My school is making our second car and thought about a brushless hub motor, does anyone know advantages/disadvantages of a hub motor and a traditional electric motor?
ProEV said
Jan 19, 2015
Hi Ryan,
We are running an AC motor of uncertain parentage. It is a little heavy but quite powerful. If I was building from scratch, I would look closely at the larger radio control hobby motors and bicycle hub motors.
The RC motors are very light and efficient. Their price is very reasonable. They are brushless DC. Look for a controller that allows regenerative braking which is a big advantage especially getting through traffic. We are running the Kelly mini brushless controller ($235) that is suppose to work well with brushless DC.
The Electrocutioners have experience with this type of motor and might be able to tell you more.
Hub motors also seem to have a lot of potential. Since they are mostly for the electric bicycle crowd, many of the controller s do not do regen. Again, the Kelly controller is a reasonable option for regen.
The other thing to keep in mind is that since electric bicycles magically turn into electric mopeds if they have too much power, most hub motors are rated for only 500 watts. Electrathon battery packs should have a capacity of between 750 Watt hours and 1,000 Watt hours. This means if you have a motor rated for 750-1,000 watts and run it flat out the whole race, you can use all your energy. With our tight courses, it would be better to have a more powerful motor that allows you to lift off the power going into the corner and apply more power on corner exit.
It might be worth looking at running hub motors on more than one wheel.
USF was running a hub motor two years ago but I am not sure if any of that crew is still around.
There are some excellent options out there that are light and inexpensive compared to the traditional choices. Two good sources of information are endless-sphere.com and visforvoltage.org
Ron said
Jan 21, 2015
I have thought about hub motors but have stopped short of using my limited funds because most electric motors run at their most efficient point at a specific RPM...
above or below that RPM the motor uses more power (sometimes a great deal more) to move the vehicle.
Now if you know that your most efficient rpm will be the speed that the car will be running at for 90% of the track you are on you are fine...
BUT if you are racing on short and twisty tracks (like most of the ones we race on out here in the Pacific Northwest) then you will be burning lots of your power at less than optimal RPM's.... also hills can have a similar effect, and in Oregon we have some races that have between 15 and 40 feet in elevation changes... and trust me, the downhill coasting doesn't make up for the climb!!!
Therefore we use a motor that we can change sprockets on to get the best "happy medium" of speed and power for a given course to keep it in it's "happy spot" for most of the track... most cars are running E-tec but there are some mars and a couple of lynch motors.
this being said, I still dream about hub motors to use when we race at Portland International Raceway for the "long track" event
(1.9 mile road course, only about 10 ft of elevation change)
Hope this helps....
Ron J northwest region cars #13 & #14
ProEV said
Jan 22, 2015
The efficiency of the motor is vital but different types of motors have different efficiency curves. It might be that the advantages of a specific hub motor might include a broad enough efficiency curve to match the speed range of a tight course.
There are some interesting motor efficiency graphs that give some idea of motor capabilities. I like the one here with the ability to change the parameters and see the effects. http://www.ebikes.ca/tools/simulator.html. Choosing recumbent bike and 350 weight should be close to most electrathon vehicles.
My school is making our second car and thought about a brushless hub motor, does anyone know advantages/disadvantages of a hub motor and a traditional electric motor?
Hi Ryan,
I have thought about hub motors but have stopped short of using my limited funds because most electric motors run at their most efficient point at a specific RPM...
above or below that RPM the motor uses more power (sometimes a great deal more) to move the vehicle.
Now if you know that your most efficient rpm will be the speed that the car will be running at for 90% of the track you are on you are fine...
BUT if you are racing on short and twisty tracks (like most of the ones we race on out here in the Pacific Northwest) then you will be burning lots of your power at less than optimal RPM's.... also hills can have a similar effect, and in Oregon we have some races that have between 15 and 40 feet in elevation changes... and trust me, the downhill coasting doesn't make up for the climb!!!
Therefore we use a motor that we can change sprockets on to get the best "happy medium" of speed and power for a given course to keep it in it's "happy spot" for most of the track... most cars are running E-tec but there are some mars and a couple of lynch motors.
this being said, I still dream about hub motors to use when we race at Portland International Raceway for the "long track" event
(1.9 mile road course, only about 10 ft of elevation change)
Hope this helps....
Ron J northwest region cars #13 & #14
The efficiency of the motor is vital but different types of motors have different efficiency curves. It might be that the advantages of a specific hub motor might include a broad enough efficiency curve to match the speed range of a tight course.
There are some interesting motor efficiency graphs that give some idea of motor capabilities. I like the one here with the ability to change the parameters and see the effects. http://www.ebikes.ca/tools/simulator.html. Choosing recumbent bike and 350 weight should be close to most electrathon vehicles.