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#16 Elecman OFFLINE  

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Posted February 13, 2011 - 03:44 AM

What a lot of people do not know is that electric will have torque figures that far exceed a gas or diesel engine. I think the "weak stigma" that people attach to electrical driven vehicles is that they have seen the performance of golf carts and from this limited observation they make the assumption that it applies to anything that is electrical driven. Golf carts are limited by the under sized motor and current limited to a low value. This results in poor torque performance. The rationale behind doing this is to get maximum run time of a few hours rather than making a pulling monster that lasts 15-30 minutes.

A 8" to 13" beast sized series wound DC motor with 450 to 1000+ amps (depending upon the class you enter into) of motor current would easily win in tractor pulling. Btw, the motor current and battery current are not the same except at one point (explained later). The DC motor controller is basically like a DC-DC converter and therefore the current input will be less than the current output, and those large field wound DC motors are basically like a dead short circuit since the windings are thick bus bar type making it have very low electrical resisatance. It takes very little voltage to pump 1000 amps of current through the motor at standstill. With current limit the motor current will stay pegged at 1000 amps if you have the peddle floored the whole time throughout the pull until enough back EMF (counter voltage produced by the motor turning) from the motor results in the current falling off where the controller will no longer need to limit current.

There is one point where the battery current equals motor current. This occurs when the full battery supply voltage is finally fed (after all, current limit works by limiting voltage such that the current is kept at the set value that was programmed into the controller) to the motor and the motor has not generated enough back EMF yet (motor has not reached full load speed yet). This is very brief. Other than that there is no other point where the battery current equals motor current. So battery problems are not a super big deal.

What is interesting since we are on the subject of pulling. Someone has bet me $60 that my electric go kart cannot out pull his STOCK Roketa 250cc ATV. I tried to explain to him, but I guess he wants to give his money to me..:bounce:My 6.7" motor produces 39.5 ft*lbs at zero RPM with 300 amps current limit up to some cutoff point that I did not measure (where the controller is no longer in current limit mode and the motor current is decreasing below 300 amps when throttle is floored the whole time) and the HP is about 15. My gear ratio is 5.45:1 with a tire diameter of 1 foot. My pulling force will be 430 pounds. I looked up the specs of 250cc engines and I got to tell you, they are terrible when it comes to torque. It would take at least a 15:1 ratio just to have the same pulling force if the tires were the same size and I know for a fact that stock ATV's of the 250cc kind in first gear and the sprocket ratio combined is not going to be 15:1. Not to mention I weigh in excess of 500+ lbs (65% rear and 35% front weight distribution) which the ATV is like 230ish or so lbs.

I'll post an update after I win my $60 of how it all went down. :smile1:

#17 DH1 OFFLINE  

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Posted February 13, 2011 - 10:21 AM

2 more videos of electric racers




Edited by DH1, February 13, 2011 - 10:32 AM.


#18 jonsteffen OFFLINE  

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Posted February 14, 2011 - 09:03 AM

they may not be like a normal pulling tractor but maybe this is a picture of the future of tractor pulling
this might be a good think lets see also i think these electric tractor might have more power because the wont bog down like a normal tractor does the only way it might bog down if you don't have the batteries fully charged that is my 5 cents on this

#19 DH1 OFFLINE  

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Posted February 14, 2011 - 05:06 PM

Those 3 videos , pulling tractor, drag bike, and dragster what those guys are doing to those motors they will not last for contiuous use but for short spurts you can get away with it.
I think the drag bike has 2 motors, that are run at 350volts or something like that 2 to 3 times the rated voltage for them, that's how they get so much power out of them.
How much power would your 110volt electric drill have if you ran it on 220 volt, and how long would it last.

#20 thirdroc17 OFFLINE  

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Posted February 14, 2011 - 05:16 PM

My electric drill run at 220 volts with little load will last a lot longer than say, a nitro burning funny car trying to make a cross country trip, which is also running at light load.

Just like internal combustion engines, designs vary by performance and intended use.

Internal combustion engines have been tinkered on for years, while electric motors have largely been ignored. Don't underestimate an electric motor, they ARE what pull mile long freight trains all over the country.

