UFO politics Keeps his word 12-12 12 Let the games begin.......

[MileHigh]

Chet:

His modified motor consumes almost a kilowatt of power with no load attached to it.  My instincts are telling me that that doesn't sound very good at all.  I am going to guess a standard motor running the same unloaded test would dissipate less than 150 watts.

For now, I am assuming that his DC clamp-on meter is doing a proper job of averaging the current consumption.  I have no experience with DC clamp-on meters so I am not really sure and I am not going to look it up.

The legitimate test that he did not do would have been to compare his test run data of the modified motor with a standard motor also running without a load.  In addition, both motors would have to be turning at the same RPM so you would need a beefy variable power supply also.

For some strange reason he compares his modified motor running without a load to the standard motor running and driving a 4-horseposer load.  There is simply no point in comparing an unloaded motor with a loaded motor.

MileHigh

[tinman]

So am i seeing right?-32 amps at 37 volt's just to have it free running with no load?
1180+ watts just to run the motor-man that is one hungry motor.
Wonder what will happen when a load is applied,like a 6kva gen head?

Now correct me if im wrong,but isnt one leg of the motor suppose to be an output(ie generator)?.If so,why dose he have power going into both legs of the motor?

So now,just out of curiousity-im going to hook my 1hp 24 volt motor up to 36 volt's and look at the current draw.
This is just to see how much current a motor should draw in standard trim.

It would seem to me that UFO's two input legs are having argument's with each other,and causing a massive current draw?.

[ramset]

Inviting Comparison........?

@TM
It would seem that a comparison is being offered,I do not see a "no load" or "Idling load" spec in the data sheet.

I have no doubt this Value is readily available![from what I can see "Googling" DC motors use 5-10 times [dif / design types] less under No load / idling ]

However,UFO Must be aware of this ,he seems to be going for RPM
which at 7500 is 3 times published design speed of 2500.

He's happy ,and the replicators are happy,I suspect this High RPM
is the comparison at this point!

I wouldn't mind seeing what that little beast would do at the golf course
[I see its a golf cart motor].

I am sure a load test is soon to follow once his high RPM Coupling issue is resolved.
He just needs a good R+D guy to help him out over there.
Thx
Chet

[picowatt]

What is amazing is that after 110 pages and mods of both the RS motor and the Imperial, not one efficiency test has been performed.

UFO does however appear to be preparing a Prony Dyno using a steel cable, drum, and dual scales.  Depending on the size of those components and the surface area of the contact area, there is going to be rapid temp rise on the brake.  Localized heating/galling will likely cause the scales to hop all over the place. 

A mini-bike/go-cart disc brake or similar would likely be a better brake option for the expected kw.

Another alternative is to drive a single or three phase induction motor and apply a bit of DC to a winding.  The frame of the AC motor is mounted so that there is a degree of freedom about its drive axis and a bar of known length is attached to the AC motor frame with its free end resting on a scale.  Many AC motors have mouting brackets that use rubber bushings coaxial to the end bearings and these are easily used with plastic or metal bushings to allow the frame some rotational freedom.

DC can come from a supply or battery charger with a Variac on the AC input.

Heat is still a concern, as the rotor of the induction motor will get quite warm as it dissipates the brake energy, so it is common to use a small blower ducted to feed air into one end of the AC motor to assist in cooling.  The set up allows for  pretty smooth braking (depending on the test RPM).  The required AC induction motor HP rating is more dependent on temp rise and test run time, so the larger the motor used, or the better the air flow used for cooling, the easier it will be to deal with heat.  3/4HP or larger would be a good starting point.  Three phase motors can usually be found pretty cheap and can also be used.

A bit of research on the web in various forums for small engine modders (competition chain saws, lawn tractor pullers, steam guys, one lungers, etc) will yield a wealth of info regarding Dynos made in all manners from simple to water cooled.

The biggest problem is always regarding heat, and having smooth braking so the scales aren't jumping all over the place.  For mechanical brakes, large surface areas and hi-temp materials prevent localized hot spots and galling which tends to "catch" and bounce the scales.  Brake rotors, calipers, and brake pads are designed to deal with these issues, but even long duration test runs can over heat a brake. 

PW

ADDED:

Replacing the flexible shaft coupler with a rigid coupler is likely not a very good idea.  Any misalignment between shafts will produce a lot of vibration, increased bearing loading, and shaft/coupler wear.  The use of a solid coupler requires precision alignment.  If the flex coupler is getting warm, it probably indicates that the shafts are out of alignment and the coupler is having to flex excessively.  Better alignment and proper selection of the elastic material for the spider (or a different type of flex coupler) would be more advisable.     

[mikestocks2006]

Another very simple test would be to run the standard motor without load on the same 3 battery source. He has one such motor available. Record the rpm, volts and amps, see the difference if any.

Thanks
Mike