dc motor mounts vs direct shaft linkage

[iFred]

Hey Guys,

I got some nice industrial size/type half and one horse power dc motors a couple weeks ago. So I'm thinking of building them into wind turbines. The question is should I run the blade directly off the shaft or should I make a frame with a new bearing mount below or in front and mount them this way. My concern is the issue of the bearings in the dc motors having to taking the punishment of torque forces. Does it really matter? How often would the bearings have to be replaced anyway?

Thanks for your suggestions.

[stevesteve]

Good question iFred,

I have just bought a 90V DC PM motor (rated at 1300rpm so I think it should be fine to charge 12V - similar to the Ametek motors?). Nice screw-ported brushes so they'd be easy to change but what about the bearings?

I notice most folk using the Ametek PM tape drive motors seem to go for directly mounted blades. How long do those bearings tend to hold outat they are presumably not designed for the thrust comming down the rotor shaft?

[picmacmillan]

i fred..havent heard from you in a while ..i'll stop by as i am in town....on your question...i have bought 2 of zubblys motor conversions(real nice by the way), and he told me to just attach the blades to the shaft....he is flying his machines this way...i realizethere would be large forces in the horizontal plane that would not be normal for the bearings, as the bearings usuall force would be in the vertical plane from a pulley or what not..i dont know what the time frame woiuld be on the bearings in this fashion...maybe zubbly can give us that info if he has torn any apart after some time to see what the wear is(if any), on the bearings walls, or the bearings themselves....nice hearing from you....pickster

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[coldspot]

I flew one all winter long,

Ametek 30 VDC

I read a post about using an easter egg half

and a soldering iron to make a seal for the shaft

THEY NEED A SEAL !

I found a rubber boot type that adds a tiny

bit of drag to shaft.

I might have to try a egg half,

might be easy enough to find one or two today.

I think mostly about hold up

Seal it for weatherfastness

front bearings should hold up for a while

I had all the ceiling fan blade mounts, (three)

blown off my Ametek a couple weeks ago, (50 Mph steady, gusts 70+)

And had little luck with the PVC set I tried.

So a induction conv is up on that test tower at this testing point

PVC blades that I made for this one are working better

than simular ceiling fan blades are for some reason,

(Furl tail way to light)

Can shaped Cen's can be easly covered with a large half pipe of

PVC for a topside sheild.

But front shaft needs sealed better,

Egg half melted to slide over shaft, then glued to

seal around the bearing letting shaft just touch

were it pass's thru would help keep water OUT.

[zubbly]

hi iFred!

i have an industrial duty Leeson 1.5 hp (1725 rpm full load) 180 volt pm dc motor. it has a 6205 bearing in the drive end and a 6203 bearing in the non drive end. the output shaft is 7/8 inch diam.  i often got 30-35 amp output into a 12 volt batt bank.

i flew it for a while with a 2 blade 9 foot prop. the shutter from the 2 blade eventually tore the motor's base to pieces. i welded a new base to the frame.

when the base broke, it allowed the motor to tilt down and caused a blade strike on the tower shattering the prop to pieces. (no more 2 bladers for me)

the bearings were however still in perfect shape and thrust seems to have no problems to date on any of the gennys i have made. those ball bearings will take more thrust than many people beleive they can. you can get the specs on any size ball bearing from a bearing supply house.

my current genny that i experiment with the most is a 1.5 hp induction conversion and now running an 8 foot prop on it. i did for quite some time have an 11 foot diam prop on it. actual running time on this unit is more than 2 years. bearings are still in perfect shape. i think the greatest factor in bearing longevity is good balance of the prop. i generally balance the prop on another motor shaft that has not been converted.

your shafts are probably 5/8 inch diam. i drill and tap a 5/16 inch hole about 1.25 inches deep into the end of the shaft. my blades are sandwiched between 2 steel plates and then i put a bolt directly through the 2 blade hubs and directly into the shaft. it makes a very secure mounting.

6 foot diam 3 blade for the 1/2 hp and 8 foot 3 blade for the 1 hp should work out well.

here on pages 21-23 of my album, you can see how i assemble a 2 meter prop with 2 steel plates and a hub for a 5/8 shaft.  you can also see that i use a pendulum weight for balancing.   http://www.anotherpower.com/gallery/zubbly?page=21

i think pm dc motors make great little gennys and actually get overlooked a bit too much in my opinion. if the commutator and brushes are in good shape, they should give a very long service before any attention is needed.

also, i did fly an ametek 30 volt model for a while.  the prop was a 54 inch 3 blade unit. i had it on a 50 foot tower and that unit totally screamed until the brushes wore out and messed up the commutator. ball bearings in it were actually very small, but they were still in perfect shape when the unit came out of service.

by the way, the weld on hubs i use come from "Princess Auto Supply", available in most bore sizes and are also keyed. cheap as hell and work well. there should be one of those stores in your area.

hope this info helps you iFred.

have fun!  

zubbly

[zubbly]

i should also have mentioned that i generally use a sealed (2rs) bearing in the drive end, or order a "ZZ" bearing from FAG bearing.  the ZZ is a light contact seal and really does not hinder rotation at all.

also, you can also order at your bearing supplier what is called "V-rings" which are designed to keep dirt and water from entering the labrinth seal where the shaft passes through the end housing of the motor. they are basically a friction fit type of "o" ring which you slide up the shaft and tight against the bearing housing of the motor.  just specify the shaft size you have. the part that goes against the housing is a very thin flexible rubber that seals out the elements pretty good.

zubbly

[iFred]

Hey Picster!! Long time no hear.. Yes, please drop in some time! Thanks for the comments!

[iFred]

Excelent! Thanks Zubbly for the info. I was'nt so sure but needed to know that. I'll look into the mount flanges and bearings as well, looks really solid. Yes these motors are rated exactly like what you stated, about 130 vdc - 1780 rpm -one horse power, and the other is a half a horse power. should produce good results. i figured I would play in and about 8 ft range blade or maybe less. any  figures on the rpms I should hunt for?

Thanks again for your comments!

[tecker]

A separate bearing harmonic balance sort of thing sounds good but I think the centrifugal force dominates if the blades are balanced. The condition of the bearings in the first place is always a concern . I saw a cool design with pillow blocks and a platform  the could use several diferent motors or blade combinations (good test rig)

[zubbly]

i have found that on all the conversions including the dc and ametek that tsr of 7 seems to work out good. most of my blade specs have come from alton moore's site.

zubbly

[Jon Miller]

Hi stevesteve I think i have three of the same motors as you.  I too got them of eBay and will hopefully be using them soon, if im correct i think they have a thread internal shaft, im think to make some zubwoffs and bolt them on.  Could you let me know about your ideas for making as i am in the same boat, thanks