Saturday, March 30, 2013

The Master Link

Well, we did it. The kart moves under its own power*. Today was focused on brakes and the handle bars. Completing the brakes meant we have completed the infamous milestone 7 which is mechanical inspection. We ended up with a bit of extra time and decided to go ahead and add the chain that connects the motor to the wheel.

*We haven't installed any of the electrical system. We directly connected the motor terminals to a single battery (12v).

Attaching the handle bars was a bit difficult. It was meant to be a friction fit, but a few imperfections in the machining meant about half an hour wailing on the end of the handle bars with a rubber mallet to get it to press together. That thing is not going to come off.

This is our brake cable. Having wood all the way along the chassis turned out to be quite handy. It's easy to drill a hole wherever you want it. These connections weren't planned out in detail but the brake works. The block holding the crimped end of the cable sleeve will be put on standoffs so it is inline with the actuation arm. At the moment the brake handle doesn't return with much force. Moving the block should fix this. It feels like everything on this car is informally dubbed a block if we can't think of the technical term for the part after 30 seconds.

So, McMaster sells roller chain in one foot increments. Typically you buy more chain than you need, cut it down to almost the size you need then use a special piece called the master link to join the free ends thereby making a complete loop. We bought two feet because the CAD said that would be enough and we don't like wasting money. As we built things we relied less and less on the CAD and more on what was in front of our face. The motor ended up mounted further from rear wheel than what the original design showed. We pulled the chain over both sprockets and they were just shy of meeting. But then we remembered, the master link! After loosening the axle mounts it turned out the chain was perfect. Not a single link was added or removed. You can see our chain tensioning technique above. The only thing left to do was to stick the leads on a battery and take it for a (slow) test drive.

Caroyln apologizes for the sideways video half way through. The videos will only get more awesome form here. Think three times the speed and ten times the control. Electrical systems are up next and we're both pretty excited. We may even be able to drive this thing around during CPW (happening in two weeks) and we're pretty sure that would make us the cool kids.

Spring break is ending, I'll be posting less often. I don't know if I'd describe break as relaxing but it certainly was productive and enjoyable.

Until next time.