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  • Rules clarification

    We have read the rules and read the can and cannot put on the robot. We were brainstorming and came up with an idea that involved bike chains. The rules stated we could use #25 half length chain. Could someone clarify this to us that this is a normal bike chian or something else.
    Thanks
    Team 2003656

    **Admin Note: Questions about the game should be posted to the game forum for an 'Official' response**
    Last edited by JoAnn; 09-21-2010, 01:48 PM.

  • #2
    Standard bike chain is usually #40 if memory serves me correctly. #25 is a smaller size chain. McMaster is a nice supply of the chain as well as half links and master links. Here's the link http://www.mcmaster.com/#ansi-25-roller-chain/=8y3v7o.

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    • #3
      #25 chain is 1/4" between centers and is available along with other TETRIX parts here:

      http://parts.ftcrobots.com/store/def...D=172&by=9&c=1

      Use this link to get 20% discount for being an FTC team.

      Phil.
      Last edited by FTC2818; 09-22-2010, 03:11 PM.

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      • #4
        Thanks for the replies! We cheched 2010FTC2818's link and the chains are good, but it doesn't state the diameter of the sprockets. Anyone know the diameter for each of the each of the different sprockets?

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        • #5
          Originally posted by TrojanHorse View Post
          Thanks for the replies! We cheched 2010FTC2818's link and the chains are good, but it doesn't state the diameter of the sprockets. Anyone know the diameter for each of the each of the different sprockets?
          I can find out in a day, but some basic math would get you pretty close.
          Look at the pictures and count the number of teeth.
          Multiply by 0.25 (pitch) and you have Circumfrence (at the mean pitch).
          Divide by PI and you have Diameter....

          See, math really is usefull

          Phil.

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          • #6
            Half Link

            I believe the rules say you can use a "half link". http://en.wikipedia.org/wiki/Bicycle_chain is the website chain on wikipedia. Chain is an interesting power transfer device. I believe the chain that you can buy from the LEGO Tetrix site is a standard # 25 chain. The use of chain in machinery is quite common when you do not want any possibility of slip. To get the chain to tension properly you need the correct number of links. A "half link" helps you get the length of the chain more correct for your application. Mechanics who work on farm machinery or other types of machinery with belts, pullys, gears, chain, etc. are often very familuar with the variuos issues involved in power transfer. Correct pully, gear, or sproket alignment, correct tensioning of the chain or belts, etc. is all very important. The chain we bought from LEGO did not come with a half link when we purchased it last year. We purchased the half link from an outside source so we could get our chain closer to the appropriate length. Chain tension is very important if you are using chain. If teams do not have someone knowledgeable in power transfer they might want to contact a farm machinery dealer and see if there is a mechanic that can share some interesting insights. It might be interesting to visit a machinery dealer and have them show your team various methods to transfer power.

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