Redesign, 36mm question.

[Dan Richardson]

Originally Posted by Justin M.

We are at the same weight, just about. The arm is actually going to be made of 80/20 1515 , I just modeled it as normal aluminum square tubing for sake of simplcity in seeing my design. The one 5' piece of 1515 weighs 6.7165lbs. (based on the 1.3433lbs. per foot given in the catalog), and our claw, by my guess, weighs maybe 2lbs, also made from the 1515 extrusion - so realistically, we are looking at ~9lbs. I just said 15lbs. as an overestimate - tomorrow I'll actually weigh everything out so I can have an accurate sense of how much this thing actually weighs.

I'll probably just put an order in tomorrow for a 2 72 tooth sprockets from IFI, and have them next day aired, just to play it on the safe side, 11:72 should be more than enough to lift this thing. I think we have some 60 tooth steel sprockets laying around our storage room somewhere, and we also have the 3/8" bore 11 tooth sprockets for the motors themselves, so I'll put those together real quick with those other sprockets and see if it works.

Ok, we've made one change, the motors and everything are fine and the backdrive was negotiable but we went to Home Depot and bought a gas spring strut typically reserved for cars. We mounted it aprox. 5" down the arm that way at the most extreme of cases the arm was nearly neutrally boyant. The motors are then able to keep the arm completely still just by putting in the pwm jumper for the " break " ( also for testing purposes shorting the motor does the same thing )

The mounting for the gas shock and all weighed in about 1.2 lbs and will greatly increase the life and functionality of our arm. Infact the gas shock was so affective it negates the need for our second motor, however we left it on because we like high safety factors. If your worried about motors wearing out or backdrive this is a wonderful solution thats overlooked and under appreciated. If you need some pictures of what I'm talking about I'll get someone to take some and send them your way.