#21 Elecman OFFLINE  

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Posted February 15, 2011 - 12:29 AM

The Lawless drag bike uses a GE 13" monster that propels it down the 1/4 mile at 177 MPH in 7.46 seconds.

http://www.youtube.com/watch?v=e4_64trQ71g

More info here: Orange County Choppers and Lawless Industries Take a Brand New Beast Down the Dragstrip to Clutch the Quarter-Mile World Record «

That video of the electric dragster rail that you posted, DH1, also uses a 13" GE motor. In fact if I am not mistaken the guy that owns that dragster sold the GE 13" motor out of his Smokescreen S-10 to Lawless for his drag bike.

Here is what the motor looks like: Current Eliminator

A good forklift scrap yard should have some GE 13" forklift motors. I'd be careful not to explain the torque abilities of electric to scrap yard owners or they will charge insane prices for these. If too many people know of the electric's torque vs gas, they might charge more for the electric if they are trying to sell it.

I read some post on here that someone bought a used 9.1" for like $400 that cost $2500 new. I hope to find someone like that so I can get a torquey motor for that price!:smilewink:

I would love to see a GE 13" setup tractor pull a sled. That would be insane. Traction would be a problem for sure as well as parts strong enough to take all that torque.

#22 DH1 OFFLINE  

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Posted February 15, 2011 - 04:27 PM

The Lawless drag bike uses a GE 13" monster that propels it down the 1/4 mile at 177 MPH in 7.46 seconds.

I read some post on here that someone bought a used 9.1" for like $400 that cost $2500 new. I hope to find someone like that so I can get a torquey motor for that price!:smilewink:


Yes you did it's mine and here it is.
electric massey 018.jpg

Here's a link to info on this motor.
If you could feed it enough amps it has a stall torque at 0 RPM ratting of
1077 ft lbs at 144volts
>Motor ADC (AMD - Advanced Motors & Drives) 9.1" #FB1-4001A 72-144VDC 19.5HP Double Shaft

Attached Thumbnails

  • electric massey 019.jpg


#23 Elecman OFFLINE  

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Posted February 16, 2011 - 02:11 AM

It's current that give DC motors torque. So it takes 3,460 amps to produce 1077 ft*lbs. I suppose you plan to use this motor in a tractor pulling class? Heck, at only 1770 Amps you get 551.2 Ft*lbs which would take on quite a bit of the competition.

Btw, where it says ".03I" that is the voltage drop you get when you multiply the current with the .03, which is the actual voltage that is getting to the motor. At 75v applied the motor will actually see 21.9 volts at stall. The electrical resistance of the motor is about .012 ohms! With some good 0000 AWG welders wire and a 2000 amp version of the Zilla controller you would be rocking big time. A bigger motor like a 13" takes less current for the same torque which could allow you to use the 1000 amp version of the Zilla controller which can save you some money. If you come across a GE 13" monster for a good price you should buy that puppy up quick.


If just so happens that the guy driving that tractor in the OP's youtube video also used a AMD 9.1".

He posted a link to his Facebook album: Building the prototype electric tractor "Fully Charged" | Facebook

#24 DH1 OFFLINE  

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Posted February 16, 2011 - 05:26 PM

That ADC 9" motor was advertised on Kijiji, I got the #s off it before I went to look at it, found out what it was and that it is a popular choice for an electric car. Bought it for use in an electric car but I think it's going to end up in a tractor something like this.
Jubile 002..jpg

Cheaper easier and in the long run more useful. If I make an electric car I need 80km+ range to get back and forth from work.

#25 coldone OFFLINE  

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Posted February 16, 2011 - 09:15 PM

How do they manage the heat?

If they could manage a way to hear the current flow i bet it would sound like a nitro blown engine. I f they could every develop a a true power source then everything will be electric.

#26 Sparky OFFLINE  

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Posted February 17, 2011 - 06:16 PM

Another consideration of the electrics is that a porportional amount of total load power desired is also disipapated in the batts and cabling. The kicker is that for max power desired total the same power at the wheels is disipated in the batts. Z source = Z load for FULL POWER. The approx same current in both times whichever Z says things are a happening. Few practitioners give this much thought. Edit- For those who caught it , The exponential factor of current squared applies. As current doubles the power quadruples. Conversely as load Z increases from optimum power value , the batts accumilate less heat. Parralel batt backs have obvious advantages. One additional thought - The load ballast resitors also help limit peak batt heat. All depends on how you want to romp and stomp!!

