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front ARB drop links/fitting
Wingnut - 20/3/05 at 10:05 PM

All,

Does anyone have any advice or opinions? I'm really stuck for ideas with my replica GT40!!

I'm struggling to find a suitable space to connect the ARB drop links to my front wishbones.

I figure they need to be fitted as far outboard as possible on the lower wishbone. However, the steering arms are very much in the way, as are the track rods & dampers!

There would be room to connect to the top wishbone but I'm not sure if this is a good idea??. If anyones got any ideas/pictures I'd be most grateful!

I'll probably end up making the ARB, but haven't got a clue what type/size of steel to use.. again, any help gratefully appreciated!

THanks in advance!

Mark Allanson - 20/3/05 at 10:20 PM

There are dozens of production cars which have drop links on the ARB's, why bother to calculate your own stresses when a manufacturer has done all the maths for you.

Try a Peugeot 106 for size, dead cheap with a proper balljoint on either end.

RogerM - 20/3/05 at 11:57 PM

The maximum roll stiffness you should gain from ARBs on a road going car is 1/3 total roll stifness.

There is no reason why the bars can not be attached to the top wishobnes, so long as the joints that attach them to the uprights are man enough to deal with the loads that is.

There are so many GT40 replicas out there that there must be a well established size and construction of ARB that can be copied at either end (assuming your car is of normal wieght and using typical spring rates that is).

If you are looking for cheap drop links for ARB's I'd look at those from the front of a 97 on Passat ..... long, strong and properly jointed. That front end is VW at there very best.

britishtrident - 21/3/05 at 07:46 AM

Quite a common way of fitting arb was to connect them on to the bottom eye of the spring-damper unit using a special bolt

The shank of the bolt would be 7/16" or whatever as normal but on the head there was a 3/8" shank for the rose jointed drop link to the arb.

NS Dev - 21/3/05 at 08:47 AM

quote:
Originally posted by Wingnut
All,

Does anyone have any advice or opinions? I'm really stuck for ideas with my replica GT40!!

I'm struggling to find a suitable space to connect the ARB drop links to my front wishbones.

I figure they need to be fitted as far outboard as possible on the lower wishbone. However, the steering arms are very much in the way, as are the track rods & dampers!

There would be room to connect to the top wishbone but I'm not sure if this is a good idea??. If anyones got any ideas/pictures I'd be most grateful!

I'll probably end up making the ARB, but haven't got a clue what type/size of steel to use.. again, any help gratefully appreciated!

THanks in advance!


There is no reason not to connect to the top wishbone, as long as you feed the loads into an area which will take the bending load that you will put on the wishbone.

I use plain CFS (cold drawn seamless mild steel) tubing for my anti-roll bars. 4130 (chrome-moly alloy steel) tubing would be better but mild steel is fine and a lot easier to deal with!

I make the bar and the "blades" (the cranked ends) in one piece by bending the steel tube.

I use short homemade links with rose-joints each end for the droplinks, and for the roll-bar bearings, either off-the-shelf "Stauff Clamps" (hydraulic pipe clamps, like they use on digger booms to mount the rigid pipework) or a bored out and sliced in two block of Nylon, if there is no Stauff clamp the right size. (Usually there is as most of the small diameter CFS tube on the market is destined for hydraulic line!

As for tube dimensions, depends on the weight of the car, roll centres, springrates etc but assuming you have an iron block v8 in the back, and that this is for the front, I'd try around 21mm OD (ish) by 3.5mm wall (ish) (err to the thicker wall and bigger OD side of this when you order the tube. ( I know that 21.43mm x 4.06mm CFS is available as a std size as we buy a lot at work, (I think it is 27/32" x 5/32" originally!)

Hope this is of help

Wingnut - 21/3/05 at 12:44 PM

Thank you all for the information, all of which is a great help.

NS Dev, thanks for the advice on tube, It's great to have a starting point to work from.

I'm looking again at mounting points for the drop links & may be able to mount off the lower wishbone after all.

Here are a couple of pictures showing the steering on full lock either way..

Wingnut - 21/3/05 at 12:52 PM

OK, no image!?!

it's here;

http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=21-3-05%20(30).jpg

and here;

http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=21-3-05%20(31).jpg

NS Dev - 21/3/05 at 02:00 PM

looking at those, could you not just squeeze the droplinks in between the shocker and the front half of the upper wishbone? Looks like it would clear? If bodywork permits you could then mount the arb on top of the chassis with the "blades" bending backwards to a point above the gap between the shocker and the front tube of the upper wishbone?

NS Dev - 21/3/05 at 02:07 PM

The only point I haven't made is that I don't know the front to rear distribution of weight in your car, and if it is anything like an Ultima (I guess it will be similar) then the tube I have mentioned may be a bit on the thick side, but as long as the blades are adjustable (i.e. the droplink to blade mounting can move along the blade), that shouldn't be a problem.

I am just wittling to myself now, cos I know v8 mid engined GT cars can be blighters to get to turn in, and the least thing you want at the front is too much roll stiffness in that situation, you need all the grip you can find!

Bob C - 21/3/05 at 02:50 PM

Another system to consider is that it's a perfectly viable alternative to mount the ARB ends directly (via pivots/balljoints) to the lower wishbones and have the droplinks between the chassis and ARB.
I'm personally not that keen on using upper bones to take suspension loads because the ball joint has not been designed for forces along the direction of the bolt, but at right angles to this. However the ARB is not holding the whole weight of the car!!!
Hope that makes sense!
Bob C

britishtrident - 21/3/05 at 03:59 PM

quote:
Originally posted by Bob C
Another system to consider is that it's a perfectly viable alternative to mount the ARB ends directly (via pivots/balljoints) to the lower wishbones and have the droplinks between the chassis and ARB.
snip snip snip
Bob C


Thats how Lotus did it on the original Elan except Chapman took it one stage more and simply welded a bolt shank on to the bottom eye of the shocker to act as a spigot, this stuck down through the bottom of the wishbone and the ends of the arm had a suitable eye that fitted on to the spigot via standard shocker top mount rubbers.

Wingnut - 21/3/05 at 08:12 PM

Again, interesting ideas, Thanks guys!

NS Dev, uncanny, you are spot on about the mounting of the ARB. The chassis has mounting points in that position & I'll certainly hope to use them. As regards turn in, the car handled so badly before it was difficult to tell what was going on!

The standard weight distribution with the driver, fuel & fluids included was 44.5% front 55.4% rear & the car weighed 1122 kg (1147 without driver!).

I've made considerable weight savings, especially in the front, so weight distribution maybe affected accordingly altho much of the weight saving at the front is unsprung. I've also made lots of mods to the rest of the car during a bare chassis rebuild.

As suggested here, I may try & fit the drop links off the lower damper bolt & see if it clears, great idea!