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MG Midget and Sprite Technical - Negative camber trunions
|Looking for a pair of Negative camber trunions that take poly bushes. Aldon used to make them in alloy but don't have any and have not for years. Does anybody else make them or has anybody got a used/unused pair or will I just have to use the solid style that seem to be all that are available now.|
|Peter Mays trunnions have solid bushes, I removed mine,and reverted to standard trunnions as they were shaking my fillings out. Not sure if you can somehow remove the solid bushes and fit poly bushes, of even if the size would be the same.|
Negative camber lower arms would solve the problem (because they would still use poly or rubber bushings in all of the usual places).
Sadly, Barry King used to make negative camber lower arms, but he has recently retired and so they are no longer available until someone with some heart, like MGOC, or BMH coughs up some funds to purchase the jigs and tooling from him. He is selling off his remaining stock of standard arms now.
He made the very best arms in the business, I am disappointed that the MGOC hasn't jumped at the chance (I can understand Moss not bothering because they already have their Chinese source (or Indian, or whatever) who makes, "good enough" arms, and probably there's more profit in it, for them).
|I bit the bullet and made my own offset trunnions because I wanted to use poly bushings AND I needed different offsets on each side to end up with the same amount of camber on each side.|
|Hi Norm , Just fitted a new pair of Barry king arms , the last but one pair left. so cant go down that route, I thought somebody in USA made offset trunnions to take polybushes any body confirm that?|
|YOU CAN STILL GET NYLATRON BUSHES WITH AN OFFSET FOR ADJUSTMENT TO FIT THE STANDARD TRUNNION - MOSS I THINK.|
|Nylatron is about as hard as bronze, for all practical purposes, so it wouldn't help OP|
|I've used standrad rubber, nylatron and solid bronze bushes and prefer the nylatron - not as harsh as bronze.|
|It's possible to modify a set of polybushes to fit the Peter May Engineering negative camber trunnions. However, the real solution would be for someone to have a batch made that are an exact fit.|
|When I made mine, one of the more aggravating issues was the tapered bore for the stock rubber bushings. However, If I had known that I'd definitely be using poly, then I suppose I could have just used a straight bore.|
|Moss still list the offset nylatron bushes, part No: TMG309621, but also advise that, |
"Nylatron bushes are not recommended for road use unless you are willing to accept an increase road noise and a harsher ride, they must also be fitted carefully to ensure the correct working clearance is obtained - and they must be inspected on a regular basis.....
....Nylatrons strength does mean that we (Moss) are able to offer the top trunnion bush with an offset drilled centre hole, this allows the suspension camber to be adjusted. The fitting of nylatron bushes is best left to someone with engineering experience."
Hope this helps
Here is a pic of the rare little beastie you are after.
I purchased a pair of these from Aldon in 1978 IIRC. They gave many years of good service on various cars.I still have them and they may well get used again.
Two years ago I asked Allan Goodwin of Aldon if he recalled these negative camber trunnions, he said yes but Peter May bought all the drawings and rights to them (and all his other Spridget parts too).
I think that they are far more suited to road cars thn the solid trunnions offered by PMay.
IMO they would be fairly easy to make in these days of CNC machines as they are not complicated at all, and could easily be machined from solid (once the program is written)
Another source you might want to investigate is Rae Davis Racing, he was advertising recently adjustable negative camber trunions. I have not seen any, if any one has a decent photo of one hopefully they could post it, Daniel may have info.
|Ian Webb '73 GAN5|
|Here is a view from the top showing the difference (standard trunnion on the right)|
I measure the extra spacing to create neg camber to be 1/4"
|Ian Webb '73 GAN5|
|Another pic, with the standard trunnion in the middle, Peter May type solid trunnion on the left and the alumimium Aldon trunnion on the right. All on the same shaft to show the difference clearly.|
|Ian Webb '73 GAN5|
|I think the RAE davis one's are the old MOTOBUILD adjustable offset bronze bushes.|
|When I made mine I moved the bushings up for clearance, but I also run 14 inch rims. I machined them from 12L14 steel.|
|i'm quite unsure about the offset bushes. what's to stop them ofsetting the other way?|
I cheated and bought the last pair of -ve camber bottom wishbones from BK. Double winner as it makes the track wider as well :)
|These are the old Motobuild brass offset bushes.|
They may well be like the RDR ones as you say ?
|Ian Webb '73 GAN5|
|As Rob suggests neg camber wishbones is probably the best way to go, gives about 1/2" extra track as mentioned.|
Unfortunately NLA from BK, but here is an example.
|Ian Webb '73 GAN5|
|Why cant the trunnion be treaded and a thick pipe installed then redrilled for the offset|
Or just have a machine shop / cnc make them out of a large chunk block of ally aluminum...then just grind off any edges for foul clearancing...ugly but doable id think
|Prop and the Blackhole Midget|
|Hi Ian , Don't think you will ever find a use for those old Aldon trunnions . I can provide a good home for them!|
Excellent information and photos!!
I have a Bridgeport mill and could make those Aldon types, I think. Would you be willing to take a bunch of measurements for me?
