PMG Mill Back in Service

[brianc4]

  I havn't had much time to post of late so here is a quick update on our PMG Mill. Above is a picture of the mill with its new tail & the new blades I have made pictures smaller & less resolution for folks on dial up. If anyone needs a better picture of any of the projects I have posted just let Me know and I will Email them a High res. copy.

   As you can see from above picture the site where We have the 25 foot test tower is in a dismal location! Everything around it is taller than the tower & it is even worse now that the leaves are on the trees. However it has served its purpose of allowing us to test the mill with the blades at a safe distance above us.

  Here are a couple of refurbised truck batteries we have hooked up to the mill for testing output. There is a diode inline so that the mill doesn't turn but I do not have a charge controller hooked to it. We have been keeping a daily check on the battery volts and drain them down with a test light to make sure there is always room for batteries to charge.

  Here is our test light with a 50 watt 12v bulb.

  Here is a picture of the Battery cable arrangement & the saftey cable & spring. The steel cable comes tight & loads the 80 Lb pull spring completly long before the battery cable gets tight. Keep in mind that this mill furls by direct blade furling so even if the mill gets wound tight the mill can still furl. The mill has been up for almost 2 months now and is in a terrible & turbulent location but I have still not seen more than 1 full wrap of cable at any time.

   I have been warned by Flux & others that this would not be a safe setup for a tail furling design and I see why but so far I am not seeing the cable wrap up & this tower & mill is in a terrible location.

   I hate to revisit old discussions but any comments about the possibility of using this setup on my tail furling axial mill would be welcome.

[Flux]

I can't remember the whole story, was there some reason why you couldn't drop the cable down the centre of the pipe ( could be awkward with tilt up furling).

With tail furling you will have trouble if the cable prevents the yaw head from rotating. If you can make sure this doesn't happen then I see no problem. If you leave a large loop of cable like that with a furling tail I think you will lasso the prop sooner or later during a violent gust.

If you are careful and always unwind the cable before the rotation is restricted then it should work. I tried a loop of cable near the top once and it would never stand more than about 3 turns, it broke the cable more than once. I ended up with a loop running through a weighted idler pulley so that it could wind up about 10 turns. This gave plenty of chance to unwind it before trouble.

Flux

[brianc4]

Flux,

   I am using a trailer stub axle & hub for the yaw bearing so I have no access to the center pipe ,this can be changed in future designs. I still am leaning towards good quality slip rings like you sent me a link to.

   However it is still tempting to try a similar setup as on the PMG mill & watch it very carefully for wind up.

Brian

[oztules]

Well I like it, and I even like your solution to the wire down the mill, given that you can't go down the middle.... if it never wraps up as you say thus far.

A furling tale design....well you heard Flux, but perhaps that could be mitigated by coming in closer to the head, rather than out near the tail.... but perhaps better to use a pipe and go down the middle... stick with tradition so to speak.

Beaut looking country you have there too.

........oztules

[electronbaby]

Since you are using a bearing for the yaw, you must have some pretty tight tolerances. You would be guaranteed not much slop in the arrangement. If it was me, that would lead to experimentation with a slip ring set up. The current school of thought with the usual pipe over pipe yaw arrangement does not lend itself well to slip rings because of a lot of slop between the pipes. Pipe over pipe is a very simple yaw setup however and the KISS principal reigns supreme in most instances.

Just a thought.