Efoil build using drill gearbox


Just started my build. I have decided to run with a battery drill gearbox. they are very high quality and are only around 20mm in length. This is the first run using a drill gearbox. ratio is 4:1. will replace the printed parts with alloy once Im happy with the design.
video here


That looks good. Excited to see how the gearbox holds up once under load. Where are you based?


@mp105, it is very interesting, since gearbox is most expensive and difficult to get part in whole the story. Please provide more details about the gearbox drill type (name, type or part name). Did you order the gearbox or disassembled it from some old drill?

Please keep us updated how it holds up in the water under the real load!


I’d be a little worried about the torque and the efficiency but I’m excited to see what happens! Please update with results when you can.


Hi there I am using 2nd hand drills get them for next to nothing and there are plenty around. Using a metabo drill gearbox at the moment as have 2 of them.


New Zealand how about you?


It is really nice trial @mp105! Can you please explain how did you attach such gearbox to the motor and prop side? Espessially propeller side mounting.


Hi mp,
Is the ratio of the drilling gearbox really 1:4?
I’ve dissasambled 2 different battery drill’s and they had a ratio from 1:2,…
The teeth in the pic look like mines.
Maby i’m wrong. can you share the Type of the drill?
I like the Idea verry much!:wink:


Hi there most drills us a 2 stage planetary gearbox. The one I’m using is the second stage which drives the chuck directly. I am using the shaft which the chuck screws onto to drive the prop shaft.


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First water test. Getting closer.
first water test.


This is really smart. I think I’ve found my source for DIY gearbox pinions.

The ratio of a couple of drills I have is 16:1 in speed setting “1” and in the speed “2” position is giving a 64:1 reduction. To be clear, MP105 is taking the second stage out and driving it seperately. On its own it gives a 4:1 reduction.

An easy way to check out what your drill has as the second stage is to compare the speed specs for setting 1 & 2. If speed 1 is 1/4 of speed 2 you’ve got a 4:1 reduction too!


I think this is a great idea!!! Currently looking up drills for sale second hand cheap as a trial. Great Shout!


You have to bear in mind that most cordless drill manufacturers like Dewalt replaced many metal gears with nylon gears between 2006 and 2010. Prestigious brands for professionals like Metabo, Hilti and Makita made two ranges nylon and metal. So before buying, you have to google the drill reference and avoid “light duty” devices and search for “general duty” or still better the “heavy duty” ones.

Don’t forget the corded drills. Manufacturers maintained metal gearboxes.

Very often, you can get them for free at your local dump. For this price, you don’t mind finding a nylon gearbox, you re-mount it and put it back in place (dump) for a second life :wink:


The nylon gearboxes should be OK for a while don’t you think? The design requirements for a shorter life drill are still pretty up there.