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PostPosted: Sun Aug 26, 2012 6:59 pm 
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As some of you know, I'm fitting a hand operated clutch to a 165 whose owner has had his left foot amputated.

The system being used is nicknamed the 'duck clutch'. The basic principle of it is a flap on the back of the gearknob whick links to a servo whick pulls the clutch pedal down as the flap is pushed downwards.

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http://www.youtube.com/watch?v=oiXnVl_KZ70

The servomotor unit links to the clutch pedal via a Bowden cable which pulls on the pedal. The cable inner passes through a hole in a bracket attached to the pedal so that the pedal can still be pressed with a foot.

The first problem I am not happy about is this means that the cable needs to go round a tight corner and come up behind the pedal. I have moved the attachment point away from the floorpan as far as possible by addind a bracket to the pedal up into the back of the dash, but space is limited. Mechanically it would be better to make a hole in the floorpan, but the place it needs to be attached to the pedal is behind the brake servo, plus access and space is limited the other side of the bulkhead anyway. The other possibility of adding a lever from the pivot point at 90 degrees then pulling paralell to the dash is thwarted by the location of the steering column. The upshot is a bit of extra stiffness and flex in the system, plus I would expect accellerated wearing of the cable requiring frequent cable replacement.

The second problem encountered is that the servo motor setup is not powerful enough. The picture below shows the device in it's standard form. The servo itself rotates through 180 degrees and operates a beam via a conrod. There is a pull spring (at the bottom of the pic.) which is intended to help pull the cable. This is adjustable by a bolt (head on the outside, left side) which sets the position of the left hand side of the spring. The fundamental problem with this is that it gives maximum pull when the clutch is up and requires no pull, and gives minimum assistance with the pedal fully down and requiring maximum force. The standard spring has a very high pound per inch rating and quite a long free length meaning the difference between minimum and maximum assistance is quite large. It would be better to use a weaker but shorter spring and stretch it proportionately further. This would result in a more constant assistance force.

Image

My thought for a better long term solution is to tap in to the hydraulics directly in a similar manner to a hydraulic handbrake, i.e. insert a master cylinder in the line between the standard master cylinder and the slave. This would remove the friction and flex of the cable and pedal setup, but would also lose the assistance of the overcentre spring on the standard pedal. Hopefully the gains would outweigh this loss. It would be fairly easy to make a hole in the right hand end of the actuator and attach the master cylinder to it with the pushrod going through and attaching direct to the beam.

In the short term, I'm looking for a spring supplier likely to stock a suitable spring. Any contact details would be gratefully received.

I'm also looking for data on the dimensions of the standard master cylinder (bore & stroke) so I can calculate volume and pick a suitable master cylinder to use. Also any contact info for suppliers of generic master cylinders would be useful.

Also after any other suggestions seeing as we have some good engineering brains on here.

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PostPosted: Sun Aug 26, 2012 10:09 pm 
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Try these people, I have used them for work and they have a massive standard range and will custom wind to your spec. They are based in Reading and even for a piddly £20 order were really helpful. As they are based in Reading area it may be worth taking your spring to them for discussion/measurement.

Firstly I assume that the fixing point of the bowden cable to pedal uses all the travel of the duck system to minimise force required on the pedal to move it?

I would have some concerns about using a weaker spring as even stuff wound from decent spring steel seem to have a small element of settling over time. You really need to find out the force required to ensure you don't try and operate the spring the spring in or close to its plastic deformation range. Is there any room for a helper spring insode the existing spring?

By the look of the picture you also have a few holes in the conrod arm to allow you to set the amount of movement you get from the box. Keeping the movement here small as you can get away with shodul mean the spring providing more equal force over its range of operation.

It looks a bit of a PITA to setup TBH. I think someones suggestion of direct activation of the clutch hydraulics via this box makes much sense to me but I kind of assume a standard clutch pedal is probably required for insurance or legal reasons somewhere?

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PostPosted: Mon Aug 27, 2012 12:08 am 
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Diceman wrote:
Try these people, I have used them for work and they have a massive standard range and will custom wind to your spec. They are based in Reading and even for a piddly £20 order were really helpful. As they are based in Reading area it may be worth taking your spring to them for discussion/measurement.

Firstly I assume that the fixing point of the bowden cable to pedal uses all the travel of the duck system to minimise force required on the pedal to move it?

I would have some concerns about using a weaker spring as even stuff wound from decent spring steel seem to have a small element of settling over time. You really need to find out the force required to ensure you don't try and operate the spring the spring in or close to its plastic deformation range. Is there any room for a helper spring insode the existing spring?

By the look of the picture you also have a few holes in the conrod arm to allow you to set the amount of movement you get from the box. Keeping the movement here small as you can get away with shodul mean the spring providing more equal force over its range of operation.

It looks a bit of a PITA to setup TBH. I think someones suggestion of direct activation of the clutch hydraulics via this box makes much sense to me but I kind of assume a standard clutch pedal is probably required for insurance or legal reasons somewhere?


