Pola G scale turntable

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yb281

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Over the last few weeks I've been helping a mate to install a Pola G scale turntable in his engine shed area. This has all gone OK as far as actually building the kit, installing the electrics for rotation and securing the tracks is concerned, but the means of getting power to the actual turntable tracks via the supplied brass wiper contacts has been a nightmare. In fact, today we binned them.

I've come up with a temporary solution using brass wire pins and have it in mind to replace the wipers with Bachmann style loco pick-ups (the ones with a little wheel that contacts the backs of the loco wheels), but has anyone else got one of these turntables to work and if so, what method did you use to get power to the turntable tracks?
 
How about using a pair of LGB pick-up brushes - you know the "bullets" for the backs of the wheels - I'd have thought they'd be easier to get hold of as spare parts than the Bachmann roller pickups (come to think of it didn't I have a set of rollers off you some time back?)
 
ntpntpntp said:
How about using a pair of LGB pick-up brushes - you know the "bullets" for the backs of the wheels - I'd have thought they'd be easier to get hold of as spare parts than the Bachmann roller pickups (come to think of it didn't I have a set of rollers off you some time back?)
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Yes, I thought of using LGB bullets Nick as I've got quite a few of them from my battery conversions. The problem is that they would foul the wiper pick-ups that are attached to the turntable tracks, whereas with the Bachmann ones, the rollers would run over them quite nicely. It's difficult to explain and I haven't got any photos.

Yes, I did send you a set of rollers, that's where I got the idea of using them from. However, as this turntable has six tracks running off it, we'd need a dozen pick-ups.
 
Due to issues with the Pola brass wipers getting caught in each other and also the fact that electricity is only available to the turntable track when the table is aligned with other tracks in the layout, I have rebuilt the turntable like this:
- Added a base plate with a split copper plate on top of the base (two pieces without conductivity).
- Installed two LGB 63120 Electrical Pick Up brushes underneath the table 180 degrees opposite of each other and with the same distance form the center of the table, both brushes touching the copper plate. Connected the brushes to the rails with wire.
- Connected the two copper halfes to the digital control unit.
- Added a machine screw M5 in the center of the base plate and a ball bearing in the center of the table to center the table to the base plate.
-Removed all the Pola steel balls and spacers and replaced them with aluminium angles with ball bearings at 6 locations around the underside of the table.

Please note that this is intended for digital use and polarity for the locomotive is not an issue. I do get electrical interruption when the brushes pass the split in the copper plate for a second or two, but apart from that the turntable track has electrical connection all time. I could have used a short-circuit electronic unit to automatically switch polarity and avoid interruption in electrical connection.
 
Thanks Loco, that's a very interesting solution. As you mention, you seem to have had the same problem with the brass wipers tangling with each other - a pretty poor design IMO when you think how much the kit costs. My friend's railway is also digital, so your solution will be considered. :thumbup:
 
Here is a link to a rebuilt Pola turntable:

http://www.lgb-ohliger.de/Umbau.html

Scroll about half way down. It is in German only, but with a couple of pictures. The solution in this link is a split ring - one inner and one outer. One brush for each ring.[strike] As far as I understand that will only work if you only have one entrance/exit track and/or tracks with no polarity issue[/strike]. I think he has to switch polarity in one way or the other... The good thing about this solution is that you have electricity in the turntable track all the time.
 
Well I built my own G-Scale turntable, so I'm not sure how relevant this will be, I've not seen the Pola one.

Power for one rail of the bridge track came through the centre shaft, the other through a ring with brushes similar to what is being descscribed here. I did consider using the wheels that ran round the outside of the turntable pit on rail as one of the sources of bridge track power.

While it is true that because DCC is used it doesn't matter to a loco on the bridge track if the polarity reverses. However what does matter is that the polarity of the bridge is the same as the polarity of any exit/entry track when a train tries to exit/enter, otherwise a short circuit will be created. This could be solved with a standard reversing unit, but equally reversing the polarity on every 180° turn of the bridge from a fixed point will have the same effect, I think that the split ring solution being described here achieves this. You can have any number of exits/entries if the polarity reverses every 180°. Because the bridge of my turntable was powered by a stepper motor I knew when the bridge has turned 180° from a fixed point so I just used some relays to reverse the bridge polarity.

Actually polarity is a bad word here because we are talking pseudo AC but you get the meaning.
 
