# Better reverse gear control?



## MBEV (Sep 28, 2008)

Has anyone given any thought to making reverse a bit tamer on your garden variety small DC motor EV conversion? A couple of conversions I have driven recently are fine in 3rd or 4th gear but a bit “aggressive” in reverse (obviously a low gear ratio by design anyway) which can make reverse parallel parking difficult if not totally familiar with the car. My 72v Alltrax controller is programmable to an extent but the throttle curve applies for all gears. 
Any Ideas out there??


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## madderscience (Jun 28, 2008)

My (slightly extreme) solution (which really was for a different reason: reducing friction) was to eliminate the mechanical reverse gear completely. I have reversing contactor instead and can use any gear in reverse.

So yes, my car will do 70mph backwards.  If I were dumb enough to try.

Of course since my reverse is electronically controlled there is no reason why I could not use more relay controls to add in some extra resistance in series with my throttle potbox, effectively throttle limiting the car while in reverse.


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## MBEV (Sep 28, 2008)

A bit late to go that way now but a good idea….. 

 BTW nice MR2 conversion

Was thinking of switching a resistor across the pot box (ie in parallel) using the reverse switch built into the gearbox (the one normally used for the reversing lights). My configuration is setup for 0 to 5K so maybe something in the range or 270 or 470 ohms??

Just a thought…..


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## DIYguy (Sep 18, 2008)

MBEV said:


> A bit late to go that way now but a good idea…..
> 
> BTW nice MR2 conversion
> 
> ...


I read somewhere that someone did this and it worked well. Try some more searching. If not, I would go for it... it makes sense.

cheers.


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## PatricioIN (Jun 13, 2008)

what controller are you using? I have a Curtis 1221C and I find reverse to be no different than with the ICE. You just don't "stomp" on it! lol


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## 84bertone (Apr 10, 2008)

I wired a 1K, 5 turn, linear potentiometer in parallel with the pot box. It is selected via a DPDT switch. Control for reverse is really, really smooth.

Here is the procedure for reverse. Insure linear pot is turned completely to the left or zero. Throw DPDT switch to reverse position. Place transmission in reverse, step lightly on throttle to energize KSI relay. Turn linear pot to go backward. And the car goes ever so smoothly backward with completely control.


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## rfengineers (Jun 2, 2008)

DIYguy said:


> I read somewhere that someone did this and it worked well. Try some more searching. If not, I would go for it... it makes sense.
> 
> cheers.


That was me. I put a 2.2K resistor in parallel with the throttle pot. The resistor is switched in and out with a relay that is controlled by the backup light circuit.

It works quite nicely.


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## bblocher (Jul 30, 2008)

PatricioIN said:


> what controller are you using? I have a Curtis 1221C and I find reverse to be no different than with the ICE. You just don't "stomp" on it! lol


Same here, the Curtis 1231C is also very controllable with speed including reverse.

I think this may come down to the "whine" feature we have that steps down our voltage to protect the motor. It also allows us to creep along. Perhaps these other controllers are solving it by just giving more power to get the motor to get them rotating as quickly as possible?


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## Jimdear2 (Oct 12, 2008)

MBEV said:


> My 72v Alltrax controller is programmable to an extent but the throttle curve applies for all gears.
> Any Ideas out there??


 
A quick question to those in the know. I havent see this Alltrax Controller feature mentioned in this thread and I'm curious.

I have an Alltrax 7245 and it has a terminal (terminal four, I believe) that is called half speed reverse. As I understand it this feature, when energized, holds the controller amprage back and does not allow high speed on electrically reversed motors. Actually I guess it just limits current output period, the motor reverseing is done with contactors.

I have not reached the point in my build where my controller is operational, so I cannot test this myself, but wouldn't that slow down the response. 

Maybe all it does is limit current, without changing the rate of ramp up. I don't have my controller manual at hand so I can't tell.

Any help here for your problem?

Jim


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## MBEV (Sep 28, 2008)

Jim you are a star!!

And correct.....

_______________________​ 
_½ Speed Reverse_​Limits speed of car to 50% of throttle setting when pack + is applied to this pin.
_____________________

Not sure how I missed this but it solves my concern.


Thanks Again

Bruce


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## Jimdear2 (Oct 12, 2008)

When you try it out, Please post the results. 

We are planning to use this feature as a kidde control on the electric pulling garden tractors we are building. There is a class for kids starting them out as young as 5 years old and we are using some fairly large motors. So this will be perfect.

Jim


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## MBEV (Sep 28, 2008)

No problem....

Will be in a couple of weeks.

Cheers

Bruce


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## EV59RAG (Oct 6, 2008)

Any update on this...?

I have the same situation... and also using Alltrax 7245. Believe me.... its impossible to tame the reverse... the tires spins so much that you can hear it squeaks...... 

So did you just put power on the 4th pin (1/2 speed)? does it need to be pack voltage?

If you can elaborate more... 

Thanks


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## EV59RAG (Oct 6, 2008)

Ok guys,

Ive talked to Alltrax guys, and they said that I just need to energize it. The power can be tapped from pin 1 (or pack voltage).


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