Debate: clutch or clutchless system?
TimK
It's good to see all the new folks joining the group. I'd like to get
your input on one of the design details I've been pondering: using a
clutch or clutchless system for shifting.
Has anyone used a clutch-less system in their Civic conversion? for
those of you who are not familiar, a clutchless system eliminates the
flywheel weight and connects the motor driveshaft directly to the
transmission. The theory is that rotational mass of the motor's rotor
is so small that the synchromesh of the transmission can allow the
driver to shift gears (albeit a bit more slowly) without needing a
clutch. Electro-Auto typically uses a clutch-based system whereas the
EV-america folks provide adapter with a clutch-less system. Here's
some thoughts:
Clutched system for Civic:
- feels more like the original manual transmission
- heavy flywheel slows acceleration as the motor needs to overcome its
inertia
- ***clutch slave cylinder interferes with the placement of front
batteries****
Clutch-less system for Civic:
- much less mass to spin up during acceleration
- shifting is a bit slower as the driver uses the synchromesh to spin
the motor down
- shifting can only happen while the accelerator is not pressed
- ****no clutch slave cylinder to interfere with the batteries in the
front rack ****
- this system still uses the springed center of the clutch disk to
remove stresses on
the drivetrain from bumps in the road or looseness in the gears
The big reason I bring this up is that the clutch slave cylinder
interferes with placement
of the batteries in the front battery rack. I would prefer not to cut
any support members
on the car that I don't have to. This also removes all the clutch
hydraulics as well.
Some EV folks with clutch-less systems tie an electrical switch to the
existing clutch pedal
so that the main contactor shuts off when the driver presses the
clutch pedal, offering
a safety mechanism in case the main DC controller shorts open.
Does anyone know if removing the clutch slave cylinder will allow a
front battery rack to
exist without cutting any sheet metal (or at least significantly
reducing it)?
Thoughts and suggestions are welcome. I look forward to your
feedback.
Cheers,
Tim
Rob Connelly
I can definitely contribute to this discussion. I debated the issue quite a
bit myself when I was planning my conversion, and I agree completely with
your list of pros and cons. I decided to go with a clutchless system after
a couple of people who are clutchless told me that they don't miss it. I
was a bit incredulous about it, but I must say that after driving my
converted '95 Civic Coupe only 20 miles so far I don't miss the clutch! It
really does pull out of gear easily and go into the next one using just the
synchros to match shaft speeds. Correct, you can't shift with power
applied, but you better not do that with a clutch and an electric motor
either.
I removed ALL the clutch components -- no pedal, no hydraulics, no flywheel.
EV America made my coupler for me, and they used the old clutch disk as you
describe. It went together fine, and it is very little rotational mass.
The transmission does not have the boot covering the throwout bushing arm
any more, and the casting is flat at that spot, to give you an idea of how
much space you can save.
My installation retained the A/C, and only has 12 Optima 31 batteries, so I
only have one battery in the front rack, and it is right there where the
radiator used to be. Attached is a photo under the hood, without a cover
over the controller ends.
Let me know if you need more info.
- Rob
Chris Brune
My car is a del Sol, similar to the Civic, that uses the EV America kit, so it is clutch-less. And you are correct the slave clutch cylinder probably gets in the way of the battery rack that is currently above the motor and transmission.
Most of the time not having a clutch is OK. If I could I would rather have a clutch though. You can't get through the gears quickly. I'd say the shift delay is seconds in my car (~2-3). Not good for drag racing.
Regards,
Chris Brune
Hi All,
Cheers,
Tim
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TimK
Thanks for your comments about clutch-less design. I tried
shifting my 914 EV (that has a flywheel) without a clutch and got
similar results to Chris (waiting 3-4 seconds). Fortunately, I have
regen braking on the AC motor, so I was able to tap the brake to
quickly slow down the motor and get the transmission into the next
higher gear in less than a second.
I'm wondering if we could add a small circuit to the motor
terminals (say a few large FETs and a power resistor bank or heater
coil) to dissipate the kinetic energy in the motor at the press of a
button on the shifter knob. This would allow much faster shifting up
in gears without the clutch. When shifting down, I guess one could
just rev the electric motor with the accelerator pedal, provided there
was a rev-limiter to prevent burning out the motor. With the ability
to speed the motor up and down under driver control, shifting might be
more tolerable in a clutch-less system.
Cheers,
Tim
TimK
Would you please describe the coupler from EV America a bit more
and how it works with the original clutch disk? Did EV America attach
the clutch disk to a motor shaft adapter and then use a lathe to
remove all excess material? I've seen pictures, where they make an
aluminum rim that simply clamps around the original clutch disk so
that you can replace the clutch disk if necessary. If you could post
a picture of what the coupler looks like, that would be great.
Thanks!
Cheers,
Tim
Rob Connelly
Sure thing. I have a picture showing some of the assembly -- see it
attached here. What they made was a coupler that mounts to the motor shaft
and accepts the remains of the clutch disk. See the machined aluminum disk
in the photo -- that is the coupler, and EV America machined and tapped the
8 holes around its circumference. They took the clutch disk, and liberated
the friction surfaces from the central hub and springs by drilling out the
rivets that were in those 8 locations. Bolting it in place on the coupler
then leaves you with a direct coupling to the motor, but with the torsion
springs from the original clutch disk.
