Rob Board Posted December 17, 2002 Share Posted December 17, 2002 Gents. Firstly thanks for all your replys and posts to my origional thread. Top marks to BRICOL for the best analogy. And appologies to Rob Walker for "Doing it to death", sorry mate. However I spoke to AP today, and along with the bearing manufacturer this is the final answer. "If that CRB which is designed for a pre load application is being used in the CATERHAM where no pre load exists it will EAT CRBS!!!".(See Bricols post as to why) The experts words at AP and INA who make the clutches/bearings ,not mine, please don't shoot the messenger. The solution? Although I do have two possible solutions, a heavy duty spring to pull the Release lever and so CRB snuggly against the spline fingers, or my preferred method, a threaded stud which could be fixed via a mounting plate on the bell housing and adjusted as the clutch wears to apply pressure to the release lever, so giving pre-load. I have drawn up a few bits already, but as my car under warrranty can't touch it till Oct 03. However when CRB done will speak to Caterham. If anything forthcoming will then post the factory solution. There thats that one put to bed for now.(Thank god) Thanks once again, it really has not been my intention to annoy people with my quest, so if it has sorry. However from all the e-mails, posts, phone calls I have recieved I know a great many wanted the reason for failures and now you have it. All I need to do now is sort it. No more CRB posts till its fixed in a few months.Cheers Rob. Link to comment Share on other sites More sharing options...
Rob Walker Posted December 18, 2002 Share Posted December 18, 2002 Famous last words. Edited by - Rob walker on 18 Dec 2002 09:12:50 Link to comment Share on other sites More sharing options...
Rob Walker Posted December 18, 2002 Share Posted December 18, 2002 No problem Rob I wasn`t annoyed just that we keep covering the same old ground. I have serious doubt`s about the suggestion of applying more spring pressure against the CRB. The uprated AP clutch is only rated at 129 lb/ft max torque capacity and any additional pressure against the cover fingures via the CRB will reduce this capacity further. Rob Link to comment Share on other sites More sharing options...
sjwb Posted December 18, 2002 Share Posted December 18, 2002 Sorry to disagree Rob, but it would be far simpler to set the clutch pedal with a positive stop and adjust the cable to pre-load the release bearing. Obviously this is NOT self adjusting, but obviates springs and screwed stops at the transmission. Steve B Link to comment Share on other sites More sharing options...
J.R. Posted December 18, 2002 Share Posted December 18, 2002 Bad idea (both of them) As the clutch wears it takes up free play in the cable. If the clutch arm is mechanically pre-loaded other than via a spring any wear in the clutch will increase the pre-load and decrease the clamping pressure. The clutch would slip in a within a very short mileage. Heat expansion of the clutch assembly and the cable would probably cause it to happen straight away. Link to comment Share on other sites More sharing options...
Rob Board Posted December 18, 2002 Author Share Posted December 18, 2002 Rob W. Is not the 129Lb/Ft torque rating the maximum torque that the clutch can handle before slipping. Applying presuure to the CRB would not IMO reduce the torque capacity of clutch, providing the pre load is not too great so as to start to declutch. According to AP this force is "Well in excess of any CRB design pre-load ie 80 -120 Nm" But I do agree with you too much and you are in s**t Could be wrong often am!!!.JR Any ideas then? or should we all give up and admit defeat? Maybe a self adjusting pedal with a ratchet as found in many tin tops in addition to a pre load mechanism. Anyway hopefully Caterham will engineer a solution when presented with the facts? Rob. Edited by - ROB BOARD on 18 Dec 2002 18:21:19 Link to comment Share on other sites More sharing options...
Grim Reaper Posted December 18, 2002 Share Posted December 18, 2002 It sounds to me like you just need to make the spring on the clutch pedal a little stronger,to ensure the bearing is kept in good contact with the fingers.The pedal position is then set by the cable adjuster and any wear in the clutch will be noticeable by a variance in the pedal height,just re adjust the cable to bring it back again. Link to comment Share on other sites More sharing options...
sjwb Posted December 18, 2002 Share Posted December 18, 2002 JR you are not paying attention *mad* I specifically said NON SELF ADJUSTING and without fitting a pedal stop you can achieve non of the schemes. Just for info, my wife's Polo has just such a set up. Yes one has to carry out some maintenance occasionally. There is of course the option of an hydraulic set up - if some enterprising person is willing. Steve B Link to comment Share on other sites More sharing options...
