at what point is gearing no longer helpful?

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for sprinting around town up to 40mph with a couple hills.

in my mind it can only be a plus and the bigger the gear ratio the better. the current used to spin the motor at full speed upside down with no load is very small. i feel like i should be maybe choosing the motor kv by the biggest gearing i can fit.

i tried to do some simulations on the grin tool, which is awesome, but it's too much coming up with hypothetical inductances and resistances for custom motors. im sure easy math for many. and then there's other hurdles so im here asking.

tell me where I'm wrong:
ideal is to run a motor at an rpm which will have an equal amount of heat produced from the copper as the iron. that seems a way off distant speed compared to the few amps i see when i run the motor full speed with no load. that is the sum of the iron losses as I understand it so i should be running the motor maybe 3 times faster or something till the iron losses are coming up to something substantal? ideal would be to run the motor within some rpm range based on the copper losses and iron as i said and would depend on how hard the motor is driven still, but if the motor is driven harder especially, with stop and fast go, the bigger gearing and maybe even sinking strangely into having higher iron losses for a change. that would be a good race machine. with giant gearing, no? besides being lightest and getting the best range and efficiency, no?

with a chain or belt drive doing jackshafts are efficient and can do them through these awesome things as the jackshaft.https://sickbikeparts.com/cranks-freewheel-isis-crank-set/

and using with two chainrings or possibly pulleys using this on the cranks. http://sickbikeparts.com/front-freewheel-heavy-duty/

and then can pedal if you need to and have a jackshaft all integrated into one! i just have to see what gearing i can fit.



am i wasting my time trying to gear the crap out of some motor like this with a high kv https://www.altitudehobbies.com/collections/80mm-series/products/leopard-8072-11t-160kv-brushless-airplane-motor
and did you see it in his hand? did you see how cute it was? just look at it. just look at it.

and will this kind of motor with the bell not so supported, will the road bumps kill it? maybe theres another motor more suited you know?!!?

i plan to use all standard bike parts. aluminum 50t sprocket on the back i think i saw is out there. on a hopefully steel splined freehub body in a mountain bike rear hub.

eventually the small teeth cogs become inefficient when so small, Id like to avoid that but i see some tiny motor cogs out there. pulleys i think have to be larger. was hoping to do a pulleys and a belt coming off the motor, to be quieter, but maybe the two chains is way easier and then i can get that big gear ratio.

they make a double and then you can get a 16 or 17 tooth, and thinking maybe welding a pulley to the other side so then can have this instead of the mounting hole plate above which takes a 24 tooth minimum.
was thinking of getting the outer part of the freewheel custom made, white industries said id have to get 100s of course, but im sure i could get a couple cheap in china. make it a lot simpler. or maybe theres another better way to go about doing this?

and weld a slotted motor mount plate to the frame, or get another frame made with some other modifications. cheap steel. low bottom bracket. wide stance, 24" wheels, front suspension.
 
I am going to CUT and PASTE the rest of this post. From random references online. Related. Have fun, learn lots. YOU are on the right path, track. Trajectory. School of thought.

May be it is rocket science, maybe it is not. IDK. How smart are rockets anyway. Dumb things. Like a motorcycle, only as good as the rubber technology, for the speed you put down...

The rocket is only as smart as the technology allows. Lol. I think we are limited by the tension in certain chains available, and the forces within, for our applications. We have small chains. Bicycle sprockets can only transfer so much force before th damage with fatigue.

Ok that is all. End meaningless rant.


Cut and Paste: but I think you know all of this already. The mathematical equations of physics are very.. straight forward.



Mechanical advantage, also called force ratio, is the ratio of the output force (load) of a machine to the input force (effort). In the case of an ideal (frictionless and weightless) machine, mechanical advantage = velocity ratio.

Tractive effort : the force in pounds exerted by powered equipment (as a locomotive) as measured for statistical purposes at the rim of the driving wheels.

As used in mechanical engineering, the term tractive force can either refer to the total traction a vehicle exerts on a surface, or the amount of the total traction that is parallel to the direction of motion

A machine is a device that can change the magnitude and line of the action of force.

Newton's second law, which states that the force F acting on a body is equal to the mass m of the body multiplied by the acceleration a of its centre of mass, F = ma, is the basic equation of motion in classical mechanics.

