Author Topic: Stiffness of Fast Track crossover points / servo mechanism redesign  (Read 8659 times)

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bbussey

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Re: Stiffness of Fast Track crossover points / servo mechanism redesign
« Reply #60 on: September 19, 2013, 09:52:53 AM »
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I also like the idea of thicker throw bars, but I may go the route of adding brass reinforcement underneath so as to not worry about insulation issues of the points.  Finalizing the mechanism is the top priority though. 

I created a very simplified redesign that addresses everyone's concerns in this thread, and takes advantage of the low servo cost by assigning one servo per each set of points.  It works exactly like a Tortoise, but has a 1.6" x .75" footprint and protrudes no more than 2" below the underside of the table top.  Since one Tam Valley controller can operate two servos, I still maintain my original functionality.  While it's not prototypical to throw all four points regardless of the desired route, it is a more practical option for my scenario.  I'll post photos when I have a working sample.

Bryan Busséy
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www.bbussey.net
Bridgeport & New London in N scale


nkalanaga

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Re: Stiffness of Fast Track crossover points / servo mechanism redesign
« Reply #61 on: September 20, 2013, 01:49:56 AM »
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Insulating the points would be fairly easy with a brass tube throwbar and epoxy.  Just make sure you have nonconductive epoxy, which I believe most is.  Solder the two points to individual pieces of tubing, making sure that the pieces don't extend far enough to meet in the center when the points are properly spaced.  If desired you could thread the tubing pieces on a rod to keep them and the points properly aligned, but DON'T solder the rod in place.  As the points would be electrically connected to the stock rails, the extension to the outside doesn't matter. 

Coat a piece of brass rod smaller than the hole in the tubing with a thin layer of epoxy, and let it set, to make sure the rod is insulated.  The ends of the rod don't matter. so you can coat a long piece then cut it to length.  Once it has set, put some epoxy in the inner end of each piece of tubing and push the rod in.  Putting the epoxy in the hole will also make sure the end of the rod is insulated.  Make sure the points are spaced right and let the whole thing set.  Almost indestructable, and it's insulated.  If your epoxy is heat resistant the points can be resoldered if the ever come loose without damaging the insulation.

I haven't actually tried this, but read about it somewhere, and have used the basic idea on one turnout.  In that case I soldered the rod in place as a test to see if it made properly gauging the points easier.  It wasn't any harder, but not enough easier to be worth the extra work.  Making a gauge to space the points would probably be easy enough.  All you'd need is a piece of wood, with slots filed to hold the outside (filed) faces of the two points at the right distance.
N Kalanaga
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nkalanaga

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Re: Stiffness of Fast Track crossover points / servo mechanism redesign
« Reply #62 on: September 21, 2013, 02:46:12 AM »
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Gary:  There's no real point in a closeup of the throwbar, as it looks exactly like a PC bar once it's installed, the difference being the thickness.  Painted, one can't tell the difference, and the shim brass brace can also be used on a PC bar.  I used the brass mostly because I was tired of the foil coming off the PC throwbars on my old layout.  After a few years the glue seems to get tired.  With brass that isn't a problem.  On the other hand, insulating a PC throwbar is easier, as one can simply cut the foil. 

I have some pictures I can post, maybe this weekend, most of which have been posted before.  Thank you for the compliments.

For anyone interested in dual gauge track, the turnouts are a pain, but the plain track is easy.  I used ME flex, like the rest of my layout, and removed a tie every inch or so.  That tie was replaced with a PC tie, and the third rail soldered to it.  It was actually easier to lay the flex before soldering the new rail.  Remove the plastic ties, lay the track, test it to make sure the standard gauge runs smoothly, insert the PC ties, wedge a thin piece of wood under each end to keep it tight against the rails, and solder all three rails to the new tie.  I used a homemade wood track gauge for the third rail, sliding it along as I soldered.  Being wood, it stayed cool, and I could hold the new rail down while soldering.
N Kalanaga
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bbussey

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Re: Stiffness of Fast Track crossover points / servo mechanism redesign
« Reply #63 on: September 27, 2013, 07:06:57 PM »
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I reworked the design so that the ratio of servos to points is 1:1.



I received two of the redesigned servo bases from Shapeways today and hope to have them installed before the end of the weekend.  I still have to pick up the square K&S tubing and brass K&S sleeves, as well as the eyelets.  Also tested controlling four servos with one Tam Valley controller, and that appears to work.


Two of the servos have reverser boards attached, so all four servos when in position will move in synchronized fashion.
Bryan Busséy
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NSE #1117
www.bbussey.net
Bridgeport & New London in N scale


John

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Re: Stiffness of Fast Track crossover points / servo mechanism redesign
« Reply #64 on: September 27, 2013, 07:12:52 PM »
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I think you guys just like to over think this stuff ..  :lol: :tommann:

Chris333

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Re: Stiffness of Fast Track crossover points / servo mechanism redesign
« Reply #65 on: September 27, 2013, 08:32:47 PM »
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The way you now have the pivot up into the benchwork closer to the turnout looks like it should work.