Using RC motors on E-bikes [Archive]

[Kraeuterbutter]

if you want some more motor-data (real measured data),
i would recommend this two pages:

http://www.lehner-motoren.de
(lot of world-records have been set with this motors,
for example also outside of rc-world: the Challenge Bibendum in Paris was wone with an Lehner powered vehicle,
look the article, (German, but lot of pictures): http://www.lehner-motoren.com/download/ziegler.pdf)

two directlinks:
here the available motors (from 40g up to 1600g): http://www.lehner-motoren.com/ms10.php (choose at top of side)
here a direct link to the motor diagrams: http://www.lehner-motoren.com/motordia.php

----------------------------------------------------------------------------------

http://www.plettenberg-motoren.de
they have also outrunners...
here some lists of motor-datas, diagramms: http://www.plettenberg-motoren.com/UK/daten.htm
there is also a fan available for the motors, so cooling is even better (its nevertheless also without fan good on an outrunner)

this two companies are very accurate with datas they provide for there motors
and leading in the rc-hobby scene

there are also other good companies (for example http://www.Kontronik.com) but they have not that much data about there motors on there homepage

 

[recumpence]

hey..
have you seen this ?
http://www.powercroco.de/24N28P6530.html


weight: 960g
80 rpm/Volt
he has build that motor for a bicycle

with 24Volt its around 1300 rpm under load

yes, the efficience-numbers are not at 90% like on the motors from towerhobbies mentioned here.
BUT: i also doubt this 90% a little bit..
very often (specially cheap motors) motors are far overrated when it comes to efficience..
claims of 93% and when tested on a professional motor-test-stand (for example Plettenberg does do this) you see, that some even not reach 80%
so: this 80% are real 80% Dr. Ralph Okon measured, you can trust this values..
and with that low kv (80 rpm/V) you can maybe safe some more %-points at gearing

oh:
he has also build "some" other motors:
http://www.powercroco.de/navigation.html

Hey Man!

This is Heli Mod Man from RC Groups. How have you been! Man, small world, isn't it!? GGoodrum is here too.

What are you riding?

Have you seen my bike build? http://www.wisil.recumbents.com/wisil/shumaker/default.htm

Matt

 

[Kraeuterbutter]

Hi...
yes, i have seen your bike.. didn´t know that it was yours...
a work-of-art !

i for my self was thinking about using some of my rc-components...
but because i have no mechanicing equidment (lathe, milling lathe, ...)
this seems not so easy

my idea was to make it as light as possible.. a 300g light, slow motor (Plettenberg 30-14), two-stage beltdrive (quiet), and a 1kg light battery)
power: 200Watt to the wheel would be enough (it should help me and not give me 10times more power than i have - i know, thats your concept *gg*)
and: going through the gears, so you can use even on a hill all the motorpower and not only 30% like on some hub-motors

maybe it is somewere mentioned: how heavy is your unit ? (the gearing.. looks very robust, of course, at 5000Watt it should better be)


Ohh:
i will ride soon an old mountainbike, steelframe, no supspension
on big 26" SCHWALBE Big Apple Baloon-tieres
motor is a Suzhou Bafang 8Fun model SWX01
controller is the 24V version (cutoff at 17V) but it can handle up to 50V
i chose the 24V and not the 36V Version, because the controllers only differ in the cut-off-voltage, and so iam also able to use some of my rc-batts which have less than 36Volt
batteries: i first wanted to use 10s A123
but i already have some Sony Konion 1100 (18650-format)..
and 9s4p fit into the bottle, so i can hide 33,3V and 4,4Ah in the bottle

i have a distance of 12km to my flying field one direction
i will carry my heli and equidment with a little one-wheel-trailer

hope that the 33,3V and 4,4Ah are enough to give me some help over the hill i have to go...

 

[Kraeuterbutter]

just found in this thread on page three:

dirty_d wrote:

like this thing? this is pretty cool, it uses 2 motors and a planetary gear set to make a sort of motor/CVT unit. http://www.solomontechnologies.com/wheel.htm

by Drunkskunk on Fri Jun 06, 2008 12:14 pm

Exactly!

