Mac Sports Classic Wagon Replacement Wheel

My Mac Sports classic folding wagon has been through a lot, and used quite hard. It had a wheel that was threatening to come apart, so instead of trashing the whole wagon I made a better wheel for my old friend.

The old wheel used a simple bushing over a riveted in axle. I decided to use two 608 bearings instead. Cutting the axle will be the hardest and most dangerous part, do not attempt if you can’t do so safely.

Tire is 95A TPU, holding up great so far. It is as wide as possible for easy rolling on sand, while still fitting inside the two arms of the wheel support.

I tried a lot of different wheel configurations, landing on a simple design that uses the least amount of plastic for the most strength and easiest print, as well as easy assembly. It is lighter than the stock wheel as well, and future tire changes will be easy.

Hardware you’ll need, per wheel:

• 2x 608 bearings, available cheap on Ali or Amazon
• 4x 1-¾” length, ¼-20 TPI round head bolts, flat head or Phillips or whatever (mine were combo). Longer could interfere with the wheel supports, shorter will not be long enough to reach the nut. 
• 1x 3” length, ¼-20 TPI hex head bot, for the axle
• 5x ¼-20 TPI nylon lock nuts
• 2x ¼ washers

I used PETG for the back for cost and ASA for the front for the mechanical properties, but honestly you could probably do the front and back with PEGT and be fine. 

Print the bushing vertical with a brim, PETG or other stronger material, make sure your settings are correct as this is the most tolerance sensitive part. 

Print the wheel with TPU, your choice of softness and infill. I used 95a, 6 walls top bottom and sides, and 20% cubic infill. It rolls pretty much the same as the stock tires so far. When you print, use a brim, and print with supports for the overhang on the inside just to keep it from curling up. I failed 2 wheels for curling without supports.

Assembly:

1. Press-fit the 608 bearings in the wheel hubs, one each front and back. May need to push them against a table or something, they should be quite snug.
2. Place the tire over one side of the wheel from the inside, so the notch on the inside of the tire fits in the groove. It should be snug, may need you to stretch the tire a bit.
3. Place the other side of the wheel inside the tire, line up the holes, and secure with 4x nylon lock nuts in the hexagonal pockets and the bolts in the circular pockets
4. Push the axle bushing through the bearings. It should be snug, not fall out, and when you turn the inside of one bearing the other should turn. It can require some force to turn, thats ok.
5. Put on safely glasses and gloves at minimum. Cut your old axle carefully. I used a dremel with a cutting disk. Metal will be hot and sharp, use PPE. Remove axle and old wheel, discard
6. Place a washer on top of each wheel bearing, and put the wheel in between the support arms where the old wheel was. The washers should be INSIDE the arms against the wheel bearing.
7. Push the 3in ¼-20 bolt through. it can take some force, a light tapping with a hammer can help. Secure with nylon lock nut, only moderately tight. If you crank down the axle you risk crushing the bushing and bearings
8. When rolling, the axle should stay stationary, and the wheel/tire shouldn’t touch the support arms anywhere. If like me your wagon is a bit beat up, you may have to gently push on the arms to bend them back into the proper place.