Upwards pointing wishbones

[Arthur 10]

47 minutes ago, Tom Fenton said:

From experience

 

They can and do

 

Even more so if you start altering camber/caster.

So it might be a good idea to preload the spring in the joint quite a bit, I guess. Maybe it’s not 35mm with 205 shafts either. 

[welshpug 1,622]

Look at the wear pattern in the inner cup, you'll  see how much travel they use

[petert 550]

I like to set mine up so there is >10mm plunge at the closest point in the operating range of the shock.

Edited June 9, 2022 by petert

[Arthur 10]

19 hours ago, petert said:

I like to set mine up so there is >10mm plunge at the closest point in the operating range of the shock.

And that would be with horizontal wishbone, right?

 

I think a perfect rollcentre adjustment would be when the wishbone is horizontal, and thus longest, at max cornering speed just at about 1G. (assuming friction coefficient of the tires is 1 and no downforce)

 

 

[petert 550]

Not necessarily. It's just whenever it's the closest point. Depends on the setup. When you venture down the custom world, anything is possible.

[Arthur 10]

Oké. 

 

M18x100 12.9 bolt + nuts are purchased as well as ball joints. I think I will have to limit the roll center adjuster to max 35mm. All but M18 x 100 was not not available in other then 25 pc package. 

 

Carrier is 26mm, ball 22,8mm and nut 18,5 mm. I'm not sure whether I will keep the bolt in tact or cut the head off. Use the clamp or weld it up. 

 

 

And i made this:

 

Edited June 15, 2022 by Arthur

[Arthur 10]

How much slack do the steering rods have? When 20mm is added at the pivot point at the hub carriers, about 15mm extra will be needed at the steering. Will it cope without redesign? 

[petert 550]

I think I used 306 rods and cut them back a bit.

[wicked 103 3 Cars]

I used 206 steering ball joints on my trackday car. They are a bit longer than 205 ones and bit quicker than changing the rods..

 

 

Edited June 16, 2022 by wicked

[Arthur 10]

I wonder whether I will notice bump steer after wishbone correction. 

[allanallen 528 2 Cars]

11 hours ago, Arthur said:

I wonder whether I will notice bump steer after wishbone correction. 

Yes you will completely alter the bump curve so this will also need addressing. 
 

Using an m18 bolt is not ideal, the spherical needs locate on a good 18mm shank, using a bolt you’ll have the joint located on the thread by the looks of your measurements so it’ll be ill/loose fitting and weaker. 
 

ive repaired/re-engineered quite a few failed rollcentre correction kits. The connection between the hub and bearing is absolutely critical, clamping it all up with a longer PTS style drop pin will work but the ‘head’ of the pin ends up very small to clear the hub and cv joint, I’ve seen the heads break off when using larger spacers to correct roll centre.
Using a pin with no head  is a non starter, there’s quite a few kits on sale for other cars that do it this way, they’re  dangerous. 

[Arthur 10]

Yeah.

 

At arrival of the bolt it's obvious the spherical of the joint would be 100% on the threat of the bolt. I don't like that either. I was thinking to take an M18 x 120 or 130 and cut that, but I can't find them yet without having to buy 25 pc. 

 

Clamping is another story. I was thinking when you fit a cone, force would be transferred through the cone and then to the hub. But indeed the arm will be longer and so will the force on the clamp be. Unless you weld the cone to the hub. Then the force will be on the cone, and mostly shear force. Then the head of the bolt can go off as well. The shear force will be transferred to the cone and hub directly.  The rest will be taken by the bolt, but that is not much compared to the shear force imo. I've even taken stainless A4 nut because of that. Clamping force for the spherical will not be that much imo. 

[Arthur 10]

So like this solution (clio). It does indeed seem the arm of forces will be tripled. And so will the force on the clamp be. I agree this is outright dangerous. 

 

This is why I wanted to weld the cone to the hub. Maybe not even weld the bolt to the hub and thus not tempering with the steel of the bolt that much. Just weld the (steel) cone to the (cast steel) hub and then use the bolt more or less separately. That way I can keep just 1/3 of the head of the bolt for the clamping force and 100% of the shear force of the bolt. 

 

Maybe I can get a purchaser at work to buy me 2 pc of 120 or 130 long bolts. 

 

Another solution might be to forget about the roll centre and just focus on the camber only. Then the spherical will be on the shank and force will be equal to standard. It always better to have her on the shank . The 106 rear anti roll bar did already massively improve the roll anyway. 

 

Edited June 17, 2022 by Arthur

[Arthur 10]

Or just accept 10.9 grade since it's "only" an 800kg 205 upgrading to 18mm pin anyhow. 

 

When I calculate M18x2,5 15.5mm core x 900 N/mm x 75% for shearforce I still get to 60 ton. That seems enough. (when the cone is welded, that is)

Edited June 17, 2022 by Arthur

[welshpug 1,622]

I would worry less about the roll centres tbh, oem pug arrangement  really isnt that  bad, you need to get it measured and experiment if you need to move the pivots at all.

 

I helped convert some 106 legs to an inverted insert, with our own steering  a that allowed much longer spring and easy steering arm height adjustment, ended up with the pivot within a few mm of the original location when bump steer was checked.

