Millie antiroll bar

[cabrioman]

Re: Millie antiroll bar

Paul

Had a quick look round online on this and I can't see anywhere that shows different castor choices for the ARB. Different diameters and multiple part numbers for some diameters but nothing related to castor options.

If you look at the parts catolog at https://ford.7zap.com/en/car/?view=list it shows the ARB options for the different models including diameters. If you select the broad year range and don't put in a specific variant it shows all ARB for all models for the particular year range. Interestingly it does not show differences between 4dr and 3dr.

Makes me think the differences may be just the model the ARB was fitted to. The 24mm appears to come in only one part number regardless of the model even including Cosworth.

John

[kahawi]

Re: Millie antiroll bar

Here are some more dims from the front suspension, pretty self-explanatory and might save you from wrestling with the ARB again. The ‘compression strut’ is nearly parallel to the track-rod but leans closer to the bumper at the outer end.

Caster Dims.jpg

p.s. The 455mm dim is about the same on both sides + 5mm

[milliemarlin]

Re: Millie antiroll bar

Thanks kahawi and John,
The ARB measurement I would like can be measured by placing the ARB on the ground leaning against a cupboard or wall. It is easiest to lean the flat side against the wall hold it there with a wedge under the bottom.

Img_8630s.jpg

Then measure from the ground to the midpoint on the TCA positioning shoulder. Kahawi’s looks to be about 317 mine is 320. I was hoping to find about 12mm difference. Does that rule measure from 0?

These are from the bent estate one.

Img_8629s.jpg

Img_8632s.jpg

My estate car one is 312 off side and 325 near side, 13mm difference. Unfortunately, I did not have anything to measure the caster angle before I took it off. I know the near side was way out but I don’t think the off side was good either.

I estimate the Sierra suspension leg to be about 400mm long, about 600 from the top mounting to the bottom ball joint. That would mean an increase of 12 mm on the ARB would increase the caster by about 1 degree. There seems to be a notion that a bigger caster is better for stability and a good thing on power steering cars. I suspect there is quite a wide tolerance on the Sierras and even with the wrong size you would be hard put to feel a difference. . Assuming the body mountings are the same for all versions it looks like the caster angle is increasing with the weight of the car.

The second measurement is from the back of the TCA mounting face to the centre of the front U mounting bolt. I need both hands to do it so I can't hold the camera. I am trying to make sure the ARB U-bracket mounting plate is in the right place.


I took her out for a spin this morning and on a straight smooth road she drives as well as before. Everything else is a setback.
Paul

[kahawi]

Re: Millie antiroll bar

Being rather more careful and jacking the ARB up flat against the wall, with an 8mm 'foot' to allow for the 'end' of the rule, surprisingly I get the same on both ends at 322mm:-

Both.jpg

[kahawi]

Re: Millie antiroll bar

ARB-.JPG

[milliemarlin]

Re: Millie antiroll bar

Paul
<snip>
If you look at the parts catolog at https://ford.7zap.com/en/car/?view=list it shows the ARB options for the different models including diameters. If you select the broad year range and don't put in a specific variant it shows all ARB for all models for the particular year range. Interestingly it does not show differences between 4dr and 3dr.
<snip>
John

Thanks for pointing me at that parts web site. I have used a similar one:

http://www.fordopedia.org/parts-catalog/sierra-mk1/B1.10

This one list one part number for 24 and one 28 mm diameter bars but 4 different 26mm bars. These are two types for GB and two for Germany (D). 7Zap adds another part number. Trying to figure how these relate to cars will only ever lead to madness!
Paul

[milliemarlin]

Re: Millie antiroll bar

Kahawi and others,
Thanks for all the good information.

This bit of steering geometry is a triangle with the TCA on one side, the ARB and chassis on the other two. The dimension I really want to verify is the chassis side of the triangle. The question is was my mounting plate welded on too far forward. I have marked up your picture...

Arb-2.jpg

The easiest measurement on an assembled car is from the back of the TCA mounting face to the centre of the front U mounting bolt.

