Snapped upper wish bone bolt

[normspanners]

On the escorts they where fine with polybushes as they where 'slippery' it was the harder than standard competition rubber bushes that caused the issue, especially with the group one pinto engined car where you had to use normal uprated ford bushes because of the extra weight of the cast engine which caused the issue, the nylocs where easy to fit but slackened off, the castellated with split pins where fine and used to tighten and 'grip' the split pin but never sheared it, to remove the split pin you had to tighten slightly first. all that was caused by the rubber bush being forced to compress under suspension movement and braking.
I even tried locking the two 3/4 unf nuts together to prevent it and it failed.
this is one reason manufacturers have gone to void bushes, to help prevent the extra torsion of a solid bush i do realise noise and harshness are also the main factors btw.

 

[normspanners]

Regarding the comment earlier about serrations in the bush tube - I've never seen one with serrations - they would simply smear flat I would think. I looked at the picture and thought they were indentations from something like a nordlock washer - now they take some undoing when fitted correctly!

It's also very important to remember that metalastic bushes work by the rubber twisting, but because the rubber is bonded to the metal, it will only move so far before running out of movement (going solid). For this reason, it is imperative that these bushes are not torque tightened until the wheels are under their own weight. At this point you tighten the bolts which then locks the bushes to the wishbone brackets, and then they have the maximum amount of travel in both bump and droop directions before the rubber locks-out.

2.2 Nylon bushes

A much more performance-orientated wishbone bush is nylon. Unlike the metalastic bush, they come in 3 parts as opposed to 1. Each bush is made up of a steel crush tube (just like what is at the centre of a metalastic bush), and two nylon pieces which are shaped like a top hat with a hole through the middle. The way in which nylon bushes work is different though. Instead of rubber being used to deform and permit movement, the movement is provided by the crush tube being allowed to rotate within the nylon. The crush tube is a precision fit for the nylon, and a bearing is effectively formed. The crush tube remains fixed, while the nylon (and wishbone) rotates around it.

The two nylon top-hats are pressed into the wishbone bush housing at either end, and then the crush tube passes through the entire assembly. The crush tube is marginally longer than the combined length of the nylon pieces when pressed into the wishbone. As a result, when fitted the crush tube is bolted tightly against the wishbone mounting bracket which locks the crush tube into place. The wishbone and its nylon inserts are then free to rotate around the crush tube. The faces of the top hats will be very lightly in contact with the face of the wishbone brackets, but this is to prevent the bush twisting in a way it shouldn't.

The end result is an almost frictionless wishbone motion, with virtually no deformation or undesirable geometry movement due to the nylon being solid. There is also no increase in rate, unlike metalastic bushes. This makes it a very desirable choice for track cars.

To avoid complicating the rubber section too much, I thought I would mention this here instead. One of the problems with using rubber in motorsport is the rate that it adds to the suspension. As mentioned in the metalastic section, the twisting of the rubber permits the wishbone to describe an arc, therefore allowing the wheel to move up and down. For this reason, it’s very important to torque the wishbones up when the car is on the floor at normal ride height. Sometimes, you may even want to do this with the driver weight on board to so the bushes truly start with zero load on them.

The rubber operates just like a spring, in that it has it’s neutral setting (e.g. spring at full length), and when you move it, it will always resist in an effort to get back to its natural setting. The more you compress a spring, the more it fights you. A 200lb/in spring will push back with 200lb if you compress it 1 inch, and 400lb if you compress it with 2 inches etc.

A rubber bush does exactly the same – the more twist you put into it, the more it pushes back to try and untwist. So this means as your wishbone travels up, the overall rate of that wheel is increasing more and more. Furthermore, when coming out of the corner, that bush unloads its force back at the wheel in rebound.

Depending on your exact setup, and the firmness of the rubber, this may or may not be a problem, but it’s worth pointing out. It means the bump and rebound damping will have a different level of effectiveness depending on where the wishbone is in it’s arc.

 

[normspanners]

Just another point re strength of rubber whilst resealing a largish hydraulic cylinder many years ago the end gland that screws into the cylinder had an o ring around it to seal it, that o ring had been supplied incorrectly metric instead of imperial and was a few thou thicker, as the gland screwed in it came to a point where the gland would NOT, turn even with a 5ft chain wrench with a pipe on it, I unscrewed it several times thinking it was another fault with the thread or some such n ever time the same place it went solid and a long way from going 'home', i eventually found the slight difference in the o ring and replaced it and it screwed by hand till the final tightening tweak now that was an just an o ring not bonded to either part and lubricated, so do NOT underestimate the power of compressed rubber.

