What not to do...

[TomW]

Well, it seems like we do not get very many failure reports. Not sure why other than it can be embarrassing to say I screwed up.

Well, I screwed up! I had a nice little zubbly conversion of a .33 horsepower 2 phase motor with 3/4 inch round 1/8 inch thick NEO's on the rotor that Zubbly built for me. I was flying a set of Arts nylon blades cut down to make a 75 inch 3 blade wind catcher.

I had mounted this conversion to the same yaw setup and tail I had used for my TDM setup which I flew for a couple years with no problems. The TDM had a 48 inch prop and frankly it sucked at power production.

This mounting setup consisted of a 1/4 inch thick aluminum plate about 8 inches wide and 10 inches long. The "yaw bearing" was a 1 inch floor flange bolted to the plate and 8 inch pipe nipple that extended down inside a 1.5 inch waterpipe mast. The lip on the floor flange was a near perfect fit inside the pipe mast.

Anyway I learned the valuable lesson that you Can Not trust threaded pipe connections in that type use. The pipe nipple sheared off at the area where it threaded into the flange and once that happened the power cables kept the mill attached to the tower and the blades hit the tower mast.

2 blades are salvageable the 3rd one has yet to be found. The hub is mangled and bent. The 1/4 inch aluminum plate is bent up at about a 45 degree angle between where the motor foot mounted and the floor flange mounting. The conversion hit 623 RPM just as it blew up according to my RPM logger on the laptop. The ammeter was pegged hard over and it had shoved the batteries up to about 16 volts. Just before this happened I had tried to brake it by shorting but I could not even get it to slow any appreciable amount so decided I may as well soak up some power. I guestimate the gust that took it was around 50 mph. There was no furling mechanism on this mill. I do feel that had the yaw setup held the rest of the unit would have faired OK. It seems that the motor shaft is bent now so I am not sure I can get it flying again soon.

Sorry, no camera so no pictures.

Just wanted to share this so others could learn.

TomW

[jmk]

 I am sory to hear about the misfortune. We all have bad days. The important thing is to forget the fustrations learn and get it fixed. There is alot to absorb on this board. Its got to be terible to get it up in the air and have a failer like that. Dan took pictures of one of his and I thought it was quite comical how he blacked out the eyes of all the people and aven the dog. I am going to attempt to raise a realy heavy machene. I hope mine does'nt come crashing down. Keep your chin up, we feel for you.

[Experimental]

   Sorry to hear of your problems Tom,

 But hope you can salvage some of it at least !!

  Was this associated with that 45' tower, you aquired??

  Most of us, only report our successes -- but we all suffer failures, I have a bunch of them, thrown under the work bench !!

   Lightning strikes, and smoked inverters have been a couple I reported here -- still trying to repair that inverter !! (probably a waste of time)

   Anyway, you have my sympathy, but perhaps it,s time to build a dual rotor -- really easy, and worth the work !!

   Best of luck to you, Bill H........

[nothing to lose]

Sorry to hear about the breakage.

Yes pipe threads are the weak point of a pipe. They are not intended to take any flexing/bending and can shear/break easily.

Hope you can fix that motor. Double check the inside I think. Make sure no magnets broke loose durring the impact. It would be terrible of course if you got it fixed then a magnet fly loose and ripe out a winding or something.

Good luck.

[cyplesma]

THANK YOU for sharing, I was in a hardware seriously considering using floor flange/nipple pipe type of setup for my yaw.

thank you for letting me know, I'm sure if someone was to watch the weight of their mill that setup would be fine, or use next higher size flange/nipple. As you said it worked fine for the previous genny you flew.

Or maybe the new blades just put too much torque on the yaw.

[jmk]

  Hugh recomends not to use threaded pipe in his book, or plans for this exact reason.

[Laylow]

I wish that more people would post failure reports, especially in developement.  A lot of times people just keep quiet until they get something that works and we are all supposed to believe that they did everything perfect the first time.  Unfortunately, that deprives the rest of us from some very valuable information.

