# AC motor with 10,000+ RPM for a bike



## Technologic (Jul 20, 2008)

I'm going to be taking the plunge and converting a bike soon (dropping my 1 person car that gets like 35mpg, until I get married and/or the aptera is in other states).

I need to find an AC motor with regen braking capacity that can run on a fixed gear ratio tranny (speed doesn't matter just want to top out at 70mph ish safely)

I have a lot of room for lithium batteries and plan to go full show on them with a voltage in the 120+ area. As many as I can fit in the gas tank and extra engine room (probably about a 3-5kwh pack if I can get the frame I want).

I'd like the motor to have a controller I can purchase outright as I have no EE abilities to speak of.

Thanks for any help in advance mates


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## Little Rhody (Jun 17, 2008)

I'M not sure why you need 10K rpm. 70mph is plenty achievable with an rpm range of 3000, to 4500 rpm. 

LR


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## skullbearer (Jul 9, 2008)

I'm with Rhody on this, besides most off the shelf AC motors you can fit in a bike and aren't enough hp to push a small tank are going to run at 1800 rpm or less.

Now, if you're looking to do 100mph+ you can do a no-reduction setup with an 1800rpm motor. Or you can do a slight reduction, say 1.2:1 or something like that, to get a stronger acceleration up to maybe 80mph. That gives you a bit of acceleration leeway on the freeway with plenty of power.


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## Technologic (Jul 20, 2008)

skullbearer said:


> I'm with Rhody on this, besides most off the shelf AC motors you can fit in a bike and aren't enough hp to push a small tank are going to run at 1800 rpm or less.
> 
> Now, if you're looking to do 100mph+ you can do a no-reduction setup with an 1800rpm motor. Or you can do a slight reduction, say 1.2:1 or something like that, to get a stronger acceleration up to maybe 80mph. That gives you a bit of acceleration leeway on the freeway with plenty of power.


a 1800rpm motor seems too easy to overrun and break... brushed motors are a no as well as I don't usually like them (from other experiences).

If I can get by with less I'll try.... I was hoping for a high voltage high RPM setup to save battery losses.


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## Technologic (Jul 20, 2008)

5kW x 8000RPM 100L Frame - High Speed 3ph AC Motor for 400V 3 phase supply. Use with 5.5kW Variable Frequency Drives having encoder feedback and full closed loop flux vector set.
Use over a 1000:1 Speed Control range from 8RPM to 8000RPM, at full rating. 
Full Load Current - 11A at 400V.




I'm looking at this motor atm for the application... it is rather expensive (1400 USD) and I'm confident I can find the same type of motor for cheaper.
pretty sure this would haul on a bike... current battery pack idea is LiFePO4 with about a 5kwh reserve (if I can manage to fit it)

Wanting a 100mile range.


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## skullbearer (Jul 9, 2008)

Technologic said:


> 5kW x 8000RPM 100L Frame - High Speed 3ph AC Motor for 400V 3 phase supply. Use with 5.5kW Variable Frequency Drives having encoder feedback and full closed loop flux vector set.
> Use over a 1000:1 Speed Control range from 8RPM to 8000RPM, at full rating.
> Full Load Current - 11A at 400V.
> 
> ...


And how heavy is your bike? 5.5kw is not only 3hp btw, its about 7.7hp.

The average motorcycle (wind resistance and rolling resistance together) would only get up to about, what guys? Maybe 40mph on 3hp? If its really light that is, like a 125cc bike frame. 8hp would struggle to make 55 in a light bike too, that's really stripped down or a dirtbike.

A Ninja 250 makes about 38hp and has a top speed of about 110, but my 250 Honda Elite Scooter makes about two and a half times the torque but only like 29 hp or something (hard to find consistent power numbers on this, they are really easy to modify without part changes, and mine is slightly). Yeah, like an electric my scoot really SCOOTS off the line, and I've actually toasted a camaro (with someone who didn't know how to drive stick behind the wheel granted) up to about 30mph, but with that amount of power and a lighter package than the ninja 250, that 10hp limits me by power to 72mph. 70 now, due to the age of the motor.

