Building an electric vehicle can be easy. We wanted to figure out how to build one from scratch, and we also wanted to build one that was fun to ride. The goal of our project was to make available the plans to build a low-speed, leaning, electric trike that could be built in a modestly stocked workshop from readily available parts
First Night Austin gave us a grant to build a fleet of these vehicles to include in their Grand Procession - a parade that is part of the downtown family art festival in Austin, Texas. Our piece also included a dinosaur-like gasoline powered SUV art car which our cavemen and trike riders would hunt down as part of the festivities.
Find out more about the makers - The Caveman Collective
Step 1: Parts and Tools
Tools you will need:
A jigsaw with a wood cutting blade.
A screw gun.
Various drill bits.
A socket for tightening lag screws.
A few 6 inch C-clamps for clamping and gluing.
Wire-cutters and crimpers.
A volt meter for sanity testing things.
Hacksaw with metal cutting blade.
Sandpaper for smoothing wood.
Large crescent wrench.
Wood glue - Elmer's wood glue or Gorilla glue work fine
Half inch furniture grade plywood 2'x4' sheet
Wood varnish / paint to seal your wooden frame
3" Quarter inch lag screws
1.25" wood screws
2.5" wood screws
The front end of a kid's bike with a 20" wheel.
6"x2" eighth inch steel bar.
A two motor electric wheelchair. (Our favorite is the Quickie P300 with large wheels)
Metal swivel - we used the 300lb caster swivel from Harbor Freight as we had some lying around.
We ate our own dog food in terms of finding parts - we acquired the parts to make 5 trikes in a few weeks with a little scouring.
Step 2: Cut Out the Frame Pieces and Supports
Using a template and a jigsaw, cut out the pieces for the frame from the plywood. The templates will be provided in a pdf to be uploaded soon.
Use a jigsaw to cut out the pieces.
Sand the edges to remove the splinters.
Now make two sets of pieces for the front and rear mounts from the 2"x4" and 2"x6"s.
The front mount is made of two 8" pieces of 2"x4" glued together and then cut to be 2.5" wide. The top and bottom are cut so that they fit in between the two frame sides.
The rear mount is made of two 5.25" pieces of 2"x6" glued together.
Step 3: Make the Fork Mount
To make the steering mount, simply rip one from a kid's bicycle.
At every pawn shop I visited looking for these, and every Goodwill thrift store, there were several to choose from, all under $20. Since we only need the front wheel, and the brakes and gears can be discarded, you could get one for considerably less.
The only requirement is that the front wheel tire is 20". Suspension is not preferred, and there is no need for a front brake.
Use a crescent wrench to undo the bearings and remove the front forks and bearings from the frame. Then we need to cut the frame. The geometry for the front end requires the frame tubes to be cut parallel to the headset. Use a hacksaw or grinder to make a straight cut - this needs to be flat so that it can be attached to the metal bar. Place the cut tubes on the plate to ensure a flat mount. Sand or grind the bicycle paint off around the cut.
Cut a 5" part of 2" metal bar to make a plate with which to attach to the frame as shown in the picture. At this point, position the headset on the plate, and mark holes for four or six screws around the cut-off tubes. Drill holes for screws and two lag screws.
Now weld the frame tubes to the plate - take care not to burn through the flimsy tube metal as you go. Paint the mount and tubes and set aside for later.
Step 4: Assemble the Frame - Overview
The frame is essentially a plywood box - it suspends the rider's weight elegantly between the front wheel head set and the pivot. We've tried out different steering geometries and rakes, and the dimensions we ended up with seemed best for our riders - ranging between 5' and 6'2" tall adults.
The front is narrower than the back - the head set mounting plate is 2.5" wide, whereas the mounting plate for the back pivot is 5.25" wide. Bear this in mind when putting the box together - right angles are few and far between. We typically held everything in place with screws to make sure a good fit was achieved, and then went back and glued things later.
Unless otherwise specified, we drilled a guide hole for each of the lag screws or wood screws to their entire depth. This was especially important when screwing into the edge of the laminated wood to avoid splitting.
Step 5: Assemble the Frame: 1
Lay out the frame left and right sides.
On one side, lightly screw the head set mounting block so that it is flush with the front edge of the side.
The swivel mount plate will need to be vertical to keep the frame leaning neutral. This is achieved by ensuring the swivel mount wood is perpendicular to the bottom of the frame sides - mark a line at right angles to the frame bottom on each side, one half inch from the lower rear corner.
Step 6: Assemble the Frame 2
Now that the frame is true, add the bottom plate to add rigidity. Then add the seat, the seat back, and the final seat prop to finish it off.
Step 7: Drill the Swivel Plate Holes
Hold the plate of the swivel against the lower edge of the swivel plate mount and mark the four mounting holes. Drill four holes for the lag screws which will hold the swivel plate in place.
Drill holes for two lag screws in each side of the steel swivel. This will attach the swivel to the drive unit. Do not mount the swivel at this stage.
Step 8: Build the Power Unit
We spent a while experimenting with different solutions to power the trikes. Options we tried:
1. 600W scooter motors + 40A controller + throttle - around $140. Building a gearbox would have been expensive, and we looked at lawnmower drives but these proved too flimsy.
2. Electric vehicle transaxle - $220 + motor + controller + throttle. Sturdy but out of budget
3. Three wheel electric scooter - $60 for entire unit (used) - single 600W motor and transaxle. We built a running prototype for this but it proved slow and underpowered.
4. Electric wheelchairs - this is what gave us the best ratio of speed, power and price.
First, get your hands on an electric wheelchair - we found several sources - wanted ads on craigslist and searching under "battle bot motor" on eBay. We succeeded in finding five that met our requirements:
-two matched motors and gearboxes
-24V battery supply
Each model was different, but they are were all built into heavy duty steel frames. Some had suspension.
After removing all of the seating, leg supports and arm rests, cut some of the unnecessary steel off and find a place to mount the swivel.
Mount the swivel fork onto two 2"x4" studs with a small piece of 3/16" plywood on each side. Attach these studs to the center of the drive unit, running front-to-back, in between the batteries. The studs need to be mounted so that the bottom of the swivel is 6" from the ground when the drive unit is horizontal. The drive units generally run faster forward than backwards, so take care to position the swivel at the front of the drive unit.
Step 9: Assemble the Frame and Power Unit
Now that the swivel is mounted to the back, hold the swivel against the mounting plate at the back of the frame and tighten the four lag screws into the pre-drilled holes.
It is simpler to attach this last, rather than attaching the swivel forks onto the 2"x4"s last.
Step 10: Attach the Head Set and Front Forks
Line up the head set plate on the wooden mount on the frame so that it will be vertical when the frame is upright. Mark six holes in the frame front head set mount. Drill holes for two lag screws and four regular screws in the mount. Attach the head set to the mount.
Re-assemble the bearings and bike forks into the head set.
Step 11: Mount the Throttle
Run the wire from the joystick to the controller / motor inside the frame. Attach the joystick to the bicycle handlebars using zip-ties, screws and ingenuity.
Step 12: Add Footpegs
Figure out a comfortable position for footpegs. Use 2"x2"s or unused parts of the donor wheelchair. Footpeg position should allow both leaning of the front frame and turning of the front wheel.