Gear reduction ratio ????????

[JustWood]

Replacing my processor belt conveyor with a chain conveyor and I recently rebuilt a HD Morbark conveyor with new series 400 chain and paddles, new wear boards and sprokets. This is one beefy conveyor and the conveyor of my dreams!
Sprocket on shaft that pulls the conveyor chain is 8" in diameter at bottom of gullet between teeth.
Shaft is 1.75".
Motor will run 1750 RPM.
If I use the same size sprocket on gear drive and driving shaft, what gear ratio will I need to spec the reduction box at to get the conveyor to run 30FPM.
Also considering an adjustable speed inducer on new motor/gear drive so ratio woodn't have to be exactly 30FPM.
Any math wizards wanna take a shot at this.

 

[kevin j]

The conveyor drive sprocket is 8 inch to bottom of pockets. We need the center of the rollers or chain teeth, the effective pictch diameter. Let's say it is 9 inches. 9 inches x pi (3.14159...) is 28.3 inches circumference around the drive sprocket at pitch line.
28.3 /12 inches/ft = 2.356 feet per rev.

Another way would be to count the number of sprocket teeth, multiply by the chain pitch, and it should be about 28 inches per revolution of the drive sprocket.

you want 30 ft/min divided by 2.356 ft per rev = 12.7 rev/min of the drive sprocket.

If you planned on 1:1 sprocket ratio on chain drive, then all reduction is in the gear box. 1750 rpm / desired 12.7 rpm = 137 : 1 reduction.

You know what you want = 12.7 rpm. What you start with 1750 rpm. so the product of all reduction ratios in between is the 137. One or more stages as you decide.

You could use a hollow shaft reducer mounted directly on the drive shaft and eliminate some chains.
125 to 1 or more is several stages, a worm and then helical for instance in one gearbox.

Personally, I'd try for maybe 3:1 on a v belt drive at the motor to reducer, then about 45:1 on the gear box, or two v belts reduction, or one vbelt and one chain, then a gearbox.
a. It makes it easier to fine tune the speed by changing a cheap pulley, or use a variator on the belt drive.
b. by running the belt loose you have some slip clutch action if a log gets jammed.
c. easier to find cheap surplus gearboxes (surpluscenter.com, or the local agric junkyard from a baler, feed mixer, manure spreader apron drive, etc.) if the reduction ratio is not so steep.


good luck kcj