Puzzling motor turns and Grin simulator

[MikeSSS]

Puzzling because of preconceived notions, that the simulations do not support.

What I thought: more turns give more low speed power, fewer turns give more high speed power. But, hmmm, I seldom use full throttle, so it is better to compare turns vs actual riding use. I'm old, play racing was 50 years ago, now I ride slow and look at critters, plants and geology. So, I put my riding use into the simulator and viola, almost any hub motor will work. Whatttt? Yep.

First run was 6.5% grade and 5 mph. Next was 0 grade and 12 mph, after that 0 grade and 17 mph. After this was wide open throttle with a 20 amp controller and then a 40 amp controller. Motors were, from top down, 9C 5 turn, 6 turn and 7 turn. Then a Bafang BPM, GO1 and finally a BMC V2 torque. The first three are direct drive, the last three are probably geared hubs.

turns motor mph grade % batt watts mph grade % batt watts mph grade % batt watts
5.0 2705 dd 5 6.5 397 12 0 137 17 0 282
6.0 2706 dd 5 6.5 355 12 0 125 17 0 276
7.0 2707 dd 5 6.5 340 12 0 128 17 0 273
BF gear BPM 5 6.5 292 12 0 130 17 0 286
BF gear GO1 Std 5 6.5 340 12 0 130 17 0 284
BMC V2 trq 5 6.5 265 12 0 144 17 0 286

Note: fewer battery watts drawn is better. Note 2: this is from an Excel spreadsheet, correct formatting of columns did not come over. If preview comes out wrong, I'm not fixing it.

Conclusion: if the BMC V2 torque hub simulation is correct...what are the chances...then this hub is better for 5 mph climbing, at far less than full throttle. At 12 and 17 mph, all the hub motors are close to the same performance. At wide open throttle, fewer turns, results not shown, were faster, especially with a 40A controller, vs a 20A controller.

Hmmmmmm.

PS, the column formatting did not carry through. Why should it?

Note: on the Grin hubmotor simulator, when choosing a motor to model, go to the bottom and click "show all".

 

[markz]

Puzzling because of preconceived notions, that the simulations do not support.

What I thought: more turns give more low speed power, fewer turns give more high speed power. But, hmmm, I seldom use full throttle, so it is better to compare turns vs actual riding use. I'm old, play racing was 50 years ago, now I ride slow and look at critters, plants and geology. So, I put my riding use into the simulator and viola, almost any hub motor will work. Whatttt? Yep.

First run was 6.5% grade and 5 mph. Next was 0 grade and 12 mph, after that 0 grade and 17 mph. After this was wide open throttle with a 20 amp controller and then a 40 amp controller. Motors were, from top down, 9C 5 turn, 6 turn and 7 turn. Then a Bafang BPM, GO1 and finally a BMC V2 torque. The first three are direct drive, the last three are probably geared hubs.

turns motor mph grade % batt watts mph grade % batt watts mph grade % batt watts
5.0 2705 dd 5 6.5 397 12 0 137 17 0 282
6.0 2706 dd 5 6.5 355 12 0 125 17 0 276
7.0 2707 dd 5 6.5 340 12 0 128 17 0 273
BF gear BPM 5 6.5 292 12 0 130 17 0 286
BF gear GO1 Std 5 6.5 340 12 0 130 17 0 284
BMC V2 trq 5 6.5 265 12 0 144 17 0 286

Note: fewer battery watts drawn is better. Note 2: this is from an Excel spreadsheet, correct formatting of columns did not come over. If preview comes out wrong, I'm not fixing it.

Conclusion: if the BMC V2 torque hub simulation is correct...what are the chances...then this hub is better for 5 mph climbing, at far less than full throttle. At 12 and 17 mph, all the hub motors are close to the same performance. At wide open throttle, fewer turns, results not shown, were faster, especially with a 40A controller, vs a 20A controller.

Hmmmmmm.

PS, the column formatting did not carry through. Why should it?

Note: on the Grin hubmotor simulator, when choosing a motor to model, go to the bottom and click "show all".

Its the same power, same torque, given the same copper fill.

