# New user, planning custom build



## gmijackso (Sep 30, 2008)

First I'll start with I'm new here and new to the thought of building an EV myself. I hope this is in the right place (since the build isn't solidified yet, but is technically under way). I'll appologize in advance if it isn't.

Here's my plan. I would like to build a 2 seat custom vehicle (as opposed to an mod of an existing vehicle). Something similar to the Rixster, this, I even like the specs at 50 Mph and 50 Mile range or so. Two seats with a little room for some cargo (think grocery store) and maybe plan for something towable to extend range. I stumbled onto (what I believe to be) an awesome deal and bought some parts this past weekend. Here is what I've got going so far.

Stats are from data sheet, not from testing at this moment.
*Motor: LMC (Lynch Motor Company) LEM-200-127*
Weight: 11Kg (24.25 lbs)
No Load Current: 5A
Peak Power: 16.08 kW (21.56 HP)
Peak Efficiency: 88%
Peak Current: 400A
Rated Power: 8.55 kW (11.46 HP)
Rated RPM: 2592
Rated Voltage: 48V
Rated Current: 215A
Rated Torque: 31.5 Nm (23.23 ft. lbs.)
Motor link

*"Controller": MagnaDrive*
I don't really have a lot of stats on it, but it used perminant magnets with a variable air gap to to couple the motor to the output shaft. This allows the motor to free run at max speed while allowing the output shaft to be variable from 0-100%. The website can explain it better than me, but supposidly is quite efficient (I was told about 1.75 x PWM battery life).

That's what my plan A is currently, for a start. I figure light is going to be key, as it almost always is. The Rixster is only like 250lbs curb weight, and gets their specs using a 6 HP motor and Lithium batteries. I plan on going with an Aluminum frame, but I'm cheap and don't know if I can afford the lithium batteries.

So here are my starter questions...
Does anybody know anything about the products I've posted, or have any experience with them?
With the items I speced is it possible to obtain similar results to the Rixster?
With the extra HP my motor has, what are the odds of getting away with flooded lead acid batteries and still coming close to my speed/distance goals?
I figure I need about 350 AH (back of hand calculation) of battery storage to achieve those goals does that seem about right?
Any other thoughts/suggestions?
Thanks in advance for your ideas. I'm unbelievably excited about this project. If you don't think that motor/"controller" will do, let me know, I have a plan B already in mind, all part of this crazy deal I got this weekend!


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## major (Apr 4, 2008)

gmijackso said:


> *Motor: LMC (Lynch Motor Company) LEM-200-127*
> 
> *"Controller": MagnaDrive*
> 
> ...


Hi gmijackso,

I have never used either of the components you chose. But I'd advise against both. Those axial motors look good on paper, but many find them not to be durable for EV propulsion. Maybe in a real light vehicle, but I advise to get a good solid wound field motor. For a light car, a 6.6 inch motor would probably suffice and cost much less and prove more durable.

As for that variable speed coupling, forgetaboutit. You need a motor controller, not a load controller. Those might work in some stationary applications for constant duty with only slight speed variation. For EV propulsion, I bet they would suck. It would provide no current limiting for start up or overloads, like hill climbing. So what are you planning to do? Leave the motor running continuously? Bad idea. Go with a standard PWM motor controller.

You don't say what voltage system you plan, but 350 Ahr batteries sound big. Not really compatible with a light weight car.

I recommend you take the path well traveled for your first conversion. KISS and you'll be on the road years sooner and bucks ahead.

Just my opinions,

major


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## TX_Dj (Jul 25, 2008)

gmijackso said:


> This allows the motor to free run at max speed while allowing the output shaft to be variable from 0-100%.


Interesting. I don't know about the lynch, but if you let a series-DC motor "run at max speed" without a load, it will overspeed itself in a heartbeat and you'll find the insides in tiny pieces.

Also, peak torque is nearer to 0 RPM than max RPM on most motors that I've seen for traction use.

Something else to consider, it sounds like there's more parts in that... more parts = greater chance of failure?

Granted I know nothing about it... so I could just be paranoid...


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## frodus (Apr 12, 2008)

Even if that vehicle is lightweight, that 25lb lynch motor seems a little undersized. Its good for motorcycles and such, but anything with 4 wheels and lots of drag, is going to need something more along the lines of a series wound 6.7" motor or larger.


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## gmijackso (Sep 30, 2008)

major said:


> Maybe in a real light vehicle, but I advise to get a good solid wound field motor. For a light car, a 6.6 inch motor would probably suffice and cost much less and prove more durable.


Well cost is definately a factor, I'm cheap... I already have the parts mentioned above, so I doubt that anything I don't have is cheaper than the things I do have . I got a small lot of motors and parts for a song and a dance, so that is why I'd "picked" the items above. It is the most powerful motor of the lot, with the simplest and most efficient load controler.



major said:


> As for that variable speed coupling, forgetaboutit. You need a motor controller, not a load controller. Those might work in some stationary applications for constant duty with only slight speed variation. For EV propulsion, I bet they would suck.


Did you happen to look at the site? There is a video of an installation on a water pump and shows the load controller in use. The video makes it seem as though complete variation of speed. What are some of the reasons it woud not work in a similar fashion?



major said:


> It would provide no current limiting for start up or overloads, like hill climbing.


From what I understand of the "controller", the limiting is provided my the magnetic coupling. If the load were to increase beyond a certain point, the magnets will slip keeping the load from even being visable to the motor. This is of course provided you're not all the way into the speed (100%) and even then there is no physical connection from the load to the motor and will still slip if met with the right resistance. Will this not be adequate?



major said:


> So what are you planning to do? Leave the motor running continuously? Bad idea. Go with a standard PWM motor controller.


