Thursday, April 21, 2011

Pot box issue resolved

April 20, 2011 - Last time I blogged about how the pot box from Mark Hazen at EVHelp wasn't working out with my throttle cable and how I had ordered a Curtis PB-6 to replace it. A couple of days ago Mark e-mailed me to see how things were going with the conversion and I relayed to him the problem I was having and how I was going to solve it. It's a good thing Mark and I had the mail exchange because I found out that the Curtis pot box won't work. Here is what Mark had to say about that: "The Curtis PB-6 throttle control will NOT work on my controller. It will cause the controller to start at full throttle with a huge surge in power that will jerk your head back and perhaps destroy the controller and cause an accident in your garage."

Hoo boy, what a catastrpohe waiting to happen. Mark pointed out that the Ohm range in his pot box was backward (2KOhm - 0Ohm) and different than the Curtis PB-6 (0Ohm - 5KOhm) and he does make reference to the range in his installation manual but does not note that his controller is incompatible with the Curtis pot box.

Anyhow, he recommended that I lower the position of the cable attach point on the pot box arm to accomodate the short throw of my throttle cable. It took two tries but I finally got it right. What didn't help was the fact that the throttle cable was also partially binding on the clutch cable assembly preventing full throw of the cable. Once I figured out where it was binding and freed it up, the cable travelled full distance and freely.

I also had to extend the offset on the pot box from 1-1/2" to 2-1/2" to allow this additional length. Once I had the new offset mounted and attached the cable, when I pressed the accelerator pedal fully, I got full deflection on the pot box. And yes, I plan to fabricate a thicker and stronger offset than the thin aluminum one shown. Whew!! Anyone wanna buy a brand new Curtis PB-6 when I get it? $80 plus shipping.

Here's the pot box at zero deflection:

And at full deflection:

April 21, 2011 - Update to resolution. OK, my boss Adam Kreuger and EVHelp's Mark Hazen must be smarter than me because when they saw my offset they both just kind of snickered and said "get rid off the offset and just cut the cable", independently of course. DOH!!!! Thank goodness for out of the box thinkers. Of course, I soldered the end of the cable so it won't fray. I'm worried that the cable may slip in barrel connector so I will also solder the cable area that is being clamped down on for extra hold strength.

So here's a pic of the zero offset zero deflection:

And another at full deflection:

Now just to mount the pot box on the firewall. Oh, and Mark also lamented that I should pull the controller off of the firewall to allow air flow. I'm guessing 1-2 inches should suffice plus the addition of a ram air scoop that dips below the firewall should force enough air over the cooling fins to keep it from over heating. He also mentioned that I may want to look at adding some sort of high volume blower that blows lengthwise over the heatsink fins.

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