The extra holes in the arm were put there by me in order to get full pedal travel with full servo travel. I originally measured cable movement and put in the right place on the pedal (actually the only place it had room to fit) then found that with all the flex in the system there was not enough travel. I realise that by increasing bar movement I have made the spring situation worse but I think it would have only just worked anyway.

A hydraulic system as I described above doesn't affect normal clutch operation. When the secondary master cylinder is fully retracted it just acts as a pipe and passes fluid through. When the pushrod is pushed in, it shuts off the inlet port and pushes fluid towards the slave cylinder. I already have this system in operation in my 185 for the handbrake.

I'm hoping a spring will be a quick fix to get the system running so Chris can get to JAE, then I'm planning to have the car back anyway for some welding, fuel tank repairs etc. (in reverse order :lol: ) so can sort a better solution then.

By the way, I don't see a link to the spring people or am I being blonde ?

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PostPosted: Mon Aug 27, 2012 12:28 am 
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How about upping the strength of the stock spring

That would decrease pedal weight where the duck spring is at its weakest but would increase initial weight


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PostPosted: Mon Aug 27, 2012 12:38 pm 
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I adjusted the spring up to the point where the servo could not push back against it (i.e. couldn't release clutch) then backed off until it just could. At this point it still needed me to slack off the cable a bit in order to get the servomotor to full extension. At this point it still had a little clutch drag making it difficult to get in gear when stationary but was fine for pulling away and changing gear.
It was too close for comfort and would sometimes fail to return to the 'home' position throuwing an error and requiring a power off / power on with some external assistance to reset it.

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PostPosted: Mon Aug 27, 2012 1:08 pm 
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Perhaps should have been a bit more explicit. I was thinking of the stock Toyota over center spring

That would make the initial pedal feel a bit heavier (but the duck has max internal spring assist there) but should ease the effort required when the Toyota spring goes over center where the duck internal spring is approaching its weakest

It might make the real pedal feel a bit odd but you could possibly test it out with random springs floating about the workshop doubled up with the OEM Toyota one


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PostPosted: Mon Aug 27, 2012 2:00 pm 
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two_OH_five wrote:
Perhaps should have been a bit more explicit. I was thinking of the stock Toyota over center spring

That would make the initial pedal feel a bit heavier (but the duck has max internal spring assist there) but should ease the effort required when the Toyota spring goes over center where the duck internal spring is approaching its weakest

It might make the real pedal feel a bit odd but you could possibly test it out with random springs floating about the workshop doubled up with the OEM Toyota one


I had thought of this and in many ways it would be the preferable option - apart from the job of actually changing it (I dismissed it as I'm a lazy git). Access is awful and it will be a very powerful spring. It would have the benefit of making the pedal much lighter overall and may reduce force on the cable to the point where the current setup can be a long term solution. Good suggestion, I will explore further.

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PostPosted: Mon Aug 27, 2012 3:37 pm 
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Happy to donate some upside down time if I can help!


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PostPosted: Mon Aug 27, 2012 4:37 pm 
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I may take you up on that :)

I had a splitting headache after fitting the thing initially.

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PostPosted: Mon Aug 27, 2012 7:12 pm 
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sorry - linky
http://www.leespring.com/uk_index.asp

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PostPosted: Tue Sep 04, 2012 1:37 pm 
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Hiya guys,

I have only just seen this post as i am busy back in hospital. Unfortunately i have not got any soloutions to this but what i wanted to say is that the speed thing about JAE is irrelevant now due to readmission to hospital and will be in here for some time due to many a *bleep* up, { Dont worry i wont bore you with the details :)} but the end result is i am now having to have more surgery to remove more of the leg, also been transfered to Brighton which is a right pain with a minimum ...very minimum stay of a month but looking more like a minimum of 2 months as they are now going to have to do 2 operations {waiting for one to heal partially and stop bone infection AGAIN, then to kill tissue infection}
I'd also like to say once again thanks for continuing your efforts in Chris's search to this problem for me

Thanks.....Hopefully i'll get to drive her again sometime and meet up again


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PostPosted: Tue Sep 04, 2012 4:27 pm 
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Was very sad to hear your news

Hang in there Chris


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PostPosted: Tue Sep 04, 2012 10:13 pm 
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:shock: jees mate! you're not having a lot of luck right now.
Really distressing news but, on a positive note, at least they'll keep you in until it's all sorted properly this time and at least when you're discharged you'll be on the road to recovery.

I'm sure Ezzy will be waiting for you.

I would publically like to take my hat off to Chris for his sterling effort
...as to everyone that has helped out - this means alot to Jingo.
...and indeed the GT4DC community - IMHO this is what its all about.

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PostPosted: Tue Sep 04, 2012 11:14 pm 
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Also hats off to the CCUK community who have rallied round and stumped up the cash to buy the duck clutch and provided emotional support for Chris.

Two very special clubs in their own different ways IMO.

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PostPosted: Tue Sep 04, 2012 11:20 pm 
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That's terrific! I don't have any ST165 specific parts but if you need anything more generic from my 'pre-loved' parts stock I would be happy to donate FOC.

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