electric motor stuttering

redflash

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Bldc 48 volt motor and matching controler ...6-1 sprockets...everything has worked well for 10-12 rides.....when rear wheels are off the ground everything spins nicely.
when a rider sits on it and attempts to drive.... you hear a sound which sound like the chain skipping over the sprocket....when you look back at it, its not skipping, the motor appears to be chattering, and it will make forward motion at about 1/2 mph. One shop suggested that the "Hall" wires from the motor are not solidly connected to the controller fitting. I bought a "motenergy" tester, and it tells me the motor is fine ( all hall effect sensors are firing correctly ). I've replugged the connecters back together....and again if the wheels are off the ground I get full RPM spinning....but with a load the motor just chatters......Help me brothers

Da Flash
 

JTSpeedDemon

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What is the sprocket count on the motor and axle? Also we need the tire diameter. Sounds like a classic case of too-high gearing.
 

redflash

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appreciate the response, but no.... as I said the ratio is 6 to 1...and it has run with absolutely no problems for 10-12 rides. I'm sure it's not mechanical...it seems to be electrical....... as was suggested it might be connections of the hall wires......anybody seen something like that ??

also tire diameter has not been the slightest issue ...as it accelerates quite well when its not stuttering.

this might be a question for the infamous Sid.....he appears to be the electrical guru of the century !!!!!!
 

Functional Artist

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Ah, missed those parts....
Um...he gave all of that info in the first post. :unsure:

I've experienced this phenomenon a few times too, seems/sounds just like the chain is "skipping" on the drive sprocket
...but, it has only happened intermittently, usually on hard acceleration.

I also, have visually verified that this was not the case. :cool:

I was almost thinkin' that the shaft may be spinning inside of the sprocket
...but, I haven't looked into it further.

Yup, maybe Sid has some insight :sneaky:
 

itsid

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Hi ..
that unfortunately sounds like you cooked the magnetic field off the motors magnets.
(happens quickly and at rather scary 'low' temperatures of just over 80°C [176 Frankfurters])
maybe someone pushed the throttle too eagerly with the kart not wanting to move..
and didn't even cared for ~10 seconds that it's stationary still...

and if that chain stuttering sound is for the same reason,
you either have one faulty set of magnets or at least one good set still.

Easy test :
disconnect the motor from the controller entirely (not one wire must be connected)
take steel bolt and connect all three phase wires together to short them.
now lift up the back end and try to rotate the wheel veeery slowly.
you should feel "notches" 18 in the motor usually and therefore (with a 6:1 reduction) 108 per wheel revolution.
if you cannot tell if all are equally strong locking, remove the chain and rotate the motor shaft directly instead.

My assumption: every third feels different (either weaker or much stronger than the other two);
if that's the case.. the cheapest fix is -I'm afraid- a new motor.
having custom made magnets fabricated is terribly expensive, finding the correct strength magnets
almost impossible without proper Lab-equipment and worst: epoxying them in is a real pain in the beehive.

In case that assumption is incorrect and the motor latches into each magnetic notch perfectly identical,
the motor is fine and instead one of the phases of the controller burned out.
(might be as easy a fix as replacing a single or pair of MosFets..)
that would be the lucky case I guess.
But maybe you could more easily get a new controller instead.
IDK how good your soldering skills are ;)

'sid
 

redflash

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sad,,,,sad the Chinese BLDC $100.00 motor is dead.... no resurection here. Tell me guys...what 48 volt motors are available between the chinese $100 motor and the $500.00 americans ? There must be something in-between,,, that is cheaper than $500. I've got a brand new stage 2 predator 212, but

I'll need to spend $200.00 on centrifical clutch, driven sprocket, and motor mount to move to right side. And for the neighbors sake ( and creative eco ) I'd like to keep the electrical system since I already have batteries, and controller et.
Thanks again Sid, you saved me some search time.

Da Flash
 

redflash

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since I fried my 48 volt 1800 watt motor by apparently overheating it......the question arises...Is there a "overheat" fuse, or something I can put in-line with the motor that will protect from inadvertent overheating the motor ???....I am an electrical idiot...please help....SID ??
 

Functional Artist

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Have you thought about why it overheated so badly?

You mentioned a 6:1 gear ratio
...but, what size tires?
...how heavy is the kart (including driver)?
...& what kind of terrain was it driven in/on?