The other part of their package is the large aluminum adapter plate. They
machine the opening to fit the collar on the motor and drill holes to mount
it to the motor. They leave it up to you to machine the holes and mount it
to the transmission, and machine the perimeter of the plate to match the
bell housing.
I hope that helps. Perhaps Chris has more/better photos.
- Rob
----- Original Message -----
From: "TimK" <tim_k...@yahoo.com>
To: "Civic EV Kit" <civic-...@googlegroups.com>
Chris Brune
I think Rob's email gets it right on. I didn't do the conversion of my car, but I do have lots of pics.
I have attached one that shows the remains for the clutch disk attached to the adapter disk.
I was told that there was some sort of alignment tool that was needed, but I haven't figured out what it was and why it was needed.
I have been experiencing some vibration that seems to come and go, I've wondered if it has something to do with the adapter, but I don't know.
Regards,
Chris Brune
Tim,
____________________________________________________________________________________
KazooPaul
driving it seems clutchless is the way to go. The disadvantage of
slightly slower shifts doesn't come close to balancing the weight and
space savings (for this particular small, light EV). The more
relevant disadvantage for me might be some added difficulty in getting
my wife to use the car, ie., the more different it is to operate, the
tougher it might be to get the non-enthusiast to actually use it when
they have a choice.
Ian
something that is as usable as possible. Having to teach people how
to shift without the clutch adds one more hurdle to overcome.
What about using a lightened or an aluminum flywheel to reduce the
rotating mass? Depending on the power of the motor a smaller clutch
might also be possible.
Ian
Rob C.
miles on my Civic (clutchless) now, and I am second-guessing my
decision to do away with the clutch. As you may recall, I retained
the A/C with my installation, and until my latest test drive I hadn't
used it much other than to see that it works. Well, I drove a whole
trip with it the other day, and the compressor's power demands make
shifting without a clutch more troublesome. If the compressor is
demanding power, then when you pull it out of gear the motor quickly
comes to a stop, and it makes the synchros really work to bring the
motor (and compressor) up to the proper speed to engage the next
gear. I found that I had to blip the throttle a tad if I needed to
upshift while the compressor was on.
Secondly, I definitely agree that it would be a challenge for someone
new to the vehicle to be comfortable with the lack of a clutch.
If the extra rotating mass of the flywheel takes more energy then
perhaps the better solution is to put more energy into the size of the
battery pack rather than remove the clutch. Tim, I saw your post
about the Dekas -- maybe their extra oomph (and lower cost) are just
the ticket.
- Rob
TimK
Thanks to all for their input. Although I was tending towards a
clutch-less system at the start, I'm tending towards a clutched
system now. One of the big reasons I wanted to go clutchless
in the beginning was because of the battery interference with the
clutch slave cylinder. If we go with the Deka 9A31 AGM batteries,
they are slightly thinner (6.75") and that seems to fit in the 7.5"
that I measured between the vertical hood latch support and the
clutch slave cylinder.
So, reviewing the differences again:
Clutched system for Civic:
- feels more like the original manual transmission, allows people
unfamiliar with EVs to drive it more easily; downshifting much
easier
- Allows troubleshooting of the drivetrain by allowing an intermediate
disconnect point during operation
- Adds a safety feature if the controller shorts and over-revs the
motor
- inertia from heavy flywheel slows acceleration
- clutch slave cylinder interferes with placement of front golf cart
batteries
but not Deka 9A31s
Clutch-less system for Civic:
- much less mass to spin up during acceleration
- shifting is a bit slower as the driver uses the synchromesh to spin
remove stresses on the drivetrain from bumps
took significant inertial mass off the flywheel. I'd be a bit leery
of
taking off too much more since the electric motor has quite a bit
more torque, especially from a dead stop. I've heard several
people in the local EV club say that they hurt their transmission
(not necessarily the clutch) due to execessive torque from the
motor.
Given the thinner 9A31 AGM batteries, I'm tending toward a
clutched system at this point with the starter teeth on the clutch
machined off.
For the clutch-less systems from EV-America, it's my understanding
that you have to machine down your own faceplate to the transmission.
The motor adapters from Electro Auto for the Civic actually come with
the transmission plate pre-drilled so you don't have to spend the time
and money to machine your own transmission plate.
I actually ordered a Civic motor adapter from EA this morning, but
they
insisted I send a pencil scraping of the flywheel bolt holes so that
they
didn't give me the wrong motor shaft coupling. Apparently, they've
had
issues in the past with giving people the wrong bolt hole dimensions.
Alas, I don't yet have a flywheel for the conversion so I'll probably
have
to get one after I return from Italy.
Any other feedback regarding clutched versus clutch-less?
Cheers,
Tim
Hondacrzy
I do not have any personal experience yet,but I did order the clutch
design through EA. My thinking on the whole project is to make the car
as easy to drive as possible. This way if everything goes well with
the design, there won't be any thing to scare away the people sitting
on the fence waiting to jump into this whole idea of EV's
Thanks Chris