Go go go-kart again.....

Small update. I wanted to do a couple of things - lots of the time with this, I have to leave with a problem still unsolved. I kind of have the thought about how I'll solve it, but not sure if it will work until I try. One example is how I am going to transfer drive to the wheels. In a normal go-kart that you'd buy, the axle has a keyway cut in it. A sort of square-ish channel. There's another cut in the wheel hub, and then when you go to assemble it all, you line up the two keyways and push a piece of rectangular bar called a key into the hole. This means that the axle and wheel will turn together.

If I had a mill, or a broaching machine, I could probably make the keyways, but I don't, so my plan is to drill and tap through the wheelhub and into the axle, and screw in a high-tensile steel machine screw into it. I'd done this, and got to the stage where I was about to screw in the screws, when I realised an error - I'd made the holes fractionally to close to each other and the screws interfered with each other. I was wondering if I could turn the screwheads down just enough for them to miss each other, and, luckily, I could!

Just a few odds and ends to address. Need to dress the welds holding the wheelbolts on and trim them to length.

I've also carried on with the other wheelhub. I had to weld up the hole I'd made down the middle because I need to have a flat surface for marking out the wheel bolt holes. So I welded it up and faced off the weld in the lathe. Then I did a bit of schoolboy geometry and marked out and drilled the holes.

Next I needed to drill a 30mm hole down the middle to match the axle:

Starting with a very small drill bit, and then moving up to the final size hole which is cut with a reamer.

Bit of a test fit.

And then weld on the wheel bolts and mock up:

I need to go through the same process with the drilling and tapping on this side too, and then that's the wheels done. All 4 of them!

A little more go kart? It's only waffer thin...

On with the steering. On the last update, we had the steering column (or whatever it's called in this context) done, and the front uprights and steering arms in. Now need some steering rods to go from column to uprights. These are made out of 12.5mm bar, but I needed to turn the ends down to get an 8mm thread on them to accept the rod-end bearings. Pic on left shows the turning, pic on right shows using the die for the thread - you can see the thread on left end of the rod already has the bearing on it.

And the completed rods connected to the steering arms and to the column

Now need to make a steering wheel boss. The technique I've used is the same for wheel hubs, sprocket carrier and now this. Cut out a rough circle the right size out of steel plate with a grinder. Take a piece of bar (in this case some of the same stuff as I've been using for the axles). Drill a 5mm hole in the centre of both and use the 5mm drill bit to align the two. Then weld them together, put the now joined part in the lathe, face it, turn it to a true circle, and then drill it for the column and wheel.

So it ends up like this. I've marked it for the steering wheel.

And drilled and tapped the holes to attach the wheel....

I drilled through the lower part of the boss and into the steering column to make sure the column turns when the wheel does. So this is how it looks now. I've missed an episode where I've got the left hand back wheel on. It's more or less the same drill as the steering wheel boss:

 Below is the process of making a wheel hub, or steering boss, or sprocket carrier. Cut out rough shape (I did mark out the diameter that I needed first - it's not all guesswork!)

Got to a rough circle.

Next step is to smooth it out a  bit - it has to go on the lathe and the less the tool gets smashed into by sharp edges, the better. Because it needs welding, it also gets a good sanding down so that the weld can penetrate.

Turning a piece of bar in the lathe. The diameter isn't crucial - I'm just trying to get the edges parallel and get rid of any corrosion. I get the ends square too, so when the other part is welded to it, it should run true (this rarely seems to happen 100%, so the whole lot gets faced again to ensure the face is perpendicular to the axis. I also put a chamfer on the ends too. The idea is that there's more for the weld to get into when attaching the circular plate.

The two pieces are welded together and spun up in the lathe.

Need to swap to a 4 jaw chuck - want this to run really true.

What it ends up like. Time will tell if this works out....

The part I'm making above isn't the sprocket carrier - it's the hub for the right hand rear wheel. Once that's done, it can sit on 4 wheels. I think that will feel kind of satisfying.

Since I've done all this, I've found somewhere in the UK that looks like they do bits for off-road karts, so I'll look at those next time to see if there's time I can save just buying bits. There are things that really don't need to be made. It's enjoyable to do though - apart from the odd ruined part, it's been fun doing everything from scratch...

More Cowbell? ... no, more Go Kart...

Onto the front end. Wanted to make a kind of wishbone type set up. Although there's no actual suspension, there are upper and lower frame rails, so it makes sense to utillise the both of them. So, after a bit of trig to calculate the angles, the various parts were cut out.

Then I needed something to hold the bearing that will hold the upright. This is just some rectangular bar with a hole drilled down the middle. I probably should have set this up in the lathe, but my crappy pillar drill's done a job for me.

This is what I ended up with.

 Welding it all together gives this:

I made the upright out of the same rectangular bar. This time it was set up in the lathe, and the hole drilled and tapped to M10 in the centre at both ends. You can see now how the whole arrangement is. The two Rose type bearings hold the upright. The steering arm and axle is already welded to it at this point. You'll note that the top wishbone is set behind the bottom. This gives the upright some castor angle. The idea is that this helps the steering self-centre.

The one thing I'm not 100% happy about is that  I'm not sure that it's OK to triangulate that lower wishbone in to the middle of a tube like this, but it seems sturdy enough.

Below the axle clamped in the vice, ready to have an M20 fine thread cut into it. The axle (like the rear) is 30mm, then turned down to 25mm where the wheel runs, and then to 20mm to take the thread for the wheel retaining nut. I did all that on the lathe. I definitely need to take more pics! I haven't dressed the welds yet...

Making the thread. I was concerned at this - I thought this process would be tough going (especially as the axle steel is hardened), but the die cut the thread no problems at all.

Finished! You can also see how the upright's made too. Very simple.

And on the kart.

Both sides done and on. I haven't got the retaining nuts on the wheels. Mostly because I'd ordered coarse thread nuts, and I need M20 x 1.5mm pitch. Doh.

A few other things are clear - the seat arrangement has changed. Instead of the plastic go-kart seat, I've made a steel frame for a seat that has foam and faux leather covering. It's red! I'll get more pics (I know...). From the picture above, you can also see that the steering's coming on too - the column runs in two bearings - these were heinously expensive for their use, but never mind. Next time perhaps I'll just run bearingless.