Race Engine Forum UK

Here are some pictures showing the shaft problems ( fixed)

a/ The small free play between splines on the sleeve yoke and the shaft. ( The shaft yoke will be replaced . maybe the short shaft as well)
b/ Bearing of the shaft support , the bearing flexible carrier and bearing carrier outer tube worn, All will be replaced
c/ Shaft spiders worn ( will be replaced )
d/ signs of movement between shaft flange and and diff flange. ( We will now use 12 grade bolts and nuts to get it tighter. We also will put between them a micro thin diamond friction sheet to prevent any movement when bolted together.

Miro

Pre rally work

1/ New seats
2/ High security
Miro

Now the free play you mentioned makes a lot more sense to me. Most of those locations, I think you will need new bearings, or the spline part replaced or reworked. There's nothing that can be fixed there with tighter bolts. If those bolts work themselves out, it almost must be from the knocking caused by the play on the splines and the cross bearing. Friction should keep those bolts immovable, but that friction will be overcome if there is too much knocking going on. I've seen bolts that were just sheered off because of this. It's good you are paying attention to this detail, we've all seen the pictures of what happens if this goes wrong.

Wizzman

We have replaced all spiders ( with heavy duty versions) and put a new donut flange and the eliminated the potential problem.
the bolts holding the diff and shaft flanges were replaced with 12 grade (12 bolt and 10 grade nut).

The car is inspected very carefully before each event and all problem issues are addressed and parts replaced.

Actually we hav also adopted Guy's advice not to reuse the botls nuts and washers, at all. Once removed it feeds the scrap can.

No reuse at all. Believe this policy pays off.

Thanks

Miro

Guy,

The new Hellix clutch received. Speed of light delivery !

Miro

PS you can tel Helix they need to make sure that the parts match . We had to put the disk on a lathe to shave off few microns , as when you tried to engage the clutch the pressure springs were catching the disk shaft.

When we compared the new clutch with the old clutch no size difference was see, When we measured it with standard (non electronic caliper) the difference was too small to be measured. We had to resort to micrometer. So discrepancy was not minute , but required shaving off the shaft by few microns.

See pictures.
No problem at this end as we have easy access to a big lathe, some may not.

Incidentally we had to install the clutch to notice the problem. The pressure springs create a smaller circle (opening) when installed and engaged.

M

miro-1980 wrote:
Actually we hav also adopted Guy's advice not to reuse the botls nuts and washers, at all. Once removed it feeds the scrap can.

No reuse at all. Believe this policy pays off.

That's smart. It's probably more expensive to do extensive testing on the used bolts to determine if they are still good, than to just use new ones.

Yes I shall pass that on to Helix. Thank you for checking and correcting.

G

I spoke to Helix

I think you may be 'over-stroking' the clutch. In other words the cover springs are being compressed too far. That is a standard cover & hub pattern we've used for years.

Report please!

G

Question .

The basic principle of the way the clutch works is rather simple and I understand that , but the way clutch works in the assembly (from the clutch pedal and line all the way to the gearbox) is not something I really looked at with any depth. Funny (stupid ?) , but true. I need to look at it again to understand what pushes what and understand interdependencies between all the mowing parts.

I will do this after the rally , so give me a crush course: Please advise : if the wear suggest that clutch pedal travel is too long ( or too short ? Or what else this might suggest ?


Miro

Some pictures of a Tilton cerametallic clutch may help you to understand.

How far the release bearing moves when you press the clutch depends on the cable free-play and also the 'mechanical advantage' of the pedal itself.

The standard setup pedal in the 131 should cause no problems but if you alter the length of the pedal above or below the pivot point or the position of the pivot point or the stop (that the pedal hits at full depression) it could easily cause too much release bearing travel.

It is too complicated to model on CAD without knowing the specific dimensions, I have tried! There are too many permutations.

G

Just as a quick follow-up I recommended Miro (by phone) use 12.9 grade bolts and 10 grade nuts with Disc-Lock washers.

http://www.disc-lock.com/stainless-steel-washer

GC

Just a quick update ;

1/ We are in full swing preparations for the St. Barbara Rally

2/ More updates after the rally.

3/ The page went public : www.131abarth.pl ( no more registration/log in required, it is now visible to the search engines )

4/ Wish me luck and not to be tempted to race Bryan Bouffier and other Champions (LOL)

5/ Re clutch . Thank you. It must be the clutch pedal travel issue. There is no upholstery and no silencing mats , so the pedal goes all the way to the metal floor. We will place a small support (2 mm thick) in the place where the pedal touches the floor . Hope this is enough.

Miro

It may not matter that the clutch goes all the way to the floor, because once it is depressed beyond a certain point it will not pull the cable anyway since the cable end of the pedal swings in a circular arc.

Have you altered the length of the pedal in some way?

This is quite serious - your kind attention please.

No way can you keep running a unit where the clutch actuating arm is over-stroking - hard contact of the cover springs with the friction plate will impose an excessive load on the crank thrust washers.

You should test this with engine running on axle stands and someone under it to see how much travel is needed to disengae the clutch and how far the pedal is actually capable of moving the clutch release arm in the extreme. You should barely have to 'kiss' the pedal to lay off a cerametallic clutch.


G

Guy Croft wrote:Just as a quick follow-up I recommended Miro (by phone) use 12.9 grade bolts and 10 grade nuts with Disc-Lock washers.

http://www.disc-lock.com/stainless-steel-washer

I've never seen those before. Very nifty indeed. Bookmarked!

Just as a quick follow-up I recommended Miro (by phone) use 12.9 grade bolts and 10 grade nuts with Disc-Lock washers.

Hey, I was about to say the same as Whizz... nice washers!

Guy, out of interest: What size is this bolt? I'd say M10 but it might be fine thread for instance. What sort of torque did you specify? Original value or higher (considering the 12.9 grade bolts)?

regards
Tom