hard shifting

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hard shifting

Ben Jarrett
       

Hey guys,

So I put the clutch back in my jeep to make it easier to shift (especially downshift).

For the most part I'm happy to have the clutch back, except for one thing.  I start
my jeep in 2nd.  I shift to 3rd around 35 mph.  When I shift, I have to let
the clutch pedal out very carefully at about 2/3 of the way out.  If I don't,
I get a decent drivetrain jolt.  Nothing too terrible, just a bit harsh.  If I'm careful,
I usually do ok.  

I think the issue is that when I shift, the motor is around 4000 RPM.  Since I have a 22 lb
flywheel on the motor, when I shift, the motor doesn't slow down very much at all.  When I finish shifting,
the motor needs to be around 2500 RPM. So during my shift, the motor has to change quite a bit
of momentum.  My theory is that if I could lighten my flywheel (maybe go with aluminum), I could
"fix" this.

Has anyone else had this problem?  Are there other solutions (like some way to slow
down a dc motor)?

I don't have as much issue downshifting - my biggest problem is 2nd - 3rd shift.  3rd - 4th
isn't so bad.

thanks,
-ben

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Re: hard shifting

martinwinlow

On 24 Jun 2012, at 05:40, Ben Jarrett wrote:

>
>
> Hey guys,
>
> So I put the clutch back in my jeep to make it easier to shift (especially downshift).
>
> For the most part I'm happy to have the clutch back, except for one thing.  I start
> my jeep in 2nd.  I shift to 3rd around 35 mph.  When I shift, I have to let
> the clutch pedal out very carefully at about 2/3 of the way out.  If I don't,
> I get a decent drivetrain jolt.  Nothing too terrible, just a bit harsh.  If I'm careful,
> I usually do ok.  
>
> I think the issue is that when I shift, the motor is around 4000 RPM.  Since I have a 22 lb
> flywheel on the motor, when I shift, the motor doesn't slow down very much at all.  When I finish shifting,
> the motor needs to be around 2500 RPM. So during my shift, the motor has to change quite a bit
> of momentum.  My theory is that if I could lighten my flywheel (maybe go with aluminum), I could
> "fix" this.
>
> Has anyone else had this problem?  Are there other solutions (like some way to slow
> down a dc motor)?
>
> I don't have as much issue downshifting - my biggest problem is 2nd - 3rd shift.  3rd - 4th
> isn't so bad.
>
> thanks,
> -ben
>
>

Hi Ben,

I think you have analysed things correctly.  And yes, if you lighten your flywheel this issue would be reduced in proportion to the loss of flywheel weight.  I made a replacement one for my old van using a piece of 6mm mild steel plate.  The details are on my web site: http://www.winlow.co.uk/wychwood.co.uk/EV_Conversion_-_Part_5.html

One interesting issue of having weight in your flywheel is that you can use it to get a bit more efficiency out of an EV than ICE.  In the ICE the plug breaking or engine breaking effect is all internal and offers no way to get the inertia out of the crank shaft/pistons' motion. So it is wasted.  With the EV once the motor armature is spun up after you change gear and release the clutch you can get a little extra kick (as you have found) as the momentum of the which will go toward accelerating the vehicle a bit more.  Obviously you have to put the energy in first but at least you get it back again in an EV.

You would need a thicker plate as mine was a relatively low power engine (1.2l petrol), 10mm probably would be fine.  I would guess this would reduce the flywheel weight to around 14lbs (assuming it is 13" in diameter).  If you used alu you would have to go a bit thicker say a good half inch but because of their relative densities (7.85g/cm3 Vs 2.7g/cm3) your flywheel would end up at about 6lbs.

 
Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk

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Re: hard shifting

Jeffrey Jenkins
In reply to this post by Ben Jarrett
Ben Jarrett wrote
...Has anyone else had this problem?  Are there other solutions (like some way to slow
down a dc motor)?...
If your motor has a tailshaft you could use it to drive one or more of the OEM engine-driven accessories (ie - p/s pump, alternator, a/c compressor). The alternator seems like a particularly good choice because it requires the right amount of power (1-2kW) and performs a useful function (keeping the battery charged). Also, pretty much every car has an alternator, in contrast to the p/s pump and a/c compressor (both of which require much more power, too).

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Re: hard shifting

Roland Wiench
In reply to this post by Ben Jarrett
Hello Ben,

I had this same problem with my first EV which was a conversion by the
Electric Fuel Propulsion Co. back in 76. It had 180 V 300 AH battery pack
that weigh 3000 lbs which made the EV weigh about 7850 lbs.

Going to work every day up a 5 mile hill which was very steep at the last 1
mile, I had no problem running at 70 mph at a 180 battery ampere.  Coming
down this hill, the EV would get up to 85 mph and could have a rolling run
out of about 3 miles and right into my garage.   This was fine in the
summer, but in the winter it was dangerous.

Could down shift a heavy duty manual Saginaw that had over a 100 lb flywheel
in all the gears.

The motor was a GE-11 with a pilot shaft.  I install one of those air
condition electric clutches that I could engage with a 3 position  switch on
the console. This clutch ran off the a belt connected to taperlock pulley
that was on the motor pilot shaft.  I had a shaft built that attach to this
clutch which was mounted in two face bearings that was supported a 3/8 inch
aluminum plate.

This shaft then had a double pulley that was belted to a large alternator
that is design for a deep cycle 12 volt battery and also ran the A/C unit
and a 5kw 120 vac 60 hz inverter for my electric heating.

The 3 position switch had a auto-off-on position where in the auto position,
the accelerator control which had a micro switch in it would close every
time I would let up on the accelerator.  This would engage the alternator
which also had a 120 vac 5 kw inverter I use for three heaters and/or engage
the A/C unit for summer driving.

Going up hill, this accessory load would be remove and going down hill it
may be added if necessary.  A lot of times, I would just leave the accessory
load off the motor, where the EV would gain more distance than if I left
this load on.

At a heavy accessory load, it work just like JAKE brakes on a truck and with
a light load, it felt just like a engine compression load of a vehicle.

It was nice to see 0 motor and 0 battery amperes when moving down or
coasting to a stop and generating 13.5 to 15 vdc, 120 vac 60 hz, running the
electric heaters or A/C with a output up to 100 amperes.  Another form of
REGEN.

Roland






----- Original Message -----
From: "Ben Jarrett" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Saturday, June 23, 2012 10:40 PM
Subject: [EVDL] hard shifting


>
>
> Hey guys,
>
> So I put the clutch back in my jeep to make it easier to shift (especially
> downshift).
>
> For the most part I'm happy to have the clutch back, except for one thing.
> I start
> my jeep in 2nd.  I shift to 3rd around 35 mph.  When I shift, I have to
> let
> the clutch pedal out very carefully at about 2/3 of the way out.  If I
> don't,
> I get a decent drivetrain jolt.  Nothing too terrible, just a bit harsh.
> If I'm careful,
> I usually do ok.
>
> I think the issue is that when I shift, the motor is around 4000 RPM.
> Since I have a 22 lb
> flywheel on the motor, when I shift, the motor doesn't slow down very much
> at all.  When I finish shifting,
> the motor needs to be around 2500 RPM. So during my shift, the motor has
> to change quite a bit
> of momentum.  My theory is that if I could lighten my flywheel (maybe go
> with aluminum), I could
> "fix" this.
>
> Has anyone else had this problem?  Are there other solutions (like some
> way to slow
> down a dc motor)?
>
> I don't have as much issue downshifting - my biggest problem is 2nd - 3rd
> shift.  3rd - 4th
> isn't so bad.
>
> thanks,
> -ben
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
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> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>

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| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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