High Torque Actuator?

Greetings, I am a novice in ME and would like some advice. I am looking for a rotational actuator that can provide about 25kp-ft torque that is
accurate to within 1degree. I need to be able to rotate 60 degrees in less than 6 secs then go back to its initial position for the next rotation. It will have to run continuously for 8 hrs/day.
I know that I can use stepper motors for accuracy but will not get this much torque out of them (at a reasonable price <$1500).
Is there a hydraulic solution that can meet these requirements. Can hydraulics be controlled to stop instantly or is there a lag / back lash effect?
Any suggestions are highly appreciated.
Best,
A
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Dear amerdsp:
amerdsp wrote:

Google hydraulic "rotary actuator"
The accuracy will come from what you use beside the actuator.
...

Hydraulics can be made as accurate as you have money to spend.
Cheapest: mechanical stops with dashpots (for end of travel braking) Fanciest: 0) completely bleed air from system; 1) oil returned below reservoir level; 2) oil pumped with variable displacement pump; 3) hydraulic line length and volume kept short / small; 4) actuator controlled by proportional control or servo valve; 5) actuator position monitored by encoder, feeback loop for "stops" and "path"; 6) oil kept as cool as practical.
0, 1, 2, 3, and 6 provide minimum "back lash". 4 and 5 provide fully programmable power curve and variable soft stops at end-of-travel.
David A. Smith
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42g2000cwt.googlegroups.com:

My primary suggestion is a common one in this group, please define your design restrictions more fully. All we know is what you wrote and it is a little thin for any kind of detailed answer.
In general, 1 degree of accuracy is easily doable with a hydraulics based solution of which there are several in this case. Hydraulics can not stop instaneously, but then neither can a stepper motor or anything else. Acceleration and deceleration requirements can add much to the cost of actuator system design.
Hydraulics can get very close to ideal critical damping at high slew rates, however, the faster the stop, the more power required and the more involved the control system.
Among the additional information required are things like:     Is the torque above maximum or average?     What is the torque and time requirement on the reset rotation?     What is the complete cycle time (6 sec. actuation +hold + reset +     rest)?     What are the restrictions, if any, on the velocity profile of the     actuation and return motions?     Is there hydraulics power already available?     Do you have an appropriate electrical power already available?     Have you factored acceleration and deceleration into your torque     calc, both the load and the actuator?     How much physical room is there for a solution?     What is the design life?
This is, of course, not a complete list, but rather a suggestion of the kind of thing to start thinking about.
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Dear Charly Coughran:
Charly Coughran wrote: ...

Add emergency stop behavior, and / or the need to "lock the load mid stroke" to the list...
David A. Smith
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Charly Coughran wrote:

amerdsp-
As Charly noted
".....All we know is what you wrote and it is a little thin for any kind of detailed answer."
mechanical engineering is all about details (yeah & general concept as well)
to do good ME design you have to bounce between "the big picture" & "the details"
right now I think I know you have some sort situation where you need 25kip ft over 60 deg rotation & return
I getting the feeling that you don't have much of a budget because you mentioned <$1500
IMO you need to add a zero (at least) to that number
cheers Bob
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Try this web site for all the manufacturers of Rotary Actuators:
http://www.hydraulicspneumatics.com/Directory/DrawSpecs1.aspx
If this does not work then lokk in the "Designers Guide" at http://www.hydraulicspneumatics.com and under "Actyators Rotary"
--
Bud Trinkel
HYDRA-PNEU CONSULTING, INC.
  Click to see the full signature.
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Sure, but not for <$1500....

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Let's do the basic estimating first.
A force of 25000 lb for a distance of 2*pi*1ft / 6 in 5 seconds is what power?
25000 * 9.81 / 2.2 newtons * 2 * p i* 12 / (39.37 * 6 * 5) meters/sec = 7.2 kW = 7200/746 HP = 10 HP
Working from too little information, I imagine an 1800 rpm 15 HP motor into a 180:1 reduction gearbox to a crankshaft with a connecting rod to a secondary crankshaft whose throw is about 6? times longer than the first, so that the second crank rocks 60 degrees and back for each rotation of the primary crank.
This supposes a continuous cycling of 60 degrees. Stop/start is another matter.
Brian Whatcott Altus OK
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