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Old 04-13-2017, 09:53 AM
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Default Found a used DC motor, good for Go Kart?

New to the forum

Any ideas on this DC motor I found?
See attachment for motor tag, hope i attached it right.
Pesco Products Co 26vdc 6000 rpm

Very early stages but I plan on using 3x12v batteries. I found this motor at a salvage yard and couldnt help myself. Im having a very hard time finding any info online about this company, looks like they did a lot of work for the government in the 60s but nothing I can see for this motor specifically.

Im concerned about the low 3.91 horsepower and high 157 amperage, though im not sure if amps on a DC motor are rated like 3 phase AC motors.

I read a normal go kart motor rating is about 1000 watts or less so at 26 volts its about 38.5 amps (though I plan on 36v/1000w=28a). So backwards math says 26v and 157a is 4082 watts? I think missing something or this is some special motor that wont work for this project.

Also not sure what INT means on duty, maybe the 900 seconds on and 3600 secs off is INTermediat duty? I got it cheap so if its not good for a go kart ill find something else.
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Old 04-13-2017, 10:13 AM
bigrigbri bigrigbri is offline
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Try the motor on 24v that should help the motor in running cooler ie more continously.
There should be plenty of power and will take less current.
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Old 04-13-2017, 10:54 AM
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Uhm nope.. less voltage does not equal less current!
(less power: yes.. less heat: maybe (but unlikely), less current: NOPE!)

Anyways, the duty cycle of this motor is kinda bad for a kart..
I mean 15 mins on then wait an hour for it to cool down enough to run for another 15mins is kindof annoying (especially if more than one kid is involved[you included LOL])

The efficiency of that motor is really bad too I'm afraid, I mean it draws 4000+ Watts electrical and only spits out ~3000 Watts of mechanical power that's sooo 1960s
70% is really really really bad in motor efficiency;
especially since you need to be sure that all loss is generated HEAT
(a 2kW heating element basically)
which explains the lousy duty cycle.

But not all is lost, you can improve that (hopeffully)

FIRST: let us see the whole unit!
and inspect it..
if it's shaft runs in bushings, upgrade these at least (if possible replace with bearings)
that'd reduce at least some friction.
then upgrade the brushes (assuming it's brushed)
it sounds like it's a permanent magnet motor (which in your case is unfortunate)
Otherwise you could just upgrade the brushes to more recent ones and increase the efficiency by a noteworthy amount.
But in this case.. (that bad efficiency) it's likely ferrous magnets..
You could swap them with high power neodymiums of course, but that'll be extremely expensive (more expensive than buying a new 5kW 80%+ efficient motor off any shelf really)
So yeah,
the last thing possible to improve that duty cycle left is cooling..
closed caps? disassemble and find a good spot to add some holes ..
enough room inside (Brush-side) to add a small plastic fan to make it actively cool it's coils by itself?

could you add cooling fins to the case? (keep in mind: welding is a no go because of the magnets)

And then finally if none of that is within range...

Get a programmable controller for the motor (Kelly makes nice ones)
and if possible get one of there thermistors as well.

Attach the thermistor to a good spot on the motor to let the controller know when it's overheating. (to shut it down before it's toast)

And: maybe reduce output to a maximum of 80%!
(it still peaks at the same 160 Amps mind you, thus the controller must be able to deliver that)
BUT it only does so for 800 out of 1000 milliseconds

Thus reducing the drawn power to 80% (and hopefully the generated heat)

Start at the lowest powersetting you can live with and run it as hard as you can at that setting until the thermistor calls to shut the motor down.

then work your way up until the duty cycle dictated by the thermistor is no longer acceptable.
and back down for the sweet spot

internal temp must NOT exceeed ~100C for ferric magnets in order for them to not lose their magnetic strength (neodymiums must be kept even cooler )
so try to stay below 80C if you cannot put the thermistor inside the motor case!

Once is enough to render magnets useless btw, so be gentle with it.

'sid

[EDIT]
Oh see.. all that babble not answering the initial question
Yes, when taken care of the downsides of that motor, it'd be a nice one to power a kart,
it has more than enough power (even at 80%.. dang even at 30% !!)
to move a gokart around.. kellycontroller can provide a matching controller and all you need to fire it up properly really..
so yeah.. I'd at least give it a chance.
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Old 04-13-2017, 11:29 AM
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Thanks a ton, thats great info. I thought this motor was either really old or specialized in some way. Ill take some more and better pictures when I get off of work today.

