# [EVDL] Return Spring Too Strong



## EVDL List (Jul 27, 2007)

I've been driving the MetroLectrical to work for two weeks now, and overall
I'm pleased with the EV. My only disappointment has been that the car is
very jerky to start up--which I've been attributing to those damn cheap PB-6
potboxes and their dead spots. Well, the jerkiness indeed did turn out to
be caused by the potbox, but not for the reason I thought. In fact, it was
my own damn cheapness that was making it happen. For safety reasons, I had
installed a second return spring on the potbox's control arm. I just used
whatever spring I could find lying around the house at the time. Turns out
the spring was a little too stiff. When I took it off and drove the car
around the block today, all jerkiness was gone. Guess I'll run out to the
hardware store tonight and buy an appropriately sized spring to replace the
old one.

Tightwad Bill

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## EVDL List (Jul 27, 2007)

Hello Bill,

I find that the original coil spring that came with the pot box, may not 
return to less than 50 ohms. Less than 50 ohms is needed so the Z1K 
controller will start up. There is a some accelerator cable resistance and 
the fastener point on the accelerator pedal is not rigid.

I change this accelerator cable with a heavy duty type that is use on 
semi-trucks that is very slippery no matter how many turns it have. It has 
positive rod ends with a bearing in it. The accelerator peddle has a large 
coil L spring that returns the accelerator cable to the normal position. 
This pushes the pot box lever to the stop position.

Another thing I did before I did the above modification, was to rotate the 
accelerator pot box coil spring about a 1/4 turn tighter. Use a small 
aircraft cable clamp that is fasten to the upper right pot box cover screw 
for the spring to hook into. This work good for returning the lever to the 
stop position.

After driving 9 years with the PB-5 pot box, I notice there is a high 
resistance spot where the wiper contacts the coil which is not critical yet. 
I always like back up circuits and equipment, so I install another PB-5 pot 
box circuit wires so I can either switch out the one PB-5 or even switch the 
circuit wires in series. The second PB-5 is dash control. I can add just 
enough resistance, so the original pot wiper is off that contact spot.

Also this second pot becomes handy so I can idle the motor when I do 
maintenance of the A/C system, Alternator-Inverter unit, water pump for 
heating and water pump for cooling the controller.

I also find that I know that I have to come a quick stop and go stop, I will 
turn on the idle control, so the motor does not run below 500 rpm. This 
decrease the high motor ampere surge when starting up again and do not have 
to shift to a lower gear.

Roland




----- Original Message ----- 
From: "Bill Dennis" <[email protected]>
To: "'Electric Vehicle Discussion List'" <[email protected]>
Sent: Friday, August 05, 2011 11:52 AM
Subject: [EVDL] Return Spring Too Strong


> I've been driving the MetroLectrical to work for two weeks now, and 
> overall
> I'm pleased with the EV. My only disappointment has been that the car is
> very jerky to start up--which I've been attributing to those damn cheap 
> PB-6
> potboxes and their dead spots. Well, the jerkiness indeed did turn out to
> be caused by the potbox, but not for the reason I thought. In fact, it 
> was
> my own damn cheapness that was making it happen. For safety reasons, I 
> had
> installed a second return spring on the potbox's control arm. I just used
> whatever spring I could find lying around the house at the time. Turns 
> out
> the spring was a little too stiff. When I took it off and drove the car
> around the block today, all jerkiness was gone. Guess I'll run out to the
> hardware store tonight and buy an appropriately sized spring to replace 
> the
> old one.
>
> Tightwad Bill
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere. Thanks.
> |
> | REPLYING: address your message to [email protected] only.
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> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

I am baffled by the complaints about the Curtis potboxes. In the 
past 30 years, I must have sold a couple thousand of these, and I can 
count on the fingers of one hand the ones I have had to warranty. At 
one point, I was supplying them to Solectria. My prototype 
VoltsRabbit is still running on the original potbox after 20 
years. Most potbox "faults" turn out to be inadequate springs, 
mounting brackets that are not sufficiently rigid, or poorly adjusted 
throttle cables. Curtis sells hundreds of thousands of these every 
year, and has been doing so for decades. I can't believe they would 
come to dominate the industrial EV market if they had an inferior product.

Mike Brown
Electro Automotive, POB 1113, Felton, CA 95018-1113 Phone 831-429-1989
http://www.electroauto.com email [email protected]
Electric Car Conversion Kits * Components * Books * Videos * Since 1979


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## EVDL List (Jul 27, 2007)

>> Ah; but you live in a place that doesn't have weather. 



> Mike Brown wrote:
> > That depends on your definition of "weather". Last winter, we had
> > 60" of rain, about typical. We live in the fog belt, so almost every
> > morning, everything is dripping until it burns off. We're about 4
> ...


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## EVDL List (Jul 27, 2007)

I'm very interested in this discussion because my PB-6 often shows "jumpy"
behavior. My box is under the hood, on the firewall and without any
additional box. Also, I live on a 1/4 mile long gravel driveway so
everything is always covered with dust. The car is kept garaged when at
home, but it still has to drive down the driveway each day.

I have found that turning off the key and pumping the pedal full stroke
several times does help. However, the jumpy behavior often returns within
the same 1/2 hour drive. This seems worse in the morning for some reason. 

Is it possible to open these up and clean them? Is that reasonably easy or
are there some tricks? Anything to watch for when enclosing the PB-6 in a
box?

Mike

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Lee Hart
> Sent: Sunday, August 07, 2011 1:15 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Return Spring Too Strong
> 
> >> Ah; but you live in a place that doesn't have weather. 
> 


> > Mike Brown wrote:
> > > That depends on your definition of "weather". Last winter, we had 60"
> > > of rain, about typical. We live in the fog belt, so almost every
> > > morning, everything is dripping until it burns off. We're about 4
> ...


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## EVDL List (Jul 27, 2007)

My Curtis potbox is short coupled to the pedal inside the car. It is my
suspicion that the lack of cable sticktion causes much more cycling around
the cruise position in my car due to the mass of my foot shaking with road
bumps. I believe that a cable would reduce this movement. Or maybe the pots
are just no good! 

I buy an average of one replacement pot element every two years from KTA
services since it's much cheaper than the whole pot box. At this time I'm
being lazy and just stomping on the pedal with the key off, but now the off
resistance sometimes sits at 200 ohms and I often have to clean (stomp) it
to get the controller to start up since it wants 150 ohms or less.

Lee, do you have a part number for a good sealed replacement that I could
try next? 

-----
-Otmar-

914 EV, California Poppy, Zilla research vehicle. 
http://evcl.com/914/

The Zilla factory is at:
http://manzanitamicro.com/

Zilla Support is still at: 
http://cafeelectric.com/Ssupport.php
--
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## EVDL List (Jul 27, 2007)

> Otmar wrote:
> > Lee, do you have a part number for a good sealed replacement that I could
> > try next?
> 
> ...


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## EVDL List (Jul 27, 2007)

Mike,

Have you tried wiring the pot up to an analogue ohmmeter to see what 
the resistance is actually doing as you start moving the pot arm from 
zero (or 5k or whatever it is)? This might give you an idea of where 
the problem lies...

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





> Mike Nickerson wrote:
> 
> > I'm very interested in this discussion because my PB-6 often shows
> > "jumpy"
> ...


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