Fitting that in a bike hub and making it strong enough to survive what most of us put the bikes through would be a real feat, but should be possable.

maybe iam not understanding the concept..
but isn´t this already sold as an electric bike for over 10 years now ?
i mean the "Dolphine" (later named swissflyer, now again named Dolphine)

here the webpage:
http://www.velocity.ch/

some kind of planetary gear in the bikes rear hub...
on one side the power of the cyclist goes in
on the other side the power of the electric motor goes in..

variable gearing
so: you can for example go from 0 to 30km/h without shifting, pedaling all time with same rpm and nevertheless your power is added

 

[Miles]

Yes, same principle, that's why I wrote:

like this thing? this is pretty cool, it uses 2 motors and a planetary gear set to make a sort of motor/CVT unit. http://www.solomontechnologies.com/wheel.htm

Neat.

Similar idea to this: http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US5242335&F=0

 

[Kraeuterbutter]

hi..
oh.. i have overseen the link you posted...

its not only the same principle..
its the patent from KUTTER MICHAEL (CH)
look at this picture:

second person from left: Michael Kutter

 

[Miles]

Yes, the link that I posted was to Michael Kutter's patent. I've lost interest in it a bit because the pedal gearing changes so much depending on whether the motor isn't being used, or not.

There's also a similar epicyclic differential drive on the Prius. These things have been around for quite a while...

I like the idea of doing something similar with 2 RC motors

 

[dirty_d]

i think those resistance values must be wrong, the temperature coefficient of resistance for copper is 0.0039 so if say at 27 deg C that HXT motor is 0.032 ohms if the motor has been running for a while and it is 100 deg C, the resistance would be 0.032 * (1 + 0.0039 * (100.0 - 27.0)) = 0.041 ohms. with a 50A motor current limit the motor would be generating 102W of heat in the copper windings(at 0.041 ohms, 80W at 0.032), with a fan blowing air through the motor it would probably stay under 200F right?

one thing screwing up the efficiency numbers may be their posted no load current, they might only measure it at 10V or something, to accurately plot the motors performance you need the no-load current at the voltage you are plotting for.

 

[eP]

i think those resistance values must be wrong, the temperature coefficient of resistance for copper is 0.0039 so if say at 27 deg C that HXT motor is 0.032 ohms if the motor has been running for a while and it is 100 deg C, the resistance would be 0.032 * (1 + 0.0039 * (100.0 - 27.0)) = 0.041 ohms. with a 50A motor current limit the motor would be generating 102W of heat in the copper windings(at 0.041 ohms, 80W at 0.032), with a fan blowing air through the motor it would probably stay under 200F right?

You are overly optimistic at this point i'm sure.
For real motors warm resistance to cold resistance ratio is more than 2:1.
I suppose proximity effect is also involved for increasing warm resitance at high rpm.

one thing screwing up the efficiency numbers may be their posted no load current, they might only measure it at 10V or something, to accurately plot the motors performance you need the no-load current at the voltage you are plotting for.

It is the second important thing.
Third thing is mechanical loss. Bearing friction strong depend on balancing quality at 6000 rpm level IMHO.

Best regards

 

[dirty_d]

You are overly optimistic at this point i'm sure.
For real motors warm resistance to cold resistance ratio is more than 2:1.
I suppose proximity effect is also involved for increasing warm resitance at high rpm.

but why? do they use an alloy of copper or something with a higher thermal coefficient?

 

[eP]

You are overly optimistic at this point i'm sure.
For real motors warm resistance to cold resistance ratio is more than 2:1.
I suppose proximity effect is also involved for increasing warm resitance at high rpm.

but why? do they use an alloy of copper or something with a higher thermal coefficient?

Frankly speaking I don't know

But once again:

Lets look at TP5330 real datas:
http://myhobbycity.com/showthread.php?t=345&page=2

Kv = 254 rpm/V
Rm = 24.5 miliohms cold, at 1A
Rm = 63.4 miliohms at 70A, warm

That behaviour is not exceptional for outrunners.

Also i'm not sure what is valid range for copper linear temperature resistance coeficient.

For 50A level 2:1 ratio Rm_warm to Rm _cold is what you should expect IMHO.
If that ratio would be lower than 2:1, so Myhobbycity would claimed that already IMO. But now we still need someone brave and not poor to check that for all of us

Keep in mind: lower expectations = less disapointment :wink:

Best regards

 

[dirty_d]

well, either they made errors measuring the resistance, or the temperature of the motor "warm" is about 514°F. gotta follow the laws of physics. i dunno maybe there is something magic about a motor where the magnetic fields amplify the resistance increase due to temperature. but i think its more likely that they just made a mistake measuring the resistance.

