[Tesseract]

With the large amount of torque the 11" motor puts out would one need high RPM?

Nope. More torque means you can shift to a higher gear earlier. But keep in mind that motor losses are mainly from I^2R, so a smaller motor - within reason! - turning at a higher RPM and lower amps will have less losses than a larger motor turning at lower RPM and higher amps (delivering the same amount of power). For example (not realistic, but instructive), let's say the 9" motor has a field resistance of 0.1 ohm and it needs 300 motor amps at 100 volts to propel a vehicle at 70 mph. The field loss will be 300 * 300 * 0.1, or 9000W (told you it wasn't realistic). Now let's say the 11" motor has a field resistance of 0.075 ohms but requires 400A at 75V? The field losses here are 400 * 400 * 0.08, or 12,000W.

Now, on the flip side, the closer you run a drive train to 1:1 the lower the overall mechanical losses, so the lower rpm motor will have the advantage in that aspect. Then there is the fact that controllers are happiest when operating at 50% duty cycle, because that spreads the losses evenly between switch and freewheeling diode... Lots of factors go into whether a larger/slower motor is better than a smaller/faster motor.

The 11" 250v Kostov is supposed to top out at 5600 RPM.

Sure, but you shouldn't run motors at their maximum RPM if you want them to last a long time. I mean, it's not like at 5599 RPM the motor can run all day but at 5601 RPM it will fling itself to pieces.

 

[Woodsmith]

Tesseract, you have a good point there.

When I go looking for my motor at the breakers they will probably have a selection all at about the same price.
I'm still unclear in my head about lighter 9" running faster to give me 70mph for half an hour or heavier 11" running slower to give the same result.
It would seem that the 9" would have less losses and less weight and run at a higher rpm with more efficiency?
I take it I should also be looking for a 72volt motor more then a 48volt motor to run on a pack that could be in the 120v-160v range?

 

[Tesseract]

Tesseract, you have a good point there.

Erf... Well, maybe, but I wasn't really arguing one way or the other, rather, I was just trying to get people to think a little differently than to simply assume that the larger the diameter/size of the motor the better performing their EV will be.

I'm still unclear in my head about lighter 9" running faster to give me 70mph for half an hour or heavier 11" running slower to give the same result.

Okay, I'll make my example less abstract. Consider the performance graphs of the WarP 9 vs. the WarP 11 at a specific power output of, say, 30hp and 72V:

The WarP 9 needs ~325A to spin at 2200 rpm and deliver ~66 ft-lbs of torque.

The WarP 11 needs ~360A to spin at 1500 rpm and deliver 100 ft-lbs of torque.

Notice how the WarP 9 actually needs less amps to deliver the same power as the WarP 11?

Is this always true? No, of course not. It's just an example, but it happens to be of two very popular motors

I take it I should also be looking for a 72volt motor more then a 48volt motor to run on a pack that could be in the 120v-160v range?

Maybe, maybe not. A motor that is specifically wound for a higher voltage (e.g. Kostov) will have more turns in its field, and require less amps, for a given power output than one that is wound for a lower voltage but with advanced brush timing (e.g. - WarP). Whether the lower amps translates into lower losses, though, depends on a lot of other factors. You really can't make any blanket statements, was more my point (and also that I like to play devil's advocate).

 

[Woodsmith]

Maybe, maybe not. A motor that is specifically wound for a higher voltage (e.g. Kostov) will have more turns in its field, and require less amps, for a given power output than one that is wound for a lower voltage but with advanced brush timing (e.g. - WarP). Whether the lower amps translates into lower losses, though, depends on a lot of other factors. You really can't make any blanket statements, was more my point (and also that I like to play devil's advocate).

To me that says that maybe a higher voltage rating means less advance needed on the brushes and less amps for the same output. That may equate to less to consider and give the option of running it with no advance and at lower pack voltage to begin with and then advance it later as a bigger pack (and bigger understanding) is acqured perhaps.

