Millie antiroll bar

[milliemarlin]

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.

Wow! How did you do it? Any chance you could machine mine?
Paul

[milliemarlin]

Re: Millie antiroll bar

I had a private message giving measurements. This indicated a difference between near side and off side. So I have checked my nearside. It matched the dimensions given. So it seems I have 262 on the offside 270 on the nearside.

I found myself laying on my back staring up at the ARB and wondering if I was going over the top on this. After all I lived with the original set up for years. I bet 95% of my driving is straight ahead. But it was quite a bit better to drive and getting this right is an interesting challenge.
Paul

[greyV8pete]

Re: Millie antiroll bar

Wow! How did you do it? Any chance you could machine mine?
Paul

Made a special hand tool. It took about one hour per 2mm so sorry not in a hurry to repeat it!

[greyV8pete]

Re: Millie antiroll bar

I had a private message giving measurements. This indicated a difference between near side and off side. So I have checked my nearside. It matched the dimensions given. So it seems I have 262 on the offside 270 on the nearside.

I found myself laying on my back staring up at the ARB and wondering if I was going over the top on this. After all I lived with the original set up for years. I bet 95% of my driving is straight ahead. But it was quite a bit better to drive and getting this right is an interesting challenge.
Paul

There is an error in the position of the ARB pads on all the Cabrios that I have checked. Therefore likely also present on the chassis jig. From memory mine was 10mm different. However the position of one of the top ball joints was 5mm different the other way, so half the error was cancelled out. I still had to machine more off one ARB shoulder though to get the castor equal on both sides. Will try to post some dimensions later tomorrow.

[greyV8pete]

Re: Millie antiroll bar



Some dimensions from my Hunter as promised.


Back of TCA bracket to centre of front ARB clamp bolt
O/S 262mm. N/S 272mm


C/L bottom ball joint (outer TCA) to front bumper datum plane
O/S 465mm N/S 455mm


C/L top outer ball joint to front bumper datum plane
O/S 465mm. N/S 471mm


C/L ARB D-bush to C/L outer TCA compliance bush
O/S 402mm. N/S 407mm


Castor angle degrees original
O/S 11deg N/S 9deg


Castor angle after first* O/S ARB shoulder 5mm m/c back
O/S 7deg N/S 9deg
Note* Done originally to get castor same both sides. Eliminated previous tendency for car to always pull to the left!


Castor angle after latest further O/S ARB shoulders m/c back
(Target m/c back O/S 1.7mm. N/S 5.1mm)
O/S 5.8deg N/S 6.0deg


Above calculations and m/c work based on every 1.7mm ARB shoulder cut back giving estimated 1deg castor change.


Important Note! It is essential when removing metal from the ARB shoulder to use a cutter with at least a 0.5mm radius to match the original! A sharp corner here must be avoided to prevent stress raising weakness! Also the cutter face next to the 16mm diameter needs to be backed off a couple of degrees to avoid removing any metal from the existing diameter surface.


Hope all this helps. Peter.

[milliemarlin]

Re: Millie antiroll bar

I mentioned earlier that I thought I needed to move the ARB back 30mm then I had second thoughts. This is my attempt to calculate the required change.

This is a view on the driver’s side hub.

Hub view.jpg

The blue centre line shows the current angle 12°. I can’t find a definitive answer to what the castor should be. The racing community seem to think 10° to help keep the tyre on the ground as it deforms round a corner. But then I stumbled on a document detailing the 1987 Sierra RS Cosworth rally car set up for Donaldson, McRae, Lovell, Blomqvist, Vatanen and, Auriol . They generally used 4° depending on the surface; Tarmac, gravel or Big Jumps. Perhaps not best suited to my style of driving, especially the big jumps. Incidentally, I also notice the ARB was 1 in. Dia. X 14 swg.

