I am planning something similar but I will use my existing 48v battery and baserunner. So far the difficult part is finding a motor with a low enough kv to make sense given the battery voltage and my weight (200lbs + ~30lbs for bike/battery/etc). I have found some potential motors (80xx size) on freerchobby's and ant innovations websites, does anyone have any recommendations?
Single stage RC left hand drive
- Thread starter thepronghorn
- Start date
thepronghorn
1 kW
What speed and power level are you targeting? The baserunner has similar phase current to the cheap focer 2 I am using, so you'll get similar torque if you match my gearing and motor Kv (160 for my motor). If you want more torque, then you'll need a bigger motor and lower Kv or a larger reduction ratio.
As far as motors go, 80xx is the next step above 63xx. There are also 9235 (aka 8318) motors which should be even torquier with less mass, but they won't fit under the downtube as well and their mounting/shaft configuration isn't as easily used with a sprocket.
So to start off, this is my first attempt at a moped beyond a AIY kit (assemble it yourself), and my knowledge of electronics is rudimentary at best (working on it). Phase amps from the controller are still over my head knowledge wise and were not considered. What I do think/know (please correct me if I am wrong) are the basic assumptions below:
Battery Voltage x kv = unloaded motor RPM, loaded rpm is ~70% of unloaded RPM.
It’s better to underload a big motor than overload a small motor for lifespan/function.
For best responsiveness I need a sensored motor.
Targeted top speed would be 50-60 km/hr, my average speed over entire trips should be ~ 30 km/hr. It is hard to say about power levels as I need to compare it to a front DD hub; I would like decent acceleration from stop, and better hill climbing power than what I have. Easier wheelies would be a perk
.
I plan on using single stage reduction, with a 150T wheel sprocket, 15T motor sprocket, and a 25H chain, for a 1:10 ratio. Since the wheel sprocket is custom made, I went with 150T to have more wiggle room with off the shelf smaller motor sprockets.
Planning to use a 48v battery, and ride on 700x44 wheels. The largest wheel that I might use is 29x2.6 which drops the required Kv for 60km/hr to 125. Controller will be a baserunner, and ideally I will be using my CAv3 for throttle input. Please see below "calcs".
I think I need at least a Kv of 133.5 to meet my desired max speed, but what’s best for sizing a motor? I am leaning towards 80xx based solely off the experience of others posting here and other online sources (still working on learning these things). Any key posts I should read, there's like 15+ years of great info here!
For what its worth my current moped’s electric system is a 48v Battery, baserunner, grin all-axle motor(standard winding), and I use a Cav3. This set-up is awesome for practicality and maintenance, but I want to: have rear wheel drive, centered mass on the bike frame, something more done by me (although still just A-AIY, advanced assemble yourself).
Battery Voltage x kv = unloaded motor RPM, loaded rpm is ~70% of unloaded RPM.
It’s better to underload a big motor than overload a small motor for lifespan/function.
For best responsiveness I need a sensored motor.
Targeted top speed would be 50-60 km/hr, my average speed over entire trips should be ~ 30 km/hr. It is hard to say about power levels as I need to compare it to a front DD hub; I would like decent acceleration from stop, and better hill climbing power than what I have. Easier wheelies would be a perk
.I plan on using single stage reduction, with a 150T wheel sprocket, 15T motor sprocket, and a 25H chain, for a 1:10 ratio. Since the wheel sprocket is custom made, I went with 150T to have more wiggle room with off the shelf smaller motor sprockets.
Planning to use a 48v battery, and ride on 700x44 wheels. The largest wheel that I might use is 29x2.6 which drops the required Kv for 60km/hr to 125. Controller will be a baserunner, and ideally I will be using my CAv3 for throttle input. Please see below "calcs".
| Equipment | ||
|---|---|---|
| battery | 48 | Volts |
| circ 700x44 | 2.23 | m/Rev |
| ratio | 0.1 | motor to wheel |
| loaded factor | 0.7 |
| Speed to Kv | |||||
|---|---|---|---|---|---|
| 30 | 50 | 55 | 60 | km/hr | |
| 500.0 | 833.3 | 916.7 | 1000.0 | m/min | |
| 224.2 | 373.7 | 411.1 | 448.4 | Rev/min | at wheel, loaded |
| 2242.2 | 3736.9 | 4110.6 | 4484.3 | Rev/min | at motor, loaded |
| 3203.1 | 5338.5 | 5872.3 | 6406.1 | Rev/min | at motor, factored unloaded |
| 66.7 | 111.2 | 122.3 | 133.5 | Required Kv | Kv = (Rev/min)/ (Volts) |
I think I need at least a Kv of 133.5 to meet my desired max speed, but what’s best for sizing a motor? I am leaning towards 80xx based solely off the experience of others posting here and other online sources (still working on learning these things). Any key posts I should read, there's like 15+ years of great info here!