Still a lot of unknowns to take into account when there are actual motors to look at but I think it gives me a clearer understanding of what to look for, probably still whatever I can afford and then go with it.

Thanks.

 

[major]

at a specific power output of, say, 30hp and 72V:

The WarP 9 needs ~325A to spin at 2200 rpm and deliver ~66 ft-lbs of torque.

The WarP 11 needs ~360A to spin at 1500 rpm and deliver 100 ft-lbs of torque.

Notice how the WarP 9 actually needs less amps to deliver the same power as the WarP 11?

Is this always true? No, of course not. It's just an example, but it happens to be of two very popular motors

Hi Tess,

In your example, both performance graphs show 87% efficiency (+/- 1%) at respective 30 HP points. How can this be Your example just shows that these motor performance graphs suck. We've seen this before in other threads using the 9 inch curve, IIRC. These graphs give you a good ballpark as to actual motor performance, but fall way short in accuracy for doing comparisons.

I've been busy and can't take the time now to elaborate on some of this motor theory. But generally speaking, a larger motor give you more torque, not necessarily more torque per amp. That depends on the design (winding). And pound for pound, the large motor should give you higher efficiency for equal power outputs near the one hour rated loads. But motor designs vary. Some great 9 inchers can do better than crappy 11s.

More from me later

major

 

[Tesseract]

... Your example just shows that these motor performance graphs suck....

Well, I was only trying to argue against the notion that an 11" motor is always better than a 9" motor. I tried to not use an actual example the first time but, well.. read the last few messages to see why I might have resorted to using the WarP 9 and 11...

 

[Woodsmith]

But generally speaking, a larger motor give you more torque, not necessarily more torque per amp. That depends on the design (winding). And pound for pound, the large motor should give you higher efficiency for equal power outputs near the one hour rated loads. But motor designs vary. Some great 9 inchers can do better than crappy 11s.

major

This is the big unknown for me as I will be just selecting from a breakers yard shelf. I wouldn't know if the motor was crappy or not regardless of size or condition. I can't figure any way to find out just by looking yet nor do I know which brands, makes or model numbers to avoid as there are probably too many to consider. It will be a bit of pot luck I guess, and applying what I have gathered from the forum.

 

[Nigel Loller]

Hi
I am new to this forum but have read the entire thread!!! I am going to convert my donar MGF and have been trying to identify the three motors in an 80v Linde forklift..For anyone with problems in this area this is a very useful site that has hundreds of motors used by all the known makes of forklift inc Pump,Traction and steering!
http://www.kelvin.it/engl/attivita/attivita_vendmot.htm
The pump motor I have access to is 13.5 kw at 80volts. Dimensions are 250mm diameter and 300 long not including fan ,which would appear to be about half the power of the warp 9...would I be better off finding a lower voltage motor ,say 36/48 and running it at 120v? Also possible is that it's compound wound as the two main feed wires exit 'thro the winding case and not one from the comm area.If it turns out to be compound is it worth pursuing a viable controller? The two 80v traction motors are series wound but only (continually) rated at 5kw. All feedback welcome

 

[major]

Hi
I am new to this forum but have read the entire thread!!! I am going to convert my donar MGF and have been trying to identify the three motors in an 80v Linde forklift..For anyone with problems in this area this is a very useful site that has hundreds of motors used by all the known makes of forklift inc Pump,Traction and steering!
http://www.kelvin.it/engl/attivita/attivita_vendmot.htm
The pump motor I have access to is 13.5 kw at 80volts. Dimensions are 250mm diameter and 300 long not including fan ,which would appear to be about half the power of the warp 9...would I be better off finding a lower voltage motor ,say 36/48 and running it at 120v? Also possible is that it's compound wound as the two main feed wires exit 'thro the winding case and not one from the comm area.If it turns out to be compound is it worth pursuing a viable controller? The two 80v traction motors are series wound but only (continually) rated at 5kw. All feedback welcome

Hi Nigel,

Some pictures of the motors and nameplates would help. It is difficult to give advice blindly, but what the heck, I'll just throw it out here. Fork lift trucks use a wide variety of motors and motor systems. Lot of them use a single traction motor. Sounds like your 80V truck uses dual traction motors. If so, each could be about half size of the motor for a single drive.