First off, its for me and my 34 yr old butt to ride in, I weight about 190lbs (86kg). I want power and acceleration but I do plan on constant upgrades so starting small and simple is fine for now. At the moment all I have is this motor so any parts I get Id like them to be able to work with each revision. And of coarse I dont have a ton of money to put into this.

So if I planned on getting this motor at some point unless you recommend something else,
http://kellycontroller.com/24v-1000w...tor-p-511.html
would a programmable controller for my odd ball motor transfer over?

Also Im new to the programmable controller parts so the terminology and wording on the Kelly website is a little above my skill level. Can you recommend a controller that would work fine for a few upgrade paths.

Thank You

---------- Post added at 10:29 AM ---------- Previous post was at 10:25 AM ----------

Are these what you were thinking

http://kellycontroller.com/kds36200e...ler-p-276.html

OR

http://kellycontroller.com/kds48200e...ler-p-286.html
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Old 04-13-2017, 12:06 PM
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exactly.. both of these are what I had in mind..
if you do not need 48Volts take the cheaper 24-36V (kds36200) version.

add the usb cable to actually program it and the thermistor they have in their shop (one is in accessories the other in sensors IIRC)

for convenience cables and /or connectors might come in handy, so check twice before ordering to spare you the hassle of paying shipping twice

That 1kW is nice, but not exactly cheap either.. roughly the same specs can be had for half the price from UNITE Motors (MY1020 1000W) which is basically the cheapest reliable 1kW you can find atm.
(btw that one also peaks at ~2kW++ mechanical power under full load for a few seconds which is also almost 3hp )

'sid
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Old 04-13-2017, 12:50 PM
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Thank you again. So this Pesco Ive got, is also very heavy and probably 12in front to back. The MY1020 1000W is comparable or more powerful and so small? Shouldn't surprise me i guess.

I really like the usb hook up part, I have a usb to RS232 cable. Does it just plug into the controller somewhere? Is there some kind of software to make the changes.

Is this the thermistor?
http://kellycontroller.com/kty84-130...tor-p-314.html

I have on of those in an arduino kit i think, didnt know what it was. : )

What about throttles or pedals? What are the differences in the 0-5v pedals, if I built a pedal mechanism is it basically just a potentiometer.

Do you do anything or over-current or motor protection? Is my adult weight a problem for the quality of parts were talking about?

Big fan of planning ahead.
Thanks
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Old 04-13-2017, 03:33 PM
bigrigbri bigrigbri is offline
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Tell me how less voltage on a constant resistance/inductance equals the same current draw.
Being a low cycle motor they are constructed using far thicker wire than the operating voltage suggests hence offering the OP to lowering the voltage to lower the rpm and excess heat.
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Old 04-13-2017, 05:50 PM
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first inductance and resistance are two different things living in the same triangle (like cats are not dogs just because they share the same owner)
second resistance on that coils is all but consistant, mainly because each winding effects the adjacent ones when there's a current flow or better magnetic field because of such.
it also changes with temperature
Third and most importantly:
copper wire is indeed a resistor, at a fixed length and width (which we can safely assume)
the resistance should be fairly constant indeed
but just because we induce a lower voltage potential at both ends does by no means limit the currrent it's technically able to pass through.

Just as your USB cable on your phone is happy with a 5V 0.5Amp std computer USB socket,
it can still be attached to a 5V 1.5Amp quick charger

and if you short it out it will try to pull even more from the computer port (likely shredding the motherboard or PSU [or both])
At no point it sees neither 15V on the 1.5Amp port nor 1.7 on the 0.5Amp port...
it not even changes it's internal resistance really either.

it's just dumb copper able to pass up to 1.5 Amp at 5V (ideally that is.. cheap stuff craps out at 1200mA... nevermind)
that doesn't mean it cannot pass 1Amp at 4V or 1.4Amp at 3.3V or IDK make up your own combinations.
it indeed has limits just as the windings in the motor will have;
but the nominal ratings are far from those limits and it'll draw 157Amps if it can
and it gives a flying shirt about the voltage it does that at.

'sid
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