Nov 16 2011

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Completed Flat Cars

Once I was satisfied with the prototype flat car, I wanted to make a whole mess of them at once — nine in fact. I decided to create a few jigs to make production go more smoothly.

I built the first jig for cutting out the wheels. It solved two problems, splintering on the backside of the cut and producing at least 36 wheels exactly the same width. To back the dowel as I was cutting it, I routed a cove in a scrap of wood with a 3/8″ radius cove bit.  Next I cut a kerf about halfway through it to hold a thin piece of wood as a stop. I placed one of the prototype wheels on the jig and marked where I needed to cut, then applied some double-sided tape to the bottom of the jig and positioned it on my miter saw. There is one problem with cutting such small pieces on the miter saw — the piece is so light that as soon as it is completely disconnected from the mother dowel, it’ll fly out of position and get sucked up by the dust collector or get damaged by the blade. To stop this from happening, I had to stop the blade while it was in the down position. This added about 5 seconds to every cut to wait for the blade to stop spinning.

I didn’t want to mark the center of all 36 wheels individually, so I next I built a jig for positioning the drill bit in the center of the wheel. For this simple jig, I used a 3/4″ Forstner bit to drill a hole slightly deeper than half the thickness of a wheel. Then I used a bit the same diameter as the axle hole to drill the rest of the way thgouth the scrap — of course the Forstner bit left a nice divot exactly in the center! I was able to drill about half the holes before this jig wore out, the hole just got too sloppy after so much use, so I made a second jig to finish the rest of the wheels. A side benefit of this jig was that it held the wheels firmly so I could sand the face and ease the edges of the wheels. It was much easier than trying to hold the small wheel with my hand.

I didn’t need to make a thin rip jig because I had previously built one, but it came in handy for a few more pieces of stock for chassis. I also didn’t need a make a jig for chamfering the bottoms of the chassis either. I just used my miter gauge on my oscillating belt sander set to 30° and fence extended to almost to the belt.

To drill the axle holes in the chassis, I used a jig on my micro-mill. The jig allows me to index the piece be the corner and fine tune exactly where the hole goes with the X-Y table. Once I zero in on the location I lock down the table and theoretically every hole I drill should be in the same location. Unfortunately, I’ve found wood often has a mind of its own and the grain can deflect small drill bits. Some of the holes started in the right location but came out the back side slightly high or low. When I put the wheels on the cars, I was able to compensate somewhat by angling the screw into the hole.

Once I had all the pieces for the bed and chassis finished I roughly sanded them with some 100 grit sandpaper then glued them together. Since the enamel spray paint I was using would hide most flaws, I didn’t worry about making the cars really smooth, I just knocked down the rough spots and removed flash. One problem I ran into was that I put paper underneath the parts when I was painting them. I needed to re-coat the spray paint within an hour or wait a few days so the pieces were still tack when I flipped them over. The paper stuck to the paint. I’m not sure why I put paper down, I usually just pray on top of old clean sheets, that way nothing really sticks.

When the paint dried, I assembled all the cars. I gave six of the cars to my son right away and kept 3 in my shop. I think I might give them away as presents.

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