Gear Reduction

This page shows a few ways to reduce the speed of your model.

Fab a New Gear Reduction Box for the KT

I was going to try this method until I found out that there is not enough room for this unit inside the KT. Maybe it can fit in other tanks with more vertical clearance. Therefore, I left the idea and drawing attached.
Basically, I was going to build a gear reduction unit that attaches between the motor and the existing motor mount. The gear reduction ratio will be 2.5:1. Here is my plan. I will remove the motor and mount a 12T, 48P Losi pinion gear to it's shaft. Next, I made a front and a rear mounting plate to support the motor and the new drive shaft. These plates will be bolted together with spacers to make a little gear box. Then, I will mount a 30T, 48P Losi pinion gear to a 1/8" dia. shaft that is supported with two motor bushings soldered to the mounting plates. The old KT 15T metric pitch pinion gear will be mounted on the same shaft as the 30T. Now, the motor is attached to one side of the gear reduction unit and then the whole setup is attached to the existing KT motor mount holes. I will also add a spacer between the unit and the existing mounting plate to allow for protruding bolt heads on the reduction unit. A zipped Autocad drawing of the unit is available. Note: the dimensions on the drawing are approximate. Basically, I only had a scale to get them. You should verify them with more accurate equipment if you actually want to build the gear reduction unit.

Use One of the KT Turret Gears

This way requires taking one of the extra gears out of the KT turret drive and using it to gear down the tank. Here is what Rich Upton did to install this upgrade. First, remove the lowest turret gear on the pinion side and replace it with a spacer so that the turret drive still operates correctly. Next, move the clutch shafts (I had to create new shafts myself since the old ones were not long enough, I used 5/32" drill rod) out as far as they will go and add a spacer between the motor and the gearbox vertical plate. You then mount what now becomes the reduction gear on a short post (I had a friend turn one down for me to 0.159") to the left of the motor (mine seemed to work better on the right side). The motor pinion now drives this big gear which has a small gear molded in the base that drives the clutch gear. He estimates that the tank goes about 40% slower and can climb much easier. Others have noted that the clutch mounting holes may need to be elongated to accomodate this setup (I had to do this as well as remove some of the metal at the back of the mounting plate). Here is Rich's drawing. I also have a picture of my setup.

KT Pinion Gear Changes

This method involves replacing the existing 15T pinion gear with a smaller one. An 8T or 9T one would be nice, but I have not been able to find one that small in the proper pitch. The Old version King Tiger that I own uses gears with a metric pitch somewhere between a 32P and 48P. In addition, the motor mount holes must be elongated to accomodate the smaller pinion. Ken Hofmann was able to find a 12T that is used on the Tamiya TA-03 cars but felt that the small gains in speed reduction were not worth the hassle.

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