Slowest Motor 1500watt max?

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Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 01, 2017 3:38 pm

I need a very slow motor to power my friends cargo bike. We don't want to build a large gear reduction. I figured that for a 3000 rpm motor it would take a 18:1 reduction (for about 13mph with a 26inch tire) a 3:1 reduction would be much easier. But A 9:1 ratio would be good for a 26” tire if the motor runs at about 1500rpm at the power needed.

Can anyone recommend a very slow but high enough power motor?
Is the Mac 12t the only option?

On this page https://em3ev.com/shop/mac-5001000w-motor it says the 8t motor is good for 50kph at 48v on a 26inch rim (I think they mean OD of tire) but this does not tell me what I need to know.

ok down on the page I found the rpms out put 12 turn standard motor 12 turn low speed extra torque motor – 200rpm loaded at 36V I think that may do it.......

As a guideline you can expect approximately the following real world speeds for the above windings on 12S LiFePO4 battery pack (approximately 38V under load) in a 26″ rim on the flat, no pedaling with a rider plus bike weight of approximately 130kg total (286pounds):

6T – 45kph (28mph)

8T – 39kph (24mph)

10T – 32kph (20mph)

12T – 25kph (15mph)

I see that grin tech's motorsimulator has been rigged to not calculate 250kg or 551lbs..... so what can I do now.
I definatly do not want to use a geared hub motor.

here is a sprocket to speed caculator https://www.electricscooterparts.com/mo ... atio-guide

Image

Now I need a photo of the right way to rig it.

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 01, 2017 5:11 pm

So these Mac motors geared hub motors? (5:1 planetary gear with clutch is implemented) well that troughs off all my feverish calculation. So maybe I can just add the 5:1 reduction to the total to get the right ratio.

But I need a 12 turn (or should that be 8 turns?) direct drive hub motor with good ventilation, or equivalent....

I want a 1500watt motor that says 750 or 1000 watts on it. I know the lightning rods kit would be good for all that, but the gear reduction will need to be even more than the kit.

I give trying to understand the motor simulator.




they are modifying the java script on the page to add a little drop out box:

Image
Last edited by Hugh-Jassman on Sep 03, 2017 12:07 pm, edited 1 time in total.

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Re: Slowest Motor 1500watt max?

Post by liveforphysics » Sep 01, 2017 8:04 pm

Being wound for a lower kV (RPM/Volt), doesn't make that motor capable of any more torque or continuous torque. Just changes that the controllers phase current happens to be to make that torque.
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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 02, 2017 3:53 pm

So does that mean I should just forget the slow motor concept and go for a fast motor? Looks like I would have to have at least one stage reduction before the wheel anyhow.

Also I am going to have to limit the whole thing to 450lbs total combined weight.


liveforphysics wrote:Being wound for a lower kV (RPM/Volt), doesn't make that motor capable of any more torque or continuous torque. Just changes that the controllers phase current happens to be to make that torque.

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Re: Slowest Motor 1500watt max?

Post by liveforphysics » Sep 02, 2017 4:10 pm

Hugh-Jassman wrote:So does that mean I should just forget the slow motor concept and go for a fast motor? Looks like I would have to have at least one stage reduction before the wheel anyhow.

Also I am going to have to limit the whole thing to 450lbs total combined weight.


liveforphysics wrote:Being wound for a lower kV (RPM/Volt), doesn't make that motor capable of any more torque or continuous torque. Just changes that the controllers phase current happens to be to make that torque.

The ultimate winding doesn't matter, the best you can do is pick a motor that works well with the controller you have in mind.

I'm personally a fan of lower voltages for lower power levels, but many methods work. No method of equal power levels buys you a meaningful difference in climbing performance without having more iron or copper in your motor.
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Re: Slowest Motor 1500watt max?

Post by Chalo » Sep 02, 2017 4:21 pm

Hugh-Jassman wrote:So does that mean I should just forget the slow motor concept and go for a fast motor?
No. The slower winding allows you to use a much more normal battery and controller and lighter gauge wiring, and to operate at higher efficiency at low speed.

If your power is a fixed amount, and you want to maximize torque at that amount of power, you have to reduce speed to match. So you want a motor that runs efficiently at a suitably low speed.

I think your job is for a geared hub motor (or two), or for a shafted motor with lots of reduction, but not a direct drive hub. What is the problem with using a mid drive like BBSHD?
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Re: Slowest Motor 1500watt max?

