Tractor in trouble..

Here’s the challenge. A’s tractor is great, but it’s too hard to pedal, and we’re scared of him or some other kid getting feet crushed in the pedals while being pushed enthusiastically from behind. Plus, for a boy who doesn’t ask for much, he really really wanted an underpowered electric quad bike he saw in Halfords. He also wants to help in the garden, which is definitely to be rewarded.

So, can I convert his big green tractor into an electric vehicle with a foot throttle – and by Christmas?

This has been done in different ways before, like on Hackaday but I don’t want handlebars – limitable foot controls are the way forward.

The other way is with brushless motors direct on the wheels like this guy did, but that looks like he’d have to be too controlled by an adult.

Combi drill it is then.  Off come the pedals, out comes the back axle and a spare 23 tooth chain ring is tack welded on so I can at once add more torque and slow the speed down.

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Most drills now have variable speed triggers that I can use for the throttle somehow. Plus they have a forward and reverse switch.

Then I have a problem of where to fix the drill so the drive cog is in line. Others have stuck the drill outside, but I know this is going to get left out in the rain, and anyway, A is as particular as his mum, and I agree it would look rubbish.  I also need to be able to get to the battery easily to take it off to recharge, and he might go through puddles.

Difficult. Tractor has a narrow body.

Ah – impact driver! Squat motor and great torque. £35 on eBay.

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Some ‘welding’ or melting of cogs to driver adapters later and it doesn’t look great. To keep the gearing ratio and stay on the centreline, even the impact driver would stick out the side.

If only I could have the drill at 90 degrees to the axle. Most right angle drill adapters are 1:1 geared and would only power one wheel. Bevel gears? £30 per gear looks a bit much, and then I have to make a housing, bearings and fit it all in a confined space.

I keep coming across angle grinder bevel gears when I search for some with 12mm diameter holes in. Plus most of these things seem to come on a slow boat from China.

Perfect – I’ve been meaning to buy a new angle grinder for ages. Bearings and housing all sorted.

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Just need to cut off some of the redundant bits…

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And look at that.  It works. Gearing ratio is perfect – something like 2:1, and I get loads of angles to position the drill. And Combi drill it has to be, because the impact driver makes too much noise and will damage the gears.

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Next job is to drill a hole through the back of the grinder housing to let the axle through…