That was kinda my plan. With a no load current of 5A I don't really see what it would hurt. What are your concerns?



major said:


> You don't say what voltage system you plan, but 350 Ahr batteries sound big. Not really compatible with a light weight car.


I was planning on running the motors recommended voltage of 48V. I came up with the 350AHr number by figuring that if I get somewhere near my 50 mph goal and want a 50 mile range, that means I have to be able to drive for a little over an hour, figure 1.5 hr. Since the motor draws 200+amps, that comes to 300+ AHr. Once you figure some inefficiencies in there I figured 350 was about right.

I agree that 350AHr and light don't go hand in hand, but the other option is to reduce expectations, which I'd prefer not to too much.

Thanks so much for your thoughts. I really am new to this area. I'm the type of person that really needs to understand things completely before I can come up with a solution to the problem. So if something I'm planning is a problem please try to explain how it's a problem for me to understand.


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## gmijackso (Sep 30, 2008)

TX_Dj said:


> Interesting. I don't know about the lynch, but if you let a series-DC motor "run at max speed" without a load, it will overspeed itself in a heartbeat and you'll find the insides in tiny pieces.


I was concerned about overspeeding myself, but correct me if I'm wrong, I don't believe this to be a series wound motor. I believe it is a perminent magnet motor, which is less likely to overspeed, and it will have some load since the magnadrive is always coupled to the motor and always spinning the motors magnet plate.



TX_Dj said:


> Also, peak torque is nearer to 0 RPM than max RPM on most motors that I've seen for traction use.


From what I understood of this motor (there's a chart here) it has a torque constant of .15Nm/A. Here is a graph of the motor being used as a generator. You should be able to use that same graph (nearly) to get some graphical representation of how it runs as a motor as well. 



TX_Dj said:


> Something else to consider, it sounds like there's more parts in that... more parts = greater chance of failure?


I totally agree with this. These are the parts I have though and looks like they might work so why not give it a shot right?



TX_Dj said:


> Granted I know nothing about it... so I could just be paranoid...


I don't know much more about the parts than you do, I just looked over the websites. I'm just not paranoid, I'm hopeful. I guess that's the difference in being the guy with the parts as opposed to the third party lol. I want it to work much more than I'll allow my paranoia to set in.


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## gmijackso (Sep 30, 2008)

frodus said:


> Even if that vehicle is lightweight, that 25lb lynch motor seems a little undersized. Its good for motorcycles and such, but anything with 4 wheels and lots of drag, is going to need something more along the lines of a series wound 6.7" motor or larger.


I thought so too, but then I found the Rixster I posted above that is meeting my goals with a 6Hp motor. If it can be accomplished with 6Hp and 4 wheels, why not with 11Hp and 4 wheels? Maybe just my wishful thinking, but it seems logical right?

As a side note, the guy I got the motor from (supposedly Lynch's grandson, he did have the same last name) had it in a motorcycle at one point, and crashed at 90+mph and apparently lost the bug for EVs.


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## frodus (Apr 12, 2008)

gmijackso said:


> I thought so too, but then I found the Rixster I posted above that is meeting my goals with a 6Hp motor. If it can be accomplished with 6Hp and 4 wheels, why not with 11Hp and 4 wheels? Maybe just my wishful thinking, but it seems logical right?


Thats 6hp at 36V though, higher voltage will likely gain you more HP. Lots of those series wound are made for higher voltage (or can be higher voltage). at 36V it puts out 6hp. The LEM 200 is rated for 11hp at what, 72V? the Rixster is a larger motor.

Also, for those smaller perm pancake motors, I don't think there's a built in fan for cooling. 11Hp is likely not continuous, so 50 miles is going to be hard on it. The rixster is series wound, and has tons of thermal mass for good heat dissipation. USUALLY 25lbs of motor = 25lbs of torque... so you do the math... what would it take to push a 500lb vehicle and a 150lb rider at a decent acceleration? Well, if you wanted to be able to get to 50mph, you might need more than 11hp.

Also, that electrical "clutch" for varying the input to output is NOT a transmission. If you do 0%, the motor will be unloaded. It can speed up, but since its a perm mag, it won't overspeed. You're still only going to have 25ftlbs going through the "clutch" as a max, and your RPM's will be the max motor RPM's. Simple is better, use a gearbox, set it for 50mph and let her go. Its lossy, there is no coupling to your wheels from the motor. So, to start out at 0mph, you'll have the motor spinning at say 3000RPM, and start to engage the "clutch" system, and it'l put out almost NO torque, and slowly increase RPM as you "engage". 

I seriously doubt his claims on speed and range for the rixster


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## major (Apr 4, 2008)

gmijackso said:


> > I already have the parts mentioned above,
> 
> 
> So after it fails, you can buy a good motor.
> ...


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## gmijackso (Sep 30, 2008)

frodus said:


> Thats 6hp at 36V though, higher voltage will likely gain you more HP. Lots of those series wound are made for higher voltage (or can be higher voltage). at 36V it puts out 6hp. The LEM 200 is rated for 11hp at what, 72V? the Rixster is a larger motor.


Did you look at the links I provided at all? The LEM 200 is rated at 11hp continuous at 48V. It is rated at 20+Hp peak.



frodus said:


> Also, for those smaller perm pancake motors, I don't think there's a built in fan for cooling. 11Hp is likely not continuous, so 50 miles is going to be hard on it. The rixster is series wound, and has tons of thermal mass for good heat dissipation. USUALLY 25lbs of motor = 25lbs of torque... so you do the math... what would it take to push a 500lb vehicle and a 150lb rider at a decent acceleration? Well, if you wanted to be able to get to 50mph, you might need more than 11hp.