Post by Triketech » Sep 03, 2017 11:04 am

From my experience with both a MAC 12T and 10T both are stout motors at lower speeds. 550 lbs on climbs could strain the internal reduction gears & clutch on climbs.

Starting with efficiency, the frequency of pole switching events has the largest effect at lower speeds. Virtual rotor speed. You can get an idea of that about halfway down in this article:
http://www.triketech.com/Drivetrain/Pow ... AC-V2.html

The Grin simulator is an exceptional tool, when used for comparisons but in the real world one finds their usage often deviates from what they were inputting.

From my testing at 52V @ 20 amps the 12T delivers more torque than the 10T up to about 12-14 MPH and the 12T thermal rise isn't as fast as the 10T. Above 16-17 MPH the 12T torque begins to taper off a bit below the 10T. Above 18 MPH the 12T thermal rise is slightly higher than the 10T. That's from testing on hills of 7-10% with a 265 lb trike.

I can't tell you if that agrees with the simulator, so much as that's real world results.

Internal gearing has its limits. The 12T at 40 amps would spin the tire off the line. It also made a few dreadful sounding noises that sounds like gears stripping, but it was actually rotor slip which can occur under high loads when the stator leaves reach saturation. In the short time I ran at 40 amps the audible noise level from the internal gears increased a bit and even with reduced current the 12T is now louder then the nearly silent 10T. That testing was done with the same Infineon 12 FET trap controller, I now run the Phaserunner with the 10T. You will be better off with the Infineon 12 FET trap controller.

Your looking for hill-boosts. Here are a few numbers to start with:

5MPH on a 5% grade will require 274 watts of output just to lift. At that speed the efficiency will be much higher for a geared vs direct drive nearly double. Less heat to shed.

Required output power is pretty much a linear increase to speed or grade. So at 10 MPH on 5% or 5MPH at 10% just double the watts required. But here is where it gets challenging; how many watts in to get the required output depends on efficiency which also depends on the speed.

Limits. You have a 36V battery that I would assume (LiFePO4) capable of 30A continuous (check, including BMS). That allows a budget of about 1080 watts. If you pedal at about 30-40 watts (overcoming rolling/areo drag) at 7 MPH climbing a 10% grade the efficiency of the MAC12T will be in the 68-71% range; that provides about 750 watts to the ground, and 330 watts to heat. Most typical DD motors will be down in the 50% range and below in the real world.

Trouble is at that speed it won't shed heat fast enough for sustained rides, and you'll be building heat at a rate of about 300 watts. A simple rule to convert that to thermal rise is every watt-hour of heating will raise 1 Lb about 3° F. So that begs the question of how tall is the hill?

Lets work with 100 foot climb increments. 7 MPH @10% will take 97 seconds. 97/3600 = .027 hours, multiply by 300 watts = 8.1 watt-hours = 24 BTU. The stator assembly weighs about 5 Lbs, so 24/5 = about 5° F.

These numbers are part of a spreadsheet that I've been developing for a few years now from real world testing. It does deviate a bit from the simulator which again is an excellent comparison tool, but somewhat limits the user in accurately inputting/defining real world application.

Bottom line is I would recommend the MAC 12T at a 30A max limit with the internal temp sensor connected. It wouldn't hurt to have a spare set of planet gears and clutch on hand, if it does fail you can still pedal (or push) home but you won't be stranded for long. Gear life is a bit tricky to project as the AGMA gear wear rate formula depends a bit on the tribilogy of the nylon gears and that's not a linear value. My best guess is you'll get at least 1000 miles under worst case, but probably closer to 2000 miles at the 1080 watt limit.

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 03, 2017 12:05 pm

that make the slower motor even more atractive...I really don't want to use ageared hub motor but I have not seen another slow wind motor that would do about 1200 rpm. (rough estimate in my rusty mind)

I am NOT looking for more SPEED nor am I looking for more THRUST. Although it will create a little more thrust, just because it will be easier to gear the motor power down to the right wheel speed. I definitely do not want to build a three stage or even two stage reduction.