 

[teslanv]

I'm sure I will get the riot act from a few members, but I say get a high turn-count (Slow Speed) winding, and a modest 36V or 48V controller & battery. 30A would probably be plenty for your needs.

When you don't need or want to go fast, I see no reason to pick a fast wind motor.

 

[dogman dan]

I get the riot act for that too. But I sell a ton of low speed motors, and everybody buying them loves them,, cuz those particular guys want to go slow. This is the guy on an adult trike, that's dangerous to ride above 15 mph. Or sometimes a cargo bike with two kids on the back. No hauling ass for them.

Slow motor IS for the guy who wants to ride slow. However,,, you can ride slow all you want with a fast motor too, if the load is light relative to the motor system.

Here's were it gets really confusing though,, the geared motors do climb better,,,, to a point. This is why the website talks about a 300 pound weight limit, for the bike, battery, rider and cargo, for the 500w geared motors. ( which we limit to about 1000w) They do climb great, but if your load is above 300-350 pounds, then the motor stalls enough on the steeper hills to overheat. The motor may be doing just as good as the DD, but it cannot cool itself as well, and there is less copper to heat up too.

So when they are going to really punish a motor with load, we still send them to a low rpm DD. And there is still a weight limit for steep hills,, but now about 400 pounds.

Even though we could sell them a motor,, once people start talking 400 pounds and steep hills,, I start sending them away to somebody who sells a motor with more magnets, a muxus, a clyte, whatever. Then they can run 2000-3000w to climb hills with a big load. And once you get that watts to weight ratio back to a reasonable level, it stops mattering so much which wind they ride.

Play with the sim some more,, adding more weight, and a steeper grade, and then you will start to see why people do return to the DD for the big weights.

 

[markz]

dogman dan - By what you typed, it sounds (to me) like you sell motors or am I totally wrong?
You do a lot of recommendations on the forum, so maybe I just misinterpreted what you typed.

 

[dogman dan]

It's in my sig,,, I'm the guy on the live chat at E bikekit, Liberty Trike, and Electric Trike.com. That's all Electric Bike Technologies.

Once in a blue moon, I actually do sell something on that chat. But mostly it's just explaining e bikes to noobs, who often as not buy something, but not till next year, or maybe they go get a cheap ass kit from amazon. Sometimes the job is explaining to a guy why he does not want to buy our kit. Like maybe he weighs 350 pounds, and thinks a 1000w kit will climb his 15% grade hill with him on it. Or he wants to go 40 mph. I explain to folks what to expect from our kits, so they don't buy the wrong one, or have totally unrealistic expectations for speed and range. We don't want to scream 30 mph and 50 miles range,, when to get 50 miles range you have to go 10 mph.

I do lots of troubleshoots as well,, walk people step by step through installing their E bikekit, or send them here when they have a problem with another brand kit. This summer will be my fourth year working the live chat. When Jason first hired me, I could barely get through a day with my chronic fatigue so bad. So lying in bed waiting for a chat was a perfect job for a guy too sick to go out much. Now I'm doing a lot better, and wish I could work a regular job. But I'm not better enough for an 8 hour shift at any other job yet.

 

[Triketech]

The Simulator only gives a set of benchmark references, and pretty good at that. But there are so many variables to the designs its not quite so simple as turn counts.

That said, between the MAC 12T and Mac 10T winds, they behave as expected.

12T has a boatload of torque up to about 10 MPH with a top speed of 26 MPH on my trike.

10T has less lower end torque up to about 12 MPH, with a top speed of 30 MPH.

Dan's right on about "extraordinary" loads, just plan on hanging a cannon ball weighted hub in those cases.

One of my routes begins with a 500 foot climb on an average 9% grade. Some points are as steep 18%. My 260 lb trike does just fine climbing at 3-4 MPH. Internal temps on the 12T report about 45° over ambient. On the 10T its about 51° over ambient. I'm guessing the 8T would probably overheat on a 100° ambient day or get close to it.

Going down the steep hills a DD is great for trimming speed, but I don't miss that too much as the brakes work well enough.