Anglesey, Trac Mon.

[JohnD]

Qualy just finished.   Engine behaved perfectly!  Fingers crossed, but suggestions re the fragments taken to heart.

The problem is the replacement diff.  My Quaife, I have used for years - it was in Silverback - ans i was very happy with it, but the Silverstone incident damaged the casing, so I replaced it with an original Gareth Thomas (!!) locking diff that had been on my shelf for years.    

Maybe I'm getting used to a different type of diff, but I span in practice THREE times!   The last on the corner into the start/finish straight.  Next time around, they 'black'n'white' flagged me.     I came in and they told me that my inside wheel had been in extreme positive camber.   In other words, I was 'jacking-up', the traditional.failure of the Herald/Vitesse swing axle!

I've inspected the rear axle, all is tight where is should be, and loose where it shouldn't.   Nothing else has changed, so this has to be the effect of the locking diff.  Too abrupt transfer of power to the outside wheel, compared to the more graduated efect of the Quaife.   I'll have to adapt my driving style.

Anyway, Trac Mon is a wonderful circuit, views over the sea to the Cambrian Mountains and Clubhouse/bar that stays open until 2230!   Long curvy bits where I can get up into fifth gear and 100mph, and some very twisty bits like The Corkscrew, named after the Laguna Seca corner and very like it.

Video will come after I get home.  Now to double check the car!

John

Edited July 21, 2024 by JohnD

[JohnD]

And...

Bugger!

That's my left front, the 'attacking' wheel on this clockwise circuit.   All the others are OK.  Yokos are directional so I could change it for the rear on that side,  but not safe whatever axle it's on.

So an early bath, I'm afraid.  I'll withdraw and get home today.

More negative on the front, I think!

John

[Nick Jones]

Holy crap….. how much understeer?!

Which bit of your Quaife diff casing is damaged? Rear casing is pretty easy to swap….

Definitely a big contrast between the Quaife behaviour and conventional plate diff. Remember Alan’s Vitesse gave me a couple of brown moments at CC when I tried it and I wasn’t going especially hard. Though Alan reckoned it was because I wasn’t going hard enough! 
 

Does sound be like yours might be set on the aggressive side though. Their behaviour can be altered. Yours sounds like it might be more suited to gravel stages!  Might be inducing additional understeer and contributing to the tyre wear?

positive camber on the inner wheel (at full droop) is a normal roto geometry thing - actually helps keep the tread flat on the road. Do you have a rear ARB?

[Hamish]

Sorry to see and hear this John. 
 

the front wear is strange and seems very evenly spaced around the tyre

would this correspond with and “hopping” at the rear ?

[JohnD]

Thanks, guys!

All four of the small socket headed  bolts that secure the output shaft into the body were knocked out!   Some remained in the diff body, but I was able to remove all but one.  Might need drilling out, perhaps with a reverse drill.  Easy enough to replace, but after all that I'd rather have 'my' gearbox man go over it before I use it again.   As said, this is a Gareth Thomas product, but I would rather not go back to him for many reasons, nit least he lives in Russia?

I used to have a rear ARB on the Silverback.  I adapted a Peugeot 205 one, but it malfunctioned at one meeting, I took it right off, and couldn't tell the difference!  Unlike this!

Yes, that front left is worn like that  all around the outer shoulder.    I didn't flat spot it anywhen - although, there was a chirp as I braked for the hairpin at Barbon last week, but I thought that was the rears.

John

[Nick Jones]

As regards the plate lsd you are using now, it might be worth talking to Paul Hughes at 2 Spec Transmissions. He’s a Triumph person who knows about these things. Might help if you know what kind of lsd it is though?

[JohnD]

Thanks, Nick!

[egret]

14 hours ago, JohnD said:

 

 although, there was a chirp as I braked for the hairpin at Barbon last week, but I thought that was the rears.

