Concentric Clutch Slave

[ChimpOnGas]

Brerabit said:

I know CCRs are commonplace on modern vehicles; but do they work better when designed in from the outset with possibly lighter clutch’s? Is a retrofit with the TVR clutch a bigger challenge?

I guess its a case of horses for courses Malcolm

On this one its easy to argue the pros and cons either way, you can't deny most modern stuff went over to a concentric clutch slave a long while back to the extent its now become the industry standard, but equally those who favour the easy field repair of an external slave have a pretty compelling argument too.

I looked closely at the concentric slave idea when I had Lloyds fit a new clutch five months ago, again they advised against it, I listened but if I'm honest cost was an additional deciding factor and then there was all the horror stories of very short concentric slave life and expensive gearbox out fixes from the Cerbera and "T" car crowd.

Once I'd weighed up all those pros & cons I ended up sticking with the original setup.

I'd already welded a heavy plate on my release arm and replaced the worn/wasted fulcrum pin on the pedal to master cylinder end, for complete peace of mind and long term reliability I also specified a brand new slave and master cylinder with a braided flexi hose to compliment the Lloyd supplied clutch kit which they promised me would be nice & light with progressive engagement.

Now I have to say I did go from a nasty feeling and overly heavy Helix clutch to the Lloyds offering but boy what a difference, the clutch they supplied and fitted really is a dream to use, it's light with perfect take up and a bite point right where you want it.

Sure the antiquated release arm arrangement is a bit Isambard Kingdom Brunel but the truth is it works perfectly on my car, I have no idea if a concentric clutch slave would make it even better but for my needs I've come to the conclusion it doesn't need to be any better now so I'm better off taking the field maintenance benefits of an external slave.

That's not say if I tried Pupp's new arrangement I wouldn't fall in love with it and change my mind, its certainly a modification worthy of praise. From a purely engineering standpoint the straight inline push of a concentric slave and the deletion of all those joints, links & pivot points has to be a good thing, I'd also be surprised if Pupp's commendable arrangement didn't give a nicer and lighter feel at the pedal?

A bit like my S-10 tail housing & TVR gear linkage delete it's hard to put how something feels into words on a forum, it's also impossible to determine if making such changes are really worth the work/cost without back to back testing the two setups.

And like the TVR gear linkage delete, in the end it boils down to whether you're happy with what you have (as I am), or if you feel there's a worthwhile benefit in chasing what might potentially amount to a small improvement

Great post all the same, and I wish Pupp a long and reliable service life from his concentric slave

[Pupp]

Well, as toasts go, it's an unusual one but I'm happy to raise my glass with you on that wish!

I would hope the slave itself would not have any inherent flaw that causes premature failure (how many V6 Mondeos are out there on massive mileages?) and, whilst a different component,, the similar one in my Laguna is at about 198k miles now...

Of course, this presupposes the installation and set-up is competent - have been very careful to avoid over-extending the slave (or the clutch cover for that matter), and the thing cannot be but properly concentric given how it is mounted. I confess to not being delighted to hear some (slight) noise where none was expected but do not think it is especially sinister. Time will tell...

[Brerabit]

Once again Dave, we’re in violent accord on this one. I think I’ve got the same clutch as you which I understand is better than the Helix - but light it ain’t. I’m also totally seduced by the sheer engineering elegance of the concentric pusher which makes the existing agricultural agglomeration of levers and pivots look positively primitive. Add to that an almost totally linear action (if we ignore the pedal lever) - whats not to want?

Which is why Dan’s antipathy towards it surprised me a little. Sure, clutch failure is a little inconvenient but it’s not game over. I’d be surprised if most Chimaera jockeys didn’t regard a clutchless drive home as not much more than a minor inconvenience, even a bit of a challenge. I did one once in a Jag MkII (that box was never slick - even with a clutch) from Plymouth to B’ham and at the end of the trip was not only making perfect changes but feeling pretty pleased with myself. But I digress…

It’s indisputably a bigger job to fix if it fails but if you do it yourself, it’s just spannering and relatively cheap. In a workshop for guys who know what they’re doing it can’t be much more than half a day. Not so cheap, but on the mileages we clock up with these things, how often is that going to happen?

Unless - we’re missing something…

Is it that it needs to be ‘designed in’ with a lighter clutch that places less load on the seals - because clearly in the Chimaera it’s doing all the work that was previously aided by the mechanical advantage of the big arm.

I really want to do this if I can be confident I’m not going to have to eat humble pie when I’ve sprayed hydraulic fluid all over my clutch.

Keep us posted Gary, you’ve started something I’m sure a lot of us are very interested in. I’m sure I’m not alone in wishing you all the best with this.

… I’m also willing to bet Dave will eventually find it irresistible …

[ClassiChimi]

Great thread, I'm sure I'm also not the only one who's wishing Pupp well with this,,
I don't consider issues as failure, just another test of engineering solutions so other than the noise this has to be considered a huge step in the right direction.
Great stuff

[N7GTX]

Brerabit said:

I think I’ve got the same clutch as you which I understand is better than the Helix - but light it ain’t.

