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What's stronger then Gear OR Chain?

  1. Nov 16, 2008 #1
    Sorry if the title is a bit blunt, but it's basically like this.

    There's this machine I'm working with.
    It's kinda using Gear + Chain to drive the output.

    Initially, they were all driven by gears but the gear is spoil every 2 months.
    So then it was changed to chain instead but now the problem is that, it's still spoil every 2 months :(

    But replacing the chain is far cheaper compared to replacing the gears so i guess it's an improvement already. But what i'm interested to improve is basically trying to come up with an idea so that it wont break at all! (At least not every 2 months)

    So any suggestions?
    I was thinking use double chains (side by side, not one on top of the other) but then it will be thicker and it wont fit in the 'container' designed for it.

    At the moment I'm thinking RUBBER BELT, but to be honest I don't know if it can transfer the full speed from the motor due to lack of friction.
     
  2. jcsd
  3. Nov 16, 2008 #2

    mgb_phys

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    There's something wrong with your setup.
    Motorbike chains last 1000s miles at high speed while being sprayed with all sorts of road junk. .Heavy duty chains take huge loads in a lots of industrial system
     
  4. Nov 16, 2008 #3
    hmmm
    but im assuming that motor setup is like this

    MOTOR -> GEAR -> CHAIN -> GEAR

    this machine is like this

    MOTOR -> GEAR -> CHAIN -> GEAR -> ROD -> GEAR -> CHAIN -> GEAR -> CHAIN (This is the one that keeps breaking every 2 months) -> GEAR

    (Sorry if i can't give a better picture)
    (Don't have camera and scanner atm)
     
  5. Nov 16, 2008 #4

    mgb_phys

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    The chain is either the wrong profilefor the gears, is installed with the wrong tension, isn't lubricated properly or there is some very nasty stuff in your enviroment.

    Does the system stop and start with high torque frequently? That isn't good for chains
     
  6. Nov 16, 2008 #5

    russ_watters

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    ...or just plain isn't strong enough for the application, in which case you simply need beefier gears and/or chains.
     
  7. Nov 16, 2008 #6
    Well i think the lubricant is good enough

    I mean, we can always change the solution to direct drive.
    Motor -> gear

    But i'm trying to look for other alternative at the moment.

    If i need 'beefier' gears or chain, then i think this
    falls under 'material engineer' instead of 'mechanical engineer'

    And yes, the system stop and start with high torque frequently. (No choice)
    But there's this sensor installation that speeds it down and also builds up the speed when it starts. (Not DIRECTLY speed up and DIRECTLY stop from high speed)
     
  8. Nov 16, 2008 #7

    mgb_phys

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    Good point - I assumed whoever had built it knew what they were doing !
     
  9. Nov 17, 2008 #8
    ummm in that case,
    may i know what's the STRONGEST chain material out there
    in market?
     
  10. Nov 17, 2008 #9
    Where is the highest rpm in your drive system? Is it at the motor end or the output end where the chain is breaking? I’m trying to determine if you are using a high torque motor to drive a high speed gear, or a high speed motor to drive a high torque gear. If it is a high torque output, it could be the chain is just not strong enough, as Russ has said, or the torque being generated is not enough to do the job, in which case something has to give! But, if you are driving the chain and gear at high rpm, it may just be a misalignment problem. I would do a vibrational analysis to check alignment. If you just keep putting in a stronger and stronger chain, the drive system will just fail somewhere else.
     
  11. Nov 17, 2008 #10

    russ_watters

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    It's not a materials issue, it is about selecting physically larger gears/chains.
     
    Last edited: Nov 17, 2008
  12. Nov 17, 2008 #11

    FredGarvin

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    This is exactly an Mechanical Engineer's job. You need to look into who specified and sized the gears and/or chain for the service it is in. It is pretty apparent that you either have a serious misalignment issue or the components are undersized.
     
  13. Nov 17, 2008 #12
    This is a hard lesson to learn. I learned it the hard way. :smile:

    As Fred suggested, I would first check the alignment. At high speeds/torques, bad alignment can kill chains pretty quick. Can you tell us any of the specifications of the machine? Such as the torque and speeds being inflicted on this chain?
     
  14. Nov 17, 2008 #13

    Danger

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    Keep in mind, as well, that there are three kinds of alignment. The first, as Mgb mentioned, is that the profile of the teeth matches that of the links. The second is that the distance between the gears matches the pitch and length of the chain. That can be altered by an adjustable tensioner. Lastly, the circumferences of the gears have to be in the same plane and parallel to each other to minimize side-stress on the chain.
    Along that line, are you sure that all of the gear-shaft bearings are in good condition? One that's worn can cause the gear to wobble enough to accelerate chain wear even if it's not readily visible.
     
  15. Nov 17, 2008 #14
    I actually most note that I work in Jakarta.
    There is no 'official testing' in a sense that we know what's the tension level or such.
    We just make do with whatever's given here :(

    So it's just, design, implement and see the progress.
    Of course in this case, our 'testing phase' is only proven 'theoretically' wise.
    Like, theoretically, THIS design should be stronger.
    We don't have any apparatus to test whether it IS stronger or not,
    we just put it to use and run the thing and see if it performs as we calculate it to be~

    I'm actually now trying to find a more 'sturdy' way of designing the gear~
     
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