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Tangental and Thrust force on worm gear

Tangental and Thrust force on worm gear

Tangental and Thrust force on worm gear

(OP)
I need to get the thrust load on a worm shaft for bearing life calculations.

The Thrust force should be:
0.98 x Tangential force

And the Tangential force should be:
(1.91 x 107) x Power x efficiency
Pitch Diameter of gear x Speed of gear

So my 0.55Kw electric motor turning the 1", 2 start worm at 1500RPM
with a 50 tooth 4.167"gear with a 25:1 ratio nets me almost 42000N
of Thrust force, that can't be right, what am I doing wrong here?

RE: Tangental and Thrust force on worm gear

You lost me somewhere. A 0.55kW motor @ 1445rpm produces a torque of 2.681ft-lbf. With an 1.00" worm the axial load on the worm would, therefore, be U=2*torque/dw = 286N

RE: Tangental and Thrust force on worm gear

(OP)
So axial load on a worm is 2 x Torque / Worm Pd so

2 x 3.635Nm = 286N
0.0254m

That's way easier than what I was doing,
do you have a reference for that formula?
Most of the material I found on worm gears is willingly obtuse.

RE: Tangental and Thrust force on worm gear

I'll have to admit something must have gone wrong with my unit calculations. It came out to 572N the second time around. In any event, I did not use any literature, but since you asked, I did some checking on the Internet and came up with this.

RE: Tangental and Thrust force on worm gear

(OP)
Thanks, I had worked with that website before and it uses a completely different formula than the other places by using a whole lot of angles and rads to come up with something around 700N.

The Formula I was using at first comes from This PDF (Page 6 for worm gears). The equasion looks simple enough but I mess up somewhere and get really high numbers.

RE: Tangental and Thrust force on worm gear

No, when you look at the formula they are using for W=T/Rc it looks exactly like mine, but their calculation is wrong. It should still be 286N, but for some reason it isn't.

RE: Tangental and Thrust force on worm gear

(OP)
This site gives the 2 x M 1 / d 1 formula like Occupant first mentioned, I will stick with that one and the result of 286N for bearing life calculations.

I can probably use that site as a reference too, although the banner on top says the formulae are unverified.

RE: Tangental and Thrust force on worm gear

(OP)
Ah okay, that looks closer to a previous formula I saw, I can adjust for my actual pitch and friction and get numbers that make sense.
Thanks, it was a frustrating problem since everyone I asked looked at me with a blank face or pointed to a formula they didn't know how to apply.

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