 

[eP]

well, either they made errors measuring the resistance, or the temperature of the motor "warm" is about 514°F. gotta follow the laws of physics. i dunno maybe there is something magic about a motor where the magnetic fields amplify the resistance increase due to temperature. but i think its more likely that they just made a mistake measuring the resistance.

It is nothing magic, but high freq. magnetic fields are able to amplify resistance at all (not resistance increase ) by shinking conducting wire crossection. (skin effect, proximity effect ).

Rm_cold is typicaly measured at low RPM/ low magnetic field freq. , because at high rpm level the stator is hot so you can't measure Rm_cold that way.

So for high Rm_warm is also magnetic factor involved as you see.
(not only the temperature factor)

 

[The7]

It is known that the effective resistance an condcutor depends on many factors; such as magnetic field frequency (skin effect), magnetic field strength (Hall effect), temperature (temperature coefficient) and the wire construction (single/multi strands).

It is not clear how the Rm are determined or estimated at cold and at warm for these motors.
The change of Rm by a factor of 2 is seemed to be on the high side for an warm temperature (say < 100 deg C) and low motor frequency (say < 1000 Hz).

 

[eP]

It is not clear how the Rm are determined or estimated at cold and at warm for these motors.
The change of Rm by a factor of 2 is seemed to be on the high side for an warm temperature (say < 100 deg C) and low motor frequency (say < 1000 Hz).

But who said assumptions above are true indeed ? Maybe wire temperature is T=140'C and field freq is f=1200Hz ?

 

[dirty_d]

well, even using 64 mOhm instead of 32 mOhm for that HXT motor i still get a peak power @50A limit efficiency of about 85% as opposed to 90% for 32 mOhm. so thats still pretty good for like $100 less than the AXI motor. i bet if i plot the AXI motor using double the cold resistance i get something very close to 85% for the same conditions. the only thing thats uncertain is the no load current for each motor at 48V. does anyone have that 130Kv HXT motor?

 

[The7]

It is not clear how the Rm are determined or estimated at cold and at warm for these motors.
The change of Rm by a factor of 2 is seemed to be on the high side for an warm temperature (say < 100 deg C) and low motor frequency (say < 1000 Hz).

But who said assumptions above are true indeed ? Maybe wire temperature is T=140'C and field freq is f=1200Hz ?

" Prop selected (13x8 APC-E) was just the right one to draw 40A average. ...
.....Temperature was just 12C over the surrounding"

In all those tests, temperature elevation is not more than 25 C.
This shows that the temperature rise of the wire (< 100C) is justified.

The motor rpm is around 12000 rpm.
The motor frequency = 12000/60 x no of pole-pairs
= 200 Hz for 1 pole-pair
= 400 Hz for 2 pole-pairs
= 800 Hz for 4 pole-pairs.
For such a high rpm motor it is very seldom to have more than 4 pole-pairs. It seems that it is most likely with 2 pole-pairs.
For motor with iron core, it is not recommended to operate at frequency higher than 800 Hz.
Most aviation motors operate at 400/440 Hz.

 

[Kraeuterbutter]

Prop selected (13x8 APC-E) was just the right one to draw 40A average. ...
.....Temperature was just 12C over the surrounding

most likely the prop is giving some good airflow to the motor...
you have to considere this as well

oh: for the pol-pairs, how do you mean that ?

1 pol-pair is what ? a motor with 2 pols ? (like most inn-runners)
2 pol-pairs is a motor with 4 poles ?
4 pol-pairs --> 8 pol-motors

10 pol-motors for heli-use are sometimes spinning up to 20.000rpm
and then there are the 14pol-motors as well.. (up to 10.000rpm)

 

[eP]

" Prop selected (13x8 APC-E) was just the right one to draw 40A average. ...
.....Temperature was just 12C over the surrounding"

In all those tests, temperature elevation is not more than 25 C.
This shows that the temperature rise of the wire (< 100C) is justified.

Did you noticed that:

Essential motor parameters measured and calculated are:

Kv = 771 rpm

Rm = 0.050 ohms (50 milliohms) warm, at 45A
Rm = 26.5 miliohms, cold at 1A

Do you still insist wire's temperature is still below 100'C ?

