CNC is cool! But CNC is not the only way to make things. Our world got a long way without computers, with screw machines and pantographs and Hardinge lathes and various cam-guided manufacturing machines. I made the one below for cutting roll bar components.
"So what?" you may well ask. Well, between this tube cutter and our two bit digital tube bender, we can crank out roll bars for about 3/4 the cost of conventional techniques, and send the savings your way. Besides, us locosters like showing off our fiendishly clever penny pinching techniques.
The tube rests on a series of ball bearings (far left bearings not shown). It has one PVC drive drum and two PVC cams hoseclamped to it. The drum is sized for the wall thickness of the tube; thinner tubing cuts faster than thicker tubing so we use a smaller drum for thin tubing, rather than invest in a vaiable speed motor and controller.
The positioning cam on the left is straight cut; it merely holds the tube steady against the grounding stud, resisting the bungee cord's pull to the left. That bungee cord pulls the plasma cutting torch (mounted on a ball bearing drawer slide) to the left...
...where it's stopped by a skate wheel bearing riding against the pattern cam.
The photo below shows a tube after it has been cut. To cut, the operator clamps the pattern cam so there's a bit of overhang to the right of the torch, and fires off the plasma with a foot switch. As soon as the plasma burns through the tube, he flips the drive switch and the tube starts turning. As soon as the end piece falls off, he shuts off both torch and drive. Oh yeah, the fan has to be running or the heat will work its way down the tube and melt the pattern cam guess how I know that?
I'll take some photos of our two bit bender some time this week. Meanwhile, during my July Tour de Frames, I dropped off a four tube rollbar kit with Nathan up in Ohio...
...and he and his friend David held it in place (roughly) so I could get a shot of it in sutu.
You'll note the hoop legs and rear brace tubes are not cut to length. That's so you can set your rollbar height and angle to your own taste; the lower ends are straight cut and don't require any fishmouthing, so we figure you can cut them to length easier than we can. Nate wasn't sure exactly what intersection angle he wanted on the top of the rear braces so we gave him a choice, and he'll cut off the end he doesn't like once he decides. The options are 0 degree, 10 degree and 15 degree fishmouths; Nate ordered 0 and 10 on the rear braces (and is going to go with the 10 degree, as you can see).
At present we're bending (and stocking) 1-1/2" diameter only, but you can have your choice of .109" or .120" wall. Hoops are $150, the four tube kit (hoop, diagonal, two rear braces) is $300.