Model Machining Service: Mini Demon & Inner Demon

Model Airplane News, Sep 2003 by Gimlick, Greg

Adjustable gearboxes

Model Machining Service has proven its expertise in machining with its most recent offerings. The Mini Demon and Inner Demon gearboxes are not only versatile, but they're also beautifully machined. One of their biggest benefits is that you can go to a local hobby shop and buy pinion gears right off the shelf. You can change the ratio of the Mini Demon box from 3.5:1 to 7.5:1 in minutes. The same goes for its bigger brother the Inner Demon, but the ratios range from 3.3:1 to 8.3:1.

If you've struggled with how to mount electric motors, these boxes have the solution. Each has an "EZ Mount" system that allows you to bolt it directly to the firewall.

The gearboxes also support single or dual motors ganged to a single prop. For as long as I can remember, folks have argued about whether ganging motors works, but all agree that if you do it, you must be sure to match the motors by properly timing them.

For my tests, I ganged two Kyosho Endoplasma motors on the Inner Demon gearbox and geared them 6.6:1. On 20 cells, they turn an APC-E 17x10 prop at 5,400rpm to provide more than enough power to hoist my 8.5-pound Dymond Modelsports Ford Fliwer skyward.

I used a single, 6V, Speed 400 motor on 8 cells and the Mini Demon gearbox geared at 4:1 to power a Northeast Sailplane Virus 400A. I was able to change the gear ratio and remount the system in a matter of minutes.

The Mini and Inner Demon gearboxes weigh 82 and 231 grams, respectively, so you need to plan accordingly, but they are extremely well made and sturdy. Their weight wasn't a factor in the models I tried them in. The Mini Demon costs $69; the Inner Demon costs $84.