A truck you can build, fix and fuel yourself.
Drumlin is an open-source electric pickup and a set of farm tractors for a home shop. Flat steel panels you cut and bend yourself, a steel ladder frame, a wooden bed you replace one board at a time — and battery boxes that ride in the truck, the tractor or the house.
Few parts, standard parts, fixed by the owner
The trucks people keep running for thirty years — the old Hilux, the T100, the 70-series Land Cruiser — have a ladder frame, solid axles and leaf springs, and nothing a shop can’t reach. Drumlin starts there and keeps the spirit of the Model T and the Ford 8N: as few parts as it can have, and all of them repairable with hand tools.
It is built more like a kit airplane than a modern vehicle. Every part that can be replaced on its own has a part number and a drawing with a revision letter. Every truck keeps a logbook from the first receipt. The dash is dedicated gauges and switches, not a screen: speed, charge on a fuel needle, temperatures, and one lamp that means stop and look.
The truck
An extended cab on an eight-foot wooden flatbed with stake sides. The body is flat galvanized steel panels on a steel cab frame, folded in a sheet-metal brake and bolted on, so a damaged panel is cut again from its drawing.
Two electric motors, one for each axle, make it four-wheel drive with no transfer case — and if one drive fails, the other brings it home. Each motor has its own battery pack, like an old pickup’s two fuel tanks, with a switch on the dash to show either one.
Each motor rides on its own axle, above the differential — one under the hood, one under a hatch in the deck — so it is serviced from above and sits out of the road spray. A small two-speed gearbox at the axle's nose drives it: high range for the road, low range for a trailer or the field. No driveshaft.
The four battery boxes ride in two bays between the frame rails, one behind the front wheels and one ahead of the rear, and come out from underneath on a lift trolley.
Turn the truck in 3D — steer it to full lock, twist the axles, and lift the body off to see the battery bay.
- Wheelbase
- 3.7 m
- Length
- 5.75 m
- Drive
- Two motors, one on each axle, two-speed, four-wheel drive
- Road speed
- 65–70 mph
- Battery
- Four 14.3 kWh boxes, about 57 kWh
- Frame
- 2 × 8 in steel tube, 3/16 in wall
- Axles
- Solid, on leaf springs
- Rated gross weight
- 3,900 kg (8,600 lb)
- Payload
- About 1,250–1,350 kg (estimate)
One battery box, three places to be
The Drumlin cell box is sixteen lithium iron phosphate cells in a stainless case: 51.2 volts, 14.3 kilowatt-hours, about 130 kilograms. There is no electronics inside it — the battery management lives in whatever it plugs into, so the box itself is cells, copper, a fuse and a connector.
The same box rides in the truck, sits in a leg of the tractor, or stands on a rack in the house as backup and solar storage. A lift trolley moves it: roll it under, crank it up until the guides catch, and four latches close with a flag you can see.
Watch a box dock — step through the lift, or hide the case to see the cells inside.
- Cells
- 16 × LiFePO4, 280 Ah
- Energy
- 14.3 kWh, 51.2 V
- Mass
- About 130 kg — rolled, never lifted
- Inside
- Cells, copper, one fuse, heaters, a sealed plug
- Docks
- Upward, on guide pins, held by four latches
- Cold
- Will not charge below freezing; heaters bring it up first
The tractors
The first tractor is a straddler for strawberries: a bridge frame that stands over two rows at once, eighteen inches clear of the plants, on two legs that run in the alleys. One battery box rides low in each leg, which is what keeps a machine eight feet wide this steady. It steers like a zero-turn mower and carries a 300-gallon tank and a 32-foot boom.
Turn the straddler in 3D — swing the casters, unfold the 32 foot boom, and lift the tank off to see the frame and the battery boxes.
The track is a setting, not a fixture: change the bridge and the same machine straddles one wide bed or two narrow rows. The second tractor is a narrow electric tug, under 49 inches wide, that tows a small sprayer between the raspberry rows — sharing the straddler's pump and controls on a tank sized to the patch. A 600-gallon nurse trailer carries clean water to the field; the sprayer fills itself from it, so the trailer needs no pump and no power.
- Track
- 96 in, two rows on 48 in centres
- Clearance
- 18 in over the crop
- Spraying
- 5 mph, 50–100 gal per acre, 32 ft boom
- Per charge
- About 60 acres (estimate)
- Road
- Up to 25 km/h, empty
Energy independence, a box at a time
Every box bought for a machine is also storage for the house, and every box on the house rack is range for a machine. So independence grows slowly: a box and a few panels at a time, each step paying for itself before the next.
It is honest about winter. A kilowatt of panels here makes about a third as much in winter as in summer, and a battery holds hours, not seasons. Sun and batteries carry the summer and the daily loads — pumping, spraying, driving, the house’s evenings and outages. Winter heat stays with wood, stored heat and a heat pump, with the grid as backup.
Eau Claire, Wisconsin, seasonal averages (profilesolar.com). Filling one battery box a day takes about 1.9 kW of panels in summer and 5.6 kW in winter.
Show as a table
| Season | kWh per kW per day |
|---|---|
| Winter | 2.32 |
| Spring | 5.14 |
| Summer | 6.64 |
| Autumn | 3.34 |
- MeasureWhat the pump, the shop, the house and the machines actually use.
- A house batteryOne or two boxes on a rack, with an inverter: backup the day it goes in.
- First panelsSized to what gets used during the day, not to what can be sold back.
- The truckFour boxes that are house storage whenever it is parked.
- The farm pumpPanels on the well’s own meter — the biggest summer load.
- The tractorsSpraying all summer on the sun.
- HeatWood, stored heat, a heat pump — to cut propane.
How it’s built — and what isn’t proven yet
Every part is modelled as a solid and checked by machine before anyone trusts it: no two parts may pass through each other at any point of their motion, every contact has to seat, and every number on a page comes from the model itself. The truck’s layout has been checked through full steering lock and full axle twist; the frame, the battery box and the lift trolley each pass on their own.
Every safety system has a named standard before a drawing is trusted — the federal brake, roof, belt and high-voltage rules, and Wisconsin’s own inspection for a homemade vehicle — and where a standard cannot be met in a home shop, the plans say so.
Nothing here is released. These are concept models and hand calculations. No drawing has been approved for building, nothing has been weighed, and no part has been tested. A model that looks right is not a truck that stops. The plans will be published under an open licence once they are ready to build from.
Decisions so far
- The project opens: a modern Hilux in the spirit of a Model T. Named Drumlin, after the glacial hills of Wisconsin.
- Flat steel panels, a steel ladder frame, a wooden bed. Electric first.
- Drumlin cell boxes: 51.2 V, no electronics inside, moved on a trolley. The first tractor straddles two strawberry rows.
- As few electronics as possible: dedicated gauges and switches. Built more like an airplane than a modern vehicle.
- Two motors, one per axle. The battery boxes ride between the frame rails and swap from below. An eight-foot wooden flatbed.
- Two independent drives, like a dual-tank pickup. The straddler sprays; a nurse trailer brings the water.
- The frame for all of it: energy independence, built up a battery box and a few panels at a time.