The motor is vented as the pictures at the site show, and as I recall has a "fan" on the back end of the motor I'll have to take a closer look, but even if I have to force air cool it no big deal. It says very clearly on the motor that it is 11Hp continuous. 



frodus said:


> Also, that electrical "clutch" for varying the input to output is NOT a transmission. If you do 0%, the motor will be unloaded. It can speed up, but since its a perm mag, it won't overspeed. You're still only going to have 25ftlbs going through the "clutch" as a max, and your RPM's will be the max motor RPM's. Simple is better, use a gearbox, set it for 50mph and let her go. Its lossy, there is no coupling to your wheels from the motor. So, to start out at 0mph, you'll have the motor spinning at say 3000RPM, and start to engage the "clutch" system, and it'l put out almost NO torque, and slowly increase RPM as you "engage".


I agree it is not a transmission, and I didn't claim to be trying to use it as one. I suggested that I would possibly try to use it as a speed controller. I understand that there will need to be some gear reduction to modify the rpm/torque range to the final drive. I'm still not hearing why it won't work as the speed controller I suggested? 

So the motor is turning "zero" load at max rpm drawing 5 amps. As I begin to increase load, the rpms will drop some with the load, and the current is going to increse thus creating more torque. At some point the amount of torque created beats out your static friction and you begin to move. What am I missing?



frodus said:


> I seriously doubt his claims on speed and range for the rixster


That may be the case, but at this point I can't prove or disprove his claims. He is apparently attempting to sell this as a modification to just about any golf cart, so I suspect that there would have to me at least some truth to his claims.

Most people I find here with real world data are doing MUCH heavier builds, or motorcycles that are lighter.


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## gmijackso (Sep 30, 2008)

major said:


> Yeah, I watched it. The thing looks like a slip clutch. Bet it waste a lot of power. Large diameter and air cooling is probably what keeps the thing from melting.


Then you saw less power being drawn by the motor using the magnadrive than by restricting output flow of the pump. How is using less power a waste of power?



major said:


> I don't think so.


Can you be a little more descript? 



major said:


> 0 amps at 0 RPM is better. And how do you get it up to speed in the first place? Or you leaving it run 24/7?


Um... how about a switch? It's kinda how ICE engines work right? Or am I supposed to let the ICE run 24/7, I thought that was what the key was for? And realisticly, wouldn't keeping the brushes from arcing and drawing a ton of current through many starts in a trip lengthen the life of the motor a ton? Five [email protected] 48V sitting at a stop light for even 5 minutes will draw 20whrs, seems like a fair trade for motor life right?



major said:


> Your plan sounds like a problem to me, but what the heck? You got the parts, go for it. I am certain you will be disappointed. But you'll learn what not to do.


Again, can you be more descript. I'm open to the idea that this is a failing idea, but other than "it's not what is normally done" I haven't really gotten a reason for failure.


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## major (Apr 4, 2008)

> How is using less power a waste of power?


So you think that would be less power than running the motor at reduced speed? I don't think so. They never say it is more efficient than a variable speed motor, because it's not.



> Can you be a little more descript?


I and others are trying to explain things to you. If you don't believe us, just do it and find out the hard way.



> Um... how about a switch?


How much current does that motor draw at zero RPM and full pack voltage? Like 2000 amps? That flimsy comm and brushes should take that, 3 or 4 times. Need a big switch also.




> Again, can you be more descript. I'm open to the idea that this is a failing idea, but other than "it's not what is normally done" I haven't really gotten a reason for failure.


Hey, it may not be instant failure, but some of us think it is a bad idea from several fronts. Like I said, be prepared for disappointment. Two basic things: Bad motor choice. Bad control choice.

Hey, I'm an engineer. My career has been giving advice to people who choose not to take it. So, I could care less. I'm trying to help you. Take or leave it.

Regards,

major


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## gmijackso (Sep 30, 2008)

major said:


> So you think that would be less power than running the motor at reduced speed? I don't think so. They never say it is more efficient than a variable speed motor, because it's not.


perhaps, but the motor is most efficient when drawing 90-130A and turning 3100-3200 rpm. The motor also doesn't fall below 80% efficient until 220A at 3400rpm. However on the other end it falls below 80% efficient @ 50A and 2700rpm. Since the torque curve is pretty much linear, how could it possibly be more efficent to drag the motor throgh a range of 0-80% efficiency with every start and stop as opposed to running the motor consistantly above 80% efficiency?



major said:


> I and others are trying to explain things to you. If you don't believe us, just do it and find out the hard way.


It's not a matter of not believing, it's a matter of not really seeing any explaining. Maybe I'm over looking the explainations, feel free to point them out. All I am able to see at this point is "it won't work" without any explaination.



major said:


> How much current does that motor draw at zero RPM and full pack voltage? Like 2000 amps? That flimsy comm and brushes should take that, 3 or 4 times. Need a big switch also.


I see your point here, but wonder how this is significantly different from starting any industrial motor? Granted most are AC, but some are DC and don't necessarily have a gental startup procedure.



major said:


> Hey, it may not be instant failure, but some of us think it is a bad idea from several fronts. Like I said, be prepared for disappointment. Two basic things: Bad motor choice. Bad control choice.


Again, apparently I'm missing the fronts. I hear you saying bad motor choice, bad control choice, but I'm apparently overlooking the description pointing out why.



major said:


> Hey, I'm an engineer. My career has been giving advice to people who choose not to take it. So, I could care less. I'm trying to help you. Take or leave it.


Me too... Perhaps if your advice has some supporting description it would fall on fewer deaf ears. It's should be understandable that when people hear "don't do it" without any supporting info, that they're skeptical especially if those people are providing several examples as to why and how they think it should work. 

Like I said, perhaps I'm missing the detailed explaination, and if so, please point it out to me. I need to understand things completely before I can draw better opinions about them. Right now I have MY understanding. If my understanding is flawed (which it may be) I need to understand where and how. Telling me it's flawed without telling me where/how doesn't help.