 

In the first video you shared of the Barbon you can just make out the rears locking up as the video pans between 9 and 10 seconds.  A useful tip that I didn't know about until recently is that youtube allows you to move frame by frame (or at least small intervals) using the "," & "." buttons.  You can move frame by frame and see the rears stop turning. I make it 11 frames out of 30, so about 1/3 of a second, so pretty good reactions there!

[JohnD]

It was my front that shredded, so no harm there then.   Thanks for the video tip!

John

[Escadrille Ecosse]

Well shreded there John. Obviously trying.

Good man. Just a shame it brought the proceedings to a premature end.

The heavy six out the front makes the front outer work hard @Hamish, even more so with the Vitesse, especially on full chat and somewhere like Anglesey where there are big speed variations round the course. And some tarmac surfaces are more fierce than others. Long time ago but I thought Anglesey was a bit like Kames up near me. Very hard on tyres in the dry. Even more so when it's actually dry and warm.

I've raced Spitfires with locking and Quaife diffs in swing and roto flavours. Actually preferred the locking diff on full chat as it felt more predictable although the Quaife is fine on the road unless you forget it's not a locker.

Mine is a Gripper LSD. As Nick says they are adjustable. Spoke to them when I was buying it, wanted to know what the car was used for, how heavy, engine power, which axle, etc. Set up with ramp and preload to come in fairly gently and works very well on tarmac.

But very glad the engine held together.

[JohnD]

As I told above, I retired early from the practise, after having several 'moments', including full spins at Rocket (the uphill left 90 degree at the end of the long curved 'straight') and just after the Corkscrew on entry to the Start/Finish straight.     I hd been shown the Black and White flag ("You have a mechanical problem") after the last, and a scrute told me that my rear axle had been in extreme positive camber  In other words, I was 'jacking-up' the known and notorious failing of the Triumph swing axle rear suspension.   I retired early,  because I felt sure that something  was loose.  But a check in the paddock found all was tight and correct.    

Jack-up has never been  problem for me for years.  I was sure that my mods to the rear axle had abolished it, but now that I'm using a  clutch-based diff, it's  returned , big- time.     So why?    I'm still struggling to to edit the GoPro video of practise, but meanwhile the excellent David Stallard, the pro-photographer who follows the CSCC events, has provided several pics that seem relevant.

Here I am entering the S/F straight, turning left.  Significant roll, but NO positive camber

And here:

Shortly before the previous, turning right in the middle of the Corkscrew, rolling to the left, but left rear wheel planted.  No positive, or negative camber.

I have to believe the scrute who advised me, so what's going on?  Is it my new and different diff?  Do I need to have that adjusted?  Or adopt a different  driving style?   I'll be grateful for your thoughts!
 

JOhn

 

[Nick Jones]

11 hours ago, JohnD said:

I have to believe the scrute who advised me

Why? Pictures suggests he’s talking bollocks. Did he actually see it, or is he just “interpreting” what he was told by others and applying (irrelevant in this case) swing axle prejudice?

Quite a bit of roll and weight transfer in the first pic, but that’s the iron 6 for you (and what eats your front tyres)

Worth checking rear toe settings but it could simply be the diff action being too violent and unsettling the car.

[Escadrille Ecosse]

Agree with Nick. I suggest the scrutiny doesn't know what he's talking about. 

A rotoflex rear end can't adopt 'extreme positive camber' unless it's falling off.

 

[Hamish]

I’ve had discussions with a very keen scrute - as Marshals had reported ……..

I just asked if he was stopping me taking to the track on their opinion .. he backed off and spun it as just letting me know …

so don’t take it as gospel. 
Were there many cars behind you with video you can look at John ?

[JohnD]

Hadn't thought of that, Hamish!  Perhaps I can ask through the CSCC.   This would be a good use of Facebook, as people do post on the CSCC page there.   And Daughter shows me, there is an active Spartans Owners Club page too!

I do have my own video, still in the editing room, that I must remove all the boring bits from and leave the exciting moments and spins, to elicit your analysis, please!

But I have a houseful of family this weekend, so later!

John