Hello EV Bikers, and happy new 2022 
I am new to the forum so please excuse me if I chose the wrong area for the topic. I am designing an Aprilia Pegaso (1997 to 2000 model) EV conversion. This would be my first EV conversion. I have automotive engineering background but I'm not an EV specialist. I read a few books on the subject in order to get some sort of clear design in mind and avoid reengineering things or reordering parts mid-project, which would be a waste of time and money. Here's what I have in mind : Get a 650 Pegaso (something I know) with good enough plastics, suspension,frame and no rust, tear most of it down, stick an electric motor instead and fill in the gaps with as much lithium cylindrical cells as I can (air box under the seat, inside the mufflers..) while keeping the weight close to stock and the center of gravity as low as possible. I'm aiming for a riding experience not too far from stock (37 Kw/60 Nm). Here are the design choices that I am struggling with :
1) Motor type to choose :
It will be either DC brushless or AC induction. I don't have a full understanding of how either of them will behave but here's what I have found so far :
Price : The AC motor is generally cheaper (no magnets) but the controller is more complicated, and therefore more expensive -> AC vs DC motor/controller combinations would be close enough. So price is not going to be a main deciding factor.
Controllability/behavior : DC has more torque off the line and more peak efficiency, but AC can be better for a performance application, if coupled with the right controller/software. AC can also have a better overall efficiency (https://www.tesla.com/blog/induction-versus-dc-brushless-motors). I would prefer to keep the power and torque curve profiles similar to an ICE : Something like a big KTM V-twin profile with peak figures close to stock (37 Kw/60 Nm). I wouldn't mind getting a little more torque since it is electric, but I want smooth acceleration and predictability around corners, again, not a completely different experience from an ICE. A high revving motor would be preferred, let's say 5000 rpm at least. You get the picture, it's a motorcycle trying to be electric, not an electric vehicle trying to be a motorcycle.
Braking regeneration : Apparently AC induction is easier to operate in generator mode and I could get more regeneration in lower speeds with it, apparently!
I am leaning towards AC according to what I read so far, but it's not yet backed by equations and figures or any type of experience.
2) Keep the gearbox or get rid of it :
This is a tricky one.. Here's how I see it : Transmittions increase the dynamic usability, and therefore efficiency, of any motor/engine, that said, ICE can't run without them, but electric motors can operate on a much wider range, and here it gets almost subjective. Big companies have to go about this with different constraints in mind, supply, cost... Tesla and zero went without one, Porsche and Brammo went with one, all for different but understandable reasons. In my case, the whole transmission is already there, if it gives me a 10% efficiency overall I'm up for using it, plus, engine braking is fun (assuming it won't be a huge headache to calibrate the controller for it). From what I saw, 5 gears are not really necessary with any electric powertrain, so I'm thinking maybe it would make sense to use first, third and fifth. I'm leaning towards keeping the gears and getting a smaller motor/controller set up for a better efficiency and less cost. I saw online someone who cut off the upper half of an engine and stuck an electric motor to the timing chain, not a bad idea ! Obviously in my case I would probably have to reinforce the timing sprocket and go with a bigger chain, it would need some work, but if the result is worth it in terms of efficiency and riding fun, definitely doable. Internet says chain drive efficiency is 98%, with two chains in the setup I'd be around 96%, right at where the best designed belts are.
One more thing, the plan is to use the bike as it was intended stock, so commuting, highway speeds and light off-roading. So a 150 km/h (93 Mph) top speed would be nice, maximum range is a priority, while keeping the weight from messing with the handling. There are no plans to touch the suspension, except adjustments within stock parameters.
So, what do you guys think ? Did I get something wrong ? Is it too ambitious ? what range can I hope for here ? Did any of you consider keeping the gearbox on a conversion ? What were your reasons either way ?
Did anyone have experience setting up an electric power-train ? AC induction or Brushless DC for what I'm aiming for ? Any open source tools I can use for the controller Hardware/Software set up and calibration ?
Any readings/ressources you can recommend moving forward ?
Thanks for taking the time to read through all of it !! And ride safe !
