# Finger Engine Clutch"



## Captain Jerry (Aug 13, 2011)

Hi All!

This is an offshoot from an older thread from 2008 that got revived because of a more current thread about finger engines. I thought it more appropriate to start a new thread because it has taken a different course. The parent thread can be found at
http://www.homemodelenginemachinist.com/index.php?topic=2063

It is worth the time to take a moment to read that thread if you haven't already.

This thread is aimed at building a finger engine that uses a clutch or other method to decouple the finger treadle from the flywheel so that the flywheel will continue to freewheel after treadle action stops.

There have been a few ideas and suggestions offered. So far only Arnold and I have jumped in, but there is plenty of room for everybody. The rules are simple. The above paragraph is all there is.

Arnold thought that he would get some shop time on it today and so did I. My shop time was spent mostly looking through the pile of discarded parts from other projects. I found what I was looking for and cobbled up a mock up as shown here:







It make take some imagination to understand. Imagine that the small pinion is on a shaft with a flywheel. When the free end of the treadle is depressed with a finger, the gear segment pivots on its bottom pivot pin and is forced into mesh with the pinion and drive it clockwise. At the end of the power stroke, the gear segment pivots out of mesh with the pinion and is returned to the lower position by a spring. The process repeats.






Position, clearances, springs, stops have still to be worked out, but that for tomorrow ( or later)

Arnold, how did you make out?

Jerry


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## Ken I (Aug 14, 2011)

Jerry, I played around with the spring clutch idea - it will work but as Noitoen said the friction will slow the flywheel down pretty quickly.

A roller clutch (balls can do as well for low torque) would work - consists of an outer hub with the surface rad inclined by 2° at three points forming 3 "wedges" when turned in the one direction the rollers (balls) move to the open end of the "wedge" when turned the other way they lock into the wedge.

No springs required as gravity will drop at least one roller into the wedge.

A fiddly bit of work for the rotab.

Ken


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## arnoldb (Aug 14, 2011)

Nice going Jerry Thm:

Ken, that's one of the solutions I looked at. I settled on a slightly different method though - just need some time in the shop to build it.

 :big: What was supposed to be a quiet weekend for me turned into a social fest with a steady stream of visitors and partying; I didn't even get to unlock the shop, never mind build anything.

Regards, Arnold


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## Noitoen (Aug 14, 2011)

I remember when I was a kid, once I saw an artisan turn some wood souvenirs with a "man powered" wood lathe. The lathe structure was very crude, mounted under a tree. A flexible branch of the tree acted as a spring with a piece of rope tied to it hanging above the lathe's shaft, went once or twice around the shaft and the other end of the rope was tied to a wood plank that acted as a pedal. When he pressed the plank it would spin the shaft and as he released the pressure the "branch spring" would pull the pedal back up and let the shaft spinning due to a small flywheel.

Here is another version http://www.wood-lathe.org/articles/a-brief-history-of-wood-lathes


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## Blogwitch (Aug 14, 2011)

I am unable physically to join in the fun on this little project, but that doesn't stop me thinking about ways to get the drive from the finger treadle to the flywheel gears.

I don't know if anyone can understand this C-o-C, but with a little bit of fiddling, this should be able to be got to work. Maybe a second spring would be required under the finger button to allow it to retract a little quicker. The only problem I can forsee is getting too much pressure produced between the taper and cone. That could be solved by having the fixed taper that the shaft taper runs against to be slightly spring loaded, or even an o-ring in a recess instead of the internal cone against the taper.

There are most probably hundreds of ways of solving this problem, so even if you aren't going to make one, how about knocking up a C-o-C to give your ideas to the subject.


John


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## dmac (Aug 14, 2011)

What about using a one way bearing.

Something like this.

http://www.smallparts.com.au/store/partslist/bearingsonewayspragtfs/bearingsclutch/wide/1/


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## Captain Jerry (Aug 14, 2011)

dmac

Sure a one way bearing would work but that's so easy, it was the one solution that was ruled out. For the purpose of this discussion, project, or brainstorming session, the clutch mechanism must be shop made. 

There have been some good ideas proposed and the way I see it, all of them could be made to work. There is no time limit on this project so if something pops into your head, tomorrow, next week, next month, build it, draw it, model it, or just describe it.

One of the things that I have been wrestling with is the fact that a finger engine treadle operates over an arc of no more than about 20 degrees. So the clutch must actuate in a small fraction of that if there is going to be any arc left to provide power, and it must disengage cleanly without robbing any energy from the flywheel. Lots to think about.

