Looking for info on commercially available, automated turntables...

[DKS]

https://www.therailwire.net/forum/index.php?topic=39946.0

Check out reply #4 on this thread.

Al Hooper

Not meaning to be critical of your work or anything, and it's cool that it functions well, but that turntable looks like it's being rotated by a rubber band. It's kind of herky-jerky in its movement. Or is that a function of the video?

[alhoop]

I am loving the stampede toward "low tech" on this.   
And YES... hand crank.  Why not?

"low tech" yes, but the simpler it gets the more workarounds are
required/suggested, some of them quite dangerous.
Al hooper

[alhoop]

Not meaning to be critical of your work or anything, and it's cool that it functions well, but that turntable looks like it's being rotated by a rubber band. It's kind of herky-jerky in its movement. Or is that a function of the video?

You are right - it does look that way - I never noticed it until I went to full screen. I can assure you that the tt moves as smooth
as the proverbial babys B--- so it must be our lying eyes or the video frame rate or ??
AL Hooper

[DKS]

You are right - it does look that way - I never noticed it until I went to full screen. I can assure you that the tt moves as smooth
as the proverbial babys B--- so it must be our lying eyes or the video frame rate or ??
AL Hooper

OK, sounds like a frame rate issue then. Good!

"low tech" yes, but the simpler it gets the more workarounds are
required/suggested, some of them quite dangerous.
Al hooper

"Dangerous"? Do tell!

[Maletrain]

Regarding the hand-crank idea: My experience with hand cranks is that they have lots of lash, and would need some sort of latch to hold the bridge end in place when stopped in alignment with a track. 

A decent high reduction gear train on an electric motor doesn't seem to have that problem. 

But, the connection of the gearbox output to the bridge shaft would need to be rock solid. 

I am considering using a stereo phonograph plug for my bridge pivot, so that I can wire the tracks through it.

Has anybody done that with a gear reduction motor.  If so, how did you decide to set it up?

[Mark5]

Not meaning to be critical of your work or anything, and it's cool that it functions well, but that turntable looks like it's being rotated by a rubber band. It's kind of herky-jerky in its movement. Or is that a function of the video?

This is a common Youtube issue.

[peteski]

One other nice thing about a non-indexed TT is that you can locate any number of fan tracks at any arbitrary angle(s) anywhere around the pit to suit your particular needs. You're not locked into whatever the mechanism affords--which may not work with the roundhouse/facilities you're modeling.

The nice thing about Walthers turntable is  that it "learns" the indexing, so when you install it at first, there are not constraints as to locations of the tracks.  After all, that is what its fancy microprocessor controller is for.

[DKS]

The nice thing about Walthers turntable is  that it "learns" the indexing, so when you install it at first, there are not constraints as to locations of the tracks.  After all, that is what its fancy microprocessor controller is for.

Just more sh!t to break down...

[alhoop]

This is a common Youtube issue.

Thanks!
The original was shot with a Panasonic DMC-FZ30. I just did a short video
using Samsung Galaxy and the TT movement is still as smooth as the proverbial ----.
I'll post it if there are any non-believers.
Al Hooper

[alhoop]

OK, sounds like a frame rate issue then. Good!

"Dangerous"? Do tell!

Yeah this thread is a lot of fun - one sez he  has to stand on a step stool to select certain tracks. I'm
reminded of Model Railroader cartoon of years back of a guy falling through a mountain doing that.
I guess nowadays one could use a drone especially if the tt is in the far reaches of the layout - nah that's hi-tech.
AL Hooper

[Ed Kapuscinski]

What about small "stops" like the pointer on a carnival wheel that will keep it aligned when you get close enough but can easily be over powered when you need to move it?

[alhoop]

id. 

I am considering using a stereo phonograph plug for my bridge pivot, so that I can wire the tracks through it.

Has anybody done that with a gear reduction motor.  If so, how did you decide to set it up?

My first tt was the Hejlan 120' which I powered with a 0.9 degree stepper motor with the steps further divided
by 4. Some tried to convince me it was smooth but it was quite disconcerting to see a prized loco being jerked around.
I got bridge polarity reversal by using a brass tube as the tt center post  with a wooden insulating dowel in the center
of the brass tube with extensions of the brass tube wall on each side which my bridge power wipers rode on.
 I also got(using a Stamp II) rudimentary track selection by counting steps between selected tracks.
While it worked very well the Walthers TT was much better.
Al Hooper

[DKS]

What about small "stops" like the pointer on a carnival wheel that will keep it aligned when you get close enough but can easily be over powered when you need to move it?

This is what I did on one of Rick's turntables. Took a sheet of 1/4" Plexiglas, traced out a circle, marked it with the track centers, drilled those points out with a 1/4-inch drill. Then cut the main circle out of that, leaving indexing depressions around the inside of the ring. Below the pit, attached an arm with a spring-loaded 1/4-inch roller on it to follow the ring. As a bonus, I put a microswitch at each index point, so when the roller dropped into the detent, it closed the switch and energized the corresponding track. All of this had to be built before laying the fan tracks, so that they could be precisely aligned with the bridge track when it was locked in a detent position.

Also rigged up a wiper system on the main spindle that fed the bridge track to reverse polarity when appropriate. It was just two metal rings split in half on the spindle, and two wipers. The split rings were wired opposite one another.

There's one drawback to this design: the bridge doesn't turn smoothly--it pauses briefly at each track.

[DKS]

I am considering using a stereo phonograph plug for my bridge pivot, so that I can wire the tracks through it.

Has anybody done that with a gear reduction motor.  If so, how did you decide to set it up?

Most of those phono plugs are too mechanically sloppy to maintain good alignment.

If you're going DIY with a bridge drive, I strongly recommend using two ball bearings and a shaft of 1/4-inch minimum. Sounds like overkill, but it'll never give you any trouble.

As an alternative, if you have an old record player, many of them have a robust platter bearing that's useful. A friend actually used the platter itself mounted upside down as the pit...

[mmagliaro]

Regarding the hand-crank idea: My experience with hand cranks is that they have lots of lash, and would need some sort of latch to hold the bridge end in place when stopped in alignment with a track. 

A decent high reduction gear train on an electric motor doesn't seem to have that problem. 

But, the connection of the gearbox output to the bridge shaft would need to be rock solid. 

I am considering using a stereo phonograph plug for my bridge pivot, so that I can wire the tracks through it.

Has anybody done that with a gear reduction motor.  If so, how did you decide to set it up?

I have to give you another thumbs down on the 1/4" phone plug idea.   It was very popular back in the day for carrying the bridge current, but it's too sloppy.  I agree with DKS... two precision bearings with a snug-fit shaft.
As for the gear motor... when I did it with the old Bowser turntable, the turntable has a round plywood disk underneath that rotated on the bearing.   I mounted my gearmotor to the benchwork with a small drum with a rubber tire on it (no idea where I got it... it's been years... I think I made it).  The motor was mounted so the rubber tire rode on that plywood disk, so as the motor turned, it rotated the turntable.  With the big gear reduction and the rubber tire friction drive, there was zero backlash.
If I were doing it today, I'd buy a ready-made machined round disk of aluminum (you can buy these cheap on eBay).  The plywood disk was too sloppy (probably just cut out by somebody at Bowser on a bandsaw or with a jigsaw), so it had little dips and bumps in it that I had to sand out, and I still had to spring-load the motor mount so that it could bob in and out a little to keep the rubber tire in good contact with the disk.