Calculating shaft sizes

Calculating shaft sizes

I think the upper right formula for a shaft with key way applies.

Lets work out what the motor shaft needs to be.

cube root ((40x1.5HP) /1725) = 0.33 in

So now how do I work out the size for the next shaft and the one after that.

HP = torque x RPM so that does not change,  

From a previous post with the addition of RPM for each shaft.

belt	motor	1st shaft	2nd shaft	spindle	ratio
1: V	2"	10"			5:1
2: V		2.6"	9.75"*		3.75:1
4: flat tooth			2"	8.5"	4:1
RPM	1725	345	92	23	75:1

again for the 1.5HP motor
cube root ((40x1.5HP) /1725) = 0.33 in
1st shaft

cube root ((40x1.5HP) /345 = 0.56 in

2nd shaft
cube root ((40x1.5HP) /92 = 0.87 in   (7/8")

spindle
cube root ((40x1.5HP) /23 = 1.38 in

So clearly I will have to up size the 2nd shaft and bearings to use the 1.5 HP

What about the 1/2 HP motor

cube root ((40x0.5HP) /1725) = 0.23 in
1st shaft

cube root ((40x0.5HP) /345 = 0.39 in

2nd shaft
cube root ((40x0.5HP) /92 = 0.60 in

spindle
cube root ((40x0.5HP) /23 = 0.95 in

On this one the 2nd is also weak but maybe close enough to work.  Do what I can to use a shaft without a key way between the pulleys.  Maybe that will belp.

Conclusion

The unit can be built with the existing drive stuff and the 1/2 HP motor.

To upgrade to the 1.5 HP I will need a 1" 2nd shaft and bearings.  Will also need to cast or find a beefier large pulley for the 2nd shaft.  The hub on the existing one can not be bored to an inch.

Hope is that belt 2 will be ok.  Maybe need to double it or go to a poly V. Need to figure out how to calculate that.