The thrust-to-weight ratio can be calculated by dividing the thrust (in SI units – in newtons) by the weight (in newtons) of the engine or vehicle and is a dimensionless quantity. The thrust-to-weight ratio can be calculated by dividing the thrust (in SI units – in newtons) by the weight (in newtons) of the engine or vehicle and is a dimensionless quantity. Note that the thrust can also be measured in pound-force (lbf) provided the weight is measured in pounds (lb); the division of these two values still gives the numerically correct thrust-to-weight ratio. For valid comparison of the initial thrust-to-weight ratio of two or more engines or vehicles, thrust must be measured under controlled conditions.

Power-to-weight ratio (PWR) (also called specific power, or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power source. It is also used as a measurement of performance of a vehicle as a whole, with the engine's power output being divided by the weight (or mass) of the vehicle, to give a metric that is independent of the vehicle's size. Power-to-weight is often quoted by manufacturers at the peak value, but the actual value may vary in use and variations will affect performance.

The inverse of power-to-weight, weight-to-power ratio (power loading) is a calculation commonly applied to aircraft, cars, and vehicles in general, to enable the comparison of one vehicle's performance to another. Power-to-weight ratio is equal to thrust per unit mass multiplied by the velocity of any vehicle.

Starting tractive effort: Starting tractive effort is the tractive force that can be generated at a standstill. This figure is important on railways because it determines the maximum train weight that a locomotive can set into motion.

Maximum tractive effort: Maximum tractive effort is defined as the highest tractive force that can be generated under any condition that is not injurious to the vehicle or machine. In most cases, maximum tractive effort is developed at low speed and may be the same as the starting tractive effort.

Continuous tractive effort: Continuous tractive effort is the tractive force that can be maintained indefinitely, as distinct from the higher tractive effort that can be maintained for a limited period of time before the power transmission system overheats. Due to the relationship between power (P), velocity (v) and force (F), described as:

P = v F or P v = F

Tractive effort inversely varies with speed at any given level of available power. Continuous tractive effort is often shown in graph form at a range of speeds as part of a tractive effort curve.
 
Hummina Shadeeba said:
for sprinting around town up to 40mph with a couple hills.

If you have enough power to ride around at 40 mph without aero aids, and reach that speed in a reasonable time, then climbing hills in most kinds of terrain won't be a factor.

Let us know if there are complications getting your motorcycle registered and insured.
 
Chalo said:
Hummina Shadeeba said:
for sprinting around town up to 40mph with a couple hills.

If you have enough power to ride around at 40 mph without aero aids, and reach that speed in a reasonable time, then climbing hills in most kinds of terrain won't be a factor.

Let us know if there are complications getting your motorcycle registered and insured.

I’m not going to be getting into those complications and thought most here don’t. I keep it under wraps and don’t kill myself

But I’m still in the dark as to at what point gearing is an advantage. Am I wrong in believing the most efficient way to run the motor is fast enough that half the losses are iron? Otherwise, as seems much more common, the majority of heat produced is copper losses, which could be lower with more gearing.

The front freewheel cranks are awesome in being able to add both a jackshaft and the ability to pedal if needed and all through the standard bottom bracket. Then can just use a chain or belt to increase the gear ratio. But how much do I want to do that?! Sure I need to have the kv and voltage result in an ideal top speed but if I can chose that kv and the gearing,... .. im believing I should be spinning the motor much faster for efficiency and performance no?

the ultimate would be if I could also find a mountain bike rear swing arm that uses the bottom bracket as the pivot point as well so as to keep the single speed chain taught while the rear flexes. And I’d get the frame made. Or would you not need to pivot there necessarily and I won’t lose my single speed chain? a lot of rear suspension dont pivot off the bb...but they’re not single speeds without a spring tensioner. So maybe just do rigid rear, but would be super slick with dual suspension so what you think?
 
Having multiple gears would make sense for a faired HPV or velomobile, because those don't take nearly as much power to attain high speeds as a regular bike does. It doesn't make as much sense for a regular bike, because if you have enough power to go fast, you also have enough power to climb steeply or accelerate quickly.

The one exception I can think of is a case where you have long uninterrupted climbs, like mountain passes, and your high-geared bike could run in an inefficient speed range for long enough to overheat it. In that case it might be worthwhile to have a shorter gear available so the motor can do long accents in an efficient speed range and/or at a lower power level.
 