Maybe some pics
...we like pics :sneaky:
 

redflash

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F/A....18" tires old rebuilt dart kart....80 pound kid. all level ground. Had a situation where the key fell out of axle sprocket slot, and kid probably fried the motor spinning the dead sprocket around the axle trying to make forward motion. we've had some 110 degree days here in northern Califonia.....if he was doing too much stop and race.....motor could have well got to over 160 degrees with the ambient at 110 degrees. It is what it am !

ive ordered one of those heatsink cylinder that goes on auto oil filters...3 inch I plan to heat it a little and solidly fix it on the new 4 1/4 inch motor to reduce some of the heat

Da Flash
 
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itsid

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could you specify the motor in question a tad better?
(maybe post a pic of it even)

BTW: there is no american made motor for 500 bucks ... sold by american companies yes..
american made nope.. not one for all I know;
ALL are chinese made. So as chinese as your predator ;)
very few exceptions (Taiwan, Indonesia and really expensive ones from japan...)
custom hand wound motors are made all over the world but stuff you buy off the shelves is from Asia.

Anyhow, unfortunately you gave no information about the motor (size, power etc..)
so we cannot suggest anything but to keep your eyes peeled.

Now.. usually the cheap chinese motors (BOMA etc)
are of reasonable quality, as long as you do not mistreat them badly, they'll work well
(albeit most are slightly overrated in terms of continuous power)

if you want to prevent such happening again (say with your next cheap $100 identical replacement)
you can add a few pennies worth of electronics and add a thermal protection.
self resetting thermal fuses (actually a thermal switch ;)) in the 70-75°C range will be all you need
best a resistor programmable one IMHO to set the temperature to manufacturers recommendations.

an opening switch can be wired in series with the 5V line of the throttle to cut the throttle out
a closing switch can be wired in parallel with the brake pedal switch to shut the motor down directly.
both will essentially shut down power from the field coils preventing the motor from overheating.

If that however is a "common" issue with your setup, it's time to shed some weight and/or improve the gear ratio significantly I'm afraid.

In edge cases it might be suitable to add active cooling to the motor
(a heat sink and a nice fan wedged onto the shaft behind the sprocket to blow air through)
but that only works if overheating is the occasional exception to your usually "cool driving"
(say climbing the incline of your drive way or such)

'sid

[EDIT]
since I merged the threads.. it's a bit awkward to read,
but I think you'll find the answer to your sub-request as well ;)
 

redflash

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in regard to gear ratio...are you suggesting rather than the 9 tooth drive....54 tooth axle...That I go to 60-72 tooth axle sprocket ?
.
The motor label only states....BLDC MY1020.....48 volt...1800 Watt...4500 rpm
again I appreciate the assistance
 
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itsid

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that's the info we were asking for;
my1020 is the can size and with 1800 Watts
we now know the power and size we would need to find a replacement for ;)

in order to know if that 6:1 ratio should work or not
we need to know for what vehicle (wheelsize, total weight inkl all passengers).

'sid
 

redflash

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18 inch tires...cart must weigh about 150 lbs,,,usual rider is approx 110 lbs........occasionally a 200 pounder rides around the block. always level ground.
just ordered a 72 tooth sprocket which would give me an 8 to 1 ratio......whut yu tink ????
 

Justin67

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Hi, I have brake caliper that is on my go kart. It squeezes together but it doesn't retract. I thought to "rebuild it" or change the seals.(I think this is what I should do) The problem is that I can't find the kit anywhere or even what kind of caliper this is. Can anybody help me out?
Thanks, Justin
 

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Justin67

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Hi, I have this brake caliper that is on my go kart. It squeezes together but it doesn't retract. I thought to "rebuild it" or change the seals.(I think this is what I should do) The problem is that I can't find the kit anywhere or even what kind of caliper this is. Can anybody help me out?
Thanks, Justin
 

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itsid

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18" ?? that's tough
I'd say you need more like a 9:1 ratio at least

the 110lbs kid will likely be fine with 8:1.. the 200lbs adult might not be.

'sid
 

redflash

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I have epoxied the thermal switch to the lower side of the bldc motor...now I have 2 wires coming from the thermal switch...I know they need to wire (in-Line) with a power wire somewhere....But I don't know where...sid suggested I believe.. into the throttle wire....question...hot ? or ground ?

Thanks
Da Flash
 
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