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## major (Apr 4, 2008)

gmijackso said:


> Telling me it's flawed without telling me where/how doesn't help.


Sorry gmijackso,

I just don't have the time. Maybe some others here will chime in, some have, none I see are on your side. I suggest you seek out some other expert who is willing to spend the time with you. Or simply "do it". I'd love to see your results.

I just thought my opinion would be better than nothing.

major


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## gmijackso (Sep 30, 2008)

major said:


> I just thought my opinon would be better than nothing.


If you're not willing to support, how much weight can it possibly hold?

The world is flat, just ask me.


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## Bottomfeeder (Jun 13, 2008)

Hey, gmijackso!

It sounds like you're trying to figure out your design. Some people are telling you that it won't work. You don't think their explanation is adequate. You think it might work after all. Why don't you design your vehicle such that your motor/controller can be used, but leave room for a more traditional 6.7" motor? Then you can rub it in their faces as you drive around in your unique EV if it works, or you can replace the motor and controller for something more standard when it doesn't. You already have the motor and controller, so why not give it a shot? What's the worst thing you can do except waste a little time? I think people have given their opinions. They probably don't have STRONG evidence that it won't work. Just some experience and intuition. Doesn't innovation always go against those things?

Good luck!


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## frodus (Apr 12, 2008)

> Did you look at the links I provided at all? The LEM 200 is rated at 11hp continuous at 48V. It is rated at 20+Hp peak.


Stop right there. We're trying to help you AVOID failing. CHILL OUT.

I looked at it, but didn't have my KW to HP calculator handy.... First off, 6.1Hp is CONTIUOUS not PEAK for his motor. Its got over 15hp at 36V and 400A. If you want to argue more, why don't you go find out what the HP rating is, at 48V 400A, and compare that to 48V and 400A on the Lynch motor. Otherwise, its apples and oranges.
http://www.golfcarcatalog.com/catalog/index.cfm?fuseaction=product&theParentId=965&id=4298
(this d392 is a replacement for the d3080)

Its still only 25ftlbs. You're gonna take a LONG time to accelerate, or you're accelerate quick but have a top speed of about 10mph.



> The motor is vented as the pictures at the site show, and as I recall has a "fan" on the back end of the motor I'll have to take a closer look, but even if I have to force air cool it no big deal. It says very clearly on the motor that it is 11Hp continuous.


11hp isn't that much. How heavy is the vehicle? Find out if its got a fan. Even if it doesn't, it CAN overheat moreso than the series wound. They have more mass and thermal area to cool.



> I agree it is not a transmission, and I didn't claim to be trying to use it as one. I suggested that I would possibly try to use it as a speed controller. I understand that there will need to be some gear reduction to modify the rpm/torque range to the final drive. I'm still not hearing why it won't work as the speed controller I suggested?


Because you're adding inefficiency to the motor driveline. Your loss for 0-100% is from 100-0% loss. Plus, you LOSE torque when you need it. If you have it, well, thats just fine, use it. You'll be disapointed. Get an electronic speed control, they're MADE to control the speed of motors. Those clutches aren't made to control speed with higher torque applications. 



> So the motor is turning "zero" load at max rpm drawing 5 amps. As I begin to increase load, the rpms will drop some with the load, and the current is going to increse thus creating more torque. At some point the amount of torque created beats out your static friction and you begin to move. What am I missing?


Yup. What you're missing is, the torque max on this motor is 23.5 ftlbs max. If you think you can get that to move your vehicle + rider, then go for it.



> That may be the case, but at this point I can't prove or disprove his claims. He is apparently attempting to sell this as a modification to just about any golf cart, so I suspect that there would have to me at least some truth to his claims.


That's marketing for you  Don't have to prove it, just sell it.



> Most people I find here with real world data are doing MUCH heavier builds, or motorcycles that are lighter.


True, but if you're heavier than a motorcycle and want to use that motor, you'll be sorely dissapointed.

Go do some calculations. What torque do you need to move xxxlbs of vehicle + xxxlbs of rider at a decent rate? What HP do you need to get to 50mph and stay there? We're basing our arguements on our experiences, as well as calculations we've already done. You have list of parts and asked if it'l work.

Don't like our answer? Feel free to disprove us.


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## major (Apr 4, 2008)

gmijackso said:


> The world is flat, just ask me.


O.K.

How many of those motors are actually in use for EV propulsion? How many have you seen reports of failing? I've been around this game a long time, and that motor sucks as to durability. Even guys using them on 2 wheelers fry them. A few get by. But that is about it.

And the mag clutch thing. How is that different than a friction clutch? Or eddy current clutch? At best, torque out is equal to torque in. So any difference in output speed to input speed represents a difference in power that is wasted. Even a torque converter would be preferable.

You come to an EV forum seeking advice. Some of us try to help you. And you get pissed off because we don't give you a first class education. Sorry we (or I) don't meet your standards.

Just do and find out.

major


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## frodus (Apr 12, 2008)

> Then you saw less power being drawn by the motor using the magnadrive than by restricting output flow of the pump. How is using less power a waste of power?


well, its not... but losing torque in the process is going to make moving the vehicle really hard.




> Again, can you be more descript. I'm open to the idea that this is a failing idea, but other than "it's not what is normally done" I haven't really gotten a reason for failure.


I gave you several reasons


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## frodus (Apr 12, 2008)

> perhaps, but the motor is most efficient when drawing 90-130A and turning 3100-3200 rpm. The motor also doesn't fall below 80% efficient until 220A at 3400rpm. However on the other end it falls below 80% efficient @ 50A and 2700rpm. Since the torque curve is pretty much linear, how could it possibly be more efficent to drag the motor throgh a range of 0-80% efficiency with every start and stop as opposed to running the motor consistantly above 80% efficiency?