That and she only wants to cruise at 66 or less.


Yes, the peak power of that motor will get you a good up there speed, but if you run it at peak power for long it will also get you a good hunk of melted slag.


Choose your motor carefully.


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## Technologic (Jul 20, 2008)

skullbearer said:


> And how heavy is your bike? 5.5kw is not only 3hp btw, its about 7.7hp.
> 
> The average motorcycle (wind resistance and rolling resistance together) would only get up to about, what guys? Maybe 40mph on 3hp? If its really light that is, like a 125cc bike frame. 8hp would struggle to make 55 in a light bike too, that's really stripped down or a dirtbike.
> 
> ...



There are a number of CARS that run off of 5kw motors (for instance the aptera) and it weighs about 4 times more than I hope to make this bike weigh. I don't know how the drag/resistances will effect it, but my guess is that it will be ok... most/all EV motorcycles run 3kw or less motors from what I can find.

 now I'm just confused hehe


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## zig06 (Aug 3, 2008)

skullbearer said:


> And how heavy is your bike? 5.5kw is not only 3hp btw, its about 7.7hp.
> 
> The average motorcycle (wind resistance and rolling resistance together) would only get up to about, what guys? Maybe 40mph on 3hp? If its really light that is, like a 125cc bike frame. 8hp would struggle to make 55 in a light bike too, that's really stripped down or a dirtbike.
> 
> ...


Ummm, nothing personal but your numbers just don't add up. Like, there's no way on this green earth that a Honda Elite Scooter could beat any car off the line. Yes, if you get the drop or just out right take off before they do then great. But in a race just about any car will beat that scooter (including a fat guy in a Yugo).

Also, those power numbers sound like at the crank numbers not rear wheel HP which more directly applies to what we are doing. A number of years ago (about '95) Ford said that the aero load on a Thunderbird at 55mph was equal to 5hp. And a car is far more aerodynamic than any production bike, so it's easy to see that aero is huge.

Weight by itself doesn't have as big as an effect on top speed as you may think. Many land speed runs were made in vehicles that are very heavy. So weight by itself really only effects acceleration, aero load and vehicle drag are what effects top speed. 

Give me another month and I'll prove it.


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## frodus (Apr 12, 2008)

First off, 70mph and 100 miles range.... is a tall order. Lets say you can get the rolling resistance low enough and efficiency high enough to get 100Wh/mile (lowball for electric motorcycles, lots of them run around 100-125). So you want 100 miles, thats a 10,000Wh pack. Have fun fitting that in a motorcycle. at 120V you stated, thats going to need at least 90-100Ah lithium cells. Roughly 35 of them. Lets say you can get them for 150 a piece, 7 grand for batteries, no charger and no balancing.


Now, onto the topic of the motor. Why on gods green earth do you THINK you need 10,000RPM? Just because the ICE engine goes that high, doesn't mean you need to rev that high. Electric motors have almost ALL of their torque at 0rpm and a fairly flat power curve. ICE's do not.

For example: I have an 18" rear wheel. (130/80/18 tires, 130 * 0.80) x 2 then divide by 25.4 mm per inch +18 = 26.19″ = diameter. Circumference of the tire is pi*d/12 (convert to feet) = 6.856ft. at 4000RPM, with a 60 tooth rear sprocket and a 11 front, the wheel will travel at 57.13 mph. thats 72V for me with a series motor.

Now, look at AC (which can go higher RPM but the field starts to saturate at higher RPM and torque is decreased), to go 70mph on my bike, with this ratio, i'd need about 5000 rpm. you do NOT need 10,000rpm... period. And you might find it hard to even RUN a motor at 10,000 RPM, if its even possible with the inverter.

