Tortoise Switches

Has anyone got any experience of the reliability of the switches
provided on Tortoise point motors? I've just made up a set of
turnout operating units to go with my Tortoise motors and I was
thinking of using the internal switches instead of fitting
micro-switches to the TOU's tiebar. The switches would be used for
polarity switching, or could be used to operate relays if more
contacts are required.
Jim.
Reply to
Jim Guthrie
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I have heard of problems from some people but I have been using mine for polarity switching for 5 years now with DCC without any switching problems. Same goes for the club layout. The switch is comprised of wipers on a pcb track so its advisable to avoid switching under load. (Frog switching is normally with no load, if you trail the point causing a short the DCC system will cut off the current so when you swing the point to correct it the load is off. If you use car bulbs in the frog feeds to stop the DCC unit cutting out then you will be switching under heavy load and the contacts are likely to suffer).
I have had a couple of failures of the intermediate gear shaft bearings, repaired by adding new bearings from brass tube. The mechanical design of the bearings is poor, not enough lengthwise engagement between shaft and bearing so excess torque forced the shaft ends out of the bearings. The damage was all in the bearing, hence the brass bush.
Keith
Reply to
Keith
Keith,
I had faint memories of reading or hearing some reports of problems, hence my question. I had used TOU operated micro-switches on my last installation, but thought that I might just try and use the machine's internal contacts to make the TOU setup a bit easier to construct.
The main use will be frog switching although I might use one of the contacts for detection, or to drive a relay to provide more contacts. I doubt the load will ever be all that heavy since I prefer to use coreless motors. Or I might just do what Dave Skipsey suggests and use the two switches in parallel to provide a bit of belt and braces.
I haven't had any mechanical problems with any of mine yet, so I have had no need to take one to bits. However, I'll be driving 7mm scale pointwork with non-hinged blades, so your advice might just be welcome some time in the future :-)
Jim.
Reply to
Jim Guthrie
Dave,
I was half thinking of doing that. But I have a complex formation to wire and I thought I might need the second switch to use for other than polarity switching. If that is the case, I might just stick a relay on the contacts to get more contacts of known reliability.
Jim.
Reply to
Jim Guthrie
Hi Jim,
A lot depends on how you power the Tortoise motors.
If you leave them under power in the stalled condition all the time, the internal contacts work ok-ish (you can't really rely on a wiper on a copper track to be reliable for years, especially if they ever find themselves making or breaking a short-circuit current).
If you power the motor across and then switch off, the motors work fine mechanically and there is a big saving in power consumption if you have dozens of these motors. But in the unpowered drive condition the internal contacts are not at all reliable. The back-pressure from the stretcher-bar, unbalanced by the forward drive from the motor, twists the internal drive arm slightly, lifting the wipers from the copper tracks.
Martin.
Reply to
Martin Wynne
If you can put up with three wrires from the panel (after all you probably had three when you used solenoid point motors), you can use a 3 (or 4) way double pole, double throw switch. Two of the poles are crossover-wired and power the tortoise, the third switches power at the frog, with input from the same feed that goes to the track.
Reply to
Christopher A. Lee
Martin,
My previous small 7mm layout was the first one on which I used Tortoise motors and I worked them in the 'constantly on' mode. It took a lot of getting used to - with all these stalled motors on the layout :-) I could operate them on the new layout in the same way since that will be the easiest way from the electrical point of view, but I don't think I will ever get used to stalling motors intentionally, and to a layout which quietly buzzes :-)
Also, when making and setting up the Tortoises with their TOUs, I noticed that there could be a bit of bounce back when I took the power off at the end of a stroke. I work Tortoises with stiff arms (50 thou spring steel) and adjust the throw with the fulcrum so that there is just enough loading at the end of the stroke to give a good seating for the switch blade. If there was a bit of bounce back with the power switched off, then I could be splitting blades in Scale7.
Jim.
Reply to
Jim Guthrie
I have also had them ease back when left with power off, for reliable operation they need to be used as 'stall motors' as designed. My problem with the bearings I believe to be a result of having a bit to much voltage on lightly loaded motors so they were hitting the end stop rather hard. I now adjust the resistance in series so they reach the end of travel fairly gently.
If you want motors that de-energise at the end of travel you need a mechanical lock, ie a Z slot Midland style or a butterfly crank, ot an overcentre spring like Peco. But if you make up that sort of linkage there is no need to waste money on a Tortoise, cheap Model aircraft servos will do the job. Keith
Reply to
Keith

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