Race day is fast approaching for my high school small engine class. They were tasked with converting push lawn mowers into go-karts and completing as many laps as they can in 30 minutes. Emphasis is not on speed but rather experimenting with build ideas, problem solving, and just get a wrench in hand. Right now our fastest kart and only race ready rig hits a whopping 13 mph.
More than likely most of the karts will break down, burn up, or fall apart before the 30 minutes are up. Again, I just want the kids to try mechanical ideas without the worry of getting in trouble for something breaking. No bad idea as long as there is safety consideration. To help with the mechanical triage the local hot rod club is volunteering to man our "Pit Row" so that as kids break down they have a several experienced mechanics on hand to quickly get them back on the track. We have invited the whole school, families, and community to come to our "Kart Show" in the morning where they kids can show off their rigs before the race. During the race we will have bleachers for the student body and causual public. For those wishing to donate to the program and our new Small Engine and Machining facility we will have a shaded VIP seating with shop swamp cooler right on the straight away. Next to the VIP seating there will be cookies and lemonade available to everyone at the cost of an open donation.
Anyways, here are some the rigs the kids have come up with...
The green rig is a rear pivot steer setup currently using the factory drive system. The rear pivot steer is a a single bolt with bracing in the chassis riding on a thrust bearing between the bracing and steering arm. They are using the 550 cord run through eye bolts to pull the steering arm in either direction. So far it works okay but today they learned that the bracket on their steering stem was not long enough so there wasn't enough pull length to steer sharp enough. They made a longer bracket and got that welded on. They also learned their weight is far enough back that they just spin tires intitially. They might try making rubber adapters for the plastic tires. Who knows but it'll be interesting. They are so close! I forgot to mention their steering is made mostly from scrap. The eyebolts and thrustwashers being the only new components. The rear wheels are original to the mower. The seat and steering wheel are from a rider that was stripped completely down for salvage parts.
The trike is running the front frame assembly off a bicycle that they made custom brackets to mount it up. The drive system is the auger gear box off a snowthrower. They are using an idler pulley on a swing arm as a tensioner clutch. We'be been trying to splice a belt up for them and are making progress. I ordered a belt for them as a backup because they are so close. They had orginally tried to use the snowthrower transaxle but discovered that it unfortunately had a stripped worm gear setup and we were unable to resource a replacement. The rear tires are from the snowthrower and have been welded to the the auger shafts. The overall pulley system is okay. It's a bit loose but considering the engine is running a bent crankso the drive pulley is a tad out of center we will take what we can get till it loses compression or seizes.
The last mower is using a deck from the 80's, engine and clutch from the 60's, a carb with modified intake manifold from the 90's, and an airbox from god knows what. The tires and wheels are from furniture dollies, the gears are from a bicycle, and the chain tensioner is a combination of bicycle derailer and a riding mower idler pulley. The throttle cable is off a rototiller I believe. The axle and steering are all build from scrap. It is our current top contender and is actually complete as of today. They have built a chain guard, kill switch system, and actually performed successful test runs.
All three of these mowers were non-running when they came in. The students had to first diagnose and repair the engine to ensure it would run. They then build the steering systems and then finished with drive systems. And all just in this semester with just an hour a day. They spent last sememster going through the book learning with me to prepare for this semester. This is our inaguaral class year and race so I'm sure it will have some hiccups but heck, I can't think of a high school in the country right now that has go kart race as the final grade.
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