[wicked 103 3 Cars]

17 hours ago, welshpug said:

I would worry less about the roll centres tbh, oem pug arrangement  really isnt that  bad, you need to get it measured and experiment if you need to move the pivots at all.

Second that... If it is not for a trackday car and you don't go really low with ride height, I wouldn't bother the effort and hassle to correct it. The additional camber will already improve the handling. You must go ridiculously fast on public road to benefit from improved roll center..... 

[Arthur 10]

Oké, noted. But when I do correct it, it won’t get worse? 
 

I was thinking to add 35mm because it’s lowered 35 mm. 

I must add something between the ball and the hub to get more angle out of the ballpoint anyway. But when I add a ring of say 3mm I could stick with the 12.9 bolts and use them as an clamped pin like original setup. 
 

Using 10.9 I can get more bolts for a reasonable price. Even fine thread. M18x1.5 has a bigger core diameter so I would not use much settling for 10.9. 
 

In that case I would not go for a clamping solution though. Then I will add more cone/ring and weld it all up. 
 

Does my “add 35mm to correct roll centre cant hurt” theory stand? 

[Arthur 10]

Come to think of it. Since I wouldn’t use the threat for the shear forces anyhow, core isn’t even relevant. It’s the shearforce of an 18mm pin in both solution. 

Edited June 20, 2022 by Arthur

[Arthur 10]

Machining the 12,9 bolts is easier then expected.
 

I can turn the head down and win 15mm of shank. This way I can more or less use the bolt as the original pin setup, with clamp, and still have 5 to 6 mm left for a cone washer to clear the carrier.
 

Uprated to 18mm and with failsafe clamp bolt making sure it can’t get out no matter what. 

[wicked 103 3 Cars]

On 6/16/2022 at 11:08 PM, allanallen said:

Using a pin with no head  is a non starter, there’s quite a few kits on sale for other cars that do it this way, they’re  dangerous. 

This.... 

 

If tighten the bolt under the rose joint, you will pull the pin out of the hub. An OEM arm will not pull on the pin like that. 

Edited June 23, 2022 by wicked

[petert 550]

Indeed. You need to machine up a pin from 4140 (or similar) which has a head. The head is relieved so it fits snug against the vertical hub surface, like a D in the top view. You also need to machine the horizontal surface flat. These are Group A hubs which already have those features, but you can easily modify a standard hub.

[Arthur 10]

Hmmmm

 

Yeah, I didn't really think about it like that. It kinda looks like the standard solution, but that indeed does not have the pre tension force of the nut. I thought the bolt to be a stopper to avoid pulling it out. together with the clamping force. I could also weld it to the carrier, but the welding puts me off. Adding roll Centre would also require welding but a talk with the certified welder and petrolhead at work puts me off as well. 

 

Doing it with 1/2 a head though, will force me to settle for 10,9 bolts. I can't machine threat. At least never done that, so would be new. 4140/42CRMO4 is about the same strength as 10.9 bolts imo. So using M18 x140 as a source for my pin makes sense. Easier for me to source and I don't have to machine thread. The upgrade to 18mm helps of course since it would be better than the standard 16mm anyway. 

 

I have a back to school feeling when I try to calculate it all. Doing it like the group a solution above. (1/2 a head, cone washer of about 5mm) would mean pre tension of the m18 nut to keep it all in place. The the majority of the force at driving it would be shear force on a 900Nm/mm pin, 5 mm from the face. (I think)

 

So 900 x 255mm/2 is about 230 kN. I think it depends on the clamping force what the shear force will be. As long as the clamping force will not be overcome, the cone washer and spherical  will stay seated, and 100% of the shear force will be available to deal with potholes and curbstones. The higher the washer, the worse that will be. 18 x 5 triangle will be at play in this case so I don't think huge pre tension is needed. Assuming shear force is about 2/3 (conservative) it will give me about 150 kN. Taking 2/3 of that because the pin is already loaded with pre tension give me 100 kN. The joints are rated 95 kN

 

I can't imagine that going wrong. 10 000 kg on a joint. One should be able to hang the car from a crane on that one wheel only and wiggle the hell out of it and it will still not break imo. The rim might, but that joint, neh. 

 

Something I miss?

 

   

Edited June 24, 2022 by Arthur

[welshpug 1,622]

Using 307 or similar  hubs with a screw in lower balljoint seems a lot simpler to make strong, its what the Citroen C2 ran as an R2 rallycar, and satchell engineering have also done.

[allanallen 528 2 Cars]

This is how I do it, machine the bbj mating face flat and at 90 degrees to the hole, bore and thread the hole and then screw in a shouldered extension piece to what ever length you require, then clamp it all up with the pinch bolt. It’s imperative that the shoulder is flat against the hub as this is where it gets all its strength, if it isn’t it’ll fret in the hole and snap. 

I’ve had zero failures out of 250 plus kits on Renaults, fords and Peugeots using this method. I reckon I've repaired  around 30 setups like the one you’re trying to do that have failed.
 

[Arthur 10]

The failures are the ones without the head I reccon?