Posting in this forum despite my project not being a scooter, but it's also not really a car and the motors are basically scooter-class so I figure folks here might have the answers I need.
I'm building a small vehicle that's going to be the base for a Burning Man art car. The speed limit out there is 5 MPH and the terrain is totally flat and level for miles. There can be rough spots and small 'playa snakes' of piled-up dust, but the roads at least are always a good driving surface and that's enough for my purposes.
The goal is to haul 1-4 people and a ton of LEDs and get a range of at least 10 miles on a charge.
This project was originally going to be a motorized couch but got turned into something more car-like, about 6 feet wide and 7 feet long. Because of the couch origins I stuck with differential steering - it drives like a skid steer loader or a tank.
I'm using a pair of MY1020ZX 36V 800W gear motors, one motor driving both wheels on one side. The wheels are 13" mini ATV wheels, and I'm running an Ion Motion Control MCP266 controller.
Today was my first real drive test of the completed frame, and it started out great. Acceleration needs to be limited in software because it's a bit whiplash-inducing, and according to GPS it topped out just at 7 MPH. I'd planned the reduction ratio to get about 5.5 MPH, but picked up a bit more because the motors came with different sprockets than expected. Cornering is not the smoothest and on asphalt it's murder on the tires, but on playa dust I think that would be OK.
The problem is heat. I drove it about 1/3 of a mile in a lap around a few buildings, stopping four different times to chat with auto shop guys who stopped me to ask what the thing was. When I finished the lap I found the right motor smoking and making a very unpleasant smell.
I realize the MY1020 motors have a reputation for not being terribly rugged and I expected their lifespan would be limited, but this version at least has a fan and seems to be rated for what I need. And I figured if I made it 50 miles over the course of a week that would be a success. Only making it 500 yards is another matter.
I grabbed my thermal camera and found the right motor was at least 10 C hotter than the left. By the time I dragged the car back to my shop the right motor was still almost too hot to hold onto, but the left motor was merely really warm.
The rated current on the motors is 26.7 amps. I had the current limiting on the controller set at 40 amps per channel, thinking that I'd only see them draw that much for a few seconds during acceleration and they'd taper off to something reasonable at speed. I spent some time dragging the car around with a force gauge before I had the motors and the rolling resistance isn't bad.
The right motor was slightly damaged in shipping. The fan cover was dented in, but the fan itself turns freely and as far as I could tell the damage was only cosmetic.
I can't find anything to suggest why one motor would run significantly hotter than the other, unless maybe it was just chance that the one motor started failing first and the failure mode results in higher current and more heat. I don't know how these motors behave when they fail.
All of the wheels seem to turn just as easily and mismatches in speed ought to just make it arc (it was maybe pulling slightly left on straightaways) or at worst skid a bit.
I hooked up a laptop to monitor the motor currents and in the very short drive I made they did seem to be frequently at 40 amps, but I didn't get enough of a run on level ground to really get good numbers. I tried again at 28 amps but my testing got cut short when a software glitch caused the controller to stop responding to my steering inputs. I was going backwards and couldn't reach the shutoff switch fast enough and crashed into a curb.
Am I doing something fundamentally wrong here? Are these motors going to draw vastly more current than I was expecting? Could my low-speed maneuvering with the 40 amp current limit and the motors fighting the tires' traction to turn on asphalt have overheated the motors so quickly?
If the one motor was just a fluke I'll happily replace it and try again, but I don't want to smoke another. And if it really does take a combined 50 amps or more to keep it going, I'm not going to get more than a few miles on my 110 AH lead acid battery pack. Assuming a Peukert number of 1.3 I figure 50 amps would drain the batteries in half an hour.
I was really stoked that my vehicle accelerated so well with 500 lbs of battery, frame, and rider and even handled a steep (but short) driveway with ease. But while I don't know electric motors well, but I've been around electronics long enough to know that they don't work if you let the magic smoke out, and this motor has already lost some of its limited supply before I've really begun.
If anyone's got advice on the subject, I'm all ears. I leave 3 weeks from today and if the project is going to happen, I've got to get it figured out soon.
