Geared Motors

[Mono]

This is how the future EUC motor may well look like: a geared hub motor without clutch. This can probably shave off 3-5kg without affecting the specs.

[Ro.man]

Yes, and the torque will be insane. 

Spoked wheel will also be lighter and easier to fix. 

I wonder if the mobo will work with geared motor, anybody tried that?

[supercurio]

I'm not sold on the noise tho.

[Ro.man]

MAC/GMAC is very quiet, there are other geared hubs that are noizy though 

[Mrd777]

I used to build e bikes almost 10 years ago with these Mac motors.  They are truly amazing motors, and the weight to power didn't compare to the hub motors. They are a bit louder than hubs,(but hardly) however I favored them. Mac sold them with different gear "numbers" if you wanted a high torque or high speed.  The nylon gears do eventually wear, however I never had to service or replace mine.  These would be brilliant on our EUC's !

Edited September 23, 2021 by Mrd777

[mrelwood]

Geared motor on an EUC brings memories to many long time riders. RockWheel used some kind of gearing system in the GR16 back in the day, a few millennia ago… I don’t think it was all that successful.

Edited September 23, 2021 by mrelwood

[RockyTop]

1 hour ago, mrelwood said:

Geared motor on an EUC brings memories to many long time riders. RockWheel used some kind of gearing system in the GR16 back in the day, a few millennia ago… I don’t think it was all that successful.

I can’t imagine it would be. If you want more torque a bigger diameter, wider motor with more steps / fields makes more sense. Gears are just something to go wrong. 

[RayRay]

Solved: 

Up the voltage and motor power. (Worked so far...)

What could go wrong?

(Go!) 

[supercurio]

2 hours ago, RockyTop said:

I can’t imagine it would be. If you want more torque a bigger diameter, wider motor with more steps / fields makes more sense. Gears are just something to go wrong. 

Not having much experience with BLDC motor design, I was wondering about that.

Simply put, what are be the benefits of geared motors compared to building a hub motor with the right Kv for the application.
Is it because a wheel at zero or very low rpm can always get more torque from a geared motor than a hub motor - both systems being tuned for the same no-load speed?

[RockyTop]

5 minutes ago, supercurio said:

Not having much experience with BLDC motor design, I was wondering about that.

Simply put, what are be the benefits of geared motors compared to building a hub motor with the right Kv for the application.
Is it because a wheel at zero or very low rpm can always get more torque from a geared motor than a hub motor - both systems being tuned for the same no-load speed?

We use geared motors when physical limitations are to great or when it is cheaper and easier. 
 

Take elevators (lifts) for example: (simplified)

 They have geared and gearless motor configurations. Both systems work. The gearless motors are much larger in diameter. Even then they take advantage of a 2:1 pulley configuration to work. They are smooth and fast, best fitted for 10 -100 floors. Best suited for passenger use. They could work in a 1:1 construction yet the motor would have to be ridiculously large. As they are some older gearless motors are 8 feet tall. So why do they have geared elevators? …. The answer is money and space.  Most elevators less than ten floors are geared. They are slow cheap and can lift heavy weight. They are less complicated electronically because they are not controlled by every field and pulse that passes by in the motor. The geared motors basically just ramp up power then ramp back down. Simple cheap. Let the gear resistance do the rest. 
 

Disclaimer: The above refers to most elevators. Some geared elevators are roped 2:1. Some elevators are 4:1. Or even more. A recent change from cables to belts allows for smaller drive shivs. This allows for less movement per motor RPM effectively blowing old rules away.= smaller motors.  Old rules: gearless 2:1 gearbox is usually around 40:1 

[RagingGrandpa]

1 hour ago, supercurio said:

what are be the benefits <and drawbacks> of geared motors compared to building a hub motor

For single-fixed-ratio gearing, which I think you're discussing here:

• Speeding up the output gives less torque.
  An HT motor like Gotway C38, plus gearing, could spin as faster as the Sherman, but it would also produce less wheel torque (like Sherman).
  If you're willing to trade torque for speed, better to keep it simple and reduce turns (less copper) or reduce flux (smaller magnets). Which is what the EUC designers do today.
   
• Slowing down the output slows down the EUC.
  You could use the Sherman motor to get the HT motor's wheel torque, but the EUC would also become slow (like the HT motor).
  I think we have plenty of torque from the HT EUC designs today, so I doubt this is helpful.
   

1 hour ago, RockyTop said:

We use <single-ratio> geared motors when physical limitations are to great or when it is cheaper and easier. 

Great point.

For EUC's, we seem to have found a motor type that fits nicely inside the machine, so no need for gearing.

 

*multi-ratio* gearing would allow you to move your peak-power speed up and down, expanding the speed range of the machine. This is certainly desirable... but a multi-speed transmission is a complex thing, made even more challenging because self-balancing EUCs would require it to shift without a neutral position. Better to expand the speed range of today's BLDC motor through increasing input voltage (126V etc), or flux weakening (electrical, or mechanical).

EUC's (non-suspension models at least) are an especially elegant design, because there is only one moving part. This permits lower cost, lower weight, durable designs. I think the best way to continue along this path is higher voltage, or non-permanent-magnet motor types.

.02

Edited September 23, 2021 by RagingGrandpa

[Tawpie]

I also wonder about gear lash and how much precision is required of the mechanics to keep it from being a thing. Maybe hydrostatic 'gearing'? (nah, we still want speed don't we!)