Another idea hit me this afternoon and you have probably seen it in music boxes and wind-up toys of all kinds. It uses a drop out pinion between the driving gear (attached to the finger treadle) and the driven gear (attached to the flywheel). The pinion is fixed on a short axle shaft that moves in a short slot that keeps in mesh with the driving gear. When the shaft is at one end of the slot, the drop out pinion is also in mesh with the driven gear. When the driving gear stops or reverses, the pinion is pushed to the other end of the slot, un-meshing with the driven gear and letting it freewheel. That should be easy to build. If I had another pinion laying around, I would give it a try.

Jerry

Jerry


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## Noitoen (Aug 15, 2011)

I just thought of another mechanism. Those "pull-back and release" toy cars have a sort of multiplication system that gets the car to run fast and far with a little pull-back movement. Should investigate how it works


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## Captain Jerry (Aug 15, 2011)

Here is a quick sketch of the drop out pinion. The finger pedal would be directly attached to the large gear on the right.

Jerry


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## Dan Rowe (Aug 15, 2011)

Jerry,
If you made the top of the pinion teeth pointed instead of the usual flats. The posibility of the flats hitting when they rengaged would be elimated which was the problem I was having thinking about a gear design.

I like that one.

Dan


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## Captain Jerry (Aug 15, 2011)

Dan

I think you are right about that. The two gears meshed and ran well when the centers were at the correct distance. They got a little rough when I cut the drive gear quadrant and drive it into and out of mesh. I took a file to both gears and eased the corners off of the teeth and the action is much better. Thanks for the suggestion.

Jerry


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## arnoldb (Aug 21, 2011)

;D I finally managed to get 5 hours in the shop today...

Built some crude bits from odds 'n ends lying around:





And a base:





I tried to do a ratchet drive that will use the inertia of the "crank" movement to engage the ratchet, and once it goes beyond a certain point will automatically disengage. A spring below the "finger" (not built yet) will pull back things for another stroke. Things don't quite work like I wanted it to though - it only half-works which is no good for me. 
There is too much friction between the outer ring and the inner "drive" bit with the ratchet on, and it is a bit too light as well as it's made from aluminium , so it does not provide enough inertial resistance to properly engage the ratchet. The ratchet mechanism is a wee bit shallow as well, so it's back to ye olde papyrus and pen for those bits.
 ;D Already have a plan; just need a bit more shop time.

Kind regards, Arnold


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## lazylathe (Aug 21, 2011)

Looks great Arnold!!!

Just making the flywheel would take me forever!!!!

Andrew


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## Blogwitch (Aug 21, 2011)

If I could give you a clue to getting it to work correctly.

Have your treadle driving a fairly large gear rather than direct to the flywheel, then the large gear driving a smaller gear connected to the flywheel.

Doing it that way, most of the energy you produce from the very short stroke of your clutch will be driving the flywheel a little faster each time and so storing that small amount of energy you are able to produce each stroke.

That is the way Bill Reichart managed to get his to run.

Without that addition, I don't think you can generate enough flywheel momentum to keep things going, unless you can say extend the drive treadle driving part to give a lot more than just a part of one revolution to the flywheel.

As I stated when we first discussed this on the other link, I had already looked at different methods of clutch to see if the gears could be done away with. But when you study the original plans in detail, you can see why the gears need to be in there, and I think the exercise was only to come up with a new clutch system rather than the roller variety.

I hope you can understand my ramblings.


John


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## Captain Jerry (Aug 21, 2011)

Bogs

Your ramblings make perfect sense. I may be slow but I'm heading in that direction. The planets may revolve about the sun many times before I'm finished.

Jerry


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## checkedout (Aug 23, 2011)

Would something like a bendix gear work?

Is that essentially what you're already doing there?

(please excuse my noobishness)

Is that also the kind of gear that allows your feet to stay stationary when you're coasting on your bike?

Just trying to understand if a modification of that sort of assembly may work.
Or... if not, why not?


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## Captain Jerry (Aug 24, 2011)

checkedout  said:
			
		

> Would something like a bendix gear work?
> 
> Is that essentially what you're already doing there?
> 
> ...



Checkedout

I don't know how the bicycle coaster brake works but in principle it seems like the same thing. The bendix uses a helix to drive the starter pinion into mesh with the flywheel gear. I think the problem with that is that the helix has to make one or more revolution to engage.

