# [EVDL] Clutch vs Clutchless - Two Cents



## EVDL List (Jul 27, 2007)

Clutch vs clutchless is just one of the many decisions any EV converter 
will have to make. Here's my two cents.


The principle advantages of clutchless are:

1. The motor and transmission can be closer in distance. The flywheel and 
pressure plate push the motor further away from the transmission. Now 
most of the weight (flywheel and pressure plate) is further down the shaft. 
They may actually overhang the motor shaft. This puts more stress on the 
shaft and bearings. 

2. The coupling, hub, and clutch disk (~5 lbs) weigh only a fraction of 
the weight of the pressure plate and flywheel (~25-40 lbs). Our design uses 
the clutch disk, the springs absorb the initial shock. Without the 
springs, the splines on an S10 disk may wear out in about 7000 miles, but that 
may be also due to softer grade material used. 

3. Many people do not know how to drive with a clutch. With the 
clutchless, they simply take their foot off the accelerator and shift. Without the 
flywheel and pressure plate, there is minimal inertia; easier to shift. 
We tell people to sit in their car without the engine running. Now shift 
gears. That is what it is like.

4. The clutchless is simpler to machine and less costly. It can be more 
generic.

5. The clutchless design does not require the flywheel and pressure plate, 
so there is nothing to balance at high speed.

6. The clutchless may be more efficient due to less inertia. No data, but 
it appears that clutchless EVs do get better range. Bolton High School 
(CT) used our clutchless design and 20 -6V batteries and did 165 miles on a 
charge in the American Tour de Sol race. Two years in a row! 


The disadvantages of clutchless are:

1. Slightly longer to shift, so drag racing is out. 

2. Downshifting from 3rd to 2nd gear, or 2nd gear to 1st gear is more 
difficult at certain speeds.

3. The motor cannot be isolated from the drive train. If you destroy a 
motor by overreving, most likely you will come to a screeching stop. 
Depressing the clutch may help you coast, if you recognize the mode of failure in 
time.


Hope this helps those trying to make a decision. During our 23 years, we 
have provided clutch and clutchless designs. The problems associated with 
clutchless have been minimal in comparison to the clutch design. 

Bob Batson 
603-569-2100
_www.EVAmerica.com_ (http://www.ev-america.com/) 
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## EVDL List (Jul 27, 2007)

> [email protected] wrote:
> 
> > Clutch vs clutchless is just one of the many decisions any EV
> > converter
> ...


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## EVDL List (Jul 27, 2007)

I'm hoping to make my EV (now with a clutch + flywheel) clutchless and go
lithium at the same time. With the reduced weight I can have a simpler
design and as a normal course shift less ... use 2nd most of the time, and
3rd only after I crest a hill. I won't need 1st unless I'm climbing slowly
with 4 adults in the car. I have driven clutchless designs too, and without
the flywheel, the motor slows down more quickly to shift, so it's hard to
compare an ICE or EV w/clutch with a clutchless design. My experience is
that it's not that bad. 

Another benefit for me is that I have a lot of noise/vibration with my
flywheel right now (and some reduction in efficiency), so without it It'll
get quieter.

And, though I understand the safety concern on a runaway controller - it is
easier/faster to push the clutch in than other manuevers. But, I would
think, though perhaps not the best thing for your transmission (it IS an
emergency / low probability event afterall), you can yank it out of gear
without a clutch. Or, use your brakes. Most EV motors wouldn't be able to
overpower braking before you hit your disconnect or turn off the key ...

Dan

-----
Dan Gallagher
http://www.evalbum.com/3854

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## EVDL List (Jul 27, 2007)

The clutch vs. clutchless debate always incites lots of arguments. I've 
driven both, and there advantages and disadvantage to both methods. Many 
of them have been covered in these posts. Here's my two cents.

If the car had a clutch and flywheel, it's easiest and most 
straightforward to keep it. It will also make driving the car more normal.

To do it right, the flywheel *has* to be well balanced, and the coupler 
*has* to be very strong and rigid. The forces generated by an out of 
balance flywheel will cause vibration, can wreck the motor bearings and 
seals, and in extreme cases even causes dangerously destructive 
failures. If you are getting vibration, fix it!

