UN1 13 gearbox prime shaft upgrade

[Fred/Belgium]

I once again broke my standard primeshaft this weekend (second time this year) and I am considering installing an upgraded kit.

Is there anyone having one they are willing to sell ?

My engine is a 302 mexican block with arround 380HP,clutch is AP racing.

Tx
Rgds
Fred

 

[Scott Calabro]

HI Fred/GT40,

Contact Andy Sheldon at TSC in England. He can provide you everything you need to make sure that never happens again.

Cheers,
Scott

 

[Malcolm]

We had an interesting discussion at the club AGM this morning about busting gearboxes and drive shafts etc. One theory put forward (which I didn't get but others with more knowledge seemed to support) is that if you use a smaller diameter multiple plate clutch on a standard Renault box you are far less likely to get breakages. The evidence put forward is from Rodgers 500+ bhp big block car using a small diameter triple plate clutch on a bog standard UN1 box except with Quaife ATB diff. He runs slicks and does competition starts with it. Never broken his box yet. So whilst you fix your box, maybe worth considering the clutch element at the same time.

 

[Fred/Belgium]

Tx Scott and Malcom.

Seems like I have some time to work during the long weekend.

Rgds
fred

 

[BruceA]

We had an interesting discussion at the club AGM this morning about busting gearboxes and drive shafts etc. One theory put forward (which I didn't get but others with more knowledge seemed to support) is that if you use a smaller diameter multiple plate clutch on a standard Renault box you are far less likely to get breakages. The evidence put forward is from Rodgers 500+ bhp big block car using a small diameter triple plate clutch on a bog standard UN1 box except with Quaife ATB diff. He runs slicks and does competition starts with it. Never broken his box yet. So whilst you fix your box, maybe worth considering the clutch element at the same time.

Over in the Transaxles thread, Paul Thompson talks of similar things. I cannot see why this is myself, as the small diameter, multiplate clutches have the sticky kevlar/ceramic disc faces which are somewhat 'grippy'. They have no sprung centre hub, or marcel spring to soften takeup. He may just have a somewhat 'tortionally flexible' input shaft, or his driving technique offers a degree of mechanical sympathy.

 

[Jac Mac]

Two thoughts on this;
1. The liteweight clutch assy might reduce the rotating weight of the crank/flywheel/clutch assy enough to reduce the failure rate( I was going to say prevent, but thats not likely!)
2. If the smaller clutch means that he breaks traction, rather than attempting to ease the clutch engagement to gain max traction, it is easier on the driveline. Of course individual car setup is a factor as well, if the car has a lot of anti-squat plus full rear tire tread contact it might break parts,where a car set up for optimum corner speed( neg camber )might not.

Jac Mac

 

[Paul Thompson 'Hooligan']

hmmm - interesting this one...

I initially figured that there might be something in the 'dia' being important, but now I'm not so sure.

My figuring was that, let's say an engine produces 500ftlb of torque, if you dump that across a clutch that's half the diameter of another one, then the smaller clutch with efectively a shorter (clutch radius) mechanical advantage will present less of a load to its output (trans input) shaft....

However, I then thought about the initial figure of 500ftlbs and then figured that this measurement IS SPECIFYING the diameter already, i.e. 12". so having a 6" dia clutch is no difference because the 500ftlbs becomes 1000 half-ftlbs...? - is this correct?

Apologies Fred for the thread drift! - I hope you manage to sort your gbox soon and if you do get an upgraded unit, you'll not regret it I'm sure...

So the theory of a smaller multiplate clutch softening the torque to the trans probably goes out the window...

I should also say that I never thought that the 'snatchy' nature of the metallic multi-plate was an advantage, it's just the nature of most units. If you break traction, it becomes irrelevant because measured torque levels would then be lower anyway. When Roy's original shaft broke, we were hard on the gas in about 4th/5th gear approacing Fordwater at Goodwood. There was a couple of bangs, (each time we lifted) and then on the third bang, the shaft sheared. Looking at it afterwards you could see from the cross-grain where the initial couple of bangs had probably partially craked the shaft, as there was a slight polishing sea-shell like look to two segments and when it finally broke a couple of laps later, the final section was just a dull grained area...

Still can't quite understand though how Rodger's 'std' UN1 quill has not broken??? - Of course he might be trying a 'sneaky-pete' (read Malcolm) and maybe he's actually fitted a DB conversion already that we are not aware of?.... No, probably not....

Anyone else...

Sorry for the thread drift Fred, if you do get an upgraded unit I'm sure you'll not be disappointed...

 

[Paul W]

There were a few adaptor shafts (Ford - Renault) made out of the wrong metal and subsequently failed early, a friend of mine infortunately got one in his build. It worked fine for a short period. Mine has so far been ok and I've done a few days on the track and about 12k miles in it - std mustang clutch and flywheel.

 

[Fred/Belgium]

Paul

tx and dont worry, I always appreciate your expertise anyhow.

Rgds
fred

 

[Fred/Belgium]

Folks,

Connection part between prime shaft and secondary (to the engine) went bust.
Chris Cole helped me out to understand the issue.

Thanks for your expertise and ongoing support.


Rgds
Fred

 

[rick]

fred contact d.bell he make upgrades UN1 Index page

 

[BruceA]

Folks,

Connection part between prime shaft and secondary (to the engine) went bust.
Chris Cole helped me out to understand the issue.

Thanks for your expertise and ongoing support.


Rgds
Fred

Ahhh thats the dreaded splined sleeve. Yes, this wee peice of French ingenuity has only about 1/3 of the splines actually cut in it. It is designed to fail before anything else in the engine (in theory). And while Im speaking about theories, this 'sleeve' allows the primary shaft to 'flex' in extreme conditions, eg: the primary shaft is supported in 2 bearings and 2nd gear breakage is where the shaft flexs in the middle so the gearteeth ride up and break off. The 1-peice shaft more-or-less makes this a 3 bearing shaft as any flexing is now resisted by the crankshaft bearing.

 

[Fred/Belgium]

Chris Cole helped me to understand there are 2 type of dreated splined sleeves made of 2 different metals.The one wich is more shining than the other is a stronger one.

I ll try it this way (and have a spare tx to Chris) before moving to a fundamental upgrade investment...

Thanks to all of you for the valuable support.

Fred