Electric motors - any ideas?

Sune Posselt · Post by **Sune Posselt** » Tue May 04, 2004 10:54 pm

Hi all

I just found two fairly big electric motors in a dumpster, now I only need to figure out what to do with them, and where would be a better place to ask than here?

One is rated 3 kW, the other 2 kW. I have no idea what kind of power they'll give, but considering they weigh in at about 100 and 60 pounds respectively (not to mention the trouble I had getting them home on the back of my bike :) ), I'm hoping they're at least moderately powerful. They are rated at 1400 rpm, but I also found a few belts and pulleys of various sizes, so I should be able to vary this a bit

So, what does one use such nice toys for, if one doesn't need a 100-pound paperweight? Bonus points will be given for creativity :)

/Sune

Stephen H · Post by **Stephen H** » Wed May 05, 2004 4:41 am

ahh.. interested in ramjets? make a big spinny thingy with to arms shaped like a "T".. motor drives it round and a weight on one side equal to the ramjet on the otherside. should be able to get it fast enough.. mabey.. if the arms were big enough!!

Al Belli · Post by **Al Belli** » Wed May 05, 2004 12:06 pm

Hi ,

1 Hp. = 746 Watts
3Kw. = 4 Hp.
2 Kw. =2.7 Hp.

Al Belli

Sune Posselt · Post by **Sune Posselt** » Wed May 05, 2004 3:32 pm

True, except the motors aren't 100% efficient - some energy will be lost as heat etc.

And neat idea about the ramjet thing, might be a bit ambitious though -- considering I know nothing about those engines.

Post by **Mike Everman** » Wed May 05, 2004 3:53 pm

The wattage is usually the peak value, deliverable for a few seconds. The continuous capability is probably 1/3 of that.
There's a good NASA ramjet page, I think Glenn Research Center; I don't have time to get the link at the moment. I'd love to do a whirly ram myself. You'd have to gear these motor up if you want to get near sonic with any reasonably small radius. :-)

Mike Kirney · Post by **Mike Kirney** » Wed May 05, 2004 4:37 pm

Those are still pretty strong motors. Most stuff I find in the garbage is 1/4 hp or 1/3 hp. I have some three-phase whoppers (25 hp, 35 hp) I found in my yard but I am having a hell of a time taking them apart because they are all rusty. Concerning the ramjet spinner, a circle 1 metre in diameter has a circumference of 3.14159 metres so spinning at 1400 rpm, the ends of the arms (0.5 long each) would be travelling at roughly 264 km/h. If you put a 4:1 pulley/belt system on the motor shaft, you could get some sonic speeds from a reasonably short arm, although I wonder how much torque you would need to accomplish that. You could use the motor to start the jet a-whirling and once the ramjet was running reliably you could switch the current from the armature to the field and have a ramjet-powered generator. By the way, Sune, what are the volt and amp ratings on these motors? I am guessing they are AC and single phase. What diameter is the shaft? If you had some old bicycles, an inverter or two and a couple of car batteries, perhaps you could use the 3 kW motor to make an electric go-cart.

Sune Posselt · Post by **Sune Posselt** » Wed May 05, 2004 6:50 pm

Hi Mike (and all)

I just checked the motors again, and it turns out I was wrong about the small one, it is only a 1,5 kW unit, not 2 kW.
They are rated at 380 volts, 6,8 and 3,7 amps respectively.
The diameter of the shafts is about 3 centimeters, but unfortunately the inside diameter of the larger pulleys is a bit bigger, so I won't be able to create a higher gearing :(
They are AC units, but I don't know about the phasing. The power cord has four legs -- would this mean that it's a three phase unit, with only leg for each phase and one for neutral, or am I way off? As you might have guessed, my knowledge on these issues is very limited :(

/Sune

larry cottrill · Post by **larry cottrill** » Wed May 05, 2004 7:15 pm

Sune Posselt wrote:Hi Mike (and all)

I just checked the motors again, and it turns out I was wrong about the small one, it is only a 1,5 kW unit, not 2 kW.
They are rated at 380 volts, 6,8 and 3,7 amps respectively.
The diameter of the shafts is about 3 centimeters, but unfortunately the inside diameter of the larger pulleys is a bit bigger, so I won't be able to create a higher gearing :(
They are AC units, but I don't know about the phasing. The power cord has four legs -- would this mean that it's a three phase unit, with only leg for each phase and one for neutral, or am I way off? As you might have guessed, my knowledge on these issues is very limited :(

/Sune

Sune -

They are probably not three phase, but rather split single phase, like 240V equipment in the US. The extra lug is probably so the neutral can be separate from the frame ground [safety ground], as required for some types of service.

Go to a place that sells electrical [NOT electronic!] supplies. They can identify the type of service from the exact plug type, and might even take time to explain to you the function of the different blades in the plug.

L Cottrill

Sune Posselt · Post by **Sune Posselt** » Wed May 05, 2004 7:56 pm

Hi Larry

Unfortunately the power cord has been cut, so I guess that isn't really an option. Besides, the prospect of hauling the motor halfway across town on the back of my bike makes this solution a bit less attractive :)

www.pulse-jets.com

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