a small puzzle

A little OT, but what the heck, there are electrons involved. Noticed some oddness re. a small ATV winch, 12VDC powered, with a PM brushed motor and an up/down reversing switch: It runs slower in the down direction than in the up direction...checked the resistance of the armature/brush dc path, same in either polarity. Checked the switch box, again, the same in both directions. What the heck! It does seem reasonable to run slower in the "unload" direction, but how is being done? Not really interested in tearing everything down to the bare bones to figure it out! One other interesting anomaly: The motor is tagged as 2.5hp, but given the approximately .5ohm armature resistance that I measure, that's about

24amps stalled rotor... 12V * 24A is 288 Watts, how in heck is that 2.5Hp? :-) Maybe those Chinese horses are really tiny?

Bill

Reply to
Bill Martin
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brush position

I suspect so.

NT

Reply to
tabbypurr

Ahh, that I could check without major destruction, thanks for the idea.

Reply to
Bill Martin

Bill Martin prodded the keyboard with:

I would suspect that the HP rating is that at the winch drum.

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Best Regards: 
                      Baron.
Reply to
Baron

How would you get more power out than the battery is putting in? Maybe a few milliseconds surge from stored inertia, it really does not have a flywheel to store energy though.

Reply to
Bill Martin

Bill Martin prodded the keyboard with:

Simple gearing. Though calling it HP is misleading and labelling the motor as such. Might be more accurate to say effective HP. I've seen similar motors break teeth off their gears.

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Best Regards: 
                      Baron.
Reply to
Baron

effective HP? That must be a marketing term for made up nonsense

gearing does not increase power, it can increase torque, torque is not measured in HP

-Lasse

Reply to
Lasse Langwadt Christensen

perhaps they measured maximum pull force and maximum pull speed and multiplied them, getting a different sort of immaginary power rating.

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Reply to
Jasen Betts

Or took advantage of inertia to get a momentary peak output figure. Or just made it up.

NT

Reply to
tabbypurr

This Jason person is too ignorant of engineering fundamentals to know the difference between STALL torque and HP. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

A Small Puzzle Q C W P A D Y P P A N M F V G M E R H A M P E R E S R G F U R X S R P E Z E T Y E R C R O H T R E Z A O S K I D A T M W N L P R A T Q Y R T A A R L T T M U A X A I N C U Q E A M E K A S E H T T N G G N E E N T R P P B R T T I K S C A F E P N O T E L S E E E G E C I Q T Z T S C I I N I U R L I N E L S T I L N Q Y T M E F V M D E I O Q E E O B A H J A S G I E W I V C V H R P N C P W R L N S E P V E C M T M P C H A T E B U A I R Y R O F R L R U O R O C B Z D R D R T T A L I O R O G R E N Q G O T E E E U Y H T R W E N I C Z Y C M V B W L N C O E A L A V I K I H Q J P A O E E T N C E G E V T C K M V H J N P T R T H T E R E A E F S N V H Q D V M Find these hidden words in the above puzzle: AMPERES AMPLIFIER ANTENNA BATTERY CURRENT DIGITAL ELECTRONICS FREQUENCY GENERATOR HEATHKIT METER MICROPHONE MICROWAVE MODULATION POWER PROPAGATION RECEIVER RESISTANCE SIDEBAND SPEAKER SPECTRUM TELEGRAPH TELEPHONY TELETYPE TRANSCEIVER TRANSMITTER TUNER VOLTAGE

(If this does not look right, you may need to use a mono-spaced font like Courier or Monaco)

Reply to
Fred McKenzie

Another small puzzle:

Y=X^X

Solve the relation for X.

Reply to
John S

That's one small puzzle. ;)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
Principal Consultant 
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Reply to
Phil Hobbs

Neeerp! Most quadratic solutions of physical problems have boundary conditions which limit the choice to only one root. If two roots _are_ allowed you have a potentially unstable system.

...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Of course it's not a physical system, and it's not a quadratic. ;)

Cheers

Phil Hobbs

Reply to
Phil Hobbs

Sure it is... just b=c=0, so ooopsy on my part.... many solutions. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

You cannot get a reliable reading of armature resistance through the brushes. The large current when the motor is actually running and the action of the brushes wipes oxides off the commutator, making a much lower resistance connection. If you REALLY want to measure it, remove the brushes and use sewing needle-sharp probes to poke into the commutator. Also, you need to use a milli-ohmmeter, the typical DVM can't tell the difference between 0.001 Ohm and 0.5 Ohm or more.

Jon

Reply to
Jon Elson

Well, curiosity got the better of me, I opened it up. There are four brushes, at 90 degrees, so no asymmetry there. The only clue to be found is that two of the four magnets, also at 90 degrees, have a little ink stripe on one end...and offset from the centerline of the magnet poles, in opposite rotational direction. Not sure that means anything, but it is all that is visible. BTW, I misread the HP rating, it says 1.5, not 2.5, not that it matters, it ain't possible!

-bill

Reply to
Bill Martin

True enough, I was mostly interested in seeing if there was a difference with polarity, which there was not.

-bill

Reply to
Bill Martin

You persist in being wrong. Define HP for me in terms of torque and speed. Ever hear of a torque speed curve? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

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