Hugh,s 4 foot on a G.M Alternator

[mitcamp]

Since I had a pile of G.M alternators laying around, I decided to put them to use as a bearing for Hugh,s 4 footer. I removed the original G M stator and pressed the claw off of the rotor to save on the weight. I removed the rectifier assembly and installed 2 bridge rectifiers under the rear cover. It is easier to get to them if there was a problem.

I put the alternator back together with the 4 original bolts using spacers to make up the difference after removing the stator. This leaves a 1/2 inch gap. I used metal tape over the gap to keep the weather out.

I used a 9 in. disc 3/8 thick with a 7/8 hole in the center for the magnet rotor.I glued 8 magnets 2x1x1/2  down and then put the rotor in a mould. Using west bend epoxy I covered the mags, leaving a 4 in. island in the center. This rotor goes on the alternator first,with a spacer to keep it from rubbing the alt frame.





The stator was cast with hughs specs of 85 turns of #16 on a 3/8 former. The stator goes on next and is held in place by metal extensions attached to the original eye bolt lugs on the front of the alternator.

I used a second 9 in. disc on the front for 2 reasons, to complete the flux path for magnets and to attach the blades with short spreader bars. The spreader bars are just long enough to clear the bolts holding the stator.





I used a front wheel assembly from a dodge shadow to act as a yaw bearing. The axle hole allows the wires to go down the center of tower or pipe. In my case I use the hole to accomadate my slipring tower. The sliprings are insulated from the 1 in pipe with a teflon insert. You could just use the axle hole to run your wires down with or without sliprings.





You will need misc spacers on the alternator shaft to keep a air gap between the rotors and stator.

I have built a dozen of these 4 footers for cottages in the outback to charge batterys. Great for 5 to 20 amps depending on the wind. Hope this can shorten your build time.  Mitcamp

[willib]

mitcamp did you use any type of arbor on the magnet rotors?

nice use of available stuff

[mitcamp]

Willibur, I am using no arbours. In order of assembly(1) spacer

(2)rotor with mags

(3)pipe spacer(keeps the 2 steel disc apart,also determines the air gap)

(4)front rotor with spreaderbars for blades,no mags on this disc.

(5) washer

(6) Nut

As you can see in the picture, the shaft is all used up. No room for the second set of mags on the front disc.

This above machine does not have great braking ability, so I have devised a easy build for a 4 foot dual rotor,8 mags on each disc. I will post it within the next month. I have one flying now with 3 foot blade( 6 footer) It brakes better and makes a bit more power.  Mitcamp

[downwind]

I would like to pass on some information based on experience. A number of years ago I built a genny very similar that what you are doing. Though I can't tell from the pictures, it looks as if you are using 1/4 inch stock for the spreader bars. I did the same and paid the price the very first time the genny yawed in a stiff wind.  The bars bent and a blade went into the tower.  Even doubling it did not stiffen it enough and I ended up going with heavy square tubing.  It ran well for several years until the bearings finally gave out.  You just can't imagine the force placed on things when those blades are forced into changing axis during a yaw.  I hate to see you lose nice blades.  Best of luck!  

[Flux]

That was my thought as well, I would expect those flat bars to bend.

Otherwise it is a good idea. With the extra disc to return the flux i would have thought that hugh's winding would cause it to stall with the blades at 4ft diameter. If the extensions increase it to nearer 5 ft dia it will probably be ok. I made one like that and it takes 5ft 6" blades very nicely in a low wind area.

Flux

[mitcamp]

Hi downwind  My spreaderbars measure 8 3/4 in. long 1 in. wide and 1/2 in. thick.  From the edge of the disc it measures 7 in. I have a dozen up for 2 1/2 years and had no problem so far. I cant imagine bending one as it is difficult to correct the tracking by puttig them in a vise. Thanks for the information and I will keep my eye on them. Mitcamp

[mitcamp]

Flux, The extensions increase the diameter to 5 ft 7 inches and are 1/2 in thick, 8 in. long and 1 in. wide. I confirmed the measurements in  a previous reply.

I mentioned in my post that I was adding a 2nd disc with 8 magnets to Hughs 4 foot machine.

Would you suggest a alternative wiring scheme, other than hugh,s 85 turns of # 16 for the added rotor. I didnt have time to experiment much,  I just added the extra rotor and put it up last week.  As usual I havnt had enough wind to test it. You mentioned stalling.

On a second note, I have finished my 17 foot Dan B clone with 16 mags 3 x 1 1/2 x 3/4 on ea disc and it is ready to go up on my 100 ft tower. This time I have 3 wires down to my batterys, and rectified with large stud diodes. I will post a diary in the next 10 days with a few pictures. I am waiting on a crane to hoist it into position. thanks  Mitcamp

[Flux]

At 5ft 7" I think the 85 turn winding will be ok. It would stall badly at 4ft.

With the larger blades it will run at lower speed and that should compensate for the increased flux from the second disc.

I assume you only have magnets on one disc. with both discs having magnets it would need a different winding and even larger blades.

Mine is on the end of a very long cable, possibly with very short and thick cables it may be a bit near stall. Your blades look as though they may be a bit faster than Hugh's. I think it will be just fine, nice and quiet, good in low winds and still acceptable in high winds. If it looks to be stalling try adding a bit of thin cable to the line.

On a decent site your 1 x 1/2" blade extensions will probably ok, mine is on a very bad site with lots of trees.

Flux

[mitcamp]

Flux, you say:

"I assume you only have magnets on one disc. with both discs having magnets it would need a different winding and even larger blades."

Matter of fact.I would like to try 2 disc with magnets on each disc. Give me your best idea on # of turns and size of wire.  Would a 7 foot diameter be compatable for this machine.  

The only problem I have with this single disc with magnets is: When you put the brake on (knife swich style) it still turns quite fast in a windy location. Would the second disc with magnets slow it down better.    Mitcamp

[downwind]

Sorry, the photo was deceiving, it looked thin.  1/2 inch should do very well.  

[tecker]

Might be intresting to power up the armature  with the a regulator and kick on the alternator in a stiff wind . Three or four standoffs is  a good idea for a cast stator

but I like that idea.  Very good idea.

[Flux]

I have built one with 8 magnets on each disc for a 24v system using a buck converter and intended for a 6 ft prop. I think the coils were 100 turns of 2 in hand .9mm.

For 12v you could probably use 55 turns 2 in hand #16. Probably it will stall with a 7ft prop without the converter but a bit of series resistance in the line should sort it out. If you are in a good wind area then reducing to about 45 turns would likely give a better winding but with the loss of some low wind performance.

I suspect it would hold a 7ft prop braked under most conditions. This is something I am always suspicious about, it really takes a very powerful alternator to stay braked at all wind conditions and even more so to guarantee to stop in any wind. If you have any line resistance it will make this problem worse.

I think you are right, the original winding that Hugh intended for the single rotor 4 ft will probably have too much resistance to stop with a 5ft 7" prop.

Your spindle scheme will work but using 8 magnets on a 9" disc gives a stator with a hole that is probably too small to take the usual hub and allthread construction. I built my own hub. You could try the trick that Dan mentioned on the Guemes Island report with the magnets mounted the other way round. May not be quite as effective in the use of magnet material but would simplify construction. I used the metric magnets but the 2 x 1 x 1/2 N40 work out very similar.

Perhaps Dan will give more details of that machine, I think it was 6ft.

Flux