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Discussion Boards => General Discussion => Topic started by: kpsdjs on August 21, 2011, 10:11:21 PM

Title: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 21, 2011, 10:11:21 PM
Hello all,
     I have recently aquired the Bachmann motorized turntable, and find that it "shorts out" as the rail rotates to it's own neighboring rail. While rotation continues faultlessly, it has none the less "shorted" long enough to reset my "E-Z Comand Controller" every time.
     I have a "relay patch" to cut power to the table's rails. However, I wonder if there is standard fix, or plane to engineer out the problem?
     The best fix would be to only allow the "contact fingers" power contact near "index". I quess this got overlooked at some level, but deserves attention, as it is otherwise an extreemly well made product.
Any Thoughts? kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Doneldon on August 21, 2011, 10:31:08 PM
kp-

I'd also inspect both ends of the rails on the bridge and the various access, roundhouse and garden tracks to make sure you aren't getting a momentary contact/short there. If you find such a problem it will be a minor issue of filing the offending rails. I don't know how likely it is that this would be your problem but it's so easy to check and repair if necessary that I'd do it before looking deeper.
                                                                                                                                                     -- D
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 21, 2011, 10:53:45 PM
Doneldon

     Thanks. But thats not it.

     This does remind me that the instruction never mention anything about "Polarity" at different positions. I had to run through all the positions one at a time and note "polarity". Otherwise bringing in more than one rail with power can cause catastrophic "Short Circuit" to entire layout!!

Thanks,
kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 21, 2011, 11:00:57 PM
Doneldon, P.S.

     Just FYI. The problem is known exactly. It is an engineering error. The rail should not be allowered power while it rotates away from "Indexed" area!

Have a nice day, Doneldon

kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jim Banner on August 22, 2011, 01:15:27 AM
kpsdjs,

Don't keep us in suspense!  What exactly is the exactly known problem?  If not the rail ends, then what is shorting to what and where and when exactly is it happening?  If it is an engineering error, I am surprised that we have not heard from everybody who has bought one of these turntables.  If the problem occurs only occasionally, perhaps it is more of an assembly error.  If it occurs as the locomotive rolls off the bridge onto one or more approach tracks but not all of them, it is an installation error - the turntable may be forming part of a reversing track and requires a polarity reversing switch (dc) or a phase reversing autoreverse module (DCC.)  Alternately, the approach tracks may be wired at random with no regard to polarity or phase.

The idea of removing power from the bridge rails is not out of the question.  It could easily be done with a pcb switch.  But unpowered bridge rails would mean that the locomotive's headlight would be on/off/on/off/on/off... as the bridge turned.  One of the nicer scenes, both in the model world and in the real world, is watching a steam locomotive, all fired up and lit up, being turned.  This scene is particularly poignant just before sunup or soon after sunset.  Most of us go to great lengths to make sure our turntable bridges have a constant source of power as they turn.

Because I enjoy this scene so much, I am glad that this "engineering error" was included in every turntable I have ever seen or built.

Jim  
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 22, 2011, 04:04:13 AM
Jim,
     Thanks for your reply. The problem is better understood if describe contact area's better.
First; When track is "indexed" It makes contact between the Bridge and Rails with Flexable copper contacts that are atached to the underside of the bridge rails. As rotation starts, these contacts move with the bridge and extend out to contact the next rail. Unfortunately, that next rail is it's own "other rail polarity"... and ZAAP! a momentary short causes reset of my E-Z Comand.
     The engineering fix would be to not allow power at that moment. I understand wanting all the lights and whistles, but they do alter polarity on some rails already, (as compared to main track power @ # 4pos.), causing momentary outages. Perhaps those contacts should "Drop away" slightly so they will "clear" unwanted rails while away from "index"? or?  I will re-engineer for $$. But I think they should do something to improve the product.

kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jerrys HO on August 22, 2011, 06:38:06 AM
kpsgjs
I have the same turntable and have no problems. The pit rail is powered and was designed that way. As the table turns it cuts power from one track and powers the next as it turns. The 4th track position is set up for the main track input from your controller.
Jerry
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 22, 2011, 06:59:22 AM
Jerrys HO,

     Do you have an E-Z Comand DCC Controller? Or do you only run DC. Problem would not show up on DC systems. It keeps resetting my DCC system.

