Smallest motor that packs a punch

What’s the smallest motor you can use on a single drive build that’s capable of carrying 200lbs of load and can still go uphill? Building a light, stealthy, easy to carry, round-the-neighborhood board.

A single 5065 motor at 140kv geared-down at 15:40 or 15:44 and running at 10S on 107mm wheels

1 Like

uphill is very relative. 10% or 20%…Makes a hughe difference. Also going up hill slow is putting more strain on things. Going uphill fast is a lot more easy to achieve. Brands fool people by posting videos of fast uphill runns. Users think fast and steep hill climbing must be very hard to achieve. Slow and steep is the challenge…

https://vesc-project.com/calculators

6364 or 6374 is quite good for singles. Longer is better, more diameter is better. KV around 140-160. Housing should not be closed, so you get good airflow.

Frank

5 Likes

My mind is blown any reading material you can share so that I could understand this concept?

Is this something about gearing?

1 Like

Any specific brand of 5065? 107mm wheels might be a bit too big for a stealth build though.

My single 190kv 2000w 6364 motor on 9s lipos,

can pull me up a steep looking hill at like 30km/h and it’s top speed is a bit over 40 km/h.

Gearing: 90mm wheels 36/15

I was thinking the 6374 really fits the bill. I was just thinking if there was something smaller that’s still up to the task.

I think I understand that bit about going fast uphill and deliberately going slow bit and I agree.

E-Motors are efficient at high RPM, but inefficient at low RPM and high torque output. Going up a hill slow, you will push a lot of Amps to generate the torque you need and you travel up the hill for a longer period of time, since you are slower.

2 Likes

How about braking downhill, how does it perform? What are your ESC settings for this kind of setup?

Braking downhill, Kinda sucks, I think i got it on -40a But I get belt skips on a 15mm kit.

I can go up this hill at 33km/h easily if I catch a bit of speed before hitting the hill. Screenshot%20from%20201t8-06-21%2011-33-35Screenshot%20from%202018-06-21%2011-32-49

2 Likes

On smaller wheels, lower the gear ratio like 15:36 or 15:40 instead of 15:40 or 15:44

2 Likes

Going fast uphill stresses the battery more, as you’re pulling higher power, but is easier on the motor and motor controller, as they don’t have to perform at high power (current=torque) as long.

Going slow uphill inverses this relation, low battery power, but ends up heating your motor and motor controller more, as they have to sustain high current for longer.

2 Likes

But battery output should match the power of the boards motor anyway + you can define the max battery drain in VESC-Tool. What usually creates temp cutouts on hills is the motor heating up due to high Amp flow in the spools. Small commuter boards usually have smaller batteries, which is an issue for up hill performance, top speed performance and the brakes. Scaling down the battery creates issues…

It’s quite amazing what hills you can climb using a single 6364 or 6374 motor, as long as you can go fast enough up the hill and when the battery has enough voltage and P count.

2 Likes

Yes, but battery current and motor current can still be very different between them.

For example difference between battery and motor current: High speed: Power 1000W, battery voltage 40V -> battery current 25A, motor operating at higher RPMs might see 30V -> 33.3A low speed: Power 200W, battery voltage 40V -> battery current 5A, motor operating at low RPMs might see 6V -> 33.3A

In both cases the motor is producing the same torque, because same motor currents, which let’s say is the torque needed to not gain or loose speed, but power use is very different between the high and low speed examples. High speed/ low time uphill would have battery hotter and motor controller + motor cooler, whereas the low speed/ high time would see the battery cooler and motor controller and motor hotter.

Correct Mr Muffin! I want to work on a nice diagram showing how things actually are linked together. This is the part most people don’t understand when setting up their boards. A good diagram would help.

If you want to climb hills, you probably also ride down those hills and you want to use the brakes in that case. So you are aiming at a battery that can cope with the Amp flow. And this is the issue when building small and light boards. The battery is usually not capable enough and overstrained when braking for a longer period of time.

2 Likes

Using different battery max vs. motor max settings also allows you to use more acceleration or brake at lower speeds, because you can crank/regen higher motor currents, while still being under the power limit. Battery is always going to be more stressed at higher speeds, unless you limit the battery max currents, which the VESC then compensates by decreasing motor currents at higher speeds.

@trampa, I have a 10s3p and two motors. After a km of an uphill climb averaging ~10%, the board gets weak and then just stops. After I let it rest for a few minutes, it’s able to climb the hill again, but for a shorter distance this time. Is there something in the dual VESCs that I can change? Do you have any insights you can share? Thanks.

What kind of motor, gearing, wheel diameter, ESC? Without those infos nobody can help.

The smallest motor that packs a punch (for weight) will be something with a long stator with a small diameter. For the weight a 4092 inrunner has big torque. Either need a custom wind or a big gear reduction. @MoeStooge has made it work a handful of times so you just need to be creative or order a custom from Alien.

This little fella (4092) makes 4200w. 8:1 gearing on 8s makes 34mph on 70mm wheels. Have used this setup to pull a 190lb friend on a DH board back up the hill multiple times. Honestly this single will rival many dual motor setups in acceleration and speed. Screenshot_20180604-082522 IMG_20180624_165922296 IMG_20180624_165928083 IMG_20180623_130202620_HDR

11 Likes