Thanks Flecc for putting it into laymans terms

 

Unfortunately, I am still struggling to envisage it. I havent had enough experience of gearing to understand this I think.

 

Let me give it a try...

 

The Sun turns the fastest, it in turn turns the planets slower, which in turn turns the Annulus even slower. So you would have 3 other cogs connected to these, is that right?

 

Thanks

No John, the Sun is part of the spindle, fixed to the frame, so is stationary at all times.

 

The three planet gears surround the sun and are engaged with it.

 

Around the whole is the circle of the annulus gear, it's teeth engaging with the planet gears.

 

Now if that annulus around the outside is rotated (by a drive from the sprocket) around the whole, the planets are forced to rotate, since they are engaged with the stationary sun, and have to roll around it.

 

As those planets revolve around the sun, they and the ring cage they are mounted on are trailing along after the outer annulus as it turns.

 

As that planet ring is travelling slower, we connect it to the wheel, so the bike wheel is now revolving slower than the sprocket. Therefore it's geared down, so that's low gear.

 

If we reverse that and connect the sprocket to the planets instead, turning them around, they revolve around the stationary sun again and carry the outer annulus around, this now travelling faster.

 

Therefore we connect the outer annulus to the bike wheel, making that revolve faster than the sprocket, therefore geared up, so it's high gear.

 

To understand gearing in general, think of the bike chainwheel and rear sprocket. Turn the large chainwheel once, and the small sprocket has to turn several times. That's a high gearing, gearing up for more turns out.

 

If you do the reverse and turn the small sprocket, you'll have to turn the sprocket several times to turn the chainwheel once, that's a low gearing, gearing down for less turns out.

 

Although it's more complicated to understand, that's all that's happening in an epicyclic, the sun in the middle is small, the outer annulus ring is large, so different ratios exist between them, the direction of the drive applied determining whether it's geared up or down.

.

Edited July 22, 200718 yr by flecc

3 Speed Hubs

 

Further to Fleccs comprehensive description above this page gives an excellent description and cutaway diagram of the old Sturmey Archer 3 speeds, on which others are modeled.

Edited July 22, 200718 yr by Ian

Gearing in a Hub Motor

 

Hello Flecc:

re your last two posts on this subject (unless you are posting another as I type).

I understand the principles of the three gears that you expound.

My question is: "How do you propose to change between one gear and another?"

Just an aside: I would hope to get a top ratio between the present Torq gearing and Sprint gearing. A low gear lower than the Sprint (I'm old and feeble and like to rest often before I reach the top of a long hill) and a high gear lower than a Torq (I don't need 23 mph - at least not at the expense of battery range).

Say, something that would climb 14% at 5 mph (unassisted) with a pay load of 125 kgs and cruise at 16 mph on the flat in high gear. Middle could be used for intermediate hills. Lots of lovely torque.

It would be a shame to lose these conclusions to an academic experiment.

Thank you Flecc

Peter

Here you go: Rohloff - How it works

To Peter

 

For external change control in normal hub gear fashion Peter, the spindle hollow on the opposite side to the cable (the gear side) with an actuator rod. No point in details before determining which elements to choose in the gearing. Either a rotating sun driving the planets for a lower gear, plus direct drive, or a driven free annulus driving the planet ring in hub gear fashion. The detail isn't important, it's for the final designer to decide, as are the possible mechanical and electrical change methods if used.

 

You won't be able to adapt those existing bike hubs to this method, the motors no good for this job. A motor near to a direct drive one, but designed for very low speed rotation being needed. There's no alternative gears available for your motors either.

.

Edited July 22, 200718 yr by flecc

If I've understood correctly, I think that the topmost animation here somewhat illustrates the top & bottom gears in action: when engaged with the wheel, the outer ring (annulus) is the top gear when the motor drives the intermediate "planet" cogs, and vice versa the planet cogs make the low gear when engaged with the wheel while the motor drives the outer ring (annulus).

 

For middle gear, one must envision the hub & wheel being driven directly at an intermediate speed.

 

Stuart.

Yes, that's a good illustration Stuart, but it would be much easier for people to understand and follow if the animation had been smoother.

.

Just had an idea - and it will probably remain so....... but:

 

Supposing one had opposing overunning bearings on the carrier and the planets and that with the sun as the driver you had a negative gear ratio for low gear. For the high gear (direct drive) you would reverse the direction of the motor - the planets would lock and the carrier would be free to move - everything would move at motor speed.

