Critical sped for vertical shaft
Critical sped for vertical shaft
(OP)
Hello,
I have a problem as shown in attachment,here a vertical shaft is powered by a motor.
at the top of the shaft a circular disk is fixed weigh approximately 3 kg.
the shaft runs at 3000rpm and motor power is 0.75 hp.
Iam intrested to know the critical speeds within the working rpm range.( first ,second and may be more critical speeds).
i would be obliged if somebody helps out.
regards,
aftab
I have a problem as shown in attachment,here a vertical shaft is powered by a motor.
at the top of the shaft a circular disk is fixed weigh approximately 3 kg.
the shaft runs at 3000rpm and motor power is 0.75 hp.
Iam intrested to know the critical speeds within the working rpm range.( first ,second and may be more critical speeds).
i would be obliged if somebody helps out.
regards,
aftab





RE: Critical sped for vertical shaft
You want the sweep to be fast enough to not linger at an area that is resonant and who's amplitude will grow to destruction but you also want the sweep to be slow enough to see the effects of resonance to find the speeds. Start with a fairly fast sweep and if nothing is seen slow it slightly. Step and repeat.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Critical sped for vertical shaft
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Critical sped for vertical shaft
the motor is DC motor and for this application i need to vary the speed.
By varying the speed, the resonance seems to appear at 600-700 rpm.After sweeping these speed range motor runs smoothly.
as the speed reaches near 2700 rpm, vibrations are too much but not as much as near 600 rpm range.
practically i know what may be the critical speed range but I need to know the results in theory.
it's better you state what assumption Iam lagging or data which I didn't specify for the calculations.
regards,
aftab
RE: Critical sped for vertical shaft
thanks.
aftab
RE: Critical sped for vertical shaft
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Critical sped for vertical shaft
i had that in my mind but here i don't have equipment to check balancing.
is there any other method to check balancing.
aftab
RE: Critical sped for vertical shaft
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Critical sped for vertical shaft
thanks for help
RE: Critical sped for vertical shaft
or if you have a complete, updated finite element model, you can use SSD to find critical speeds.
RE: Critical sped for vertical shaft
RE: Critical sped for vertical shaft
this method generate critical speeds and critical domain after calculating eigenfrequencies.
This is Finite Element and you need experimental investigations to validate and update your model.