Slipper Clutch

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Has anyone got any ideas about fitting a slipper clutch to a commando - what clutch centre is relatively cheap and could be easily modified to fit ?
 
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I was thinking of the thread about using the 4 speed CR box and how it might be made OK if it had only first gear low enough to get the bike mobile when moving off from traffic lights. If you used that setup an accidental change down into first gear could be dramatic.
 
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acotrel said:
Has anyone got any ideas about fitting a slipper clutch to a commando - ... ?
Heinz Kegler built one.Have a look at this thread.

It's basically a std clutch centre but the linear grooves are changed to a spiral design which creates a ramp effect at the inner teeth of the clutch disc pack.


Tim
 
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Thanks for that link, it is very interesting. The prices for modern slipper clutches seem very high. I think I will try to have a look at what is being used in superbike racing these days. The angle machined Norton clutch centre looks at though it is more intended to stop slippage under acceleration rather than allow it on back-off.
 
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The need of slipper clutches has to do with the corner crippleness of all non-compliant tri-linked isolastic cycles and lack of pilot skill as is easy to find out riding with spirit on THE Gravel. The moderns have issues with the innate power character of hi power engines that hit & miss with the reasonations of cam and exhaust evert few 100 rpm changes, so they can't just ease off throttle and expect a constant predicable engine drag so they have to slow up sooner or ease through turn on light throttle or light braking - the poor dangerous things. Going fast and trying to use rear tire/engine drag to slow is rather counter productive, so one Commando I know just avoids that all together. What is usefull in Kegler type design is the engine torque helping to clamp plates together which is opposite of slipping, sheeze.
 
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I was thinking more of the situation where a 4 speed CR box with a very low first gear is being used. If you pick up first gear unintentionally without giving a heap of revs, the result can be nasty. Even the standard commando box can give problems in regard to smoothness on down changes especially in the wet.
There was this in Ian's link :
There are several types of slipper clutch but the Ducati version is one of the simplest. The original clutch put on ducati's is a purely mechanical device, when the throttle is closed and the rear wheel starts to turn over the engine a simple system of 45 degree ramps (with or without ball bearings, depending on budget and manufacturer) inside the central drum forces the drum up against the outer pressure plate, so forcing the clutch plates apart. As soon as the clutch starts to slip the forces holding the clutch apart are controlled and the clutch is held in a perfect slipping situation, just enough power is transmitted to maintain the equilibrium. In a normal driving situation the clutch operates just like any other.

A TTI 6 speed box is $6000. A four speed cluster $700 for a commando and a slipper clutch is about $900. With a 6 speed CR box behind a commando engine , a slipper clutch should not be needed - the crank is too heavy to over-rev easily on down changes - easy to ride smoothly. First gear is the only drawback with the 4 speed CR box.
 

madass140

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"First gear is the only drawback with the 4 speed CR box"
are there not alternative 1st gear sets available , either for the 4 speed CR or stock tranny?
 
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madass140 said:
"First gear is the only drawback with the 4 speed CR box"
are there not alternative 1st gear sets available , either for the 4 speed CR or stock tranny?
There are plenty of low first gear pairs available, for the commando box - the problem is that if first gear is low enough to get a good start in a 'clutch-start race', the step up to second gear is very large. It is not a problem moving up through the gears. However coming down and using first gear anywhere else you need a heap of revs. It makes a crash likely unless there is some way of preventing the hesitation in the back wheel when it tries to accelerate the internals of the motor. I had the same situation with a Suzuki T250 racer I built. The Yamaha TD3 always had first gear not much below second, if you accidently changed down to first on the Suzuki during a race, it was not good.
I think I will end up fitting a lower first gear to the 6 speed TTI box, and I've been looking for a decent photo of the internals of the Ducati slipper clutch. When I ordered the TTI box, I specified that first gear should be between first in a commando box and first in the manx box. You might not believe this stuff makes a difference, however it does. The original commando box is not up to high performance - a major design flaw. The bike is totally different when it has the top three gears close and high.
 
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The 70s Triumph 5 speed box is OK, however until recently Phil Pick was supplying two pairs of gears which moved 2nd and 3rd up a bit. I don't believe the step up between 4th and top would have been large as standard. You don't usually have a problem unless you lose count of your gear changes on a tight circuit. You always need to know where first gear is if you are getting balked.
 
