Home>Projects>Completed>Barstool Racer
15 HP Electric Barstool Racer
Project by Corey, Project coverage by John
Corey likes to build fast and dangerous things to ride on. This is one of them. The total build time was fairly short (probably 2 days). Figuring out the wiring without proper diagrams however took a bit longer. The components used were as follows:
| Item: | Description: | Cost: |
| Motor | Briggs and Stratton E-tek (15 HP @ 48V) | $400 |
| Motor controller | 24V high amperage DC motor controller (E-bay) | $50 |
| Twist throttle | Electric scooter twist throttle (E-bay) | $15 |
| Brake master cylinder | Off a motorcyle, came w/ brake line (junk yard) | $10 |
| Barstool | Ikea or Target quality metal barstool | $40 |
| Handle bars | Off a bicycle | $ free |
| Tires/hubs/bearings (x4) | 5" diameter From Harbor Freight | $4 ea. |
| 12V car batteries (x4) | Standard car batteries (laying around our shop) | $ free |
| Wiring | 12 guage and 18 guage (from car audio store) | $10 |
| Sprockets | Used sprockets from one of our Baja cars | $ free |
| Brake caliper | Used brake caliper from one of our Baja cars | $ free |
| Brake disc | Used brake disc from Baja car | $ free |
| #40 chain | Used chain from Baja car | $ free |
| Contactor | DC Contactor (relay) used for motor on/off (E-bay) | $ 24 |
| On/Off Switch | Radio Shack toggle switch | $3 |
| Tie Rod ends (x4) | Standard 3/8" tie rod ends from McMasterCarr | $10 ea |
| Axle Material (x2) | 2' section of 1" steel rod | $5 ea |
| 1/2" x 2' steel tubing (x2) | Tubing used to make tie rods | $2 ea |
| 1" x 16' steel box tubing | Low grade steel box tubing | $1.50/ft |
| Misc. | Various fasteners, nuts, bearings, and materials | $15 |
Total: |
$629 |
Mechanical Construction:
The first step of this project was to mach up the location of all the parts. Once that was done, the box tubing frame was constructed. Box tubing was used because the frame was mostly right angles and the box tubing made welding easy (plus strength/torsion wasn't an issue). Once that was done, the barstool legs were attached to the frame by sliding into steel tubing acting as "seeves" and they were secured in place by a screw through each tube/leg. Next the motor was bolted on, making sure to slot the motor mount so that the motor could be moved up or down to tension the chain. The batteries were held in place using steel angle (L-brackets) on opposite corners of each battery. Their weight was enough to keep them from bouncing up and out of their positions. The steering column was a 3/4" diameter steel tube with a 3/4"-16 bolt welded to the bottom. The bolt threaded into a nut on the frame, allowing the steering to turn freely (although move 1/16" vertically per full rotation). Luckily, the vertical movement wasn't an issue since the steering would never be turned more than a few degrees in each direction. The rest of the construction should be pretty straight forward for anyone would be attempting to duplicate this project. Refer to pictures if you need to see more detail. The motor was geared way down to limit the barstool to a 15 mph top speed (which coincidentally provided way too much torque).
Electrical Construction:
The electronics side is fairly simple. The E-tek motors put out 15 HP when run off a 48V DC power supply. Fortunately for us, a 48V power supply wasn't readily available, so we went with a 24V supply, limiting our power output to about 7 HP. I say fortunately, because as I'll talk about later on, even 7 HP is too much for a barstool (without wheelie bars).
Since a 24V power supply was being used, the 4 batteries were wired as sets of two in parallel, giving an output of 24V with plenty of battery capacity (enough for over 30 minutes of driving on a full chage). A contactor/relay was placed between the motor and motor controller and wired to an on/off switch to prevent someone from accidentally hitting the throttle and sending the barstool through a wall.
The Barstool in Action:
The first time the barstool got running, Corey hit the throttle, the barstool did a wheelie, and Corey got thrown off. After that, we warned everyone to engage the throttle VERY slowly. Almost everyone who rode it still popped a wheelie the first time before realizing how much torque this motor puts out. With a center of gravity this high up, the barstool was very dangerous and should probably have only had 3 HP, or had wheelie bars attached. Even 15 mph was rediculously fast when you are sitting that high up off the ground on something that would tip easily if you took too sharp of a turn.
The best part of the barstool was the fact that it was electric, 100% silent, and could be ridden indoors. This thing was unbelievably fun once you realized how to handle it safely. Unfortunately, too many people hurt themselves riding it for their first time (Including someone putting a large hole in a wall inside of one of the academic buildings on campus and breaking their finger). Corey put the barstool up for sale on ebay and a police officer bought it from him with plans of turning it into a go-kart for his kids.
If you plan on building your own barstool, PLEASE be very careful. This project hurt the most people out of anything that Corey's ever built, and he builds some dangerous things.