pic: Gerrish Gearbox MKII

[Tytus Gerrish]

Although I do Love your Critical essays To me All you realy had to say was....

"So tytus, You dont have the numbers?"


And here is an intresting pdf...
www.army.mil/usapa/doctrine/DR_pubs/ dr_a/pdf/fm1_514.pdf
id like to point out the part on the combining transmition
Im still looking for more info... so its on the way

[Gadget470]

... and she's right. You just say "add everything and it's better"

Perhaps create a white paper, one with calculations, better (and by better, I mean easier to understand) drawings with less fancy textures, and then really ask what people think.

[Ryan Dognaux]

Hey Tytus - just curious, did you make all that in 3D Studio Max, or did you import some stuff from CAD/Inventor into 3D Studio Max??

Also, taking in some of what people have said here.. it is true that you can't really judge any real-world attributes of objects in 3D Studio Max... unless you have certain add-ons/settings that allow that... Inventor/CAD would be a much better help if you try to do some math and test some things before ya build it.

Design looks interesting, keep at it

[FotoPlasma]

Originally posted by Tytus Gerrish
And here is an intresting pdf...
www.army.mil/usapa/doctrine/DR_pubs/ dr_a/pdf/fm1_514.pdf
id like to point out the part on the combining transmition
Im still looking for more info... so its on the way

Here's a working URL for that PDF.

<edit>
Because of the fact that that PDF is image based, you can't search through it. Also, actual information pertaining to a "combining transmission" seemed a little lacking. This irked me a little, so I searched around a little.
</edit>

Other than that, upon my own investigation of "combining transmissions," it seems they're only used in rotary aircraft (helicopters [namely the Chinook] for the most part).

Here's another website that explains the CH-47 drivetrain's usage of a "combining transmission," or "C-Box," as they like to call it. The images on their website are artificially shrunk, so here're some links to the actual full-size images:

Diagram of CH-47 drivetrain, focusing on how the assembly is integrated into the body of the aircraft.

Conceptual diagram of the actual mechanical set-up of the system.

Assuming the engines are the same, in the concept diagram, they output 15066rpm, which goes through a ~1.23:1 reduction, taking it to 12263rpm, which goes through another reduction of ~1.77:1, taking it to 6912rpm, which goes to the two independant (somewhat) rotors, which have their own ~30.72:1 reduction, before the output shaft (the rotor) which is a nice and manageable 225rpm.

I have no idea what I added to this thread, probably nothing, but there's a little more information about practical usage of this kind of system. *beats a dead horse*

And just for the record, I still love Google.

[Madison]

Originally posted by Tytus Gerrish
Although I do Love your Critical essays To me All you realy had to say was....

"So tytus, You dont have the numbers?"

Well, whatever. I'm tired of this, so I'm done.

If you can manage to build it and make it work, good for you. If you happen to manage to do that by pulling it straight out of your behind, I don't care. I've done what I can to provide a better explanation as to how and why this may operate and how and why it can be improved. If you're not interested in learning from that, I'm not interested in providing it.

You have a lot to learn about everything.

Good luck.

[Tytus Gerrish]

ok... Ill build it, ill prove it works, Ill change the way multi-motor drives are built Forever!

(ok, getting a little ahead of myself there.... ,At least ill build it)

[Ianworld]

A friend of mine directed me towards the Toyota prius (and i suppose other hybrid cars.) They have two inputs at varying speeds and combine them to produce one output. Unfortunatly i haven't been able to find a good source of information on the topic of their transmissions but i'm still searching. Might be good place to look for more info.

I'm starting to edge towards beltless CVT though...

[Matt Attallah]

Originally posted by Ianworld
A friend of mine directed me towards the Toyota prius (and i suppose other hybrid cars.) They have two inputs at varying speeds and combine them to produce one output. ...

I was under the impression that they used one or the other - not both. When it needed heavy acceleration it used the gas engine - but when it was coasting or anything like that - it gave the power from the engine to the generators so the gens. can charge the battery while the electric motor was being used...


But if they do use both at once - they can use a viscous coupling, and I'm sure that can help in its moments...

[FotoPlasma]

Originally posted by Matt Attallah
I was under the impression that they used one or the other - not both. When it needed heavy acceleration it used the gas engine - but when it was coasting or anything like that - it gave the power from the engine to the generators so the gens. can charge the battery while the electric motor was being used...


But if they do use both at once - they can use a viscous coupling, and I'm sure that can help in its moments...

