Heavy blades = Heavy tail?

[clockmanFRA]

I have 2 Hugh Piggott's design 3.7m (12 footer). No 1 has Cedar blades, but trying to source good thick Cedar in UK and France is very difficult. (My laminating was not a success).
No 2, has my glass fibre blades, an exact copy of  Hugh's design and from his contribution document, Engineers Without Borders, "Fibre glass wind turbine blade manufacturing guide".  The 3 blades total about 12.4kg which is about nearly double the Cedar blades.
No 3, is now under construction and I will use glass fibre again, but with modifications I can reduce total weight of these blades to approx 11.1kg.
No 4, collecting parts.

My problem. No 2 when at rest, is blade heavy and the whole turbine assembly is sitting forward so that the outer yaw pipe is in constant contact with the inner yaw pipe that is attached to the mast/pole. Over the past 9 months this has been rubbing and polishing a ring, (mast yaw inner is 8mm wall and outer yaw wall is 4mm, so still has a good life). And maintenance/lubrication is constantly required.

Do I add weight to tail?. Hugh's recent update now say's 5Kg for tail of the 3.6m (12ft) but then with added weight will the self furling tail have problems ??

Any advice would be very welcome.  

[fabricator]

I depends where you are furling now, if you have room between your peak power output and smoking the stator to furl later then the extra tail weight won't be a problem.
But if you are right one the knife edge between peak power and furling then yeah, extra tail weight could make the difference. You could make the tail hinge degree less, if you are using 15 degrees now you could go to 12 degrees to lessen the impact of a heavier tail.

[zvizdic]

If I am right 2x8 is available in UK. Use  any wood  painted with fiberglas it be OK.

[Flux]

With a furling system it is near impossible to balance the weight of the alternator and blades against that of the tail. Even if you can do this below furling ( and that will involve balance weights in strange places) it will all go wrong as soon as it furls.

The yaw bearing should be able to deal with this and as long as the unsupported part of the tower above the guys is rigid enough to stay vertical I really wouldn't worry about it. With the intended blades it will not be correct and I doubt that your blades have made the problem much worse,

If you increase tail weight you will have to reduce the hinge angle or it won't furl at the correct wind sped. Reducing the hinge angle makes the whole thing much more critical on the tower being truly vertical and as you won't be able to balance all the forces in the various planes you will probably come off worse.  If you do set out to balance all the forces independently before and after furl you will have a string of heavy balance weights in various planes and it will weigh a ton, I have never seen it done and can't believe there is any benefit.

Flux

[Ungrounded Lightning Rod]

Flux called it on why you don't try to balance by increasing the weight of the tail.

If you DO want to balance it better, though, you can always add a counterweight behind the turbine that is NOT part of the tail assembly.  (On motor conversions, if the shaft and bearings can handle it, you can get much of this by mounting the motor with its center of gravity a bit behind the yaw axis.)  Watch your clearance with the tail as it furls and try to avoid throwing a lot of extra turbulence at the tail vane.

Some friction on the yaw axis may actually help the mill track in turbulent conditions (although fluid friction, i.e. grease, is better than rubbing friction, which has the static/sliding dichotomy and may stick and not track light winds.)

With pipe-over-pipe bearings the longer the pipe the lower the friction for a given amount of off-center weight.

[clockmanFRA]

Thank you guy's for your wisdom.

I am of the philosophy that, "if it isn't broke don't fix it" brigade, however that shiny ring on the mast/pole yaw inner tube is definitely showing signs of  wear and keeping grease on it (a vertical surface) is not possible for long.

I have also noticed that No 2, turbine, (the heavy blades) in very light winds cracks and groans when turning into the wind, sort of telling me that grease is required, (about every 2 months).

So, I will try to get No 3 blades weight down during the manufacturing process, and install a grease point on the inner yaw tube/mast that puts grease onto that shiny wear area.
 Hmm have to think about that. Especially regards the internal 3 cables/wires do not foul any internal protrusion and some sort of tube that can take the grease up, so I can just pump grease at the base of the mast/tower.

