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# Quarter turn gear box!

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## Quarter turn gear box!

(OP)
Dear all,

I calculated the module & p.c.d of a worm & worm wheel for a Quarter turn gear box (used as a operator for butterfly valves)by starting with the torque required & using the lewis equation.Now,I require to calculate the handwheel shaft dia & the handwheel dia.Since the worm is hollow the O.D of shaft is assmled. inside the worm & is fastened by shear pin.The handwheel is fastened to the other end of the shaft again by a shear pin.

Is the shaft only affected by shear stress?If it is,then I will calculate the shear stress keeping the dia. unknown.Then all I have to do is equate it with the shaft material's allowable shear stress to get the diameter.Is my design intent o.k?Also,I would like the esteemed members of this thread to tell me the way to calculate the handwheel dia.

For info. the o/p torque is 50 kgmt,the material of worm wheel is astm a 395 400/18.The ratio i arrived is 40:1,m=2.25,pcd=90,dist. between the centers of worm wheel & worm is 61mm.

### RE: Quarter turn gear box!

look in MSS SP-91 for how to figure force on a handwheel.

### RE: Quarter turn gear box!

For worm drives, the efficency varies greatly. The lower the worm lead angle, the lower is the efficency. For low lead angles, and poor thread quality, the efficency can get quite low.

Checking single stage gearbox efficency in a catalog can provide some insight. Look at the higher ratios, these will have lower lead angles.

AGMA has a worm design manual. Check out agma.org

### RE: Quarter turn gear box!

(OP)
Dear gearmanPE,

Thanks for the tip,But I found only spur & helical gears given in agma.org

Should I get registred as a member to have that info?

Bye,Thanks in anticipation.

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