Drawing Andrews Worm Wheel

[Anonymous]

Having now machined a real worm wheel I'm none the wiser as to how the tooth form varies across the tooth.

Regards,

Andrew

[Sub MandrelParticipant @submandrel]

You must do, or you wouldn't have pointed out my approach would generate a helical gear, not an enveloping one!

Think in slices through the gear. At centre it is true involute. At sides it is less depth, but also it is not a radial slice through the worm… so not just the tip of the involute, but a stretched version of it.

Neil

[Mark CParticipant @markc]

Neil, Did you notice that the worm has a different profile on each side of the "tooth"? Due to the inclined nature of the contact I doubt it is really "involute" but some modified form – a sort of oblique involute (if such a thing is still involute) of some sort.

Mark

[Sub MandrelParticipant @submandrel]

Surely it should be symmetrical…?

Neil

[Mark CParticipant @markc]

Nope, very clearly asymmetric. I think due to the helix angle, but I was starting to think that the the worm should have an involute form of some sort rather than a straight sided flank.

Mark

[Anonymous]

Looking at the end of the teeth they seem slightly asymmetric to me:

But of course that could just be iffy machining.

Regards,

Andrew

[jason udallParticipant @jasonudall57142]

My guess .the original was filed to fit and run for polish..tight wears and clearance doesn’t matter..this is why things used to be “run in”..
The engineering/design fascinates me. But it might be the curves and surfaces “generated” by the run -in meshing set differ from our ideal in subtle ways … …

[Author]

Posts