Comparing Worm Sets vs Spur Gears

[Precursor]

I'm doing a comparison on worm sets over spur gear sets and I came across a question that seems rather simple, but I can't quite resolve. Here it is:

[PLAIN]http://img403.imageshack.us/img403/4848/42786849.png

I do know that worm sets typically achieve high torque and a low speed gear ratio, but in terms of the above question, where would the worm set be placed?

Any help is much appreciated.

 

[danev2]

The clue is understanding what spur gears and worm gears do at high speed.
which one has less friction?
I'm a bit rusty here... But I think that spurs had less friction at high speed.
So I would set the spurs first to step it down then the worm gear to step it down the rest of the way.

It's an opinion...

 

[Danger]

Gear ratios are cumulative, so the overall speed reduction and torque multiplication should be independent of the worm placement.
The only consideration that occurs to me is that I would probably use the worm/worm gear combination as the last component simply because that would allow for lighter (and cheaper) intermediate gears.

edit: I see that Danev beat me to the same conclusion, although it's worded a bit differently.

 

[Precursor]

So the worm set should be on the high torque, low speed end to increase efficiency?

 

[Lazer57]

I believe it should be the other way around. The worm gear set should be the driver because it is meant to operate at high speed and allows for huge reduction. The spur gear set is not meant for high speed or large reduction; the high speed would make it noisy, cause frequent shock loads and generally wreck the teeth. If you look through machine design books or just online you should be able to find sufficient information to make you confident of one of the options.