I believe that a 6:1 ratio can be done in a single stage reduction. But I may need to make a belt pulley out of a 12 inch rim, or at least a 16 inch rim. And maybe even make some splash guards to help keep the road grit out of it. Infact if some one wanted to do it right they could just use a single gear hub like in this thread that used a two disc front motorcycle hub to hold the sprocket: https://endless-sphere.com/forums/viewt ... it=skeetab. But my friend wants to keep his 10 speed cassette hub and the wimpy drive chain. So I will have to build it on the left side around the disc brake.

If I can't obtain the correct gear ratio with a single speed gear reduction, this device may never be built. Even if it is only because of the price of a multistage reduction.

As for steep hills, off road terrain is not needed. Some of our hills go up to a 16% grade for a short distance. But they are avoidable. And I don't know many people that can pedal even an empty bike up even our milder hills. Even I have a hard time pushing my empty yet heavy utility bike up the main 9% grade that cannot be avoided.

Chalo wrote:
Hugh-Jassman wrote:So does that mean I should just forget the slow motor concept and go for a fast motor?
No. The slower winding allows you to use a much more normal battery and controller and lighter gauge wiring, and to operate at higher efficiency at low speed.

If your power is a fixed amount, and you want to maximize torque at that amount of power, you have to reduce speed to match. So you want a motor that runs efficiently at a suitably low speed.

I think your job is for a geared hub motor (or two), or for a shafted motor with lots of reduction, but not a direct drive hub. What is the problem with using a mid drive like BBSHD?

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Re: Slowest Motor 1500watt max?

Post by SlowCo » Sep 03, 2017 1:16 pm

Can't you use a DD 1500W (Leaf or Edge) as a Stoke Monkey mid drive setup?: https://endless-sphere.com/forums/viewt ... =6&t=38553

Or use the Cyclone 3000W: https://endless-sphere.com/forums/viewt ... 28&t=69867

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 03, 2017 5:28 pm

no the mid drives require a stronger drive train. but I could check the leaf for 12t slowness....


SlowCo wrote:Can't you use a DD 1500W (Leaf or Edge) as a Stoke Monkey mid drive setup?: https://endless-sphere.com/forums/viewt ... =6&t=38553

Or use the Cyclone 3000W: https://endless-sphere.com/forums/viewt ... 28&t=69867

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 03, 2017 5:38 pm

I am not looking for “hill-boosts”!!! I am looking for a way to build the right gear ratio without spending too much money at the machine shop.

Yes I know a faster motor is more efficient, but also more expensive (Unless I just have to spend the money saved on a larger battery).

Image

What I am trying to estimate with these graphs is simply what gear ratio I will need so I need to know what rpm it will use. Unfortunately I need a different motor. Maybe the one in the photo above with different controller, one that is programmable. The motor with the 1000w controller is no longer available.

So I am starting to think that I will have to just choose a motor that looks like it may work a then rig it with a 5:1 ratio reduction and try it out to see how it hot it gets, not a very good idea, because it may take a 7:1 ratio. Which would require a larger rim pulley than 12 inches.

Now if I could just drink some more caffeine and or sugar, I would be able to calculate the gear ratio from the graph. or just add 5:1 after I use this calculator: https://www.electricscooterparts.com/mo ... ratio.html

sorry wrong graphs



This one looks the best, what do you think? Is there any motors that can come close to the rpms and wattage of this one. maybe I should just take out the planitary gears and put some fans in it to help cool it?

Image


Did I forget to say that I do not know what controller to use nor do I know enough about batterys to choose one yet. But I do know that I need the right gear ratio. If I can't get past that design stage the rest is useless.
Last edited by Hugh-Jassman on Sep 03, 2017 8:05 pm, edited 2 times in total.

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Re: Slowest Motor 1500watt max?

Post by liveforphysics » Sep 03, 2017 6:35 pm

That photo with a 5:1 gearing reduction is magnetically a similar model as a direct drive hub of similar width with ~2.5x the motor radius (which would likely weigh more).

None of the windings (that share equal copper cross-section in the slot between teeth) you pick give the motor any climbing or torque production advantages or continuous torque or continuous power advantages.

You can only pick something to be a good match for your controller/battery options. Since you don't want speed a low Kv winding (high turns count around tooth) enables a smaller size controller and a few feet of wire can be lighter gauge or run cooler for the same gauge.
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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 03, 2017 8:11 pm

could you explain that in terms for dummies like me?

