Our reply:
We used an calibrated pulse counter to count the number of rotations and taps per minute. The actual results are 265 rpm and 147 taps per minute.
Haver&Boekcer has let us know that, although their specs have a +/-10 rpm tolerance, in practice the device has an exact rpm rate of 278. Their device isn't actually their own design, but simply the WS Tyler Ro-Tap 8'' RX-29. They also sell the exact model you have with the same specs.
Your test results show that the remark of Haver&Boecker is actually not correct: you have measured 281 rpm, an deviation of plus 3 rpm from the specified 278 rpm. Would this be minus 4 rpm, your machine would not have met the SAE J444 specs, although it would still be within the manufacturer specs.
The whole point of our questions is that the SAE J444 (and AMS 2430) specs for sieve shaker do not seem to reflect *any* product on the market. Even the tolerances of the original WS Tyler Ro-Tap do not comply with the J444. There seems to be no rationale which clarifies on what basis these J444 requirements were determined.
Do you feel that your test results would be different when the J444 requirements would be less stringent, say 250-300 rpm and 140-160 taps per minute?
And what is your opinion about the significance of characteristics like tapping force or oscillation amplitude?
(name withheld)