 

[PhillipM]

To avoid complicating the rubber section too much, I thought I would mention this here instead. One of the problems with using rubber in motorsport is the rate that it adds to the suspension. As mentioned in the metalastic section, the twisting of the rubber permits the wishbone to describe an arc, therefore allowing the wheel to move up and down. For this reason, it’s very important to torque the wishbones up when the car is on the floor at normal ride height. Sometimes, you may even want to do this with the driver weight on board to so the bushes truly start with zero load on them.

The rubber operates just like a spring, in that it has it’s neutral setting (e.g. spring at full length), and when you move it, it will always resist in an effort to get back to its natural setting. The more you compress a spring, the more it fights you. A 200lb/in spring will push back with 200lb if you compress it 1 inch, and 400lb if you compress it with 2 inches etc.

A rubber bush does exactly the same – the more twist you put into it, the more it pushes back to try and untwist. So this means as your wishbone travels up, the overall rate of that wheel is increasing more and more. Furthermore, when coming out of the corner, that bush unloads its force back at the wheel in rebound.

Depending on your exact setup, and the firmness of the rubber, this may or may not be a problem, but it’s worth pointing out. It means the bump and rebound damping will have a different level of effectiveness depending on where the wishbone is in it’s arc.

Sorry, but this is wrong, the reason harder bushes are used in motorsport is to control geometery under high loads, the massive downside of poly or nylon bushes is the fact that they introduce static and dynamic friction issues into the suspension - this is effectively uncontrolled damping that changes massively depending on the load on the arms and how much preload is on the crush tube and the faces of the bush where they contact the chassis lugs. It's worst right where the suspension is changing direction, which is where most of your driver inputs come in (turn in, acceleration, braking, etc) so it upsets chassis balance and confidence.
Ariel Atoms had a big issue with this when they were first built because someone put solid bushes in the suspension rockers, it led to poor ride quality and the car handling changing with different conditions/wear. They swapped them out for roller needle bearings to solve the issue eventually, after a customer that was clued up realised and made a kit to sort it out.

Rubber bushes flexing are a much prefered option but the issue is getting the suspension travel out of them in stiff enough compounds to control the geometery - the spring rate change you mention is a non-entity - who cares if the rubber bush has a 25lb/inch spring rate, you take your 200lb/inch corner spring, add them together and you set the damping for 225lb/inch, you can control it, it doesn't matter in the scheme of things. Now, try setting your damping when the friction in your bushes is adding 25lb one way, then the other direction when you reverse it, and it jumps up to 50lb every time you go over centre, or 200lb if you're braking hard and the load has increase on the bush...
This is exactly why F1 racers don't use rose joints or nylon bushes any more, they have flex joints much the same as your rubber bushes in a road car, albeit far stiffer made out of carbon, because then there's almost no friction to deal with.

If you could get rubber bushes hard enough to control the geometery and still flex enough to cope with the travel required I'd be throwing so much money at you you'd think it was snowing, as it is we have to settle for a mix of Poly, Nylon/Delrin and rose-joints depending on what suits the area, and then we spend dozens of man hours per car perfecting fits just to get as little friction as possible with enough preload to keep the joints tight, and you still have to fudge the damping to guess how much friction is going to bugger up your low speed valving settings.

 

[normspanners]

??

new arm has been delivered looks fine to me the bolts on either end are tight so I think I will leave them alone and see not sure it is a nylock now or if it is blue thread lock. Any way i just stuck it in a vice and rotated it to how the old one was ready for fitting at the weekend probably now

Just as a matter of interest, was the nut that slackened on the near side, the foremost nut ?

 

[octo0072000]

should not have been able to turn it in the vice so the nuts are not doing what they are supposed to do
inner metal sleeve of the bush should be locked to the centre bar.

 

[123hotchef]

well that is not the case no wonder they are loosening the nuts. The old ones wont budge in the vice I nearly ripped the vice off the bench trying!

 

[daedalusminos]

It looks like you have two 'spacer' washers on the 'axle' inboard of the wishbone, are these serrated? With the nylocs torqued to the correct spec and if you still get movement in the vice, at which interface is movement occurring? I would make sure you sort this off the car rather than just fit and forget.

 

[123hotchef]

the whole rod turns in the bushes with it clamped up in the vice, no the washers are not serrated

 

[normspanners]

the whole rod turns in the bushes with it clamped up in the vice, no the washers are not serrated

could you explain this better is the rod turning in the crush tube or is the crush tube turning in the bush ?------ and also answer my question i have asked twice re which nut slackened on the nearside

 

[normspanners]

Sorry, but this is wrong, the reason harder bushes are used in motorsport is to control geometery under high loads, the massive downside of poly or nylon bushes is the fact that they introduce static and dynamic friction issues into the suspension

Well in my view it is not wrong some suspension setups use just the rubber bush as the 'spring' and use the rubber as a natural damper, rubber can be incredibly hard to twist when bonded to steel and encapsulated in a tube most polly bushes will allow the item to twist within its self quite easily, nylon especially but nylon doesn't give enough shock absorption, but can introduce rattle into the setup, well for rallying an off roading etc. poly bushed wishbones can be lifted by hand to any position and stay there whereas rubber has to be forced away from its natural at rest position and in fact to get ball joints out a large bar has to be used, that force has to be transmitted to the chassis and the fasteners at the end of the crush tube.
we are after all talking about an off road vehicle here, not a formula 1 car, and the two are TOTALLY different.

