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913 Posts

The less obvious would be to connect a 50 ohm resistor in parallel which will drop the overall resistance (assuming your exising resistor is 55 or 60 ohm) to around 25 to 30 ohms.

Copper wire isn't suitable, you'd need a vast length of very thin wire to make 35 ohms.

Resiatance wire is more difficult to come by.

Maplin do constantan resistance wire but only in 28 AWG , that's 4.2 ohms a meter. You could measure up your resistor and work out how much wire you can get on it, If your resistor is big enough to wind 8.3 meters that'll give you 35 ohms.

Like slotcarscrapyard, I'm not sure its worth doing with that controller

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3,629 Posts

It would have to be wound with the wire touching to get all those turns on, then rub off the enamel where the wiper runs.

Not sure how long wire that thin would stand up to a wiper rubbing on it and motor stall current is close to the fusing current.

Try it if you like but don't be surprised if it doesn't last long.

The Parma is much more practical.

Hi RichD, what do you mean by "non linear response" ?

I owe a 60 ohms Parma i fitted with 2 resistors and a 3 position iterruptor, so it makes a 60/40/20 ohms, and I'm quite satisfied with it.....i did not really saw a difference in the curves response ?

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1,947 Posts

Then you are going to end up with a bunch of parts that cost close to what a new parma Economy would cost and still not have a controller that works. Save up and just buy a new controller. Geez they are only around $30.

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3,629 Posts

Suppose that we try to make a 65 ohm controller act like a 25 ohm controller. RE = 25 and R1 = 65 in that case. 1/R2 = 1/25 - 1/65. Therefore R2 = 40.65 ohms. The problem crops up when you squeeze the trigger more. See the chart for a comparison of 25 ohm, 65 ohm and 65 ohm with a parallel 40.65 ohm fixed resistor.

The 25 ohm controller and the modified 65 ohm controller are clearly not the same. The effect is not as drastic if you do not try to lower the effective resistance too much. I shall point out that some people like controllers like that. You should give this idea a try and see how you like it.

Half the wire equals half the resistance. If you have a multimeter you can measure accurately for the right resistance. Attach one probe to the end of the wire, then move the other along until you get the desired resistance.

Wind the wire carefully back onto the core, soldering the ends back on where they came. Clearly with less wire you will have fewer turns but it's relatively easy to space them out.

Use a heat-resistant paint to secure it all - not epoxy.

Simple and cheap!!

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