Let’s build a turntable

Discussion in 'The Academy' started by cnw1961, Nov 11, 2006.

  1. Russ Bellinis

    Russ Bellinis Active Member

    I just discovered this thread yesterday. Just for general information for anyone wanting to do a similar turntable, Micro Mark www.micromark.com offers a motorized planetary gearbox system for $34.95 part number 82722. The motor will operate on 6vdc to 24vdc at speeds from 8500rpm to 19680rpm, and it is polarity reversable. It comes with color coded, stackable planetary gear sets that reduce the output speeds to 13.8 rpm up to 6560 rpm. I've never bought or even seen one, but it looked like a good candidate for powering a turntable at a slow speed.
  2. MilesWestern

    MilesWestern Active Member

    ...I don't think it'd be fun to run a turntable at 6560 rpm!!! YIKES! :eek: sign1
  3. Bob_H

    Bob_H New Member

    Finally, a way to get those old 78 rpm records to sound like the Chipmunks...

    This is a great thread, and that's some excellent modeling. You have more patience than I do to fabricate all those zig-zags, but they sure look great!

    As for the speed, what is the normal speed of one of these? I'm not even sure 13 rpm would be slow enough, maybe.... I know prototype tables move pretty slowly. Let's see, to make the math easy I'll just say 12 rpm, that's one revolution every 5 seconds. No, I don't think I've ever seen a real turntable move that quickly, guess you'd need to do some more gearing down. Of course if you used the 13 rpm to drive a small gear powering a large gear on the turntable then you'd be fine.
  4. fsm1000

    fsm1000 Member

    Maybe it is 1.38 to 6.56 rpm?

    Anyhow, thanks for answering my questions Kurt.

    So how do you apply it then? A brush? A needle applicator?

    Also, how the heck do you clean a needle applicator?

    Thanks again.
    Of course beng busy answering us will of course take time out from modeling but... :D LOL
  5. cnw1961

    cnw1961 Member

    I found out that the right speed of the bridge for me is 1 min 15 sec for one revolution – I don’t know about the prototype, but it looks good at this speed and I don’t fall asleep. The motor is running at 40 % (1700 rpm) of its maximum speed (4250 rpm). I am glad that can keep it at this relatively low speed, because above 2000 rpm it gets noisy. The noise of a motor at high revs is an important point that one should think of when calculating the speed of the bridge, rpms and gears.

    fsm1000, that’s how you apply the glue. It comes with a needle applicator. No need to clean anything if you don’t leave it without the cap for more than a few minutes. And even then, a small wire is all it takes.

  6. Bob_H

    Bob_H New Member

    No, it's 13 to 6,000, but it's not being sold as a turntable drive, just as an electric motor with a combination of gearboxes to let you vary the speed. The main selling point is that by adding and dropping various snap on boxes, you can get a variety of speeds.

    It would still be useful for a turntable though, all you'd need to do is drive a larger gear with a small one. By selecting the right sizes, you can get the speed you want.
  7. cnw1961

    cnw1961 Member

    I don’t have much to report today. Only one picture. I painted and installed the ring rail, "detailed" the pit and finished the walkway.

  8. cnw1961

    cnw1961 Member

    Earlier on this thread I posted a picture that shows the mock-up of the control cabin. I claimed that I could do better than that – I’ll try to prove it now.

    When I scratch build a structure, I simply glue the plastic sheets for the window panes to the backsides of the walls. This little control cabin has windows on all sides and I want to build it without a door. To make it look good I have to think of a better way to attach the window panes.

    Instead of using .040" styrene for the walls, I take two halves of .020 styrene for the wall sections (except the front wall with the door opening). The openings for the windows are .040" bigger on the inner halves. This allows me to insert the window panes into the wall. I did the cutting templates on the computer.


    After I cut the parts, I glued the halves together and inserted the window panes. Then I scribed the front sides of the wall sections with the tip of a knife to make them look like wood panels.


    After that, I assembled the cabin.


    To hide the seams between the wall sections, I added strips of .013" styrene as trim to the corners.


    Now the cabin still needs to be sanded and painted, and not to forget – a roof.

  9. cnw1961

    cnw1961 Member

  10. pennsyrrfan

    pennsyrrfan New Member

    "Speaker Ring"

    Kurt -

    This is FANTASTIC! :thumb: I have read through the thread, but I don't see contact information for the "ring" vendor. It would be greatly appreciated.

    Keep up the good work.


