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Tight radius switches
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 Posted: Sat Mar 16th, 2013 03:12 am
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Herb Kephart
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TIGHT RADIUS SWITCHES


Decided that that was a better title than “Trolley Switches”, since this method of construction is also applicable to industrial railways and even the “micros” and “minnies” that folks with a lack of space build. Not the thing for Class 1 railroads, one of the key features in having these work is the very fact that the diverging track takes off on such a great (relative) angle –or low frog number. One benefit of that, is the frog of the switch does not need the two short guard or “wing” rails immediately adjacent to the frog point. This is because their primary function is to support the tread of the wheel while it goes over the gap in the diverging rail. The larger divergent angle, the shorter that gap becomes-- with a #12 or 14 switch the gap could be as much as a half inch, or more. Actually, a lot of this can be eliminated by filling the flangeways between the point and the wing rails with solder, and filing the solder to just the right depth that the wheels ride on their flanges through the gap. Also, the guard rails opposite the frog are missing also. The short gap with tight radii really doesn't require this, for the same reason


Part of the basis of this whole system is working with what the car “wants” to do. It wants to keep going straight on straight track, and it wants to run the flanges against the outside rail on a curve.


First, lets look at the “pointless” switch—NOT meaning one without a reason for it's existence, but one with no points.






Notice the switch at the bottom of the picture. Cars can approach this switch from three tracks-the one coming from the top left, the one from the left, and the one from the bottom. The first two pose no problem—the lack of a proper point is not important—the car will go through –just as it would (two rail electrics ignored for the moment) if there were points, and the car pushed the points over. Now if the car comes to the switch from the bottom of the photo—because the approach track is on a broad LH curve (admittedly not readily evident in the photo, because not enough of the track before the switch is shown) the car will be pressing against the right hand rail, and the car will take the straighter of the two routes. So IF the intended route is straight, or the straighter of the two, this is all that is needed.
It is possible to have the car always take the curved track also, but it takes a little more attention to the (non) point area. If the switch in the above example had a short guard rail on the LH rail just before the points, that guard rail would pull the flanges away from the RH rail, and in the short distance before they got to the gap where the points “should” be they wouldn't have had a chance to move over again to the RH rail BEFORE they got to the piece of rail that would be the RH point, if there was one. So the car takes the curved route. This isn't as cut and dried, or as foolproof as the first example, it requires some fiddling with track gauge, length of the afore mentioned guard rail, and most importantly the distance from the guard rail, to the gap where the points are missing. A little variation here can make the difference between success and failure`--but it CAN be done, and I have had probably a dozen switches on past layouts over the years where this was used successfully. Actually, the guard rail isn't even needed if the track approaching the point area is curved so that the flanges are pushing against the rail that continues as the diverging route—but this creates a rather vicious S curve that is OK with a single car, but might cause major problems with coupled cars.


Photo and model by TRAMCAR TREV

  They are just great shots that show very plainly what I'm about to describe.

The side with a point is just like a railroad point—except shorter, because of the smaller radius of the diverging track. The other side is exactly like the pointless switch described above, Since filing points is the least enjoyable part of hand laying a switch, this cuts the suffering in half. On occasion, the real railroads used this type of switch-- The Philadelphia Belt Line Railroad, an entity that owned no cars or locos—but had plenty of trackage in the middle of Dock Street up and down the Phila. harbor front, used them on the track that was surrounded with paving. A “switch iron”, basicly a crowbar with a loop at the handle end was used to throw the point. The point had a very heavy over center spring on the pivot pin, and when the switch iron would pry it past the mid point of it's travel the point would snap to the other position.


The real thing usually had the moving point on the side that had the curved rail. The travel of the point was restricted to the amount that would cause the surface of the point that nested up against the running rail, to become a guard rail—catching the flange and pulling it over away from the “pointless” point.
Notice that is the way that the model switch is made. If you are running live overhead wire, and all rails are the same polarity (or if you are using on board batteries and radio control, and NO wires above or below) this will work fine. If, however, you are running two rail, you will get a short from the flange touching the guard side of the point. In this case, put the moving point on the straight side of the switch-- there, it can open farther so that the flange wont touch it, Car will take straight route when point is open, just as it does with the pointless type.



