Clutch release

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doc knutsen
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Clutch release

Post by doc knutsen » Tue Aug 09, 2011 6:53 pm

Due to HTP issues and a long delay in getting the latest engine built for my son Matt's Bevan-inspired car, our pair of racing Imps is only now about ready for the second half of the Scandinavian historic racing season. However, we have run into a clutch release issue which has us stumped...
Matt's clutch worked OK last season, but on moving the car after 8 months of rest waiting for the latest demon engine, its clutch will not relase properly. Likewise, my re-shelled car, another Gr2 car exactly like Matt's blue example, will not release at all, despite having all the mechanical bits simply moved into a fresh body shell...no amount of bleeding or re-building master cylinders or slave cylinders have made any difference. The only difference, with both cars, is having new engines, both built on Imp blocks rather than B1 blocks. With the B1 block and crank, the flywheel would sit much further out in the clutch housing, to the extent that the bolts of the AP sinter clutch would leave marks inside the flywheel housing.
Somewhat confused, having run racing Imps for so many years, I removed the clutch release forks and compared them with two units that I had lying about the workshop..and to my great surprise, these were somewhat different: Two of them had their pivots welded to the outer edges of the release forks, while the two others had the pivots poking through the middle of the release arms. Obviously, the geometry of the release mechanism would be somewhat different. And not only that, the actual height of the relase bearing assembly itself (the competition assembly using a roller bearing mounted on an aluminium alloy extension piece) differed by more that 1/4 ". So, what parts to use? Would an adjustable clutch push rod (that pokes into the slave cylinder) be the answer? Or am I missing something else altoghether? Any comments would be much appreciated.
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Re: Clutch release

Post by Grumpyoldmen » Sun Aug 14, 2011 2:11 pm

Surprice! Nobody in a forum filled with Imp specielist seems to know the answer. And sometimes there are answers even if nobody don't know anything!
A fact related to any of Murphy's laws?? :mrgreen:
http://historicracing-photo.blogspot.se/
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Re: Clutch release

Post by The Nun » Sun Aug 14, 2011 2:25 pm

Grumpyoldmen wrote:Surprice! Nobody in a forum filled with Imp specielist seems to know the answer. And sometimes there are answers even if nobody don't know anything!
A fact related to any of Murphy's laws?? :mrgreen:
Could be because youre not members and cant get access to all the good answers from the past :wink:
Peter Nunn...ey im member 00033
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Re: Clutch release

Post by Grumpyoldmen » Sun Aug 14, 2011 2:31 pm

The Nun wrote:
Grumpyoldmen wrote:Surprice! Nobody in a forum filled with Imp specielist seems to know the answer. And sometimes there are answers even if nobody don't know anything!
A fact related to any of Murphy's laws?? :mrgreen:
Could be because youre not members and cant get access to all the good answers from the past :wink:
??? Doc had a question, not me
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Re: Clutch release

Post by moose » Sun Aug 14, 2011 3:36 pm

http://www.petermayengineering.co.uk/specProd5.13.1.jpg

it could be the pivot point has been moved to accommodate this type of roller release bearing as it is about 1 inch deeper than the standard carbon bearing i have a solution that does not require this mod and also prevents the problem of release bearing drag on the top edge as the pivot point on my design stops the bearing falling forwards. gallery/image.php?mode=medium&album_id=12&image_id=4519 do not know if being non members you cannot see the gallery photo's if you want more help Doc get in touch direct mike@symtechracing.com (and in future i will dedicate more of my time to answering forum posts faster to lower the grumpyness of posts :lol: :lol: :lol: )

regards mike
Regards Moose
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Re: Clutch release

Post by Grumpyoldmen » Sun Aug 14, 2011 4:02 pm

That's it!!!
We in Scandinavia want Doc out on the racetrack as fast as possibly and don't want him to be stopped by a silly thing like a clutch release problem!!!
http://historicracing-photo.blogspot.se/
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Re: Clutch release

Post by ImpManiac » Mon Aug 15, 2011 10:18 am

Image

^^ I haven't seen one of these before. Interesting thread, though. :mrgreen: I have heard that there may be two (or more :?: ) different types of release bearing arm fitted to Imps. I do not know which is which, how they differ in detail or which cars they were fitted to. Otherwise, I'd have been happy to help with an answer for Doc. :wink:

When I am rich and decide to buy a transmission with all the tasty bits for my car, I might go down the route of using a concentric clutch release slave cylinder, as per Dennis Allt's (and perhaps others' :?: ) modification. It uses an annular hydraulic slave cylinder with a ball bearing attached directly to it. The only downside that I can see is that it is concealed within the bellhousing and can be a pain if they start leaking because you cannot get to them without removing the engine.

