Discussion
Another post, I know. Having followed the bible's advice on removing the outer bush sleeve from the wishbones by hacksawing through it, I've found it impossible not to cut into the wishbone itself, in the process of ensuring I've actually cut through the sleeve. Some have gone deeper than others, and although this is not a bearing surface or anything, I am concerned about the reduction in strength of the wishbone as a result, particularly the potential for a stress fracture migrating from the bottom of the cut.
Can someone tell me whether I need to worry about this, and if so, whether getting the cuts tig welded up and ground back would be a suitable solution?
Many thanks in advance.
Can someone tell me whether I need to worry about this, and if so, whether getting the cuts tig welded up and ground back would be a suitable solution?
Many thanks in advance.
One way of reducing the cut is to saw all the way through the sleeve at the external edge, say 3-4mm into the hole but only partly over the rest of the width. Then with a suitable tool (old screwdriver) leaver the flap up a bit, make a few more strokes with the saw and progress like that. If you only cut the bit that is bent up it is possible to minimise the damage to the wishbone, obviously it takes a bit longer. It pays to have a good poke around under the flaking paint and rust to ensure the wishbone is actually reusable before bothering to remove the bushes. Two of mine looked fine but great holes appeared when the rust was prized off.
First ones I did have a cut the entire width I would guess a bit less than 1mm deep and I am not worrying about it. I would think it cheaper to buy new wishbones than have them welded and the welds cleaned up. Also wouldn't like to say what efect the heat of the welding would have on the strength. I think I would worry about that more that the cut.
starmist said:
Great advise, but having already removed my bushes, not much use to me! I just need to know whether I need to weld up the cuts.
IMHO one of the worst peices of advice given. I would never use that method because of the problems that you have encountered. You cannon risk crack propogation and so the only solution is to renew the wish bones. In future if you can't push them out then go to someone with a hydrualic press. And to think that this advice appeared in Sprint...
Yes and I would agree with you if I had actually suggested cutting into the wishbone.. but if you were to read the source material in the bible, the description actually says don't cut into the wishbone and that using a hydraulic press and/or blow torch is the normal method.
It actually states that the cuts should be made deep enough to help fracture the bush and remove it with the aid of a chisel or similar tool. It states that the cuts should not be made into the wishbone itself for the reasons previously described.
This technique was shown to me by an old mechanic after I had struggled for several days. in the 1970s and in several discussions with current mechanics, it is still used when the previous techniques has failed. The key point is that you have to be careful and inspect frequently but it can be done.
Having used a hydraulic press, it is also no guarantee of success as the edge that the bush provides is usually thin and it is not unknown for this to deform and damage the inside. Once this happened... it is out with the hacksaw or replace the whole wishbone.
If it is a couple of slight marks on the edge then I would grind them out. If they are inside and deep I would weld and bore it out to be on the safe side.
As for this being the worst bit of advice given... I would agree if I had actually said cut into wishbone. I didn't and the book frequently states to take care and don't cut the wishbone. It also says that this is a job that I would suggesting leaving to others to do.
Steve
www.tvrbooks.co.uk
It actually states that the cuts should be made deep enough to help fracture the bush and remove it with the aid of a chisel or similar tool. It states that the cuts should not be made into the wishbone itself for the reasons previously described.
This technique was shown to me by an old mechanic after I had struggled for several days. in the 1970s and in several discussions with current mechanics, it is still used when the previous techniques has failed. The key point is that you have to be careful and inspect frequently but it can be done.
Having used a hydraulic press, it is also no guarantee of success as the edge that the bush provides is usually thin and it is not unknown for this to deform and damage the inside. Once this happened... it is out with the hacksaw or replace the whole wishbone.
If it is a couple of slight marks on the edge then I would grind them out. If they are inside and deep I would weld and bore it out to be on the safe side.
As for this being the worst bit of advice given... I would agree if I had actually said cut into wishbone. I didn't and the book frequently states to take care and don't cut the wishbone. It also says that this is a job that I would suggesting leaving to others to do.
