There it is- the new guard. I haven’t put it onto a chair yet, but I have a good feeling about it. I think I got things fairly straight. A jig to hold everything during tack welding would have made things go together easier. It also would have been nice of I had been able to mill the edges of the inside edge of where the horizontal tubes come together at 90 degrees. I had to grind off the interfering edges, and any imprecision created a gap that I had to bridge with filler. It’ll be strong enough, I think, but would have been easier with a nice tight fit all around.
It weighs 10.8 pounds, about two pounds more than the World Cup guard. I don’t have access to a CAD system that will calculate rotational inertia for me (and I don’t feel like doing it by hand for), but I suspect that the new design isn’t quite as good in that respect. Regardless, this is about $80 worth of steel, compared to $300 for the cheapest commercially available guard. It also has a much more square tip, allowing the player to hit the ball with a spot closer to the end of the guard where the speed is highest.
Have you tried a “joint-jigger” for making the tube joints? You can get cheap ones at HF, and more expensive ones elsewhere… Essentially it is a fixture that clamps into a drill-press, with a vice that clamps the tube in place, and a rod that goes into the drill chuck and holds a bi-metal hole saw about the tube diameter on the other…. You cut the tube with the hole saw, and it gives you a nice “mouth” of the right diameter. It is even possible to adjust the angle to do angled joints… Works pretty nicely though it’s not as precise as a mill… It’s what we used in my TIG class to make test piece joints. It does take practice to learn how to cut the right length, but that can be figured out….
No, I haven’t- but thanks for the suggestion. I do all of my work these days at TechShop in San Francisco, and I mostly use the tools that they have available.
Adjusting the angle sounds great- TechShop didn’t have anything on hand to do that easily. I can definitely think of some great reasons to use that capability. I’m glad to hear you had a TIG class. I’ve been looking at more of the wheelchairdriver.com threads seeing what you’ve been up to- sorry to say I’ve been pretty absent over there lately. I guess that was probably noticed.