As I see it, finger engine treadle makes less that a 1/4 revolution per stroke and the clutch mechanism must engage in a ver small fraction of that stroke. It must also disengage completely and instantly at the end of the stroke.

Bogs

I understand that gearing would allow the small input arc to transfer more energy to the flywheel. Would a LARGE flywheel give the same action. More inertial resistance to absorb more energy on the short stroke?

Jerry


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## checkedout (Aug 24, 2011)

Good point Jerry.

Thank you.


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## Captain Jerry (Aug 25, 2011)

While thinking about all of the possible ways to make a one way clutch I kept avoiding the most direct approach. Instead of gears, wrapped strings or springs, how about just a clutch? You know, one thing rubbing against another thing. I drew up an Alibre' model Tuesday night, made some parts Wednesday, and fiddled with it today. I didn't really get it finished but I got close enough to do a trial assembly and test. There is no base, and no return spring, the flywheel is my plumbing parts baton and there are some minor revisions to be made but it works surprisingly well.

I didn't get any build photos and only a couple of videos of the trial. Here it is:

[ame]http://www.youtube.com/watch?v=o-LvTNnPeg8[/ame]

I haven't decided on the final mounting but I will work on it tomorrow. I will take it appart and try to get some pics of the works.

Jerry


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## lazylathe (Aug 25, 2011)

That is a really cool design Jerry!!!
Works a treat too!!

With a return spring and a stop to position the lever in a handy place it will be perfect!!!

Seeing how the clutch works would be great!!!!

Excellent work!!!! :bow:

Andrew


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## Ken I (Aug 26, 2011)

Aye Aye Cap'n.

That works well - can't wait to see how you did it.

Ken


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## Captain Jerry (Aug 26, 2011)

Here are the parts for the one way clutch.







The actuator freewheels on the shaft. Right now it is aluminum on a steel shaft. I plan to insert a bronze bushing to reduce friction. The diameter of this and all other components is 2".






The clutch cam carrier also freewheels on the shaft and will also get a bushing.






The clutch cams mount on the pivots of the carrier plates and the slots on the cams engage the drive pins of the actuator.






The action of the clutch depends on a small angular displacement between the carrier and the actuator. On the power stroke, the cams are driven outward against the inner face of the drum. At the end of the stroke, the carrier plate stops as the lever comes to a stop and the momentum of the actuator plate moves the pins in the opposite direction and pulls the cams away from the drum providing instant disengagement for the return stroke. The last part that mounts on the shaft is the drum and it is the only part fixed to the shaft.

The gearing is salvaged from a discarded cordless drill and provides a 5:1 increase.







I will get some more video after I get it cleaned up and mounted.


Jerry


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## Captain Jerry (Aug 26, 2011)

Here is a video of the drum end where there gear action and the rotation is 1:1 with the lever. I know. Its a clunky set screw but it helps visualize the motion.

[ame]http://youtu.be/RkW2mLV0Syk[/ame]

Jerry


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## arnoldb (Aug 26, 2011)

;D REALLY Good going Cap'n J :bow: :bow:

Makes my little escapade today seem a bit dim, but I'll post it for interest's sake.

Cut a quick 'n dirty ratchet - used a dovetail cutter to get some angles:





Made some other crude bits; a new bearing for the column that extends out a ways, a ring to fit on the outside with a hole for an M3 cap screw and a small hole for a pin that will help reversing the ring, and a tooth to engage the ratchet:





Assembled it looks like this; a drill bit is still doubling as the reversing pin:




The multiple holes in the ratchet tooth was to test the effect of powering the lot at different offsets; closest to the center works best, and it's surprisingly positive.

It does run after a fashion:
[ame]http://www.youtube.com/watch?v=fjXpCuc3Ono[/ame]

John was definitely right; gearing would be best to get some RPM from the flywheel. I was in a bit of double jeopardy this time... Didn't follow John's current advise, but did follow some he'd given me many months ago: "Unless you try it you'll never know". Nothing like a bit of practical work to try something; at least I know I can make a ratchet now 

I'll try and complete it as-is tomorrow; I need to get cracking on my Cracker and a lot of tool-making jobs again, and am in no mood to cut some gears for now 

Kind regards, Arnold


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## Captain Jerry (Aug 26, 2011)

Hey Arnold,

Nice ratchet! Did you originally plan to hang it under the shaft like that or is that a revision? Looks like it does the job of engaging and disengaging well. John's advice is usually worth listening to, even if you don't follow it. I think the gearing is a good idea but I think you could get the same result with a bigger, heavier flywheel.

