STEVE GILBERT Posted January 11, 2001 Share Posted January 11, 2001 Having recently ripped the A Frame mounting bracket off my Diff which resulted in the prop exploding through the xmission tunnel and the Axle twisting/ Diff Flange burying into the tarmac causing a big spin and near crash,I have paid more than normal attention to said Bracket.I notice that the A frame seems to move a fair ammount on the rubber bush on the Diff.Anyone else noticed this and how often are you Live Axle owners changing this Bush? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
Casbar Posted January 11, 2001 Share Posted January 11, 2001 I am changing my bushes about twice a year, that is with very little track use. If the bushes need changing, you usually hear a knock from the rear, when accelerating fast. Rgds, Robert Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 11, 2001 Author Share Posted January 11, 2001 Do you see this same lateral movement of the Axle as me after say a succession of R/Handers noticable by more compression of the Bush to one side? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
deanteam Posted January 11, 2001 Share Posted January 11, 2001 The life of the bushes is greatly reduced if oil leaks on to them. Do you fit the smaller bushes with the larger metal insert ? We have not noticed any wear bias left to right. On one of our cars we have replaced the rubber bushes by a spherical bearing. After 1 year's heavy use this seems the best solution. Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 11, 2001 Author Share Posted January 11, 2001 Deanteam, I'm on Caterham supplied bushes and was not aware of different types although I was aware of oil contamination. Are you describing a Rose type joint?I like the idea but shock loading would worry me. Are you on a Std Arch Motors Diff Bracket or is that modded as well? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
I.Mupferit Posted January 11, 2001 Share Posted January 11, 2001 Anybody know if you can get poly-bushes for the 'A' frame bracket. They would be less susceptible to degradation from oil contamination. Brent Link to comment Share on other sites More sharing options...
Mike Bees Posted January 11, 2001 Share Posted January 11, 2001 But would the stiffness of the polybushes cause the bracket to break off rather more often? It's only the compliance of the bushes that allows the car to roll with respect to the axle without tearing the bracket off. Mike Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 11, 2001 Author Share Posted January 11, 2001 Definately one of my concerns, In other circumstances my bracket failure could have been more nasty, as is was I came soo close to collecting the car beside me.This must be an old problem? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
tgracing Posted January 11, 2001 Share Posted January 11, 2001 I am changing my bushes every two races or so on my Academy (now Grads) car. The left hand one tends to get more sh*gged than the right (no surprises there then), so I sometimes swap them over if the left hand one is not too bad (Scrooge - moi?). I was told the A-frame was designed so that the bushes were a weak point and throw away so as to protect the axle. Not checking/replacing the bushes removes that 'insurance'. Davebo C7 CAR Link to comment Share on other sites More sharing options...
deanteam Posted January 12, 2001 Share Posted January 12, 2001 Yes it is the rose joint type. I have heard that to replace the rubber with the rose joint would negatively effect the bracket, but our's has survived last year, which included Le Sept(multi-drivers!), 3 trackdays and road driving. We also changed the shock absorbers to Leda with spherical bearings as well, I don't know if this also helped to reduce the loads. I think that the rubber bushes (when new!) must put some twisting loads into the bracket as the wheel move up and down(or body rolls). The total handling of the car has improved tremendously from the previous Spax-gas set-up. Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 12, 2001 Author Share Posted January 12, 2001 Deanteam,given the movement I,m seeing it can't be good for the geometry and I'm not seprised you see handling Improvements. I wonder if when designed the rubber bush was just the most simple/cheap solution? Did you lop/weld the A/frame or fit in the Eye somehow? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
John E Posted January 12, 2001 Share Posted January 12, 2001 If you read Tony Weales book the above subject is covered in some detail along with axle bracing.He comments that Caterham investigated the use of Neoprene and a spherical bearing but concluded that the gain in roll stiffness was balanced off by additional strain on the outer mountings and diff bracket. Caterham concluded that the throw away Y16 bushes are the most satisfactory under different operating conditions. The book recommends replacement every 6k miles but I change mine every 3k. If there is an oil leak issue then life of these bushes will be significantly reduced. If any one wants a copy of the relevant pages then let me know. There is also a diagram of the Spherical bearing set up. I will need a fax nmumber. Edited by - John E on 12 Jan 2001 13:08:52 Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 12, 2001 Author Share Posted January 12, 2001 Didn't think this could be anything new and would like a look at the book..Fax 01206 369849 All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