IM 8)
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Re: Clutch release

Post by imporium » Mon Aug 15, 2011 12:38 pm

doc knutsen wrote:Due to HTP issues and a long delay in getting the latest engine built for my son Matt's Bevan-inspired car, our pair of racing Imps is only now about ready for the second half of the Scandinavian historic racing season. However, we have run into a clutch release issue which has us stumped...
Matt's clutch worked OK last season, but on moving the car after 8 months of rest waiting for the latest demon engine, its clutch will not relase properly. Likewise, my re-shelled car, another Gr2 car exactly like Matt's blue example, will not release at all, despite having all the mechanical bits simply moved into a fresh body shell...no amount of bleeding or re-building master cylinders or slave cylinders have made any difference. The only difference, with both cars, is having new engines, both built on Imp blocks rather than B1 blocks. With the B1 block and crank, the flywheel would sit much further out in the clutch housing, to the extent that the bolts of the AP sinter clutch would leave marks inside the flywheel housing.
Somewhat confused, having run racing Imps for so many years, I removed the clutch release forks and compared them with two units that I had lying about the workshop..and to my great surprise, these were somewhat different: Two of them had their pivots welded to the outer edges of the release forks, while the two others had the pivots poking through the middle of the release arms. Obviously, the geometry of the release mechanism would be somewhat different. And not only that, the actual height of the relase bearing assembly itself (the competition assembly using a roller bearing mounted on an aluminium alloy extension piece) differed by more that 1/4 ". So, what parts to use? Would an adjustable clutch push rod (that pokes into the slave cylinder) be the answer? Or am I missing something else altoghether? Any comments would be much appreciated.
Hi Doc, The clutch arms with the pivot on the outer edge should not be used now, dustbin jobs ! these were only used on early Imps, as they would split apart around the pivot point & not release the clutch.....the arms were modified to the later ones with the pivot through the centre & are much stronger....had to change loads of these under warranty when I was a lad at a Rootes dealer !!.. :lol: have a few new ones in stock & some used ones if needed ?.....................Malcolm
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Re: Clutch release

Post by 617sqn » Mon Aug 15, 2011 7:47 pm

/\/\/\ Interesting that, Malc. I was looking at a pair of clutch forks in the Club Spares tent at National, and spied two forks : One of each type described ! I'm glad that this thread has answered that particular question for me :D I'll store that piece of info away for future reference :wink:

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Re: Clutch release

Post by imporium » Mon Aug 15, 2011 8:22 pm

617sqn wrote:/\/\/\ Interesting that, Malc. I was looking at a pair of clutch forks in the Club Spares tent at National, and spied two forks : One of each type described ! I'm glad that this thread has answered that particular question for me :D I'll store that piece of info away for future reference :wink:

Andy G.
I did tell Bob to put that naff one in the raffle...... :lol:
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Re: Clutch release

