Fixing a wobbly leg

Hurrying a build will always come back to bite you later!

When I originally built my R2, I was in a building frenzy. In a way, it was almost therapeutic for me, as I needed to get my mind off things, and really focused as much as I could into the build.

The legs was one of those first things I made, and I did not let the fact that I did not have a drill press stop me!

So, instead of .. I don’t know .. ask any of my friends if any of they had access to one, I basically drilled the holes in my ankles freehand. I know for a fact, that these holes have not been straight.

The symptoms of this, has been that my R2 always drifts towards the left when I drive him, and even though I can compensate, as soon as the drive power stops, and he rolls a few decimeters, he always steers off to the left. This has really been a pet peeve of mine, even though it is something only I was aware of, but isn’t that the definition of a pet peeve anyway, more or less? ūüėČ

So, armed with a plan, I took R2’s legs to my friend Anton’s work (where they have a proper drill press) and got to work.

This is the problem area: (and no it isn’t dirty. It is only painted that way)

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A few years ago, I did have the foresight to protect the existing ankle holes, so I had drilled the holes slightly larger and inserted a piece of aluminum tube to not let the threaded bolt eat into the plastic. When the foot was removed, I got proof that my ‘protection plan’ had worked as it should: The threads from the bolt had really eaten into the aluminium bolt! Just imagine what could have happened if it had gone straight into the plastic ankle?

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So, the force has been strong enough to not only impress the threads into the aluminium tube, but also to slightly deform the hole!

My plan was to make a new hole, a straight hole this time, and rather than the existing tubes, I would insert some sort of bushings into the hole.

I had these linear ball bearings that will do just fine for the job at hand:

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First step was to affix the leg to the drill press… and slowly drill through both ankle and the existing aluminium tube to straighten up the hole..

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Since the aluminium tube was only fixed with E-6000 inside, it soon pushed out the other end, while the drill made a straight hole through..

My friend Anton did the first one:

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.. and I drilled the second hole. Scary but a VERY quick fix in the end. The new bushings were pushed in to place …

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A much better solution, and a more solid contact area towards the plastic!

I also took the opportunity to attach the new motor holders (as seen in¬†“Fixing a hobbled droid”¬†and¬†“Fixing a hobbled droid, part II”). Yes, even though I had made these new motor holders way back, I had to abandon them due to a motor dying on me, but this has since been fixed, and this seemed like a great opportunity to put them in action!

Since fixing this, I have not yet had time to do a proper event with R2, but I’ve got a two day event in September that will be a perfect test. I will bring along my backup motor holders just in case… you never now.