Steve
www.tvrbooks.co.uk
Quite. Well, it's all relative, isn't it! I take your point about the article in the bible, Steve. Perhaps I wasn't being careful enough, but at least what little engineering knowledge I have alerted me to the fact (albeit bolt upright in bed at 3 am this morning) that there may be some stress fracture issues with the cuts.
I am confident that a nicely tig welded fill, ground down to approximate the orginal (not so important with the polybushes) will restore any lost strength.
I am having them shot blasted first as this should show up any other areas that need work whilst I'm having the welding done, or even if it's worth getting it done, if they prove to be in that bad a shape.
I'm also going to have penny washers welded over the anti roll bar bush holes on the lower rears so I can fit rose joints and threaded bar front and back. This probably won't make a huge difference until I sort out the main arb bushes, which will be the next handling job once it's all back together.
BTW can anyone recommend a good place to get the geometry set up in the Midlands once it's back on the road?
I am confident that a nicely tig welded fill, ground down to approximate the orginal (not so important with the polybushes) will restore any lost strength.
I am having them shot blasted first as this should show up any other areas that need work whilst I'm having the welding done, or even if it's worth getting it done, if they prove to be in that bad a shape.
I'm also going to have penny washers welded over the anti roll bar bush holes on the lower rears so I can fit rose joints and threaded bar front and back. This probably won't make a huge difference until I sort out the main arb bushes, which will be the next handling job once it's all back together.
BTW can anyone recommend a good place to get the geometry set up in the Midlands once it's back on the road?
I think your approach is fine and I think I will stress the care needed a bit more in the next edition. I try to get the balance right but it can be difficult.
The penny washer trick is not a bad idea but make sure it is a thick washer not a thinish one as I have seen those distort with the ARB loading. I used a 6mm thick plate on the 520. Maybe a bit of overkill but they can be some pretty high forces involved.
The penny washer trick is not a bad idea but make sure it is a thick washer not a thinish one as I have seen those distort with the ARB loading. I used a 6mm thick plate on the 520. Maybe a bit of overkill but they can be some pretty high forces involved.
shpub said:The only problem I thought I might encounter is that bolting the 8mm rod directly to the wishbone means it can no longer maintain the correct angle to reach the arb that the bushes allow, i.e. as the wishbone rotates, the rod will describe an arc. It this a problem, or does the rod just flex as necessary?
I think your approach is fine and I think I will stress the care needed a bit more in the next edition. I try to get the balance right but it can be difficult.
The penny washer trick is not a bad idea but make sure it is a thick washer not a thinish one as I have seen those distort with the ARB loading. I used a 6mm thick plate on the 520. Maybe a bit of overkill but they can be some pretty high forces involved.
I take on board your comments re thickness. I would looking at 14swg ms.
joospeed said:
I've used the hacksaw-cut version of doing bushes succesfully for 24 odd years of working on cars, never had a crack-failure of any description after cuttin bushes out.
I think you're quite safe
But were you more careful than me about cutting in to the wishbones?
I'll in touch in a bit regarding my bush order and the rod ends.
When I rose jointed the drop link on the 520, I provided three axis of movement so that as the ARB moved the rose joints were not moved out of their degree of alignment. I machined various big yokes to do it.
Rod ends do not like much side movement and if they are loaded and beyond the side movement, they will break relatively easily. The TVR system provides a lot of movement by using ball joints so controlling or compensating for this movement is a lot easier than a rose joint equivalent which has some restricted movement.
Rod ends do not like much side movement and if they are loaded and beyond the side movement, they will break relatively easily. The TVR system provides a lot of movement by using ball joints so controlling or compensating for this movement is a lot easier than a rose joint equivalent which has some restricted movement.
Cheers, Seasider! Got my wishbones back from shot blasting, and looking good. The two lower front wishbones both have very badly corroded rcaes, but my local welding company are going to replace them whilst they are welding up the cuts and welding in the washers.
Only cost £15 for the shot blasting. No wonder the engineering industry is going up the swanny. They're too cheap!
Only cost £15 for the shot blasting. No wonder the engineering industry is going up the swanny. They're too cheap!
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