When we last saw our action hero he had set up the frame, king pins (spindles) and mounted the upper and lower control arms in place. The plans called for building our own 16″ wheels out of plywood planks and mounting bicycle tires onto them. The end result would look really nice and definitely keep the similarities of the wheels of Bugatti in it’s day, but to put it lightly, what a pain! Not to mention I would suspect they would add a lot of weight to the kart.
As with the MG kart project, I too was going to use some bicycle wheels. In that case he used four front bicycle wheels. As luck would have it my oldest son recently grew out of a bike, a Spiderman bike to be precise, that had 16″ wheels. Perfect. I now had half of the wheels I needed. Now to find two more, or rather two more that matched. You see these weren’t simply your basic chrome spoked wheels, these were the masked super hero special wheels. These had red spokes and a black rim so I couldn’t pick up just any set of wheels, that would be blasphemy!
I tried turning to friends and family to see if by chance anyone had the same bike sitting around. You’d think my chances were slim to none, but I just happen to know that this bike was available at Costco a few years back, and I also know that Santa shops there on occasion.
The responses ranged from “No, but I have a Barbie bike you can have!” to “I have wheels but they are purple, they’re yours if you want to come get ’em.” Purple wheels, next to my existing Spiderman wheels!? That would be perfect…if I were making a stage prop for an episode of HR Puff N Stuff.
I turned my attention to the net, specifically Craigslist. I found three bikes for sale right off the bat. In fact I came across one for a mere $5.00. Since it was located a couple hours away, I asked a friend who lived nearby to go pick it up. For only $5.00 I now had an exact duplicate of our Spiderman bike. To add a bit of high tech mystery to this project we could refer to it as a clone I suppose. I told my wife about the good fortune. She seemed genuinely happy, but I suspect it was do more to the selling price rather than the find. “What are you going to do with this when you’re done?” she asked. “Getting it finished isn’t the point, it’s the journey much more than the destination!” I said. Getting all deep and philosophical I figure would be better than a simple “Who cares, it will be cool!“.
Next I started to disassemble the bikes. The boys saw this and went ballistic,”Dad! I wanted to ride that!” I diffused the situation by saying I was only borrowing the wheels (not to mention the chain, and sprocket). I replied with “Don’t worry, if you want to ride your old bike again we can just put take them off your go kart, and put them back on your bike.” That’s what I said, but what I was thinking was more like “This go kart will be so cool you’ll forget your Spiderman bike ever existed!“. Well that settled that.
I wanted to go with bicycle wheels for a number of reasons; simplicity, availability, leverage of using the coaster brake, and the sprocket. I’ll get to the sprocket later. For now let’s look at exactly what it’s going to take to use bike wheels since it’s not as straightforward as one would hope.
Back over on the kart, I started mounting the front wheels. I had previously drilled the front spindle holes to accommodate the axles.
I went to put the first wheel in place only to discover that the axle wasn’t quite long enough to go through the spindle, through the other side and still have room for a lock nut and washer on the other side. I suppose I could replace the axle with simply a longer bolt right? Theoretically this would work just fine, but I wouldn’t be able to use the bearing retainer nuts which are slightly rounded specifically to hold the bearings in place. This would work if I could find a 5″-6″ 8mmX105 axle which as it turns out isn’t as easy as you would hope. I hit the hardware stores nearby and had no luck. Thank goodness the US completely adopted the metric system as it has.
On closer inspection it wasn’t that the axle wasn’t long enough, it was actually plenty long, it was that the wheel needed to be shifted in one direction a half inch or so. Easy right? Simply thread the bolts further in on one side, and further out on the other, and more of the axle would be available to go through the spindle. Not so fast.
It turns out that the axles for the front wheels are not threaded all the way across, but have approximately 2″ in the middle without threads. This means that if you wanted to shift the position one way or the other you can’t go very far. My solution? Simply take an 8mm die and extend the threads further down the axle. Run the die onto one end (doesn’t really matter which) of the axle, and go all the way down into the center. This can be quite a pain, but by moving back and forth slowly, you can add a few more threads which is all you’ll need. Occasionally spray some WD40 (or similar) lubricant and stop every so often. The die and threads will be extremely hot and can easily snap so take your time.
Eventually you’ll have enough space to offset the wheel once the axle is placed back into it. You will want to do this for both of the front wheels. The more space you can get the better, so it will allow you to comfortably place a lock washer and nut to attach each wheel onto the spindle.
