Team Kaizen Build Diary

[Ocracoke]

Azriel
So I thought I would go through the various stages of doing a brushless conversion. As a forewarning, I am not claiming in anyway that this is the best or ideal way to do this. This is simply the method I am using, your mileage may vary etc. Anyway, today I did the physical conversion and later on in the week/weekend, I'll do the brushless speed controller programming.

To give an overview of the things typically listed on a brushless motor, this motor is listed as a Turnigy XK3674 1650kv motor. That means that the motor diameter is 36mm and the length is 74mm and, for every volt applied to this motor when under no load, the motor will spin 1650rpm as I understand it. Originally, I chose this motor when I thought about doing a brushless conversion on Kaizen at the time. As a result, this motor is specced to run at 8S LiPo, meaning a no load speed of (3.7 * 8S) * 1650 = 48,840 rpm with a theoretical max current of 70A. For the budget I had at the time, it seemed to be the best balance of output speed and power I could find. Wherever I'll regret this later on remains to be seen.

Here are most of the parts I am using. From left to right, the Turnigy XK3674 1650kv motor, 2x M3x10mm bolts and a Gimson 13.7:1 motor with the 775 motor attached. The only thing not pictured is a 17T 0.6Mod pinion gear but as that is already attached to the brushless motor.
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First thing I needed to do was cut down the M3 bolts a bit as the depth of the holes in the motor is quite shallow. If you are doing this, I'd recommend the 6mm bolts, I think they'll fit nicely. The next thing to do is shave the shaft off the motor with the pinion gear attached. The easiest method I found to do his is to get the pinion gear on the shaft as far back as the D shape goes and then cut off the excess. Not doing this will cause the shaft to foul in the gearbox.

Before:
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After:
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The next thing to do is get the 775 motor off. To do this, lay the motor on the ground and with a suitable allen key, undo the four bolts on the gearbox. These run the length of the gearbox to connect to an adapter plate between the motor and the gearbox. Make sure you don't, whatever you do, allow the assembly to be vertical as it will all fall apart and will require greasing and cleaning before reassembly.

Once the 4 bolts are out, pull the motor away from the gearbox, which will reveal the plate. Undo the 2x M4 bolts with the allen key.
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Once the M4 bolts are undone, get the M3 bolts and place one in the adapter plate and then get the brushless motor and get that bolt in. Once done, swing the plate a little until the opposite bolt hole is lined up and then put the second bolt in. Note that not all brushless motors will fit this (under 50mm diameter I think should) and even then, not all motors have the right M3 or M4 spacing for this plate.

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Once the plate is on, get the motor back into the gearbox, which will require a bit of patience to get it seated properly, especially given that the gearbox will want to seperate apart. I try using a pair of fingers around the face of the gearbox to the shaft to hold it in place as I am reinserting the motor. Once in, screw in the 4x bolts when it is all lined up.

The net result is this.
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One thing to be careful is the gearbox, when opened, has a very thin metal plate to keep the gears in the gearbox. This plate often comes out with the adapter plate. Make sure that is placed back in the gearbox body correctly (i.e. flat) in the body before replacing the motor otherwise it'll prevent the motor from spinning in the gearbox and thus, seize it up.

Given the much narrower body of the Turnigy motor over the 775 motor, it might be worth supporting the rear end of the motor with a HDPE block. Next time, it'll be the ESC programming.