So, 5A at 48V is 240W, every time you're stopped. Once you increase the load, it starts to draw more current, voltage drops and your power shoots up to 8kw (straight from your datasheet). So, you'll ALWAYS be running between 240W and 8Kw. With a controller in the mix, you can limit current, so you can limit your output power and stop it from ever GETTING to that 8kw, even if its fully loaded, the controller controls the amps going to the motor. At a stop, it draws 0W, and you could program it to only go to 6kw. If you use the clutch, at the VERY least, your loss is 240W, then what is the efficiency of the clutch input to output? It slips. Unless its totally locked (100%) there will be a loss in efficiency. so if you're 0 < kw < 8kw you're losing lots of energy in the slipping of the "clutch". Electronic controllers can be north of 95% eff. Good luck getting that mechanically.



> It's not a matter of not believing, it's a matter of not really seeing any explaining. Maybe I'm over looking the explainations, feel free to point them out. All I am able to see at this point is "it won't work" without any explaination.


Its not a matter of explaining, its a matter of telling you what you want to hear, otherwise you ignore it.





> I see your point here, but wonder how this is significantly different from starting any industrial motor? Granted most are AC, but some are DC and don't necessarily have a gental startup procedure.


Motors that use contactors are HORRIBLY inefficient. Have you been in industrial. Most DC applications use A CONTROLLER! Most AC applications use a VFD, and on larger motors with fixed RPM, they use something called a SOFT START drive. They don't just "flip a big switch". I worked at GE for 5 years, after that I've been in the industrial sector doing Automation. This is how they do it.





> Again, apparently I'm missing the fronts. I hear you saying bad motor choice, bad control choice, but I'm apparently overlooking the description pointing out why.


You'll have almost no torque at 0rpm on the other side of that clutch. That won't work because you need torque to overcome static friction. In order to get 100% torque, you have to load the motor, thus totally defeating the purpose of the clutch. The motor is also undersized for a lightweight vehicle between 500-1000lbs. 11hp isn't a ton at 48V, the motor he used is 15+ at 36V 400A.


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## gmijackso (Sep 30, 2008)

frodus said:


> First off, 6.1Hp is CONTIUOUS not PEAK for his motor. Its got over 15hp at 36V and 400A. If you want to argue more, why don't you go find out what the HP rating is, at 48V 400A, and compare that to 48V and 400A on the Lynch motor. Otherwise, its apples and oranges.
> http://www.golfcarcatalog.com/catalog/index.cfm?fuseaction=product&theParentId=965&id=4298
> (this d392 is a replacement for the d3080)


Ok, apparently I'm still missing something here. It seems as though you're saying that the Rixster somehow has more HP and more torque and is the reason it's a feasable project. The Rixster uses a continuous 6 hp motor produced running on a 36v pack. The Lynch motor is a continuous 11.5 hp motor that runs at 48v, and has a peak hp of over 20hp at the same 48v. I was never suggesting to use the Rixster motor at 48volts, and don't understand how 11.5hp at 48V with the lynch motor isn't as capable as the 6hp at 36V in the Rixster.



frodus said:


> Its still only 25ftlbs. You're gonna take a LONG time to accelerate, or you're accelerate quick but have a top speed of about 10mph.


I agree, but if somehow the Rixster is capable of doing this with a 6hp motor, it should be possible with an 11.5hp motor correct?



frodus said:


> How heavy is the vehicle?


Which vehicle? The Rixster has a dry weight of 250lbs (which was in the link I posted).



frodus said:


> Yup. What you're missing is, the torque max on this motor is 23.5 ftlbs max. If you think you can get that to move your vehicle + rider, then go for it.


The max torque is actually more like 37 ftlbs. I don't know if I can get the weight moving with that or not. But as I said earlier, if the Rixster is able to do it with less hp, then why would it not work with more hp?



frodus said:


> We're basing our arguements on our experiences, as well as calculations we've already done. You have list of parts and asked if it'l work. Don't like our answer? Feel free to disprove us.


That's a fine thing to base it on. But you have to agree it is akin to saying "because I said so".


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## gmijackso (Sep 30, 2008)

major said:


> At best, torque out is equal to torque in. So any difference in output speed to input speed represents a difference in power that is wasted. Even a torque converter would be preferable.


I don't see this. As the output speed is reduced, the magnets allow more slip. This in turn reduced the amount of load on the motor with allows the motor to maintain full speed with less current required. So less current at the constant voltage is a save in power. Less speed out means less power in. Is this now how you see the effect? It's like a variable current drive as opposed to a variable voltage drive.



major said:


> You come to an EV forum seeking advice. Some of us try to help you. And you get pissed off because we don't give you a first class education. Sorry we (or I) don't meet your standards.


I don't get pissed off at the opinions placed. I get annoyed at the lack of ANY explaination beyond "because I said so". I don't expect a "first class education" as you put it, but some explaination is key, and until the last few posts I was getting none.


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## gmijackso (Sep 30, 2008)

frodus said:


> Its not a matter of explaining, its a matter of telling you what you want to hear, otherwise you ignore it.


That is a very bold statement to make in what is maybe your second post that included any explaination. As I suggested before, if I was missing previous explaination point it out, which you didn't do.

Never was I ignoring anything, I was simply asking repeatidly for explaination and trying to clarify my understanding of things. 

I had read in other places on this forum that there are a lot of naysayers and a lot of lack of support unless doing things in the tride and true way and it is apparently real. I don't expect to be fully supported, I don't expect to be supported at all for that matter, but I do expect that my points be countered with valid points of your own.

The one thing I do ignore is the "because I said so" mentality. If there are actual reasons show them (which you've finially begun doing and thank you, I'll consider them closely).


