Motors - state of the community

[ttshaw1]

I'm planning a e-motorcycle build based on a Honda Grom frame. What I'd like to do is approximate the performance of a CSC City Slicker, meaning roughly a 5kW motor. I also want to keep my options open if I decide to upgrade the motor to something like 15kW or perhaps 25kW - so the motor voltage and control scheme should be compatible with reasonably available and cheap higher power motors.

Right now, the best option I've found is 72V BLDC motors, which are fairly simple to find around 5kW. Golden Motor also offers 10 and 20kW BLDC motors compatible with 72V, so the upgrade potential is there. What I'm wondering is if there's an outstanding consensus among hobbyists about companies, motor types (e.g. am I sleeping on AC?), voltages, etc. to prefer or avoid that would contraindicate or support my plan. I haven't been on this forum or others long enough to know, so I'd appreciate it if someone could clue me in as to the general sentiments of the community.

Thanks!

 

[mxlemming]

My opinion from what I've read... For low hassle high performance for a mini motorbike conversion

Nucular 12 or 24f, get on the waiting list ASAP and get some relatively cheap interim controller

Qs120 or 138

20s battery (72V nominal, 84 at full charge).

Avoid the path I follow with custom controllers and misused RC motors with unrealistic ratings.

The Golden and QS motors mentioned can be run far above their ratings.

 

[dozentrio]

I am also trying to get a handle on this.

I am doing an electric conversion on a 1980 Yamaha SR250. My wish is to be able to cruise at 140 kph. Seems the stock bike has an effective top speed around 110 kph and has about 13 kW available at the crank. I will need more power to get my 140 kph goal.

The Motenergy specs (https://www.electricmotorsport.com...tor-24-120v-5000rpm-12-kw-cont-30-kw-pk.html)claim 180 amps continuous. Perhaps I can run it at 120 volts and get something like 20 kW continuous.

There are also Golden Motor and 75-7 zero motors available. Not sure what my best option is. I also have two of these large drone motors laying around. Could make a custom shaft, join them, and have something capable of ~40kW continuous.
https://www.freerchobby.cc/products/mp20280-45kw-95kg-thrust-brushless-motor-for-home-build-flying-car

 

[larsb]

Haven’t seen much positive on the golden motors here. A qs138 90h would tick your boxes. Paired with xxx controller. Votols seems like too screwed up in the program now.

People seem to have issues with the new fardriver controllers but that is still what i’d get. So far could be just that it’s unknown and poor support as always

 

[Chalo]

I am doing an electric conversion on a 1980 Yamaha SR250. My wish is to be able to cruise at 140 kph.

Emptying your battery pack in a few minutes isn't "cruising". My back of the envelope estimate suggests you'll need about 30 kW at the wheel to hold 87 mph.

 

[dozentrio]

I am doing an electric conversion on a 1980 Yamaha SR250. My wish is to be able to cruise at 140 kph.

Emptying your battery pack in a few minutes isn't "cruising". My back of the envelope estimate suggests you'll need about 30 kW at the wheel to hold 87 mph.

It definitely won't be efficient at that speed. I will need to cram as much battery as I can in it. As far as power required to go 87 mph, how did you get your number? My only point of reference is that a '09 ninja 250 is measured on a dyno to have 19.5 kw at the wheels and has a top speed of around 108 mph. I know it's a slightly different bike, but that's a fairly generous margin in terms of power and speed. Say we do a 10% drive train loss, and a 10% electrical->mechanical power loss, that still only requires 23.5 electrical kW to do 108 mph. I've been trying to find more data points on this so if I'm way off base please let me know.

 

[Chalo]

As far as power required to go 87 mph, how did you get your number?

http://www.kreuzotter.de/english/espeed.htm

For a motorcycle, I use the "roadster" setting because motorcycle. I used 550 lbs rider + bike weight because it presumes lots of battery, and plenty of rider. Set the elevation to 500 feet to reflect where most of us live. Set the pedal cadence to 1 so leg thrashing doesn't cost efficiency.

 

[BalorNG]

I am doing an electric conversion on a 1980 Yamaha SR250. My wish is to be able to cruise at 140 kph.

Emptying your battery pack in a few minutes isn't "cruising". My back of the envelope estimate suggests you'll need about 30 kW at the wheel to hold 87 mph.

