View Full Version : How about this for a motor?...

15 September 2010, 1939

O.k., now I wouldn't have any intention of paying 400 dollars for it, I could get an Etek for that. But since cost is a factor, I could definitely play around with that one for a while. (I am talking about an ULTRA low ball offer here).

It's a forklift motor so in theory it should be able to carry some substantial weight (and probably take a SERIOUS speed hit though). But it's an advanced DC motor, I could probably get it at a reasonable price, and with my controller and throttle that I am going to get, this would make my electric motorcycle probably the cheapest EV in history.

Motor controller, contactor, diodes and resistors: $80

Motor: $150

Throttle: $50

That sounds like a pretty damn cheapskate EV to me :)

BTW, I think this guy did the same thing:

What do you think?

15 September 2010, 1940
330 RPM? I don't know much but that seems kinda low.

15 September 2010, 1948
Yeah, it won't be a speed demon for sure.

But if I blow it up from some damned newbie mistake that I make, I won't really care :)

15 September 2010, 2009
From your other thread
"I am a bigger guy (avid powerlifter) so I am about the size of an NFL lineman, and 300lbs."

This motor would give you all the fun of the build, but next to zero motion. At 2.5hp, It's too weedy!

15 September 2010, 2050
So I take it that the general consensus is no then.

O.k., thanks for the advice all. By the way, there's no guarantee that the seller would even accept a low ball offer like 150. Just a thought.

Thanks again.

Tony Coiro
15 September 2010, 2114
Also, on a scale from one to ten, you don't wanna use a motor with a drive shaft like that.

15 September 2010, 2119
stay away. 330RPM at 24V would be not even 700rpm at 48V. The HP is likely continuous though, so double the RPM, up the current (it'd probably handle it) and you might get some decent power, but you need something in the 3-5000rpm at 72V range.

Not even worth it to mess around with, it'l just gather dust.

16 September 2010, 0959
Got it. Another $150 saved.

Thanks guys!

16 September 2010, 1047
So... then another question (and this is an ultra dumbass question, bear with me folks).

What is the difference between a continuous duty motor and an intermittent duty motor like this one: http://cgi.ebay.com/4-HP-24V-DC-VEHICLE-ELECTRIC-MOTOR-BIKE-PUMPS-GOKART-/230517163586?pt=LH_DefaultDomain_0&hash=item35abe4c642

Were I to find a motor that works in the voltage range that I want, the RPM range that I want... and has the power that I want... but says "Intermittent duty" what does this mean for an ecomodder?

Sorry, I know it's a stupid question but I have to ask. Does an intermittent duty motor have a continuous rating?

16 September 2010, 1111

to wit:
"duty rating

Duty rating refers to the length of time a motor is expected to operate under full load. The motor may be rated as either Continuous duty or Intermittent duty. Continuous duty rated motors are rated to be run continuously without any damage or reduction in life of the motor. General purpose motors will normally be rated for continuous duty.

Intermittent duty motors are rated to be run continuously only for short time periods and then must be allowed to stop and cool before restarting. It is usually possible to reduce the size, weight, and cost of a motor by purchasing an intermittent duty motor. Intermittent duty motors are available with maximum operating times of 5, 15, 30, or 60 minute duties or times.

These motors are sometimes used on devices like garbage disposals or air compressors where the motor operates for a short period and shuts off after the job is accomplished and will not be needed for an extended time period. "

16 September 2010, 1131
Ahhhhh I see. Thanks for the great information man.

So pretty much, no intermittent duty motor would be appropriate for an EV.

16 September 2010, 1134
(Disregard....... n/m)

Tony Coiro
16 September 2010, 1243
Not necessarily, you will not spend a lot of time at peak amperage, it will vary while riding. For example, I might see 250A peak battery side during full acceleration but I will only draw about 60A cruising at 40MPH. Nearly all motors will have both a continuous and peak amperage rating for a certain amount of time at that peak. The relationship between current and amount of "time at that current before bad things happen" is a non-linear relationship, so if your motor says 400A peak for 10 seconds, it doesn't mean 800A for 5 seconds and so on. I will continue to elaborate purely for the sake of unnecessary complexity..... a motor has inefficiencies, lets say it's 90% efficient overall, so 10% of the power going to the motor is turned into heat. It will also be losing heat through radiation and conduction through the motor mount into the frame. The rate of change in temperature will look something like this:

change in temp = (1- Eff. Motor) * Voltage * Amperage - rate of energy radiating away - rate of conduction
change in time............ weight of the motor

Solving those last two rates is something no one in the world wants to do without a computer since the rates will increase with temperature. The point is every motor, whether it says it is or not, has an intermittent rating (based on a lot of ****) and a continuous rating (also based on complicated stuff.) I'm pretty sure what I wrote won't help anyone understand this stuff but I wrote to much not to post it........

16 September 2010, 1245
<<<<------- Head just exploded.

16 September 2010, 1309
them physics guys have that effect on heads- all that tamperin with the elemental forces of the universe and all...

16 September 2010, 1335
Intermittent is fine, you won't hardly ever use peak power on the motorcycle, but its there if you need it. But, if you calculate you need 5hp to move you at 60mph, and you're going to be doing a lot of 60mph driving, you better be sure that the motor meets that spec at the very least.

16 September 2010, 1822
Got it. Thanks guys!

26 September 2010, 0049
Intermittent duty motors are available with maximum operating times of 5, 15, 30, or 60 minute duties or times.
So is it safe to assume that a 10 mile commute at speeds from 40 to 50 mph are a "intermittent duty" for the motor? That is an interesting point you guys have raised, because is lowers the cost of converting.