Author Topic: Hugh Piggott design, Not seen this before............  (Read 10916 times)

0 Members and 1 Guest are viewing this topic.

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Hugh Piggott design, Not seen this before............
« on: February 09, 2016, 04:10:55 AM »
I have 3off, 12 footer/3.7m diameter, Hugh Piggott design.

It has been windy here for the past 2 weeks.

Just popped down the field this morning, gusting 70 mph wind, noticed a little vibration on this No 2, just about to shut it down and waiting for a lull in the wind, as it was generating 30amps at 58vdc, when there was a crack! noise, the nose cone flow away.

 Safely shut down now.
This No 2 has my MkIV fiberglass blades that are twice the weight of my No1 with Cedar blades.

So it looks like I will have to increase the thickness of those two 18mm / 3/4 inch thick marine plywood boards that sandwich the blades.
 
Everything is possible, just give me time.

ontfarmer

  • Full Member
  • ***
  • Posts: 122
  • Country: ca
Re: Hugh Piggott design, Not seen this before............
« Reply #1 on: February 09, 2016, 05:14:43 AM »
Have you been using it for some time?  Good thing you where there
to shut it down. Hope the blades are not damaged.
Ontfarmer

kitestrings

  • Hero Member
  • *****
  • Posts: 735
Re: Hugh Piggott design, Not seen this before............
« Reply #2 on: February 09, 2016, 11:09:31 AM »
Very fortunate that you were keeping an eye on it and happened to be there.  The next thing to fail probably wouldn't be pretty.

Maybe go to a thin piece of sheet metal?

~ks

hiker

  • Hero Member
  • *****
  • Posts: 1525
  • BIG DOG
Re: Hugh Piggott design, Not seen this before............
« Reply #3 on: February 09, 2016, 12:10:51 PM »
steel plates 1/2" or 1/4.....
WILD in ALASKA

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #4 on: February 10, 2016, 12:54:04 AM »
Hi ontfarmer, this particular turbine has been up nearly 6 years.

 Each one of my 12 footers gets a good service, oil, paint, a few turns of unwind on the internal mast cable, and re-balance every 18 months or so.

Its coming down today, gin pole and 'tyfor' winch, that's if the sideways rain/sleet stops.


Hi KS, In heavy wind conditions I tend to keep an eye on my 'gals' a couple of times a day.

So I was very fortunate in spotting the nose cone spinning off centre, and starting to take shut down procedure. Very, very fortunate it was in daylight.

Found the 16 inch diameter nose cone, and it looks like it hit the blades.  :'(

I am not keen to put metal on the sandwich plates, as this will increase the nose weight, unless its a good bit of aluminium.
 Because the blades are already twice the weight of the cedar blades the turbine sits slightly nose heavy and is putting wear on the mast top spigot and the turbine head mast over tube. I suppose I could extend the tail tube or counter balance the tail, but personally I would like to keep the weight up the top as minimal as possible.

Hi hiker, As I have said I really do not want any more weight up the pole.

I like Hugh's design, as its very simple, cost effective, and very robust.

 But me putting fiberglass blades on has stretched the design a little bit, and that front 18mm ply has broken into 3 pieces, don't often see plywood brake like that.

 I will closer inspect later and see what's actually going on.
Everything is possible, just give me time.

kitestrings

  • Hero Member
  • *****
  • Posts: 735
Re: Hugh Piggott design, Not seen this before............
« Reply #5 on: February 13, 2016, 09:27:12 AM »
Quote
I am not keen to put metal on the sandwich plates, as this will increase the nose weight, unless its a good bit of aluminium.

While the Hugh design is proven to be pretty sound - your three are a good example - frankly I think the plywood hub plate is a poor chose for this piece.  It is predominantly it tension at high loading and steel or aluminum would be much better IMO.  There are examples of numerous fixed pitch machines using a metal plate with a lighter weight upwind plate sandwiching the blades that never had failures operating 30 years or more.  Sencenbaugh is the one I'm most familiar with; pretty bullet-proof.

I follow your concern about adding weight, but especially with aluminum this piece could likely be at or less than that of the plywood, much stronger and less affected by weather deterioration.

Good luck,  ~ks

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #6 on: February 14, 2016, 03:33:13 AM »
Thanks KS.

Yes I think a decent bit of aluminium is the way forward, so will put a hunt out for a triangle shape 540mm x 540mm x 540mm.

In the mean time I am doubling up the front plywood piece.

The nose cone is really lightweight so easily damaged, but I will put it back in its mould and repair.

The No2 blade has damage to its leading edge, but again repairable without to much difficulty.

However the PMG unit has sheared one of the 12mm stainless steel bolts and the others are bent, so its a PMG off the mast and a rebuild with new studs.