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## frodus (Apr 12, 2008)

> Ok, apparently I'm still missing something here. It seems as though you're saying that the Rixster somehow has more HP and more torque and is the reason it's a feasable project. The Rixster uses a continuous 6 hp motor produced running on a 36v pack. The Lynch motor is a continuous 11.5 hp motor that runs at 48v, and has a peak hp of over 20hp at the same 48v. I was never suggesting to use the Rixster motor at 48volts, and don't understand how 11.5hp at 48V with the lynch motor isn't as capable as the 6hp at 36V in the Rixster.


the GE motor has 15hp at 36V and 400A, but what I can't find is the torque.... thats All i've been trying to say. HP is great, but if you don't have sh*t for torque, you ain't goin anywhere..... You need to be comparing your motor to his setup.... 15Hp at 36V 400A and at 46lbs, its about twice the torque you've got.

HP might match, current might match, but I know the ftlbs is going to be more than 23.5ftlbs. Series wound motors are usually torque = weight. Get a curve and disprove me if you want. This is going by other motors in the same category from D&D and ADC, and my background in automation.

I wasn't suggesting to use the rixster motor, but you have to get your units straight. 36V ratings and 48V ratings aren't comparable without a torque curve for the motor.





> I agree, but if somehow the Rixster is capable of doing this with a 6hp motor, it should be possible with an 11.5hp motor correct?


Sure, if you can put a transmission in with multiple gears so that you're Torque matches the rixster at 0rpm, and allows you to get to 50mph.





> Which vehicle? The Rixster has a dry weight of 250lbs (which was in the link I posted).


I was asking about your vehicle. You expect 250lbs With batteries? Chassi? motor? Motor = 25lbs, chassis 100-150 (good luck getting it lighter than a motorcycle), transmission another 40-50lbs, and since you can't afford lipo batteries, you go lead, and expect to install 5kwh at least (100wh/mile for small motorcycles, and aerodynamics), 50 miles, 5000Wh. Going by what I have (will be similar because they're all lead batteries), 28Ah batteries 12V, you'd need 15 batteries, at 25lbs a piece, you'd have 375lbs in just batteries. Switch to lead, and you'd have 1/3 that, or about 125lbs. So with lead, expect 600lbs, without lead, expect 450lbs. Without rider, controller, cables, contactors, lights etc.



> The max torque is actually more like 37 ftlbs. I don't know if I can get the weight moving with that or not. But as I said earlier, if the Rixster is able to do it with less hp, then why would it not work with more hp?


Its not HP, its torque, stop confusing the two. 



> That's a fine thing to base it on. But you have to agree it is akin to saying "because I said so".


So even if I find another website, or a book, its all just he said she said


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## frodus (Apr 12, 2008)

gmijackso said:


> The one thing I do ignore is the "because I said so" mentality. If there are actual reasons show them (which you've finially begun doing and thank you, I'll consider them closely).


Point taken, but I also didn't lock in and say things were true, I said its not Likely that you'd get to 50mph continuous, and that you'd likely have some torque constraints to consider, and that you might have heat dissipation issues.

Not because I said so, Just things to consider...

How about this, you go build it, and then come back and tell us what you did. Thats what we all did.

If you aren't doing something tried and true, we're going to give our opinions on what a working design would be with your constraints. We ALL think the motor is a little small for the job, and that the mechanical coupling is not ideal. Take that for what its worth and do your own research to see if its really the best solution for you (for both cost and complexity).


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## TX_Dj (Jul 25, 2008)

frodus said:


> Its not HP, its torque, stop confusing the two.


Exactly.

Torque is a measure of work, HP is a measure of work over time. You cannot calculate HP without torque and RPM.

In your original post you stated:



> Rated RPM: 2592
> Rated Voltage: 48V
> Rated Current: 215A
> Rated Torque: 31.5 Nm (23.23 ft. lbs.)


You would think, by the way this is written, that it's saying your torque is 23.23 ft lbs AT 2592 RPM. If that were the case, you'd be producing 47 HP. 47 HP = 35 kW. 35kW @ 48v = 729 Amps. Think again.

Torque is everything. Without torque, nothing moves. Horsepower only comes into play if you have sufficient torque and RPM. The bulk of electric motor torque is generated near 0 RPM. You want to use that to your advantage at all times, while still retaining the ability to spin the motor near its max RPM for efficiency.

As the RPM comes up, the volts come up. As volts come up, less amps are required to do the same work. Less amps = less heat. Less heat = longer motor life. On the flip side, if you're running your motor at max RPM and try to get moving from a stop, it doesn't matter what the HP is at that max RPM, torque is small.

You also say your rated power is 11.46 HP... at 2592 RPM... that's 5.6 ft-lbs.

Use the torque, Luke!


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## frodus (Apr 12, 2008)

TX_Dj said:


> Use the torque, Luke!


LMFAO

The [electro motive] force is strong with this one....

(sorry, just had to).


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## gmijackso (Sep 30, 2008)

TX_Dj said:


> You would think, by the way this is written, that it's saying your torque is 23.23 ft lbs AT 2592 RPM. If that were the case, you'd be producing 47 HP. 47 HP = 35 kW. 35kW @ 48v = 729 Amps. Think again.


I'm not sure I follow you here. Braking Torque (aka full load torque) given HP and RPM is as follows.

T=(5252xHP)/rpm
If we agree that the motor can produce 11.5HP @2592 rpm we can fill in the formula.
T=(5252x11.5)/2592
T=60398/2592
T=23.3 ft lbs

correct or no?


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## gmijackso (Sep 30, 2008)

frodus said:


> LMFAO
> 
> The [electro motive] force is strong with this one....
> 
> (sorry, just had to).