Also incorporating Underground Lightning Rod's idea with lengthening the yaw pipes sounds very sensible.

[fabricator]

Or, you use something like Teflon or UHMW or Delrin for your bearing surfaces, I used Delrin on my 17" machine and have seen no signs of wear in over a year.

[zvizdic]

No more simple yaw bearing for me.

My 6' got dray yaw and squealed so my 10' got real bearings in a yaw bearing.

[jonpowers]

Posted by: clockmanFRA
"the outer yaw pipe is in constant contact with the inner yaw pipe that is attached to the mast/pole. Over the past 9 months this has been rubbing and polishing a ring, (mast yaw inner is 8mm wall and outer yaw wall is 4mm, so still has a good life). And maintenance/lubrication is constantly required."

To make two nested pipes a better yaw axis:  Above the bottom of the outer  pipe and near the top drill two sets of three equally spaced holes on the outer pipe.  Weld three nuts to outer pipe at the two locations.  With one lock nut threaded on to a (total of 6)  brass bolts screw them into welded nuts and adjust for a small clearance to the (in this case stationary) inner pipe.  Grease it up and that's taken care of.  At the top of the stationary inner pipe put on a plastic disk or a three piece thrust ball bearing for the outer pipe and turbine to rest on.   This has worked for me in the past.

Jon Powers

[fixitguy]

i think with pipe in pipe design its just a matter of time be fore it wears to the point your describing.theres a lot of stuff depending on that crude bearing system.
my 10 footer has a 2 roller bearing design...only on my tail would i think of a pipe system.

[clockmanFRA]

Interesting.
Need to ponder on your solutions.

I would still like to keep the yaw pipe bearings simple.

[Flux]

It's all a matter of what feels right. Those involved in engineering will probably run a mile from pipe on pipe bearings, properly engineered yaw bearings last forever ( or nearly so) require decent engineering and have some disadvantages of less damping of the yaw axis.

Pipe on pipe is simple well damped and lasts long enough to be practical for many it is a means of doing the job when proper facilities would rule out more complicated solutions. If you want long life and silent operation you need to keep greasing, if you are not so fussy it will still work for years left to its own devices but it will squeal and eventually fail and need replacing.

There is a reasonable compromise where you keep the pipe on pipe but add a taper roller or ball thrust race to support the weight. If you have enough facilities to engineer this half decently the same bearing will prevent wear on the top of the pipes, the loading at the bottom is so low it never becomes an issue. To work the bearing must take the side loading as well as end thrust, if you just use it for the thrust then it won't reduce the side wear on the pipes.

If you have a lathe and other facilities you have more choices and a nylon or similar plastic bush at the top where the wear takes place will make a big improvement. If you have the lathe then the taper roller solution to take thrust and side force on the tubes is probably the best compromise but with any form of bearing you have to keep water out or it will be far more trouble than the simplest pipe on pipe arrangement.

Flux

[Scott]

I don't know if this is relevant but what I've done in the past is weld a tapered bearing race to the top of my tower then drop the bearing in and place the mill on top of that.

[clockmanFRA]

Thank you very much for all your replies.

Thankyou Flux for your wise common sense approach.

I do have full machine shop facilities, with 2 ton turret lathes, down to 6mm collet lathe that holds material at 0.20mm diameter. .. And machine mechanically from 30mm diameter down to + or - 4micron.

Over the decades, as wisdom and age grow, I look at things in a much more simpler concept, "keep it simple keep it sweet", "don't over complicate and make work", and "with something good, be carefull, you tinker at your peril".

For me Hugh's wind Turbine is one of those "simple and sweet" designs and very efficient for what job it has to do.

So, after due consideration and all your comments i will leave the design of the Yaw pipe inner and outer as is. But run a small tube (brake pipe size) up the tower so that i can lubricate the offending parts more frequently from the ground.

Again many thanks.
now where's that grease gun