Post by doc knutsen » Sat Aug 27, 2011 11:42 am

Well it's sorted, after numerous blind alleys. Thanks to a phone call to an ever-helpful David Weedon, Matt and I realised what we had been missing as far as getting our pair of race Imps into operating modus...
Also would like to point out that good old Malcolm Anderson managed to get a slave pump over to this country in three working days, despite Norwegian Customs doing its level best to interfere.. However, we have missed this week-end's big Classic and Sports Car Meeting which means that our Nordic season is close to ending, with neither of our Imps having been out at all this season.
My re-bodied car was finally ready in late May, when the application for an HTP was sent to the FIA here. I had hoped to run at the classic Velodromloppet at Karskoga in Sweden, although Matt's car, the blue Bevan inspired car you may have seen in Utube videos last year, was still waiting for its engine to be re-built around an Imp block, after the FIA had declared the B1 blocks not kosher. My car had a newly built 998 using the correct block...and therein lies a clue, both cars having run so well with engines built on the B1 blocks for some three seasons...
Matt's engine was finally collected from Reg Patten in late July, and duly fitted to the blue car. As for my own car, I am still waiting for the HTP and the FIA's reps in this country have not (yet) replied to two enquiries.
As a result of this, the car has been sitting idle since May...no HTP, no race! However, the authorities at the C&Sm granted me a permission to run at their big race, pending the arrival of the HTP, so all hands were called into action to get the pair of Imps ready. Then, the clutch fun and games started! As related in my previous posting here, no amount of fault tracing could find a cure for the yellow car. And that includes changing a suspect Aeroquip joint in the hydraulic line, re-building the master pump and slave pump, even fitting a brand new slave pump courtesy of Mr Anderson... making up a rose-jointed adjustable release push rod and finally whipping out the engine and changing the sintered AP clutch itself - in between numerous bleed jobs, including having the rear end of the car jacked up overnight for any remaining air bubbles to come to the surface...yet no success. With the car in the workshop, the clutch would free when the car was pushed with the engine not running. However, once the engine was fired up, the clutch pedal got all limp and staunchy refused to work.
At the same time, Matt's blue car came down off its trestles with the new engine firing up on the very first try, kudos to the good Mr Patten. Matt was just taking the car out for a run up the road (on trade plates, officer) when he realised the car's cluch pedal...got all funny when the engine was fired up. And this car's clutch worked perfectly well last season, with nothing having been touched except for the block-related engine change.
With time to make practice at the C&SM rapidly running out, I phoned Dave Weedon for advice. And then it clicked... Dave suggested we seemed to have excess clutch release bearing free travel, the release bearing assembly travelling too far back once the engine fired,probably due to the vibrations. The clue is changing from the B1 block engines on both cars.The flywheel/clutch assembly on the B1 engine sits more than half an inch further out compared to the Imp blocked engines - indeed I had to fit countersunk bolts on the AP cluch in order to avoid the bolts fouling the inside of the clutch housing. With the Imp block engines, the full travel of the slave cyl push rod is not enough for the release bearing to fully engage the clutch. An adjustable travel stop to limit the return travel of the release fork was all that was needed - simple enough when you know it! I have just removed the engine from Matt's car and modified the release fork with a 5/16 bolt through it, with a nut welded on the other side of the fork, so that the head of the bolt will hit the transaxle housing before letting the fork travel all the way back, and - of course - it works! I now need to connect the engine and remove the engine from the yellow car and carry out a similar job. Then we should have a pair of working race Imps at long last!
But I am still waiting for the FIA to provide an HTP for the new car, with this car being an exact copy of the blue one that got its HTP last year you would think this would to be not too much work for the FIA...
.
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Re: Clutch release

Post by knutspeed » Sat Sep 10, 2011 7:33 pm

Evidence:

:)
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Re: Clutch release

Post by Grumpyoldmen » Sat Sep 10, 2011 9:25 pm

knutspeed wrote:Evidence:

:)
Yes, what a lovely day!!
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Re: Clutch release

Post by doc knutsen » Tue May 15, 2012 5:38 pm



Well, it worked in the end! My brand new FIA Period G race Imp finally hit the track last week-end, having gotten its HTP paperwork in late March. And the clutch now works sweetly, absolutely no bugs at all.
First race of the National Championship was held at Vaalerbanen, and the car proved totally reliable and vice free, straight out of the box.
Qualifying 2nd to a potent Abarth in the up to 1300cc class, we then went on to finish second in both Saturday's and Sunday's race, beaten by that same Abarth...but finishing ahead of a very quick NSU TTS in both races. The video shows that we suffer in straightline speed, also the 3rd and 4th gears are too tall for the Avon ACB10 tyres (23" diameter) ...besides the driver, at 63, being a wee bit rusty...still, a rolling road session and some lower cogs, and we'll be challengign for the top of the podium.
Great fun !!
And once again, thanks to David Weedon for solving the clutch riddle...
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Re: Clutch release

Post by bks974c » Tue May 15, 2012 7:04 pm

Well done - loved the TLC for the car at the end :lol:

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Re: Clutch release

Post by 617sqn » Tue May 15, 2012 7:31 pm

loved the TLC for the car at the end
Haha ....... now tell me you've never done that ! :lol: 8)

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Re: Clutch release

Post by knutspeed » Tue May 15, 2012 7:38 pm

Seems to be a requirement for these cars - they do have souls! Besides, I'm quite certain that "pumpkin 2" is female :wink:
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Re: Clutch release

Post by Lars Hagermark » Tue May 15, 2012 9:53 pm

Stunning first outing Doc K! :D
knutspeed wrote:... I'm quite certain that "pumpkin 2" is female :wink:
If so she's an ambitious and hot tempered lady when introduced to other cars on a race track. :wink: :lol:
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Re: Clutch release

Post by Impecunious » Wed May 16, 2012 10:20 am

Nice video Fredrik! Glad to see you are getting some enjoyable laps in. Looked to me like you were also getting some WD40 into your rusty joints as the race progressed :lol:

I would agree with the gear ratio assessment - I think you should try one shorter on third and fourth for your next race.

Look forward to seeing you again Sir 8)

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Re: Clutch release

Post by ImpManiac » Wed May 16, 2012 10:53 pm

I like your videos! :mrgreen: The yellow race car certainly goes rather well. I see what you and Mr. Weedon mean about the ratios, though. She doesn't quite reach maximum revs in third or fourth before you have to apply the brakes. But what a great result first time out! :P

IM 8)
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