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Discussion Starter #1
Hi all,

Hope you aren't tiring of my relentless noob questions.

My truck has a 4-speed manual with no clutch. This seems fairly common
on conversions from what I've seen, but I'm a bit confused on how to
drive it. When I shift from one gear to the next, it sounds like the
syncronizers are screaming pretty loud. This doesn't surprise me much,
and my natural inclination is to try to float the transmission, like I
was driving a big-rig or something. But this raises two problems. First,
I understand that revving the motor without a load (e.g. in nuetral)
like I would want to when downshifting is a big no-no. And second, when
upshifting there isn't any way to drop the motor rpm...you take it out
of gear and the motor keeps spinning rather than immediately falling off
like an ICE. I've successfully floated it upshifting a couple of times
by simply shifting into nuetral and waiting for the motor to spin down
to an appropriate speed on its own before shifting to the next
gear...but that takes a really long time.

So, what am I supposed to be doing? Is it OK to very gently rev the
motor to float downshift? Is there some way to slow the motor down while
it's coasting in nuetral? Should I not be trying to do this at all, and
it's just OK to shift with the motor off-speed? If someone could
enlighten me a bit about the proper driving technique for an electric
motor on a clutchless manual, I would really appreciate it.

Thanks

Hunter

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Discussion Starter #2
From: Hunter Cook
> Hope you aren't tiring of my relentless noob questions.

No. It's the nature of mailing lists like this that we answer the same questions over and over. It would be nice if people checked the archives first, but they don't...

> My truck has a 4-speed manual with no clutch... I'm a bit confused
> on how to drive it... syncronizers are screaming pretty loud...
> Is it OK to very gently rev the motor to float downshift?
> Is there some way to slow the motor down while it's coasting in
> nuetral?

Clutchless shifting depends a lot on the transmission. Some transmissions have weak synchronizers, and do it really poorly. Others have strong synchronizers, and shift so well that you can hardly tell that there's no clutch.

In my limited experience, the transmission in my 1974 Datsun worked badly clutchless. The 3-speed Borg Warner in my ComutaVan (from 1960's Studebakers) worked well, as does the 4-speed transaxle in my 1980 Renault LeCar EV.

The danger from revving the motor in neutral in an EV is that the motor speeds up VERY QUICKLY, and makes very little noise to warn you of how fast it's going. It's very easy to blow it up from over-revving. Here are a few ways to fix this:

- Add a tachometer, so you can see what you're doing.
- Add a RPM limiter, that senses high RPM and cuts or reduces power
to the motor to prevent it from going higher.
- Add something that limits the potbox resistance when in neutral,
so the controller can't provide enough voltage to over-rev.

Slowing the motor down faster when upshifting can also be done several ways:

- Use a controller that has regenerative braking.
- Drive some parasitic loads off the motor, like they do in ICEs.
(alternator, power steering, air conditioning compressor, vacuum
pump, etc.) You can arrange things to deliberately switch these
loads on when you shift into neutral and release the accelerator
pedal to brake the motor as fast as you like.


--
"Excellence does not require perfection." -- Henry James
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net

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Discussion Starter #3
If you are running a wide ratio transmission with straight cut gears, it is
about impossible to make down shifts. This is what my old transmission was,
which had a 1st gear ratio starting out at 3.5:1 and then drops to 2nd gear
at 2.0:1 which are the normal gearing for lite weight vehicles with small
engines.

My other transmission has a close ratio which is 2.2:1 1st gear, 1.6:1 2nd
gear, 1.3:1 3rd gear which had bevel gears. With this type of transmission
is connected to a engine, and you let up on the accelerator, you then shift
the gear lever to neutral, the engine because of its compression slows down
more than then the drive line, so you have to give it a little more gas to
bring the engine up to the same speed of the driveline and it will slip
right in.

With a electric motor, when you let up on the accelerator, a motor if not
driving a accessory will it is free wheeling or maintaining a higher speed
then the drive line. If I slip the transmission out of gear while my EV is
still moving, and coming to a stop, my motor may still be rotating. I
sometimes do this on purpose, so when I start apply power to the motor, my
motor may still be rotating which may decreases the starting motor ampere.
All I do is depress the clutch to perform this trick.

The problem here is with a motor and you slip the transmission to neutral,
the drive line is slowing down more than the motor. The only time I can
make the drive line go the same speed of the motor or even more, is when I
coasting down a hill. Sometimes a close ratio will work for down shifting.
Up shifting is no problem, because all you do is reduce the motor rpm to
match the drive line rpm which is normally higher because you was in a lower
gear and going up to a higher gear.

To solve this problem is that I am running a rotating inverter alternator
off the front of the pilot shaft of the motor, which slows the motor like a
compression of a engine, which I need when driving on very icy down hills.

I can turn off the regulator circuit to this alternator which turns off the
charging to a onboard battery if I want to gain speed on some down slope
hills, so I can roller coast the next one.

I am going to make a modification to this accessory drive system, where I
can select a AUTO mode, where If the the motor is under power from the
controller, the accessory drive is driven separate by accessory electric
drive motors. When the main motor is not under power, but the EV is still
moving, the main motor will then drive the accessory units.

Roland






----- Original Message -----
From: "Hunter Cook" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, October 21, 2007 10:47 AM
Subject: [EVDL] Clutchless transmission question


> Hi all,
>
> Hope you aren't tiring of my relentless noob questions.
>
> My truck has a 4-speed manual with no clutch. This seems fairly common
> on conversions from what I've seen, but I'm a bit confused on how to
> drive it. When I shift from one gear to the next, it sounds like the
> syncronizers are screaming pretty loud. This doesn't surprise me much,
> and my natural inclination is to try to float the transmission, like I
> was driving a big-rig or something. But this raises two problems. First,
> I understand that revving the motor without a load (e.g. in nuetral)
> like I would want to when downshifting is a big no-no. And second, when
> upshifting there isn't any way to drop the motor rpm...you take it out
> of gear and the motor keeps spinning rather than immediately falling off
> like an ICE. I've successfully floated it upshifting a couple of times
> by simply shifting into nuetral and waiting for the motor to spin down
> to an appropriate speed on its own before shifting to the next
> gear...but that takes a really long time.
>
> So, what am I supposed to be doing? Is it OK to very gently rev the
> motor to float downshift? Is there some way to slow the motor down while
> it's coasting in nuetral? Should I not be trying to do this at all, and
> it's just OK to shift with the motor off-speed? If someone could
> enlighten me a bit about the proper driving technique for an electric
> motor on a clutchless manual, I would really appreciate it.
>
> Thanks
>
> Hunter
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 
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