# Electric clutch?



## samborambo (Aug 27, 2008)

Excellent idea. Should work if you can find a suitable solenoid to pull in the clutch lever on the tranny. Use a dynomometer or torque wrench to work out the force required.

Sam.


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## Woodsmith (Jun 5, 2008)

I was wondering what to use but that's a good idea.

It will get rid of the hydraulic clutch cylinders and the potential for leaks too.


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## Woodsmith (Jun 5, 2008)

How's this for a further thought.

I could use a pnumatic actuator on the clutch lever. The compressed air could come from the same compressor that supplies the vacuum for the brake servo. One side of the compressor sucks a vacuum, the other side blows compressed air into a small pressure tank.

It will take a bit of fancy plumbing and pressure/vacuum switch control.


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## Jimdear2 (Oct 12, 2008)

Woodsmith said:


> How's this for a further thought.
> 
> I could use a pnumatic actuator on the clutch lever. The compressed air could come from the same compressor that supplies the vacuum for the brake servo. One side of the compressor sucks a vacuum, the other side blows compressed air into a small pressure tank.
> 
> It will take a bit of fancy plumbing and pressure/vacuum switch control.


Look at the VW and Porsche auto sticks for ideas and components. 

That was a completly vacuum operated system. It used a big diaphram, a big vacuum tank and a engagement control valve to operate the clutch. You could use some if not all of the components. The control valve could be adjusted to allow fast or slow clutch engagement.


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## PhantomPholly (Aug 20, 2008)

Warner carries some interesting electric clutches, but don't know if they have any large enough to carry the full load of an EV motor.


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## Woodsmith (Jun 5, 2008)

That would be neat, small and compact and no need for a heavy flywheel. I guess those are just heavier duty versions of the aircon compressor clutch pulley?
I shall look in to that further but I reckon they won't be that cheap.

I also looked into the auto stick shift vacuum clutch but couldn't find any easy access parts for one so stuff will need to be made up one way or another.

This could lead to an interesting coupling option for converters and parts suppliers.

Just remember, it was my idea!


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## PhantomPholly (Aug 20, 2008)

Woodsmith said:


> That would be neat, small and compact and no need for a heavy flywheel. I guess those are just heavier duty versions of the aircon compressor clutch pulley?
> I shall look in to that further but I reckon they won't be that cheap.
> 
> I also looked into the auto stick shift vacuum clutch but couldn't find any easy access parts for one so stuff will need to be made up one way or another.
> ...


Yes, I've been looking at these for a while as a way to mount a supercharger on my flying toy. Superchargers draw approximately 1/4 of the additional horsepower they allow you to create - thus, if it allows your motor to generate an additional 50 hp, 12.5hp of that is "robbed" by the supercharger.

The pictured model is purportedly for superchargers, so I presume they have models which will handle at least 10hp continuously. I don't know what larger models they might make, but my supposition is that they are not $ thousands.


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## Woodsmith (Jun 5, 2008)

I had a look at a few manufacturers products and it is possible to have ones that handle high torque or high speed but is seems to be inversely proportional. Higher speed, lots less torque.

It will take a bit of shopping around to find one that suits. I will get the motor first though so I know what the capacity needs to be.

Maybe one day EV motors for conversions will have one built into the end cover so the output shaft is clutch controlled and with a female spline to fit the gearbox shaft.


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## Drew (Jul 26, 2009)

There are some semi automatic systems around which depend on detecting the initial movement of the gear lever to activate a clutch solenoid for ICEs, I can't remember what make of car they were for (saabs maybe?), but the initial travel of the shift lever basically absorbs the slack in the linkages so you could just detect that movement to pop the clutch. The same mechanism could zero your throttle input to the motor controller with some sort of small relay or something as well.


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## Woodsmith (Jun 5, 2008)

Drew said:


> There are some semi automatic systems around which depend on detecting the initial movement of the gear lever to activate a clutch solenoid for ICEs, I can't remember what make of car they were for (saabs maybe?), but the initial travel of the shift lever basically absorbs the slack in the linkages so you could just detect that movement to pop the clutch. The same mechanism could zero your throttle input to the motor controller with some sort of small relay or something as well.


