driveshaft issue once and for all.

 

Il approach the group on Monday for some updates on the driveshaft situation

 

 

 

-->

QUOTE(Adam B @ May 12 2006, 10:28 PM) <{POST_SNAPBACK}>

To add to Henry's comment,

a faulty wishbone from GSF (put the hub about 10mm further out at its base) destroyed a brand new 1.9 driveshaft in under a mile.

Would 309 shafts be long enough at maximum negative camber?

Looks good though from where I'm sat.

 

yes the 309 shafts would be longer enough at maximum negative camber, i replied to your questions above by the way

 

cheers for the support and comments guys

[jonah 1]

I don't want to detract from what you're trying to do, but I think you need to be VERY careful about the safety aspects if you're seriously thinking of marketing this thing, especially as a rallying upgrade. It's a safety-critical item, and any breakage could result in a big accident. I can assure you, rallying puts extreme punishment on the suspension...

 

I'm with Craig on the point about the necked pin. This is THE weak point of the standard design, so if your design doesn'tt modify this part, then it cannot possibly be stronger than standard. In fact, if the sims show that the weakest point in your design is the bush housings, then it proves that it's weaker than standard overall.

 

One thing I noticed in the drawings is that the hub adaptor (the conical shaped thing) looks quite tall, which spaces the balljoint away from the clamp. The bigger the spacing, the weaker the design will be, because the failure mode of the standard design is that the pin prises the clamp apart, causing bellmouthing. The further the balljoint is from the clamp, the greater the leverage it has on the pin (the greater the moment to rotate the pin in the longitudinal plane for a given force). Ideally you would want the RJ butting right up against the bottom of the hub carrier, although I guess that would cause them to foul on the extremes of suspension travel...

[engine killer 5]

have you seen the TAS's arm? i am wondering if you can think of the caster/king pin adjustability in your design as well. i don't really like the TAS eccentric top mount, whenever you dial the camber the caster also be changed.

[base-1 17]

Another idea we had even though we haven't researched into it as yet, is to use the 205 gti driveshafts and machine a spacer which sits behind the hub over the top of the driveshaft splines before it engters the hub splines. We knew straight away this was limited on a few factors

 

1) less contact patch between the the driveshaft splines and the hub splines

2) less thread for the hub nut to lock onto

 

I know of a guy round my way who used to rally 205s, and in his opinion this spacer method is the only way to do it, not to use 309 shafts.

 

Now whilst I consider him to be something of an idiot, and that statement is obviously rubbish, if he was finishing/being competitive without failures because of this, then it has to work, whether it is the cheapest/easiest/best way or not.

[jacobs53 0]

I don't want to detract from what you're trying to do, but I think you need to be VERY careful about the safety aspects if you're seriously thinking of marketing this thing, especially as a rallying upgrade. It's a safety-critical item, and any breakage could result in a big accident. I can assure you, rallying puts extreme punishment on the suspension...

 

I'm with Craig on the point about the necked pin. This is THE weak point of the standard design, so if your design doesn'tt modify this part, then it cannot possibly be stronger than standard. In fact, if the sims show that the weakest point in your design is the bush housings, then it proves that it's weaker than standard overall.

 

One thing I noticed in the drawings is that the hub adaptor (the conical shaped thing) looks quite tall, which spaces the balljoint away from the clamp. The bigger the spacing, the weaker the design will be, because the failure mode of the standard design is that the pin prises the clamp apart, causing bellmouthing. The further the balljoint is from the clamp, the greater the leverage it has on the pin (the greater the moment to rotate the pin in the longitudinal plane for a given force). Ideally you would want the RJ butting right up against the bottom of the hub carrier, although I guess that would cause them to foul on the extremes of suspension travel...

 

Our group has been researching this since November, and on the top of our list is durability and safety! Obvesiously if the product fails then a serious accident will occur, which will cause the car to be uncontrollable. Thats why we use the 5g figure as thats double the force that one of our reference books dictates. We think we know why its failing by the bushes and its due to the bush material allow too much flex, when we used solid metal mounts on the subframe locations it was a hell lot stronger! But unfortnaly this product is aimed at everybody, so solid mounts may be a little OTT for the road user, also hence the ball joint idea.