Edited by Sparky, February 18, 2011 - 01:11 AM.
Make the post more accurate


#27 Sparky OFFLINE  

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Posted February 20, 2011 - 01:58 PM

OK - so it finally hit me what else is missing in batt heating discussion. Motors are rated in max permissible temp rise from room temp. I do not recall any such data about batts. If engineers have it , it probably wont be released. We are on our own for now. :wallbanging:

#28 Elecman OFFLINE  

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Posted February 21, 2011 - 12:42 AM

Another consideration of the electrics is that a porportional amount of total load power desired is also disipapated in the batts and cabling. The kicker is that for max power desired total the same power at the wheels is disipated in the batts. Z source = Z load for FULL POWER. The approx same current in both times whichever Z says things are a happening. Few practitioners give this much thought. Edit- For those who caught it , The exponential factor of current squared applies. As current doubles the power quadruples. Conversely as load Z increases from optimum power value , the batts accumilate less heat. Parralel batt backs have obvious advantages. One additional thought - The load ballast resitors also help limit peak batt heat. All depends on how you want to romp and stomp!!

What you are referring to is the maximum power transfer theory which occurs when the electrical load is at 50% efficiency. This is where the DC motor produces maximum horsepower. This is only achieved by loading down the motor until it becomes 50% efficient. In practice this is not a good idea to do because although traction motors use class H insulation, at 50% efficiency the heating of the windings will be well beyond the rating of the enamel insulation. The best approach to get more power is to take a low voltage rated motor and over volt it, but to ALWAYS remember to gear it down lower when over volting.

The benefit of this is you get more HP without heating up the motor from the other method of overloading the motor to 50% efficiency and it is more efficient. For example my electric go kart's motor is rated for 36 volts DC, but I am running it at 72 volts with a 5.45:1 gear reduction to account for the increased voltage.

In pulling if both identical motors had the same current limit of say 300 amps then they both will have the same peak torque and lets say both vehicles with all else being equal (except gear ratio) were geared to top out at 15 MPH, then the vehicle ran at the higher voltage will have more pulling force, because the gear ratio will have to be lower to keep it at 15 MPH, which in turn is a greater multiplier for torque at the wheels vs the low voltage ran motor that must use a higher ratio to achieve the same speed, hence reducing their torque at the wheels.

That is not say that going to higher in voltage is not bad, but usually a stock DC motor can handle twice the rated voltage without much severe sparking of the brushes contacting the commutator. In drag racing they employ a few "secrets" although it's not really all that much of a secret to run motors well beyond their rating of at least 4 to 5 times.

OK - so it finally hit me what else is missing in batt heating discussion. Motors are rated in max permissible temp rise from room temp. I do not recall any such data about batts. If engineers have it , it probably wont be released. We are on our own for now.

With DC motor controllers the battery current does not equal the motor current except at one data point. This is not like a series circuit, but more like a DC-DC switching power supply converter. That is not to say that pulling 400 or so amps from a 72 volt battery supply to get 1000 amps of motor current at 28 volts (if 100% efficient) is not stressing the batteries because it certainly is. That is why premium $1000+ motor controllers like the Zilla controllers also support battery current limit.

#29 DH1 OFFLINE  

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Posted February 21, 2011 - 08:47 AM

This little Sears that I converted has a 12volt starter/generator in it and I'm running it at 24volts, the motor does get hot but it doesn't get used enough non stop to burn it up so far. 45 minutes non stop use and it's to hot to put your hand on it.
This motor running on 12volts doesn't have enough power to move along especially in the higher gears on grass uphill. At 24volts it has a lot more enough to run on grass uphill, I tried 36volts and again faster, more powerful but I figured I was pushing it too much and would burn up the motor a lot quicker than running on 24volts.
At 24 volts it seems OK, similar to the gas version, but the gas one would still have more power in top gear on grass going up a steep hill.


#30 Sparky OFFLINE  

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Posted February 21, 2011 - 11:23 AM

Doug - Thanks for letting out some of the secrets of out of envelope performance. Would you have any guess of batt capacity used typically?




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