Large Scale Central

Turntable Drive

Electronics Power and Sound
#1

Has anyone built a powered turntable drive? If so, what kind of motor/gearbox did you use?

I’m working on a drive for a turntable, the primary axle for which will be a tube about 1/4 inch in diameter attached to a plate secured across several ties at the center of the bridge, and driven from underneath. On my current course, I’m going to have to attach a gear to the tube and drive it with a gear motor turning a smaller gear than the one on the tube…

What is an acceptable rotational speed for a turntable like this? I’m shooting for 1-2 RPM … too fast or too slow?

I would also be interested in seeing what various turntable locking mechanisms looked like (prototype) … I’m going to have to have one, and wonder how a “real” 60 foot gallows turntable would lock into place.

Matthew (OV)

Oh, by the way … this is in Power/Sound primarily because I’m interested in the motor and gear train for the table … the lock was an afterthought. Sadly, the table’s not quite close enough to the operator to be reached comfortably, so Armstrong is really a last resort, and would require a pole and hook to operate it.

#2

Hm. After a lot of researching gears, power window motors, and the like, I think I’ve settled on the idea that I’m going to make it a true Armstrong table, turned via a wheel under the benchwork. Much less likely to break down … though I still need a good locking mechanism for the “Big Wheel” … perhaps a simple locking pin?

#3

Matthew ,
I think you asked the wrong question , or asked the right one the wrong way . I was put off answering because you seemed to have already made up your mind as to how to go .
There is nothing intrinsically wrong with a hand operated wheel turning a shaft with worm and wheel , the speed is then a bit immaterial because it will go as fast or as slow as you turn it . The problem of locking into position is a different kettle of fish . It will rely on accurate pinning of the turntable itself , not the remote winder for obvious reasons . But that is not to say that a remote lock will not work .
Start from a simple extended bolt mating with holes around the periphery of the table where convenient . Bring the operating part of the bolt out to where you can easily access it . Consider some form of lock to prevent accidental operation . Start simply and make it as complex as you wish , a fully automatic indexing table is nice , but once the novelty has worn off , maintenance and set-up costs may rear a ugly head .
Enjoy working it out , bounce ideas into the forum–someone must have tried something similar to anything you are likely to come up with .
Have fun ,
Mike

#4
Matthew (OV) said:
Hm. After a lot of researching gears, power window motors, and the like, I think I've settled on the idea that I'm going to make it a true Armstrong table, turned via a wheel under the benchwork. Much less likely to break down .... though I still need a good locking mechanism for the "Big Wheel" ... perhaps a simple locking pin?
Matt,

You’re on the right track!

Having an index plate mounted to the shaft with notches the slopes of which are just steep enough and deep enough to keep the turntable in proper position. The “positioning pin” is akin to a ballpoint pen, but uses a spring loaded ball from a ball bearing which fits in the retainer tube and engages the notches. The spring pressure is sufficient to keep things in place but not too great to move the table by hand. If you have a worm-wormgear drive with a hand crank that will be as KISS as it gets, but still very accurate. The retainer/plunger is mounted as an adjustable subassembly to allow precise alignment.
Let me know if you need a basic drawing.

PS I have to build one of these for outside this coming winter. It will be Armstrong, completely selfcontained (mount and remove the whole shabang as a unit!), have industrial grade ballbearings and most of the components will be alumin(i)um. Basically it’s the standard EMM design, scaled up and beefed up for 2m and outside service.

#5

Matthew, Here are a couple of pictures of my powered turntable. It is accully powered by two Lionel F-3 motors and gear boxes. One at each end of the span. And it turns on a 4’ diamitor track. I did not need a locking mech. because I can slow the motors down to line up the tracks and once it is stopped the motors keep it in place. The span is 42" long and will turn my 40lb USA Hudson with ease.

Thanks Rex

#6

Rex, it looks like you are having wayyy too much fun there!

I’m guessing your layout is indoors, have you ever posted a track plan? (Of course I might get sick with envy!)

Regards, Greg

#7

Greg, Actully this turn table was built for a portable train layout. I haven’t worked on it in awhile other than taking pictures on it, like the picture below. It is stored and covered up outside on my padio. The round house you see in the background was destroyed in the trailer on the way to the MWLSTS two years ago. load shiffed and crushed it. I’m trying not to have too much fun until they fix my ruptured disc. I have been trying to take it easy, but I do work on trains 2-3 hours a day. Thanks Rex

#8
Hans-Joerg Mueller Having an index plate mounted to the shaft with notches the slopes of which are just steep enough and deep enough to keep the turntable in proper position. The "positioning pin" is akin to a ballpoint pen, but uses a spring loaded ball from a ball bearing which fits in the retainer tube and engages the notches. The spring pressure is sufficient to keep things in place but not too great to move the table by hand. If you have a worm-wormgear drive with a hand crank that will be as KISS as it gets, but still very accurate. The retainer/plunger is mounted as an adjustable subassembly to allow precise alignment. Let me know if [b said:
you[/b] need a basic drawing.
Very interesting, Hans..... and I'm hoping you'll tell me that you have good luck locking the table via the center axle rather than at the ends..... I was afraid the force at the end of the table would have enough leverage on the center axle (1/4 inch in my case, attached by a plate to the center several ties) to torque the rails out of allignment.