 

With reagrds to the hub adapter, this was one of our worries. If you measure the standard ball joint it causes the hub clamp surface to sit 18mm above the wishbone surface (hence why ours included the 18mm step, to keep geomtry very close to standard). We did have another idea for the hub adapter, which involves producing a one piece adapter which was tapped at the bottom to except a bolt to clamp it in place. But this takes longer to disassemble then our current design. We included a circlip which locks onto the top of the pin (hub adapter) to prevent the pin from dropping out the hub in the event of the clamp bolt shearing or failing. Obvesiously this isn't super strong but it may enable the pin to stay in longer enough for the driver to control the vehicle to a safe stop.

 

Another recommendation from alot of people is to reduce the 20 degree angle to 10 degrees and bring the start of the angle forward. I agree this would offer more strength, but the geometry of the bottom rose joint would be slightly at the wrong angle, and also the rose joint would not be centrallised.

 

 

have you seen the TAS's arm? i am wondering if you can think of the caster/king pin adjustability in your design as well. i don't really like the TAS eccentric top mount, whenever you dial the camber the caster also be changed.

 

We did design another wishobe with a inner rose joint attachment to change to the caster, but there is very low demand for this. But to be honest the rpice difference between the non-adjustable castor and adjustable is only 5.50 in components anyway. makes you think how companies can charge rip-off prices!

 

I know of a guy round my way who used to rally 205s, and in his opinion this spacer method is the only way to do it, not to use 309 shafts.

 

Now whilst I consider him to be something of an idiot, and that statement is obviously rubbish, if he was finishing/being competitive without failures because of this, then it has to work, whether it is the cheapest/easiest/best way or not.

 

Yeah it would work, but I need a car to see how much spline contact is remaining on full adjustment, if its only 5mm then it **could** be a option.

 

 

lee

[Pug_101 0]

I was wondering if any strength problems have been found in the normal non-adjustable wishbone (with balljoint), has anyone used these for racing when on a tight budget?

Thanks

[B1ack_Mi16 67]

You should really take the CAD file and impoort it into Fedem. It's a dynamics program that can simulate load, forces and potholes in the road.

 

I did simulate a few Saab 9000 bottom arms this spring as we had a project about making the lightest and still strongest bottom arm on a Saab 9000.

 

You can put on the loads you wanna, and see how many cycles it can take with fatigue before it breaks.

Shouldn't be too hard to make an approximately model of the original wishbone either, just to see how it performs compared to that.

 

This is a picture from the simualtion program, showing the number of load cycles before it breaks.

 

[jacobs53 0]

we simulated the wishbone we designed in solidworks. Which allowed us to run stress anaylis on the component. But I might draw up the orginal though and see how it compares

 

lee

[jonah 1]

But I might draw up the orginal though and see how it compares

That's a very good idea. You would also need to model the lower part of the hub carrier and clamp bolt that the pin fits into, since this is also involved in the failure mode of the standard part - excessive force prises the clamp open and deforms it (from what I can tell), exposing the necked part of the pin to heavy load, which then snaps.

 

The circlip on the top of the pin is a nice idea as well but I don't think it will really help prevent stress-related failures, because (again in my experience) it's not the pinch bolt that snaps but the pin itself. Which renders the top half of the pin pretty useless...

[Guest Nuno205Rallye]

Hi,

 

I would be very interested in this, specially if a version with solid bushed is available.

 

 

Why don´t you create a design with more triangulation? it would not make a big difference for the price

 

 

This is the 205 Rallye Group A tubular wishbone, notice how triangulated it is in comparison with your design...

 

[jacobs53 0]

can't include more triangulation as any more than specified on the drawings that I produced interferes with the location of the standard anti-roll bar. The only way to increase triangulation is to custom make a new anti-roll bar

 

lee

[jacobs53 0]

someone aproached me today in college, who knew of the forum. Who are you?

 

lee