Coach Chassis Progress

Building the chassis for the coach out of metal (aluminum) meant that I needed to learn some new ways to do things.  As it turns out, MIT (yes, that MIT) has a collection of 10 video lessons online giving a complete introduction to machine shop tools and techniques.  For free.  I've watched about the first half of them, so when it came time again to work on the chassis I took a shot at trying them out.

From what I've gathered, layout is one of the most crucial steps.  Woodworkers have that saying -- "measure twice, cut once."  The same holds true for metal work, however being precise is brought to a new level.  When I was building the chassis, I needed to make sure that I got the width in which the wheels would be mounted as exact as I could.

To do this, I started by making black lines on the metal in the general area where I was going to make a mark.  This gave me a surface to scratch off (this is an easier and faster way of doing what most machinists would use blue layout dye for)...

You can probably guess I used a sharpie for this.  With the black in place, I started my measurements, then use a scribe which is basically a sharpened piece of metal rod to scratch off the black where I needed the line. This left a very high contrast line to work by.  Note that the width of the line here is a bajillion times skinnier than a pencil line and allows for a greater degree of accurate measurement and layout...

With accurate lines I was able to construct the chassis to be the proper width to mount the wheel journals (axleboxes) on...

I haven't yet bolted the journals on, but here's an idea of what they might look like once mounted...

Now when it actually came time to seat the body into the chassis, I realized something...

...the chassis is less than 1/32 of an inch too short!  In some sense I'm kinda proud that I was able to be that accurate without a caliper or some sort of other measuring device and by using just hand tools (hack saw + file), but on the other hand it means I need to shave down 1/64" off of either side.  I'm sure it won't be a huge deal to fix.

I was curious how it would look and perform with the wheels in place, but wasn't quite ready to commit and bolt down the wheels.  So I measured the approximate location and taped them in place just to be able to see and try it out.  Here's a short video...