Introduction: Custom Electric Trike - It's for the Dogs.
In a previous Instructable seen here, I described the construction of a $100 recumbent pedal trike I built for the purpose of taking my dog, Louie, out for nice long runs. I liked the pedal trike so much (as does Louie) I decided to add an electric motor, in part, to enhance the exercise program but mostly because it just sounded like a lot of fun.
This was my first EV venture so I knew very little about the various components necessary to create a DIY machine. I therefore opted for a parts kit to up my chances all the pieces and the electronics would match up properly. After much searching and comparison shopping, I ordered this kit from Kings Motor Bikes. (Photo 2)
The components include:
Currie 500 watt, 24 volt, 28 amp motor #XYD-6B w/ 11 tooth sprocket ($100 elsewhere on web)
Currie 30 amp controller #XK-022C ($57 elsewhere)
Currie 24 volt Sla twist throttle ($23 elsewhere)
Currie 24v/10 Ah/SLA battery pack with soft case and charging port ($106 elsewhere)
Currie 24 volt charger ($32 elsewhere)
Artek brake lever/cable/switch ($15 elsewhere)
E-zip power switch ($6 elsewhere)
Wiring harness and all snap together plug ends (not found as a unit elsewhere)
Motor mount - not used
Purchased individually the parts would have been $339 plus shipping for a number of the items. The Kings Motor Bikes price was $199 shipped to the door. Everything in the kit is well labeled and is nearly mistake proof to insure a safe electrical set up. No two plug ends are the same so it is impossible to plug the wrong component into the wrong circuit. I would highly recommend this kit for novices like myself. Obviously, if you are experienced you could no doubt find some different brands and some special deals which might save you some money or give you more power and distance.
Materials not in the kit:
3/16" steel plate 6" x 12" for motor mount - $4.00 (local supplier)
Assorted nuts and bolts - $3.00 (home depot)
#25 chain - $12.29 (for 10' of chain, used only 3 feet) (Amazon)
#25 to #60 chain breaker - $11.43 (Amazon)
90 tooth Schwinn/Ezip sprocket - $31.14 (Wild Scooter Parts)
11 tooth Schwinn sprocket/coaster hub - (parts and cost included in original trike construction - see link above)
Total cost for the electrical trike conversion - $260
I would consider this project to be moderately difficult because it requires some cutting and drilling of metal parts. The actual electrical connections are quite easy as is the installation of the throttle and brake lever The chain breaker is included in the project cost since it makes the job of creating the correct chain length relatively easy and I highly recommend buying one.
Step 1: Assembling the 90 Tooth Sprocket
My target speed was somewhere between 15-20 mph. The motor comes equipped with an installed 11 tooth sprocket. So a 90 tooth sprocket, a 20" wheel and a motor rpm of 2600 would result in a top speed of just under 19 mph. Plenty fast for my purposes. This 90 tooth, #25, Schwinn sprocket is also used on Ezip scooters. (Photo 1)
One of the 20" flea market bikes I purchased for the original trike build was a Schwinn coaster bike. I am keeping the pedals on the front wheel of the trike for dual power and I liked the idea of using this coaster hub on one of the rear wheels, driven by the electric motor. This would allow the electric driven wheel to “free wheel” without any back friction from the motor whenever I used the pedals. If you are not familiar with coaster bike hubs and brakes, here is a great resource
To allow the coaster mechanism to operate normally, the 90 tooth sprocket is bolted directly to the sprocket of the coaster hub. Unfortunately, the 90 tooth sprocket comes with a threaded collar. (Photo 2) This collar had to be cut off with an angle grinder and then filed smooth around the inner diameter. (Photo 3)
The coaster hub includes a sprocket and drive gear which are attached to each other with a snap ring. (Photo 4) The sprocket and drive gear can be separated by removing the snap ring. Note the three tabs on the inner diameter of the sprocket. (Photo 5) These tabs intersect with the drive gear to turn the wheel forward.
