Cutting wishbones

[lewist123]

Hello gang

I have been re-envigorated with the skoda recently and should be pumping in some big time to get it done soon.

Anyway, one slight bugbear that I have is that I can't wind on enough camber on the front wheels to tuck the top of the wheel into the arch (running zero offset 8" wheels) and to match the rear. There is camber adjustment, but just not enough now that the front has been lowered.



Here is the front double wishbone front subframe



So I think that I have to following options.

1) Re-engineer the top wishbone mounts so that more camber can be dialed in
2) Take a thin sliver out of the top wishbone and re-weld them back together

Now, I am currently leaning towards option 2, as I think it would be the safer option. Re-engineering the wishbone mounts won't be easy due to the mounting points etc and might require more of a bodge to make it work.

If I trimmed a, say 10 mm, sliver out of the top wishbone and welded them back together I could also add some additional plating to the sides to increase stiffness.

Remember that the top wishbones are only acting in tention or compression.

Anyway, a penny for your thoughts!

Lewis

[westy180]

Could you weld up the outer holes in the top wishbone and redrill them further inboard?

[lewist123]

Jul 21, 2011 21:09:05 GMT westy180 said:

Could you weld up the outer holes in the top wishbone and redrill them further inboard?

Possible, but the current holes are punched with flaired edges, giving a nice meaty area for the bolts to bear. If I just redrilled the holes the bolts would be riding on a metal edge.

I forgot to mention option 3) Don't do any of the above, and leave well alone.

[westy180]

Make some steel bushes up to reinforce the holes?

Weld thick washers either side of the wishbone to beef the metal up.?

Scratches head.

[bl1300]

I think id be leaning towards option 3.

That is a safety critical part do you really want to be messing with it?
Judging by the thickness of my own wishbones it going to be asking a lot of most hobby welders to penetrate all the way through and if it doesn't your setting up stress points for crack propogation and ultimatly fracture

I also hate to think what fun the plod would have if you had an accident in it afterwards.

[lewist123]

^ Wisbones are pressed 3 mm steel plate, so no issues getting a good quality weld.

Option 4 is to get some rose joints and tube and make new tubular top wishbones (also forgot to mention that option in OP)

Lewis

[bl1300]

Jul 21, 2011 21:23:48 GMT lewist123 said:

^ Wisbones are pressed 3 mm steel plate, so no issues getting a good quality weld.

Option 4 is to get some rose joints and tube and make new tubular top wishbones (also forgot to mention that option in OP)

Lewis

The quality of the weld was my main concern especially given that the wishbones on my own car are about 20mm thick

[westy180]

Looking at your pic it would seem that the lower wishbone is the one taking the suspension loads were as the top one is more for location. Is that right?

[lewist123]

Indeed.

As with most double wishbone suspension the shock and spring act on the lower wishbone. That is the one that does the hard work. The top wisbone only really controls camber, takes some lateral loads (in the tention and compression plane of the wishbone) and helps to act against rotational braking forces.

[BiAS]

Lewis, Are the wishbones bolted to bushes on the subframe? I can't really figure what's what in the picture. How about offset polybushes for something else on the top and bottom arms, top in, bottom out to achieve the neg. Or maybe offset bolts for the outer pivots? If they're similar dimensions to these?

[ChrisT]

I'd be tempted to go with the redrilling route
Drill the holes oversized and weld in some tube so the bolts can't crush the arm.

[lewist123]

Ok some good input.

For BiAs, here are a few more pictures of the top and bottom wishbone mounts.

Some rusty, pre-referb pics.



The top wisbone, at the subframe end, contains rubber bushes and a long steel shaft passes though the bushes into a clamping block on the subframe. The claimping block bolts down to the subframe with bolts, shims and slotted holes.

At the hub end, there are bushes and excentric bolts to fine tune the camber.



The subframe



The bottom wishbones fix again via bushes to a clamping block that bolts to the bottom of the subframe. I could more the lower wishbone pivots out fairly easily, but that wouldn't really help tuck the top of the front wheels in much.

Slotting the mounting holes and welding on washers/tubing is an option that I hadn't previously considered. I will measure the diameter of the bolts and see if I have some tubing of suitable quality and dimentions/suitable washers.

Thanks

Lewis

[Dez]

looks liek a dead easy job to me. chop and weld. depends how good your welding is really. if youre not confident or don't have the correct gear, get a pro to do it. id have no issue with cutting and welding them.

[lewist123]

^ yay A response that I was looking for

I have a 150 amp mig running a full size argon/co2 mix bottle. I have been practising a lot recently (gathering project) and I am confident that I can lay down some decent meety welds.

Having looked at the pics, the wishbones are pressed and the bottoms open (although I knew that already, but had sort of forgotten). I recon that if I chopped and welded the upper wishbone back together I could then plate over the open bottom with some 3 mm plate to close the 'box' and they would be stronger than they were before.

I know this might sound like I am only listening to the advice that follows my own ideas. Sorry about that, but I am fairly confident, given the other options, that this one is the best all round way of doing it. Whether it should be done is another question, obviously!

Lewi

[scaryoldcortina]

I think you'll do fine. I agree about the extra boxing to make it stronger than it was, I do that sort of thing too (not just me, check the beardmore brothers builds....)

Only bit of advice I can offer really is measure twice, cut once

[lewist123]

^lol yeah. I really will make sure I measure about 10 times before I cut anyting, if indeed I do go for it.

Lewis

[Seth]

I think I would look into moving those outer wishbone to upright holes in first before chopping the "meat" of the wishbone down.

Grind the exisiting load spreading tubes down flush, weld up the holes, make new holes to suit new tubes that, if necessary, were made from solid in a lathe* to suit. That way you're basically replicating the original set up in a virtually undetectable way. Chopping up the wishbone and keeping it all square would seem like more work to me.



*_{Can't remember if you have access to one but you know someone who does...}

[ejenner]

Put a little bit of a 'crank' on the upper wishbone to hub bolt. That's how OEMs get camber adjustment.

Here's how they do it on the Subaru Impreza. It's an OEM part so you should be able to get them cheap enough from any breaker. Might need a bit of shaving here and there to get it to fit. If you find they aren't big enough then weld some extra metal onto them. Better to start with something which is nearly there rather than making something from scratch. If you find the bolts are rotating after they have been installed and tightened then just weld a flat onto the side of the bolt and a corresponding flat onto the wishbone.




I wouldn't cut the wishbones. Welding weakens the metal around the weld sometimes. My car snapped the shock mount off the wishbone and I have seen plenty of bent wishbones over the years. They take a real beating.

[lewist123]

^ That is what it has already got, but it only allows about 1 degree of adjustment.

Seth - I will drag my spare set of wishbones out of the shed (btw I also forgot to mention that any mods will be done to the spare wishbones/subframe I have so I can always hit the undo button) and have a look. You might get a PM in the near future

Thanks for all the advice guys.

Lewis

[ejenner]

To get more camber the Subaru guys then elongate the loop this bolt fits through on the hub or on the end of the wishbone. Would be much better than cutting and rejoining the wishbone.