Anyone run a 10x5 in a 20" wheel?

[auraslip]

Not for a hill climber or a dirt bike, but a near highway speed cruising bike meant to run at WOT and peak efficiency with very little starts and stops. A rural cruising bike for those of us who don't have to worry about the law or traffic lights.

I know the common theme on the sphere is to get the hub with the most copper (8x8) and throw enough voltage at it to get the speed you want, but you're looking at a lot of voltage to get up to 45-60mph. Lots of complications too in a high voltage setup. Higher voltage components, charging, lots of wiring, lots of cell logs, money money money.

The idea I'm toying with is dual 10x5 s in 20 inch rims (comes stock from ebikes.ca!) with 16" motorcycle tires, 2x lyen 12fets, on 18s lipo.


10x5 @ 66v with a 22" wheel size

So cruising just above 40mph I'll be a bit about 80% efficiency and using around 1500w. This is well within what ONE properly ventilated 9c can take. Since I'll be running at full speed 90%, I'm not even sure more than one motor will be needed at this voltage. And I'll only be doing 22 amps. The 12 fet could handle that without blinking.

Am I really off with this? I just wonder because it seems no one in here has done something like this, but that may be because most people want a dirt bike, live in hilly areas, or have to deal with lots of stop and go traffic.

 

[dogman dan]

2805 you mean. Not sure what it's called in the other nomenclature, 10x5? 6x10 -2810 is the slow winding.

I have assumed that the 2805 in a 20" rim has similar speed performance to the 2807 in a 26" rim.

Dual motors on any bike would be nice. Push 1500 watts through each one and little worries about meltdowns. 3000 watts is fun for sure!

 

[neptronix]

Geez, can the 9C/MXUS 9C clones not handle more than 1500w constant?

I got one coming to me to test out.. was planning on running ~2250w constant to it ( 72v x 30a )

 

[auraslip]

I put 1500w through my stock 9c all the time....... probably ventilate it if you're worried.

thanks - fixed my nomenclature error.

Also does the power needed to go 40mph seem a bit low? I was using that old chart lying around...

 

[ecross]

.

 

[dogman dan]

If it was truly constant, I bet the 9c's limit is pretty close to its rating. Isn't that somewhere around 500-700w?

Once above 1000w, it becomes a matter of, "it depends". Cruising on the flat, in moderate weather, pulling 1500w may only be making 300w of heat, and the wind is helping cool the motor. Climbing a long hill, maybe you are making 500-1000w into heat, and not going fast enough to cool well either.

Both cases would be "1500w continuous". One will melt a motor for sure!

But happily, in the real world, we rarely use high watts continuous. Even 40 mph travel on the flat is not using all 3000w. So you can get away with about 20- 30 min of hauling ass on the flat streets. At the end of the ride, you will have a very hot motor, hot enough to stink the first time you do it. 40 min at 3000w controller settings has melted motors twice for me. I learned to make my battery too small for 40 min of that kind of wattage.

In my motor testing years ago, exploring the limits of 1000w and searching for the fastest reliable ride home up a big long hill in desert heat, I found the continuous wattage varies with the weather. Motors stay quite cool if the ambient temp is below 80F. A long enough hill on a hot day, and the motor temp would just keep climbing till I stopped at a red line I had arbitrarily set at 170F measured at the winding. But on a moderate hill or a flat, the motor would reach an equilibrium temperature at about 150F, and stop getting hotter. Interestingly, the continuous wattage I was pulling was just about exactly the same as the motors rating. At 700w continuous, I could ride all day and never overheat the motor even in 110F temperatures. But at 1000w, I would tend to overheat, or at least heat past 170F if the hill was longer than 2 miles.

Those tests were being done with an aotema motor btw, I believe the larger covers on the 9c motor radiate heat slightly better.

 

[dogman dan]

Looking at that chart, I don't see how it's going to take you more than 3000w to cruise at 25-30 mph. You can pull it getting there from zero of course. But cruising at 30 mph should not take more than the normal 1000 w or so.

But like I was saying, cruising at 40 mph with a 9c motor, bet you cant run more than 30 min without having a very hot motor. How hot can depend on the weather, but even on 50F mornings, I've really heated a 9c motor up fast at 45 mph.

