Boost Opperated Lock Up Clutch?

[slingy1052]

Ok, was doing my usual pondering over random stuff on my daily commute home, and i was thinking of the whole Lock up clutch thing.
The standard snowflake style ones are tried and tested i know, but seem a bit of a comprimise on a street turbo bike, or any turbo bike to some deggree as torque isnt very linear to RPM and as RPM creates the centrifical force to hold the clutch, the setting of it is going to be tricky. Then theres the noise etc as well, and to tune it, you have to pull covers etc.

So, i was thinking what would be cool would be to use the boost pressure to assist the clutch spring pressure thus when ever boost is pressent, the cluctch is locked , and the more boost the more locking effect, plus it could be tuned by means of blead screws (ie boost controller) or even by ECU to give multistages of grip or to even release to save transmision componants as a safety valve .

But how to do it simply.......... What if you did something like, for example, with a GSXR/Bandit type motor, use a 750 clutch cover (suitably spaced to clear 1100 basket), make a new larger pushrod end with a thrust bearing to push on the outside of the pressure plate, then make/extend the clutch arm to gain more leverage and use an aftermarket style external wastegate actuator (probably with spring removed so just a diaphram) to push on the clutch arm.
Clutch is still opperated like normal with the hydraulic slave, which will just push the diaphram in a pit when the clutch is lifted , but when boosting, it will pressurise the wastegate actuator and push the clutch pressure plate in harder.
Just need someone smart like Arttu to verify the math as to if enough force could be generated to asssist, I think it easily would but would depend on the area of the diaphram (bigger would be better) in the actuator and length of the lever.

Anyway, just thought i'd throw it out there, its probably already been done or being used on some vehicle somewhere or has some major flaw i havnt thought of.

[slingy1052]

Ok, so I have found 1 that is made by NLR. Looks like it can be fitted to any cases, but is expensive, and seems to push directly on the clutch, so diaphram is very large. Using mechanical advantage, a smaller diaphragm could he used I think.

Any racers out there using the NLR one?

[katana]

A few of the SSB boys are using them this year. Andersen came out with one probably 10 odd years ago - see piccie.
They do require fairly sophisticated air control usually from a separate air supply which is also used for boost control and the air shifter. Its a neat concept but could have limitations for a road application.

[slingy1052]

Cheers Katana,

The picture looks exact like the NLR brand one I found. It said on their website that it just runs off boost, but that N/A bikes could use it with compressed air

[katana]

Yeah Seb at NLR used to be associated with Andersen so its understandable its a recycled / probably updated design. Air control on SSB / Prostreet bikes is everything and NLR make some of the best control systems for that purpose. I've got a design for an air over slider clutch on the PC somewhere which isn't from Andersen but deffo not suited for road use!

[arttu]

Yes, a boost operated lock up would have some benefits in street use compared to centrifugal version. It would add clamping force exactly when needed, when there is boost/torque. And clamping would be released when throttle is closed.

Nice idea to use release lever to apply clamping on the pack. I don't see any fundamental reason why it wouldn't work. You should be able to generate enough force, it's only question of lever ratios and actuator cross section area. I haven't done any calculations but I guess it would be wise to add lever ratio quite a lot to get enough travel for the actuator and decrease required force from the actuator. Otherwise you probably will need quite large actuator. Some potential problems that came to my mind are the thrust bearing and flexing of the clutch cap plate. But probably these wouldn't be problems. Required clamping force won't be significantly higher than what is normally needed to open the clutch.

[slingy1052]

Jun 21, 2014 7:23:59 GMT arttu said:

Yes, a boost operated lock up would have some benefits in street use compared to centrifugal version. It would add clamping force exactly when needed, when there is boost/torque. And clamping would be released when throttle is closed.

Nice idea to use release lever to apply clamping on the pack. I don't see any fundamental reason why it wouldn't work. You should be able to generate enough force, it's only question of lever ratios and actuator cross section area. I haven't done any calculations but I guess it would be wise to add lever ratio quite a lot to get enough travel for the actuator and decrease required force from the actuator. Otherwise you probably will need quite large actuator. Some potential problems that came to my mind are the thrust bearing and flexing of the clutch cap plate. But probably these wouldn't be problems. Required clamping force won't be significantly higher than what is normally needed to open the clutch.

Yep, i was trying to think of a way it could be done at a level where the type of folk who have enough knowledge and skills to put together a turbo setup could put together a boost opperated lock up as well, rather than forking out the cash for a MTC style one.

Also, i wonder if bikes like  GS and GSX with cable opertated clutches could be made to release and lock clutch with the same mech?
I know anything is possible , just need to gather data to work out if its doable or not.
Anyone know what rating a standard gsxr or gsx clutch spring is ?
Need a good actuator with a bit of travel to allow for standard clutch disengagement travel multiplied by the lever ratio. I'm picking maybe 25-30mm of travel. Something like a large cruise control actuator would be good.

How much extra clamping force would be required over stock spring spressure to stop slip, say at 15psi boost? 50% more? 100% more?

[slingy1052]

Ok done some research but finding it hard to find data on spring rating of stock OEM springs.

The best i can find is some reference on some drag racing site to have the static clutch pressure set to about 160 - 180 lb of pressure, then add lock up pressure to this figure.

So i have done some rough calcs based on adding 200lb of lock up pressure (at 15psi boost) to double what static should be with a bit of margin.

So, i measured up the 750 clutch mech, the pinion has a 8.5mm radius, and the stock cable opp lever is 44mm centre to centre, so this gives us a 5.2 lever ratio.

So if we divide our required 200lb lock up pressure by 5.2, this will give us what we need from the actuator.
So the actuator needs to deliver 38lb of force.

we divide 38 by our 15 (psi) to see what surface area of diaphragm is required to generate the required force.
so this is 2.6si . This equates to a diaphragm 1.8 inches or 46mm in diameter.

This would be the minimum required i think, but if we increased the diaphragm to only 60mm diameter ,this would actually give us 340lb's of extra force at 15psi.
So generally i think a very compact system could be made to work for little cost using alot of junk yard available stuff. The 2 nasty's are 1) having to space off the 750 cover(unless a franken cover made up from the 2 was made) and 2) the thrust bearing required to push on the clutch pressure plate. Maybe the oem lift bearing could be used in reverse, other wise a specific bearing would have to be sourced. Maybe even the clutch bearing from a small el cheapo car could be used?

Generally i think its a doable exercise i might look into once i find i need a lockup, unless anyone else wants to experiment?

[slingy1052]

Just done a few more calls and 200lb can be generated by a 100mm piston/diaphragm acting directly onto the clutch.
A 150mm piston/diaphram could generate 424lb of force.
All based on 15psi boost. But obviously would be fully proportional, based on the reference pressure. This would be similar in size to the NLR unit in previous picture. So that is another option, to machine up a large piston and bore, with the thrust bearing on the piston to run on the clutch pressure plate.