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need some ideas on this one

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  • need some ideas on this one

    While I have been testing the On30 waters, trying to figure out if I want to change scales, I have decided to build some models just to see what I can do with On30. What got me interested in O narrow gauge was a book that a friend let me look at about the Mann Creek RR. I decided for fun to build a Mann Creek hopper just to see what it would be like. about half way through building the hopper I got the idea to make it actually work, with doors that open and close. Then I thought that maybe I could make it work hands free by making a mechanism that would open and close the doors. I had the idea to use a plunger type mechanism when pulled down the doors opened, but I could not design one that was simple enough to be repeted many times (if I decided to go this route) and open the doors far enough.

    so far what I came up with was a T bar that had to rods that connected to the doors. When the T bar is turned it pushes the doors open, which is important that the doors are pushed open because I found that the coal is not really heavy enough to force the doors open on its own (as the coal empties there is not enough force or weight to hold the doors open). The T bar works great because it opens the doors wide enough and it is really easy to make. I used a spring clip to hold the doors shut. For now I just pressed on a C channel of brass connected to the T bar and placed another T bar centered in a test track. To open the doors I just spot the car over the T bar in the track, raise the T bar into the C channel on the car and turn it 90 degrees. But, if the hopper car is not spotted centered over the T bar in the rail the axis of the T bar on the car and the one in the rail are out of alignment and the car can move or tip or just not work right. precise spotting of the car would make it a tedious job and would get tiring. I want to make it so it only requires getting the car close to where it needs to be but it does not have to be exactly in a specific spot.

    This might be a crazy idea but I tought of using a small motor and a worm drive to open the doors. I could use a DCC decoder to drive the motor (which I have plenty laying around once I switched to Tsunami decoders). The trouble I am having is that the motor needs to be small enough and slow enough that it is controllable. I also thought about using a small RC servo that I could rewire to a DCC decoder.

    Anyone got any other good ideas. The goal is to keep it simple enough to be repeated and to use easy to buy parts. Cost is not too much of a problem because I would not need a huge amount of these cars if I was to ever build a layout of that used these cars. The nice part about using DCC and a motor is that as long as the car is over the dump pit it can be dumped. I could just use one of my spare UT1 throttles to dial up the car number and operate the doors.

  • #2
    Nice engineering of the dump mech. In a simialr fashion what if you used a shape to push the rods to the side? Car would have L instead of C channel with springs to push to center/closed position. would push them out against the springs. Just thinking while sitting in Senate Gallery waitng for them to raise taxes.

    Bill Uffelman

    In Carson City NV for a few more days


    • #3

      Very cool dump car.

      I have always wanted to try to use a small RC car like the radio shack zip zap for something in a model rr. I bet you could get them at garage sales for a buck or new for around 10 buck.

      Thought would be to use the front wheel mechanism from the car to move the push bar right / left or center. The cars are rechargeable so you could use the batteries to drive the servo and not have to worry about dirty track. The issue would be the number of RC frequencies available may be limited to two or three.

      Good luck I will be watching with great interest.


      • #4
        What a great bit of engineering!!! Really cool!


        • #5
          I can't help on the mechanism question, but let me tell you that this is a fine model!


          • #6
            Years ago I used to work on Foxboro proces control equipment, one of their products was the 'Spec200' controlstation line.

            It used a special kind of wire called 'Nitinol' and I saw some references to this kind of wire (I think...) as 'memory wire'. Needs some heating up from a smal heating element, fed perhaps through 3rd or 3rd&4th rail. It's slow and quite strong, we used a 1 lbs weight to test it.

            Dunno if and where it's for sale, just a thought.

            Not sure, perhaps you'll have to swap the 'open' and 'close' captions, the wire gets longer when heated.

            Great piece of work !

            cheers, Leo.


            • #7
              Had a look in the boss's junk room, couldn't find a single Nitinol drive, but I got a few more irons in the fire.

              Thinking back, I don't think you'll need a heating element, just send a current trough the wire, makes it even more practical. I'm not on par with DCC (yet), but perhaps the light function could be used to switch the current on and off, no need for extra feeder rails !

              cheers, Leo.


              • #8
                you might be on to somethng with the wire idea. I'll try to see of I can buy any from some where.