Again, TRAMCAR TREVS work

A third photo shows a wye switch. Note that the modeler had to combine several things that I have mentioned above. The guard rail before the switch, and the back side of the point acting as a guard.


Questions? Ask!!




Herb



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 Posted: Sat Mar 16th, 2013 03:28 am
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W C Greene
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Quite well written, Mr. Kephart. Even a doofus like me can understand this. BTW, every time I ride the McKinney Ave trolley here in Dallas, I am amazed at how the cars can go through the pointess and single point switches (the crew calls them switches, not turnouts). I love the BUMP and WHANG they make...lovely!

Woodie



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 Posted: Sat Mar 16th, 2013 04:23 am
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Kitbash0n30
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Tile between rails is interesting touch. Oh, brain just registered that it evokes cobblestones.

Last edited on Sat Mar 16th, 2013 04:28 am by Kitbash0n30



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 Posted: Sat Mar 16th, 2013 07:09 am
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Across the Bridge
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Herb Kephart wrote:
Now to illustrate the next type of switch—the single point. I am  showing some pictures that I got off the internet, a while back, that were not credited either as to the modeler or the photographer.

That would be Tramcar Trev from the Lanyon Valley Electric Tramway...... http://trevstramway.blogspot.com.au/?zx=8ea36f98629157e2




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 Posted: Sat Mar 16th, 2013 03:42 pm
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Herb Kephart
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Thank you, but the link comes up as "blog not found" for me.

Do you know a way to contact Trev? if you know his Email, please PM me.

Again, thanks!

Herb



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 Posted: Sun Mar 17th, 2013 12:33 am
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Tramcar Trev
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G'day Cobbers, tis me Tramcar Trev.
Ok now the pictures you have posted, I look at it this way anything I post on the net is for others to see and enjoy and TO USE for non financial gain. If I didn't want my work exposed I wouldn't post pics or update my blog; http://trevs-tramway.blogspot.com.au/

I realise some are sensitive about what is posted but that in my opinion defies the 1st law of Net Sense. If you don't want it seen or used don't post it.... This is the reason I don't post my now infamous sex tapes online... Sorry that's some Australian humour:glad:
On the topic of points my personal piece de resistance is my 3 way Car yard fan. can't work out how to post pics here yet but they are on my blog with construction details.
http://trevs-tramway.blogspot.com.au/search?updated-max=2013-01-12T19:11:00%2B11:00&max-results=20&start=10&by-date=false

Last edited on Sun Mar 17th, 2013 01:15 am by Tramcar Trev



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 Posted: Sun Mar 17th, 2013 03:04 am
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Herb Kephart
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OH S**T

You mean I missed the tapes?

Thank you Trev! Your thoughts are right in line with mine re the net, Mate.

Herb



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 Posted: Sun Mar 17th, 2013 01:07 pm
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Bernd
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Hey Trev,

A fellow DYIer, all right. :glad: :glad: :glad: :glad:

Going to have to peruse your blog. I'm very interested in doing etchings. I've also done my own boards. Have to compliment you on your boards. They sure came out better than mine did when I tried it.

Bernd

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 Posted: Sun Mar 17th, 2013 02:57 pm
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W C Greene
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The only time I got upset with someone posting photos of my junk on the net was when a "gent" had photos of the Mogollon Railway on his "blog" and outright stated that they were his railroad! I would have never known this until a couple of guys informed me about it. I wrote a message on the blogger's comments about this and...next day, the blog and everything was gone!

Now, back to tight radius curves. I saw a couple of those at the mall yesterday. I hope Pam doesn't read this.

Woodie



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 Posted: Sun Mar 17th, 2013 10:21 pm
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Tramcar Trev
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Bernd wrote:
Hey Trev,

A fellow DYIer, all right. :glad: :glad: :glad: :glad:

Going to have to peruse your blog. I'm very interested in doing etchings. I've also done my own boards. Have to compliment you on your boards. They sure came out better than mine did when I tried it.

Bernd


Bernd, I found etching to be a super way to actually "Make things" rather than try and cut out fine detail with a jewelers saw. You can see what I mean if you can find the post on "etching for amateurs" in my blog, no reason it could not be repeated here if anyone wants it, as I say I post stuff on my blog to help fellow enthusiasts....



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There once was a man who said Damn!!
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A creature that moves
in predestinate groves
I'm not a Bus, I'm a tram
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