worm gear

[coolking]

Hi all,
Please refer to the attached dia.
I have a worm (gear) resting in a housing (having same helixal gear pattern as worm) and housing is fixed. Worm can rotate and move along its axis. When only axial force in the worm gear shaft(long shaft) are induced, i just want to find by what axial force the worm starts to rotate in the housing ?
material is steel(worm & housing), friction between steel-steel approx. 0.15, what factors influence the rotation of the worm ?
is it possible to calculate by hand, by what force worm starts to rotate in the housing?

thanks in advance

 

[Jboggs]

The worm will only rotate if (1) its teeth are engaged with similar helical screw-like grooves on the inside of the housing, and (2) it can also move axially. It appears from your diagram that it cannot move axially.

 

[coolking]

Hi Jboggs, I modified the question, its a rough dia. obvious worm & housing are having same gear pattern and worm axial movement is allowed inside housing. But housing itself fixed. Worm can perfectly engange and rotate inside the housing, by what axial force its starts to rotate inside the housing ? any way to calculate by hand ?

 

[Jboggs]

This is simply a screw. You may call it a worm gear, but its really just a screw. The generally accepted screw form for converting linear to rotary motion and the opposite is acme threads. The relationship between linear force and rotary motion is a function of three things, the helix angle, the tooth form, and the level of friction. You can find the formulas in Machinery's Handbook, or on many engineering websites.

 

[GregLocock]

There will be an additional friction component from the left most face of the worm bearing on the housing.

Big clue, it won't be a force that makes it start rotating, it'll either rotate or it won't, if you are using a linear friction model.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[Jboggs]

Greg is right. Look up self-locking lead screw.