'Im not sure I totally agree. Rotating weight has it's pros and cons - any energy before cutin that was used to get things turning is not really lost. Heavy rototing parts help the machine to yaw more slowly -they help it to keep turning in between light winds etc... I agree with much of what you're saying, but there are pros and cons to this stuff.'
Dan, None of this makes sense if you think about it. All energy needed to reach cutin is wasted by definiton because the mill puts out no power prior to it. A weightless rotor would gain speed instanty so there would be no need to store energy. Yawing more slowly is only of value if your mill is heavy. If it were lighter there would be no problem with a quick yawing machine and it would follow the wind better.
"# Your tower has to be much more expensive to make it safe. "
'Not really - the greatest load on the tower is thrust against the blades - that only has to do with swept area, not the weight of the machine.'
Yes, really. The greatest load is not the only load and a moveable weight hung off the top of the tower places loads on the tower than many ignore. Having a weightless mill would reduce the loads on the tower so perhaps I should have said 'less expensive' instead of 'much less'. People on this site often ignore the relitively large loads vibration can cause. Just because you can't see it pushing the tower in one direction does not mean it's not there.
" Your gen will be much more expensive."
'Yes - but thats why so many companies are building high TSR light weight machines - more 'bang for the buck' but the drawback is they tend to break down sooner, they make more noise etc.'
Companies build cheap things because they are less expensive not because they are better. If they break down sooner it would be just as logical to assume that they are poorly designed. A light weight mill may actually be more expensive so equating hevier weight with quality is illogical. Cheaply built mills are cheaply built, what difference does the weight make?
" Any out of balance conditions will be amplified."
'I disagree there too. If a big heavy slow machine with big heavy blades is 4 oz out of balance it's going to be a lot less amplified than it would be on a light duty/fast machine that was the same amount out of balance. The biggest factor that amplifies balance problems is rpm - not the weight of the machine. So I would say the opposite - fast, lightweight, light duty machines will amplify any out of balance conditions.'
This statement assumes your out of balance condition would be the same and it would not be and even if it were the forces generated by the condition would not be helped with addition of mass. You would just have a heavier out of balance object. A weightless mill would have no weight balance issues at all no matter how it was built. There is also no logical reason for a light weight mill to not be slow turning if you so choose.
"# Erecting your mill will be more difficult and when it falls it will likely cause more damage. "
'Yes - true. The cost of this probably isn't terrily significant though compared to the cost of the whole system.'
The cost will be very significant once enough mills get built that these sort of problems happen more often. Dropping a heavy mill on someone's head is going to hurt.
" Your mill will be far less reactive to gusts."
'Maybe... not sure on that one. More heavy stuff rotating will probably average things out a bit more but yes, I expect a 'weightless' machine will be more responsive in some conditions. I don't think it's going to be significant though. The heavier machine is likely to get 'tossed around' less and maybe stay pointed towards the prevaling wind on gusty days.'
No question at all about this one. A weightless mill would react instanly if it were possible to build one so it would be more reactive in ALL situations. There is no need to "average things out" when it would be just as easy to take advantage of the wind power that is there.
Clearly, building a weighless mill is impossible. It is still a far better goal than the idea that thowing iron into the air somehow make sense. I know that this site is all about practical DIY designs. I was just pointing out the impracticality of adding mass.
John.......