Perhaps a solenoid to inject a pin into the mechanism that locks it.
John
That’s what I needed John, thanks for pointing that out! And howdy Randy, thanks for the instructions, I’ll do just that. Funny that my MLS-stored pics work here… I probably shouldn’t make a habit of that…
I’m in total agreement Greg, and thanks for your thoughts. (And I credit you for turning me on to Tam Valley, I’d not looked at their site in years). The servo-protection spring should be near the servo, I think. A dirt-simple approach might be to put a V-kink in the cable, keeping it oriented with 2 new posts coming from the mount. For switch cutting, a real spring at the throw bar connection would be nice. Will need to experiment.
Yes, I’m suspicious of the micro servo… you’re probably right, might as well go hole hog. Tam Valley recommended the HS 311, which can be had for about $10.
Rick, that’s a really nice and compact unit, did you design that board yourself? I’ll have to read more about it, it looks very impressive. Is it compatible with other DCC systems?
Speaking of boards, the “Singlet II” board I’m designing around is a DCC decoder and servo operator. The instructions say it can run on DCC, DC or AC. A cool feature it has is the ability to “learn” where the servo should stop. You put it in learning mode, go back a forth, and it remembers the positions where the force gets high. Something like that. It has an optional relay for indication / frog powering / etc. And it has inputs for local operation, on-board LED indication & buttons. Especially in view of the fact that it’s also a DCC decoder, that’s a lot of bang for $16.
Here’s the web page,
http://www.tamvalleydepot.com/legacyproducts/singletiiservodecoder.html
===>Cliffy
Sorry Cliff, but those pictures link to this
at least that’s what happens on my 'puter. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-undecided.gif)
Bob McCown said:
Hey Cliff
A lockable switch means that, when locked, a switch CANNOT be thrown by someone at the switch; it can only be operated electrically. The lever either does nothing, or cannot be moved at all. A local manually-operated-selectable switch would work. Ive been envisioning various kinds of solenoids that connect/disconnect the switch stand with the mechanism, but havent quite got it figured out.
Hi Bob, thanks for clarifying. And have I told you your site is awesome? Well, your site is awesome.
For local operation, I’ve been working on two different electrical switching devices, but you’re describing a means of enabling / disabling them, as I think John points out. This is very much related to a similar issue I’d like to solve, the overall enabling / disabling of indication lights. If we’re solving for only a DCC solution, we could add an additional decoder & relay in each turnout controller. But, that’s expensive. And, it isn’t portable to non-DCC layouts.
So, I’ll suggest something, but it’s not elegant and hasn’t been designed by any means. Say you have one or more sealed boxes, each having a relay and some means of remotely commanding it. That relay serves 1-20 (I’m guessing) turnouts, for either indication, local button enablement, etc. You’d have a local bus running from this box to your turnout control boxes or switch machines in the vicinity.
If DCC, the control & power means is another Singlet decoder, a relay, and a power conditioner (DCC to whatever the bus requires).
If rail power, I’d like to have a discussion on a “rail wart” rechargable battery thing. But for RC & Live Steam, we’d need to talk about an overall accessory power bus; and if one installs that, one might as well add the extra wire in the sprinkler-cable bundle for enablement of local switches or indicators.
Your thoughts?
Best,
Cliff
Perhaps some variation on a ‘servo saver’ ?
http://www.fingertechrobotics.com/proddetail.php?prod=servo-saver
Hans, I wouldn’t have known they weren’t coming up. So thanks!
Following Craig’s and Randy’s advice, I just uploaded the pics to the freight shed, so here goes:
Do you see these?
CJ
Thats prett nice, Cliff. Neat idea.
@martin. Thats an interesting thought. I wonder if there is a small enough (and cheap enough) electrically operated clutch that we could put between the servo and the lever. I dont see anything on SDP…
Cliff Jennings said:
Do you see these?
CJ
Yes Sir! Thanks!
Thanks Martin, I’ve seen other “servo saver” products, but none as elegant as that.
