windell747
Mechanical
Aloha,
I have a 270in-lb moment acting on a worm gear and I'm trying to calculate the thrust force extered on the shaft of the worm. The worm gear is about 3.3 inches in diameter.
For a static thrust load calculation the thrust force exerted on the worm shaft is about 270in-lbs/1.67in = 160lbs.
I was told that I should perform a dynamic thrust load calculation since the thrust force will increase while the worm is rotating. The worm will be spinning at about 24RPM max. The equation I was given to use is this one.
T=P/tan of lead angle
where T=thrust force,P=input torque/pitch radius of worm
Well, I know my output torque must be at least 270in-lbs. My worm gear ratio is 40:1. So I first divide 270in-lbs by 40. I get 6.75 in-lbs. I then multiply this by 1/worm gear efficiency. The efficiency I calculated for this worm gear set is 15%. By multiplying 6.75 in-lbs by 1/.15
I get 45 in-lbs as my input torque on the worm.
Then to solve for P, I divide 45in-lbs by 0.5in, the pitch radius of the worm. This gives me 90in-lbs.
Then to solve for the thrust force I divide 90 in-lbs by tan(4.08deg).
This gives me a thrust load of about 1260lbs. This dynamic thrust load does not seem to be right since by static calculation is only 160lbs.
Can anyone point out what I am doing wrong with this calculation? Is there another way I can calculate the thrust load exerted on the worm shaft? I'll be using this thrust load calculation to choose the proper thrust bearings for my worm gear box.
Mahalo
I have a 270in-lb moment acting on a worm gear and I'm trying to calculate the thrust force extered on the shaft of the worm. The worm gear is about 3.3 inches in diameter.
For a static thrust load calculation the thrust force exerted on the worm shaft is about 270in-lbs/1.67in = 160lbs.
I was told that I should perform a dynamic thrust load calculation since the thrust force will increase while the worm is rotating. The worm will be spinning at about 24RPM max. The equation I was given to use is this one.
T=P/tan of lead angle
where T=thrust force,P=input torque/pitch radius of worm
Well, I know my output torque must be at least 270in-lbs. My worm gear ratio is 40:1. So I first divide 270in-lbs by 40. I get 6.75 in-lbs. I then multiply this by 1/worm gear efficiency. The efficiency I calculated for this worm gear set is 15%. By multiplying 6.75 in-lbs by 1/.15
I get 45 in-lbs as my input torque on the worm.
Then to solve for P, I divide 45in-lbs by 0.5in, the pitch radius of the worm. This gives me 90in-lbs.
Then to solve for the thrust force I divide 90 in-lbs by tan(4.08deg).
This gives me a thrust load of about 1260lbs. This dynamic thrust load does not seem to be right since by static calculation is only 160lbs.
Can anyone point out what I am doing wrong with this calculation? Is there another way I can calculate the thrust load exerted on the worm shaft? I'll be using this thrust load calculation to choose the proper thrust bearings for my worm gear box.
Mahalo