2025-06-14

Last modified: 2025-06-14 15:19:37

Tractor

Latest CAD is:

I've built a wooden box for the central part of the chassis.

The only actual things that need doing are:

• rear axle
• front axle
• steering
• brake
• wiring
• seat
• mud guards
• foot plates
• central dashboard bit
• bonnet

Rear axle

Waiting on:

• steel
• sprocket
• bearings

I'm thinking that once the sprocket arrives I will make up a little steel plate that will bolt on to the sprocket and weld on to the axle.

So processing on the axle is:

• cut to length (oversized, remember the wheel nuts)
• turn ends down to 19mm to fit wheels
• turn threads on ends to suit wheel nuts
• machine/grind/file flats on ends to suit wheels
• weld sprocket plate on
• bolt sprocket on
• wrap chain around sprocket
• slide bearings over ends
• bolt bearings to frame
• bolt wheels to axle

Front axle

???

I know I need 16mm spindles. I have ordered some 16mm steel just in case but may end up using M16 bolts instead.

I'm thinking I want a swing axle.

Waiting on CAD, inspiration, I guess?

Steering

???

Today we 3d printed a steering wheel for Lucy to play with, but it's not very good and only printed at draft settings in PLA. For the real one I would use "strength" settings and probably PC-Max.

Apart from that, we need linkages or whatever to transfer rotation of the steering wheel to rotation of the front wheels.

Waiting on CAD, inspiration.

Brake

I'm thinking I have something gently rubbing against the rear axle all the time, adjustable. It just needs to be enough of a brake to stop it rolling down the steepest part of the garden.

In the future we could upgrade to a real brake, but it's not a requirement.

Waiting on rear axle.

Wiring

Battery goes under the bonnet. Motor obviously goes under the chassis box, at a point to suitably tension the chain. Throttle pedal goes on the right foot plate. And maybe a key switch on the dashboard.

The speed controller doesn't have any way to ask it to reverse the direction, so I am thinking of installing some high-power DPDT switch to swap the wires going to the motor, and then some sort of lever that looks like a gear lever and lets you flip the switch.

Waiting on rear axle.

Seat

I'm thinking take the plastic part off one of those child's primary school chairs:

So need to acquire something like that.

And then work out how high it needs to be, and make some sort of box to sit on top of the main chassis bit, at the back, to bring the seat up to the right height.

Waiting on acquiring a seat, rear axle

Mudguards

Probably make these part of the same box piece that brings the seat up to the right height.

Waiting on CAD, inspiration.

Foot plates

Obviously these are just plywood rectangles, I'm thinking of making a "carrier" for them out of angle iron which will bolt to the central chassis piece so that they are strong enough to stand on. So imagine a length of angle iron running horizontally across the chassis at front and back of the foot plate, and then each one has another couple of pieces welded on to it that run vertically and bolt to the chassis.

Waiting on CAD for mudguards.

Central dashboard bit

This will be a plywood addition to the existing chassis, will be used to mount the steering wheel, bonnet, and dashboard.

Waiting on CAD, inspiration.

Bonnet

This will be a plywood box with potentially 3d-printed corner pieces. This can probably be the last bit I make. It doesn't do anything functional, just completes the look. Maybe we could mount some headlights on it eventually.

Waiting on CAD, inspiration.

So actually, when you put it like that, most of this is blocked on CAD rather than parts. I should pick whatever is the next easy part to make, finish the CAD tonight, and make it tomorrow.