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Does anyone have any experience using latex tubing with ballsy (300 watts+) motors? This method would make my life easier- I've been trying to fabricate stainless double u joints, but just can't get the tolerances close enough to be smooth.
Jim
The reason I use plastic is that you don't require a set screw, you can simply make them a push fit- much simpler. Also because there is no offset weight from a set screw, the joints remain well balanced even at higher RPM. The one pictured is winding about 17000RPM.
Originally the boat had a cardan style joint, and made a horrendous racket despite being inline. Cardan joints are okay up to about 8-9kRPM, beyond that I find they tend to go a bit flaky. The main problem with a cardan joint is that they accelerate and decelerate as they rotate unless completely straight, which is quite difficult to achieve, and if so would ultimately make the use of a flexible coupling somewhat irrelevant.
Regarding latex tubing, no experience of that. However most rubber tubing will be strong enough, just try twisting it to see if it tears under torsion. Try one and see how it pans out, they don't take long to make, and the worse case scenario is a failed coupling that cost pence- no big deal.
Vulcanized rubber couplings are commercially available for very high levels of power. Be aware that some full size cars still use rubber couplings in torsion e.g. BMW often use them on propshafts, and they were very common on cars years ago when CV joints were still in their infancy (e.g. Lotus Elan driveshafts). They have an advantage of providing a bit of cushioning against drivetrain shock. There disadvantage is they eventually perish and crack. Silicone tubing doesn't do this I find.
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