I also found this list, I have added the curb weight in brackets: Renault Clio II 2.1° (990 kg), Citroën C5 3.1° (1,537 kg), Audi A4 3.4° (1,410 to 1,730 kg) , Peugeot 307 4.6° (1176 kg), Volkswagen Touran 7.5° (1,436 to 1,603 kg). I had a theory that heavier cars had more castor. This was because the Sierra ARBs increased the castor in the order 3 door (1040 kg), 4 door (1270 kg), Estate (1,435–1,611 kg). The list sort of confirms that but I think other factors such as intended drivers and power steering must be an influence. My guess is that a heavier car will deform the tyre more on heavy cornering and the angle compensates for that.

I note that the Clio is closest to the weight of Millie but reviews of that car’s handling use words like “nothing to write home about”, “handling can seem blunter and less entertaining” and “expense of handling sparkle”. Perhaps not the best model even if closest to my driving style.

So I’m still undecided on the ultimate angle. I would welcome input on what others have used. With my sedate driving style, I haven’t even done a small jump in Millie, so I guess somewhere from 3 to 6 degrees would be fine, preferably nearer to 3° for a lighter feel.

On the diagram above the red centre line shows 6° and the green 3°. To get 3° I need to move the bottom swivel joint back 30mm hence my original estimate. I would like to move at least it 20mm. What I hadn’t taken into account was the ARB is inboard on the TCA. As shown in this plan view of the TCA.

TCA view.jpg

Using the same colour scheme blue shows the current position, red 6° and green 3° of castor. Because the TCA is a classic lever the ARB only has to move back between 14 and 21mm on the off side. The near side is already 8mm further back so an adjustment of 6 to 13mm is required. Using my pre-bent estate car ABR the off side at 313 should have 14mm machined off (320 – 21 = 299). The near side starting at 325 18mm machined off (320-13 = 307). As a minimum to get 6° I need 7mm from o/s and 11 n/s machining off.

Some other possible fixes are:

Weld on new mounting plates. Not easy to remove the old ones without damaging the chassis. It would not be easy to weld up the holes and extend the existing plates and re-drill further back.

Make a bolt on adaptor: using a 15mm thick bar make an adaptor. The adaptor would bolt on to the existing mounting with counter-bored holes to allow a flush mounting surface. The ARB mounting surface and holes are reproduced in a better position. The ARB will sit 15mm lower but I don’t think that will affect its operation. I quite like this idea as it can be reversed if everything goes pear shaped. But having four sets of bolts per side is unsatisfactory, something of a bodge.

Pack out the upper wishbone brackets: The bolts are not very long and my camber is not good, especially, on the driver’s side. I have a hope that modified ARBs will improve my camber.

Bend the ARB: Not easy to do. One possibility is to take to a blacksmith or similar and get it heated up and bent. Not easy to do accurately even with a template. I suspect the bar would still need machining to finished size.

Any other ideas?
Paul

[milliemarlin]

Re: Millie antiroll bar

Some dimensions from my Hunter as promised.
<snip>
Hope all this helps. Peter.

Outstanding! Thank you Peter. A big help.

How does she drive?
Paul

[milliemarlin]

Re: Millie antiroll bar

I’m going to refit the compression strut.

Madness! MADNESS! I hear you cry.

I’m one of those people who keep paper and pencil beside the bed because I sometimes wake in the night with a solution to a problem. The ideas come into my head like methane bubbling up in an alligator swamp. I have been mulling over the best castor angle. I had been trying to invent a way to make the ARB adjustable. But it’s occurred to me, at 03:37, I have the perfect way to adjust the angle to discover the optimum. I will refit the compression struts and test the driving experience over a range of angles. This will give me a target angle for the ARB. Once the angles are common I can compare the independent compression struts to the connected ARB to see if it makes much of a difference.

The only problem with my cunning plan is that there limited driving experiences on the Island, nothing over 60mph, nowhere to cruise at speed.

It may be a few days before I can get going on this.
Paul

[milliemarlin]

Re: Millie antiroll bar

I’m going to refit the compression strut.

<snip> I will refit the compression struts and test the driving experience over a range of angles. <snip>
Paul

The best laid plans...