Man, that roundhouse … are those ALL hudsons in there?

#9

The far right locomotive looks to be the only Hudson. #'s 1 & 3 appear to be Mikados based on the fact that they have a freight pilot and 2 & 4 are possibly Pacific’s. None appear to be his Northerns. They would have a regular pilot and a silver face. The only silver faced locomotive is #3 with the freight pilot.

Just my guess,

Warren

#10

Warren, Just bad lighting, You are close. #1 is a Mikado, #2 & #4 are Pacifics, #3 is my early made Nothern and #5 is the Hudson. But right now if I did another picture it would be hard to tell because I have 4 Northerns sitting here right now. The two silver face ones are mine and I have two black face ones I have built for other people on east and west coast. Here is a picture of the one going to California soon. Thanks Rex

#11
Matthew (OV) said:
Hans-Joerg Mueller Having an index plate mounted to the shaft with notches the slopes of which are just steep enough and deep enough to keep the turntable in proper position. The "positioning pin" is akin to a ballpoint pen, but uses a spring loaded ball from a ball bearing which fits in the retainer tube and engages the notches. The spring pressure is sufficient to keep things in place but not too great to move the table by hand. If you have a worm-wormgear drive with a hand crank that will be as KISS as it gets, but still very accurate. The retainer/plunger is mounted as an adjustable subassembly to allow precise alignment. Let me know if [b said:
you[/b] need a basic drawing.
Very interesting, Hans..... and I'm hoping you'll tell me that you have good luck locking the table via the center axle rather than at the ends..... I was afraid the force at the end of the table would have enough leverage on the center axle (1/4 inch in my case, attached by a plate to the center several ties) to torque the rails out of allignment.

Man, that roundhouse … are those ALL hudsons in there?


Matt,

The center axle (through the ball bearing) on the HO version measures 30mm (1.181") and 20mm where the disc mounts.
BTW I designed the first of those turntable assemblies for a friend who had nothing but trouble with a commercial one that used a 1/4" shaft, a simple sleeve bushing/bearing etc. etc. :wink:

Of course you can also use the plunger for each lead that comes of the turntable, easier to lay track since you adjust the separate plunger assemblies. However you need a large disc, more plungers and unless you design very carefully you need to mount the parts individually.
Personally I like the “adjust everything on the workbench and then install as a unit” routine. :wink:

#12

I suppose now the trick will be to find a worm gear/round gear/crank assembly I can salvage from something to actually move the mechanism… probably a lawn mower, snow blower, something…

Matthew (OV)

#13

Matthew ,
Try a loco gearbox . Think of the mechanics of what you are trying to do . You have a more or less balanced loco on a turntable .All you are trying to do is turn it against the inertia of its weight . A loco gearbox does this , so should be man enough for the job ,especially given its likely usage—compared to its life as a loco unit . I take it you are trying to do it without sourcing special bits , you may even have a semi defunct loco somewhere that will do . The gearing down will make
hand operation steadier . Also think about whether or not you need the table to go 360 deg . Generally , it is not necessary , so you can hard wire the power to the table tracks and not worry about twisting them off .
In general , with modelling , a bit of lateral thinking can help .
You may have seen my Railbus .
I needed a small motor to have the drive hidden and not showing up into the passenger compartment . It took a little while to realise that the Railbus is very light , won’t pull trains ,and weighs less than an O gauge loco , which is what the motor/drive was intended for . So I now have a power/drive unit which is standard and thus able to be serviced . You can tell its not working very hard by the delrin chain drive .

#14

Matthew:

Along with Mike’s excellent suggestion that small, lightweight and simple will suffice, take a look at Tamiya’s gearbox and motor combination kits. Their Techno Series is aimed at experimenters with small motion applications for items such as your TT. They come in a wide variety of configurations and typically have the ability to be assembled with varying gear ratios (up to ~3000:1). They would have plenty of power to run the TT. Some are differential types for vehicle applications, and are not suitable for the TT. Tamiya also have a line of hard contact type and non-contact type position detection switches that are compatible with the gearmotor drives. I see them available in hobby shops and at on-line hobby and robotic suppliers with prices ranging from $5 and $25 for the complete kit.

Hope this helps.

Happy RRing,

Jerry Bowers

#15

Jerry ,
Right on the button . I had forgotten them , and actually have a couple lying round somewhere , one of those “might be useful” buys . Good thinking .
Mike

#16

Excellent information. As you can see, I tend to overbuild EVERYTHING … so I’m going to have to rethink some things here, and maybe downsize the mechanical end a bit.

#17

Matthew (OV),
Check out the specials area within the Hartland Locomotive Works website, motor with gearbox and wheels for only $25.00. Hope this is a help.
Good Luck,
Ron