Thanks for taking the challenge and following through with a good result. That's one of the greatest things about this forum. A simple question gets a lot of good answers and leads to some new experience. 

One of the thins that John said is that there are probably lots of ways to do this and I'm going to explore a few more before I move on.

Jerry


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## lazylathe (Aug 26, 2011)

Nice work Arnold!!

Loved the shot of cutting the gear!!
I am sure you do not want to make too many of those in the future! ;D

Looks like it works a treat too!

Andrew


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## arnoldb (Aug 27, 2011)

Thanks Cap'n J & Andrew

Jerry, it's pretty much as I had in mind - I'll add a bit of a description of how things work in a later the post. Looking forward to your other explorations Thm:. 

Andrew, that milling shot is all wrong :-[ - Only after I set up everything I realised I'd have to climb mill to cut the grooves at the correct angle - so I went and did just that, but it's not good practice. This was a very quick job; everything by eyeball and gut feel; it took me less than half an hour for doing all the setup and cutting that ratchet gear... Proper gears take a wee bit longer :big:. Mind you, I'm not averse to cutting gears; in fact, I enjoy it and in the next couple of months I'll be doing quite a bit of that, but just not for this build.

Well, the engine is finished, and works surprisingly well ;D
Made some more crude bits:





All assembled it looks like this:










Definitely one of the crudest-looking things I built in quite a while Rof} - I'll call it "Rustic"

But it does run ;D (Apologies; I took this video in my kitchen and the TV was on, so a lot of background sound):
[ame]http://www.youtube.com/watch?v=FqwC1pXNthc[/ame]

Kind regards, Arnold


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## Captain Jerry (Aug 27, 2011)

Arnold

Call it crude if you want to but the challenge here was function, not finish. I think you passed on the function part. As far as finish goes...not too shabby. At least it's got all the necessary parts. You have shamed me into getting this thing FINISHED!

I seem to have a problem with that. I get to a point where something works, and I want to tinker with it until I works better. This project is a good example. I started fiddling with the clutch and discovered that there was a small amount of friction between the carrier plate and the drum, even with the cams retracted so I fixed that and then the clutch didn't work at all.

It turns out that this friction was providing the energy to engage and disengage the clutch. I guess that would be OK except that the energy to disengage the clutch was coming out of the flywheel. Not much energy but then, every bit counts. 

The aluminum carrier plate just didn't have enough mass to drive the mechanism the way I thought it would. I thought that might be a problem when I was building it but when I assembled it and it worked, I forgot about it. Well it worked but not the way I designed it and not the way I explained it in my last post so I had to fix it.

Here is the fix, a cast iron rim added to the carrier plate to give it the needed mass:






It came from a surprisingly convenient source.






Lowes cast iron plumbing parts are just that, CAST IRON. Not the galvanized cast steel that most plumbing supplies are. It added the needed mass and the action is greatly improved. You probably can't tell the difference in the video but the feel is unmistakeable. 


<VIDEO>



Now I can get to the spring, the stop, and the base.

Jerry


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## Blogwitch (Aug 27, 2011)

And so it goes on, at each step a little improvement. 

You guys are doing a great job of solving the problem, I just wish I could be in there with you.

I think you have both solved the drive problem perfectly. A purchased one way clutch bearing could do no more than what you gents have achieved.

It is now a matter to get the flywheel to increase in speed at each stroke, rather than frantically using the treadle just to keep the flywheel turning. 
Jerry's is almost there, shame you couldn't have got a bit of a higher gearing in there, but if you wanted to, you could call that a project achieved.

Just by tinkering about like this (I know you have put a lot of work into them) I think both of you have learned something about problem solving. Maybe you didn't learn a lot, but I bet both of you enjoyed the challenge.


John


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## Captain Jerry (Aug 29, 2011)

John

Thanks for the comments. This has been a fun challenge. I'm almost there and that has been the story of my life. This finger engine may never be finished but I was much more interested in the clutch than I was in the engine so I'm going to call that part finished. More gearing might help. I salvaged the planetary gears from a battery powered drill and only used half of it. The original gear set was a double reduction type where each gear set gives a 5.5:1 ratio so if I use both gear sets, it will give a ration of 30.25:1. That will really spin the flywheel or it may require more input torque than the clutch can handle. I think I will try another type of clutch mechanism before doubling up on the gears.

The two shoe cam clutch could be improved. Different material for the drum and the cams and a little different angle on the slots might give improved performance but I'm going to try something else. For my next trick, I'm going to attempt a "sprag clutch". This is another type of over running clutch that uses small wedges between the driving and driven parts that release when the parts change relative motion.

