a small puzzle

Of course. Did you ever notice that the most current you can push into a dc motor is at stall? Current has to go down, when the thing starts turning enough to generate back emf. I'm just claiming that you can't get more mechanical output than the electrical power you put in, and for a constant voltage supply, that occurs at zero rpm for a pm dc motor. Look at the torque/speed curve if you don't care to believe me...it's pretty linear.

Presuming brush drop isn't a function of speed... and it can be a significant effect.

I'm old-guard MIT grad... I had TWO years of machine labs... pretty useless stuff in this day of electronically-commutated motors, but actually was fun 56-58 years ago.

Mercedes AC blower...

which will only draw small pulses of current at stall.

Now! If this is a motor out of your vacuum cleaner, it's _all_ a lie ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website.

You get no power out (other than heat) at zero RPM. Maximum torque, zero power.

Where you getting tht from?

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This email has not been checked by half-arsed antivirus software

Uh-huh, it's from a small Harbor Freight branded ATV winch...it is all a lie! Cheaply made, brushes are not replaceable, only one shaft bearing in the motor, they use the input bearing in the planetary gear on the output to support the pto end of the armature. Fortunately, I don't have to care too much, it still has enough grunt (sci term!) to move my 14' trailer both forward and backward. I'm using it in a DIY trailer tug, kind of like a 14' long RC car. Only reason I posed the question is curiosity, as in "how de do dat?". It sure is not obvious...but I suspect it is clever.

-bill

yep, plenty of power, just zero "work".

-bill

Fo a slow winch HP has no meaning, it's all about torque. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website.

The planetary gear provides a clue, motor runs very fast, so HP rating would be based on motor speed, not load shaft speed... so maybe it is officially 1.5HP. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website.

Den tirsdag den 13. september 2016 kl. 19.02.23 UTC+2 skrev Jim Thompson:

for a

a

e

if if doesn't use >1100W is doesn't produce 1.5HP

no amount of gearing is going to change that

-Lasse

It's Harbor Freight, what do you want already... their claims are nothing compared to the typical vacuum cleaner claims of outrageous "peak" HP. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website.

If the drum turns at relativistic speeds time will slow down making the same battery energy dissipate over a shorter time period increasing the power level.

--

Rick C

That's not power, that's torque.

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Rick C

Noooo.... No work out, no power out. However this is the maximum power

*in*. The power out can never exceed the power in so motor stall input power sets a ceiling for the possible power out at any speed.

--

Rick C

Jim is a bit up there and doesn't always comprehend what he reads... as is true for any of us at sometime.

--

Rick C

Some people just don't know that stuff. Horsepower takes into factor speed whereas torque does not. Gear it up or down and the torque changes but the horsepower does not.

Car engines. I do not have the exact numbers right now but one year the Cor vettes had two 350 HP 350 engines, one Chevy and one Mercury Marine.

The difference ?

350 ft lbs peak torque at 2,800 RPM, 350 HP at 4,000 RPM 350 ft lbs peak torque at 1,800 RPM, 350 HP at 6,000 RPM

Which is faster ? Gearheads know.

And you can just about mathematically derive the torque curve from those nu mbers, or come close. There are anomalies due to airplay in the manifolds a nd a few other things but you can get pretty close.

One strangety I heard of recently is a Harley Davidson golf cart a buddy of mine it restoring. This thing,, instead of having a gear box uses a two st roke diesel and to go into reverse it starts the engine backwards. They pro bably chose that design because it was cheaper, but personally I think that reverse should be geared down, like in cars and trucks.

Their engineers did not see it that way. Saving a few bucks was more import ant. I can imagine the meeting with the bean counters and lawyers - "So how much you figure this is going to cost us when some old geezer runs off a c liff backwards at 40 MPH ?".

LOL

Also, if you want accuracy you should use a Kelvin connection.

THAT is the crux of the matter and the answer to your question.

Den tirsdag den 13. september 2016 kl. 20.55.08 UTC+2 skrev snipped-for-privacy@gmail.com:

should be obvious to people around here that

torque*speed = power just like current*voltage = power

and that a gearbox is the mechanical equivalent of a transformer

-Lasse

yeah, what I said.