John E Posted January 12, 2001 Share Posted January 12, 2001 Its on its way Steve Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 12, 2001 Author Share Posted January 12, 2001 John E, thanks, I'm assembled with a 1/2 x 3/4 washer betweem the Y16 bushes as per latest build manual.Am I reading that right as this diagram is not showing it? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
John E Posted January 12, 2001 Share Posted January 12, 2001 It must depend upon the bracket and distance between the flanges. Mine has just the two bushes as per the diagram. It is also possible that it depends upon the axle. Mine is a Ford. It seems that yours is using the washers as spacers which would point towards a different bracket size. When I fit new bushes I have to compress them into the bracket. Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 12, 2001 Author Share Posted January 12, 2001 Same here,I needed washing up jiz.The 2 bushes+washer are exactly the width of the Brackett.I reasond that without the washer when I tightend the bolt it would stress the Bracket rather than clamping the metal Inserts in the Bushes but I may be wrong and I dont have the Manual to hand. All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
Aidan Parte Posted January 12, 2001 Share Posted January 12, 2001 Steve Exactly the same thing happened on my live axle Caterham about 5 years ago. It was pretty hairy! When I had the car repaired, I had the bracket strengthened by welding steel plates (approx. 4 mm thick) either side of it, so the nut goes through the bracket and plates. I believe this is extremely strong and is no longer anything to worry about. Owners who change their bushes frequently probably need to be more concerned about this, as sometimes leverage is required to get the bushes in. I tried some poly bushes a couple of years ago, and they worked very well for good while - but when they did start to deteriorate, they broke up very rapidly indeed. Link to comment Share on other sites More sharing options...
John E Posted January 14, 2001 Share Posted January 14, 2001 Steve, I'm sure that you have done the right thing by including the washers. If I compress slightly the two bushes with a pair of mole grips then in they go with no problem but I have learnt over the past twelve months that each of these cars is different. I changed the bushes on another car last year and that vehicle did not have a braced axle but was sporting a 195bhp Zetec engine.OOOOOOOOOOOOHHHHH mother. Link to comment Share on other sites More sharing options...
bl0498 Posted January 14, 2001 Share Posted January 14, 2001 Steve, Definitely don't bother with the non-Caterham bushes - as Mike Bees correctly says the bushes are intended to be the weak and wearing link in the rear suspension - and at a couple of quid for a pair, hardly expensive. What I did find with my live axle car was that torqueing up the bolt seemed to stress the ears of the bracket unduly by bending them inwards once the bushes (and the internal washer) were compressed. I have to say my only remedy for this was to be gentle and not torque up to the Caterham recommended 40lb/ft but to torque up to the point the ears were just starting to bend. Like most of the above I routinely replaced the bushes 2 or 3 times per season - it only takes 15 minutes! Hope it helps. Brian Link to comment Share on other sites More sharing options...
tgracing Posted January 15, 2001 Share Posted January 15, 2001 When replacing my bushes I use a pair of adjustable pliers to compress one edge of the bushes (at the top). The whack them from underneath with a Fine Adjuster or whatever is closest to hand when I forget to bring the damn hammer under the car with me. On occasion I have managed to compress the bushes by hand enough to get them in. When orignally assembling the a-frame i used a vice to compress the bushes (overnight) in the a-frame and then fitted it to the car. Not practical for a roadside change really though. wink.gif Definitely put the washer between the the bushes. Use washing up liquid if you like. Use a medium screwdriver to align the bushes in the holes so that the bolt will go through without having to whack it with the F.A. My record is about 5 and half minutes. Cheers, Davebo. Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 15, 2001 Author Share Posted January 15, 2001 Well thanks to all for your comments, it's nice to know other people have A-frame and rubber fun! All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
John E Posted January 15, 2001 Share Posted January 15, 2001 You've got me thinking now about the spacing washers. My bracket fittment does not have any washers inside the flange, its exacly as per the diagram in the Weales book. Does anyone else have such a fittment or are you all using washer spacers. I have to add that the bracket on my axle probably wouldnt allow for any additions. Link to comment Share on other sites More sharing options...
STEVE GILBERT Posted January 15, 2001 Author Share Posted January 15, 2001 John E. My Brackett came from Arch and was 2 halfs spot welded, I suspect in a jigg, so I think they should start out the same size.When welded to the Axle it must resist a mere 40lbft without bending and although a squash the washer is only 3mm ish, you could try fitting it? All.Knowing1@talk21.com Link to comment Share on other sites More sharing options...
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