Unless - we’re missing something…

After reading about heavy clutches, QBee suggested fitting a servo to make the clutch lighter. For some of us with old joints, a heavy clutch can be a real pain. I haven't fitted mine yet but with a 9:1 ratio it should make a heavy clutch considerably lighter. I know QBee is happy with it. I got mine here:
http://mgbhive.co.uk/product/mgb-gt-or-roadster-lo...
Just an idea for consideration....

[ChimpOnGas]

Brerabit said:

Once again Dave, we’re in violent accord on this one. I think I’ve got the same clutch as you which I understand is better than the Helix - but light it ain’t. I’m also totally seduced by the sheer engineering elegance of the concentric pusher which makes the existing agricultural agglomeration of levers and pivots look positively primitive. Add to that an almost totally linear action (if we ignore the pedal lever) - whats not to want?

Agree, my Helix really was dreadful, but I'd also say my Lloyds clutch is lighter and nicer feeling than the AP unit in my mate's 500, a clutch I was very envious of during my Helix years. Actually I'm not sure I'd want a lighter clutch than what I have now, it's a TVR for heavens sake.

My new Lloyds clutch is now very nice to use with a feel that's in keeping with the weight of all the other controls in the car (steering, gear lever, brakes ect ect), and that's really important to create a harmonious driving experience, I feel certain a super light Nissan Micra weighted clutch would just feel wrong in this type of back to basics driver's car.

Now to be 100% clear I do really like this concentric slave idea, Pupp (Gary) should definitely be commended for making it all work, and his point about the proven reliability of such systems in Mondeos and the like is totally inarguable.

I suspect Lloyds aren't keen to fit one simply because they guarantee all their work and they don't want risk the possibility (however slight) of having to suck up a second gearbox out job to solve a leak at their own cost. Given there's currently no tried & tested concentric slave kit on the market for this car I can see why they wouldn't be keen on being the guinea pig, they are after all a business and that should be respected.

Gary has bravely taken on the guinea pig role to the benefit of us all and has been kind enough to share it all here which is exactly what the forum is all about. I tried to do the same with my S-10 TVR gear linkage delete post, and if anyone was mad enough to want to install LPG to their Chimaera it would be my pleasure to show them how its done and share all the things I've learned along the way so they don't have to suffer the same development challenges I've had to overcome, what they would enjoy from this is a system that will work perfectly and to the maximum efficiency from day one.

It's also nice to see Gary has been candid about the development challenges he's had along the way and then gone on to share his solutions. This allows the less brave (including myself) to watch the development process from the comfort of our arm chairs while the OP lies on his back wrestling with his gearbox. If we're honest with ourselves we're all just quietly sitting in the wings waiting for him to come up with a proven recipe of parts so we can copy it, safe in the knowledge it'll all work first time.

What we need now is review of how the clutch feel and weight at the pedal have been altered/improved over the standard Isambard Kingdom Brunel release arm contraption. With all the time & effort that's been invested here it's understandably tempting to sell the end result as "brilliant in every way" but the nice thing is Gary has clearly demonstrated restraint in this area throughout so I'd hope we'll get to hear his candid review soon.

Brerabit said:

… I’m also willing to bet Dave will eventually find it irresistible …

Well yes & no, my honest answer is I only want a concentric slave if it offers genuine and significant benefits in proportion to the investment, and I only want it once the recipe has been proven 100% reliable over an extended period.

I'm also in no rush to fit one because I've just spent a chunk of money on my new clutch, clutch hydraulics and S-10 mod and the end results are such a significant improvement over what I had I find myself asking "do I really need a concentric slave?".

The truth of course in the world of modifying our TVRs is NEED & WANT are two very different things, so lets see what Gary says about how his excellent setup performs and take it from there

[Pupp]

Much as I appreciate the kind comments, the motivation for trying it was primarily because I was not sure I could get the original mechanism's pivot height right for the beefed up clutch cover I'm using; it's quite different to what came out. That, plus the fact I could see the potential for a considerable weight saving by deleting all the hefty steel the original uses. Also, I needed to change the original slave anyway and the replacements available from the usual suspects now have a smaller (hence 'heavier' acting) bore size, which was not going to be helpful given the higher clamping force I needed.

Any benefits in improved lightness are a bonus but impossible for me to objectively assess given there has been no back to back comparison of the two release mechanisms on the same clutch pack. All I can say is this combination does, so far, seem completely linear, and has a very drivable weight and feel but this has to be read in the context of the nasty knackered juddering piece of red crap that was removed.

Whether, ultimately, the single plate unit I am running will prove sufficient as the boost gets ramped up I'm not sure (same goes for the uprated T5 itself); chances are the box will have to be out again soon enough so no biggie if the concentric slave needs some refinement.

If I was doing it again with current knowledge, I would use a cover fitted with an integral release plate, which would avoid the necessity for the round profile adaptor to be bonded on.

[Pupp]

Quick update given I have just done an oil change after putting a few hundred miles on the gearbox and slave conversion. Pleased to say no obvious issues apparent on pulling the inspection plug in the bell housing; all clean, intact, and no signs of fretting or galling etc. Can only conclude the (still present) noise is just that, noise, and not an indicator of impending doom.

Box now has a new fill of stinky Royal Purple so let's see what's what after a blat to Le Mans...