Yes, I've heard of that but also can't remember where and on what vehicles.

I started thinking of this yesterday when I had the gear stick boot off the tunnel in the MR2 and saw the two rods that moved with the gear stick.
The fore aft rod could have a couple of blocks clamped to it to actuate a micro switch to detect the slack.
That should work.


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## Drew (Jul 26, 2009)

I had a bit of a look around and it was the Saab Sensonic Gearbox, apparently it was only ever produced for 2 years before they pulled the plug on it.

I think that picking the for after selector and putting some sort of microswitch system on it would be a good idea, it might be easier to implement on the gearbox casing though, as you'll have a lot more structure and bolt holes to borrow down there and if you mount to the case then the parts won't flex or move relative to each other.


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## Woodsmith (Jun 5, 2008)

Could this work?

Using an old Lockhead type overdrive for its cone clutch and doing away with the gears.

I have thought about ripping one apart and using the cone clutch and hydraulics to make a hydraulic 'on/off' clutch to replace the flywheel clutch assembly. The unit would need to be run backwards so that the spinning gearbox shaft supplies the internal hydraulic pump drive. That way it can only disconnect drive for a gear change when the vehicle is in motion. The electric valve could then be controlled by movement in the gear stick in advance of a gear change.

When there is no action and the shafts are spinning or not the unit is locked in direct drive via the cone clutch. Fine for moving off and driving.
When a gear change is made, movement of the gear stick operates the electric valve and hydraulic pressure disengages the clutch to the overdrive position, except there are no gears so no drive so it is effectively disconnected. That allows a smooth gear slection to be made.
At the end of the change the electric valve is closed and direct drive is back on.


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## dreamer (Feb 28, 2009)

Woodsmith said:


> Could this work?
> 
> Using an old Lockhead type overdrive for its cone clutch and doing away with the gears.
> 
> ...


I would think the key to a smooth gearshift requires correct speed control of the motor. You know the gear ratio for the gear you are moving into, and you know the tire circumference and the current vehicle speed. A simple calc in the motor controller could adjust the motor RPM to exactly match what is needed for the current MPH. Wouldn't this lead to incredibly smooth shifts ? Simply disconnecting the throttle control while the clutch is operated would lead to jerky shifts. You want the motor turning at exactly the right RPM in anticipation of the new gear selection.


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## Woodsmith (Jun 5, 2008)

dreamer said:


> I would think the key to a smooth gearshift requires correct speed control of the motor. You know the gear ratio for the gear you are moving into, and you know the tire circumference and the current vehicle speed. A simple calc in the motor controller could adjust the motor RPM to exactly match what is needed for the current MPH. Wouldn't this lead to incredibly smooth shifts ? Simply disconnecting the throttle control while the clutch is operated would lead to jerky shifts. You want the motor turning at exactly the right RPM in anticipation of the new gear selection.


But having the motor running off load would be a risk of over speeding the motor if something else wasn't quite right. Besides, there shouldn't be enough rotating mass to make the chage jerky.

I can do clutchless changes in and ICE car by managing the engine revs but I wouldn't risk it in an EV especially as the motor speed would depend on the road speed at the time of the gear change.


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## SimonRafferty (Apr 13, 2009)

A nice simple (read cheap) solution would be to keep the regular clutch then use either a windscreen wiper or electric window motor to operate the clutch directly. 

Si


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## Woodsmith (Jun 5, 2008)

SimonRafferty said:


> A nice simple (read cheap) solution would be to keep the regular clutch then use either a windscreen wiper or electric window motor to operate the clutch directly.
> 
> Si


Do you mean attach the wiper motor crank to the clutch release arm and make it run half a turn to pull the arm and then half a turn to release the arm?

I should have tried that while the engine and box were still together to see how much force would be needed and if the motor would do it.
I still could, I guess, if I refit the clutch and flywheel to the box and then fix the flywheel from moving.


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## Drew (Jul 26, 2009)

If you cut an actuation cam or design a linkage appropriately you can just have fast disengage slow re-engage for the clutch, I've seen it done with pneumatic control for race cars, where the air bleed out of the cylinder controls the rate of re-engagement.