At very high speed, and lacking massive energy density of fossil fuels (tank), only way to *cruise* at very high speeds w/o towing a Tesla-sized battery pack is streamlined shell, and we have an entire thread dedicated to that in ebike section

 

[Jordan325ic]

I'm planning a e-motorcycle build based on a Honda Grom frame. What I'd like to do is approximate the performance of a CSC City Slicker, meaning roughly a 5kW motor. I also want to keep my options open if I decide to upgrade the motor to something like 15kW or perhaps 25kW - so the motor voltage and control scheme should be compatible with reasonably available and cheap higher power motors.

Right now, the best option I've found is 72V BLDC motors, which are fairly simple to find around 5kW. Golden Motor also offers 10 and 20kW BLDC motors compatible with 72V, so the upgrade potential is there. What I'm wondering is if there's an outstanding consensus among hobbyists about companies, motor types (e.g. am I sleeping on AC?), voltages, etc. to prefer or avoid that would contraindicate or support my plan. I haven't been on this forum or others long enough to know, so I'd appreciate it if someone could clue me in as to the general sentiments of the community.

Thanks!

The QS138 sounds like the motor for you. It's a mid mount motor technically rated at 3000W but is known to be reliable at much higher power levels. The V3 has an integrated gearbox which removes the need for crazy custom rear sprockets. And it's pretty affordable.

 

[dozentrio]

I am doing an electric conversion on a 1980 Yamaha SR250. My wish is to be able to cruise at 140 kph.

Emptying your battery pack in a few minutes isn't "cruising". My back of the envelope estimate suggests you'll need about 30 kW at the wheel to hold 87 mph.

At very high speed, and lacking massive energy density of fossil fuels (tank), only way to *cruise* at very high speeds w/o towing a Tesla-sized battery pack is streamlined shell, and we have an entire thread dedicated to that in ebike section

Thanks, I'll check for this!
So far what I've found from google searches regarding motorcycle fairings is a bit discouraging. I found a few examples of fully enclosed "bikes" or dustbins but 1) I don't love the styling and 2) it looks challenging to do. I was thinking of trying "winglets" as vortex generators to disrupt flow around the rider so that a full fairing isn't needed. Will check to see what folks on ES have come up with!

 

[BalorNG]

I am doing an electric conversion on a 1980 Yamaha SR250. My wish is to be able to cruise at 140 kph.

Emptying your battery pack in a few minutes isn't "cruising". My back of the envelope estimate suggests you'll need about 30 kW at the wheel to hold 87 mph.

At very high speed, and lacking massive energy density of fossil fuels (tank), only way to *cruise* at very high speeds w/o towing a Tesla-sized battery pack is streamlined shell, and we have an entire thread dedicated to that in ebike section

Thanks, I'll check for this!
So far what I've found from google searches regarding motorcycle fairings is a bit discouraging. I found a few examples of fully enclosed "bikes" or dustbins but 1) I don't love the styling and 2) it looks challenging to do. I was thinking of trying "winglets" as vortex generators to disrupt flow around the rider so that a full fairing isn't needed. Will check to see what folks on ES have come up with!

And a good thing you are 'a bit discouraged', because motorcycle fairings that are really effective ARE complex to pull off, and it comes not to making them fast, but making them SAFE:
https://motochassis.com/Articles/Aerodynamics/AERO.htm

And no, 'vortex generators/winglets' will not work, lol. You misunderstand what purpose do they serve (it require knowledge of laminar-turbulent transition, boundary layers and their detachment and Reynolds number - no need to dig into differential equations, just understanding what they truly stand for will do). Having air not turbulent enough is certainly not a problem on a motorcycle
Ok, a lift dumper might be a good idea and it was used to good effects AFAIK, but that's also a different concept...

If you want a high-speed, but a very effective drag-wise vehicle, it should be made 'from ground up' around this concept, or at least have fairing designed by someone who truly knows what he is doing - and this not something you learn by googling for 10 minuts and watching a couple of youtube videos.

http://craigvetter.com/pages/Online_Store/Streamliner%20Superstore.html
This one might work, but how well will depend on what kind motorcycle you have, you want a VERY stable one, up to and including sacrificing manueverability.

 

[dozentrio]

Emptying your battery pack in a few minutes isn't "cruising". My back of the envelope estimate suggests you'll need about 30 kW at the wheel to hold 87 mph.

At very high speed, and lacking massive energy density of fossil fuels (tank), only way to *cruise* at very high speeds w/o towing a Tesla-sized battery pack is streamlined shell, and we have an entire thread dedicated to that in ebike section

Thanks, I'll check for this!
So far what I've found from google searches regarding motorcycle fairings is a bit discouraging. I found a few examples of fully enclosed "bikes" or dustbins but 1) I don't love the styling and 2) it looks challenging to do. I was thinking of trying "winglets" as vortex generators to disrupt flow around the rider so that a full fairing isn't needed. Will check to see what folks on ES have come up with!