Thanks!
I'm building a small vehicle that's going to be the base for a Burning Man art car. The speed limit out there is 5 MPH and the terrain is totally flat and level for miles. There can be rough spots and small 'playa snakes' of piled-up dust, but the roads at least are always a good driving surface and that's enough for my purposes.
The goal is to haul 1-4 people and a ton of LEDs and get a range of at least 10 miles on a charge.
This project was originally going to be a motorized couch but got turned into something more car-like, about 6 feet wide and 7 feet long. Because of the couch origins I stuck with differential steering - it drives like a skid steer loader or a tank.
I'm using a pair of MY1020ZX 36V 800W gear motors, one motor driving both wheels on one side. The wheels are 13" mini ATV wheels, and I'm running an Ion Motion Control MCP266 controller.
Today was my first real drive test of the completed frame, and it started out great. Acceleration needs to be limited in software because it's a bit whiplash-inducing, and according to GPS it topped out just at 7 MPH. I'd planned the reduction ratio to get about 5.5 MPH, but picked up a bit more because the motors came with different sprockets than expected. Cornering is not the smoothest and on asphalt it's murder on the tires, but on playa dust I think that would be OK.
The problem is heat. I drove it about 1/3 of a mile in a lap around a few buildings, stopping four different times to chat with auto shop guys who stopped me to ask what the thing was. When I finished the lap I found the right motor smoking and making a very unpleasant smell.
I realize the MY1020 motors have a reputation for not being terribly rugged and I expected their lifespan would be limited, but this version at least has a fan and seems to be rated for what I need. And I figured if I made it 50 miles over the course of a week that would be a success. Only making it 500 yards is another matter.
I grabbed my thermal camera and found the right motor was at least 10 C hotter than the left. By the time I dragged the car back to my shop the right motor was still almost too hot to hold onto, but the left motor was merely really warm.
The rated current on the motors is 26.7 amps. I had the current limiting on the controller set at 40 amps per channel, thinking that I'd only see them draw that much for a few seconds during acceleration and they'd taper off to something reasonable at speed. I spent some time dragging the car around with a force gauge before I had the motors and the rolling resistance isn't bad.
The right motor was slightly damaged in shipping. The fan cover was dented in, but the fan itself turns freely and as far as I could tell the damage was only cosmetic.
I can't find anything to suggest why one motor would run significantly hotter than the other, unless maybe it was just chance that the one motor started failing first and the failure mode results in higher current and more heat. I don't know how these motors behave when they fail.
All of the wheels seem to turn just as easily and mismatches in speed ought to just make it arc (it was maybe pulling slightly left on straightaways) or at worst skid a bit.
I hooked up a laptop to monitor the motor currents and in the very short drive I made they did seem to be frequently at 40 amps, but I didn't get enough of a run on level ground to really get good numbers. I tried again at 28 amps but my testing got cut short when a software glitch caused the controller to stop responding to my steering inputs. I was going backwards and couldn't reach the shutoff switch fast enough and crashed into a curb.
Am I doing something fundamentally wrong here? Are these motors going to draw vastly more current than I was expecting? Could my low-speed maneuvering with the 40 amp current limit and the motors fighting the tires' traction to turn on asphalt have overheated the motors so quickly?
If the one motor was just a fluke I'll happily replace it and try again, but I don't want to smoke another. And if it really does take a combined 50 amps or more to keep it going, I'm not going to get more than a few miles on my 110 AH lead acid battery pack. Assuming a Peukert number of 1.3 I figure 50 amps would drain the batteries in half an hour.
I was really stoked that my vehicle accelerated so well with 500 lbs of battery, frame, and rider and even handled a steep (but short) driveway with ease. But while I don't know electric motors well, but I've been around electronics long enough to know that they don't work if you let the magic smoke out, and this motor has already lost some of its limited supply before I've really begun.
If anyone's got advice on the subject, I'm all ears. I leave 3 weeks from today and if the project is going to happen, I've got to get it figured out soon.
Thanks!