 

[8ob]

Those two washers on the inside of the fulcrum forging are a possible problem, if they are not welded/fixed/attached to the fulcrum the serrations on the bush will turn them which will then put the strain onto the outer serration`s and washers. Basically the inner washers if not fixed are as good as bearings.

Just thoughts.

Bob

 

[normspanners]

which will then put the strain onto the outer serration`s and washers.

and then ----the nuts !
thats the dogs ... btw

 

[normspanners]

new arm has been delivered looks fine to me the bolts on either end are tight so I think I will leave them alone and see not sure it is a nylock now or if it is blue thread lock. Any way i just stuck it in a vice and rotated it to how the old one was ready for fitting at the weekend probably now

how and why would this need to be done ? it should be set ready to fit or at least if not set, it should state what you should do to fit it? methinks it has come incorrectly set then fitted and that is the issue.

 

[daedalusminos]

Those two washers on the inside of the fulcrum forging are a possible problem, if they are not welded/fixed/attached to the fulcrum the serrations on the bush will turn them which will then put the strain onto the outer serration`s and washers. Basically the inner washers if not fixed are as good as bearings.

Just thoughts.

Bob

My thoughts exactly, I was prompting the hotchef to investigate further. But it's important to have the nuts torqued to the specified (actually I would go slightly lower than specified torque to begin with).

 

[doubleboost]

If the nuts are torqued up now are the bush inner sleeves gripped so that they spring in the rubber
If that is the case just fit the arm with the nuts slack
Put the weight on the suspension (jack under bottom arm)
Then tighten up the nuts
If you "bounce" the suspension the nuts should move with the arm

 

[123hotchef]

could you explain this better is the rod turning in the crush tube or is the crush tube turning in the bush ?------ and also answer my question i have asked twice re which nut slackened on the nearside

sorry mate the front nut on both slackens off, the rod is turning in the tube what do u mean by crush tube are the tubes suppose to crush or is it to stop the bush crushing

 

[123hotchef]

My thoughts exactly, I was prompting the hotchef to investigate further. But it's important to have the nuts torqued to the specified (actually I would go slightly lower than specified torque to begin with).

I cannot find a torque setting for these nuts in the workshop manual funnily enough

 

[123hotchef]

Well in my view it is not wrong some suspension setups use just the rubber bush as the 'spring' and use the rubber as a natural damper, rubber can be incredibly hard to twist when bonded to steel and encapsulated in a tube most polly bushes will allow the item to twist within its self quite easily, nylon especially but nylon doesn't give enough shock absorption, but can introduce rattle into the setup, well for rallying an off roading etc. poly bushed wishbones can be lifted by hand to any position and stay there whereas rubber has to be forced away from its natural at rest position and in fact to get ball joints out a large bar has to be used, that force has to be transmitted to the chassis and the fasteners at the end of the crush tube.
we are after all talking about an off road vehicle here, not a formula 1 car, and the two are TOTALLY different.

Actually it is a L200 used for work and play and towing 2 horses so it has to be right

 

[normspanners]

If you "bounce" the suspension the nuts should move with the arm

I dont think so John?, the nuts are at the end of the the through shaft which is bolted to the chassis if they moved with the arm that is why they undid

sorry mate the front nut on both slackens off, the rod is turning in the tube what do u mean by crush tube are the tubes suppose to crush or is it to stop the bush crushing

ah from your photos it looked like the rear nut on the OS !! if the front nuts then it is braking that is slackening them IMO as the wish bone tries to spread under load.
the tube in the middle of the bush are called crush tubes, called that because you crush them up tight between the end nut and the thickened part of the through shaft which is bolted solid to the chassis, the tubes are locked solid onto the through shaft by the nut to lock them into final position to prevent them slackening the nut and prevent the inner crush tube rattling on the through shaft , the tubes dont actually crush up (in the fact of getting shorter) they prevent the nut crushing and locking the rubber.
But as has been said above those parts I think MAY be delivered/ supplied with the nuts 'slack ish' AND A NOTE SHOULD BE IN THE PACKAGE TO STATE --- that when fitted, the arm is allowed to move the crush tubes into there 'neutral running position, so the car should be dropped into its normal running height, whilst sitting on flat ground,---- THEN and only then should the end nuts be tightened to prevent undue loading on the through shaft and associated washers and lock nuts.