QUESTION
We just received a gearbox with a chain drive ratio of 4.73:1. On top of this GEARBOX, there is a 4-speed transmission and a hydraulic motor to drive it. One of the most common combinations RPM/torque in this GEARBOX is 781 RPM / 681 FT-LB TORQUE (gearbox output)
The question is the following: when the driven sprocket is running at 781 RPM, the drive sprocket runs at 3694 RPM which seems a bit excessive considering the size of the chain and the power: torque X Speed/5252 equal to 100 HP.
This GB is mounted on a drilling truck and does not operate at this setting 100% of the time, however, there are entire days where the customer will run it at this exact settings. The customer has not had any issues with the chain or sprockets EVER, HOW DO YOU THINK THEY GET AWAY RUNNING THE DRIVE SPROCKET AT SUCH HIGH SPEED AND RELATIVELY HIGH POWER WITHOUT BREAKING ANYTHING?
You can see a similar arrangement of the gearbox here: (notice that this runs only with 80-3 roller chain but the idea is the same)
REPLIES
Pete K
Go to Tsubaki’s website and download their ANSI chain catalog…they provide a straight-forward guide to sizing chain.
In your description, you say,
“We just received a gearbox with a chain drive ratio of 4.73:1. On top of this GEARBOX, there is a 4-speed transmission and a hydraulic motor to drive it. One of the most common combinations RPM/torque in this GEARBOX is 781 RPM / 681 FT-LB TORQUE (gearbox output). The question is the following: when the driven sprocket is running at 781 RPM, the drive sprocket runs at 3694 RPM…”
If the hydraulic motor/gearbox is the driver, then the 781 rpm sprocket is the “DriveR” sprocket, not the driven. Are you sure that the chain drive is a speed INCREASING arrangement?
SOURCE
https://www.eng-tips.com/viewthread.cfm?qid=443153
Above is a snippet.