36v & 48v motor differences

[sonicj]

made some progress today...

got the plastic off, old motor is out! after all i've read, i just knew the rotor was going to be seized on the splines... sucka slid right off! check out the wear on the two brushes. doh!

what is up with all the different sized hardware throughout the cart??? i can just about disassemble my entire car with just 2 sockets! the loose nuts really slow down the process as well. if i knew how to weld i would tack some weld nuts to the frame and make life much easier. i had to drill out some phillips heads holding on the plastic. lame.

check out the broken weld on the frame... looks like someone tried to fix it with a nut & bolt. hmm... time to learn to weld!
-sj

[sonicj]

tried waiting for a warm, dry day but decided its not getting warmer anytime soon. so with the aid of my hairdryer, i finally laid down some paint. 3 coats of high temp caliper paint on top of 3-4 coats of filler primer. for some reason, the red was tough to spray.... after the first coat i couldn't tell what was wet and what wasn't. ohh well, looks better than it did when i dug it out of the scrap yard... definitely sending my next one to get blasted!

sorry for the crap photos... i'll take some with a real camera when its back in the cart.
-sj

[scottyb]

The broken weld is in a typical spot for the CC... they do that. Aluminum welds end to fail if flexed the slightest amount repeatedly... another spot to look for weld failure is in the front underneath where the floor turns up there is a pipe running across the cart welded to each frame member. sorry can't describe it better but I think when you get under there the pipe is pretty clear. so what did you find in the motor? What did you do to it besides the paint?

[oldngray]

Have been reading this thread looking for the "Why" a 36v is faster than 48v.
In my case, I had planned to go from 36 to 48. Could/would you be so kind to explain?

[sonicj]

Originally Posted by scottyb

The broken weld is in a typical spot for the CC... they do that. Aluminum welds end to fail if flexed the slightest amount repeatedly... another spot to look for weld failure is in the front underneath where the floor turns up there is a pipe running across the cart welded to each frame member. sorry can't describe it better but I think when you get under there the pipe is pretty clear. so what did you find in the motor? What did you do to it besides the paint?

whats weird is i've looked at pictures of other's carts and didn't see that crossbar. if its not a structural necessity, i'll just leave the bolt in until i have access to a welder. i know the bar you are talking about.... i'll give it a good look!

im not sure why the shop threw this motor out.... one bolt was sheared off at the end but it was still long enough to be used, plus it was a bolt from one of the brushes so i could have been easily replaced. maybe someone upgraded and didn't want the core so it went in the junk pile. anywho, i didn't fire it up, but it should have worked before i unwound it. besides paint, i removed the stock 6 turns of 8awg and re-wound 5 turns of 4 parallel strands of 14awg.
-sj

[sonicj]

Originally Posted by oldngray

Have been reading this thread looking for the "Why" a 36v is faster than 48v.
In my case, I had planned to go from 36 to 48. Could/would you be so kind to explain?

lol, i can try...

picture a horseshoe electromagnet. less turns of copper = weaker magnet, more turns of the same sized copper = stronger magnet.

ok, so the field coils in the motor are simply electromagnets just like the example above. winding the coils in alternating directions gives us north and south poles. winding one less turn around each iron tooth produces a weaker electromagnet.

this is the part that is difficult to explain without screwing it up as im not a physics instructor nor did i stay in a holiday inn last night. anywho, here we go. when a voltage is applied to a motor, the motor spins as it tries to generate a inversed voltage to match its input. this is known as back electromotive force (back emf). by weakening the magnetic field (less turns = weaker electromagnet), the motor is presented with an increased load as it tries to balance the input voltage. thus, the motor must spin faster in order overcome the additional load presented by the weaker field.

soo.... less turns = faster motor but at a cost of available torque due to the increased load presented by the weaker field. hope that made at least a little sense as its the best i've got to offer at the moment!
-sj

[oldngray]

Heh, I will take your word for it, are you using 48V to turn the 36V Motor?

[sonicj]

haha!

nope. i found a 48v motor at the scrap yard. i rewound that motor with less turns (more speed, less available torque). i pulled out my stock 48v motor and set it aside. im replacing it with the "new" motor and crossing my fingers that i got the winding part right.

so in a nutt shell, i converted a 48v motor into a "36v motor."
-sj

[oldngray]

Myself being Electrically challenged, (amongst other things) your explanation is way over my head however I do appreciate your kind responses.

[sonicj]

well, the project was at least a partial success... the "new motor" functions just as it should! if i don't ease on the pedal, it'll pop from the line with authority that it certainly did not have prior. motor & controller are both cool to the touch after a trip around the block. my only complaint is that im not getting the top speed i was after. i hit 16mph on a stretch i normally average 12-13mph on; i was aiming for about 19mph.

there are still some variables that need to be addressed before i can decide whether this was the wrong wind or not... batteries are still within the break-in period and had been sitting close to a month, allow old brushes to break-in with the new commutator, batteries were not fully charged, check tire inflation, check possible left brake drag, try again when batteries are warm.

its much quicker off the line, just not hitting the top end i want. i suspect moving up to larger wheels/tires might shift the power band closer to the top end. anywho, if nothing else, at least it was a learning experience/confidence builder/reference point/entertainment, didn't cost much, and gives me the satisfaction of knowing i rolled my own.

project costs:
used motor $8.30
magnet wire $10.00
solder $5.00
paint $10.00
total: $33.30