In a stroke of good luck, once the collar was cut off of the 90 tooth sprocket, the sprocket fit perfectly around the outer diameter of the drive gear. (Photo 6 and 7) To attach the hub sprocket to the 90 tooth sprocket I first tried drilling holes through the hub sprocket. I quickly discovered, however, that the sprocket is hardened steel and I could not make any headway even using my drill press. As an alternative I drilled four holes in the 90 tooth sprocket (which isn’t hardened steel) equally spaced around the hub sprocket with each hole at the base of a cog. To make sure the two sprockets are perfectly aligned for drilling the holes you can insert the drive gear through both center holes of the two sprockets to hold them in place. (Photo 8)
Assemble the hub sprocket and drive gear and then bolt the hub sprocket to the 90 tooth sprocket. (Photo 9) The sprocket assembly can then be mounted on the 20" wheel. (Photo 10) There are internal parts in a coaster hub and naturally I found a way to drop and misplace them. The “troubleshooters” link shown above can be a real life saver showing exactly how everything has to go back together.
Step 2: Motor Mount
Drill a 1" hole centered on the 6"x12" steel plate. Allow about ½" at the top of the plate beyond the top of the motor. The 1" hole will allow you to lay the motor flat on the steel plate with the 11 tooth sprocket protruding through the hole. (Photo 1) Center the sprocket in the hole and mark the three bolt holes. Be sure to position the motor so that the electrical wiring will be in the best position for your particular set up. I pointed mine straight down so I could run the wire under the trike’s frame. (Photo 2) Test fit the motor in the mount to insure that all three bolts will line up properly. (Photo 3)
To make the motor mount adjustable, which will allow you to take the slack out of the chain, create two slots where the mounting plate will be bolted to your frame. I’m using 5/16" attachment bolts so I drilled drill 4 holes slightly larger than the 5/16" bolt size. Each hole will serve as one end of each slot. (Photo 4) Cut away the material between the holes to create the sliding slots. (Photo 5)
Bolt the mounting plate to the frame. Note the use of extra large washers to prevent any collapse of the square tubing when the motor mount bolts are torqued down tight. (Photo 6 and 7) Set the motor mount exactly at the mid point of the slots and then install the chain to measure for length. Draw it tight and then mark the link where you want to install the master link. You can break and assemble the chain off the trike if you find that easier than putting in the master with the chain on the sprockets. If you pre-assemble the chain off the trike, you will need to remove the wheel and drape the chain over the 90 tooth sprocket and then reinstall the wheel. Slide the motor mount all the way toward the wheel/sprocket and the chain should easily loop over both sprockets. Then slide the mount in the opposite direction until the chain is tight. Tighten the bolts. (Photo 8)
Step 3: Battery Tray
The battery pack can be held in place any number of ways. I happened to have a 19 gauge piece of sheet metal in the scrap pile from an old gas range the was already partially bent in the shape I needed for a tray. The piece was cut and pounded into shape with a large hammer. (Photo 1) Just make sure you don’t leave any sharp edges. The 24 volt battery pack fits snugggly inside the tray. (Photo 2) I used a small nylon strap (not shown) to insure the battery remains secure. The tray is attached to the frame with self tapping sheet metal screws. The tray is tucked away behind the seat. (Photo 3)
Two of the electrical components, the power switch and the charging port, need to be housed in a secure yet easily accessible spot. I used another piece of the same 19 gauge sheet metal I had to make a small “dashboard” which fits under the seat but within easy reach. The sheet metal is cut out to accommodate the switch and the port. (Photo 4) The dash is screwed to the under side of the seat frame. In the photo (Photo 5) the battery charger is shown hooked to the port. The on-off power switch is shown on the left.
Step 4: Throttle and Brake Lever
The throttle and brake lever are installed on the handle bars in typical fashion. All wiring should be firmly attached to the frame with zip ties of some other method to prevent any possible snagging of the wires.
Step 5: Ready to Roll
The electric trike is completed and on the street. The motor has plenty of power to take me (160 lbs) from a dead stop to full speed without any use of the pedals. If I keep speeds reasonable and don’t do a lot of hill climbing, I can travel an hour or more on a charge. At constant full throttle, that time is cut in half. There is almost no chain noise and it is quite peaceful to ride along in the quiet. The cost of building the original 6-speed pedal trike, as shown here, was $100. The electric motor upgrade added $260. So the total cost for this dual powered machine was $360. And so far my dog thinks it was a great investment. I’m so happy with the final results that I’m already thinking about building a bigger/better trike for commuting and running errands around town.