70mph is completely doable with the AC system from electricmotorsport. Its about 2500-3500 for a kit for an AC system, plus lifepo will run you about $10,000. No contactor, DC-DC converter, balancers, charger, gauges, fuses, cable, sprockets, chain, various hardware. That AC motor kit runs at 84V.

The other issue with 120V and trying to use an off the shelf industrial, is that its 230V, and you'll need an inverter for it. They have them for cars, but not in applications for motorcycles. There are 120V motors, but they're single phase, and you won't want that. Basically, the system linked to on EMS is the only one I've found that'd be of good use for a motorcycle. It'l give great performance, have a good top speed, and allow you lots of flexibility.

If I were you, I'd research a little more on what is feasable, 100mph and 70mph with an industrial motor shows you haven't looked online much to see what others have done. Its possible, but you'll have $12,000 into the bike without the roller, and likely have to get some luggage racks just to hold all the lifepo. you will also spend lots of time trying to source a motor and controller, if you even can find something.

www.evalbum.com is a great place to start.
http://www.evalbum.com/type/MTCY is all motorcycles


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## Technologic (Jul 20, 2008)

I've read quite a bit about it and came to the conclusion from lots of japanese/chinese bikes that it could be possible to make this for a reasonable price.

If it's seriously looking at a 12k price tag to get a bike to do this I'm gonna start looking again into dropping a custom low air resistance 1 piece body on a miata frame/suspension. 

a 70-100 mile range is something I'd like to get out of this at a reasonable price and since I've done lots of fiberglass work before I guess I should continue searching for a cheap motorless miata body.


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## frodus (Apr 12, 2008)

Technologic said:


> I've read quite a bit about it and came to the conclusion from lots of japanese/chinese bikes that it could be possible to make this for a reasonable price.
> 
> If it's seriously looking at a 12k price tag to get a bike to do this I'm gonna start looking again into dropping a custom low air resistance 1 piece body on a miata frame/suspension.
> 
> a 70-100 mile range is something I'd like to get out of this at a reasonable price and since I've done lots of fiberglass work before I guess I should continue searching for a cheap motorless miata body.


that 12k price tag is because your specifications aren't matching with your pocketbook. What is reasonable for one is not for the other.

Try scaling it back a bit. 50 miles is going to get you most places you need to go. 70 mph tops is fine, so consider 8-9 grand for a nice bike that'l be silent and go 50 miles. Just consider it this way.... you pay for distance with electric OR gas, but electric pays itself off.... gas doesn't.

motorless miata, thats fine, but you'll spend more getting that thing to run 100 miles than you EVER would in a motorcycle.


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## skullbearer (Jul 9, 2008)

I wish I could be fine with just 50mile range. My ride to school round trip is over 60 miles, closer to 70 or a little more. I don't really have a chance to recharge either...


I agree with you guys though, on this, I don't know why he thinks a 10k rpm motor is necessary, as I believe I mentioned earlier in the thread.

Ideally I think though you'd match your motor's peak efficiency rpm to your most common speed. For instance, for my personal commute to school I'd need a gear to optimize it at 55-60mph. This is really where I think mechanical gears will come into play with electric vehicles, especially bikes... if we want the absolute peak range we need a low speed gear (like 35mph max efficiency) a mid speed (45/50mph) and a high speed (55/60/65/70mph depending on your need).

Of course though these gears themselves reduce efficiency and the whole thing goes back to the drawing board...


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## TX_Dj (Jul 25, 2008)

IRT the discussion of small bikes with small power and top speeds-

The Honda Rebel 250 makes about 17 HP at around 9000 RPM, and about 12.5 ft-lbs around 7500 RPM. At the redline (about 9850 RPM) it will do 83 mph on flat level ground with a 180 lbs rider.

It has a curb weight of 230 lbs or so and will go about 130 miles on less than 2 gallons of gas. I put 13,000 miles on my last one, and averaged 68 mpg across all 13,000 miles. Riders who treat the bike gingerly and never exceed 55 mph average 80 mpg.

Total purchase price (new) - $3000.

