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Doltec Limited
Rigg Lane
Trent
Sherborne
Dorset
DT9 4SS
England
Telephone: +44 (0) 1935 851 034
E-
The Craig Test
Flat Tape between gearbox and roll shafts
The CRAIG Test (created by one of our customers)
1. Remove a drive shaft from any convenient roll pass.
Initially we suggest a breakdown pass.
2. Attach a length of flat tape between gearbox output
Flange and roll shaft (Photo left).
3. With strip in the mill, run the mill for one or two
minutes and observe the tape.
4. Replace the drive shaft and carry out the same test
on another shaft.
If the Tape does NOT twist, you DON’T need
CyberDrive
The object of this test is to demonstrate that however good the roll design, there is always some linear speed difference between rolls due to variations in material thickness and tensile strength which produce changes in Drive Points. These variations create roll wear, distortion and marking of product, and an increase in drive power.
The CyberDrive system fixes the problem.
One customer in the U.S.A. tried the Craig Test and, despite having new rolls of the ‘latest design’, the tape rolled up almost as soon as the mill started when attached to the top roll of Breakdown Pass 4. It happened so quickly he decided to measure the shaft speeds and found that when making 2.75” diameter tube, the gearbox shaft was rotating at 55 rpm and the roll shaft at 55.4 rpm. On the same shaft but with rolls for 2.382” diameter tube, the gearbox shaft was rotating at 40.6 rpm and the roll shaft at 43 rpm.
If you think this is crazy -
Another customer tried the the CRAIG Test on a fin pass.
The tape wound up 720º in 15 seconds!
The reason the tape twists is that the chosen roll is freely running at strip speed, not ‘driven speed’.
CyberDrive couplings allow each roll to rotate at the speed of the strip and eliminate the stresses, wear, and marking created by speed mismatch.
Why not check your mill NOW -