I don't think a simple keyway and setscrew is adequate for anything 
except light-duty or quick-n-dirty conversions. It isn't strong enough 
to handle the weight and forces of a heavy flywheel and clutch. I prefer 
a taper-lock of similar high-strength coupling methods.

The coupler is simpler without a clutch and flywheel, but you need a 
stronger, better transmission. Some stock transmissions are good enough; 
others aren't. Shifting clutchess is much harder on the transmission's 
synchronizers and gears. If your transmission is known for problems with 
these parts, going clutchless is likely to cause failures.

On eliminating the springs in the clutch disk: You need *something* in 
the drive train between the wheels and motor to absorb sudden speed 
differences. There is backlash in the gears, universal joints, and other 
drive train parts. Jack up a wheel, and rock it back and forth; you'll 
feel this "play". It rotates a small amount, then stops with a sudden 
"jerk".

Potholes, an uneven road, or just minor ripple in motor current will 
make the drive train "bounce" back and forth between the limits of this 
backlash. Without springs or rubber or anything to soften the force, the 
peak force on the gears, splines, universal joints, etc. is quite high 
and can cause faster wear. You can feel this when driving as the car 
"bounces" rapidly ahead/back.

A clutch provides a way to disconnect the motor in case of a failed 
controller. Without a clutch, it is difficult or impossible to pull a 
manual transmission out of gear under full power. However, you should 
already have other, better ways to cut power so that such a precaution 
isn't necessary.

Don't expect that you can stop a series DC motor with the brakes. As 
their speed approaches zero, their torque approaches infinity! The real 
torque can be many times more than any ICE would have delivered.

-- 
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377	| There is a crack in everything
leeahart earthlink.net	| That's how the light gets in -- Leonard Cohen

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## EVDL List (Jul 27, 2007)

> On 13 Dec 2011 at 7:42, Danpatgal wrote:
> 
> > Most EV motors wouldn't be able to overpower braking
> > before you hit your disconnect or turn off the key ...
> ...


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## EVDL List (Jul 27, 2007)

Maybe the exception that proves the rule: I drove a 65 Ford Mustang with a =
3 speed manual (ICE). You could shift up and down without the clutch as eas=
ily with, no rev matching needed. I also drove an electric VW bug clutchles=
s, and it was easy to up and down shift without rev matching.

I have many more examples the other way, though. My electric Porsche is ver=
y difficult to shift unless you use the clutch. Even with rev matching, Cam=
aro, Jeep, Fiesta, 2nd Jeep, and others were rather difficult to shift with=
out the clutch.

It appears the difficulty can vary significantly between models of cars.

BTW, the pilot bearing galled on my Camaro (kind of like what a clutchless =
adapter does 100%, locks the tranny shaft to the motor shaft). It was very =
fussy about getting into 1st gear, even when stopped with the clutch in. Wi=
th a new pilot bearing it slips in like butter (including accidentally shif=
ting from 4th to 1st on the racetrack once!).

My 2 cents is keep the clutch!



________________________________
From: Martin WINLOW <[email protected]>
To: Electric Vehicle Discussion List <[email protected]> =

Sent: Tuesday, December 13, 2011 2:30 AM
Subject: Re: [EVDL] Clutch vs Clutchless - Two Cents
... As for "simply take their foot off the accelerator and shift...". I=
am sorry but no car I have ever driven works like this unless you want to =
destroy the synchromesh in very short order. There is ALWAYS some degree - =
and often A LOT - of rev matching required by using the throttle to get the=
synchromesh sufficiently aligned to allow changes in gear. Perhaps US manu=
al boxes are different to Japanese and European ones. I have never drive=
n one. ...
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## EVDL List (Jul 27, 2007)

I'll add some data, I'm running clutchless with an AC system. Since regen
slows the motor very quickly when shifting you must time the shift very well
and shift very fast. This allows faster shifting than with a clutch but
also means you'll be grinding gears if you don't get it right. Down
shifting is rather difficult. On the other hand with the flat torque curve
and higher RPM's of an AC motor you probably won't need to shift, I just use
2nd gear for almost all driving from 0-65 mph, 7500RPM peak. This is with
an HPEVS AC31 motor and Curtis 1238-7501 in a Fiero.

EVDL Administrator wrote
> 
> 
> Alternatively, you could go with an AC motor, which is inherently unlikely 
> to fail full on.
> 
> David Roden - Akron, Ohio, USA
> EVDL Administrator
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