If you run it on the HP curve (that is wind it out in each gear) you will accelerate faster than the traffic on the onramp ahead of you is willing to.

I took an 800 mile camping trip on mine, through hilly terrain, and had no problem maintaining the speed limits going up hills.

This will give you pause for thought when thinking about spending $10+k on an EV conversion that will have the same performance and range characteristics.


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## frodus (Apr 12, 2008)

TX_Dj said:


> This will give you pause for thought when thinking about spending $10+k on an EV conversion that will have the same performance and range characteristics.


I couldn't agree more. If someone wants an electric for going 5-10 miles to the store and back, an electric motorcycle is a winner.... but when you think about long range and low cost, they're mutually exclusive with an EV

If someone wants 75 miles and decent top speed for a low cost, consider getting a 250 or something. Sure, long term gas is more expensive, but replacing the pack in 5-6 years will also cost a ton as well. Cost of ownership is something that you need to consider.


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## skullbearer (Jul 9, 2008)

But you're going to be packing about a hundred grand in coolbucks! I'd eat the money for a good long range E-bike anyday. Anyday I had the money in the first place.


I'm running a Honda '87 CH250 'Elite' Maxiscooter right now, on my parent's dollar. Makes me feel real accomplished for a 22 year old getting married in a year. Not to mention my father wants me to have a 650 or larger so badly he's going to cough out the cash for a new one. We are considering converting the Honda into an EV, since parts are being phased out fairly rapidly in the last couple years. Otherwise it sells for over $2k which is more than twice what we paid for it + repairs, so it will also pay for most of the 650....


Anyway though, I think the big losses I experience in top speed with the 250 are that the motor is limited by a very small bore CV carb. I've been reading online about modifications to the bike, and one of them (filing down a ridiculously large weld bead in the header) is already done and adding a whole hp to the bike.

Even so, packing more hp than that Rebel and lighter too, the wind resistance is such and the motor efficiency rpm so low that the bike only winds out to 70mph as it is. Some gearbox changes can up that to nearly 85mph with no motor change but its shaky at 70mph, I don't think its sane at high speed.


Which brings me to a few considerations:

- Your starter bike had some known statistics, you can take advantage of those. If you can find power curves you can know what its producing at its top speed, since it is almost never max hp.

- Your starter bike has some known ranges and efficiencies, and you should be able to get a rough idea of how far your battery pack would take you. If you approximately match the original weight of the bike, and can produce the same amount of cruising power for a duration, just calculate your battery use at that power output and determine that duration, work that time with the speed, say 55mph, and you got your max range.

Ideally, like an ICE, you want to match your peak efficiency with your cruising range. I think I mentioned this before... possibly. I've been camping for the last week or so, so forgive any repeats.


:EDIT: By 'new one' on the 650 I mean a used one, 'new' for me.


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## Tommey Lee Reed (Sep 2, 2008)

Technologic said:


> I'm going to be taking the plunge and converting a bike soon (dropping my 1 person car that gets like 35mpg, until I get married and/or the aptera is in other states).
> 
> I need to find an AC motor with regen braking capacity that can run on a fixed gear ratio tranny (speed doesn't matter just want to top out at 70mph ish safely)
> 
> ...


Sounds good, but 5 kw won't get you 70+mph, maybe 40mph with a weight of 400 lb


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## frodus (Apr 12, 2008)

Tommy, he said 3-5kwh, as in total pack capacity in watt hours... not peak power.

just because he uses something like a 12V 50Ah battery doesn't mean its ONLY 600Wh, some batteries peak over 4C.... which might peak around 2400W.

My bike has a ~2500Wh pack.... and we've seen peaks of over 15kW on my 6.7" ADC motor. Got us to 65mph. I'm using 12 18Ah batteries for 72V (6 series 2 parallel). Each battery can source up to 200A peak, but 80A max continuous. Sure, they sag and don't last long, but I CAN achieve much more than 10kW with a 2500Wh pack.


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