It would be single speed. A giant gear for everything paired with a high kv as well.

But what of my fundamental understanding of how to run the motor in the most efficient rpm? I always see iron losses (seen while doing no-load at top speed) that are barely anything compared to the copper losses in use. The current drawn I see at full speed with no load...I increase that by adding gearing, which isn’t good in itself, but it will subsequently reduce the copper losses in use due to the massive gearing. I trade one for the other till a balance in how I ride is achieved and THAT is the most efficient way to run the motor, no?

For someone who takes it easy on the throttle and isn’t always sprinting a smaller gearing would result in greater range and vise versa.
 
It's most efficient to gear an EV motor so the vehicle reaches the desired top speed and no more than that. Having excess top speed available reduces efficiency in the normal operating speed range.
 
Chalo said:
It's most efficient to gear an EV motor so the vehicle reaches the desired top speed and no more than that. Having excess top speed available reduces efficiency in the normal operating speed range.

Yes, but I can alter the gearing and kv so can have that same top speed but greater motor rpm. What’s the most efficient motor rpm?
 
Hummina Shadeeba said:
Chalo said:
It's most efficient to gear an EV motor so the vehicle reaches the desired top speed and no more than that. Having excess top speed available reduces efficiency in the normal operating speed range.

Yes, but I can alter the gearing and kv so can have that same top speed but greater motor rpm. What’s the most efficient motor rpm?

I don't know how to determine motor peak efficiency RPM, but I know it varies between different motors. You can't go far wrong by sticking reasonably close to manufacturer ratings.

I prefer to specify motor winding and battery voltage to give me the RPM I'm looking for, because there are drawbacks to gearing. Having any external reduction gearing at all adds bulk, wear, maintenance, points of failure, and pinch points to a bike. If your layout requires gearing, it's best to keep chain wrap angles and sprocket sizes generous for improved wear and reduced noise. Doing that reduces your choices of reduction ratio.
 
I’m pretty sure peak efficiency would be at a high enough rpm that the iron losses match the copper. In use moment by moment it will vary of course but overall this is the goal. Hoping someone can confirm this as that’s the whole point in my doing the big gearing w mid-drive using a jackshaft as apposed to simple hub motors.

Not the simplicity and lack of maintenance of a hub motor but the benefits of being lighter, having better hot rod performance, and better range seem worth it.

The huge weight of the hub is also a real handling downer I’ve come to find. Looking forward to a super light back wheel that doesn’t fly around with every bump and instead has just one big cog.


I forget what erpm the vesc6 or other escs can do but I’m betting way more than any hub motor does and it’s an untapped source of power. Add more speed in the torque x speed equation.
 
This question as to what erpm the motor should spin for best efficiency is fundamental in understanding how to run a motor. It’s the mid-drive section..surely someone can answer this :es: r maybe I should ask in motor section

I can imagine over gearing the motor and ending up heavier in iron losses with the purpose of putting less heat on the winding so the motor lasts longer, or reducing mechanical stress for some parts. Maybe.

Maybe the iron losses and its heat produced would be more easily rid from a typical outrunner or other motor, a possible reason to run iron loss heavy.






Copper losses are a simple loss in heat but iron losses are both a loss to heat as well as a mechanical resistance right? What percent?


Are iron losses as simple as being erpm dependent and what I see on my no-load current draw at such and such erpm is the whole story, or is the stator magnetic field and higher current going to create higher eddies and hysteresis even before it saturates?

How can I figure at what current saturation is happening?
 
I mean, you are getting this complicated, this goes on forever: Since the dawn of brushless RC,....

Timing has been adjusted and tried, the Hz of PWM is adjusted, Erpm of processor been adjusted, the heat has been monitored, the adjustments recorded. How this (winding) or that ( wound, winding) motor reacts to any particular setup is very specific to that combination, as seen in RC hobby and VESC programming.=, for example. What is the efficiency? What is the actual losses?

Some say they run better hot, at the edge, with alot of timing. One motor may, one motor may not.

Some do not know the effects of timing. Advance, Retard. Some do not understand a three phase bridge with legs line to line. Running the PWM.. and the difference in timing actuation... All this contributes to a certain combo, and the heat/power relationship, I think.

YOu must specify the motor, winding, type of commutation for another analysis, more specific, in my opinion. THere are soooo many magnet and winding configurations it is very hard to make assumption and take data from that, generally.
 
