Working car clutch

[Tamas Juhasz]

Hello!

For a big projekt I needed a clucth without friction and relative high torque transmission, so I made this:

folder: http://www.brickshel...ry.cgi?f=532696

( http://en.wikipedia.org/wiki/Clutch )

My goal was a non friction clutch, without tension in the input and output axles, which can transmit one XL motors torque.

The most important thing in a clutch is the continuous transmission of torque from 0 -to max, and the separation of the two friction discs. This is what it can do, like the real clutches. In my moc, two 30,4x14 gokart wheel transmit the torque (max. ~40 Ncm) only with friction.

Yes, the rubber tires have friction and abrasion (after a time a new tire is recommended), but without friction between the discs it's not clutch.

In this clutch there is a minimal friction only during the separation of the friction discs. I separated the two types of forces: which pushes the two tires, and those ones, which makes friction (like in every technic mechanism, because of no bearings) in the axles. So the big force (for a big torque transmission) is between the two turntable bottom part, and this pushing force doesn't make tension and harmful friction in the input and output axles.

Displacement range:

This is 1-2 mm, but after the separation, you need no more. It has precise gaps between the rotating parts, so when it's closed, it works like a long axle, without plus friction. When it's released, it has again non friction in the axles, because the two friction discs can rotate free in the turntable discs: http://www.brickshel...y.cgi?i=5922650

Size: I built a big holding frame for the pictures, so it can be built smaller, but of course it's for big models and requires relatively lot of space. I think it's better when we have a big working clutch than a small one which is a torque limiter, or something non-clucth like mechanism. It's all about working, If you think it's big, just see these: http://www.brickshel...y.cgi?i=5054271 ; http://www.brickshel...y.cgi?i=4439709 ; http://www.brickshel...y.cgi?i=2478965 - these can be used in big models. I need this clutch for a very big truck, I built in, works fine. For me, efficiency is very important, that's why I needed a "non-friction" cutch. Technic is all about compromise:

in this case bigger size for less friction.

I made a video for better understanding:

Hope you like it.

Edited August 12, 2013 by Mbmc

[Doc_Brown]

Thanks for making that video and sharing.

Great showing how it works! It looks really strong and seems to handle a good amount of torque.

Great job.

[JF8]

That's pretty cool, also is that part of a wind up motor I see?

[EyesOnly]

That looks like one powerful clutch. Can't wait to see what model you put it in.

[camaudio]

Would a servo have enough force to disengage the clutch?

[Tamas Juhasz]

Thank you!

That's pretty cool, also is that part of a wind up motor I see?

Yes, that white part is a "spline shaft" from a wind up motor: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=505117 - it's smaller and simplier than the "pulley-3Lstopaxle" construction. I could do the building with it also faster.

Would a servo have enough force to disengage the clutch?

Very good question, it's important. The servo has enough force to do it (not with empty battery). This clutch can work "proportionally" with the PF servo motor. I use it before and after the gear change, it works fine. That truck is a wip project which contains this clutch, after a few weeks maybe I will publicize it.

[aol000xw]

Recently I tried something similar with those exact tyres, a double clutch indeed, completely isolating the gearbox. But failed at it as my design caused friction and so load on the motor. Your approach is very elegant, love it.

Correct me if I am wrong, but for a totally smooth gear change isn't a dual system needed with one clutch at the input and another at the output of the gearbox, both working together?

I am thinking more on the line of a fast car than a crawler. with a couple RC motors,

if you disengage the wheels, but the motors aren´t completely stopped the gearbox isn't safe. If is the motor what you disengage, the speed of the car can tear apart the gearbox.

Obviously I am thinking of changing gears with the vehicle at speed preferibly without stopping the motors in the process.

[Bart]

You don't disengage the gearbox from the wheels, you need the rotations of the gears to make a smooth change, or that is how I understood it.

I mean your car doesn't have a clutch there either, you only take the power (engine) of.

I do like your clutch design, very clever how its not making any friction when disengaged.

bart

[Tamas Juhasz]

Thanks!

Correct me if I am wrong, but for a totally smooth gear change isn't a dual system needed with one clutch at the input and another at the output of the gearbox, both working together?

Obviously I am thinking of changing gears with the vehicle at speed preferibly without stopping the motors in the process.

Bart has right, it doesn't need a second clutch after the gearbox, if it would be needed, real cars also would have it.

The reason is in the rpm and load: the clutch synchronises the rpm of the motor and the rpm of the axle connected to the gearbox. With another words: the motor makes tension and load to the axles and gears in the gearbox, so first we synchronise the gear (first, second,..) and it's axle with the gearbox (without load). Then the clutch synchronises it with the engine's rpm (in technic also, but simplier). The reason is why clutch is needed in real cars is that the rpm synchronisation would be too quickly without clutch, the mechanisms aren't for that big load, even it takes a very short time. When the rear (or another) driven wheel drives back the gearbox, after the gearbox there is nothing, so there is no load (because the clutch is disengaged). Load causes scratching and similars (without load the synchronisation is done nearly immediately). In Technic, when we shift gear without clutch, there is an electric motor, which drives the gearbox, AND the load, the driven wheel which is connected with the road. So in this case there is load after the gearbox, that's why we can hear scratching.

Edited August 13, 2013 by Mbmc

[aol000xw]

Im planning a fast MOC with 2 RC motors and 10v LiPo modified battery packs, not a crawler type, That is a lot of power and speed -i hope- and even if the gears are synchronized the gear selectors are vulnerable.

If wheel speed is high enougth you might not be able to make the switch movement fast enougth to avoid damage to the gear selectors.

Well that's what I think, and why I asked about the double clutch; of course perhaps I am a bit optimistic about the achievable speeds... or I am missing some trivial fact. I did not specify that my concern where on the selectors and not the gears itself..

Anyways most clutchs out there can't achieve what his design does so in that regard is awesome, and my concerns are more in the line on how to apply correctly his system to my crazy projects.

Edited August 13, 2013 by aol000xw

[piterx]

Thats great man! Well done