I am absolutely not an automotive expert, so I apologize in advance if I'm just being stupid (not to mention the fact that I just woke up).

That said, after a little searching, I found this, a comparison between the Honda Insight and the Toyota Prius regarding their drivetrains.

According to the various diagrams of energy flow (mechanical and electrical) in various states of use (stationary, starting up, accelerating, cruising, and decelerating/regenerative breaking), it seems as though both the electric motor and the internal combustion engine are used in tandem much of the time, in the Prius (and obviously less of the time in the Insight, but it still happens).

[Jnadke]

Originally posted by Ianworld
A friend of mine directed me towards the Toyota prius (and i suppose other hybrid cars.) They have two inputs at varying speeds and combine them to produce one output. Unfortunatly i haven't been able to find a good source of information on the topic of their transmissions but i'm still searching. Might be good place to look for more info.

The Prius uses electric generator/motor at different stages in the drivetrain. Primarily, the gas engine exerts power into a planetary gear system. One part of the planet is connected to a generator. The other part is connected directly to the wheels. As the engine rotates, it exerts equal torque on both the wheels and the generator. As the generator produces more electricity, it exerts more torque as a reaction, thus, the engine can exert more torque on the entire system. Basically: The torque is split between the wheels and the generator.

The neat thing, however, is that the power created by the generator (when the batteries are full), is sent to a motor that is directly connected to the driveshaft that, ultimately, leads to the wheels (after the planetary gear system). So, contrary to belief, the Prius planetary gearbox does not have two inputs. Its planetary gearbox actually has one input and two outputs. The only exception to this is when it is using regenerative braking.

Originally posted by Tytus Gerrish
But still In spite of its disadvantages it will Combine the force of two motors over a larger power arc than any ideas ive seen yet ,wich Work! but when theyre slowed down By puching Or accelarating They will not Be as efficent as My device

1. You can't get any more efficient than 100%. Traditional gearing will combine the torque while still allowing the same top speed. Do the math and you end up with the same power output as the sum of the two motors.

2. If you've learned anything from the explanation of the Prius above, you cannot exert more torque than the weakest motor (believe me, if Toyota could operate at greater than 100% efficiency, they would). Once you do, it will act as a generator. The power output of the remaining motor will be split between the wheels and the generator. The bad thing is, all the speed controllers do with this generated power is get rid of it, as heat. Basically, this limitation makes this system bad for pushing applications (when using motors with dissimilar torques).

3. Actually, I got the idea from a patent when I was surfing the internet. Technically, it's not your device. It belongs to the guy that patented it. Beyond usage for non-profit applications, you have no rights to it.
Differential electric engine with variable torque conversion
Continuously variable transmission system
Continuously variable gear drive transmission
Electric constant speed/variable speed drive/generator assembly

There's a lot of neat stuff floating around in the patent database. All of it is free range to us since we're using it not-for-profit. Sometimes when I have an idea I search there to see if there's a better idea or to see if it's feasible.

Originally posted by Ianworld
Good thing i found this thread. I was about to try to build something like this without knowing the short comings.

Thank you. You really have to realize what the two parts independently are doing, and then piece them together. Instead of being an input, pretend it's a fixed shaft. You'll then realize that such a system does provide some benefits, but also has some quirks. Such an idea could succeed if you could develop an easy mechanism to mechanically stop the shaft and hold it in place. The Thunderchickens did so using worm gears. The bad part is that worm gears are 75% efficient at best. A more realistic estimate is 50%.

[Joe Johnson]

Worm & Worm gear combos are not typically even 50% efficient.

There is a very good match between effeciency and backdriveability so in the case of the the Thunderchicken drive, they were probably way under 50% or else the system would have been backdriveable.

Joe J.

[Tytus Gerrish]

A Dual-engine helocopter Roto-train

[sanddrag]

That's pretty neat however is appears that each motor would be spinning at the same speed. Have you tried it with different gearing on one motor?

[Gadget470]

Urmm.. having them at different speeds (in that orientation) will definitly cause a generator. Give it a whirl, program the rcx so one is going 100% and the other 50-80% Should be some interesting results.

Edit: If you have a rotation sensor, maybe you could get some good feedback?

[Tytus Gerrish]

Originally posted by Gadget470
Urmm.. having them at different speeds (in that orientation) will definitly cause a generator. Give it a whirl, program the rcx so one is going 100% and the other 50-80% Should be some interesting results.

Edit: If you have a rotation sensor, maybe you could get some good feedback?

thats exactly what i did Boyo!