Also, I think you have the 13 kW motor at 15% (for the lift pump). That is the duty cycle. Meaning it is rated for 15% time on out of a 100% DC, likely on a 1 to 5 minute time base. It is basically an overload rated motor because the forks can only go so high, and then the truck travels and lowers before it lifts again. So your 13 Kw 15% motor may be only rated for 5 or 6 kW on a one hour continuous time base, as are traction motors. Because you can drive the truck a long distance without giving the motor a rest.

I try hard not to tell people a certain motor will work for them. Too many unknowns from my vantage point here in Ohio. I do let people know when I think there is a problem. See, I don't even know what you mean by MGF, nor what your performance expectations might be.

I suspect Linde uses well built motors and these could work well for you. Running at higher voltage means you need to watch commutation and advance the brushes if you are into arcing. Also, perhaps active cooling could be needed. And always, you need to get a motor you can control. So, unless you're willing to do a lot of home work or have an uncle who is an EE, stick with series motors which will work with available "good quality" controllers.

How long did it take you to read this thread? Quite amazing the number of posts and views. I wonder if Jim H had any idea how far this would go.

Regards,

major

 

[Woodsmith]

I'm hoping, Major, that the MGF is the MG F sports car so beloved by hairdressers in the UK last decade.
It would be an interesting conversion.

 

[Nigel Loller]

HA Ha Woodsmith
Whats wrong with Hairdressers choice of car ...Lots of good things re MG F
1 very cheap £200 for one in excellent condition
2 electric power steering as standard
3 mid mounted IC rubbish...only lasts for 35000miles or so then head gasket failure,liners,head warps etc all due to plumbing
4 both ends free to fit batteries
5 suspension height is adjustable (form of Hydroelastic)
6 Brake disks on all four wheels
7 only 1100 kilo weight inc batteries
8 some of them ( not mine ) come in British Racing Green ,which as you know still is the best colour for a convertible!!!
How many do you want?
Major,sorry I seem to have replied to you directly which may be unethical?
Nigel

 

[major]

Major,sorry I seem to have replied to you directly which may be unethical?

No apology necessary, Nigel. I don't mind PMs (Personal Messages). That is their function. Just that if I'm going to take the time to express my opinions on the subject and there is nothing confidential about it, I'd rather put it out publicly so maybe others can benefit. And did you see my response PM wrt size

major

 

[Woodsmith]

Any thoughts on this motor on Ebay?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=330383247030&ssPageName=STRK:MEWAX:IT
It is a drive motor for a Toyota 6FBRE16 Fork truck.

It is open to offers and only attracted my attention as it would put a Toyota motor in my Toyota MR2. The seller also has a new pump motor fo the same truck.

 

[jackbauer]

Jeez could the guy have taken a worse photo? Only concern i'd have is its 48v but i'm no expert. Bit expensive too.

 

[Woodsmith]

I think he was trying to show off the brake assembly to justify the price a bit.

 

[JRP3]

Cant see the shaft, or the brushes. Asking price is way high.

 

[Woodsmith]

I've sent a message asking for more details, just out of curiosity.
If I don't win my (it's mine ya hear? All mine!) TransWarP9 then I may think about it and put an offer in if cost wise I can get it the same as one from a breaker plus reconditioning.

 

[Nigel Loller]

Voltage is right,price is X5,very marginal on kw

 

[janee]

I think you like This one car. This is a electric car -> (http://car-n-car.com/2009/12/first-drive-peugeot-ion) and i like this.

 

[JRP3]

I think you like This one car. This is a electric car -> (http://car-n-car.com/2009/12/first-drive-peugeot-ion) and i like this.

Yeah that's a Mitsu iMiev rebranded, and doesn't belong in this thread. Spam bot?