Subject:
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Re: Grade Crossing Signal Thingy...
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Newsgroups:
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lugnet.trains
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Date:
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Fri, 17 Dec 2004 20:57:30 GMT
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Viewed:
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1302 times
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I have a couple of newbie questions about things like this.
First, how do you protect the motor? In this particular design it looks like
you could actually rotate the arm past vertical, which I guess isn't a problem
until you hit the ground on the other side. Or, if you were to go the other
way, you could lower the arm instead of raising it, again smashing into the
ground. At that point, if you don't let up quick, aren't you going to strip the
motor?
This might not be a problem for AFOLs, but I'd like to have some things like
this on a layout that would be played with by my 4-year-old, so it needs to be
robust to abuse. Should I always go though a clutch gear? Or is there some
other clever trick to cut the power to the motor when it goes too far?
A similar question applies to those nifty motorized track switches I see used at
shows. There, even with an adult operator, it looks like it'd be easy to hold
the button down too long and end up frying the motor. Why isn't this a problem?
Next: when controlling a crossing like this from an RCX, is cumulated error a
problem? I'm talking about imprecision in the position of the arm after many
up/down cycles. I don't see a rotation sensor on this unit, so how does the RCX
know exactly where the arm is? Or is the RCX/motor combo so precise that this
isn't a problem?
Thanks,
- Joe
(Told you they were newbie questions!)
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Message has 3 Replies:
 | | Re: Grade Crossing Signal Thingy...
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| (...) One approach is to use a linkage mechanism in which the gate is driven by a link that no matter how the motor rotates, never takes the gate below horizontal or beyond directly vertical. That of course introduces other issues, such as knowing (...) (20 years ago, 17-Dec-04, to lugnet.trains)
| | | Re: Grade Crossing Signal Thingy...
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| (...) Easiest way is to have a stop of some kind at both extremeties of movement, and introduce some kind of slip into the drive mechanism, like rubber bands or a slip clutch (URL) each cycle runs the motor longer than it needs, and the clutch slips (...) (20 years ago, 17-Dec-04, to lugnet.trains)
| | | Re: Grade Crossing Signal Thingy...
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| (...) The way that my design ended up, that isn't an issue. The arm just goes up and down as the wheel/motor rotates. It doesn't go past horizontal or vertical positions (by luck, not design :^) ) (...) There's a weak spot in my signals above the (...) (20 years ago, 18-Dec-04, to lugnet.trains)
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Message is in Reply To:
| | Grade Crossing Signal Thingy...
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| What the heck are they called? I know the whole thing is referred to as a grade crossing, but other than crossbucks, I don't know what to call it. Anyways, I cooked this up recently: (3 URLs) It's going to be part of a larger module with a road (...) (20 years ago, 16-Dec-04, to lugnet.trains, FTX)
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