Slipper Clutch, back torque limiters call them what u want

[dansoarr]

Ok, slipper clutches assuming that we all know what they are & the basic principle of operation (if not ask!)

I'm convinced that they are of serious benefit to the racers among us, & even to those of us that just have fun on the street or track.

But my latest race bike has not got one, & the idea of shelling out another £700 is painful (all racers are financially broke). So I pose the following question to you all.

I’ll give you my thoughts later, I tried this at work & told them my ideas & I got loads of expansion on the ideas but no new ones!

Given that the slipper clutch is essentially de-coupling the engine (crank) from the transmission, when the rear wheel speed is higher than the engine speed (for the given transmission ratio). Are we not tackling this from the wrong end? Should we not be limiting the engine characteristic so that the engine spins up to speed easily, i.e. no compression?

To aid this we all run high tickover speeds dependant on circuit, up to 3000rpm

Your thoughts please, Mechanical, Electrical

Arron

 

[mburgess]

Slipper clutch is usually made up of a ramp that forces the clutch open on a closed throttle. Not a new idea, I have one in my 1991 model kawasaki (standard). To get set up correctly some clutches will have different rate ramps & springs. Most racers will make do with a high idle speed. There are a couple of aftermarket brands arount STM is proably the best known.
Regards,
MB

 

[mburgess]

Errr, in terms of operation I still get some chatter from the rear wheel at lower speeds but can really knock down several gears at higher speeds. I still run a high idle speed but only about 2 to 2.5k. The more modern ones may work better but have not used one.
Regards,
MB

 

[dansoarr]

Ok, I know about the ones you can buy, I've had STM, Sigma & Suter. Ther's no question on thier operation or benefit, some are better than others, suter was the best I've had.

The question is not what is out there but what else could we do in stead?

for example, why dont we run 5000rpm tickovers, cos at hairpins we'd get pushed through the corner etc.

So what would the benefit ( under heavy braking, for a chicaine) be of telling the Fuel injection the throttle is shut (so only put in fuel for 2500rpm) but the throttle bodies are actually held fully open. therfore less engine braking? ingnoring the issue of transition on and off etc. Just alternatives to the ramp style slipper clutch

Arron

 

[kcj]

With throttle bodies held wide open, (no fuel injected) would you not have MORE engine braking? the engine is acting as a compressor at that point, and manifold pressure is very low with throttles closed. Throttles open, manifold pressure is close to atmospheric and more compression work is done by the back wheel turning the engine.

kcj

 

[thundair]

I had a 750 Ninja and if you wrapped it up in second about 11000 and let off all of a sudden it would completely lock the rear wheel. Scary....

My FZR1000 had a dog bearing on 3 clutch plates and only worked in forward motion...The bad thing about that is there must have been a design flaw, as the clutch gave up the ghost and locked the rear. Put me on the ground..

My thinking is why have any motor braking it will put you much deeper in the corner and you'll be so surprised when you make it through....

Cheers

 

[dansoarr]

Well I sort of agree, the principle of compression vs the effort of pulliin the mixture of air in to the cylinders.

What I can say is if I get an injected bike to 9000rpm in first and kill the engine on the stop switch with the throttle dropped to idle & glide to a stop on engine braking, I stop a lot quicker than if I do the same with the throttle wide open.

Arron

 

[dansoarr]

Reduced engine breaking also helps maintain corner entry speeds, & yes most racers could go a ot quick if they had the bottle. Do it once and you find that you repeat it.

One of the bigger benefits of a slipper clutch

Arron

 

[mburgess]

You could do what yamaha did with the M1 & run a servo motor to independantly control two of the throttle bodies. Open them slightly & feed fuel, for two cylinders only on overun. The whole thing was mapped for gear & rpm.
The whole idea is to control rear whell chatter/hop under heavy braking.
Regards,
MB

 

[kcj]

I wrote too fast, before thinking that through. When I see it in print, duh.

Yes, there should be more braking with throttles shut, as engine is acting as vacuum pump pulling through the butterlfies, doing work.

With throttles open, more air mass goes through but there isn't the throttling loss to suck against. The work put into compression roughly equals the work gotten back when the compressed air expands on expansion stroke, so that is somewhat of a wash.

One of the differences between gas engines and diesel, not as much engine braking with diesel, no throttles.

sorry for misinformation

kcj

 

[waross]

Didn't Honda used to have a "Flywheel" circuit on one or more of their highway bikes? As I remember, it was a method of delaying the throttle closing so that you did not get excessive engine braking when reducing throttle position.
respectfully

 

[R1100S]

I've heard of several MotoGP and other race teams trying what you are suggesting. The main problem they have is with the rider. It is easier for the rider to adapt to engine brakeing or a slipper clutch that to the inconsitant engine braking the servo controlled butterflies produce.