 
I have to say, I'm glad we've all lightened up a little.


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## TX_Dj (Jul 25, 2008)

gmijackso said:


> T=23.3 ft lbs
> 
> correct or no?


Argh, I must have been too quick on the calculator, I did 11.5 * 2592 / 5252... 

Sorry, I'm still at work, ground loop in the brain...


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## gmijackso (Sep 30, 2008)

TX_Dj said:


> Argh, I must have been too quick on the calculator, I did 11.5 * 2592 / 5252...
> 
> Sorry, I'm still at work, ground loop in the brain...


No worries. So that would indicate 23 ft lbs of torque at rated rpm correct? Everybody is right, HP isn't torque, but they are relational, and since I increase HP with rpm, I increase torque with rpm. So why wouldn't you want to always run the motor at max rpm and always have that torque available?

Now I understand that it may still not be enough torque but it's a start.


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## frodus (Apr 12, 2008)

Groundloops consistantly cause undesired results 

The motor is a nice motor, but I think there's going to be a design challenge keeping it under 500lbs, so it might be a little underpowered. You can always gear it for 40mph. You still have to get around 5000-5500Wh of batteries in there somehow for 50 miles.


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## gmijackso (Sep 30, 2008)

I do have a backup option of running dual Briggs & Stratton E-tek motors. This option is undesireable though becasue of added cost. I have the motors, but at very least would need to buy 2 new contollers for them.

Or I would need to combine their outputs to use the existing magnadrive option (that admittedly may not work either). I also have a Coyote Electonics item that works just like the magna drive except it uses variable electro-magent coupling rather than variable perminant magnet air gap. But I don't see a use for it at all at the moment.

All part of the same small lot deal


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## frodus (Apr 12, 2008)

gmijackso said:


> HP isn't torque, but they are relational, and since I increase HP with rpm, I increase torque with rpm. So why wouldn't you want to always run the motor at max rpm and always have that torque available?
> 
> Now I understand that it may still not be enough torque but it's a start.


Torque DECREASES with RPM, they're inversely proportional.

You don't want to run at max RPM because there's not as much torque at higher RPM.

The motor is actually better than I thought (thought it was the smaller LEM motor). Its Nm per A is .15 which would give ~44ftlbs of torque. At 300A mine gives about 45ftlbs, at 400 it gives around 60ftlbs. 

Just keep in mind the weight, and try to gear it so you can get up to speed fairly quickly, and use less current, but maybe have a lower top speed. This helps the batteries. They don't like to draw large amps, their Ah capacity decreases exponentially the more amps you draw (peukert effect)


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## gmijackso (Sep 30, 2008)

Ok... So lets pretend you have a motor that is capable of 100ft lbs at 0 rpms but moves to 0 ft lbls at 100 rpms (just for sake of easy numbers).

Now lets assume that it takes 50 ftlbs to break static friction and begin rolling.

If I start a motor with 0V at full load and apply voltage, I'm going to hit the load with 100 ft lbs of torque and begin moving as rpms increase.

If I start the motor with full voltage and no load and apply load, the motor will drag rpms down with the load until you reach say 50 rpms where you now are applying 50 ft lbs of torque, enough to brake friction and you begin to roll.

As far as rolling goes, is it not effectively the same thing? But as the motor looks at is, isn't it easier to ease into the load with more torque slowly instead of slapping it with full torque where some may not be needed?


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## frodus (Apr 12, 2008)

More current = More torque

More Voltage = More RPM (speed)

Those are factual relationships for DC motors, not something I pulled out of my bum.

Just because you ease into it doesn't matter... thats what a controller does. It PMW's starting at a low average voltage and high current. Then as PWM increases, the Average voltage increases and the current decreases, but the power is the same.

With yours, you load it and decrease RPM, while maintaining full pack voltage, which is going to cause amps to increase, but at full pack volrage which causes some VERY HIGH uncontrolled power (volts times amps). Sure it causes torque to increase, but 400A at 48V is 19,200W, just to acclerate from a stop. This stresses A) the batteries B) the motor C) all of the cables

If you did that controlled, with a series motor, you might be giving it 400A at 25% throttle (steadily increasing Average volts, but decreasing current), which would be ~12Vavg on a 48V pack, which is 4800W. This is MUCH easier on the batteries, controller and the motor. You still get all that torque, but at a lower average voltage, and lower average power. At Low RPM, you're not spinning the motor fast (yet) so you don't need that full pack voltage on it.

If you have a 90% efficient motor running the first way, thats 19,200*0.1, thats 1920Watts dissipated as electrical loss (heat). @100wh/mile, thats about 19 miles lost.

If you have a 90% efficient motor running the second way, thats 480W dissipated. Thats 5 miles lost.

Over an hour, which one gets more range? I'll give you a hint, its NOT the first way. Thats a huge difference.


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## major (Apr 4, 2008)

gmijackso said:


> I don't see this. As the output speed is reduced, the magnets allow more slip. This in turn reduced the amount of load on the motor with allows the motor to maintain full speed with less current required. So less current at the constant voltage is a save in power. Less speed out means less power in. Is this now how you see the effect?


No, I don't see it that way at all. The device increases the gap between magnets and conductor to allow slip which then causes a difference between input and output speed. As this gap increases to allow more slip for lower output speed, it also reduces the torque transfer.

Use the vehicle acceleration from standstill for an example. Let's say a 3000 RPM motor speed. 0 RPM driveshaft speed. You want to accelerate. Reduce the gap between the copper disc and magnets. The motor starts seeing torque. The current goes up. The motor speed decreases slightly. Driveshaft torque is a small fraction of motor torque. The car is still sitting there at 0 mph. Reduce the gap further until the car starts to move. The motor is still turning at high RPM, let's say 2800. What limits the motor torque? The strength of the magnetic coupling. When is that coupling the strongest? When the gap is the smallest. So, to get going in a reasonable fashion, close the gap to a minimum.

