Chapter 3: For every go kart turn, turn, turn.

Posted: August 20, 2009 in building a go kart, building a go kart frame, childhood, go kart plans, Go Karts
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Lower control arm ready for it's anchor bolt.

As I noted earlier, all of the parts from this project are readily available at most hardware stores. At this point I have my frame more or less together. Prior to squaring it I had to temporarily mount the upper and lower control arms. Once that was done I then removed them and drilled the holes for the king pins (or spindles). The spindles are used as a mounting point for the wheels, but also will provide roughly 40 degrees of turning radius. Go karts are definitely much more fun if they do more than just go straight.

The spindles each consist of 1/2″ galvanized pipe T fittings and are anchored in place via 3/8″ to 1/2″ pipe connectors. It’s really quite a simple and clever setup.  First, I set a center point 1/2″ in from the end of both the lower and upper control arms and drilled a 7/8″ hole about 1/4″ deep using a hole saw fitted to a hand held drill. In rummaging through the endless drawers of my Dad’s tools I realized he had a number of these which made me wonder, why? Some of them had wood bits still within them from the various projects he had done over the years. Luckily for me he wasn’t one to hesitate to run out and buy a specific tool for a task that he would use only once.

After I drilled the larger, outside hole, I then drilled a smaller hole the same size as the threads of the pipe nut in the photo. The idea here is that the nut would be carefully threaded into these holes. Once threaded down the nut would sit nice and flush in the control arm. To get that nice and flush fit took quite some time since I had to sand, and file carefully to slightly enlarge the hole otherwise the control arm would crack or split altogether. You will want to thread this bolt through so that a few threads are exposed on the opposite side of the control arm. At one point I wasn’t able to easily thread it far enough so rather than push it and risk cracking the control arm I took the hole saw out and drilled down a bit further, allowing the bolt to sit slightly lower in the hole.

At this point the thought did enter my mind as to whether or not this would be strong enough for the boys to ride on, let alone to even drive. I figured that the existence of these plans at least implied it was tested after being built, so I put that thought in the back of my mind and pressed on. In all likelihood the overall structure will only get stronger as more of it gets assembled… right?

Bottom control arm with both spindle holes set.

Bottom control arm with both spindle holes set.

Next I mounted the lower control arm back onto the frame. You can see the holes in the top of the frame rails where I had previously mounted the arms for squaring up the frame. From here you can also see the narrowing of the frame to accommodate the turning of the front wheels. I’m not sure how critical having the frame narrow like this is, since the result is that the back is a few inches wider. The plans call for this so I’ve gone ahead and followed it verbatim. As I quickly realized later, that narrowing is a bit of a pain for a number of reasons but I’ll get to those soon enough.

Before I follow up with the upper control arm I need to now insert the T fittings that get sandwiched in between them. First the large connector nut is carefully screwed into all four holes; two on the lower and the two upper.  Next I insert the T fitting into each nut on the bottom, carefully not forcing it to turn too far, and keeping it slightly loose so that it can turn easily. I’ve also added a bit of white grease to the threads for good measure. The easier these turn back and forth the easier the overall turning will be for the kart, so it’s important to spend the time here to get this right.

In addition to the goal of  free spin here, I found I also needed to account for the vertical space limitation. That is if I had the threads backed off too far the control arms wouldn’t mount back onto the frame without a big gap, but if I threaded them in too tight they wouldn’t turn freely enough. I could always insert a shim or something to account for that extra space, but I really didn’t want to do that.

After an hour or two of sanding, threading, some “Dad is the go kart done yet?“s, more sanding and more threading I was able to get the nuts through and the T fittings in place comfortably.

T Fittings mounted in lower control arms.

T Fittings mounted in lower control arms.

With the T fittings mounted onto the bottom, and enough play to both spin, but tight enough to fit in the space between the two control arms I then mounted the upper control arm back into place. Once the arm is in place and screwed back onto the frame you realize that there really isn’t anywhere for the T fittings to go. Even if they were to completely unscrew (which is virtually impossible since they’d be attached to tie-rods) the control arms have them sandwiched in place so again, a simple and pretty clever assembly overall. My Dad would be proud. 🙂

Once both control arms are in place you can see where the threads on the top of the upper control arm, and bottom of the lower control arm, come through just a bit.

Upper and Lower Control Arms with T Fittings in Place

Upper and Lower Control Arms with T Fittings in Place

The plans call for a 1/2″ electrical conduit lock nut to help to secure these in place.  Although these would do the trick they’re not very attractive. You could also use a galvanized pipe cap, but I realized that a brass garden hose cap fits perfectly and could be polished up quite nice. You can see the brass cap here in this picture with everything all in place nice and tidy like.

So far we have our frame, we have our upper and lower control arms, and spindles all mounted. I’ve even gone so far as to drill the holes into the spindles allowing for me to mount the wheels.

Oh wait, wheels. That’s right this thing needs to roll!!??

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Comments
  1. Mark says:

    You’re giving me plenty of “smack the forehead” moments here. This is really looking great!

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