Thanks Jerry,
Please re-reply. I am very curious to hear about anyones experience with this turntable.

Thanx,
kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jerrys HO on August 22, 2011, 07:27:42 AM
kpsdjs,
      Yes I am running the ez command controller for now. I did not put the decoder in as I have the turntable hooked to separate power pack. With the separate power pack I can slow the turntable down to scale speed. I am using the 44212 power pack and controller. I plan on installing decoder when I replace my ez command to the zephyr.
Jerry
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: vidguy069 on August 22, 2011, 09:00:24 AM
I recently acquired the afore mentioned turntable (happy b-day to me).  But my problem is a bit different.  I have the TT running DC on a separate power supply, and the rest of the layout is DCC with a MRC controller.  When everything is connected, and powered, the TT runs quite nicely.  The bad news is there is no power to the track.  I separated the terminal rerailer from the #4 index on the turntable, and the track had power.  I have no other 'powered' rails going to the turntable.  I have a couple of pieces of track on the 'other side' of the turntable so the locos have a place to sit, but that's it. 

My experience so far.

Vidguy069
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: jward on August 22, 2011, 09:47:26 AM
i will probably get into trouble for saying this, and i hope this is taken as the constructive criticism it is intended to be. bachmann needs to do a better job of providing documentation for their products. in the case of the turntable, atlas provides information on the polarity of each of the radial tracks. why doesn't bachmann? failure to provide this info sets up a situation where short circuits could damage the layout's electronic equipment. seeing as the polarity of the radial tracks is common to both the manula and motorized turntables, and the manual turntable is marketed to children in the thomas line (tidmouth sheds) you'd think explicit instructions would be provided.......
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Bucksco on August 22, 2011, 01:28:59 PM
There is a possibility that the DC mode is not being "disabled". This would depend on the decoder being installed. When an NMRA 8 pin decoder is mounted into the socket it pushes down a small square button that switches the Turntable to "DCC" mode. If you are not mounting an 8 pin decoder into the socket the button will not be depressed which could be the problem.
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: vidguy069 on August 22, 2011, 03:23:12 PM
This probably won't work for every one, but here is my solution.  Tested, once.
I put a piece of track (4.5 in) between the terminal rerailer and the turntable.  Locos and turnouts are DCC turntable is DC. Don't know or at this point care, but it seems to be working. Of course the loco did run off the end of the track because dumb-dumb here did not check the position of the switch, but that's a detail we won't didcuss.   :-X

Vidguy069
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jerrys HO on August 22, 2011, 05:54:50 PM
vid,
   I did the same thing on my first attempt and it did the same thing. I removed the power rerailer and it is fine. I believe it has something to do with powering the tt with a dc controller but I could be wrong.(nah). I can't wait to post pics of my heljan roundhouse that I am converting to fit. I am just waiting on wall and roof matching panels from plastruct.
Jerry
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: vidguy069 on August 22, 2011, 06:21:44 PM
Jerry;I actually got one loco on the the 'wait' track, then the turntable 'died'.  Frustrated, you bet.  But I will NOT give up.  Worst case scenario, I'll by the bloody decoder and have my LHS install it.  Everything else is DCC, why not this.

Good luck with the roundhouse.


Vidguy069
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 22, 2011, 08:38:32 PM
Yardmaster, and All,

     My TT is DC, being controlled by my DC controller. The track @#4 has DCC on it. But the DC controller does not seem to mater, even if I unhook it, the DCC is still shorted!
     I can't get past the FACT thet when rotation starts, it Immediately shorts to it's own "other rail polarity". (which is DCC) Shuts down my DCC controller every time. This will be in ALL of these TTs!

Hope to hear more,
kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: NarrowMinded on August 22, 2011, 09:23:30 PM
I read through this and not having a Turn table or the diagram one thing jumps out at me and that is that you are using DC to power the table and DCC to run the rest of the layout. 

