Sunday, May 31, 2009

Motor Mount v2.0

Ok, so it's not completely bolted up yet, and there are still a few hiccups to iron out on the final design, but the motor mounts are on!
You might notice the extra hole near one of the bolts for the motor face. Oops, the dummy running the mill forgot to zero the x & y axis before moving to the position for the first hole. To cover my mistake, I ended up rotating the bolt pattern 14 degrees, so now the chain will have less clearance for the mounting bolt closest to the swing-arm.

I'm also not thrilled about the flanges I bolted on to provide a clamping action around the motor, as they look a little cheezy. I would have been better served by a couple of pieces of 3/4" x 1" aluminum stock.
Another lesson learned: plasma tends to cut features about .075" smaller that drawn, so I ended up doing a lot of handwork to enlarge the internal diameters on both brackets.

Friday, May 22, 2009

Plasmarrific Motor Mounts

So it turns out that the tapered plasma cutting path was indicative of a worn electrode and nozzle. With a fresh electrode and nozzle, I gave the plasma cutter another shot.

Another lesson learned from the first go-around with plasma is to orientate the pattern so the more accurate side is facing up. In my case, the left bracket was cut with the side that faces the motor on top.

Sunday, May 17, 2009

Motor Mount Mishap

After countless paper and wooden templates to get the motor mount shapes and hole patterns just right, it was time to give it a shot on the real stuff. I ordered a chunk of 3/8" aluminum plate. Using the CAD drawings, one of the guys at work helped me cut the basic profiles on the CNC Plasma cutter. I was totally stoked looking at this complex geometry that took about 60 seconds to cut out.
Unfortunately, my elation was short lived. Several edges of the pattern were severely tapered, so even though the shape was perfect on one side, it was off by almost an 1/8" on the other side. I knew the shape cut by the plasma would be a little rough and had adjusted tolerances accordingly, but it hadn't occurred to me that the plasma would cut at an angle. It's possible something needs to be fine tuned. If that's the best plasma can do, I may need to rethink the manufacturing process.
Once the outer and inner profiles are cut correctly, I will use a mill to precisely drill the mounting holes for the motor and frame. Just for kicks on this piece though, I drilled the mouting holes using a paper pattern as a guide. Of course the holes for the motor didn't quite match up, so all I could do was bolt the bracket to the frame to see if it's close.
A little dissapointing, but not too bad for the first go round.

Monday, May 4, 2009

Re-assembly Begins

I've been asked why bother to strip everything off the bike and go throught the tedious work of cleaning all the little pieces. First, I'm anal retentive and have to. Second, there's no other way to know what's missing, worn out or broken on a 20 year old bike.

I cleaned all the pieces of the rear suspension and put it back together. Initially I thought a spacer was missing on the linkage lever. Turns out it was assmbled incorrectly, and judging by the wear in mating aluminum pieces, been that way for a while. You can see how much more of the left spacer is exposed. While not catastrophic at this point, addtional wear could definately be a problem.

I have gone through several iterations on the wood patterns for the motor mounst and got the design close. I'm confident in the hole locations for the motor, but not too sure with the bracket locations on the frame. I needed a more accurate template to work with. The cheap solution was a piece of 3/8" x 1" aluminum bar with a printout of the only the frame hole pattern pasted on. After a couple of more tweaks, I should be ready to cut the actual 3/8" plate.