Just takes up my precious time, but with this winter sideways cold rain and gloomy weather conditions, the ground is super waterlogged, so the turbine will have to wait a few weeks until the ground is suitable for my car and trailer with the crane on.  :'(   
Everything is possible, just give me time.

ontfarmer

  • Full Member
  • ***
  • Posts: 122
  • Country: ca
Re: Hugh Piggott design, Not seen this before............
« Reply #7 on: February 14, 2016, 04:41:15 AM »
Certainly a scenic view from the picture!

kitestrings

  • Hero Member
  • *****
  • Posts: 735
Re: Hugh Piggott design, Not seen this before............
« Reply #8 on: February 16, 2016, 04:54:08 PM »
"PMG" ?

Is that a blade that you previously repaired?   It looks like a chip in maybe some sort of filler?

Why can't someone make a better grade of stainless?  It galls terribly, and it is pretty soft.  Neil, my friend has pretty much gone to grade 8 hardened fasteners in place of stainless.  I've tried using, what is it 325(?), it seems a little better than the local hardware stock, but still room for improvement.

~ks


joestue

  • Hero Member
  • *****
  • Posts: 1398
Re: Hugh Piggott design, Not seen this before............
« Reply #9 on: February 16, 2016, 09:27:51 PM »
use 400 series nuts on 316 bolts.
 
i did find some mention of specialty alloys used to make stainless hinge pins for bridges.. but seems to me if it worked, more people would be using it.

joestue

  • Hero Member
  • *****
  • Posts: 1398
Re: Hugh Piggott design, Not seen this before............
« Reply #10 on: February 16, 2016, 09:52:03 PM »
this paper is pretty interesting but it mostly concerns specialty alloys.

it appears that 304 on 304 is the absolute worst combination.
416 on 416 looks like a reasonable option.

https://www.nickelinstitute.org/~/Media/Files/TechnicalLiterature/ReviewofWearandGallingCharacteristicsofStainlessSteel_9006_.pdf

MattM

  • Sr. Member
  • ****
  • Posts: 406
Re: Hugh Piggott design, Not seen this before............
« Reply #11 on: February 17, 2016, 12:05:55 AM »
Every version of stainless - of which it's a subjective argument just what stainless steel in fact constitutes - will have its own unique ionic transfer quality.  It would take serious testing on expensive equipment to get the perfect match.  Stainless in most forms isn't soft, it's brittle.  Very different quality.  Terrible fatigue tolerance.

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #12 on: February 17, 2016, 12:31:04 AM »
PMG.

Permanent Magnet Generator.....

That chip out, is the Gel coat, probably a little thick just there.
That's the blade join seam, which is always a problem getting the 2 half's to adhere properly. I even wrap a very fine woven cloth glass fibre down the edge and brush gel coat, but its never always good at bonding once the moulded blades half's have set.

Now I have a good stock of Cedar wood, I will leave the Fiberglass stuff to others.
Everything is possible, just give me time.

Neil

  • Newbie
  • *
  • Posts: 35
  • Country: ca
Re: Hugh Piggott design, Not seen this before............
« Reply #13 on: February 17, 2016, 06:19:39 AM »
Clockman, you can always try some Russian plywood, it has alot of layers and is very stong.

Neil

midwoud1

  • Sr. Member
  • ****
  • Posts: 341
  • Country: nl
  • There are more chiefs than indians
Re: Hugh Piggott design, Not seen this before............
« Reply #14 on: February 17, 2016, 10:25:37 AM »
Problem with plywood : Half the thickness  is crossgrain.  Normally  nice material to work with.

Bruce S

  • Global Moderator
  • Super Hero Member Plus
  • *****
  • Posts: 4521
  • Country: us
  • USA
Re: Hugh Piggott design, Not seen this before............
« Reply #15 on: February 17, 2016, 11:10:09 AM »
ClockmanFRA
To be honest , I've not built a 'mill that large (can't due to city living and safety).
I would like to ask a few questions before you decide.
1) How old are those plywood plates?
2) How are the other two holding up?

IF it failed in 1 short year, then I would look for a longer term solution, IF they are 3+ years old then maybe the plywood is an OK solution.
IF the other 2 are just as old, and they're holding up just fine,,, then maybe it's a fluke or a section of that part of plywood that was internally weak.

Just my observations , could be totally wrong on this.

Cheers;
Bruce S
A kind word often goes unsaid BUT never goes unheard

richhagen

  • Hero Member
  • *****
  • Posts: 1508
  • Country: us
Re: Hugh Piggott design, Not seen this before............
« Reply #16 on: February 17, 2016, 12:14:43 PM »
since the tension forces on the plywood hub plates will increase in proportion with increasing blade density for a given speed, and since the fiberglass blades are significantly heavier than your cedar blades, if you are replacing the fiberglass blades with cedar blades, you may not need to reinvent the wheel as the new part might outlast the blades you put back on.  While a material with a greater tensile strength to mass ratio, everything else being equal would be favorable, it is hard to beat the ease of the marine plywood part in terms of ease of fabrication.
A Joule saved is a Joule made!

kitestrings

  • Hero Member
  • *****
  • Posts: 735
Re: Hugh Piggott design, Not seen this before............
« Reply #17 on: February 17, 2016, 01:02:53 PM »
Thanks joestue, yes "316" is what I'd meant to say; seems to be better than the 18-8 used for so many fasteners.

