RC Car - MadCap - Looking For Speed

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MadCap - Looking For Speed

Comments: I have a Tamiya Madcap(basic buggy stock motor). I upgraded to good oil shocks and knobby tires. It has the original gears, 23 pinion and spur is 70 teeth. It reaches top speed fast, probably in a couple seconds. I'd like to double the top speed by changing the gear ratio. I can't go to a modified motor because I only have a mechanical speed control. I will sacrifice torque to get a good top speed. What gears do you think I could use. It might be doing 20-25 MPH now.

Thanks for any suggestions

Response: First, are you sure you can change the gear ratio in the Madcap? I didn't think you could. If you can, great! If you want to reduce the acceleration of your car and increase the top speed, you need to put either a bigger pinion gear or smaller spur gear into your car (say a 25 or 26 tooth pinion or a 60 to 65 tooth spur). Be careful not to go too big on the pinion or too small on the spur or you will "over gear" your car. If you "over gear" your car you will loose speed and acceleration as well as permanently damage your motor (and speed control). Check out How Gear Ratios Work and How Do I Choose A Pinion Gear. These are both good articles on gear ratios that may help you.

About your motor. You can install a mild modified motor (17 turns or higher) into your car with the existing speed control without burning it out. You just have to remember a few things about how a mechanical speed control works. When your speed control is in the fastest speed (third speed in your case) it is connecting the battery directly to the motor just as an on/off switch does. When the speed control is at full speed, there is very little resistance and it will last for ages. The problem with mechanical speed controls are when they are in the middle speeds (1st and 2nd speed for you). This is when the batteries current is sent through the resistor to reduce the cars speed. If too much current is passed through the resistor for too long a period, the resistor will burn out and need replacing. This is even more evident when a modified motor is used.

So what is the solution? don't drive in the 1st and 2nd speeds for too long. Try to go full speed as much as you can (this shouldn't be too hard). If you are just kicking your car around and you have a large area to drive it in, staying at full speed should be easy and more enjoyable for you anyways. Try to only use the middle speeds for acceleration and slow turns, otherwise, rip on it!

You are very correct that changing the gear ratios is an effective way of altering your vehicles speed characteristics but you will never be able to double your cars top end with gear ratios alone. Try a faster motor but keep my advice in mind. Don't buy a super fast motor and stay out of the partial throttle range. Who ever gave you the advice about not using a modified motor with a mechanical speed control is giving good advice but as you can see, there are ways around it. I know how it is when you want to go fast but you can't afford an electronic speed control (we were all there at some point).

Let's take off a few tenths per lap,

"PRO"
Pro Racer Secrets