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.

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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.

Any ome have any more pictures of this? Dump up the road has few drills. What’d be a good example of a drill thatd have this kind of gear setup?
Been seafching data sheets and for practise I took apart a real heavy duty drill (hammer action) but the gears dont look useable!?!? Should it be a heavy duty standard drill instead of a hammer action? Pics of one i took apart attached

To be honest, I don’t know. Time and usage will tell. Even if the life expectancy is divided by 3 (say) for Nylon (melting point 250°C) compared to metal , 50 remaining hours means more or less 50 sessions to decide whether the drill gearbox is a suitable solution.
The issues being that:

  • when the 2nd hand gear box has too much wear, you will have to find another one to fit in the existing efoil motor design, with possible redesign if the screw footprint is different.
  • a drill gearbox has an up time of 10 to 20% (80% rest time), an efoil close to 100% with a skilled surfer so life expectancy will be 4 or 5x shorter on an eFoil compared to the use inside a drill.

Rather than buying a second hand drill that you might not be able to replace identically, a decent solution would be to buy directly a brand new metal gearbox costs 25 GBP or 30EUR as spare part. Once you have identified the cordless drill with metal gearbox, it is easy to find a – NEW - gear box on the net. If this NEW gearbox fails after (say) 150 sessions, you don’t have to redesign everything around it since the replacement Gearbox will be new and identical.

Example with MAKITA range (to be continued).

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Ya i see the point but what make and model of a drill could i but the spare part gearbox for?

Right. Would be great to know which model(s) to look for, suitable metal gerabox. Makita I scrolled thru lots of exploded drawings with no luck, or at least I did not find the a drill with planetary like we need

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Interesting description here about the Makita 8444DWAE


MXT is the next generation in drilling power and control; high speeds of up to 1,700rpm can be achieved within seconds. MXT is the fastest, strongest drill range on the market today.

The technology behind the MXT range or Makita Xtra Torque makes all this possible. The machines have 3 different speed settings for versatility and 16 torque settings, which in the 18 volt machine, delivers up to 80 Nm of torque.

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