In my opinion, pipe and pipe fittings aren't good for anything but plumbing but I'm just as guilty as anyone for using them.  Welding or brazing can help with joints and a little concrete can add rigidity and strength when needed but there is nothing you can do about the lack of precision.  I have yet to see a pipe fitting that was straight.  I think a good investment would be a large tap and die set.  Then you could make your own threaded connections out of shaft and material of a known strength and hardness.  With a little guidance from a drill press, all of the connections would be straight or at right angles.

I hope your able to salvage most of your stuff.

[MountainMan]

Trying to sort out the details on the nipple.  Are you saying it was an 8 inch long 1.5 inch diameter galvanized pipe nipple?

If so, wow!  Would have thought you could park a small elephant on that.

Was the nipple rusted at all from being out in the weather for two years?

thanks,

jp

[hiker]

i have the same setup on my old motorhome tom---

 worked great for some time now--but after reading your post --i will beef it up..

heres a shot of the old maytag alt[retierd]

[Ungrounded Lightning Rod]

I'd second that.

Question on the failure mechanism:  Did the nipple unscrew partially before it sheered off?

That's what I'd expect it to do.  You have nothing but the friction of the threads to keep it from unscrewing as the mill yaws and the wind and gyroscopic forces cause the lower end of the nipple to rub against the inside of the mast.  The further it unscrews, the greater the leverage on what remains threadded together.  Work it back and forth for months and eventually it'll loosen up, unscrew, and break off when it's nearly out.

If you insist on using a pipe flange/nipple combo, you can keep it from unscrewing by drilling and tapping the nipple or the flange for one or two setscrews.  (Since this one had the nipple and flange INSIDE the mast you'd put the setscrews inside the nipple driving out against the flange.  Then get out the monkey wrench and crank the nipple in good and tight before tightening the setscrews.)

[maker of toys]

screw threads are a stress riser, and the sharp-bottom profile of pipe threads are especially so. . . . combine that with the relatively thin wall of most pipe, and it's only a question of when fatigue will lower your mill for you.  I'd avoid threaded connections altogeather in favor of slip-and-pin or swaged joins.

gotta be careful with welds, too; I'm getting most of a nice 100' Rohn tower from a guy who lost his commercial 4kw grid-tie unit a few years back because a welded eye let go on one of his guy anchors and smashed the whole thing up.

(BTW: he reports that he actually made money with that unit, but not enough for him to consider putting up a replacement. . . . says 80 years old is just about too old to want to climb the tower to mantain the mill. . . .)

Tom-  you have my sympathy for your loss.

-Dan

[Norm]

 Tom,

    Sorry about the mishap....

   You can put pipe threads on a large steel rod

as if it were a pipe ....this sticks into the top

of your pipe mast instead of the nipple.

 A pipe sleeve welded inside that screws onto this large bolt...the whole works screws and unscrews as it yaws...limiting cables that wrap

around to keep it from unscrewing...now the only

way this can screw up is when its yawing counter

clockwise....??

  I don't have any this large but I've used a bolt and nut arrangement like this on my little

windmills when I was a kid...before I even knew

what a 'yaw' bearing was...just gotta use a lot

of grease or oil...same as any other bearing.

           Maybe this will be of some help

                   (  :>) Norm.

 

[richhagen]

Tom, Sorry to here about the loss of the mill, I'll bet you can get a replacement for the MIA blade from Art, but if the armature is shot and can't be repaired then it will be a bit of work to build a new one.  Best of luck with it, Rich Hagen

[TomW]

Well, guys;

After closer inspection I discovered the shaft on the donor motor has a double bend in the shaft. Zubbly explained that it is probably not worth much effort to salvage the motor.

I had my machinist buddy look at it and he felt that the 5/8 shaft could be straightened but due to the location [either side of front bearing] it probably would not stay fixed.

The 3rd blade is still MIA and it has snowed since so finding a white blade is unlikely until spring. I guess I am going to call this a total loss other than the 2 blades I have recovered that are intact.

I appreciate your kind words guys and you can be assured that anything I put up in the wind from now on will be over engineered and better thought out. And NO PIPE THREADED JOINTS

Thanks again guys.

