barry.h Posted April 11, 2005 Share Posted April 11, 2005 If any of you have, or are considering, changing your A-frame axle mounting from rubber bushes to a rose joint then do please be aware that it does set up a new set of stresses. I made this change last year. On Saturday, at Loton, as I braked from about 90mph the central housing on the A-frame (the bit that contains the rose joint that is bolted to the bracket under the axle) split in two leaving the axle free to rotate partly and to move from side to side. Luckily this pulled the propshaft splines out so I lost drive as well. What is now clear to me is that the rubber bushes as well as allowing the necessary axle movement also acted to cushion acceleration/deceleration shocks whereas a rose joint transmits those shocks directly to the A-frame. Suffice to say I have gone back to the rubber bush arrangement. Barry Link to comment Share on other sites More sharing options...
Coose Posted April 11, 2005 Share Posted April 11, 2005 I take it that your prop shaft didn't pop out completely!?! You were very lucky..... We will mend it We will fix it... Link to comment Share on other sites More sharing options...
barry.h Posted April 11, 2005 Author Share Posted April 11, 2005 No it's a Blackbird engined car so the rear propshaft has a slider which is splined but doesn't actually separate - luckily!! Barry Link to comment Share on other sites More sharing options...
deanteam Posted April 11, 2005 Share Posted April 11, 2005 Which tyres and approx how much power do you have this is also relevant. Link to comment Share on other sites More sharing options...
Bare Posted April 11, 2005 Share Posted April 11, 2005 As a Digression ...remember reading that the early Jaguar C types had an A Arm axle locator.. Didn't actualy believe that Chapman invented this did You? Turns out their Arm was breaking with regularity.. Seems the Salisbury axle employed was strong enough to resist the forces imposed on it, so the A Arm suffered and ied. Seemingly not quite the case with the Triumph/Ford units inna 7. Jaguars quickly developed/deployed their IRS system in response to the problem. More useless info to clutter yr memory with :-) Link to comment Share on other sites More sharing options...
Nigel Riches Posted April 12, 2005 Share Posted April 12, 2005 Barry, I was interested to read this thread as I had the bracket under the diff housing break off, but that was when I had the original rubber bushes installed, and also when braking in reverse, I subsequently changed to Rose joint A frame and have not had any further problems, but I don't cane it on the track, just road use for me. Anyone else had this failure under track racing conditions? 1982. 5 speed, clamshells. B.R.G / Ali. The True Colours. Link to comment Share on other sites More sharing options...
barry.h Posted April 12, 2005 Author Share Posted April 12, 2005 Deanteam, Running 175/530 R13 slicks, around 175bhp and a car weighing 385kg. The slicks will certainly create more strain although presumably the light weight will offset this slightly? Nigel, the diff housing bracket is stronger than the standard one so I guess the next weakest point was the A-frame itself. Barry Link to comment Share on other sites More sharing options...
Gary-Cornwall Posted June 29, 2005 Share Posted June 29, 2005 I'd welcome any more experiences with the rose jointed A frame as I'm considering it. CC said they couldn't comment on the effect of moving stresses elsewhere as it was not really tried and tested. Link to comment Share on other sites More sharing options...
Violet Elizabeth Posted June 30, 2005 Share Posted June 30, 2005 When I spoke to Chris at the Seven workshop about rose-jointing my A-frame he advised against it for this very reason. He suggested replacing the rubber bushed with poly ones instead. The (slow) birth of the Gixxerham : Pics here now with extra drivel here Link to comment Share on other sites More sharing options...
deanteam Posted June 30, 2005 Share Posted June 30, 2005 Both our sevens have the rose joints and so far no negative effects. One has been fitted with this ca 4-5 years?, has ca 160bhp, LSD and uses ACB10s mostly trackdays (Le Sept), Second fitted 2 years, 135bhp, LSD, 032/048 more sedate trackdays and road. Former has rose jointed dampers, a good idea, latter not yet.. Having said that I hope the cars survive this years Le Sept!! Link to comment Share on other sites More sharing options...
Revin Kevin Posted June 30, 2005 Share Posted June 30, 2005 Hi all, I have been running a rose jointed A frame for ten years, mostly very hard road use with sticky tyres, never had a problem. I have got a beefier axle bracket though. Cheers Chris Link to comment Share on other sites More sharing options...
andy couchman Posted June 30, 2005 Share Posted June 30, 2005 Hi Barry My first (standard Caterham) axle had quite a thinnish metal diff mounting but its Graham Sykes replacement had a much haevier gauge arrangement (and big holes in the bracing bar at the back of the axle). Don't know if that might make a differenmce? Andy PS Glad the consequences were not too bad Link to comment Share on other sites More sharing options...
barry.h Posted July 1, 2005 Author Share Posted July 1, 2005 Clearly a mix of experience but worth keeping an eye on perhaps. My problem was not the axle bracket but the A frame itself; the housing for the bushes where it joins the axle bracket. Cheers, Barry Link to comment Share on other sites More sharing options...
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