If u want to adjust the timing or frequency or winding ok and it is still copper and iron losses being compared in the end and how much of each is ideal.

Isn’t a motor most efficient when running half copper and half iron losses?
 
Hummina Shadeeba said:
If u want to adjust the timing or frequency or winding ok and it is still copper and iron losses being compared in the end and how much of each is ideal.

Isn’t a motor most efficient when running half copper and half iron losses?


Justin did a video on just that.
Lemme see what comes up. I think I know the vid, mostly white thumbnail
https://www.youtube.com/watch?v=dxJe_gygRGU
Talks about just that, copper and iron losses and playing the efficiency game.
 
Chalo said:
Hummina Shadeeba said:
for sprinting around town up to 40mph with a couple hills.

If you have enough power to ride around at 40 mph without aero aids, and reach that speed in a reasonable time, then climbing hills in most kinds of terrain won't be a factor.

Let us know if there are complications getting your motorcycle registered and insured.

Agree, I have 40mph top speed on my 6kw hub bike. Torque isn't an issue, wheelies until 15mph.
 
markz said:
Hummina Shadeeba said:
If u want to adjust the timing or frequency or winding ok and it is still copper and iron losses being compared in the end and how much of each is ideal.

Isn’t a motor most efficient when running half copper and half iron losses?


Justin did a video on just that.
Lemme see what comes up. I think I know the vid, mostly white thumbnail
https://www.youtube.com/watch?v=dxJe_gygRGU
Talks about just that, copper and iron losses and playing the efficiency game.

thanks just what i was looking for. at an hour in:
"it turns out max efficiency is when core losses are exactly the same as copper losses"
and explaining goes on from there. All hub motors I’ve been involved with are heavily lopsided into copper losses.
 
Well I couldn't remember the time where he talked about it, I just remembered that he did talk about, but its pretty easy to find if you speed up the play speed or just skip ahead using the mouse cursor on vid-time every so often.

Here's another which might interest you if you go through it.
https://www.youtube.com/watch?v=c96n0Ma2rLY
@36:07 will interest you
@1:49


Hummina Shadeeba said:
thanks just what i was looking for. at an hour in:
"it turns out max efficiency is when core losses are exactly the same as copper losses"
and explaining goes on from there. All hub motors I’ve been involved with are heavily lopsided into copper losses.
 
markz said:
Well I couldn't remember the time where he talked about it, I just remembered that he did talk about, but its pretty easy to find if you speed up the play speed or just skip ahead using the mouse cursor on vid-time every so often.

Here's another which might interest you if you go through it.
https://www.youtube.com/watch?v=c96n0Ma2rLY
@36:07 will interest you
@1:49


Hummina Shadeeba said:
thanks just what i was looking for. at an hour in:
"it turns out max efficiency is when core losses are exactly the same as copper losses"
and explaining goes on from there. All hub motors I’ve been involved with are heavily lopsided into copper losses.

Great vids. At 1:26 it shows how the motor output power could be up to 4x more with higher rpms.
 
I wish he'd do more video's, talk more about what he wanted to talk about but couldnt in one of the videos, at the end, with all the questions asked and answered.

Hummina Shadeeba said:
Great vids. At 1:26 it shows how the motor output power could be up to 4x more with higher rpms.
 
Something like this with .15mm lams maybe is capable of a lot more speed and power for the same heat produced. https://ant-innovator.myshopify.com/products/ant-innovation-at-83100-9-5kw-brushless-motor-with-watercooling-system-for-electric-jetboard-sensored-outrunner-bldc-motor

How can I figure at what point the eddy currents start to overcome the copper losses? Anyone good at the grin simulator and bet it can figure it.

It shows the “idle current” above, which I assume is the no-load current, but it doesn’t specify for what rpm.

Places offer many kv for a specific motor and people will chose the one that most suits their application’s gearing..but if your gearing isn’t an obstacle and you can do whatever, there’s going to be an rpm that will be most suited to the amount current you’re putting out. That’s what I’m trying to figure

markz said:
I wish he'd do more video's, talk more about
[/quote]
I like the vids a lot. I was hoping he’d specifically do a comparison showing the same motor doing different speed abs how that effects heat n power.