I have some ideas on doing this but if anyone has done this or has any some thoughts, please weigh in. This may be more difficult than I think. Clearances, angles, and shapes, Oh MY!

Jerry                                                                           1360


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## arnoldb (Aug 30, 2011)

Thanks John & Jerry

John, yes, I did learn quite a bit actually - and it definitely is a nice challenge to carry on with in future. I have an idea on how to make the clutch double-acting and I'll be keeping on the lookout for a set of suitable gears to gear the flywheel up a bit. And trying to figure out a way to make the flywheel run freely rather than have the gears still engaged when the pedal is stopped. Lots of tinkering to do on a rainy day ;D

Good going Jerry Thm:
I also considered the sprag clutch, it's a nice challenge to figure out. Gave up on it though; it would leave quite a bit of friction going without some way of positively disengaging it.

Kind regards, Arnold


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## Captain Jerry (Sep 1, 2011)

Here is my first attempt at building a sprag clutch.






It worked very well much of the time. Other times it worked not at all. It would refuse to lock up, and then for no apparent reason, wham! It would lock and refuse to release. For a first attempt, I was surprised it worked at all. There are so many variables! Angles, shapes, clearance, etc. I won't bore you with all my rejected ideas. In the end, this design won out because of the available material. I decided on cast iron for the inner and outer races because it is cheap and readily available. The local source for this is the plumbing department at Lowes. Imported Chinese couplings, bushings, and plugs in various sizes. Much cheaper than brass or bronze and harder and slicker than aluminum. I would have liked to use cast iron for the sprags as well but I couldn't think of a way to produce the small shape needed.

I decided on brass for the sprags when I found a strip with a rectangular cross section 1/4" x 3/32". For this attempt I actually milled concave faces and rounded outer edges to produce the "8" shaped cross section that I was familiar with in commercial clutches. I found out later that is really not necessary. These little brass sprags fit loosely into angled slots on the inner race. There is no spring pressure to press them against the outer race, They just sort of flop around in there and when the relative motion is in the free direction, there is plenty of clearance. About .020". When the movement reverses, the lock-up direction, the little brass sprags stick there heads up to see whats happening and wedge themselves between the races. Sometimes. Other times they would get stuck in the laying down attitude due to imperfection in the shape of the sprags and irregularities in the inner end of the milled slot. Other times, they would lock up but one or more would pivot over center and then refuse to unlock.

Here is my second attempt at building a sprag clutch:






In this version, the inner end of the slot is stopped with a polished 1/8" Stainless Steel rod. This gives improved control of the slot length and gives a line contact with the inner end of the sprag against the polished face of the rod. I made no effort to shape the sprags, except to file a bevel on the inner end. The function of the bevel is to keep sprag flush against the pressure face of the slot, preventing it from going over-center and insuring instant release to freewheel.

I will try to draw this up for a clearer understanding, but for now, here is a video. As you can see, my hands and the machines are covered with cast iron powder. 

<VIDEO>




As you can see, my hands and the machines are covered with cast iron powder. Tomorrow will be a big cleanup day, and then I will work out all the fiddly bits like bearings, shields, shafts and retainers.

Jerry                                                                     1530


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## Ken I (Sep 2, 2011)

Cap'n - that's really impressive work.

Good going.

Ken


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## Captain Jerry (Sep 4, 2011)

Thanks for the complement, Ken. Cast iron sure is pretty when its polished but what a mess it makes of the machines.

The sprag clutch is finished and mounted and is a big improvement over the cam clutch. It is more compact, has much less friction in free wheel, much quicker lock-up and release. I can actually get good torque transfer with only about 10 degrees of lever action. 











Batteries died before I got good video but I'll try again next week.

Jerry


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## dsquire (Sep 4, 2011)

To all

I like the way you have taken the finger engine to new heights by using a clutch. It is plain to see that you all have put a lot of thought into the design of this clutch. Each taking a different path to the finish line. All are to be congratulated for stepping up and taking the challenge. :bow: :bow:

Cheers 

Don (1700)​


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## lazylathe (Sep 4, 2011)

I did not really think that mentioning a clutch type mechanism would receive this kind of genius!!!!

It is amazing to see what happens on this site and the enthusiasm everyone puts into a thought or comment!

When i get around to building one i think it will just be a standard version! ;D
Maybe the clutch version will follow in time...

Andrew


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