Have one of those Bertrum Heyn kits here works really well.
Item is well built and smooth in operation you can fit as many tracks as required but these are ordered as a seperate item and not included with the main kit.

Motor adaptor works well but i fitted to my own building.

Just need to order the other one for the other end at some point.

Not cheap, but then most things are expensive in this hobby:bigsmile::bigsmile:
 
steve parberry said:
Have one of those here works really well.
Item is well built and smooth in operation you can fit as many tracks as required but these are ordered as a seperate item and not included with the main kit.

Motor adaptor works well but i fitted to my own building.

Just need to order the other one for the other end at some point.

Not cheap, but then most things are expensive in this hobby:bigsmile::bigsmile:
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Sorry Steve, but are you talking about the Bertum Heyn kit? Your description doesn't sound like the Pola version?
 
yb281 said:
steve parberry said:
Have one of those here works really well.
Item is well built and smooth in operation you can fit as many tracks as required but these are ordered as a seperate item and not included with the main kit.

Motor adaptor works well but i fitted to my own building.

Just need to order the other one for the other end at some point.

Not cheap, but then most things are expensive in this hobby:bigsmile::bigsmile:
Click to expand...
Sorry Steve, but are you talking about the Bertum Heyn kit? Your description doesn't sound like the Pola version?
Click to expand...

Yes sorry should of made that clear about whos kit it was, yes its the bertum heyn kit i was refering to. Post edited.
 
We've looked at a couple of ways to carry the current to the bridge for the GME turntable schemes, and will probably use a simple cable winder, often used in rotating machines where the rotation isn't continuous. Provided the turntable rotation is limited to just over one revolution (or thereabouts) this works very well. The principle is simply a helix of wire guided between inner and outer shells, and mechanical stops to make sure you can't strangle it. For outdoor use this is probably the most rugged way to do it. A solution that allows continuous rotation is to use sealed slip ring assemblies, but these can be expensive unless you can source them on the surplus market.

Andrew
 
Well thanks to Mr Loco's excellent ideas and links, we got the turntable working this afternoon (just in time for the rain to arrive). The basic principle is a split brass plate under the deck, each half wired to a different rail on the shed entrance track. Under the deck, a pair of cut-down LGB plunger pick ups rest on either of these two brass plates, each plunger wired to a deck rail. A plastic card inset seperates the two brass plates and ensures that the plungers cannot touch both halves simultaneously.

We have not yet added a central boss or changed the Pola supplied bearings, although this is a possiblity in the future.

All seems to work for now, although I wouldn't in all honesty recommend one of these models for outdoor use. Only time will tell.
 
Hello,

let me share with you the implementation proposed by Mr Ohliger that I made. I actually ordered the required parts to him, through his web page.

First two pictures are the same, but made from opposite places. I will describe this first picture while the second picture is the same.
You may see the three main components of the turntable:
- first you see (bottom part of the picture) the base I made of 3mm aluminum plate, cut to fit the external perimeter of the turntable, including the control house. You can see the small centered copper plate, over which the rail contacts receive current to the turntable rails. Also you see water drainage holes around.
- in the middle of the picture you see the round grey ring with holes around to drainage water, that coincide with those in the base plate.
- in the upper part you can see the center part of the turntable, upside down, with the ball bearrings in place.
- the fourth piece, the electronics with its housing can be seen in other pictures below.
4ac10f6dc37840ca809b57c5e8f25d5c.jpg

21c51970521a48ab902ba1587b0f44c9.jpg



The next picture you can see all pieces assembled and in testing mode. All seemed to work fine. By the way, I added two kitchen handles to the top turntable for easy removal in case of problem. I still have to give a patina to disguise it a bit.

a9800f12c1d243d49647991a23ce14b1.jpg


Finally you can see the turntable in its definitive place with the in/out rails already connected (on the right) and the parking rails being just positioned but not yet operational.

d57362c7e82b4287ad12152df3e88fac.jpg


I hope you may like this. After being in place there has been quite some rain fall in Madrid and I am trying to improve water drainage. I have seen that water goes inside the aluminum plate through the center rails, I will have to use some silicon to better get water from coming in.

Best regards to all, and compliments to Mr Ohliger.
Jose

PS: don't know why the pictures do not show in full . . . . , some help please ?

Edit - Pictures inserted in full by Moderator following the instructions here: http://www.gscalecentral.net/tm?m=51661&high=how+to+insert+picture < Link To http://www.forum.gscalece...=how+to+insert+picture
 
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