Epicyclic retro-direct 2 speed transmission

[Miles]

Epicyclic retro-direct 2 speed transmission.

If the planet carrier of an epicyclic is held, the input and output (via sun and ring gear) will be in opposite rotational directions. This allows the possibility for a compact retro-direct gearbox by either channelling the input through the sun gear and taking the reduced speed output of the ring gear to the concentric I/O (input/output) shaft, or by driving the I/O shaft directly, bypassing the epicyclic. An opposing pair of sprag clutches on the input pulley will enable the switch over to be made by simply changing the rotational direction of the motor - one of the sprag clutches being connected to the sun gear, the other to the I/O shaft. The sun gear is an idler on the I/O shaft. A sprag clutch between the ring gear and I/O shaft will complete the isolation of the epicyclic when the transmission is run in " direct" mode.

I worked this one out for myself. Anyone know of anything similar?

More to follow....

 

[HAL9000v2.0]

Cool. It took me 7 readings to get the whole picture.
You can simplify and put only one sprag clutch between outer gear and innner gear in opposite direction of lower reduction and hold the planet gear holder from another side. Something like dual centrifugal clutch in standard chain saw.

Miles, it's patent time..

 

[Miles]

Miles, it's patent time..

Too late now

 

[HAL9000v2.0]

You can still delete it...
... and pay me to shut up...

 

[HAL9000v2.0]

wait, there is one "side" missing...maybe.. i have to draw it...
If you hold the middle gears on one side from outside the input goes from another side and over sprag clutch goes on other input the output must be on same side where you hold the middle gears so the housing can be only on two bearings one bigger on outer gear and one smaller on output shaft...or you ment it other way?

 

[Miles]

wait, there is one "side" missing...maybe.. i have to draw it...
If you hold the middle gears on one side from outside the input goes from another side and over sprag clutch goes on other input the output must be on same side where you hold the middle gears so the housing can be only on two bearings one bigger on outer gear and one smaller on output shaft...or you ment it other way?

I'm working on a model to illustrate it. At present the planets are mounted on the gearbox frame which also supports the sun gear and I/O shaft by using a dual concentric bearing.

 

[HAL9000v2.0]

This is THE epic inovation that came from this forum...
It is the Miles drive for me.

I found something simmilar in drawing of one old russian dual prop helicopter. I'll try to scan it and post it here. anyway I think that you are first on this.

 

[Miles]

This is THE epic inovation that came from this forum...
It is the Miles drive for me.

Thanks Hal

Now we need a collective effort to work out the most practical implementation of it.

 

[HAL9000v2.0]

Also you will be known as "cordless drill killer"

 

[TylerDurden]

Anyone know of anything similar?

Not sure. Washing machines occasionally use motor reversal to drive the agitator slowly or the basket quickly, but I can't recall if planetary reduction is common... more likely countershafts.

 

[Miles]

Also you will be known as "cordless drill killer"

:lol:

 

[12p3phPMDC]

Motor reversal is the only thing I don't like...because of the RC controller.
otherwise it is cool idea...

Check this out from the motorcyle threads:

gogo posted this planetary transmission.

It needs external hubs for bearings though.

 

[Miles]

Motor reversal is the only thing I don't like...because of the RC controller.
otherwise it is cool idea...

We just need a suitable high voltage reversing controller. They already exist for RC boats and cars. I like the retro-direct system because it does away with the need for a mechanically controlled change system. You can change gear with a switch or automatically based on road speed. Centrifugal clutches are ok, just not so controllable.

 

[WTC]

The two speed epicyclic with centrifugal clutch that you show in the figure is from the mopeds built by Solo of germany.

Britt

 

[12p3phPMDC]

Yes, on demand is nice

re: Solo
Uh oh...you've spoiled gogo's ability to corner the market!
j/k... I hope he is able to buy or source the two he wants..

 

[John in CR]

I don't know what epicyclic is, but isn't that what I was getting at some time ago with using the guts of a geared hub motor to make a retro-direct 2 speed?

John

 

[12p3phPMDC]

epicyclic is just another name for planetary gearing.

 

[TylerDurden]

isn't that what I was getting at some time ago with using the guts of a geared hub motor to make a retro-direct 2 speed?

Generally, or specifically?

In this case, the concept rests on locking or unlocking the planet driver, yes?

 

[John in CR]

isn't that what I was getting at some time ago with using the guts of a geared hub motor to make a retro-direct 2 speed?

Generally, or specifically?

In this case, the concept rests on locking or unlocking the planet driver, yes?

For using the geared hub, a freewheel would do that leaving the sun and planets always engaged. I don't fully understand Miles idea, but everyone's reaction is great, so let's build a bunch of them. Count me in on a group deal.

John

 

[TylerDurden]

I don't fully understand Miles idea, but everyone's reaction is great, so let's build a bunch of them. Count me in on a group deal.

You'll get the first protos... it might weigh a bit.

This vid illustrates the idea. Locking the planet carrier reverses the output; letting the carrier follow the driver provides direct-drive in the same direction. Using clutches to lock/unlock components, reversing the motor can change the output ratio and the direction will be correct (motor_rev + gear_rev = output !rev).

[youtube]a1JAWoAvK-E[/youtube]

 

[John in CR]

I don't know TD. It doesn't need to be too heavy, since my Bafang without the motor in it doesn't weigh much and has unnecessary weight in the housing. Drive the wheel off the input shaft for high gear and the housing freewheels on the built in freewheel. Turn it the other direction and the housing turns in low gear, and you drive the wheel then off of the housing rotation. It's all threaded and ready to go for a freewheel already. Just a bearing or 2 needed to drive that sun gear from the exterior. Simple enough for even a low tech guy like me.

John

 

[TylerDurden]

Ok John, I'm catching on... I'm not up to speed on the Bafang construction details, but I rekon there should be a way to hack it. (I just can't visualize it yet. It would have one chain for input and one for output?)

 

[swbluto]

I have no clue what's going on, besides it probably being an e-bike appropriate 2-speed transmission, but I just hope there's something appropriate to buy for my build in 3 or so months.

 

[mclovin]

I think changing the motor input direction can be done rather simply by a mechanical system.

FYI The sproket on the far left is the driver from the motor shaft.

CCW

CW

These screen shots illustrate the concept if but maybe not the method.

 

[John in CR]

McLovin,

My resistance to changing rotation direction mechanically is 2 fold. 1. each stage reduces efficiency and increase cost, and 2. Instead of changing rotation direction use similar and simpler mechanical steps to create a 2sp tranny.

Many controllers can do reverse with a simple low current switch, which is the simplest method by far.

John