Saturday, January 28, 2012

Assembling the chassis

This post is going to document the assembling of the chassis. I purchased the Magician Chassis as the basis for my bot. Assembly was mostly straightforward, although I did need to do just a little hackwork along the way to bring it together. The finished product looks like this:



It's not the greatest photo ever, but you get the idea. There are two motors, one attached to each large wheel. There is an additional rear "trackball" thing which bears the weight of the rear end. The construction is sturdy-ish. Certainly it doesn't seem like it's going to break during construction, but it should definitely not suffer a drop.

The kit comes with instructions, which kind of mostly cover what you need to know. In addition to the instructions and this blog post, there is a similar blog post available here: http://www.hobbytronics.co.uk/magician-chassis-build. It's probably more useful than this post, but this is my story :)

Here is a photo of the kit parts, unassembled:



The process begins by attaching the motors. This turns out to be medium level tricky, where easy is "goes according to the instructions" and hard would be "I basically had to MacGuyver it from first principles". My main issue was there there are some little red things which look like gears which attach to a spindle on the side of the motor. THESE APPEAR TO HAVE NO FUNCTION. Even after assembly, no function.


You can see the red thing here. One of my red things needed to have the whole expanded carefully with a Stanley knife in order to accept the spindle. Bolting the struts on was not too bad, although it's a darn tight fit. I had to rotate the struts 180 degrees even though they look pretty symmetrical. They do go on. Anyone who knows what those red things are for, please let me know.

Attaching the wheels is a matter of shoving them onto the outside spindle of each engine. They don't fit very well (no satisfying push... click). So I hope they don't come off, but it seems okay.


Attaching the trackball is super easy. No worries there, although I might lubricate the socket at some point. The base is now completed! The leads running off the motors strike me as a bit of a catching hazard, I think it would be better to put some electrical tape on to help run them up to the upper level where they will attach to the Arduino later on, but I'll do that at another point in time.

The next step is to put the base right-way-up and attach the battery housing. The battery housing is terrible quality, and in a stupid place. The worst thing about it is that the screw-holes are so close to the edge that you can't actually put a screw in. I had to cut down the edges with a Stanley knife. I hope this isn't a problem later.


See the screw? You can see it through the hole I cut to allow the head through.

From here, it's a doddle to finish assembly. Screwing on the spacers and the top level is super-easy, leading to the finished product:


As you can see, the battery housing is in a near-inaccessible location. The HobbyTronics post I linked to earlier said they pulled it out and housed it on the top level, which certainly makes sense. However, I figure I should follow the rules before breaking them, so there is the finished product!

Of course, right now it doesn't DO anything, because I haven't wired up any power or attached the Arduino to control the motors. However, it was a great evening's work and took a little under two hours from fetching my equipment to a finished product and a clean workbench again.