Rob Board Posted December 18, 2002 Author Share Posted December 18, 2002 Steve B. I am paying attention 😬 and know exactly the set up you mean. Maybe I shall try when car out of warranty! Cheers Rob Link to comment Share on other sites More sharing options...
J.R. Posted December 19, 2002 Share Posted December 19, 2002 SWJB Perhaps you misunderstood me but I didnt make any comments about self adjusting. FWIW The Caterham set up is not and has to be adjusted to maintain free play, no free play = clutch slip very soon. Maybe I dont understand your posting but I was trying to get across the above and that if the CRB is preloaded by any means which does not allow the clutch mechanism to move the CRB and release arm back as it wears then the clutch will wear out "as sure as eggs is eggs" Unless of course you are constantly readjusting the thing including engine hot from cold. My solution would be to do what most manufacturers did: A tension spring between clutch arm and bellhousing to preload the CRB. Often in addition to this there is a stop (sometimes adjustable) fitted to limit the up position of the clutch pedal together with a small tension spring pulling the clutch pedal up against it when not in use (this is in the pedal box not bellhousing and does not act on the cable). This takes away any "dead feel" stops rattles and ensures that only the preload from the spring is acting on the CRB. Happy Christmas everyone Link to comment Share on other sites More sharing options...
Peter Carmichael Posted December 19, 2002 Share Posted December 19, 2002 I run a concentric hydraulic clutch release, using a one-off slave cylinder of my own design. I am in the process of setting up small volume production. It was originally conceived as the only way to get reliable actuation of a race clutch in the caterham dry sump oil tank bellhousing. Variants will be suitable for actuating more normal K-series clutch set ups. Link to comment Share on other sites More sharing options...
Old Septimus Posted December 19, 2002 Share Posted December 19, 2002 A tension spring attached to the end of the clutch arm has to run towards the rear of the car to pre-load the bearing. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted December 19, 2002 Share Posted December 19, 2002 Are you sure, Old Septimus? Doesn't sound right. Link to comment Share on other sites More sharing options...
Grim Reaper Posted December 19, 2002 Share Posted December 19, 2002 A spring from the clutch arm,in the engine bay, would have to run in the same direction as the cable in order to replicate a foot resting on the pedal permanently. A spring on the clutch pedal, in the pedal box, would have to be positioned so as to have the same effect, which if you use the existing hole in the top of the pedal bracket means a spring towards the windscreen tries to pull the pedal down and away from the driver. If it runs toward the front of the car,it will be trying to pull it up. Link to comment Share on other sites More sharing options...
Nick Green Posted December 19, 2002 Share Posted December 19, 2002 In the interests of adding a few more facts and figures to this issue, I would like to attempt to measure the force the current clutch spring applies to the CRB. No one seems to be trying to do that yet. RobB quoted figures of 80-120Nm or 59-88 lbft. As others have pointed out, these are torque figures, which imply a turning or leverage force (don't they ?). If I re-fit the clutch spring to my car (5000 so far trouble-free un-preloaded miles BTW), and use a spring balance to pull back the clutch fork until it starts to move, then read off the figure, in lbs, on the scale, do I then multiply it by the length of the clutch fork from the bearing to the cable ? Or is it not as simple as that ? Assuming that lack of enough preload is the problem, then isn't the easiest solution just to fit a stronger spring ? How would one measure the force being applied by a rod, or something, pressing on the back of the clutch fork ? Link to comment Share on other sites More sharing options...