For what its worth my current moped’s electric system is a 48v Battery, baserunner, grin all-axle motor(standard winding), and I use a Cav3. This set-up is awesome for practicality and maintenance, but I want to: have rear wheel drive, centered mass on the bike frame, something more done by me (although still just A-AIY, advanced assemble yourself).
thepronghorn
1 kW
The ebikes.ca simulator is good for comparing setups and seeing how a motor will perform. I set up a sample comparison between a 10:1 geared 160Kv motor and a grin v2 hub motor.
Motor Simulator - Tools
As far as motor size goes, you're in the right ballpark with an 80xx motor. To comfortably hit 60kph, you're gonna need to go bigger, but if you're happy with a solid 50-55, you should be good. For a 60kph setup, you probably need to start thinking about a stronger chain than the 25H.
Motor Simulator - Tools
As far as motor size goes, you're in the right ballpark with an 80xx motor. To comfortably hit 60kph, you're gonna need to go bigger, but if you're happy with a solid 50-55, you should be good. For a 60kph setup, you probably need to start thinking about a stronger chain than the 25H.
Hi alpaca123
Nice calcs
My junk pile tells me it's wise to finish version N of the them before cutting metal.
My build's quite different as I wanted a 'bicycle' weight at European speeds and my bike was 30+ lbs before electrics. Anyway, main roads here are up to 12% so it worked better to do calcs for hills before looking at cruising. The ebikes.ca sim corresponds well with my road speeds, doing a better job than allowing 70% for loaded RPM.
Design got easier when I set 'must have' baselines, 50-60 km/h differ by a factor of 1.7 in power and in our market that's two different bikes
You could run calcs at the extremes of HVC, LVC, sag on full power, hot controller, coldest temperature etc. Life's a whole lot easier if you're happy to plan ahead for a session at 60 km/h rather than having it always on tap.
Nice calcs
My junk pile tells me it's wise to finish version N of the them before cutting metal.My build's quite different as I wanted a 'bicycle' weight at European speeds and my bike was 30+ lbs before electrics. Anyway, main roads here are up to 12% so it worked better to do calcs for hills before looking at cruising. The ebikes.ca sim corresponds well with my road speeds, doing a better job than allowing 70% for loaded RPM.
Design got easier when I set 'must have' baselines, 50-60 km/h differ by a factor of 1.7 in power and in our market that's two different bikes
You could run calcs at the extremes of HVC, LVC, sag on full power, hot controller, coldest temperature etc. Life's a whole lot easier if you're happy to plan ahead for a session at 60 km/h rather than having it always on tap.
Hummina Shadeeba
1 MW
Here’s a frame that could take a belt without modifications
I added bigger bearings to the motor for the sideways load an outrunner isn’t designed for. I read worth doing.
Save up to 60% off new 27PLUS CAPABLE and 27.5/29er Mountain Bikes - MTB - Gravity Full Suspension new 27PLUS CAPABLE and 27.5/29er Mountain Bikes
new 27PLUS CAPABLE and 27.5/29er Mountain Bikes - MTB - Save up to 60% off new Mountain Bikes - MTB - Gravity 27 Speed Full Suspension new 27PLUS CAPABLE and 27.5/29er Mountain Bikes - xc racing - hardtail - XTR - Kinesium
www.bikesdirect.com
I added bigger bearings to the motor for the sideways load an outrunner isn’t designed for. I read worth doing.
Attachments
Last edited:
@Hummina Shadeeba that is a pretty cool frame. My plan is to do the same with a motor mount instead of a custom bike frame, and run a left side drive.
Once my motor arrives and a can check the mounts I've designed Ill let you all know how it works out and start a thread of my own.
Once my motor arrives and a can check the mounts I've designed Ill let you all know how it works out and start a thread of my own.
thepronghorn
1 kW
alpaca123, what motor did you end up going for?
I ended up ordering a 7070 110Kv from amazon, and a 6384 150Kv from freerchobby. Combined including shipping they came out cheaper than a single 80xx before shipping and duties on my end from any source.
This made me remember to order a L1019 connector from Grin!
Both motors should work as my employment location changed last week and now my commute is: shorter, through downtown roads (no time/point to get up to speed due to lights), and on shared pathways (pedestrians/dogs/toddlers etc). I no longer need what I originally wanted for top speed or power (no where reasonable to hit 60 km/hr without looking like a jerk). The new office has showers and secure indoor bike parking too
.