I am new to the forum so please excuse me if I chose the wrong area for the topic. I am designing an Aprilia Pegaso (1997 to 2000 model) EV conversion. This would be my first EV conversion. I have automotive engineering background but I'm not an EV specialist. I read a few books on the subject in order to get some sort of clear design in mind and avoid reengineering things or reordering parts mid-project, which would be a waste of time and money. Here's what I have in mind : Get a 650 Pegaso (something I know) with good enough plastics, suspension,frame and no rust, tear most of it down, stick an electric motor instead and fill in the gaps with as much lithium cylindrical cells as I can (air box under the seat, inside the mufflers..) while keeping the weight close to stock and the center of gravity as low as possible. I'm aiming for a riding experience not too far from stock (37 Kw/60 Nm). Here are the design choices that I am struggling with :
1) Motor type to choose :
It will be either DC brushless or AC induction. I don't have a full understanding of how either of them will behave but here's what I have found so far :
Price : The AC motor is generally cheaper (no magnets) but the controller is more complicated, and therefore more expensive -> AC vs DC motor/controller combinations would be close enough. So price is not going to be a main deciding factor.
Controllability/behavior : DC has more torque off the line and more peak efficiency, but AC can be better for a performance application, if coupled with the right controller/software. AC can also have a better overall efficiency (https://www.tesla.com/blog/induction-versus-dc-brushless-motors). I would prefer to keep the power and torque curve profiles similar to an ICE : Something like a big KTM V-twin profile with peak figures close to stock (37 Kw/60 Nm). I wouldn't mind getting a little more torque since it is electric, but I want smooth acceleration and predictability around corners, again, not a completely different experience from an ICE. A high revving motor would be preferred, let's say 5000 rpm at least. You get the picture, it's a motorcycle trying to be electric, not an electric vehicle trying to be a motorcycle.
Braking regeneration : Apparently AC induction is easier to operate in generator mode and I could get more regeneration in lower speeds with it, apparently!
I am leaning towards AC according to what I read so far, but it's not yet backed by equations and figures or any type of experience.
2) Keep the gearbox or get rid of it :
This is a tricky one.. Here's how I see it : Transmittions increase the dynamic usability, and therefore efficiency, of any motor/engine, that said, ICE can't run without them, but electric motors can operate on a much wider range, and here it gets almost subjective. Big companies have to go about this with different constraints in mind, supply, cost... Tesla and zero went without one, Porsche and Brammo went with one, all for different but understandable reasons. In my case, the whole transmission is already there, if it gives me a 10% efficiency overall I'm up for using it, plus, engine braking is fun (assuming it won't be a huge headache to calibrate the controller for it). From what I saw, 5 gears are not really necessary with any electric powertrain, so I'm thinking maybe it would make sense to use first, third and fifth. I'm leaning towards keeping the gears and getting a smaller motor/controller set up for a better efficiency and less cost. I saw online someone who cut off the upper half of an engine and stuck an electric motor to the timing chain, not a bad idea ! Obviously in my case I would probably have to reinforce the timing sprocket and go with a bigger chain, it would need some work, but if the result is worth it in terms of efficiency and riding fun, definitely doable. Internet says chain drive efficiency is 98%, with two chains in the setup I'd be around 96%, right at where the best designed belts are.
One more thing, the plan is to use the bike as it was intended stock, so commuting, highway speeds and light off-roading. So a 150 km/h (93 Mph) top speed would be nice, maximum range is a priority, while keeping the weight from messing with the handling. There are no plans to touch the suspension, except adjustments within stock parameters.
So, what do you guys think ? Did I get something wrong ? Is it too ambitious ? what range can I hope for here ? Did any of you consider keeping the gearbox on a conversion ? What were your reasons either way ?
Did anyone have experience setting up an electric power-train ? AC induction or Brushless DC for what I'm aiming for ? Any open source tools I can use for the controller Hardware/Software set up and calibration ?
Any readings/ressources you can recommend moving forward ?
Thanks for taking the time to read through all of it !! And ride safe
!
