use of sliprings

[Pebbles]

Hi Guys
I have been reading the posts on sliprings, I kind of get the idea that they are not used much. Do you guys use them? A lad i work with doesn't , he doesn't even allow his mill to revolve 360 , has a lock pin at due south, he loses some wind sometimes for a few min till it gets kicked back around but he has been running successfully now for approximately 5 years with no furling and no sliprings and never had cable problems.Am i trying to overcomplicate the wind mill  with sliprings?? would appreciate some input ..:-) get the feeling I may have been flogging a dead horse working out a slipring system
Thx
Pebbles

[Flux]

For a normal site you don't need slip rings. The wind rarely goes through 360 deg. It may happen a few times a year and you can untwist the cable when it becomes necessary. There are a few very bad and turbulent sites where things do get tangled up but these are questionable as wind sites. If you use very free yaw bearings it does make matters worse and on some sites a turbulent gust might cause a 360 deg spin whereas a crude pipe on pipe yaw would be sufficiently damped to not to do it.

The idea of a stop is questionable, it can only work with a non furling scheme or one using vertical furling. Normally non furling machines are limited to small blade sizes.

For any horizontal furling machine a stop is asking for disaster, it defeats the furling when it hits the stop and you loose control.

There is nothing fundamentally wrong with slip rings but they need to be properly engineered, any half baked contraption with poor yaw bearings and no weather protection will fail here in our climate, it may be ok in some areas. Few have the knowledge or ability to build effective slip rings and avoiding them saves a great deal of future trouble.

Flux

[Beaufort]

Commercial slip rings are terribly expensive for what they do, however they've been well-tested in order to publish specifications.  In many locations variable wind beyond 180 degrees of span would be rare, and in my experience it tends to happen over a period of time with storms that blow in from an unusual direction.  I've seen some home-made slip rings here and some are done quite well, but as Flux said you have to know what you're doing to get good results over a period of time.

The drop cord scheme seems to work just fine for most people, just use cable that can take abrasion and flexing (especially in cold weather).  Make sure the tower cable is kink-free too...there can be rubbing on internal pipe weld beads for small pipe diameter/large cable sizes. 

[Pebbles]

Thx for the replies guys
I appreciate the helpful input, I have been working on a slipring set up but it is a lot more complex than most folks would think. My first mill wont have this feature, will take too long to get the slipring setup complete. It has it's implementation problems, not the least of which will be the bulk of the mast head/ mill head to go over the ring assembly and contain brush holders and brush assemblys without becoming an anchor at the top of the tower.
A friend of mine  runs a mill (5 years now) with a stop at due south and no furling and had no problems but he is running an intermediate shaft which doubles his gen shaft rpm . He is running 10 ft. dia blades , I have no idea why he doesnt have regulation problems but he doesnt , either really lucky with loads or the step up pulley had enough loss to derate it some ...not sure.
Thx again for the input
Pebbles

[imsmooth]

Let me know if this helps for a slip ring solution I use

http://www.mindchallenger.com/wind/wgpage10.html

[Pebbles]

Thx Imsmooth for the info/link
I have a quote request in to the distributer for 2 and 3 conductor models. Your link was very helpful, ( i dropped your wind gen info to a word doc on my desktop for easy future reference) .
Thx again
Pebbles