  11. cnw1961

    cnw1961 Member

    Paul, thank you for your nice words. Sorry, but I can’t help you with the ring. I found it here while I was searching German Google for wood ring. I didn’t expect to find it at a car hifi store. I thought of something like embroidery hoops. I would be surprised if it was not possible to find something suitable in the US.
  12. Nazgul

    Nazgul Active Member

    That's about all I have to saysign1
    Although I do have a stupid question:oops: : Kurt, how do you decide on dimensions for the turntable in general and the components in particular? Like the tower height or even the styrene thicknesses. I hope I'm being clear...Taking myself for instance: if I wanted to build a simple girder bridge...I wouldn't have a clue as to what thickness styrene to use, let alone scaled down flange and stiffener plate sizes.
    thanks.....................by the way, did I already say:
  13. fsm1000

    fsm1000 Member

    Wow where do I start hmmm.
    Kurt thanks for that explanation about the glue. I know my white glue bottle tips sometime clog so I was wondering. Thanks for the photo and explanation. :)

    BobH thanks. I misunderstood obviously. I thought that was the turntable revolution not the motor LOL. Thanks for setting me straight on that. :)

    Kurt, once again you have done a great job on the turntable.

    I really do like the pit rail idea. Thanks for your photos and tutorials. :)
  14. cnw1961

    cnw1961 Member

    Hello Steve, thank you for you WOW. To answer your question: To determine the size of the turntable was very easy. The biggest turntable I can use is 90'. It has to be as small as possible, but still big enough for my longest engine.Then I found the wood ring and that settled it. From looking at ptototype photos of the Redondo turntable I knew that I wanted a shallow pit, but I needed at least .700" for the ring rail, the trucks and the deck of the bridge. The wood ring is .750" – couldn’t be any better.

    When I plan to scratch build a structure, I look at as many pictures as I can find. From known objects in the pics (engines, cars, track etc.) I deduce the size of the unknown objects. But if you don’t want to count rivets, you should always bear in mind that your model does not have to be right, it has to look right. Take the power arch of my turntable as an example. I was lucky to find some pics that show a 4-8-4 on the bridge. Knowing the length of the loco, it was easy to determine the length of the bridge and the height of the arch. But when I built the arch to the right height, it did not look right on my bridge. If you take a close look at the first pic of my bridge with the power arch in place, you will see that the arch is higher than in the pics I took later.

    To ensure reliable operation, it is important to have a sturdy bridge. I decided to use the thickest styrene I had at hand: .060". That was easy. To decide which thickness to use for braces and other details, I take a look at the prototype photos and try to choose the styrene that just looks right. But sometimes I am determined by what I can do. I think the right thickness (or the closest match) for the power arch had been 0.013". But I knew that it would make the arch too delicate. That’s why I decided to use .020". BTW, the zig-zag bracing is much to big to match the prototype, but I think no one will notice if I don’t tell about it. I hope you will keep this secret :D .
  15. cnw1961

    cnw1961 Member

    fsm1000, I am glad that I could help you, but I can’t take the credits for the ring rail. It wasn’t really me who had this idea. I can’t remember, but I read about it somewhere on the internet some time ago.
  16. Nazgul

    Nazgul Active Member

    Thank you for taking the time to reply with your very informative answer:thumb: ...I am a charter member of the "looks right" school:D and I now have a much better understanding of how to approach this type of project
    Thanks again
  17. pennsyrrfan

    pennsyrrfan New Member

  18. cnw1961

    cnw1961 Member

    Paul, that’s good news. I think you don’t mind if I add this link to the first post of this thread. :thumb:
  19. cnw1961

    cnw1961 Member

    Wiring the turntable. I power my layout with a DCC sytem and will use an auto reverser to power the bridge track of the turntable. It makes wiring a lot easier.

    I thought of using a phone plug and jack to connect the bridge track just as JAyers proposed earlier on this thread. But then I realized that I could only make it work with great constructional effort. To prevent the bridge from slipping on the center shaft, I have to glue it to the shaft. If anything is attached permanently to the shaft under the bottom of the pit, I can’t remove the bridge. To make this work with a phone jack is too much effort. Instead of the phone jack I thought of using the simple method I found on a Heljan turntable (I think Walther’s TT without indexing is the same in this aspect): two metal rings on the center shaft and two metal strips.


    It’s very easy to do, but I heard of complaints that it does not work consistently. The metal strips are the weak spot. Then I thought, why not use motor brushes instead of metal strips. If motor brushes are good enough for motors that do several thousand rpm, they should be good enough for a turntable. So I got me a pair of brushes and two springs.


    To make the housing for the brushes was quite easy. I made it of .060 styrene. In this pic it is still without the cover to see how the brushes and springs are installed.


    I glued the cover to the housing and installed it to the bottom of the pit.


    I think that should work without any problems. Now I have to find a way to attach the wires from the bridge track to the metal rings.

  20. shaygetz

    shaygetz Active Member

    That's an understatement...it's all but bulletproof, wow:thumb:

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