new rebuild-low torque

[champ1956]

I have a 1995 TXT that I have totally rebuilt over the winter. I took it on the maiden run this morning and it's faster than it was but I was expecting more.
It ran decent on flat ground but struggled on a little grade.As this will be used at the beach the motor I chose was for speed and not hills but it really slowed down more than I think that it should.. Haven't checked the speed yet but it started snowing so I headed for the house. When I started to back up into my shop the cart had much more torque in reverse...as in a world of difference. Is this normal or did I cross something up? I will list the motor and controller info.
Thanks for your help
curtis high amp solenoid...curtis 500a controller,22" tires....4ga cables....amd 6hp motor....and a HD forward/reverse switch

[Zincode]

I dont know the answer but I wanted to follow this. I have read that larger tires decrease torque. But I dont know your original set up.

Sent from my SM-G960U using Tapatalk

[champ1956]

Original setup was straight off the golf course

[JohnnieB]

If it is cold enough to snow (about 30°F or so), the battery temperature is about 50°F below the temperature they were rated at (80°F), so their storage capacity is roughly 70% of their rated capacity and the less their storage capacity is, the more the voltage drops when amps are drawn, which in turn reduces the number of amps that the motor will draw, which in turn lowers torque. In addition, the chemical reactions that produce amps are less intense in colder temperatures, so fewer amps can be produced.

In other words, your cart will preform better when it gets warmer.

On the other hand, there are other performance factors to take into consideration, or should have been.

Motors in the same sized case wound for high speed have less torque than motors wound for standard speed and motors wound for high torque. However, there are motors in physically longer cases that can be wound for more stock speed and above stock torque.

Taller than stock tires increase speed (theoretically) due to traveling further on the ground per revolution, but in doing so, the amount of force applied where rubber meets road is reduced. Your 22" tall tires should increase cart speed by 22% while reducing torque by 18%.

If the tires happen to be the low pressure type (<10PSI max pressure), they take more torque to turn and the cart's speed may actually be slower than stock speed.

Also, if the tires have an aggressive tread pattern, they are harder to turn than milder tread patterns (On-road or Turf patterns turn easier than mud and sand patterns.)

Since it is a Curtis controller, I suspect it is a 36V system. If so, going to a 48V system will up the speed and torque by 33%.

The 4Ga cable size is marginal for a 500A controller. Attached is an aftermarket controller manufacturer's recommended cable thickness for controller with various throughputs.

Do any of the cables or f/r switch get more than about 10°F above ambient after a hard run?

As for reverse having more torque than forward, there isn't much that can be done about that short of turning the rear axle around so the motor spins in the opposite direction for forward, or having the brush timing changed. (If it is the brush timing is offset and CCW rotation truly has more torque than CW)

[champ1956]

True but it would have the same result forward or backward and there is a noticeable difference

[JohnnieB]

Originally Posted by champ1956

True but it would have the same result forward or backward and there is a noticeable difference

Only the last sentence of Post#4 addresses the possibility of forward and reverse having different amounts of torque.

Go to this site and scroll down and read "The commutating plane" section.
https://en.wikipedia.org/wiki/Brushed_DC_electric_motor

I suspect the brushes in your motor are shifted slightly from being exactly 90° to the magnetic field of the stator windings, giving the motor a bit more torque when spinning in one direction than the other.

I've never heard of this being done before, but you might try loosening the motor's end cap, twisting it (by hand) as far as it will go in one direction and re-tightening it. If the makes it better-great. If it makes it worse, try twisting the end cap in the other direction.

[champ1956]

I finally got to check my speed today. 14 mph forward.... 21 in reverse quickly before I lifted. What if I reversed the wires on the FR switch? Are these things
Programmed to be limited in reverse verses forward?

[JohnnieB]

Originally Posted by champ1956

I finally got to check my speed today. 14 mph forward.... 21 in reverse quickly before I lifted. What if I reversed the wires on the FR switch? Are these things
Programmed to be limited in reverse verses forward?

Typically reverse is half speed, but the unknown controller may not have that feature.

Go ahead and try reversing either the armature or the stator cables, but not both.

[Fairtax4me]

Sounds like you got something mixed up and your controller is giving you half speed reverse for forward. Just spitballing, Need a model number for that controller to help much more than that.

[champ1956]

Curtis 500A