I'm curious if the drive is isolated from the track? i've read somewhere about powering track #4 is that how the turn table gets it's power? I'm just throwing questions for thought out there.
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 22, 2011, 09:53:41 PM
NarrowMinded, and All

     Please re-read my last post. I think it answers you. Track #4 provides only power to the bridge. (At least in DC mode) The instructions show DC mode needs "seperate" power, but the DCC seems to show only "track" power is required.

I.e.; My TT is DC, being controlled by my DC controller. The track @#4 has DCC on it. But the DC controller does not seem to matter, even if I unhook it, the DCC is still shorted!
     I can't get past the FACT that when rotation starts, it Immediately shorts to it's own "other rail polarity". (which is DCC) Shuts down my DCC controller every time. This will be in ALL of these TTs!

Hope to hear more,
kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: the Bach-man on August 22, 2011, 10:41:37 PM
Dear KP,
In DCC mode, there is no power feed to the turntable other than the track. Address the turntable and control it like a locomotive, using your DCC command station. Do nor use the turntable controller...
Have fun!
the Bach-man
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 22, 2011, 11:22:46 PM
Bach Man, and All,

     Even if I provided DCC module, the rail will still "short" as I rotate away from Index @#4!! Please... Do you have a real solution? Or just glaze?

THE #4 TRACK WILL ALWAYS (All-Ways) SHORT WHILE ROTATING AWAY FROM IT!!

Gimme something I can use.

Are there others out there with this table? I need to hear from as many as possible!

Thanx
kpsdjs
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jim Banner on August 23, 2011, 12:11:00 AM
kpsdjs

I think I understand what you all telling us.  But for that to cause a short circuit, the bridge would have to powered from somewhere other than just the contacts under the rails.  In that case, what are the contacts under the rails for??  Most (all?) turntables I have dealt with power the bridge in one of two ways and power all the approach tracks separately. 

The B-mann turn table is apparently different.  But it sounds like the bridge track is still powered up all the time.  It is were not, then the contact tab touching the wrong rail could not cause a short - it would just be touching an unconnected piece of metal.  You could check this very easily by connecting a 12 volt lamp (such as a grain of wheat bulb) across the bridge rails and see if it stays lit as the turn table turns. 

If I understand correctly about the B-mann turn table, the only power to the whole shebang is via track #4 and somehow that power gets to the bridge other than through the contact tabs.  Then when you turn the bridge, it powers up whichever other approach track it aligns with via those contacts.  What would happen if you slipped a piece of Scotch tape, sticky side up, under the ends of the rails of track #4?  Then the contacts would not be able to make contact with track #4 and there would be no short circuit. 

I suppose it is also possible that the bridge rails are supposed to be powered up by track #4 only when they are aligned with it but not otherwise.  In that case, you would have to look for some sort of "sneak path" carrying current to the bridge rails even when they are supposed to be dead.  This sneak path could be power applied to another set of rails or possibly by using the same power pack to power the trains and to turn the turntable.

Unfortunately, our local hobby shop does not have one of these turn tables in stock or I would ask to borrow it to solve this problem.  So I leave to it you to try the light bulb test and hope you will continue to let us know what you find.

Jim 

 
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 23, 2011, 12:44:36 AM
Jim,

Way YES!! You hit it with this paraghaph;

If I understand correctly about the B-mann turn table, the only power to the whole shebang is via track #4 and somehow that power gets to the bridge other than through the contact tabs.  Then when you turn the bridge, it powers up whichever other approach track it aligns with via those contacts.  What would happen if you slipped a piece of Scotch tape, sticky side up, under the ends of the rails of track #4?  Then the contacts would not be able to make contact with track #4 and there would be no short circuit.

     That is absolutely the answer. Pos#4 does not NEED to contact the bridge, so the tape idea works perfectly. Another index # also has a DCC powered track coming in, so tape there also..WOOP.

