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Walter_Sobchak

Transmissions and final drives

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On 6/15/2017 at 3:02 PM, Xoon said:

Felt like sharing this gem:
http://www.ffi.no/no/Rapporter/08-01220.pdf

 

A report on hybrid electric vehicles. 

 

A neat idea here is to use the hybrid electric system to power a ETC gun. This could solve the power issue, at the cost of no or reduced mobility during firing. 

 

Xoon,

 

Thank you very much for this PDF! It's extremely useful, thought provoking, informative, and the focused comprehensiveness in it's coverage of hybrid vehicles for military use without the extraneous stuff that doesn't apply.

(like self congratulatory smug preachiness, moral exceptionalism, and the other bullshit topics about hybrid anything attract)

 

As I'm reading it,  I am actually gaining clarity on stuff that resources like technology of tanks only managed to confuse and frustrate me about even further.

 

There are several people off this site I'd like to pass a copy of this to if you are OK with my doing so.

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22 hours ago, roguetechie said:

 

Xoon,

 

Thank you very much for this PDF! It's extremely useful, thought provoking, informative, and the focused comprehensiveness in it's coverage of hybrid vehicles for military use without the extraneous stuff that doesn't apply.

(like self congratulatory smug preachiness, moral exceptionalism, and the other bullshit topics about hybrid anything attract)

 

As I'm reading it,  I am actually gaining clarity on stuff that resources like technology of tanks only managed to confuse and frustrate me about even further.

 

There are several people off this site I'd like to pass a copy of this to if you are OK with my doing so.

Feel free to share it as much as you want, anything I find for that matter.  It's not mine anyways. 

 

Found it at Forsvarets forskningsinstitutt's site (Norwegian Military Science Institute).

 

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I found this quite interesting, and I would like people to share their opinion on this:

 

 

In short, magnetic gearing. Zero contact between the two "gears" meaning "no friction", no need for lubricant, very reliable and claimed efficiency of 99% at high speeds and "much higher at lower speeds compared to conventional gearing. 

 

What this means is that you can have a final drive with almost no wear and a very long lifespan, if we do no count the bearings. It also has a side effect of slipping when the torque goes past the rated torque. This means that the drive would disengage instead of breaking itself. I think this works well with electric motors, considering their long lifespan, which often needs a gearbox to optimize the torque. 

 

The company realized this and apparently made a Psuedo-direct drive, integrating it into the motor and claim a much better torque density. I think this would be quite useful for AFVs to reduce the size of the engine bay. 

 

 

They also made a magnetic CVT:
imgsize.php?w=265&img=MAGSPLIT-on-TEST.J

imgsize.php?w=265&img=MAGSPLIT2-on-build
Should be self explanatory for anyone that knows what a CVT is. Claims to be 32% more efficient that a conventional gearbox.

 

The only disadvantages I can think of is higher price and needing to keep the magnets below their Curie point. 

 

 

 

And we have magnetic bearings too:
en-after47-1.jpg?ts=1355199050

 

Simply, they are like magnetic gears, only as bearings. They can support a theoretically infinite RPM, with no friction. They can operate in a vacuum and in very hostile environments. 

 

They come in two types, active and passive. Active bearings use sensors and electromagnets in a feedback loop does a "tug of war" to keep the object in the center. A passive system uses permanent magnets. 

Some include a backup bearing in case of a failure. Same disadvantages as above. 

 

 

This could make for a system with almost zero friction, no lubricant and a very long lifespan. In theory, non of these parts would ever need to be replaced, some maintenance would be needed to remove pill up of dirt and dust.

With a magnetic coupling, you could also have a sprocket that does need to compromise the armor, as it can transfer the power through it magnetically. 

 

Sources:
https://en.wikipedia.org/wiki/Magnetic_bearing

http://www.magnomatics.com/pages/technology/pseudo-direct-drive.htm

http://www.magnomatics.com/pages/technology/low-ratio-magnetic-gears.htm

http://www.magnomatics.com/pages/technology/magsplit.htm

http://www.magnomatics.com/

https://en.wikipedia.org/wiki/Magnetic_coupling

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Transferring power through the hull would screw with the efficiency - for conductive armour you'd induce eddy currents, and for non-conductive armour you'd still have a big "air" gap to deal with. Probably not worth it for AFV's, but if it eliminates the shaft seal then this could be very useful for submarines (depending on the EM signature)

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1 hour ago, Xlucine said:

Transferring power through the hull would screw with the efficiency - for conductive armour you'd induce eddy currents, and for non-conductive armour you'd still have a big "air" gap to deal with. Probably not worth it for AFV's, but if it eliminates the shaft seal then this could be very useful for submarines (depending on the EM signature)

Forgot that a big metal plate works as a conductor. 

 

Still, the air gap should not be too bad if something like ceramic are used. Alternatively, a composite sandwich of conductors and isolators could be used, like NERA.

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