Now, you have maximum torque on both sides of the mag clutch. Maximum torque on the motor. Maximum to the wheels. But you have barely started to move. Call it zero plus mph. The motor is turning at 2500 RPM at maximum torque, say 46 lb.ft. So the motor output is 22 hp. Yet the vehicle isn't moving yet, so consuming no power. That mag clutch is zero percent efficient. 22 hp in, zero hp out.

As the vehicle starts to move faster and faster, the mag clutch stays at the same torque and its output speeds up, becoming more and more efficient until the magnet and copper disc find an equilibrium. If the system is geared correctly, that will occur when the slip is 1 to 4 percent (per the web site). Now you have maximum vehicle speed and maximum power. And an efficient power conversion consisting of the motor efficiency and 96 to 99 percent for the clutch. Not bad. But what did you lose to get there? I think it would be one half of the total energy output from the motor shaft. Like 60 percent of the energy from the battery was lost to heat for that acceleration. Most of it in the clutch.

Now you're cruising at maximum mph and maximum power. But you need to slow down to 50 percent speed for a few miles. Pull the clutch apart. Increase the gap. Driveshaft slows down. Driveshaft torque decreases relative to motor torque. And the vehicle travels at half speed.

What happened to the motor? Good bet it is somewhere between 3000 and 2500 RPM. What about the motor torque? Could not possibly be less than the drive shaft torque. You increased the magnetic gap, so good bet motor torque is greater than driveshaft torque. They don't give any info on this. But let's just say motor torque is equal to driveshaft torque. 

So for half maximum speed, driveshaft needs 1250 RPM. Motor is turning at 2600(?). We assumed equal torque in and out of the clutch, so it is about 50 percent efficient. If full speed required 22 hp, half speed is, let's say 8 hp, at the driveshaft. So the motor has to put out 16 hp.

Compare that to a variable speed motor (with controller) where the motor output is 8 hp at 1250 RPM. You traded a 98% electronic speed control for a 50% efficient clutch.

The mag clutch claim of saving power is like comparing the above example to slowing the vehicle to half speed by applying the friction brakes and leaving the power plant at maximum output. So they would use 16 hp instead of 22 hp, saving 6 hp.

That's how I see it.

major

ps. Just occurred to me while at lunch. Input and output torque have to be equal.


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## gmijackso (Sep 30, 2008)

Thanks Frodus and Major. The failure state of my Mangadrive is becoming more obvious to me now. 

On a completely different front, I bought a few much smaller trinkets today for the project.
Got a pair of 600A shunts (50mV)
200A (50mv) meter... I can multiply by 3 til I get around to making a new scale.
2 DC-DC Converters, I dunno what all I'll use them for, but they were less than $6 each and provide [email protected], [email protected], 3.3/2.9V @3A (i think they were originally for some PC application) with a 40-65VDC input (my 48 fits nicely between those).
Those are the coolest/most important things at the moment. Can't really do any real testing until I can determine how much current I have running around.

If it makes you guys feel any better/happier, I also got a few parts (including perf board) that will be required if/when I need to build a pwm conroller (if I haven't said it before, I will now, I'm cheap). Also a few parts to build a charger for the batteries I don't yet have. 

I do things in a strange order... But, if I can keep acquiring things at the "deal ratio" I have been, this could possibly be the cheapest build ever. Any records on that? How sucessful does it have to be in the end to qualify as a build? lol


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## kek_63 (Apr 20, 2008)

gmijackso said:


> I do things in a strange order... But, if I can keep acquiring things at the "deal ratio" I have been, this could possibly be the cheapest build ever. Any records on that? How sucessful does it have to be in the end to qualify as a build? lol


So far I've got $25 invested in my chopper - total! It is complete but not yet legal. Does that still count for cheapest?

Later,
Keith


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## jaspersk (Jun 26, 2008)

I have not personally installed any MagnaDrives but I know my company has considered them for existing installations for high hp applications where it is difficult to install a VFD (medium voltage as one example).

While I know very little about the installations, I do seem to remember having some discussions about efficiency and the requirement for cooling. I believe this drive is fairly efficient when there is minimal slip between the motor and the load being driven. It works well for a soft start from that standpoint. However, as the slip increases, the losses increase. That makes an EV a very bad application for a magnetic coupler. Major and Frodus have already pointed this out, but the biggest disadvantage will be on range. Take a look at the power consumption graphs in the following report:

http://www1.eere.energy.gov/femp/pdfs/mag_motors.pdf

You will use twice as much power at 50% motor speed and it gets worse as you go down in speed from there. Personally, I'd try to sell your stuff and use it to buy something proven. But I really admire your willingness to investigate something new. I haven't been brave enough to try something unique on my EV and have chosen to follow the road traveled by the folks before me.


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## major (Apr 4, 2008)

jaspersk said:


> Take a look at the power consumption graphs in the following report:
> 
> http://www1.eere.energy.gov/femp/pdfs/mag_motors.pdf
> 
> You will use twice as much power at 50% motor speed and it gets worse as you go down in speed from there.


jaspersk,

Where were you yesterday? Could have saved me a lot of time explaining the obvious to that guy. Thanks for the report.

major


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## gmijackso (Sep 30, 2008)

I eventually found that report as well. I also found something on a thread (I think here) that the magnadrive was in use by General Dynamics for a vehicle sold to Canadian armed forces. I know a guy that works for GD and asked him if he knew anything about it but havn't heard back yet.

It looks like the Magnadrive isn't likely to work, though out of pure curiosity for real world data, I'd like to hook it all up one time and load it down and take some current measurements. Gives me something to do while waiting for more money/parts anyway.


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