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PostPosted: Sat Jul 11, 2009 7:00 pm 
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Joined: Mon Oct 22, 2007 10:04 am
Posts: 1
Hey all,
How many people here think it would be practical/possible to design a retarder using the StockAid and PointForm tools from fasttracks? They way it would work is, both rails of the track that a cut of cars would be rolling on are notched with the StockAid tool, and a set of long points would be filed using the point form. The long points would be soldered to a PC board tie and angled slightly towards the notched rail, one point going to the left rail, and one to the right, so they press up against it enough to create friction and slow the cars, but not so much as to bring them to a sudden stop and/or derail them. The design would be used for an ore dock, instead of the cars being pushed up to the unloader with a locomotive, the loco only shoves them to the foot of the grade, and a small winch car, runs down the grade, grabs the cars pulls them up to unload, and the cars are cut so they can roll down the grade freely, through a sprung switch (which is default set to the straight route, you don't want a set of controlled runaway hoppers going through the curved route! :mrgreen: ) and into the empty track, which has the retarders to bring the cars to a slow and controlled stop.

What do you guys think? Hit or miss? And I'd be happy to explain a bit more if you need me to.


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PostPosted: Mon Jul 13, 2009 9:39 am 
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Joined: Sat Aug 13, 2005 10:48 am
Posts: 365
Location: East Texas - USA
A working retarder in the small scales (less than 1/2" to the foot) is VERY difficult to control and have proper action be attained. The weight and rolling characteristics in model physics is way too variant. ANY friction squeezing to the wheel sets would simply do a forced halt or likely cause a derail. IF (a big if - not likely practical) ALL wheel sets were absolutely precise ("/- 0.0005") and your retarder mechanism were to be calibrated within the same one-half thousandth of clearance of control then maybe it would work sometimes.

Using small weed appearing brushes and other levels of pseudo techniques have a much higher capability of working within the tolerances of variability the models have in the physical characteristics. Momentum physics is about the weight mass in movement at real measured speeds (not scale speeds) and under real world gravity. There are some things that don't scale well - if at all. Volume is a cubed root scaling. Weight is a geometric scaling. Gravity and speed don't scale for the physics calculations. Friction is also not the same in scaling.

-ed-

_________________
-ed mccamey-
COSLAR RR - http://www.coslar.us/
NMRA Standards and Conformance Department
PROTO & FINE Scale Coordinator
I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.


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PostPosted: Mon May 17, 2010 9:25 pm 
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Joined: Wed Jun 17, 2009 1:47 am
Posts: 4
Inert Retarders, or Squeezers, would be a challenge, for sure!
I also think that unless you are using some kind of kadee coupler springs ( with much trial and error adjusting the resistance) to act as the resistance for the inert retarders it would probably just grab the car and stop it cold.
I have seen people use directed flows of air to act as a "retarder" in hump yard and in a "freewheeling ore dock" situation. both times, they had a small air compressor and used several feet of plastic tubing (the medical kind, in the case of the hump yard). The tube sat just below the track inbetween the rails, and when a car came down the hill, it met the wind from the pipe and slowed down. Much adjusting of the airflow had to be made (apparently, in HO scale, the wind *can* blow freightcars uphill) to get the speed right...but the hump yard was simply amazing.


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