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 Post subject: Hinge point mininum
PostPosted: Sun Feb 24, 2008 8:09 pm 
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Joined: Wed Jan 03, 2007 1:18 pm
Posts: 84
What is the minimum length required to have a turnout act as a hinge point turnout.

For example, is the 'H' PC Board tie on a #6 turnout, at approximately six centimetres from the throwbar PC board tie, far enough away to work without having to do much in the way of extra builds (cutting the rail, soldering in a rail joiner, etc.)?

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Last edited by sambear on Sun Feb 24, 2008 8:55 pm, edited 1 time in total.

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 Post subject:
PostPosted: Sun Feb 24, 2008 8:22 pm 
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Joined: Sat Aug 13, 2005 10:48 am
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Location: East Texas - USA
sambear,

Not sure of your terminology. Hinge point means a switchblade that is hinged (e.g., one that is not continuous, has some form of hinge - rail base and head cut, all cut through with rail joiner as a slide, spiked each side, various options - etc). IF the blade is truly hinged - then the shortest you would want would be the prototypical 16'-6" length (which is actually closer than the 'H' PC tie).

If your are building with a continuous switch blade and closure rail and relying on rail 'flex' for the point movement, then you want a much longer free flex length - depending on the rail size you are using. For the design specified rail of the fixture - the "S" PC tie is the attachment point. You MAY get by with a shorter distance (say with code70 in the code 83 fixture) - but the bending stress will be more.

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-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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 Post subject:
PostPosted: Sun Feb 24, 2008 8:52 pm 
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So would that mean I do the same work as shown on the 'UG06' document for the three way turnout?

From pages 25-29 in that pdf, after the closure rail is cut, the document shows a rail joiner being soldered to the rail. I still have to read and learn more to understand how to do that allowing the hinge (switchblade) to move.

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 Post subject:
PostPosted: Mon Feb 25, 2008 9:52 am 
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Joined: Sat Aug 13, 2005 10:48 am
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Location: East Texas - USA
sambear,

Yes - learning and acquiring the skill to construct a hinged switch blade point is important. Three way turnouts, the long double slips with the center moving points, certain configurations of lap and some gantlet turnouts will require the geometry of very short points that can not flex bend.

A 'standard' turnout can be reliably constructed with a continuous flexing switch blade and closure combination. This is the easiest of construction approaches with the only slight expense of some induced mechanical stress.

Prototype turnouts have a hinged point and the construction of one in the model will give greater realism to the trackwork. The extra effort gives not only the realism, but also will measurably reduce the throw rod stress and improve long term reliability. Hinging not only the heal at the closure join, but also a free turning pivot at the throw rod has many mechanical advantages and reliability rewards. The effort is more, does require additional skills, but may be very necessary for the unique turnout configurations many want, need, or just desire.

_________________
-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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