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Peel is going against the grain with 4 wide ratio's d/t rather less need to accelerate out of turns and hopeful wide enough rpm range the torque is still tire testing. I don't shit my handy modern while hard over hard on it or can stand up hi side so another reason I'm so sold on linked isolastic as could cut throttle or snick up or down and nothing happened - but as using the 850 AMC ratios I'd have to almost hit 8000 rpm not to bog snicking 3rd. Alan has sensed the friction factors of waiting for lower gear ratio to rev up vs taller gearing that got the most out of pure toque for slower reving engine but faster longer pulling cycle. My so so 10,000 rpm SV650 with 6 spd is rather throttle sensitive d/t its gearing to keep engine spun up so engine drag reaction is higher than a Norton with heavy flywheel and taller gearing. i have to dig down 2 gears on SuVee to egual the pull of my factory Combat and then still runs out of torque rise so the Combat is rather guicker above 90 mph in 4th.
 
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I have found the commando motor very strange to live with. You really know it has that heavy crank and long stroke. However once it is spinning it holds a lot of energy. I don't believe close ratio gearboxes are good on the dirt - probably better to be less jerky. I am amazed how hard my motor pulls, I've ridden an extremely good Triumph 650 and it goes nowhere near the commando for torque. I believe a lot of guys don't try to really gear up their bikes because of the spacing of the gears in the standard box. I found that with the CR 4 speed box on our local race circuit, I don't need to go below 2nd gear except during a clutch start. As I've raised the overall gearing the bike has still accelerated extremely quickly through the gears from 2nd to top, and it is difficult not to over-rev on the up changes. I think that when the bike is under-geared it gives the impression that it is accelerating as hard as it can, and until you take a tooth off the rear sprocket you don't realise it was not pulling hard enough. I always find it hard to watch the rev counter, however I believe that when I've been practising that once the bike is up and going it revs between about 6,200 and I try to keep it below 7,000 ( usually see 7,500 on the up-change). I never see 5000 RPM.
When I first raced the bike, I used the standard commando box - I can't ride it like that in a road race - you just look silly, you can't do anything with it. One of the so-called experts once said to me 'if you've got a torquey motor, you don't need a close ratio box' - I think a lot of these guys run on supposition. He'd obviously never used a close box.
 
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Steve,
'Alan has sensed the friction factors of waiting for lower gear ratio to rev up vs taller gearing that got the most out of pure toque for slower reving engine but faster longer pulling cycle. '

I don't believe it is 'friction factor' as much as it is crankshaft inertia. If you change down from 2nd in the CR box to a very low 1st without giving the motor a heap of revs, you are expecting the bike to perform convulsions. In the wet or even on a slippery surface in the dry, you would probably crash. A slipper clutch would probably stop that from happening.
The 4 speed CR box is magic everywhere, however you cannot afford to lose so much during a clutch start in a race.

I should point out that I probably have a strange approach to road racing. I raced at a major disadvantage for about 12 years with my short stroke 500cc Triumph. On only one occasion was I able to really cream the fast guys. I softened the suspension, lowered the tyre pressures and dropped the gearing right down, then blitzed them off the start and led them for a lap. The fast guys were riding Z900s and H2s, got me at the end of the back straight, then found they were going too fast. I had to stand the bike up to miss them and ran off. What it came down to was you could choose where you were going to lose a race.
 
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able to really cream the fast guys. I softened the suspension, lowered the tyre pressures and dropped the gearing right down, then blitzed them off the start and led them for a lap. The fast guys were riding Z900s and H2s, got me at the end of the back straight, then found they were going too fast. I had to stand the bike up to miss them and ran off. What it came down to was you could choose where you were going to lose a race.
Fun stuff Alan that is similar to setting up for the worst handling tests - off pavement. I've much to learn but already learned - never let cycle 'get ahead of you' like going too fast into turns and if it surprised you shame on you for not already learned what not to do. Total power don't mater to handling near as much as how much of that power can be put down in tough places compared to others. I sure liked Peels powerband which corresponded more with my intended emotional sense reactions to control forces compared to others that would respond too much or not enough to match what I wanted it to feel like just then. The closer to out of control ya get the more the slower subtle differences are magnified. What I found works best for me/Peel is what works best on bad non paved surfaces so behaves similarly going harsh enough to make the best surfaces about as loose yet w/o much slip sliding time/traction wasting intervals.