Quote
However the PMG unit has sheared one of the 12mm stainless steel bolts...
  Sorry to be missing something, but is this one different than the other two?  Aren't they all PMGs?

Aluminum is pretty easy to work with too...

~ks

hiker

  • Hero Member
  • *****
  • Posts: 1525
  • BIG DOG
WILD in ALASKA

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #19 on: February 18, 2016, 01:18:36 AM »
Neil.... Russian plywood.?

Midwoud,........ I am doubling up the 18mm thickness.

Bruce..... 1....This turbine has been up 6 years, No1 nearly 10 years and No3 3years.   2. ....... Last inspection, down for fine balancing, was last year. They look okay from the ground just now, but I will do a 'look see' on the other two when the weather gets better.

KS........ Here's some pics.  One of the main stud bolts has sheared, missing. The other studs/bolts are bent, so the PMG will have to come down for a rebuild.  All my Wind turbines are the same size and use the same main bits like the 5 stud Van hub, coil stator, magnets and the discs, frame etc.
The only difference is the blades.

The remains of the front plywood board.
a couple of possibilities.       ......  The so called marine plywood wasn't' marine plywood. ........The plywood on the fractured areas seems very wet.......... I do have some marine plywood which sits in water, bottom of a small boat, and doesn't de-laminate even after nearly 30 years.

Hiker... I can not get that Facebook link....

« Last Edit: February 18, 2016, 01:28:53 AM by clockmanFRA »
Everything is possible, just give me time.

Neil

  • Newbie
  • *
  • Posts: 35
  • Country: ca
Re: Hugh Piggott design, Not seen this before............
« Reply #20 on: February 18, 2016, 06:17:25 AM »
Clockman, I have used this plywood for years and never had any kind of problems.

Product Properties

Russian Birch Plywood is made by gluing together a multiple plies of birch veneer. There is always an odd number of veneers and each ply is at a right angle to the one below, which gives the material superior stability and strength. The type of glue and the thickness of plywood determine the suitability of a sheet for a particular application.

Baltic Birch Plywood may be used inside and outside. It is graded for exterior or interior use depending upon the water resistance of the glue.


Neil

MattM

  • Sr. Member
  • ****
  • Posts: 406
Re: Hugh Piggott design, Not seen this before............
« Reply #21 on: February 19, 2016, 10:00:55 PM »
You could always throw some fiberglass cloth between two thinner thickness marine plywood and bond them - at forty-fives to the grains - with an appropriate marine-grade epoxy.  Not all epoxies are suited to the job.

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #22 on: March 06, 2016, 09:01:26 AM »
Thanks Neil, I will keep my eyes open for some of that. However, I have put a small 6 inch by 6 inch of my latest so called marine grade ply in an open water tub and await the results.

MattM, sounds a good idea with the matt, but with the multiple choices of resins and epoxy types, getting good marine grade and knowing its marine grade is getting difficult in these times.

Photo shows the PMG being rebuilt.
The hub and bearing unit is back on with a new supply of internal grease, with the first magnet rotor disc attached, along with new, 11inch/285mm long,  1/2inch/ 12mm diameter stainless steel bolts.
The vinylester cast 1/2inch/12mm thick coil stator is ready for installation, and then the other magnet rotor disc can be fitted.


Everything is possible, just give me time.

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #23 on: April 23, 2016, 05:47:00 AM »
My No 2, 12 footer/3.7m, is back up and running.

The boys, 9 and 13, have reached a useful age.

The eldest, 16, helped me re-fit the blade complete unit, ....... and I needed him too.

Everything is possible, just give me time.

ontfarmer

  • Full Member
  • ***
  • Posts: 122
  • Country: ca
Re: Hugh Piggott design, Not seen this before............
« Reply #24 on: April 24, 2016, 12:43:23 PM »
You have a lot of help!

 What did you use for the repair?

Did the same blades go back on?

clockmanFRA

  • Sr. Member
  • ****
  • Posts: 475
  • Country: fr
    • Echorenovate
Re: Hugh Piggott design, Not seen this before............
« Reply #25 on: April 26, 2016, 01:06:57 AM »
Hi ontfarmer,

Yes the same blades went back on after a little repair work with epoxy and a new coat of paint.

I made anew mounting back disc, and a new front mounting triangle plate, but this is doubled up, ie, its now 36mm thick instead of the normal 18mm marine ply.

Testing, I put an offcut of the ply into one of my water troughs, I will keep an eye on it. 
Everything is possible, just give me time.

mbouwer

  • Sr. Member
  • ****
  • Posts: 311
  • Country: nl
Re: Hugh Piggott design, Not seen this before............
« Reply #26 on: February 12, 2017, 05:39:28 AM »
Clockman,

Have you seen the photo on Hugh Piggott's blog?