I really am not looking for any "climbing or torque production advantages or continuous torque or continuous power advantages". I just want to avoid making a two or three stage gear reduction.

liveforphysics wrote:That photo with a 5:1 gearing reduction is magnetically a similar model as a direct drive hub of similar width with ~2.5x the motor radius (which would likely weigh more).

None of the windings (that share equal copper cross-section in the slot between teeth) you pick give the motor any climbing or torque production advantages or continuous torque or continuous power advantages.

You can only pick something to be a good match for your controller/battery options. Since you don't want speed a low Kv winding (high turns count around tooth) enables a smaller size controller and a few feet of wire can be lighter gauge or run cooler for the same gauge.

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Re: Slowest Motor 1500watt max?

Post by Chalo » Sep 03, 2017 9:00 pm

Hugh-Jassman wrote:I believe that a 6:1 ratio can be done in a single stage reduction. But I may need to make a belt pulley out of a 12 inch rim, or at least a 16 inch rim.
The first e-bike I made for myself used a 400W Unite can motor with 12t small pitch chain sprocket driving a 144t sprocket I made that mounted to a left side freewheel. 12:1 reduction made 400W adequate for climbing central Seattle's hills with more than 450 pounds gross. (I did help with the pedals.) As long as you don't put the small and large sprockets too close to each other, you can get quite a lot of reduction in a single stage.

For large reductions with a belt drive, I'd definitely use a toothed belt (e.g. Gates HTD). Using a tiny v-belt sprocket is asking for slippage. You can wrap a toothed belt inside out around a sheave to make the driven sprocket.
Last edited by Chalo on Sep 06, 2017 4:46 am, edited 1 time in total.
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Re: Slowest Motor 1500watt max?

Post by liveforphysics » Sep 03, 2017 9:08 pm

Hill climbing performance is directly related to continous torque capability at the rear wheel.

You can achieve this with an adequate gearing reduction (go as aggressive as you can package if the vehicle intent is climbing) and a tiny motor, or a bigger diameter motor directly driving the wheel (or internally geared hub).

I think the best path to go with the tiny motor and gearing option if you have budget is the bottom bracket motor options, as it's easy to use any rear sprocket you want and the controller is usually integrated and the gearing quiet on the units I've tried (BBS02 and BBSHD).
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Re: Slowest Motor 1500watt max?

Post by SlowCo » Sep 04, 2017 4:10 am

Hugh-Jassman wrote:no the mid drives require a stronger drive train.
No, they need lower gearing.

I tried to understand what it is you want to achieve. If I'm correct it is about a heavy cargo bike with a 26" wheel that only needs to go around 13mph? So a DD motor is not the best choice for this application. You should use a mid drive of some sort and use low gearing. But if you insist on a DD hub motor make sure it is in a small 20" bicycle wheel (or a 16" moped rim for strength). That way you have lower gearing by reducing the circumference of the tire.

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Re: Slowest Motor 1500watt max?

Post by Wheazel » Sep 05, 2017 1:54 am

When I built my cargobike there was a lot of naysaying about switching from a revolt 120pro to a dd hub.
I was unhappy with the efficiency I got with the revolt, so I ordered a Leaf 1500 motor(5T I think). This was in a 26" wheel and the bike has a 18s large capacity battery.
I usually run with a 35A current limit, which is above 2kW and seldom reached.
The bike itself is probably 60-70kg, +me 75kg, +cargo (almost never more than 50kg). So maybe lighter than your needs.

Anyhow, that setup worked well. Would probably overheat if climbing a mountain, but no sweat for the quite hilly town I live in.
Later changed to an mxus 3k (4T) due to the lacing of the leaf 1500 gave up gradually, and had the mxus at hand.
The mxus is in a 21" moped rim and provides slightly more torque for my chosen current limits.

This tells me that a hub like the leaf 1500 in a small rim like 20" would be quite good at climbing.
I would choose the leaf 1500 + a 24" bikerim if I would relace the leaf for the cargo bike, over the mxus.
The leaf in a 26" bikerim was more efficient than the current mxus in a 21" moped rim.
The rear tyre differ between the two, but the leaf is probably a slightly more efficient package due to smaller size.

This might or might not be a niche case, riding speed is most usually 30-40km/h.
Steep uphill slopes around 25km/h, unless I allow for more power to the motor.

