LWE extended wishbone/technical help needed.

[Paul bow]

Hi Guys..

I’m stuck here with a problem.
I am currently building a semi lightweight E .
After having RS panels make the panels and spending weeks welding and finishing it’s all looking nice n dandy, I am now left with the issue of getting the offset correct.
The offset in the original lightweights came from the wheels and then a 10mm spacer at the diff end.
The LWE wheels I have (8” rear 7” front) are a little short of the mark in the offset .

I am not using the spacer as I don’t want to have to strip the diff out and find the new longer high tensile steel bolts to accept said spacer , so I’m having new driveshafts made longer.

The solution for me is made up by extending the lower wishbone by the extra needed in my case this is 16mm as per the std LWE plus 6.2mm to make up for my wheels being short in the offset.
Question is..
I need to extend my wishbone by 22.2mm, how much would the driveshaft need to be increased by?
This will be a cakewalk for many on here, but I’m just not getting it !
Thanks guys

[mgcjag]

Hi Paul...I cant do the calculations...however you could trial and error by useing spacers inboard till you get what you want.....or get a longer xj6 driveshaft( cheap on ebay) to play with..cut it and use a slip tube to join it...you then have an adjustable length driveshaft to play with.....Steve

[Paul bow]

That’s certainly a good idea Steve.. just short on time and looking to try n get it over the line without messing around, But that’s a great solution thank you

[abowie]

or get a longer xj6 driveshaft( cheap on ebay) to play with..cut it and use a slip tube to join it...you then have an adjustable length driveshaft to play with.....Steve

That's how I'd do it.

[Airborne62]

115.9

[Series1 Stu]

115.9

Interesting. How did you arrive at this figure? Surely, you need to know at least 2 of the 3 distances between the inner fulcrums and the distance between the 2 outer fulcrums? It's essentially a 4 bar link to control camber change and we don't know what the camber settings are meant to be for the LWE, either.

It would be interesting to see your working.

Regards

[MarekH]

This is simple geometry, but measuring these angles and lengths with any great accuracy isn't.

Make a triangle using the 116 and 122.2 sides, with a third side which will be a horizontal. You're going to need to know the angle to the horizontal of the 116 long side for that. This gives you the additional length of an assumed horizontal driveshaft. It also gives you the new location of the lower hub.

You need to do a similar triangular calculation with the old top length, the previously derived horizontal (or the new hub postion), to derive a new top length. Doing otherwise very obviously gives you a very different camber setting.

If the driveshaft isn't horizontal, repeat the second paragraph's logic rather than take the first's.

The double check for the correct geometry is that the old and new top and bottom lengths are the same vertical distance apart as before, otherwise they won't bolt up against the differential or the hub.

kind regards
Marek

[Airborne62]

You're making it too difficult.
You are changing the length by about 5%.
Assuming the bases of the trapezoid are identical and Ignoring the change in the tangent of the angle (assuming a level driveshaft), just use a proportional difference. You will be within camber adjustments at that point. Just my opinion.
But then again, I am not a fan of polishing a cannon ball into a bee bee.

[MarekH]

You're making it too difficult.

Agreed.

It's essentially just a parallelogram with two fixed length vertical sides. The uprights are parallel save for camber angle. Cutting and welding loads of stuff between those fixed points is harder than putting a spacer in.

kind regards
Marek

[Paul bow]

Wow guys.. !!!
I’m lost on most of that above and really wishing I had taken more time in understanding this part of the build. Thinking I could just get the parts made and all the info was readily out there and available wasn’t as simple as I first believed.
Anyhow…
I’ve had a company (simply performance) make the driveshaft.

Its 1/2” longer a hollow dog bone, this saved me having to strip the diff out and change the high tensile press fit steel bolts in the output shafts for longer ones should I have gone up the spacer route.

The bottom wishbones are made 16mm longer as per the original LWE spec, 312mm in length which is about 2mm shorter than the original, reason being to allow some shims to make up the extra or to get the camber correct, its not a complete science there are variables it’s also easier to add a few shims, not so easy to take anything away..
I went with those sizes 16mm extra wishbone, 1/2” driveshaft as that is what the originals run.
It’s been a hard slog, I wouldn’t repeat it, the bodywork is a cake walk but the IRS for me not so..
Any info on a good camber gauge guys ?