A cancellation freed up some time so I was able to refit the compression strut. The bad news is even in its most screwed in position the offside castor is 8°. Lummy Dickens*!

This has put a damper on my plans. Am going to have to remake the carriers just for the test?

In other news I turned up a bolt to take the guess work out measuring the centre. It’s still not easy to measure especially when holding a camera. But it looks like the offside is 268.5 and the nearside 272 giving a difference of 3.5mm, not nearly as bad as I first thought.


O-S length.jpg N-S length.jpg


Paul
*I may have used a stronger expletive.

[cabrioman]

Re: Millie antiroll bar

Paul did you look at the information Mike Garner put on the forum after he had his cabrio set up at a suspension specialist in lincoln area. I think he ended up dialing in around 4 - 6 degree castor, which involved cutting down the compression strut to get to that.

I am sure the struts Mike used were the same or very similar to yours, so you would have thought you should be able to achieve the same unless your chassis mountings are in a different place. Are you sure your castor readings are accurate, are you using a castor gauge or calculating it from triangulated measurements.

All the setups Mike used are documented on the forum.

[milliemarlin]

Re: Millie antiroll bar

Paul did you look at the information Mike Garner put on the forum after he had his cabrio set up at a suspension specialist in lincoln area. I think he ended up dialing in around 4 - 6 degree castor, which involved cutting down the compression strut to get to that.

Thanks John,

I did read it when it was posted but I’m glad you reminded me.

The page is here:

https://www.marlinownersclub.com/forum/showthread.php?4589-Mike-s-Cabrio-Build/page3

He uses 6°. I really wanted to check the feel of low angles. I think I could machine the strut down 4 mm to get 6° but if take off 9 to get 3° the locknut will be off the thread. I’m looking a combination of machining down and slotting the mounting holes. Not a long term solution and will devalue the resale value of the struts.
Paul

[greyV8pete]

Re: Millie antiroll bar

Thanks John,

I did read it when it was posted but I’m glad you reminded me.

The page is here:

https://www.marlinownersclub.com/forum/showthread.php?4589-Mike-s-Cabrio-Build/page3

He uses 6°. I really wanted to check the feel of low angles. I think I could machine the strut down 4 mm to get 6° but if take off 9 to get 3° the locknut will be off the thread. I’m looking a combination of machining down and slotting the mounting holes. Not a long term solution and will devalue the resale value of the struts.
Paul

I wouldn’treccommend much below 6deg or it will be too “twitchy”. Compbrake sell the arb end brackets separately, so you could always buy a new pair if it enabled you to sell on the compression struts! Peter.

[milliemarlin]

Re: Millie antiroll bar

I wouldn’treccommend much below 6deg or it will be too “twitchy”. Compbrake sell the arb end brackets separately, so you could always buy a new pair if it enabled you to sell on the compression struts! Peter.

The strut has been sacrificed. I probably wouldn’t get much for it anyway and I couldn’t give it to a Marlin owner.

As I was sawing 10mm off the end I thought at 3° I was probably going to find out why rally drivers mark the centre position on the steering wheel. In the event it wasn’t too bad – more on my findings later. On three degrees the locking nut had less than two threads to grip on but there is a second at the back and there was little risk of things coming apart on such a short journey.

I have set the garage up like a pit. I take her out for a spin round the track and return where a 12 man crew in yellow and black fire suits change the caster angle and reset the toe in. The whole process takes 7m 23s but we are getting that time down. Oops I slipped into a fantasy world for a moment. With just me in the garage it takes a while to run a test.
Paul

[dcunn]

Re: Millie antiroll bar

If you make a video of your fantasy game I'll buy a copy

LoL

Good Luck, wish I had your patience/persistence

Rgds DC

[kahawi]

Re: Millie antiroll bar

If it involves, preferably using only two pieces of string, a plank of wood and a school rule, can you please explain how I can measure camber, at home in the garage?

Advice much appreciated, Colin B.