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 05, 2017 2:38 pm

What I want to build is simply a mid-mounted slow motor with a single gear reduction. If I can't find a slow pancake motor with good venting, I ma need to use a mid drive kit with way too much gear reduction directly to the rear wheel with a belt with out going through the drive chain.

All I need is more caffeine and a better internet connection.....of course no one makes the kind of motor I need because no one wants to make a slow hill climbing machine.

I am glad you said that about it needing a lower gear. it makes very good sense.


SlowCo wrote:
Hugh-Jassman wrote:no the mid drives require a stronger drive train.
No, they need lower gearing.

I tried to understand what it is you want to achieve. If I'm correct it is about a heavy cargo bike with a 26" wheel that only needs to go around 13mph? So a DD motor is not the best choice for this application. You should use a mid drive of some sort and use low gearing. But if you insist on a DD hub motor make sure it is in a small 20" bicycle wheel (or a 16" moped rim for strength). That way you have lower gearing by reducing the circumference of the tire.

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Re: Slowest Motor 1500watt max?

Post by fechter » Sep 05, 2017 2:55 pm

I have a BBSHD with a 30t chain ring and it climbs very steep terrain with no problem. No more overheating either. With that gearing, my top speed in the lowest gear is about 10mph. When climbing, the motor is significantly more efficient than my other bike with a DD hub motor. I have been really impressed with the BBSHD so far. Having the option to change the gear ratio is great for specialty applications.
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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 05, 2017 3:05 pm

I assume that the unit you are talking about is the Bafang mid drive...? this is not what I need....


fechter wrote:I have a BBSHD with a 30t chain ring and it climbs very steep terrain with no problem. No more overheating either. With that gearing, my top speed in the lowest gear is about 10mph. When climbing, the motor is significantly more efficient than my other bike with a DD hub motor. I have been really impressed with the BBSHD so far. Having the option to change the gear ratio is great for specialty applications.

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Re: Slowest Motor 1500watt max?

Post by SlowCo » Sep 06, 2017 6:46 am

Hugh-Jassman wrote:this is not what I need....
It seems nobody knows what you need including you yourself... :roll:

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 06, 2017 1:58 pm

ok just keep tuned and find out......

SlowCo wrote:
Hugh-Jassman wrote:this is not what I need....
It seems nobody knows what you need including you yourself... :roll:

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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 06, 2017 2:00 pm

ok this is understandable now. So what I am doing is just an attempt to make a cooler climbing situation....? That sounds good. And it will use less power? That is good....I knew I was doing something right....

But the other way to do it would be just use a larger amp controller? Which would use more amperage? Heat, power, etc.

So if the gear is right for the motor, I will not need to drill vent holes in it? That is good. But what is the right gear for the Leaf 1500watt motor?

By the graphs for the 1000watt motor it looks like the leaf goes up to about 750rpm at 1000w on 50volts, so a 1:4.5 ratio would bring the wheel speed down to about 13mph.

https://endless-sphere.com/forums/viewt ... 89#p999435

I would still like to find a better motor that would fit...
How does the Leaf compare to the Stoke Monkey? And aren't there any stronger motors rigged like the StokeMonkey???





liveforphysics wrote:That photo with a 5:1 gearing reduction is magnetically a similar model as a direct drive hub of similar width with ~2.5x the motor radius (which would likely weigh more).

None of the windings (that share equal copper cross-section in the slot between teeth) you pick give the motor any climbing or torque production advantages or continuous torque or continuous power advantages.

You can only pick something to be a good match for your controller/battery options. Since you don't want speed a low Kv winding (high turns count around tooth) enables a smaller size controller and a few feet of wire can be lighter gauge or run cooler for the same gauge.

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Re: Slowest Motor 1500watt max?

Post by liveforphysics » Sep 06, 2017 3:57 pm

I believe you mean well while seeking a complex weak and inexperienced vehicle.

Ebikes may also optionally be quite robust hillclimbers (even with purposeless crippling like a 1500w limit.)
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Re: Slowest Motor 1500watt max?

Post by Hugh-Jassman » Sep 07, 2017 1:25 pm

I think I read some where that most hub motors are vertualy the same.....so that the stoke monkey would work ok with a low enough ratio....buy it should be lower than the average bicycle gear ratio.

liveforphysics wrote:I believe you mean well while seeking a complex weak and inexperienced vehicle.

Ebikes may also optionally be quite robust hillclimbers (even with purposeless crippling like a 1500w limit.)

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