[Peterx]

Re: Millie antiroll bar

Paul,
have you thought of reducing the length of your H/D bush to move the TCA back and adjust your caster angle? If you cut down the 'crush' tube and remove the same amount from the inside faces of the bushes the TCA will move back. So long as you don't remove so much that the nut hits the end of the thread it should be OK. Easier than having the shoulder of the ARB removed. Just an idea.....
Peter

[cabrioman]

Re: Millie antiroll bar

Managed to take some measurements for you Paul.

The ARB measured as you wanted on my 24mm ARB is 319mm on both sides.

Taking a measurement from the centre of the front ARB u-mount bolt to the face of the TCA mounting lug (lug nearest engine) gives a measurement of 270mm both sides.

John

[milliemarlin]

Re: Millie antiroll bar

Paul,
have you thought of reducing the length of your H/D bush to move the TCA back and adjust your caster angle? If you cut down the 'crush' tube and remove the same amount from the inside faces of the bushes the TCA will move back. So long as you don't remove so much that the nut hits the end of the thread it should be OK. Easier than having the shoulder of the ARB removed. Just an idea.....
Peter

I have. The problem is a reduction of 12mm is quite large and I think I will end up with a pretty solid joint. That might be just as bad as the compression strut.
Paul

[milliemarlin]

Re: Millie antiroll bar

Managed to take some measurements for you Paul.

The ARB measured as you wanted on my 24mm ARB is 319mm on both sides.

Taking a measurement from the centre of the front ARB u-mount bolt to the face of the TCA mounting lug (lug nearest engine) gives a measurement of 270mm both sides.

John

Thank you John. I am very grateful to all who have gone to the effort of taking measurements.
Paul

[ggrum]

Re: Millie antiroll bar

Paul, don't know if this is of any use to you but I have just measured the dimension from the centre of the ARB at the chassis mounting point to the centre of the lower suspension arm at the point where the ARB is attached as 400mm +/- a small number of millimetres. The same both sides. I haven't measured the castor angle but the self cantering on my car is quite strong suggesting that it may be a bit on the high side but not high enough to be a problem, in my opinion.
Geoff

[greyV8pete]

Re: Millie antiroll bar

Paul,
have you thought of reducing the length of your H/D bush to move the TCA back and adjust your caster angle? If you cut down the 'crush' tube and remove the same amount from the inside faces of the bushes the TCA will move back. So long as you don't remove so much that the nut hits the end of the thread it should be OK. Easier than having the shoulder of the ARB removed. Just an idea.....
Peter

Wouldnt suggest doing that. Firstly a say 6 mm cut back would only give 3mm shift of the track control arm. Secondly if the service parts were replaced with standard off the shelf in the future then there would be a few surprises in store! Peter.

[greyV8pete]

Re: Millie antiroll bar

Coincidentally I have just finished machining my anti roll bar shoulders back to get castor from the previously excessive 9deg down to 6deg, which is a figure more suited to road going cars. Will post more info and dimensions tomorrow. Watch this space as they say! Peter.

[milliemarlin]

Re: Millie antiroll bar

I gotta admit I was surprised to see thicker ARBs commanding quite a price hike on eBay. I pondered how much difference moving from 24 to 28mm would make. I didn’t think it could make much difference. The most excellent Roy Mech website http://www.roymech.co.uk/Useful_Tabl...n/Torsion.html supplied the relevant formula. See that site for full explanation of the formulae. Warning maths is not my strong point. Θ the angle of twist is given by:

F2.jpg

Where J' = Polar moment of inertia (m^4 = cubic metres).For circular sections this is derived from the radius.

F1.jpg

So the angle of twist is related to the reciprocal of the radius. A bigger the radius (thicker bar) will make the twist smaller, which makes sense.

Assuming everything else is equal and accepting that the ARB is not a uniform bar I calculate:

For 24mm diameter r^4 = 20736 mm^4
For 28mm diameter ARBs 38416 mm^4 is getting on for double thus halving the angle of twist.
The 18mm ARB 6561 mm^4 is about 1/3 the torsional strength of my 24mm version.

I have seen it said that there are 16mm ARBs but I suspect they only fitted to Sierra Unicorns.

I have seriously contemplated cutting out the centre section and welding in a much thinner section or creating some ingenious device to machine down my centre section. But right now I think castor is the main problem.
Paul