rfw2003 wrote on 04/04/13 at 14:53:45:srinath wrote on 04/04/13 at 13:51:08:If you're making them ... suggest you dont use a solid rod -
I'd use a pair of allen head bolts @ the 2 ends and a bit of pipe connecting them all welded together or something like crimped and welded or something like that. Pipe is stiffer than solid rod.
6061 Aluminum - with anything you have to tap the weakest point is where the threads start - that thread dia @ the ends is so small you'd easily have a situation if you're unlucky that it will end up breaking at that spot.
With a bolt in a pipe, you'd weld to the bolt head, so you're welding a thick strong location. Not tapping and stressing a thin location.
Cool.
Srinath.
On both materials I would do a slight taper for the transition from the threaded are to the solid rod area, to relieve the sudden weak area from the cut threads. Even with machining the same size threads on a piece of bigger stock will make the whole part stronger as a whole, since the main issue with the shift rod is not breakage of the threads, but bending of the rod itself because it is to small in diameter for the job that it is supposed to be doing.
I also have plans for redoing the whole shift rod linkage period to a much better setup, but to do that I will need a spare set of levers both front and engine case side to do this with. My plans are to make them easier to maintain the lubrication on them plus make the shift linkage smoother at the same time. I can't do anything about the smoothness of the gear box itself, but I can make the shift linkage pretty much bulletproof.
R.F.
Actually there may be a way to make this cheaper and better. See machining is $$$, cutting threads is even more so, labor intensive, arm breaking work not to mention failure prone ... so your best bet is to use bolts in the ends. You can get those inexpensive and they can be hard as a rock, and if you break those in use, the end use can replace it cheap. The trick is to make it so it wont spin around when you're trying to install and adjust it.
My thought is - you get the bolts with allen heads in a good hard material. Get the same temper steel tube that fits tight on the bolt head. Drill them both side ways with a small size drill, like 1/16th or 3/32. Small. Then put in a tension pin. You're done. If they fail in regular use, the end user can get em out, pull the tension pin and replace the bolt.
Tapping steel even mild is arm breaking work, hardened - you're gonna need a few 1000 in tools. Acorn dies and possibly a serious machine made for tapping. Aluminum is better, but still will take up a lot of your time, and at the end be non user serviceable.
Cool.
Srinath.