Re(Snuffles Reloaded: Update)

Friday, April 25th, 2008 @ 1:16 | Project Build Reports, Project RazEr

There’s plenty in the imaginary part of the update, but you can’t see it anyway.

Hey, this thing looks kind of familiar… It’s the extend-o-pack, with 4 4000mAh lithium polymer cells in place. No, they’re not shorting on eachother, despite the precarious appearance of the tabs.

The Deans connector cutout is a snug fit and should hold a female Deans in place firmly with some CA glue. I need to remember to undersize slots and holes for the LASER cutter by a few thousandths to account for its kerf (since it cuts on the line).

Here’s how it was built.

This is sacrificial vehicle #2, another junked scooter that was sitting around MITERS. I’m not sure if it’s an older generation or what, but there are quite a few structural differences compared to the new A3 model I’m converting. It’s certainly beefier in the folding joint (0.1″ formed steel plate!) and brake area, and there is more material in the chassis.

Efficient re-engineering or corner-cutting?! The world may never know.

The plan is to cut a 12 inch segment out of the chassis and use it as the extend-o-pack body.

After a trip to the bandsaw, this was what remained. It was much like partitioning a fish for cooking – remove the tail, remove the head…

…and clean the middle. Oddly enough, with the parts that remain, I could make a very innovative vehicle.

Here, the side flanges that used to form the upper deck have been milled off, and in a previous unpictured operation, the mounting ear holes drilled.

It might have been better to mill with each flange facing upwards, since the cutting head is always at the same height as the vise above the table, but the vise might not be aligned with the table axis. I tried centering it in as well as I could, but across 12 inches of travel there was still .003-.005 of deviation, enough to have a flush-cut flange at one end but a very light remnant of it at the other.

Oh well, I’m not that good… yet.

After trimming the flanges off, I milled the remaining channel down to the design height of .606 inches, which is just enough to clear the two cells with some breathing space above. I did this in order to minimize the ground clearance hit – these things aren’t known for their great terrain ability, and I was only going to make it worse by sticking batteries under it.

Here’s one of the LASER cut acrylic endcaps installed. They are retained by some drops of CA wicked into the cracks between acrylic and aluminum and one screw on each side.

The waterjet-cut mounting ears have also been installed. It turns out I was off by exactly 2mm on the width of the channel, so dumping all 4 blocks in the same vise and running an endmill through at 1mm solved the problem and made it a slip fit onto the bottom of the chassis.

The other endcap with connector cutouts! On the right side is the last leg of the height-trimming cut where the milling cutter went Z-axis Tokyo Drift on me and ended up slipping lower. Oops. Crank the drawbar a bit harder next time?

And here it is installed. It actually looks quite elegant, with the exception of the other side where there is a small gap from the milling cutter slipping.

This whole assembly slides onto the chassis tube and the mounting screws grab the small flange on the underside to hold it in place. There’s lots of potential for “slide-on accessories”, actually.

So, with my Maxamps order on the way (two more cells to fill in the insides!) I need to get going and design the internal mounting structure. I suspect that it will also be a “slide-in” thing, but from the front – mounting via the four holes at the front.

 

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