10' Generator Questions

[bzrqmy]

I am in the process of assembling my 10' generator.  I have a couple questions I would like to run by the group.

1.  I bought the magnets with the holes.  If I press a 3mm roll pin into the  steel rotor and put a coat of epoxy on the bottom, do you think this will be sufficient to hold the magnets in place?

2. I want to do some bench testing to check performance and establish a baeline at different rpm's.  What is a good way to measure RPM's?

3.  Any suggestions on a bench test rig?  I figure I can put a hand crank, or turn with a drill, but this would be for short runs.  Is there any advantage to running this at say 500 Watts for a period of time for heat dissipation testing?

I am interested in doing this testing as I really don't have a tower to put this on yet.  Spent all my extra science experiment money on building the generator.  I did get an offer for some sections of 2" pipe, hopefully enough to erect a 15-20' test tower.  I am looking at building a 40' tower out of 3" sched 40 pipe soon.

The ground has thawed up here in Michigan and we have a couple months of the mud season to deal with before we can think about erecting towers.

Will be assembling soon, pictures to come in my diary.

[Flux]

Yes the magnets with holes fitted with roll pins and a decent structural epoxy should hold the magnets if you are in a dry climate and don't think you need extra weather protection.

For speed an optical tacho or measure frequency.

I am not sure it is worth going to a lot of trouble for bench testing an existing design. I doubt that anyone knows what the cooling is like on a mill compared to bench testing. Experience seems to indicate that these things survive at about 700W with wind cooling and wind duty cycle. I am sure that with continuous load on a bench test you will fry it at a much lower power than that.

If you want to bench test to get characteristics for interest then fine but unless you have a lathe or similar you are in for a lot of probably pointless work. You need a variable speed motor, some means of reducing speed and a dynamometer mounting if you want to measure power in ( and without power in the thing is virtually pointless). Lots of work.

Flux

[behoof]

Hi bzrqmy,

Where the heck in Michigan are you that the ground has thawed? Sure isn't thawed here by me in the Thumb Area, had to bust through the frost to bury a critter the other day. And you sure are correct about the mud season.

Michigan's Seasonal Chart

Winter

Mud

Spring

Summer

Mud

Fall

 and around we go again.

Best to you on your project, sounds pretty nice and yes on the roll pin idea.

Later,

behoof

[scoraigwind]

the best way I know to bench test is to hang the whole thing off a live wheel hub.  Make an adapter out of plywood in place of the blades and containing a hole pattern that fits onto the drive wheel hub.  Put the axle of the vehicle (truck etc) up on blocks and remove the wheel and replace it with the alternator rotor.  Let the stator and frame just float - keep it from turning with some loose arrangement.  It may wobble quite a lot. Take time to make it run as true as you can, and that will be plenty.

[bzrqmy]

I am jut north of Jackson.  We are up to our hips in mud right now.  The ground may still be frozen down a foot, but the surface is pretty sloppy.

[ghurd]

Sorry about your critter.

I chopped through frozen N.E. OH mud on Thursday for the same reason.

G-

[aerospot]

An option for running a test at variable RPM would be to fashion a V-belt pulley where the blades would be and connect via V-belt to a variable RPM electric motor.

I'm interested in viewing your photo diary. I'm in the process of building an alternator for a 10' mill.

I fabricated my winder and made the 9 coils yesterday. I've also made the mold base and have drawn lines representing the coil placment and magnet travel.

I am interested in an alternative to using talcum powder as a filler. Could you use something less expensive and more availiable such as 'Durabond'? This is a powder used in finishing drywall.

I have purchased as a kit from http://www.magnet4less.com/

It came with 25 - 1" X 2" X .5" magnets, 14 guage wire, 3-Phase rectifier, Blades & Hub. The blades look to be good quality and are quite affordable compared to others I've seen.

I have taken lots of pictures and will document my progress as I go along.

Dave