Once I added enough new threads to both axles I inserted them back into the wheels. I then placed both wheels into the spindles and sat back happy with the results, for the most part. I soon realized that that since the plans call for creating custom wheels, the position of the spindles is ideally suited to those custom wheels. And not so ideal for my wheels.
In our case the wheel doesn’t quite spin freely as the spokes, ever so slightly, want to hit the very edge of the control arms. Not so much that a rough file and some 80 grit sand paper couldn’t solve it. Now we’ve got the front wheels more or less mounted.
Now let’s focus on the back wheels. As is often the case the brakes are often an afterthought with homemade, wooden, go karts. I know back when I was a kid the one we rode around on did in fact have brakes, they just happened to be attached to our feet and said “Chuck Taylor” on the side.
Since for every action there is typically a reaction (i.e., child jumping on couch results in emergency room trip…don’t ask me how I know this) I think brakes are pretty important. If for no other reason that you can make really cool skid marks on the sidewalks.
One of the goals with using the wheels from a bicycle is that I wanted to leverage the coaster brake assembly. I wanted to have a means for the rider to push down on a pedal, or in some other way, cause the coaster brake to engage. At the same time I wanted to be able to use the existing sprocket on the rear wheel to provide movement. At the moment I won’t be using a motor, but if I could somehow setup a chain/pedal drive perhaps I could use the rear sprocket to move the kart, but also allow the driver to pedal backwards and engage the brake. Easy as cake right? Sort of, but I guess it depends on what kind of cake you’re talking about.
If you look at any typical bicycle rear wheel (one with a coaster brake) you have the sprocket mounted on the right side, and on the left you have the lock mechanism for the coaster brake. This is typically mounted to the frame and when the user hits the brakes (pedals backwards) this prevents the brake mechanism from rotating and the brakes engage inside of the rim. Since I’m not mounting my wheels on two sides, like a bicycle, how would I mount this lock piece?
I took a break to sit on the front porch and enjoy an Otter Pop (an orange flavored Otter Pop to be specific) with the boys and think about this for a bit. If I could put it on the same side as the sprocket, and have that sprocket side closest to the kart frame, that would be great I thought. I asked the boys what they thought and they agreed. I appreciated their feedback, even though I knew very well it was the Otter Pops talking. They then asked if they could have another one. “No, you can’t have another one.” I said. I think they were expecting somesort of kickback for agreeing with me. At any rate, let’s put my theory to the test.
If I take the rear wheel of the bicycle, and simply place it at the left rear of the kart, I have my sprocket closest to the frame.
Reaching back to my Otter Pop Epiphany I removed the coaster brake arm and then looked to place it on the same side as the sprocket.
Not surprisingly it didn’t fit. There is a nut on this side, as there is on the other, that is squared on two sides. The only thing is that the nut on this side is slightly larger preventing the arm from sliding over it. Meet my little friend the file.
I took the retaining arm and filed about 1/16″ of an inch from the top and bottom of the hole thereby allowing it to slip over this larger nut. I then put the nut back over the axle to hold it in place and voila. I now had my “drive wheel” with a brake system ready to use.
At this point we have our front wheels in place, and we have the solution for the left rear (by far the more difficult of the two), solved for the moment at least. For the right rear wheel we also wanted to have the sprocket closest to the frame. We slid off the coaster brake retainer, as we had on the other wheel, only in this case we set it aside. Since we won’t be using this wheel for power or brakes, we just left it as is.
To mount the rear wheels to the kart it was quickly clear to me that I needed to come up with something that was strong, and flexible as well as something that would account for the narrowing frame. You see the frame narrows considerably in the front. Simply mounting the rear wheels straight to the frame would result in the kart not rolling very well since the wheels wouldn’t be square. The rear wheels would have some serious toe-in.
In addition to the alignment issue, I needed to have some flexibility to allow for sliding the wheels forward or back to adjust chain tension on the left side. Remember, we want to use the left rear wheel sprocket as a drive wheel.
In searching for a solution here I discovered that the axle fits perfectly into a 1/2″ galvanized pipe floor flange. I then mounted the rear wheels to one of these flanges. I mounted the flange to a block of wood, and mounted the wood block to the frame. Very complicated I know, but that’s how I roll.
I mounted the other wheel/block combo to the frame and voila. I’m starting to see something that could pass as a vehicle of some sort.
With this phase of our project we found four matching wheels, resolved axle issues on the front, mounted our wheels and discovered the creative inspiration that only a sugar rush from Otter Pops can provide.
Next stop some body work.