Cheers.

TomW

[nothing to lose]

Since you still have 2 blades perhaps build a new hub for them and see how a 2 bladed  rotor does on the next build.

Just a bit curious how Arts blades would run as a 2 blader instead of 3 blades. Not curious enough to do it myself though. At least not yet.

[TomW]

NTL;

Been there, done that. Only on a TDM. The usual bad things from 2 blades lots of yaw shudder and not so good startup.

Just my experience.

Cheers.

TomW

[Laylow]

I'm still against pipe fittings but another option is to use schedule 80 pipe which is twice as thick or to use socket weld fittings which don't have any threads.

[Ungrounded Lightning Rod]

[] now the only way this can screw up is when its yawing counter clockwise....??

It screws up when it winds up against the stop in the direction of furling and then a gust comes up and it can't furl.  whrrrRRRRRRR POW!

[Devo]

Tom thanks for sharing your story. How many amps was the meter when pegged?

Just curious of the output as I have a few 1/3 to 1/2 horse motors around

Devo    

[TomW]

Devo;

Well this was mostly a TDM replacement and it was pretty good at doing 50 watts [4 to 5 amps] fairly steady into 12 volts and I estimate about 15 to 20 amps just before it blew up so my best guess is it maxed out around 250 watts into 12 volts. The meter was calibrated at 10 amps max so it was at least 240 watts when it came apart as the meter was hard over to the peg past the "10"

We felt it was an overall success considering the 3/4 inch by 1/8th inch magnets in it. I doubt we would do another of this size. Maybe Zubbly will chime in with his feelings on it as he built it.

Cheers.

TomW

[Norm]

  You're probably right, haven't had any experience with the big ones...never had to

worry about that ...another thing not to do

if I ever get to the bigger ones....thanks.

                    Norm.

[nothing to lose]

Ok, thanks.

I was thinking of cutting a 2 blader using my Art blades as a pattern to try this, but since it's already been done and not that well in use, I will skip that 2 blade project.

I know 2 blades have problems, but something I like about 2 blades anyway, just looks I guess? Also easier to mount 2 blades straight across than 120 degree angles for 3 blades. As I get the trailer house setup for a work shop I am planning a copy cutter, figuring it would be easy to cut a blade in a board swing it around and cut the other side, making 2 blades from one solid board. But that leaves me stuck with even numbers like 2 4 or 6. For odd numbers then I have to cut them apart and figures angles

Hey Tomw,

 I think awhile back I looked you up and your not that aweful far away. (being as I like to travel allot anyway). I think that was early this year and had to do with a rusty ranger truck. Anyway if you want a hand with building something or raising a new genny give a yell. Always looking for a reason for a road trip

Have van and inverter, will travel

[MelTx]

   Hey NTL do you make house calls as far south as Tx ? I got a couple of gennys that are giving me trouble...Every time I want to work on them I have to climb a tall tree and jump out on them. At my age its hard to do and still have any tools left in your pocket...But if I time the blade rpms just right there is only minor flesh wounds...But I think maybe there is an eiser way...

[nothing to lose]

Sounds a bit like East Texas. I mostly do West Texas now. I liked Van Horne, nothing there but cactus an me, but that was about 15 years ago the place might have grown (or died) by now. I was 20 miles East of town.

 Spent too much time around the piney woods of East Texas, nice place but most of my friends down there died off now. Construction and auto accidents got most of them.

Not much on jumping out of trees into blades anymore myself, kinda same reason I got out of construction years ago, tired of too high places with too small areas to stand or walk.

Does San Antonio still have a river down the middle and all the clubs down there still.

 Best Mexican food I ever ate was in a little restaruant on a tiny side street there.

I did allot of eating and drinking in that town for awhile. Mostly eating, not a very busy place but the food was great, best restaraunt in town back then.

 Course the Beaches were nice around Galvaston and Corpis Christie and down by the border was really good food in Brownsville too. Used to buy Teddy Bears in Houston, was a ton of good wholesale warehouses on Harwin Street for about anything else.  

 Texas, been there done that

Great place to live, has almost everything, not enough snow.