Engineering Question (Worm gears)

[CSGAS]

I need to rotate a large Diameter ring say 15 degrees with a worm gear. Obviously don't need have teeth all the way around the ring so I'm attaching a curved rack of 20 degree range. I want 60:1 ratio but here lies the question:

Do I take no. of teeth - 60 - across the entire ring (ie. 2.5 teeth across the 20 degrees) or just the 15 degrees I need?

Pleeeeease help! I can't find any relevent theory anywhere for this!

Cheers
Chris

 

[LizardKing]

Ive got a feeling (not done anything remotly like this since leaving college) that you would need the 60teeth over the 15degrees you need as the worm gear is only one tooth, that would give you the 60:1 ratio you need, in my eyes anyhow

 

[Mr Joshua]

(ie. 2.5 teeth across the 20 degrees) or just the 15 degrees I need?

Are you sure it's 2.5 for 20 degrees?

I make it as 3.3333333333333333333333333333333, 2.5 is for 15 degrees I think.

Out of curiosity, what are you making/trying to achieve?

 

[VIRII]

The ratio is normally ring to ring.
So 60 turns of the worm would create 1 360 degree turn of the large ring.

I guess it really depends how the original question is worded.