R there’s this

https://endless-sphere.com/forums/viewtopic.php?t=100461
 
Hummina Shadeeba said:
Places offer many kv for a specific motor and people will chose the one that most suits their application’s gearing..but if your gearing isn’t an obstacle and you can do whatever, there’s going to be an rpm that will be most suited to the amount current you’re putting out. That’s what I’m trying to figure

Gearing is always an obstacle. You can't do whatever. When you're talking about multi-stage reductions or harmonic drives, like you'd need if you're running most motors so fast that iron losses equal resistance losses, then you'll lose more efficiency in the gear reduction than you stand to gain by running the motor at utmost efficiency. That's apart from the weight, bulk, noise, maintenance, cost, and points of failure that you add when you use deep gearing reductions.
 
Chalo said:
Hummina Shadeeba said:
Places offer many kv for a specific motor and people will chose the one that most suits their application’s gearing..but if your gearing isn’t an obstacle and you can do whatever, there’s going to be an rpm that will be most suited to the amount current you’re putting out. That’s what I’m trying to figure

Gearing is always an obstacle. You can't do whatever. When you're talking about multi-stage reductions or harmonic drives, like you'd need if you're running most motors so fast that iron losses equal resistance losses, then you'll lose more efficiency in the gear reduction than you stand to gain by running the motor at utmost efficiency. That's apart from the weight, bulk, noise, maintenance, cost, and points of failure that you add when you use deep gearing reductions.

gearing is an obstacle but doesn’t have to be inefficient. chains and belts are very efficient. As the motor and gearing does more speed inefficiency will go up but still seems very worth it.

you think this will destroy a freehub?:
https://www.performancebike.com/wolf-tooth-components-wolfcage-combo-pack-49t-cog-18t-cog-derailleur-cage-gc49-blk-kit/p-fqyvh4hczuargqhe

im trying to get a large bike cog made, maybe 50 tooth, that will fit in the back with this:
https://www.jensonusa.com/Problem-Solver-Singlespeed-Cog-Car
https://www.walmart.com/ip/STEBCECE-MTB-Cassette-Single-Speed-Cog-Gear-16T-17T-18T-19T-20T-21T-22T-23T-Freewheel/845304599?selected=true

Or maybe I can integrate both those already made parts and reduce stress in the freehub body


On the front, with the freewheel cranks, im planning on getting the white industries double freewheel with both 17 and 19 teeth, and ill use the 17 tooth for the chain going to the rear wheel, and weld a big pulley to the 19 tooth side or maybe some other way to connect if you have an idea. ( a friend said he could weld it but havent gone through the details with him or figured exactly where would connect.) http://www.whiteind.com/wifreewheel

and have to figure what size pulley will fit, and dont want it dragging on the ground but from what i remember before i could get a 1:3 ratio with a very reasonable sized driven pulley. so maybe would end up with like a 10:1 ratio. tell me if im wrong but regardless of an efficiency goal...if im able to spin the motor faster and convert that to torque im going to be able to gain a lot of power while still keeping within my esc's 90 amp limit. torque and speed with minimal heat.


https://cdn.shopify.com/s/files/1/0076/7098/8859/files/8072_new_chart.pdf?159
looking here its not clear exactly how many rpms its doing at 2.8 amps no-load...but ill need to spin this motor wayyy faster to get the iron losses close to the copper. i imagine it would fly apart. the losses of the drive system will greatly increase with the speed but still. hasnt anyone done some giant gearing here on :es: before?

Will use 24” wheels and suspension
 
I believe a 16t sprocket can bolt to a 104bcd chainring if I remember correctly.

I think you should look at the single speed and left hand drive setups that people are doing with the CYC X1 Pro.
 
Grantmac said:
I believe a 16t sprocket can bolt to a 104bcd chainring if I remember correctly.

The teeth of a 16t chainring are at approximately 64mm BCD. That's a common 4-bolt inner ring size.
 
Grantmac said:
I believe a 16t sprocket can bolt to a 104bcd chainring if I remember correctly.

I think you should look at the single speed and left hand drive setups that people are doing with the CYC X1 Pro.

Looks awesome. 6:1 gear ratio. The bafang ultra is a huge 18:1

I’m going to save a huge amount of time and likely money and get one of these instead.


Any advice on a frame to go with the bafang ultra? Isn’t there a frame with the motor mount already installed?
 
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