How to find the overhung load of belt mechanism

[KKiril]

Hello folks, this my first post here. Im electrical eng. but I have to do some mechanical staff and here starts the problems. I have to choose gear box. In most catalog there is overhung load value. In my machine the I use belt to transfer the power but im not so sure haw to calculate the max overhung load. By def the overhung load it that load that acting then use belt, chain , rope and so on. And its equal of the moment on radios of mounted element F = M/r. we have additional const “z” with depend of number of teeth, tension of belt and so on. Im going to use SEW geared motor, so they give overhung load action on angle “a” in the middle point of output shaft

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Here is schematic of my machine

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The output end of shaft in couplet with pulley. So my question is there the overhang force is acting and on what angle. I need to know it, to choose the right gear unit. Thanks in advance !

 

[drawoh]

KKiril,

If your pulley is supported by bearings, the side load is insignificant.

If those two triangles on either side of your pulley are not bearings supporting it, your coupler will be working (somehow) at a 90[°][ ]angle, and the side load on your gearbox will be the least of your worries.

--
JHG

 

[KKiril]

Thanks. Yep, this little triangles are bearing. But i have big load, about 4800 kg. So the torque is going to be high so if overhang load is F=M/r i will get really big value. And there is other formula to calculate the overhung load. Its base on the dismantlement form the middle point of output shaft - x. So that the reason to try to understand there this force acting and on that angle. I can't understand there this thing acting in my situation ?

 

[MintJulep]

With little triangular bearings by design intent the overhung load is zero.

The actual side loading of the gearbox output shaft will depend on how well everything is aligned, and what type of coupler is used.

 

[Jboggs]

Overhung load involves force, not torque. It appears that you are confusing the torque required to drive your mechanism with the overhung load the shaft sees. You can best understand overhung load by picturing a VERY LARGE pulley mounted directly on the shaft. The shaft would be supporting the entire weight of the pulley and that would be the overhung load. Another case would be when the shaft is directly driving a belt or chain. The belt or chain would be under tension. The shaft would see that tension as overhung load. In your case all the forces of weight and belt tension are being handled downstream of the shaft. The shaft won't see those forces. It will only see the torque required to drive the mechanism.

The manufacturer's concern about overhung load on a gearbox has nothing to do with the strength of the shaft. He is concerned about overloading the bearings inside the gearbox.

 

[dvd]

Even for the arrangement shown, the pulley shaft deflection will create an overhung load on the reducer shaft unless a coupling is selected which will accommodate the misalignment due to shaft deflection. Make certain that the pulley shaft deflection at the end of the pulley shaft is smaller that the allowable angular and parallel misalignment of the coupling.

 

[chicopee]

Misalignment between gear and pulley will cause an external load on the gear box as well as the pulley.