Tangental and Thrust force on worm gear

[Pedalpowered]

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 10[sup]7[/sup]) 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?

 

[Occupant]

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

 

[Pedalpowered]

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.

 

[Occupant]

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.

 

[Pedalpowered]

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.

 

[Occupant]

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.

 

[desertfox]

Hi
Try this site:-

http://www.roymechx.co.uk/Useful_Tables/Drive/Worm_Gears.html

 

[Pedalpowered]

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.

 

[Occupant]

If you, Pedalpowered are still there fine, if not, just to set the record straight. I made a mistake, the force I calculated is not the axial force but simply the force creating the torque. Use the attached for the axial force.

 

[Occupant]

Third time is the charm. Had the force in the wrong direction.

 

[Pedalpowered]

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.