Edited September 23, 2021 by Tawpie

[RockyTop]

14 minutes ago, Tawpie said:

I also wonder about gear lash and how much precision is required of the mechanics to keep it from being a thing. Maybe hydrostatic 'gearing'? (nah, we still want speed don't we!)

Good point. one set of gears would not be so bad but it would likely be noticeable. The floating could be unnerving. floating-prolonged time without positive or negative pressure on the gear.  

[Eucner]

Gears will always lower wheels efficiency, so less miles from the battery.

[Planemo]

I wouldn't want to use a geared motor in an EUC due to reliability. I have used geared hub motors in ebikes before and whilst generally reliable, they also aren't used to taking anything like the same repetitive forward/back axle stresses we get on EUC's. The planetary gears (nearly always plastic) can fail even on bicycles and quite honestly I want moving parts in an EUC to be kept to an absolute minimum when any loss of balance means bad news. As with anything, I am sure a reliable geared motor could be produced but at what cost and the makers of our wheels aren't known for going overboard with engineering quality.

[mhpr262]

22 hours ago, supercurio said:

Simply put, what are be the benefits of geared motors compared to building a hub motor with the right Kv for the application.
 

Electric motors can be built to a huge range of specifications, but what electric motors generally love best is spinning at insane RPMs and light loads. That is what usually allows you wring out the best performance and efficiency numbers and the best power-to-weight/size ratio out of an electric motor (as long as you can get the cooling figured out). 

I fly electric RC planes, and even in the day and age of hugely torquey outrunner motors the very highest end performance electric gliders are powered by inrunner motors with a 6.7:1 planetary gearbox attached. Those things spin gigantic 22'' folding propellers for maximum climbing efficiency.

[Ro.man]

You don't have to use nylon gears, steel and composite gears are available and they are much more durable. Of course they are a bit louder, but I wouldn't mind having a better climbing torque at low speeds accompanied with a sound of a motor. 

My S18 is not silent in such conditions and I can feel how it struggle on those steep uphill trails.

Edited October 6, 2021 by Ro.man

[RayRay]

On 9/23/2021 at 9:10 AM, RayRay said:

Up the voltage and motor power. (Worked so far...)

What could go wrong?

I am sad this thread died because I hoped someone would mention that adding more power usually adds more weight.

All the wheels coming out in 2022 are over 75lbs (so far); and, if this trend continues, could soon surpass 100+ lbs.

Since it takes more batteries (in series) to reach a higher voltage, I think at some point this strategy needs to give...

(How heavy is too heavy?)

Edited February 9, 2022 by RayRay

[Funky]

33 minutes ago, RayRay said:

I am sad this thread died because I hoped someone would mention that adding more power usually adds more weight.

All the wheels coming out in 2022 are over 75lbs (so far); and, if this trend continues, could soon surpass 100+ lbs.

Since it takes more batteries (in series) to reach a higher voltage, I think at some point this strategy needs to give...

(How heavy is too heavy?)

For me over 30kg (66lbs) Are to heavy, at that point beats the purpose of euc in my eyes. That are light enough to carry in train and 2/3 floor house.

If people don't need to carry them at all, i see appeal of heavy powerful wheels.

And most people. (Talking about regular "Joe") Buys something small, fast enough, lightweight.. Around or less 20kg(44lbs). For small city runs etc. And if they get hooked on, they most likely will buy another wheel later..

Companies need to start releasing "second round" of new lightweight wheels.. As they provide more income regularly.

Nowadays it's all about who has the biggest DuCK contest..

Edited February 9, 2022 by Funky

[Tawpie]

15 minutes ago, Funky said:

Companies need to start releasing "second round" of new lightweight wheels

And if gear lash and transmission reliability can be solved, perhaps a geared motor is a way to get zippy and light and small out of a small battery? I'm thinking something I can toss my eBike battery on... maybe with a CVT in the hub so it has torque and a bit of speed? I have no idea how to make such a CVT that'll go both directions, but uni-directional designs are starting to show up in the ebike world.

[Boris Lämpel]

I think it is possible that we will see a continously variable transmission in EUCs.

The concept could be like Nuvinci (ebike) but has to last higher torque than nowadays.

 

[tst]

Geared is probably at the moment technically the best.

Electric motors like spinning fast. So this will make for low weight and high torque.

Manufactured to high specs, high quality metal gears they won't fail. The reason ebike gears fail is because it's a cost issue. Low weight helps with manouvering. It'll be a agile wheel with insane acceleration and uphill capabilities.

But why would they go through the hassle of building this if people accept and buy heavy 30 kg wheels?

I think lightweight and high torque is the right way forward for the future. For mainstream usage that is. Speed is only nice for people willing to take high risks. More countries are putting in restrictions because there's just to many people coming in with face injuries. It's be a long way before euc's are as safe as motorcycles with their bigger wheels and physical stability. Though the euc diehards will of course deny this. They are a small group but make the most noise.

Here you see a 1000w (40 gram weight) drone motor powering a bike. This is an extreme, and will fail by lack of cooling. But it shows that euc motors are way heavier than needed.

 

[RagingGrandpa]

On 10/1/2022 at 6:20 AM, tst said:

euc motors are way heavier than needed

The manufacturers aren't dumb... 

I think the benefits of today's layout were covered nicely above:

On 9/23/2021 at 2:39 PM, RagingGrandpa said:

On 9/23/2021 at 2:36 PM, RockyTop said:

We use <single-ratio> geared motors when physical limitations are too great, or when it is cheaper and easier. 

Great point.

For EUC's, we seem to have found a motor type that fits nicely inside the machine, so no need for gearing.