Introduction: Office Chair Racer With Articulated Steering
Instructables is a great place to teach and be taught. Recently, I was asked to help build 10 billy carts for a youth group activity. I smiled when the text I received included a link to ScitechWA's original billy cart project. https://www.instructables.com/id/Build-a-Billy-Cart/. ScietechWA's instructable was a great reference while making this project.
This instructable is an entry in the REMIX contest. Check it out here. The main 'remix' here is that the steering is articulated, meaning the axles turn in opposite directions. This makes the turning radius tighter. It also uses an office chair instead of a plywood seat.
The biggest challenge was the number of carts that needed to be built. I was not so sure I would be able to buy all the parts I needed without a special order. Luckily, I was able to get everything here in town. The big win was the 10 office chairs from the county auction. Each one cost sixty cents!
Step 1: Materials and Tools
Here is what you'll for materials.
4, 10" Pneumatic tires from Harbor Freight Tools
2, 2x4's pine - body
6', Nylon Rope - steering ropes
1 section, 1" Electrical conduit - steering linkage
1 rod, 5/8"x8' Copper coated grounding rod - axles
4, 1/2" two hole strap - to hold the axles
1 roll, 3/4" vinyl tubing - to make up the gap between the axles and mounting straps
8, 2/1/2" wood screw
8, 1/5/8" wood screw
2, 3/8" Carriage bolt
2, 3/8" Nylon Lock Nut
2, 1/2" Fender washer
2, 3/8" washer
4, 3/16" Cotter pin
Here is what I used for tools:
Drill (for drilling and screwing)
1/1/4" spade bit
5/8" spade bit
Step 2: Axle Supports and Frame Rail
See the first picture for all the measurements. You have to make a total of 5 cuts from two 2x4's. Make sure to wear your safety glasses.
Step 3: Steering Stops
These are so important, I decided to make them their own step. Steering stops were never part of the plan but, we added them after the first test run. At high speeds, people tended to over-steer into turns. This was causing them to flip off the cart. Since teenagers were going to be doing this, they would likely be a little more aggressive in the turns.
I placed a clamp on my radial arm saw to hold the measurement of eight inches and set the angle at 13 degrees. Once I made my first cut, I flipped it over and cut it again. This gave me a pivot point centered at the end of the stop. These stops still allow them to lift a wheel off the ground but it's less likely to flip.
Step 4: Drill
See the first picture for the size and general locations for the holes. If you use an office chair you will have to adjust for what ever dimensions your chair brings.
It really helps to have a drill press. It also helps to clamp down the pieces while using the spade bits. If you don't have a drill press, I would screw the seat brace to the main rail and then drill the hole for the seat post. This should line up the holes between both pieces of wood better.
I placed the seat 12" from the rear edge of the main rail. This gives enough room for someone to jump on the back axle if they wanted to.
Step 5: Prep the Chair
The chair must be removed from the base. Wear safety glasses because you will be removing clips that can come flying off. To do this, start by taking off the clip from under the chair base. Next there is another clip you need to pry free to remove the piston from the main post. Once the piston is removed, cut the post down to 4/1/2". This is one of two anchor points for the chair.
Next, pry off the tension knob with a large wrench. This will take some elbow grease. Finally, remove the hand lever. To get this done I had to cut a plastic clip to allow it to come free. To access the plastic clip, I had to take the plastic cover off the bottom of the chair.
Step 6: Steering Linkage
Cut the conduit down to 43". To smash the ends down, I used a arbor press but you could use a hammer to do the same thing. Smash down two inches on both sides of the pole. Make sure the flat portions for the conduit are lined up with each other.
Drill a 3/16" hole at each end.
Step 7: Axles & Wheels
First I went to the metal supply section at the hardware store. They had metal rods likes this but only 4 or five of them. I needed 20! I ended up buying 8' copper coated grounding rods for $12.00. This was almost as must as individual metal bars but I could cut three axles from one rod.
I used a hack saw to cut these down to 30". Then I drilled 3/16" holes at each end and filed off any burs.
The tire were placed on the rods and cotter pins were put in place. The wheels had a little wobble to them but it wasn't so bad that I needed to find a spacer for the excess play.
Step 8: Assemble the Frame
The main frame rail rides on top of the axle supports. Install the bolts and washers as shown in the the picture. Tighten the bolts while still allowing the axles to move freely.
Step 9: Install the Seat Brace
Take the section of the chair post you cut off and use it to line up the seat post with the frame rail. Once both pieces are lined up, screw it together.
Step 10: Install the Wheels & Axles
Cut sections of vinyl tubing about one inch long. Then slit them open so they can be placed around the rod. Screw them into place with the 1/5/8" wood screws. Use the steering stops as jack stands while you do this.
Step 11: Install the Steering Linkage
Line up the axles with the frame rail so they are perpendicular. Place the steering linkage so you link each axle from opposite ends. Secure is with 1/5/8" wood screw.
Step 12: Add the Stops and Steering Ropes
Leave about 1/8" clearance between the main rail and stops. Clamp them down as you screw them to the axle support.
Cut 3 feet of rope and feed them through the holes at each end of the axle supports. Tie overhand knots to keep them from slipping back through. Knots also serve as handles for the rider.
Step 13: Install the Chair
Last but not least, place the chair into the two holes you drilled. Your racer now has a low-cost padded chair with a reclining back rest.
Thanks for reading.
Runner Up in the