Sizing a motor

Discussion in 'The Projects Forum' started by gfgenefitzgerald, Feb 7, 2011.

  1. gfgenefitzgerald

    Thread Starter New Member

    Oct 4, 2009
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    [SIZE=+0]Hey There,[/SIZE]

    [SIZE=+0]I'm just starting of on a project which involves wirelessly zoning a radatior based heating system. A time clock will wirelessly communicate with a motor that I will be creating that shall be able to be retrofitted to the valve as a means of opening and closing it.[/SIZE]
    [SIZE=+0]My plan is that the system should eliminate changing pipe work needed to zone a system into smaller zones.[/SIZE]
    [SIZE=+0]My problem is that I need to size a motor that will be capable of opening and closing the exsisting valve. I was thinking that i needed to measure the torque It took to open the valve with a torque wrench.. Would this be the right approach to sizing? Once i got this value i was planning on using a servo motor to open and close the valve so my system will be battery operated... for the moment 12 volt is as big as im going, any suggestion on this motor sizing problem, and any tips in this area would be brilliant[/SIZE]
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I'd consider using a new valve, one that is meant to be controlled electrically. I'm thinking of the solenoid valve in my dishwasher. Anyway, this may be simpler overall than trying to turn a mechanical valve.
     
  3. gfgenefitzgerald

    Thread Starter New Member

    Oct 4, 2009
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    Hey thanks for the your reply!
    The very concept of the project is zoning an exsisting radatior system without the need to alter the plumbing at all, and the project is kinda set in stone at this stage too.
     
  4. wayneh

    Expert

    Sep 9, 2010
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    OK, well spend some time Googling for valve turning mechanisms. It may be a challenge to find the right search terms, but anyway I have seen such things used industrially and it would really make design simpler to start with a working strategy.
     
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  5. John P

    AAC Fanatic!

    Oct 14, 2008
    1,634
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    The torque wrench sounds like a good idea. But by "servo motor" I hope you don't mean a model aircraft servo; those things have tiny motors and light-duty gears. You most likely need a gearmotor with significant output torque. Something like these:
    http://www.jameco.com/Jameco/catalogs/c103/P111.pdf

    But then, if you use a geared d.c. motor, how will you get position feedback? Got to plan these things in advance. This is not a totally trivial project.
     
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  6. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    Plenty of HVAC and industrial flow control are based on what your describing. Valves range in design and can be integrated smart controls with PID built in, or simple 'run on command'. You would have the right approach using the torque wrench, but consider the life of a choosen valve. New, it will turn smoothly but after a bit of life it may well take more torque, which you may want to accomodate. With your determined torque, you'll then want to consider speed of operation, which leads you to general motor sizing. Closed loop positioning may be required, but simple open/closed may also suffice.
     
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  7. gfgenefitzgerald

    Thread Starter New Member

    Oct 4, 2009
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    I've checked out the motor page you've posted and from the guesswork Ive been doing without using a torque wrench (Cant get my hands on one until tommorrow) Ive seen on a quick search that hand tight is about 20 nm of torque, the motors you've shown me seem a little small after Ive converted them to nm, the idea with the servo motor is eaxctly what you had said about position feedback. Again I'm doing a little guesswork on this but I would of guessed that you can get servo motors up to a fearly large size. Im taking other factors into consideration also, as another poster had said conditions will change with time and also with Temp and also when the head of water is running from the circulating pump so the motor that i will choose will def have to be over sized to make sure that it will opperate.

    Again everybody thanks for your input I'm learning plent here!!:)
     
  8. gfgenefitzgerald

    Thread Starter New Member

    Oct 4, 2009
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    I'm interested in the use of HVAC and industrial flow control, I'm going searching on this for a while to see if i can locate a bit of nice info.

    and i def want some sort of closed loop system, It would add value to my project, and when talking of speed, Low speed high torque would be preferable
     
  9. gfgenefitzgerald

    Thread Starter New Member

    Oct 4, 2009
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    This cant be right... hand tight must be way less???

    About 10 nm...?
     
    Last edited: Feb 7, 2011
  10. wayneh

    Expert

    Sep 9, 2010
    12,153
    3,059
    Depends on whose hand you're talking about!
    You really should use Nm or N•m. nm is nanometers to most folks.

    Are the existing valves gates (probably) or butterfly? Butterfly and ball valves are handy because they go from off to on in a predictable 90° of rotation. Gate valves can be predictable but you need to find out how many turns end-to-end.
     
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  11. gfgenefitzgerald

    Thread Starter New Member

    Oct 4, 2009
    6
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    Yup gates alright...!

    yea your right I should use the right terminology.. Nm

    will be getting my hands on a torque wrench tomorrow so my torque guessing will be answered but the reason for the handtight question is that I wanted an aprox idea of the range of the torque wrench i would need.

    :D
     
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