The motor rpm is around 12000 rpm.
The motor frequency = 12000/60 x no of pole-pairs
= 200 Hz for 1 pole-pair
= 400 Hz for 2 pole-pairs
= 800 Hz for 4 pole-pairs.
For such a high rpm motor it is very seldom to have more than 4 pole-pairs. It seems that it is most likely with 2 pole-pairs.
For motor with iron core, it is not recommended to operate at frequency higher than 800 Hz.
Most aviation motors operate at 400/440 Hz.

The motor rpm @kv=130 U=48V is around 6000 rpm but pole pairs is mostly between 10 to 14 (depending on particular configuration ) for so large stator diameter D=70mm.

Best regards

 

[The7]

Look like we are making intelligent guess on temperaure and pole-pairs!

 

[eP]

Look like we are making intelligent guess on temperaure and pole-pairs!

You making a guess !
7 pole pairs is an absolute minimum for that size of diameter outrunner.
Isolated wires are much much warmer than motor's case.
For e-biking purposes case and wires would be even more hot at the same loads amps if the motor case will not be cooled by the same forced air flow.

 

[TylerDurden]

For e-biking purposes case and wires would be even more hot at the same loads amps if the motor case will not be cooled by the same forced air flow.

A small motor could be used just for cooling.

 

[eP]

For e-biking purposes case and wires would be even more hot at the same loads amps if the motor case will not be cooled by the same forced air flow.

A small motor could be used just for cooling.

It sound almost like double motors idea

But telling serious the best RC candidates for e-biking should be very efficient at load as light as possible. That way you can get high efficiency and low heat dissipation in one.

Maybe we should check quite new topology ideally suited for low rpm e-biking which as a bonus could be easy rearanged for RC purposes too.
I'm sure that idea is worth of deep study and investigation.
That is what I was looking for since more than year ago.
But that study direction is worth of his own thread.

http://endless-sphere.com/forums/viewtopic.php?f=7&t=4778


Best regards

 

[safe]

http://www.solomontechnologies.com

Revolutionary design

The Electric Wheel device is, in many ways, no different than these examples. Even electric motors have efficiency ranges and require transmission functions to allow efficient operation at slow speeds. These efficiency ranges are an inherent characteristic of all motors and engines. When used in transportation and other applications, they need the aid of a transmission to vary output. The revolutionary difference with the Electric Wheel is that it performs the transmission function with a minimum number of parts and when the transmission function is no longer needed, the frictional losses (heat and wear) are eliminated. This is accomplished by actually rotating the entire transmission inside the motor and with the motor when it is no longer needed. This is all possible because within the Electric Wheel both the sun gear and the ring gear of the planetary gear set are powered.

This method of operation offers a very important benefit of the Electric Wheel; it can operate with one electric motor disabled, or half of its parts. It can also operate with full power with the gear set fused together. These important benefits make the Electric Wheel like no other device - an entirely redundant propulsion system that is totally self-contained. It is for these reasons that NASA has called the Electric Wheel "the propulsion system for the next millennium." The Rocky Mountain Institute has stated: "the most elegant and simplest example of an engine on the planet."

The patent was granted such that "at least one of the inputs being of electrical power". This is to say that the Electric Wheel can derive its second input power from a source other than electric. It could have an electric ring and hydraulic sun, or steam ring and an electric sun or an electric ring and fossil fuel sun, or any combination. It could also have multiple electric technologies combined, for example an AC motor sun and DC motor ring. More importantly, it allows for the motor technology to be employed that is most appropriate for the specific platform needs.

My Comment:

Apparently they have a design that is similiar to that of a multiple gear internal rear hub. The plantary shell layer allows what appears to be either a two or a variable transmission somehow.

This still looks too heavy though... we need to be reminded that the core idea about the RC motor was weight. The "Big Iron" hub motors can already do the job of power today, but they come with as much as 25 lbs of iron and realistically no one will every be doing mountain bike trick riding or racing with 25 lbs of unsprung weight.

So (in my opinion) the RC motor is still the right way to go...

 

[eP]

The "Big Iron" hub motors can already do the job of power today, but they come with as much as 25 lbs of iron and realistically no one will every be doing mountain bike trick riding or racing with 25 lbs of unsprung weight.

So (in my opinion) the RC motor is still the right way to go...[/color]

But still the problem nr 1 is classic outrunners 50+ mm in stator diameter
are still reserved for very very small high power niche. As a result the best of them are really expensive and others (cheap ) are relatively inefficient especially at low load.

I still wonder why nobody want discuss different topologies advantages for e-biking purposes ?