How long, MTBF

[fcfcfc]

Hi:

Just a quick question... has anyone put together an MTBF for these HAWT's of the home brew variety..... This includes all failures no matter what the cause... or to put it another way, given a proven design and a good job putting it together, how long can an individual expect before they need to mess with it..

If hermetically sealed bearings are used, should they really need periodic maintenance..??..

Happy new year...

.....Bill

[wooferhound]

We just completed a Month Long Poll in September asking . . .

How old is your Longest Lasting DIY wind generator ?

Here are the results...

http://www.fieldlines.com/poll/1219198709_pYwubLte

[Flux]

Probably impossible to answer your question, site conditions will vary so much if nothing else does.

My experience is that bearing life is long if you can keep moisture out, in a dry climate this may be no issue at all. In a damp or coastal area things may be very different and failures may occur that just don't happen in better climates.

Your question is partly self defeating as machines maintained regularly have low failure rates. If you never maintain it or check anything then minor issues will become failures.

I have never had a machine running longer than 10 years because technology moves on and new ideas need trying, but it looks as though blades should last at least 10 years ( but will need maintenance). Bearings will possibly last 10 years if you can keep moisture out. There are unfortunately a lot of dubious bearings available on the present market that may only last a few months so you largely get what you pay for.

Stator burn out? I haven't experienced it, but I had one stator winding break down ( motor conversion type thing but built from scratch)due to water in the windings.

Rectifier failures not infrequent using 35A bridges, unknown using decent stud mount diodes.

Tail mountings and furling mechanisms need regular maintenance to avoid failure but my mechanisms are different so not much guide to you.

I have not yet found the limit of life for neo magnets but I do completely pot them when possible. I have a feeling that unprotected magnets on nasty sites may have very limited life.  Similarly steelwork unprotected by regular painting or something else on some sites will have a short life (years).

I think it was Mick Sagrillo who said the life of a machine depends on the effort invested in it and it is very true.

Flux

[fcfcfc]

Thanks.... missed that poll...

[fcfcfc]

Thanks for the detail... The poll suggests that the 1 to 3 year area may be somewhat representative of a midpoint... just curious really ... my design in planning is a VAWT, BUT, they share allot of similar parts and loads and the exposures to the weather are of course the same.... on the steel outside issue I agree, unless you use Aluminum and Stainless where appropriate, you will be doing seasonal scraping and painting. One could infer as you suggest, saving up just a few more dollars to invest in the right places before you begin, could more than "pay" for itself over and in "time"...

Thanks....

.....Bill

[tanner0441]

Hi

Just an observation.... A Vertical shaft will funnel water into the bearings where a horizontal shaft will then to allow it to drip off.  So mean time to failure for bearings will be very different.  Also I can't see the mean time failure even applying to something that does not have a mass production program, and is assembleled without any form of control.  Batch testing doesn't work when you only build one.

Brian

[tanner0441]

Ooops

will tend to allow it to drip off.

[scoraigwind]

Small wind turbines seem to take a delight in confounding any attempt to make a really trouble-free product.  This applies to the commercial ones too, and even the most expensive models can fail early for no apparent reason.  The main difference is that the well built ones are easier to fix and more likely to survive and fight on.  This applies equally to homebrew turbines.

Sometimes you will get a machine that runs for years without any attention at all.  The one behind my house (an AWP with wooden blades made locally, and a heavy duty tail I built for it) has not been looked at close up since February 2006.  It sounds fine to me.  I would probably grease it if I could climb it (which I can't as it is 85 feet up and there are no steps) but taking it down is more effort than I can be bothered with until it sounds sick.

Other ones start after 2-3 weeks with failed bearings and magnets rubbing stators and coils burning and diodes blowing and all sorts of grief for no apparent reason other than to make one feel small for thinking one can make a reliable wind turbine.

[fcfcfc]

Hi:

Yes, I guess the variability in materials times the variability in environments all submitted to mother natures whims spells an inconsistent outcome....

Even in doing the solar thermal "stuff", to build it to stand up long term outside, is not an easy challenge...

Every detail and quality point must be looked at closely, because if YOU don't, Murphy will..

I am behind on my VAWT... no surprise... I have the skeletal frame built on the small prototype (2' x 4') but I have had no time to put the AL skin on it and pursue the wind tunnel tests... maybe in 09 here I can get the prototype turbine finished and tested...

.....Bill

[fcfcfc]

Hi:

Yes it would.. I plan on having a horiz. separator shield with a rubber gasket for vertical weather protection. It won't protect from the side as such, but it should stop the blatant vertical drop "stuff" be it liquid or solid...

Thanks...

.....Bill

[boB]

What about all the old Jacob's machines around still working ??

Are these machines just a few of the many that were built way back when

and are the few that still work, or are they still around because they

were built well ?

If they were build well, what is the reason they still work ?  New

bearings are in them I imagine too.

boB

[Flux]

They were well designed and well built. They were pitch controlled and the original bearings were specially selected and I seem to remember that Jacobs did something to the lubrication as the sealed bearings of that era was very doubtful.

These machines had commutators and brushes but even so they went for long periods with little maintenance. I am sure many went by the wayside after the grid replaced them, those that remain have probably had better maintenance or have been rebuilt by those who appreciate their qualities and are prepared to look after them.

If you start with a well designed and built unit then survival is more likely, in real terms they would have been incredibly expensive and the much cheaper Wincharger and other units would have been far more common but fewer will have survived. A bit like comparing a Bergey with its Chinese look alike.

Flux