 

Think I'll go and lie down for a bit before thinking this through again...

Edited July 22, 200718 yr by Miles

Ok, I think I am beginng to get it from the excellent examples that have been posted. A couple of questions though.

 

I understand that the Annulus and the Planets turn at different speeds, but I dont understand how that effects wheel rotation. On a deraillier its simple, you can see the chain going from the crank to the gear selected. But on internal hub gears, if I choose the Annulus gear, how does that gearing get pased through to the wheel?

 

Is there something else involved, something shifting back and forth across the gears that isnt shown in these diagrams?

 

Or am I a lost cause?

 

EDIT is this what the spindle is doing, and also selecting what is in contact with the wheel?

Edited July 22, 200718 yr by JohnInStockie

Yes, there's a shifter involved John, changing between gears up or down, but you don't need to bother with that to understand the gears. Just look at this extract from my above post again and you'll see that I've said how the wheel is connected:

 

"Now if that annulus around the outside is rotated (by a drive from the sprocket) around the whole, the planets are forced to rotate, since they are engaged with the stationary sun, and have to roll around it.

 

As those planets revolve around the sun, they and the ring cage they are mounted on are trailing along after the outer annulus as it turns.

 

As that planet ring is travelling slower, we connect it to the wheel, so the bike wheel is now revolving slower than the sprocket. Therefore it's geared down, so that's low gear."

 

That coupling of the selected gear and the wheel is done by an actuator either by the rider or automatically as the spin speed rises, but as said, don't bother with such details, it's only necessary to understand how gearing changes turn speed either up or down.

.

Just had an idea - and it will probably remain so....... but:

 

Supposing one had opposing overunning bearings on the carrier and the planets and that with the sun as the driver you had a negative gear ratio for low gear. For the high gear (direct drive) you would reverse the direction of the motor - the planets would lock and the carrier would be free to move - everything would move at motor speed.

 

Think I'll go and lie down for a bit before thinking this through again...

 

I's briefly considered this sort of method but dropped it immediately Miles. To keep a silent drive I'd want nylon gears still, and this locking method would put all drive force across a set of stationary nylon teeth. I feel that could lead to mechanical failure. As it is, to protect the nylon gears during changes I'd incorporate a neoprene or similar material "cush" hub, probably within the sun pinion, since that would be quite a large diameter for a suitable not too low ratio.

.

Yes, not too practical with nylon gears..

 

Bypass the planets with a freewheel from the carrier to the ring?

 

Too tired to think.... I'm off to bed....

Edited July 22, 200718 yr by Miles

Yes, could do, though I was considering a conventional motor to sun freewheel. The final details could be fine tuned in various ways, but I think the end designer could determine what they'd use.

 

It would be good to think someone would produce a motor of this type, but I won't hold my breath.

 

Re: tired. My world is opposite to most, my best work and concentration in the late hours. In the morning I can just about think up a coffee!

.

Edited July 22, 200718 yr by flecc

It's quite a lot of trouble to produce something which only has a marginal advantage (from a commercial viewpoint), unless you're designing for offroad ;-) use....

 

 

I'm at my peak at 9am after getting up at 6am and having had at least 2 coffees.....

Edited July 22, 200718 yr by Miles

I've long given up bothering much with the commercial aspects. The world can have what it chooses to want, irrelevant to me either way since I want no commercial involvement.

.

My position also.

I can't remember if I've posted these here before, or not...

 

Change-over Gear

 

Anyway, worth reviewing in the context of this thread.

You did post it before, but it was a long time ago now, so worth inclusion here as you say Miles. This sort of changeover would have been even easier for Heinzmann to incorporate with their single cog and annulus design.

 

I prefer the simplicity of mine though, using virtually what's there in most of today's hub motors.

.

Have not read the entiere Thread yet...

 

but two things came to my mind after reading the first postings..

 

1.) (light <-> 2 motors):

instead of 2 motors, it should be possible to use one motor (brushless)

and use the triangle and star-configuration (or do you call it asterix !?!)

 

how ever: the problem would not be the motor (nearly every brushless motor should be usable for this when the windings are made for it, so rewinded)

 

there would be the need of a intelligent controller..

the difference between triangle/star is about factor 1.7

 

so: when the bike runs 10mph with star-configuration it would have the torque you need, when switching to triangle the speed of the motor would go up by factor 1.7, so it would run 17mph on same voltage..

