what kind of damage can be caused

[DoorKicker]

by driving and electric cart at slow speeds like in a parade.

Another post got me to wondering about this...

If I drive my cart in a parade at slow speeds, basically crawling, for a few miles at a time, what if any damage could I cause my cart.

Also what should I look out for to avoid this damage or detect it

Thanks all, as always I learn much more than I could ever contribute.

[kgsc]

Much of it depends on which drive system you have. Series carts don't mind as much but Sepex carts may get the motor a little warm. Which do you have?

[Cart Sports]

Yes, the SepEx carts really build heat if you stall them. As long as you keep moving, you should be good. Maybe use short "bursts" and then coast. Most parades move around 2-3mph, so maybe reprogramming the controller to a slower setting could help the cart compensate.

[JohnnieB]

DC traction motors, both series and sepex, can draw more amps and are less efficient at low RPM, so they generate a lot more heat creeping along at walking speed (~3.1 MPH) or less than they do while cruising at a mid-range RPM. (High RPM is less efficient also, but an electric motor cannot draw as many amps at high RPM as it can at low RPM)

Worst case scenario is tall tires and/or high-speed gears, with a motor wound for high speed, towing or carrying a heavy load.

I'm not sure if repeated stops and starts, or continuously adjusting speed to maintain the distance is worse, but both are bad. A steady speed, albeit slow, is best of the bad situation.

Building a cart for parades and daily use presents some challenges, but two speed differentials are available, as well as two speed series motor and multi-mode sepex controllers.

[DoorKicker]

My motor is high torque but I also have 23" tires so I wonder how much I loose?

Hopefully one parade a year wont put too much wear and tear on it. The rest of the time it is normal driving conditions around the neighborhood so I cant justify the two speed differential.

I do notice a whistle in the motor at times. When I am cruising at around 20mph and let off the throttle the motor will make a whistling noise and stop when I push on the throttle again. Is that normal?

[JohnnieB]

Originally Posted by Cart Sports

Yes, the SepEx carts really build heat if you stall them. As long as you keep moving, you should be good. Maybe use short "bursts" and then coast. Most parades move around 2-3mph, so maybe reprogramming the controller to a slower setting could help the cart compensate.

Gradual changes in speed generate less heat, rapid accelerations are less efficient and generate more heat.

As for re-programming a sepex controller for parades, lowering the Max amps would help. If the field mapping is programmable (IE: Curtis 1268 controller). limiting the max field current about 10A would help (or whatever the most efficient low RPM field excitation is for your particular set-up)

[JohnnieB]

Originally Posted by DoorKicker

My motor is high torque but I also have 23" tires so I wonder how much I loose?

Hopefully one parade a year wont put too much wear and tear on it. The rest of the time it is normal driving conditions around the neighborhood so I cant justify the two speed differential.

I do notice a whistle in the motor at times. When I am cruising at around 20mph and let off the throttle the motor will make a whistling noise and stop when I push on the throttle again. Is that normal?

Monitor your motor temperature. If it is staying under 239°F, you aren't shortening its life too much, but thermal damage is cumulative, so try to keep it as low as possible.

Treat the throttle lovingly (slow and gentle moves) and try to maintain a steady speed.

As for the whistling sound, try changing the motor oil in the differential to a gear oil. I use Lucas 85W-140. My differential still whines, but not as loud.
Brush type electric motors also whine and there isn't much you can do about it that I know of.

[HiTechRedNeck]

Just a bit of info...

The AC drive systems (RXV) do not have a heat build up at low speeds.
The gearing in RXV's also allow the motor to spin at reasonable rpm even at 2 to 4 mph.

[JohnnieB]

Originally Posted by HiTechRedNeck

Just a bit of info...

The AC drive systems (RXV) do not have a heat build up at low speeds.
The gearing in RXV's also allow the motor to spin at reasonable rpm even at 2 to 4 mph.

In and of themselves, electric motors have low RPM and high RPM inefficiencies whether they are AC or DC designs. Granted, using an AC motor, a numerically high gear ratio and a VFC (Variable Frequency Controller) mitigates the intrinsic heat build-up vs RPM issues for the RXV, but does not eliminate them.

An electric motor converts electrical energy into mechanical energy and thermal energy. The thermal energy is an undesired output, so the efficiency of the motor is the mechanical energy out divided by the electrical energy in. The higher the efficiency, the less the motor heats up during operation.

Regardless of motor type and the relative flux density ratio generated by the stationary and rotating windings, an electric motor will have its highest efficiency at some RPM. If the motor is operated above or below that specific RPM for the specific motor design, the efficiency will be less, so more of the inputted electrical energy is being converted into thermal energy and the motor's temperature rise will be greater.

I'm just saying that the motor in an RXV will heat up more at low rpm (and high RPM) than it does at a mid-range RPM, without comment or speculation if it heats up as much, or heats up less, or heats up more than a sepex drive of series drive at parade speeds.

[HiTechRedNeck]

I agree completely..

The comment was for someone wishing to START a NEW parade project.
Yes The AC drive system does produce heat as a by product.
The generated heat is not high enough to cause thermal problems for the motor.
The RXV motor also has a thermal sensor feedback loop to controller to protect the system.

The RXV platform might be a good starting point for Parade type applications.

They have NO start up Jerk.. They have extremely smooth acceleration.


Also the programmable top speed and acceleration parameters could be useful
safety features.(yes ,many other controllers are programmable, many are far more customizable than the RXV controller)

Again--
JohnnieB is absolutely correct in his observations and comments.