The games played in my area get slightly strung out by the power/wt pecking order and don't much below 90's until 20-10 mph marked turns then moderns get down to upper 40's while Peel entered 50 or more and for her going slowing enough could be on good throttle all the way around from there. Most the turns are 35-45 marked where moderns are almost able to double the speeds after braking like crazy for it, but this is where I became most focused on which gear to enter turn in so would down shift at WOT throttle till I felt rear want to jerk out from under either side I slightly leaned towards so knew traction to work with then when in on WOT increasing power band power steering by a little tip this to snatch to pegs then ease throttle so full hook up accelaration with flywheel and wheel spin energy boost to straight up hooked up then as turn decreased and power band too, more than keeping up with increasing traction at higher speed would tip and jerk forward as many times as needed to run out of rpm and snick 2nd at 60 or 3rd at 90. I found the speedo is my most useful meter as its hard to judge speed in the heckic states with others to avoid and only a few mph difference beween safe but not fast enough vs out of control right off the game board. Peel would run out of my rpm fear a few 100 below 8000 when putting eyes back on aim point so came dang close a lot of times or would of been left behind in bog of 3rd till ~110 then 4th would carry the day pretty good not to get caught or passed till most a mile opens pure hp rules the roost.

I have to creep about a lot so got granny stump pulling low which should make parking lot burn out stunts on tap yet pull a slow loaded crawl up very steep stuff I don't want to be charging like a hill climber. A big jump to 2nd good from 40's to over the ton then a fairly short jump to 3rd good to 130's then 4th hopefull to at least 160.
After the ton ya don't need much power to break free in skips of rear &/or front but just staying on power and turning sharper leaning more. Its sort of crashing in anger some ahead of time on your terms then spend the rest of the turn where everyone and their sister is going crazy on restrain increasing loads, I'm doing everything I can to relieve all loads and crash just right exiting. Basically wind it up hard then let go for the whiplash thrill in the tighter spots. if only 45' leans then its just a hp power event again with wheelie control limit full power planting. So I'm also thinking the wide ratio will bog Peel down enough in sprints to just float front level til next front tap down back to level flight. If ya got great power to wt then can skip some gears like Peel will do in standing starts in 2nd with some clutch slip before getting on hi throttle. Figure the wide ratio more practical for a side car too.
 
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I tend to ride the bike both up and down through the gears. I sometimes watch the kids at ride days. Some of them click down two gears in about 3 metres, and the back wheel can sometimes hop about 100mm into the air. It is a really bad habit to get into. I'm a bit paranoid about it - I was brought up racing on rock hard tyres. To my mind the commando is superb, very safe especially with modern tyres and that smooth, strong power delivery.
 
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If ya are using engine drag while trying to go fast - oh well then ya run into all the risks of going down too fast or having to slow up too much to allow engine braking to be effective while being passed so easy by those with good braking sense, The problem is if geared low to take advantage of engine rpm torque multipling then much throttle cuts can hop skip jump the rear out of control. Modern divices take away pure pilot skill bragging rights, slipper clutches to force brake skill which now have ABS interface and traction and wheelie control programed to each track section so pilot can keep WOT and let digital brains work for them so next step is just pure robotics the pilot is along for the ride, ugh. Part of Peel's appeal to me is no interfaces between pilot and tire patches so more fun wiping sneers off strangers attitudes the old fashioned way. I am flabbergasted by the ice skater accuracy of tire behavior when aired very hard but only on flexy-retrained Peel which someday will learn how to bunny hop her going straight and at apexes... but not on fatso tires that walk all over their wide patches like people with arthritc hips and knees...
https://www.youtube.com/watch?v=0026xAUP4GY
 
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I don't have a problem with kids using slipper clutches, they obviously make bikes safer. My concern is that they help accommodate bad habits. When you eventually find yourself in the extreme situation, it is very important to do the right thing. With the old garbage we ride, that situation usually occurs at a relatively low speed. With a modern bike it becomes a very big get-off and much more likely to lead to a death. One of the things I do when practising and racing is ride faster into the corners and out until the bike goes slightly out of control. That is why I tend to stay away from modern bikes - I could end up as a wrinkly bag full of bone chips.
 
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Yep Sir Alan to me the vintage can't get going well enough to please and the moderns get unpredicable surprise reactions beyond the power & speed of humans to react too in time, so I've given up on everything but Ms Peel thrills. I learned to over come the moderns faults to pull off Phase Three and Phase Four Energy handling w/o slipper clutches but then so so many things vibe and splash its too much work/athletics/risk to me for such small increases in acceleration through turns beyond the slow pokes remaining in fear to exceed counter steering limits. Time to time ya'll see video of front tire lifting at apexes [not the wheeelies existing] and goes viral on how good bike and pilot are to save the crashing - pashaw that Peels main advantage zone and rear hook up on throttle cuts is vital to me. We are a dying breed that got to live through to this robotic age and soon enough with fuel cell powered electrics only robots will be competition to Peel. Robo cycles do not counter steer and Tony Folale cycle handling treatises don''t cover this level of motorcycle physics.
 
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