 

ideally the controller should do this by itselfs..

so when you start it runs always in star-configuration, reaching maximum speed (and measured current not to high) the controller should switch to triangle configuration and the bike would accelerate even further..

when the current goes up too high (hill) and speed for that down, the controller should shift back to star-configuration

 

ideally the user should not feel anything about this..

it would simply be like having two motors, one winded for running 17mph max, one winded for running 10mph max.

 

thats for the motors.. this should cost only some few gramms of weight for additional wires and maybe a little bigger controller

 

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

 

second:

i slimm hub-motor, mounted between front and rear-wheel under the frame (with special build frame for that, maybe a little longer than usually)

would be a nice sollution i think..

the hub-motor would run slow and for that very quiet (as used from this kind of motors in the wheels)

you could use all the gears of the bike..

the one single additional chain should not increase noise that much..

weight-distributation should also be good, when the motor sits in the middle and not in front or rear-wheel

 

combined with a 14gear-rollof hub-gear that should be killer..

wide range of gearing -> should allow hill-climbe of any hill around with 6mph and nevertheless high speed in flat surfaces..

 

i mean it like this bike here,

picture: http://www.bike-elektro-antrieb.ch/bilder2/Bodenfreiheit_103.jpg

but instead of that load motor a much more quiet hub-motor

(and because it does not have to carry the weight of the bike and the person on the bike like a spoked in inwheel-hub-motor, this motor could be build much lighter for same power as well)

 

free-running-units for the pedals: the bike on the picture above (more pics: http://www.pedelecs.co.uk/forum/electric-bicycles/263-first-offroad-e-bike.html)

uses such free-spinning units, so this is also no problem

It can certainly be done that way kraeuterbutter, and as you say a hub motor type would be quieter. However, I'm very definitely not in favour of using cycle gears for motor drive, hence my two speed hub suggestion.

 

Riders need lots of gears, motors definitely don't, especially if Hall effect motors.

 

It's illogical to use the cycle gears, since that gives loss of motor drive during cyclist gear changes, therefore losing momentum. This is especially important if changing gear when climbing, since the loss of momentum can be large then.

 

As you know, I'm opposed to electrical methods of changing motor characteristics such as in star formation, they are never as efficient as a motor using a best single mode design. I know you disagree.

.

hmm.. shifting on a hill when motor runs through gears..

never thought about that..

could realy be tricky or a problem if the hill is steep and the load on the chain big.. unloading with motor maybe not that easy like when you pedal by yourself, where you can give it a "kick" and then reduce power as much so you can shift..

 

for your last sentence:

in rc-plane-sport there were long-time-flying-competitions..

there were - beside to "glockenancker-Motoren" also brushless-motors used..

AND: for getting most efficience out of them at two rpms: with a - mechanically switched - triangle/star-configuration !

 

same thing i have seen on a competition solar-powered one-person-car for a solar-ralley..

build by some German university..

it had also an hub-motor with incredible high efficience above 98% !!

AND: it used both, triangle and star-configuration, shiftable...

 

so: in both cases efficience is the thing most wanted... in both cases they used both..

there is no real change on the motor needed:

only - instead of connecting the 3 wires for star-configuration inside the motor or paralleling each two cables for triangle, you have to bring all 6 cables out of the motor and do the triangle/star-thing outside of the motor mechanically or idealy bring all 6 cables to the controller and he does it himself..

 

running a motor in triangle which is made for 17mph with reduced throttle at 10mph would never be as efficience than running the same motor in star for the 10mph and in triangle for the 17mph..

 

same thing i have seen on a competition solar-powered one-person-car for a solar-ralley..

build by some German university..

it had also an hub-motor with incredible high efficience above 98% !!

AND: it used both, triangle and star-configuration, shiftable...

 

 

This is what makes me so cynical about such claims kraeuterbutter, 98% efficiency in an electric motor is completely impossible and has never been approached.

 

Once I see that sort of statement from any organisation I know that I can't trust anything they say.

 

And as I so often say, if it were so easy, it would be on the market. The commercial world is never slow to exploit an opportunity.

.

I have to agree with Flecc, 98% efficiency is simply not a credible claim, it's only 3% short of perpetual motion:rolleyes: A claim of even 88% for a small motor would make me sceptical.

Solar Powered Electric Vehicles

 

Obviously, it's not commercially viable......

 

Also, scroll down here:

Here are two electric trikes I have developed:

 

 

Alternatively, you could use the Cyclone motor without its gearbox, as it's 97.6% efficient...

Edited August 6, 200718 yr by Miles