Worm face gear info/theory? 1

[bithkits]

Where can I find more information on "worm face gearsets"?

See one depicted here:

http://www.stepanlunin.com/Worm_face_C.html

It uses a standard cylindrical worm as used in a normal worm drive setup - this is important as we have this part threadrolled and cannot change it.

We have a product that uses a worm drive as we need a reduction of 36:1 or more and needs to be self locking. We would like to use injection molded plastic components and the worm wheel is difficult to make. In the throated case the tool is beyond the scope of what the tool and die makers in South Africa are comfortable with due to collapsible cores etc. In the unthroated case, it is possible but the helix angle makes ejecting the part complicated/unreliable.

A worm face gear would solve all our problems, but I am trying to find literature on the subject. My worries are that the axial forces will be too high.

Is there other terminology used to describe this type of gearset?

Adriaan.
I am a Mechatronics Engineer from South Africa.

http://www.martin-electronics.co.za

 

[WinstonH]

Adriaan,(bithkits),

That is a "HELICON"; the tapered worm was the "SPIROID"; Was itw division.Gear resembled a spiral bevel gear.

HELICON series ranged from 1.500" OD Gear to 24.000" OD, the book listed 31:1/38:1/47:1 ratio's.

One problem as I recall is none symmetrical pressure angle, although I did a prototype no offset version for guitar strings keys, could be assembled for left or right hand, they had regular worm.

I have a post on photobucket somewhere, I'll look it up.

Cheers,

 

[WinstonH]

Adriaan,

This is a "Helicon":

Cheers,

 

[bithkits]

WinstonH,

Thank you so much. That was very helpful. I thought there may be another term used to describe such a gear set! Thank you again!

Adriaan.
I am a Mechatronics Engineer from South Africa.

http://www.martin-electronics.co.za

 

[drawoh]

bithkits,

Be careful. Helicon, Hypoid and Spiroid gears are similar to worm gears, but they have their own geometry. They cannot be driven by a standard worm.

I designed a worm drive in which the teeth in the worm wheel were off centre. The gear fabricator I took this to told me he had seen this done before. However weird it looked, it was fabricatable with standard worm gear tooling.

Worm gear fabricators like to make the worm and worm wheel together. Failing that, they like to take the worm from you, and cut their worm wheel to fit.

It has been a while since I have done the calculation. A 36:1 ratio is with standard worm components and materials, is borderline for self locking. The only way to achive the lower lead angle you may need, is to select a larger diameter worm. Definitely, do the calculation.

Given the difficulties in making a worm wheel, are you really and truly stuck with the worm?

JHG