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## Stunt Driver (May 14, 2009)

I like the idea of doing electric clutch alot (especially since my clutch doesn't dully disingage due to bigger movement of cylinder needed) but there is A LOT of force required to push that lever. No windshild wiper comes even close.

Need some mighty solenoid.


AC-like clutch is a neat idea, just need to find proper one - probably from lawnmover tractor? Those are used with 20HP engines.
This looks good - http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150368414748&_trksid=p2759.l1259

And biggest question - how often would it need to be repaired? Those clutches are around since 80s, so there has to be a reason why they aren't used in EV.


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## Woodsmith (Jun 5, 2008)

The lawn tractor one looks good. It would need to be tested to see if it would really cope with the torque required to move a car though. The manufacturers specs seems to reduce capacity as speed increases to EV type RPM.

It would be a pain to fit one and then find it doesn't work.

I am tempted with using either vacuum or air pressure to operate the clutch. I have been looking at the air brake actuators used on heavy trucks. They can work either with air to pull, spring to push or air to push, spring to pull. They also have a long enough stroke to work with. The compressor and reserviour don't need to be big as the clutch won't operate very often. The sort of thing used with air springs would do.

I would still like to have one compressor doing two jobs, sucking a vacuum in one reserviour for the brakes and pumping it into another for the air clutch.


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## SimonRafferty (Apr 13, 2009)

Stunt Driver said:


> I like the idea of doing electric clutch alot (especially since my clutch doesn't dully disingage due to bigger movement of cylinder needed) but there is A LOT of force required to push that lever. No windshild wiper comes even close.


Have you tried it? I have. The force required varies significantly from one clutch to another. Even if yours is uber-heavy, it is not universally true.

Also, you can balance the clutch with another spring to reduce the force required to depress it. Because the motor can pull as well as push, this does not lessen the pressure between the clutch plates.

A clutch rated at 20hp will probably not be up to the job. Remember that (ignoring units) the power is the torque multiplied by the rpm - so 20hp could mean infinite torque at zero rpm or zero torque at infinite rpm.

The 20Hp is only meaningful if the torque curve of your motor is similar to the engine that normally drove the clutch. Be careful before you spend loads of cash on it!

Si


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## Stunt Driver (May 14, 2009)

I think i'll manufacture my parts to have normal clutch installed, but later will try to install electric clutch in a way so it can be removed and replaced with normal clutch if broken.

As for 20HP - my EV is going to be very conservative in power and low in cost , so I don't expect huge amounts of torque at any RPM. 

As for lever force - sure I have tried. I can hardly move it at all with hand - on my Fiero. There are probably other smaller cars, that require less pressure, but still I would be extremely surprised if wiper would be enough. 
And spring support even thou theoretically possible - adds another huge point of failure, I will not try this.


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## Woodsmith (Jun 5, 2008)

I tried this earlier this evening and I couldn't push the clutch lever by hand.
I then tried with a big adjustable spanner on the end of the lever to expend it. It moved but then the end of the clutch lever snapped off right in the centre of the push rod dimple.

It will need a lot of leverage to move it.


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## kixGas (May 2, 2008)

something to look into is that manual transmission out of an '02-'03 MR2 Spyder. They had an option called SMt (sequential manual transmission) which essentially was a true manual transmission without a clutch pedal. I don't know if they used a sleek hydraulic system to activate the clutch plate or if it was electric but it might be something to look at.


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## SimonRafferty (Apr 13, 2009)

Woodsmith said:


> I tried this earlier this evening and I couldn't push the clutch lever by hand.


Fair enough. A few years ago, I was asked to help with a push button clutch for a chap who had lost the use of his left leg - but still wanted to drive his manual. The clutch was cable operated and required about 500N IIRC force on the cable to disengage the clutch. We used a window winder from a Range Rover with a capstan to pull the cable - worked pretty well. The gear ratio on windscreen wiper motors is similar - but the motors are generally much bigger - and many use a cable to operate the wipers.

Land Rover Defender 300Tdi's use a balance spring on the clutch to make it a little lighter for less butch drivers - I've never heard of one failing so "adds another huge point of failure" may be over-stating it.