And a good thing you are 'a bit discouraged', because motorcycle fairings that are really effective ARE complex to pull off, and it comes not to making them fast, but making them SAFE:
https://motochassis.com/Articles/Aerodynamics/AERO.htm

And no, 'vortex generators/winglets' will not work, lol. You misunderstand what purpose do they serve (it require knowledge of laminar-turbulent transition, boundary layers and their detachment and Reynolds number - no need to dig into differential equations, just understanding what they truly stand for will do). Having air not turbulent enough is certainly not a problem on a motorcycle
Ok, a lift dumper might be a good idea and it was used to good effects AFAIK, but that's also a different concept...

If you want a high-speed, but a very effective drag-wise vehicle, it should be made 'from ground up' around this concept, or at least have fairing designed by someone who truly knows what he is doing - and this not something you learn by googling for 10 minuts and watching a couple of youtube videos.

http://craigvetter.com/pages/Online_Store/Streamliner%20Superstore.html
This one might work, but how well will depend on what kind motorcycle you have, you want a VERY stable one, up to and including sacrificing manueverability.

I do question the value of traditional university teaching in comparison to what one can learn from youtube. Why labour through an explanation when millions of people have already voted on the best and most clearly presented explanation? 3blue1brown is certainly easier to follow than my Linear Algebra class was when I took it, and I think my own students only tolerate my ramblings because I grade their reports

 

[BalorNG]

At very high speed, and lacking massive energy density of fossil fuels (tank), only way to *cruise* at very high speeds w/o towing a Tesla-sized battery pack is streamlined shell, and we have an entire thread dedicated to that in ebike section

Thanks, I'll check for this!
So far what I've found from google searches regarding motorcycle fairings is a bit discouraging. I found a few examples of fully enclosed "bikes" or dustbins but 1) I don't love the styling and 2) it looks challenging to do. I was thinking of trying "winglets" as vortex generators to disrupt flow around the rider so that a full fairing isn't needed. Will check to see what folks on ES have come up with!

And a good thing you are 'a bit discouraged', because motorcycle fairings that are really effective ARE complex to pull off, and it comes not to making them fast, but making them SAFE:
https://motochassis.com/Articles/Aerodynamics/AERO.htm

And no, 'vortex generators/winglets' will not work, lol. You misunderstand what purpose do they serve (it require knowledge of laminar-turbulent transition, boundary layers and their detachment and Reynolds number - no need to dig into differential equations, just understanding what they truly stand for will do). Having air not turbulent enough is certainly not a problem on a motorcycle
Ok, a lift dumper might be a good idea and it was used to good effects AFAIK, but that's also a different concept...

If you want a high-speed, but a very effective drag-wise vehicle, it should be made 'from ground up' around this concept, or at least have fairing designed by someone who truly knows what he is doing - and this not something you learn by googling for 10 minuts and watching a couple of youtube videos.

http://craigvetter.com/pages/Online_Store/Streamliner%20Superstore.html
This one might work, but how well will depend on what kind motorcycle you have, you want a VERY stable one, up to and including sacrificing manueverability.

I do question the value of traditional university teaching in comparison to what one can learn from youtube. Why labour through an explanation when millions of people have already voted on the best and most clearly presented explanation? 3blue1brown is certainly easier to follow than my Linear Algebra class was when I took it, and I think my own students only tolerate my ramblings because I grade their reports

Well, there IS a wealth of information on youtube - including free access to lectures from elite universities you are not likely to ever afford otherwise, but still - that's many hours of mindful watching

Getting a general idea is easy, but designing something that is both fast, practical and safe does not seem to be - the fact that fully faired bikes are rarer than unicorns seems like a dead giveaway. It is possible, and people even been touring on them - but it seems that most successful ones take the shape of a long-wheelbase, low recumbent bike.

 

[Barncat]

re an OP post above: right... the only way a Ninja 250 will do 108mph is to drop it from an airplane.

my Ducati 750ss with some 70hp will cruise a US interstate at 85 but that's only pleasant with a tailwind, and you're risking a big ticket. i'll occasionally peg the throttle and "do the ton" on backroads, but then you're in license-losing territory, so that's rare.

anyway, as the other guys are pointing out, going fast is either about extreme streamlining, or crotch rocket power- streamlining being inversely proportional to practicality. also, i wouldn't be basing a high speed ride on a Grom. my two cents. plus it's expensive to cross the boundary from fun eToy to highway capable performance...