DCC converted Hornby Turntable not aligning with second exit

[Ullswater]

Hi all - I have completed the DCC conversion of my Hornby turntable as per the instructions on the Hornby website, and have it operating via Railmaster.

 

I am going down the route of putting power to each of the exit rails. So far I have put power

 

to two of the exit rails, plus of course the entrance rail.

 

All seems to work fine, except that the turntable misaligns on the second exit rail, by a whole track width.

 

So it is perfectly aligned on the entrance rail. When turned clockwise, it

 

then aligns perfectly on the first exit rail. When turned clockwise again, it appears to align perfectly with the second exit rail, but then after a pause, moves clockwise by a track width. When turned clockwise again, it aligns perfectly with the third exit

 

rail.

 

So the second exit is currently unusable. I wondered if anyone had any ideas on why it might do this?

 

Any help greatly appreciated.

[idlemarvel]

I did the same DCC conversion and the turntable worked fine on all exits. In the process I accidentally dismantled the turntable, so the way it works mechanically is that the motor drives a large cog wheel with teeth missing on one semicircle, so that

 

the turntable rotates while the cog teeth engage, and then pauses where the teeth are missing, even though the motor is still running. Very simple. So the way the DCC control works from RM or from Elite is to drive the motor for a certain time period to move

 

the turntable clockwise or anticlockwise between turnouts. The time period can be adjusted in railmaster.ini. I found the default value worked fine, but after a few hours use it can get misaligned as per the instructions.

 

So having said all this, from

 

your description it sounds like the mechanical part is working, otherwise you would get misalignment at every turnout, unless the teeth are damaged on the moving turntable ring on that exit. So it would appear there is something wrong with the timing of the

 

motor, i.e. the control commands sent through RM. I noticed that on initialisation (at startup of RM) it tries to align the turntable to some initial position supposedly determined by your track plan, but I never found that to work quite the way I expected

 

so I had to manually set the turntable at the correct starting position. Does your problem only occur at startup? Have you tried driving the turntable "manually" from your Elite controller (if you have one, you may not)? Does it work correctly that way?

[HornbyRailMasterSupport]

When setting up the Hornby turntable with a loco decoder using RailMaster there are several factors including the motor, type of loco decoder used and other minor things which can affect the accurate position of the turntable track with the entry/exit

 

roads.

 

Within the RailMaster.ini file (in the RailMaster program folder) you can set both the speed of the turntable and time (to the nearest tenth of a second) taken to drive the turntable from one road to another.

 

The Speed setting is normally

 

fine and realistic. It also substantially quietens the turntable motor, so all you need to concern yourself with is the timer setting.

 

If the road overshoots then you need to reduce the time. If it undershoots then you need to increase it.

 

One

 

tip is this: There is a dwell time of a good four to five seconds on the Hornby turntable, where when the turntable track reaches an entry/exit road it will sit there until moving off again. You should manually run the turntable and when it reaches a road

 

count two or three seconds to yourself and then stop it immediately (this will be halwaf through the dwell time). This way, you are giving the turntable a good two seconds buffer zone either side, so when you move it clockwsie or anticlockwise using RailMaster,

 

any minor errors in timing or motor are absorbed by the buffer zones and you will find it works very well indeed.

 

You need to use a little trial-and-error to get the best timing for running the motor within the RailMaster.ini file.

 

If using the

 

Hornby Elite just run the turntable at roughly the same speed as RailMaster wuld until you position the track with an entry/exit road and stop it approximately halfway into the dwell time. If using the eLink you can set up a temporary loco with the same DCC

 

Id as the turntable and run it as you would if you were using the Elite.

 

[Ullswater]

Thank you very much indeed Idlemarvel and Railmastersupport for your replies.

 

I have been experimenting for a couple of hours and have just come back from the experimenting to see your reply, Railmastersupport, which aligns completely with my findings.

 

Essentially

 

I have found that on my particular turntable, the time between exit rails is about 18.6 seconds - quite a lot less than the 23 in the railmaster.ini file.

 

I timed this by setting the time in the .ini file to be 300 seconds, which meant the turntable

 

would rotate through multiple exit roads from one press in railmaster, and I knew for certain it would be rotating at the right speed (still 40). I used a stopwatch then to time between the motor starting, stopping, and starting again, and arrived at the conclusion

 

about the dwell time - so as you say, I have positioned it manually in the middle of the dwell time.

 

I think by reducing the time in the ini file to 18.6 it will be much more accurate - time will tell.

 

One question - the turntable rotates the

 

opposite way to the way Railmaster says it should be. I have wired up exactly as instructions on Hornby website say - should I swap the wires on the motor (black and red wires) to correct this?

 

Thanks once again both

[Fishmanoz]

Yes, swapping the wires to the motor will reverse the direction.

[Blackbird]

Can I make a general comment on this problem of using the Hornby R070 turntable with DCC and Railmaster (computer control)

The R070 turntable and previous versions were designed for direct DC control with a mechanical design using a Geneva gear to provide

 

alignment to track outlets. The Geneva gearing gave a definite mechanical pause in the rotation, when aligned, allowing the dc control to be switched off. The alignment system was purely mechanical. The use of Railmaster or other computer control is based

 

on timing. From a computer based control, the timing can only be correct if the input parameters are consistent i.e. motor loading being consistent for the rotation of the turntable. If, as the original inquirer mentioned , the problem only occurs at one defined

 

position (second exit rail), this implies a mechanical problem; a restriction/overloading in the gearing at, or near that position?