clutch pedal bounce??

[pkw2704]

So, went for a blast today to see where my local area meet is ,noticed when giving the car its legs so to speak, i could feel the clutch pedal bouncing?? do i need stronger springs or some form of adjustment? i presume its the thrust bearing on the clutchplate feeding back

[Jonathan Kay]

Cable or hydraulic operation?

Thanks

Jonathan

[Jonathan Kay]

Guide: "How to pre-load the clutch release bearing (crb) -- for cars with cable clutches".

Jonathan

[pkw2704]

cable sorry

[pkw2704]

Wow, bit technical for me but i get the gist of what he's saying.So  i gather i need a double spring set up ,anyone know if the springs  are still available from Caterham?

[Wrightpayne]

I used to get this until I added the extra spring as per John's pre load mod then it stopped.

Its quite an odd sensation bouncing back through the pedal!

[revilla]

When you say "bouncing" ... Do you mean the sort of bouncing that suggests it's flopping about on a fairly soft spring (I'm struggling to imagine how you would feel this through your foot), or do you mean you can feel a pulsating vibration through the pedal, with the pedal pulsing up and down against the pressure of your foot (a little bit like the feel of ABS operating). If it's the second, that was one of the first warning signs I got of a rather nasty clutch failure. What happened in my case was the (hefty metal) clutch cover plate fractured in several places and started to come apart. Not the friction plate but the main spring cover. There's a thread on here about it somewhere with pictures. The pedal pulsation was, as you say, the CRB feeding back through the pedal, but if all is well the CRB shouldn't be moving backwards and forwards on each rotation. On mine this was happening because the cover plate was distorted and out of true. Quite some while after that I started to get a juddering with the clutch just lightly engaged whilst pulling away or reversing into a parking space. If I'd known what had actually gone, I wouldn't have risked driving it home from Wales as if the plate had actually broken up, and it was very close to doing so by the time I got it out, it could have resulted in a nasty (and dangerous to life and limb with your legs so close to the bellhousing) clutch explosion. I actually have a spare Caterham bellhousing that was literally torn apart by a clutch explosion and had to be welded back into one piece! Mine was an AP Racing clutch cover and friction plate.

[pkw2704]

never noticed it before, but never really given the car any beans .It was more bouncing up and down with no foot pressure on it at all(foot to the side/under pedal) take on board your clutch cover issue.Seemed more, not enough preload,did notice it only has one spring on clutch pedal

[John Vine]

...anyone know if the springs  are still available from Caterham?

The springs I used were P/N CQ13.  Unfortunately, neither CC nor Redline stock these any more (the supplier went out of business, apparently).

Several of us have searched for alternatives, but I'm not aware of one.

JV

[Wrightpayne]

This might be worth a punt to find a similar one....

https://www.lsengineers.co.uk/accelerator-clutch-springs.html?utm_source=google&utm_medium=cpc&utm_campaign=google-ps&gclid=EAIaIQobChMI4pTv84ef8wIVSoBQBh1XwQK1EAQYCSABEgJyrPD_BwE

[OldAndrewE]

That looks like a really useful selection

[John Vine]

That could be a winner, Ian.  Good shout.

I think I'll contact them with the spec of the CQ13 spring and see what they can suggest.  I'll post up the results.

JV

[pkw2704]

Here is my current set up (one spring ) if you can find out about the other springs please let me know

[John Vine]

That looks like the standard pedal return spring (CQ13).  If so, the pre-load it will apply at the CRB (about 20N when I did my calculations) will be much less than the recommended 80-120N.  As far as I can tell, the sole purpose of that spring is to retain the other end of the cable in the clutch fork.

You could boost the pre-load to maybe 50N by shortening the two hooks like this:

and attaching the spring so that it acts in a direct line with the cable:

And then, of course, add a second spring if/when one can be found!

JV

[pkw2704]

that is looking like the solution

[John Vine]

Re #12:

Well, I contacted lsengineers, providing dimensions etc, plus what I was hoping to use the spring for.

I'm afraid they were less than helpful.  First, they told me:

"...we are unable to source parts for motor vehicles. Our main market is for Plant & Gardening machinery."
When I asked whether their 110159 assortment (the one Ian linked to) contained a spring similar to the spec I'd given them, they said:

"We wouldn't be able to confirm if these would work. However we do have the assorted pack."

 

Not wonderfully impressive!

 

JV

 

 

[Wrightpayne]

John,

I guess that might involve getting off ones backside and using ones brain! 
 

A cheap bag of springs none the less. A purchase may yield a manufacturers label on the bag?

Regards

Ian

[OldAndrewE]

So I bought a pack of these as they look a handy lot.

These are them - no manufacturers branding on the package

[John Vine]

Many thanks for that, Andrew!  

The supplier (L&S) told me today that they buy in these springs.   When I asked if they could tell me the manufacturer's name, all they said was that the springs "could be returned if unsuitable".

These ones look very similar to the old CQ13, albeit a bit shorter perhaps (85mm? vs 100mm), but the number of coils (at 20 or so) is about the same:

 

Would you be able to measure the spring rate of those?  IIRC, CQ13 was around 5lb/in.  If they match reasonably closely, getting four for £10.80 + P&P is good value on its own.

JV

[OldAndrewE]

John, the ones you have identified are about 20lb/inch.  Wire must be thicker.

The ones marked below are about 5lb/inch.  Have about 35 coils and are about 88 mm long

[Wrightpayne]

As an aside, how do you measure spring rate? Fishing scales and the poundage it takes to stretch it an inch? 

[7 wonders of the world]

 yep, or hang it up and add weight until it moves an inch, I've used a bottle before and just add water then weight the bottle

[OldAndrewE]

Yes, I hung two up and pulled one down with a spring balance until it was an inch longer.  Obviously results are approximate 

[revilla]

Sometimes easier to use a fixed weight rather than a fixed inch length. So for example if you hang a 5lb weight on it and it stretches by half an inch that's 5/0.5=10lb per inch.

[John Vine]

Re #20:

Thanks, Andrew.  Those springs look to have a coil length of about 50mm.  I think the clevis-pin to pedal-box edge in #14 measures just over 90mm, so those springs should fit nicely.

Re #24:

That's how I did it when I was researching the pre-load article.  I attached one end of the spring to a cupboard door-knob and then hung a kitchen weight (4lb, I think) on the other end.

JV