I want to ask opinions on belt approach that Hiho has mentioned a few times. I was also of the opinion that any kind of compliant belt was not going to be the best solution. It seems in my brief experiences with speed controllers of late that with a DC approach the system does benefit from tight coupling, hence mylar can work very well.
The difference in DC controller operation can make or break this theory of mine. I would characterize one controller/drive system as being similar to the approach Dertonarm mentioned, that of counting on a certain amount of slippage. Another controller, (same motor, different controller) just happens to be one of Mark's old DC controllers, seems to improve with increased tension => no, or almost no, belt slippage. This does require a pretty hefty motor pod to help keep things taught. The presentation of this second DC approach is very much like what I hear with rim drives and maybe some lower end DDs. How much like rim drive I can't say as I don't have a good candidate for A/B.
So I thought I was all set with my drive choice. And then a friend brought over an AC motor and a Kelly AC controller. As you might expect, the cogging of the motor is very apparent with the mylar belt, even with less tension. The best setup was achieved with very little tension and a fair amount of slippage. Even more than what was used with the first DC controller. So it would seem that a more compliant belt would be called for with the AC approach. The amazing thing to me was that even with the huge amount of slippage the AC motor/controller was really kicking the DC arse in many ways.
After learning some these new things for myself I am no longer so convinced of what I thought before about belt compliance. Surely we would all love to have the perfect motor. But since that probably isn't going to happen, it seems to me that the controller becomes more important. At the same time, the selection of the motor and controller would seem to dictate what belt candidates should be considered.
Mark, I am still somewhat surprised that the particular platter/bearing does not seem to influence your designs. Or do you just make it look too damn easy? :-)
The difference in DC controller operation can make or break this theory of mine. I would characterize one controller/drive system as being similar to the approach Dertonarm mentioned, that of counting on a certain amount of slippage. Another controller, (same motor, different controller) just happens to be one of Mark's old DC controllers, seems to improve with increased tension => no, or almost no, belt slippage. This does require a pretty hefty motor pod to help keep things taught. The presentation of this second DC approach is very much like what I hear with rim drives and maybe some lower end DDs. How much like rim drive I can't say as I don't have a good candidate for A/B.
So I thought I was all set with my drive choice. And then a friend brought over an AC motor and a Kelly AC controller. As you might expect, the cogging of the motor is very apparent with the mylar belt, even with less tension. The best setup was achieved with very little tension and a fair amount of slippage. Even more than what was used with the first DC controller. So it would seem that a more compliant belt would be called for with the AC approach. The amazing thing to me was that even with the huge amount of slippage the AC motor/controller was really kicking the DC arse in many ways.
After learning some these new things for myself I am no longer so convinced of what I thought before about belt compliance. Surely we would all love to have the perfect motor. But since that probably isn't going to happen, it seems to me that the controller becomes more important. At the same time, the selection of the motor and controller would seem to dictate what belt candidates should be considered.
Mark, I am still somewhat surprised that the particular platter/bearing does not seem to influence your designs. Or do you just make it look too damn easy? :-)