Hole diameters. centerline offset, counterbore depth, that sort of thing.
If I figure out how to do this, maybe more could be made.
Barry King's longer lower arms would be better, but if they are not available then manufacturing some new Aldon-type, rubber bushing upper trunions would be a decent alternative, I think.
|I think making them from solid bar in the T6 condition would be a good idea to ensure the strength was up to the job and I would also do some calculations on the compressive stress the material is under due to the nut at the top of the kingpin as IIRC the area the kingpin is clamped to the trunnion is quite small. The aldon one looks to be cast so I would almost certainly require heat treatment to get a suitable strength and decent machinability.|
|I'm pretty sure the peter may ones could be modified to accept some form of rubber or poly bush.|
I've used the offset nylatron ones from Moss and they worked ok. They need a bit of fettling to fit and have to be bonded in to prevent turning. I wouldn't use them unless I had to though (I needed one side doing to compensate for a dodgy heritage shell), they don't give you enough neg camber to be worth bothering with the hassle of fitting.
|from looking at Ian's photo, the Peter May shape looks too small to be bored out large enough to be able to accept rubber / poly bushes|
|You could be right Norm, what we need is Peter May to run a modified batch that accept the normal bushes.|
I'm quite happy with the solid ones on mine but I must admit I spend more time looking out for potholes than any other road hazards!!
I will hang on to them for now !!
IMO you are correct to say that the PM trunnions are way too small to be bored out to accept standard shape bushes (at one time I did consider removing the phos bronze bush and replacing it with nylatron, but I still felt that in that critical position it still was not sufficient compliance for a a car used on normal roads)
The original Aldon trunnions are definitely cast in aluminium, reasonably hard and probably heat treated as DB suggests.
I am always shocked when I have the PM ones in my hand they weigh a ton !
I do already have some of those dimensions you need for machining, as I considered having some made a couple of years back. I know where I might be able to have a look at some of the original factory drawings for that part and I want to do that before I make a drawing for to enable manufacturing. I do work in engineering (but not on the machining side) so I do have an idea of whats required
|Ian Webb '73 GAN5|
|Who said anything about boring out Peter May negative camber trunnions to fit poly bushes? I didn't.|
What I did was source Poly bushes the closest match for the Peter May negative camber trunnion and modify the bushes to fit.
John P mentions it 5 posts before this one.
|Ian Webb '73 GAN5|
That is great news, I look forward to whatever you can share. A copy of the original factory drawing for reference too would be awesome!
I have been studying the best way to manufacture those things. Either machine out of a solid billet (but that would take a lot of steps, and set ups, to cut away all the sides). Or, make a CAD drawing of the shape and have it near net cast, and then just machine out the holes and counterbore.
|I can vouch for them taking many steps to machine. In fact, I never finished mine. I had one more step and a finish pass to complete. However, I went ahead and fit them to be sure the fitment was correct. I never finished them because the remaining steps were just to lighten them. Maybe when I decide to finish the car I'll finish the trunnions while the car is disassembled.|
|I'll try and keep up! Having said that I guess Norm also needs to keep up?|
|Or get a Frontline frontsuspension kit(credits to David B.) ;)|
It already has 2 neg. camber build in once installed.
Ian: "I do work in engineering (but not on the machining side)"
Ian, don't think the midevil machines at your work can handle the fine/delicate precision work needed for midgetparts anyway. LOL!
|A de Best|
|Has anyone tried the cheap method of moving the shocks slightly inboard with packing washers or a spacer plate?|
yes, I did (raised the front dampers with 3/8" spacers), and then measured the change in camber and it went from 1 degree positive, to about 0.3degree positive. It did not make it the desired minimum of 1deg negative or anything like that. Not enough to make hardly a difference when driving.
The reason why it doesn't work as well as we'd like is because the mounting surface is angled, so I found that you'd have to raise them a lot to get enough movement inboard to get to worthwhile negative camber.
By the way, I drove it like that for quite a few years, and I can vouch that it didn't harm the handling so I guess there's not much down side to doing it. I just was surprised when I finally did measure it and find so little upside. When I had the front end apart for painting recently, I took the spacers out, since they weren't doing much anyway.
|The Frontline kit only gives 2 degress less negative camber and on a car that has been lowered or wasn't built that fantastic in the factory in the first place, you can still end up with neutral camber on just one or both sides. Then you either need NLA wishbones or a negative camber trunnion or bush etc.|
Polybush could make poly bushes for the Peter May trunnions with a big enough order.
|Just thought I would bring subject back to the top . Still looking for Aldon Trunions or somebody to make a negative camber polybushed version . Peter May are you reading this?|
|TBQH you'd be much better to give Peter a phone call...|
|I've got negative camber trunnions on my wanted list but they'll have to wait a while until a few more of the basics are sorted.|
I use my Sprite in club hill climbs, running it in Class 1A for roadgoing series production cars. My interpretation of the regs in the Blue Book suggests that they would be allowed but can anyone confirm this? I'd rather find out before I spend the money!
This thread was discussed between 23/03/2014 and 03/04/2014
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