     There is still a problem that does not bother me, but you had mentioned earlier. The power to the bridge is not constant...Blinking out as the bridge approches idexes that are polarized differently. So engine lights, etc. blink on/off/on as it rotates around.

Thank You Very Much Jim,
kpsdjs
Kelly
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jerrys HO on August 23, 2011, 05:37:10 AM
Kelly,
      There is still a problem that does not bother me, but you had mentioned earlier. The power to the bridge is not constant...Blinking out as the bridge approches idexes that are polarized differently. So engine lights, etc. blink on/off/on as it rotates around.
      I went and ran my MTH engine on my tt just to see,because it has all the bells and whistles you could ask for. Now as it sits in the pit and turns it does not lose power.all the lights and even crew talk stays going. The only time it shuts down is when I pull off to a separate index and turn the tt away from it.

Kelly and Jim and others
     Looking at the diagram that came with it which is not much info at all, shows #4 tracking has power feeding the tt thru a wire to the center rails which in turn should keep it powered. As the tt moves the brush like contacts connect with each approach rail and powers that rail. Your engine should not blink on and off. I also checked it with my bachmann engines as well.
     If you bought this new I would send it in to the service dept. and have it checked or replaced.
     When you say you lose power to the track does your ez controller blink and beep as it does when the rails are shorted or are you just losing power like if you unplugged your power pack from the wall.
    Jerry
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: Jerrys HO on August 23, 2011, 05:43:07 AM
Kelly,
    I have a "relay patch" to cut power to the table's rails. However, I wonder if there is standard fix, or plane to engineer out the problem?
    I don't understand the need for this relay patch if you care to explain? Matbe this is your problem?
Jerry
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on August 23, 2011, 06:45:15 PM
To All,

     Problem is fixxed. Thank you very much to Jim Banner. His idea to isolate "Powered" track inputs with tape solves ALL. I don't need relay patch. Never installed it. I just knew that I could cut power to the bridge while rotating!
     The TT is not defective in any way. Just some fine tune at next run. The Lights DO blink on/off/on BECAUSE they engineered it that way, so that shorts occur less!
     My promlem was that I had more than 1 powered track comming into the TT. All these powered tracks need isolation from contacting the bridge. (Even if polarized correctly)
     I will, of course, not use tape. I will remove offending rail contacts and file away the Bottom 1/8" or so of those 2" lead-ins. If I ever want to change layout, I will just replace the 2" rails with new! Better yet, just insert isolating rail joiners. EXCEPT at #4 index, as it NEEDS to get bridge voltage from there.

Thank You Again Jim, a real Banner guy!
kpsdjs
Kelly
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: richd286 on October 24, 2011, 10:46:52 AM
I have had the same issue after recently bring power up after a track change.  After reading everyones responses I think I have an answer...  I have a DCC powered arrangement with power coming into the TT from position 4.  I get a short when the turn table crosses polarity with another powered spur.  I have power coming out of the TT conflicting with a powered section.  If I remove the power to the spur, it will only be powered when the TT is aligned with it which can be OK if I want that spur dead when the TT is moved away from that position.  The other fix might be to put insulators between the spur and keep it powered.  My concern this the insulated track section is a possible short when an engine crosses the insulators and bridges the circuits.  I will test this tonight and get back to you.
Title: Re: 46299 Motorized Turntable shorting during rotation.
Post by: kpsdjs on October 24, 2011, 02:54:22 PM
Rich,
     Putting isolators on the powered rails will fix UNLESS that piece of track is polarized wrong. Some TT positions are polarized one way, and others, opposite. I tested each track to find polarities.
     Going clockwise from pos. 1, rail 1 is "A", rail 2 on pos. 1 is "B" polarized. Pos. 2 is A-B, 3 is A-B, 4 is A-B. I.e.; 1-4 are alike. pos. 5-13 are B-A polarized, and 14-16 are A-B polarized.
     I.e; Pos. 1-4, and 14-16 are alike, but pos. 5-13 are opposite polarity!!
     You MUST isolate powered rails (except #4) to prevent shorts durring rotation!
Hope this helps. Maybe Bachmann will add this data next run?
Kelly