15 May 2008

Modification - the throttle

Originally the pot box (the little thing that translates the go pedal to the speed controller) was mounted on the main cluster. It had a very large spring attached and really occupied a large space. This particular pot box can be susceptible to dirt and water. With the control arm just hanging out in the air, it would be possible to bump it with the hood open. I want it in an enclosure and I want it tightened up.

So I brought home an old water proof enclosure from work that I though would be useful. Using some scrap aluminum I made a mounting plate to fit inside and hold the pot box. But I couldn't figure out where to put my nifty new box. It had to be at the end of the cable, and I wanted it out of the way of everything. After weeks of thinking and test fitting I decided the cable was just too long. So I took a different approach. First ask "where do I want the box?" and then figure out how to get the cable there. I quickly found some holes on the firewall that I could mount a plate to and now I have a nice flat surface to mount the box to.

Now I must fit the cable. Knowing it will have to be shortened I cut off the stopper on the end of the wire in the motor bay and pull it out of the cable. This wire has chunks of metal formed on the end to pull against and now I will have to figure out how to reattach one end (later). I used a cutoff tool to shorten the cable so it would route to the box. Then I also cut off the threaded adjuster end from the cable and reattached it to the new shorter cable.

To put a new metal chunk on the end of the wire I had an ingenious idea! I made up a little form from aluminum stock that would hold the wire and allow me to pour melted metal into the cavity. At first I was thinking of using aluminum, but then I remembered I had some lead shot (I don't know if it is pure lead or an alternitive). So I melted that up and poured it in. When I tried to remove my new plug, I couldn't get it out! Eventually I was trying to drill it out and the drill bit grabbed it and ended up mangling (and breaking) the wire! Now what?!

I have some aircraft cable sitting around, but it was too big to fit inside the throttle cable. Then I came across some extra bicycle brake cable from my last repair job. It was just a few tenths of a millimeter smaller than the original, and had finer strands. Thats a good thing because I'll be bending the cable tighter than it was originally. This time I cut my stopper form in half so I could just open it up to remove the cable. It worked perfectly! I had a nice metal chunk the same size and shape as the original on the end of my new wire. So I used the same method for the pedal end (after putting the wire into the cable of course). I needed to add a good spring in the system to help pull against the pedal, two springs are safer as well. The original had a very large spring about 8" by 1". I needed one to fit inside my enclosure. So I grabbed some 0.047" music wire that I had and wrapped it around some 1/4" stock in my lathe. Out came a perfect spring that makes the pedal feel just like would in a conventional car!

During testing it became apparent that I made the wire-sitcking-out-of-the-cable too short because when the pedal was pushed to the floor by my lovely assistant, it popped the metal stopper off the end! I didn't like this stopper idea anyway and decided to use a clamp instead. I would also need more wire coming out of the cable to prevent this wire-too-short problem.

I just moved the box farther to the right, which clears up more space on the left for me to mount something else when I think of it. This gave me about 6" of cable to trim down and easily fixed the cable-too-short issues. Now you can floor the pedal and the cable clamp just about touches the cable end. If you're wondering, the red and green wires still need spade connectors on them to connect to the micro switch that indicates when the throttle is all the way off.

I painted the bracket to prevent rust and blend it it. I was going to paint it black, but I noticed a can of copper color paint that matched the car pretty well! I think this is the final incarnation of the throttle assembly and I declare it done (pending the spade connectors)!

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