So no long distance cruising at 40+ mph with a 9c motor. I think many of us have proven that can't be done in most normal weather. Vent holes only do so much. My impression is that they are just good for faster cooling after you stop, helping minimize the heat soak when you stop. Or shorter waits, if you stop in time, till you can ride again.

Of course, dual motors is the way to go for long cruises. Whatever your bike speed is at 3000w continuous, you'd half it with dual motors. Dual motor, you could very likely go for quite long rides on the flat at 40 mph.

 

[auraslip]

What dogman said. Exact same experience. About 30 minutes with a ventilated 9c at 40mph. Or more realistically - until the battery goes flat.

 

[nechaus]

My 100kg body can only ride my 9c for so long, and i have ultra lov kv rating motor...
how ever my 70kg friend has no problems riding my 9c


The magie pie does last longer with myself 20mins of hard core riding and motor controller abuse.... but it takes my 70kg friend anywhere.. does not overheat..

I think the mp has a higher copper fill

 

[Philistine]

I put a 20 inch 2805 into a trike for a mate. I had been intending on building a small high powered BMX (20s50amps), but in the end I used it to power my mates (who is 78 years old) tadpole trike (he uses it for exercise and mobility), but because of his particular needs, we kept it to 10S. Even on 10S it was awesome. It would fly up hills and had good stop speed. I personally think you are on the exact right track (ie, high speed motor in small wheel). I never got to try out the wheel with the 20S I had planned for it, but after fanging around on it with just 10S I wished I could have tried it out with some real voltage.

That is the bike I would like to build next, a bike that is comfortable for an adult (not to pedal, just to sit on and handle), but to have 20 inch wheels and a built/contained triangle for batteries etc, with some storage or carrying rack/space on the back. I was just amazed at the awesome combination of torque and speed with the smaller wheel. To me hub motors (I am talking about medium to high speed winds, the only kind I am interested in, I hate slow speed wind motors) really should be kept in 20inch wheels.

 

[dogman dan]

Definitely the higher speed motors shine in that small a wheel. Grin sells them that way for a good reason.

 

[zombiess]

I have a 10x6 in a 20in wheel and love it! If you will be lacing your own a 10x6 aka 2806 is great and has more copper fill than a 10x5 aka 2805 unless they decided to use thicker wire in the 2805. From experience I can tell you a 2860 on 100v lipo is fast and lots of fun, but if you want a 20in pre laced and the faster wind for less voltage to get speed go with the 2805.

 

[auraslip]

With a fast motor you could use a lower voltage pack and therefore a mosfet with a lower rdson. Why don't more people do that?

 

[SoSauty]

I recently run my 2806/24"wheel at 20S/30A peak 2.4K. Not worried about heat for the <15min racing at Adams 6/15. Top speed was close to 35mph.

Yep, your chart underestimates the Watts needed for 40mph cruising. It's an extremely optimistic power requirement. If semi-upright comfortable riding posiiton is used along with viable tires and tire pressure, you come closer to 3000watt to hold 40mph.

As to why some of us don't run the 2805, the 9C (and others) seems to have an optimal balance between torqueKv/hi-volt vs speedKv/mid/volt. As Zombiess mentioned, more copper equals more power as well. The 9C 2806 loves 20S and sprints great with 24S on the sub 20min runs. Controllers to handle 20S are easy to find and controller techies will get performance out of anysize controller.

I'm looking at running dualies also, just unsure if a single throttle will signal 2 controllers. Hope you have a go at dual 9C's and post a thread for it.

 

[neptronix]

Look up the 2805 on a 16" wheel on 90v nominal.

How 'bout 2600w constant?

 

[electr0n]

I am currently considering doing this with my HS3540, that is running it in a 20" bicycle wheel at 88.8v for fast acceleration and efficiency. If I could go back I'd be tempted to go with the HS3548 running in a 20" wheel. Since I've got an HS3540 I kept going back and forth trying to decide between my next controller being 4115 or 4110 based because the top speed at 88.8v in a 20" wheel is only 66kph. I decided to stick with the 4110 and go with higher speed windings for my speed requirements. Really the only thing holding me back from moving to a 20" rear wheel is the pedal clearance issue more than anything else.

 

[auraslip]

Well, you can always get a pedal tap to make Shorty pedals