Old Septimus Posted December 19, 2002 Share Posted December 19, 2002 On a Xflow and the other North South cars I've worked on, the clutch arm has a fulcrum inside the bell housing between the outer end of the clutch arm where the actuator applies force and the inner end which applies force to the CRB. If the inner end presses the CRB forwards towards the clutch fingers and the front of the car the actuator must push or pull the outer end towards the back of the car. Thus your tension spring must pull backwards to pre-load the bearing. The compression spring inside my slave cylinder pushes the arm backwards to the same effect. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted December 19, 2002 Share Posted December 19, 2002 In the k-series application, the cable arrives from the front of the car and the fulcrum is diametrically opposite the cable attachment point. So the spring should be fitted to push the release arm forwards (away from windscreen). Link to comment Share on other sites More sharing options...
Old Septimus Posted December 19, 2002 Share Posted December 19, 2002 Sorry - I'll stick to my Whit spanners. My Sunbeam Talbot 90 had a really good piece of chain to operate the clutch! Link to comment Share on other sites More sharing options...
Rob Board Posted December 19, 2002 Author Share Posted December 19, 2002 Nick. Just spoke to "automotive applications whizz" at INA Bearings. He says pre-load is N NOT Nm. ie it's just a "static" load, not a turning force measured from the cable end of the lever. The guy who originally gave me this info to be fair to the company, was not said "whizz". So well done to all who spotted that c**k up. Sorry. Rob Link to comment Share on other sites More sharing options...
Nick Green Posted December 19, 2002 Share Posted December 19, 2002 So do you think my method of measuring the spring loading is viable ? Any idea if any "multiplier" needs to taken into account at all ? To be honest, it doesn't look like it to me... Link to comment Share on other sites More sharing options...
Rob Board Posted December 19, 2002 Author Share Posted December 19, 2002 Nick as the spring balance would be applied to the end of the clutch lever( for sake of argument 1 ft from centre of CRB) then this wolud give a torque figure say 50lb on spring balance x Ift from centre of CRB, hey presto 50Lb/ft not a static load. It must be remembered this is the required force applied to the lever to make it move to depress the splines. I am sure it would be possible to work out said static pre-load by using the torque figure, but I would not like to say if it's as simple as dividing force by distance. I shall attempt to dig out my HNC notes on dynamics etc and see if there is more to it. Hopefully some boffin will know. If I find out I'll let u know. Rob Link to comment Share on other sites More sharing options...
sjwb Posted December 19, 2002 Share Posted December 19, 2002 I can't be bothered any more *confused* *confused* . Stop talking about friggin' torque. A preload force of 50 - 80 Newtons (note NO distance) is appropriate Peter your hydraulic CSC (concentric slave cylinder) sounds very interesting. Steve B Link to comment Share on other sites More sharing options...
Johnty Lyons Posted December 19, 2002 Share Posted December 19, 2002 Got to agree with steve Peter always was interested in your concentric hydraulic [saab] Clutch if this will work with a Carterham 6 speed and AP R500 F/Wheel clutch assy I'm all for it. *biggrin* jj N.I. L7C AO. Membership No.3927. Link to comment Share on other sites More sharing options...
Nick Green Posted December 20, 2002 Share Posted December 20, 2002 Steve, we've already stopped talking about torque. Check out Rob's post before your's. You mention 50-80 Newtons. How do you propose to measure it ? Link to comment Share on other sites More sharing options...
J.R. Posted December 20, 2002 Share Posted December 20, 2002 Rob does mention torque although I rather hope that he is trying to express a "moment" (force mutiplied by distance) as opposed to a rotational torque. If the leverage ratio of the clutch arm is the same on the 6 speed as the 5 speed bellhousing then the mechanical advantage is in the region of 2.25:1 To be certain measure the clutch fork: divide the distance from cable location to fulcrum by the distance from the fulcrum to centre of CRB carrier. The resultant figure is the mechanical advantage (or leverage ratio) and should be multipied by the spring tension (at the fixed length when clutch released) to give the preload acting on the bearing. HNC's cant be what they used to be Edited by - J.R. on 20 Dec 2002 11:57:00 Link to comment Share on other sites More sharing options...
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