You thought you had this great idea and that idea was to use the riding lawnmower or the old John Deere tractor sitting in the backyard and make a go kart out of it. But that idea seemed to fade as you started trying to use various components off of the riding long mower and found that they were really not working out very well or it was taking a lot of work to get them to actually be usable on a go kart.
The Big Problem
One of the biggest problems you run into is actually using the wheels that come off of a lawn tractor and adapting them so they will mate with a go kart axel.
There are two problems you’ll run into when you are trying to adapt a tractor wheel onto a go kart, they are:
1. The rear hub that comes with the tractor wheel is splined and does not make with any standard axle stock
2. The rear rim and hub are one unit and the inside diameter of the hub is 3/4 inch
1. Splined Rim/Hub
The first rim/tire we ran into actually is quite serious and will require scrapping the hubs that come with the tractor. A special hub will need to be developed that will mate with the tractor bolt pattern. You will have to develop a plate based off of the old hub and then weld the plate onto a hub that you have developed or stock that fits on the shaft.
Keeping the Wheel On
Particular attention will be needed to make sure that the hub that you have developed will not come off of the shaft. This can be accomplished in a couple of ways. First of all it must be understood that the torque load from the axle to the hub needs to be transferred through a key way.
Transfer Torque Properly
Again all torque loading needs to be transferred through a key way. The reason for this is that the key way has a larger surface cross-sectional area to transfer the load. Anything smaller than a key way will not be able to handle the load and will shear off.
2. 3/4 Inch Diameter Hub (Not the 1 incher you are looking for)
The second rim/hub problem actually is quite simple to solve but requires a little welding. First of all the three-quarter inch diameter hub fits perfectly over three-quarter inch diameter shafting. Typical live one-inch axles, have reduced threaded stock that is designed to hold aluminum hubs onto the shaft. However, the length of the three-quarter inch stock is not long enough to stick out the end of the rim/hub from the tractor. Additionally, there is nothing to grab the rim/hub with.
The solution is to make the key way part of the rim/hub. The rim/hub is piloted on the three-quarter inch axle shaft stub. The one-inch keyed hub is placed onto the one-inch axle shaft. Then the hub is welded to the rim/hub. The torque load is taken by the key way in the welded on hub.
However, the rim/hub still needs one more thing to keep in place otherwise it will slip off the shaft. To keep the rim/hub from falling off of the shaft a 1/4 inch diameter hole can be trailed through the side of the welded on hub into the one-inch shaft. The ¼-20 grade 5 bolt can then be inserted and held in place using a nut.
This will effectively do two things: first the key way will take the torque load, secondly the bolt will keep the axle and the rim/hub together. The bolt will not take any torque load but will keep the wheel from coming off of the axle. This is equivalent to using a snap ring.
The same method can be used for keeping the first hub on the shaft. The preferred method however, especially if you’re developing your own shaft, is to hold the hub on with some sort of nut or bolt that threads onto the end of the shaft.
3. Live Axel Hub
One thing that we’ve not talked about and that is the method of using the three-quarter inch rims/hub as a spinning bearing. In other words, the rim/hub is spinning around the three-quarter inch shaft. This is only applicable if you have a welded on or a fixed shaft onto your go kart.
Typically, a long enough 3/4 inch bolt is not going to be available from the hardware store. So what will need to be purchased instead is some three-quarter inch shafting. The conundrum comes in how to retain the wheel and place?
To retain the wheel in place the shafting should be drilled crosswise and then a bolt can be put in place to retain the wheel. There is one serious issue to be aware of however, and that is the wheel will be spinning and can rub against the bolt when it is spinning. There’s rubbing action acts like a saw or a mail or grinder, and will cause the bolt to be sawed off or ground away completely. The downside to this is that the wheel will fall off a go kart.
So, to keep the bolt from being ground away put a simple washer between the bolt and the wheel hub. The rubbing action will be put against the washer and not against the bolt. Obviously, a generous amount of grease will aid in keeping all systems from wearing out. And honestly again the side benefit being reduced friction.
So To Recap:
First,when using a splined axle hub you will have to develop your own new axle hub that will mate onto a live-axel system.
Secondlyif you have a tractor hub that has a three-quarter inch diameter hole that can be adapted to fit onto a live- axel using a welded on hub. A key way transfers the torque and a bolt keeps the hub from falling off the axle.
Thirdly, if you are using a solid axle you’ll need to make sure that you have ample amount shafting and that the axle is held in place using a cross bolt and washer. Ample grease will be required to make this solid axle system to work properly and last.