The main thing, I think, is to intoduce a spring to protect the servo, which that product would certainly do.
I’ll try to post a pic of what might be a cheaper approach.
[edit]
Here’s the cable-kink, acting as a spring on the servo end. This would be the “poor man’s” option, saving on any extra hardware. Yes, it would be subject to the user’s adeptness with needle-nose pliers. However, it avoids mechanical joints between cable and spring.
Speaking of which, it would be my (admittedly unfounded by experience) hope that one would buy a small spool of tubing and another of cable, and adjust and replace as and if necessary. Kinda like you would buy a spool of pneumatic tubing, and cut it to length. And replace sections after you hit them with a hoe.
I should point out that this is a Dubro EZ connector, from cable to servo disk. About $5.
===>Cliffy
Yeah, some sort of mod to the servo saver to make a ‘clutch’ type thing. Tighten the clutch and the servo is in control, loosen it and manual is in control? Dunno. Have no idea how that would work, my mechanical engineering abilities are somewhat suspect…
Martin Sant said:
Yeah, some sort of mod to the servo saver to make a ‘clutch’ type thing. Tighten the clutch and the servo is in control, loosen it and manual is in control? Dunno. Have no idea how that would work, my mechanical engineering abilities are somewhat suspect…
El magnet disc clutch, but the question would be how much torque is required, that is how much extra room is there for all the refinements?
I think we’re in basic agreement, that one has to protect the servo, even when the points are at a full lockup. Like, a twig or rock jammed in. Or, mud entering the tube/cable, and hardening.
So thanks for continuing to share your concerns and ideas Martin and Hans. They reinforce what Greg voiced; and the need makes sense to me now more than ever.
Cliff
Power realy circuit. Measures the power required to run the servo under normal conditions. Allow a safety factor and a setpoint. Exceed the set point and power to the servo is cut. For manual a simple clevis and pin.
Good point Bob. It might not need an extra relay though. I’ll ask Duncan (the designer of the Tam Valley board, I believe) whether that is already baked in to the Singlet. I don’t think so; but if it can measure force from side to side in its learning mode, perhaps its firmware can be modified to be a sort of electronic clutch during normal operation, in case of mechanical lockup.
A small update. Tam Valley said an electronic clutch wasn’t part of their driver board, even though they use current measurement to determine ends of travel. Bob, is there an example circuit you could point me to?
Here’s a progress shot of my current model, showing the “heavy duty” servo packed in. I also tried to jam in an optional relay board, designed by Tam Valley to plug into the Singlet board.
The extra 1/4" ID cable glands are for power in, and signal/power out to a frog or indicators. They could be combined. When the (3d printed) mounting settles down, I’ll post a cost estimate.
Cliff,
A mechanical connection note;
Use a hex head screw on the Dubro connector.
Will be easier to tighten with a wrench from above vs. a driver from the side in your neat box.
John
Great catch John, and thanks very much!
Almost done with the packaging, and about to get a trial run of the printed parts.
The big thing lacking still is a throwbar spring, so that’s next to investigate. Greg raised a good point earlier, that the train should be able to cut the switch points. I’ve been designing around switch machines that don’t permit that; and it was a bummer to learn initially that they wouldn’t. But it would be wonderful to have that ability.
I’ll be looking around for tightly-packaged examples of springs between the throwbar and air actuators or ground throws. And if someone has a favorite approach for that, I’d be grateful to see it.
Best,
===>Cliffy
Hi
Try checking your local hobby store or Tower hobbies online for a “SERVO SAVER”.
This little gem is commonly used on larger RC cars steering links to prevent collision damage to the
steering servo in case of an accidental front impact with the wheels.
Buy one then make the rest yourself after you see how they work.
it is a spring loaded link that is perfect for what you are trying to do.
Bill
Bill, read back 14 posts, Martin suggests and it is discussed or the function referred to every post since.
I make it a habit to read threads from the beginning before commenting (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)
Greg