Si


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## samborambo (Aug 27, 2008)

SimonRafferty said:


> Fair enough. A few years ago, I was asked to help with a push button clutch for a chap who had lost the use of his left leg - but still wanted to drive his manual. The clutch was cable operated and required about 500N IIRC force on the cable to disengage the clutch. We used a window winder from a Range Rover with a capstan to pull the cable - worked pretty well. The gear ratio on windscreen wiper motors is similar - but the motors are generally much bigger - and many use a cable to operate the wipers.
> 
> Land Rover Defender 300Tdi's use a balance spring on the clutch to make it a little lighter for less butch drivers - I've never heard of one failing so "adds another huge point of failure" may be over-stating it.
> 
> Si


I suppose it comes down to how fast you want the clutch to fully disengage. It may be 500N of force but how far was the travel? If it travelled 100mm to disengage then the work (energy) done is 50 Joules. If you want that work done in, say, 0.5sec then the motor only needs to be 100W and geared appropriately.

Sam.


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## samborambo (Aug 27, 2008)

A starter motor would probably do it with the cable spooling tight around the drive axle.


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## Jimdear2 (Oct 12, 2008)

I'll bring this up again.

In the late 60s and early 70s VW and Porsche designed, created and delivered the auto stick. This system used a electrically controlled vacuum diaphram to disengage and engage the clutch. This was a standard automotive clutch opertated by a lever just like you see today.

The reservoir, diaphram and control valve were stand alone parts that are still available in dismanteler yards and in some cases the aftermarket.

The heart of the system was the control valve. It was activated by a spring loaded contact in the shift lever and when the contact closed the valve would apply vacuum to the diaphram and disengage the clutch. When the contacts were opened the valve would slowly release the clutch. The speed of release was adjustible at the control valve.

This stuff is still available on eBay and elsewhere (I looked).

Instead of re inventing you should investigate what may be a turn key system.

Hope this helps.


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## Woodsmith (Jun 5, 2008)

I like the 'Heath Robinson' string and pulley method.

Really I was thinking about a quick action to work with a quick gear change. If it was too slow then I may as well go without a clutch and change gear slowly or keep the clutch and use my leg.

I have a variety of window winder and geared motors so I can see how much torque one would produce on a crank arm and con rod.


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## Woodsmith (Jun 5, 2008)

Jimdear2 said:


> I'll bring this up again.
> 
> In the late 60s and early 70s VW and Porsche designed, created and delivered the auto stick. This system used a electrically controlled vacuum diaphram to disengage and engage the clutch. This was a standard automotive clutch opertated by a lever just like you see today.
> 
> ...


I've looked into this and I can't find the parts here in the UK. I've though of using a brake servo to do this using vacuum and also using a truck air brake actuator using air pressure.
Vacuum would be best as I would have a vacuum pump and tank onboard anyway but I would consider adding a small compressor.


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## Stunt Driver (May 14, 2009)

as for vacuum - i just don't like idea of another conversion - electricity->vacuum->movement. And noise. I'll even try to go without brake booster if possible.


But let's get back to electric clutch

Keep in mind there is huge difference in EV application - both shafts are rotating whenever you'll want to shift, and so delta of speed is never huge. You can have 7kRPM motor, but unless you'll rev motor up the red line before engaging first geat at a complete stop (which is absurd on EV) - clutch will never see those RPMs.

Torque seems to be more important factor - hub must be able to pass momentum without slipping. That would be a true EV solution.


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## Drew (Jul 26, 2009)

Another alternative is a compressed air system, using a small diving cylinder would get you 1000's of clutch operations before the cylinder needed recharging and any dive shop should be able to refill air tanks for you. No secondary system needed. And if worst comes to worst and you run out of gas then you can skip the clutch altogether.


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## Woodsmith (Jun 5, 2008)

Compressed air would be the easy route.
Standard clutch, automotive actuators and cylinders from heavy trucks and I have a small and efficient compressor in my current car....

However, it does add weight.


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## Drew (Jul 26, 2009)

I'd recommend looking at paintball equipment, excellent, cheap and deals with extremely high pressures, which means small, light and compact. And a 500N cylinder would usually only weigh a few hundred g or so


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