Curved/tamgent turnout?

Discussion in 'Track Planning' started by BigJim, May 31, 2007.

  1. BigJim

    BigJim Member

    Like many newbies working on track planning and looking at available turnouts I wondered why I couldn't find one that would let you branch off of a curve with a straight track. After my success building a "pointless" or gantlet turnout I thought I would try making one. It has a 28" curve with a straight exit. Only took slight modification to a #6 frog. It seems to work fine. Now the question is why don't the sell something like this? Am I missing something? Is this one of those "not in prototype so not in model" situations?

    Sure makes drawing the layout easy:wave:
  2. steamhead

    steamhead Active Member

    Hi...I might be wrong, but Peco turnouts (the small, medium and large ones) follow through the turnout with a constant radius...Although the "entry" ( a couple of inches at most) is straight...
  3. Russ Bellinis

    Russ Bellinis Active Member

    I think it is probably a case of the manufacturers only making certain standard design turnouts. There are a lot of different turnout designs they could produce, but if they are not popular enough, the cost would get prohibitive.
  4. Triplex

    Triplex Active Member

    Fleischmann and other European manufacturers also make turnouts like this.

    In North America, this style was mostly used for tight-radius turnouts on trolley lines. Maybe it is/was found on major European railroads?
  5. BigJim

    BigJim Member


    It is the little straight sections that make it not fit on a curve and have the same internal radius. For example a #4 turnout has an internal radius of 15" and a substitution radius of 28". So you can put this in a 28" radius curve without much adjustment but your equipment is going to see a 15" (very tight) section in the middle of the turnout.

    I wanted a turnout that is approx. 28" radius all the way through. This would be similar to a curved turnout except the outside curve is not curved at all but leaves at a tangent (straight).
  6. Triplex

    Triplex Active Member

    Peco turnouts aren't numbered. The distinction isn't at the point end, but the frog end. A numbered tunout has a straight section through and beyond the frog. A continuous-radius turnout like Peco or Fleischmann has a curved frog.
  7. steamhead

    steamhead Active Member

    Yes, I can see where a constant radius is more suitable for this application, and would make for "cleaner" lines, but from a commercial point of view, I think that the "traditional" presentation has more going for it. Although I do recognize that there are hundreds of instances where this particular set-up has a lot of advantages over the traditional one.
    How is this handled in the prototype..??
  8. BigJim

    BigJim Member

    I guess when you have a box of frogs, rail cutting equipment, some thermite, spikes and ties you can do what needs to be done. In HO you only need to cut away about 0.003" of the center of the side of the frog to match the curve. Since the real frogs are hardened I think they still need to go straight through the frog. Since our wheels and flanges are much larger than proper scale we can get away with a lot looser tolerances and much tighter curves. I don't think you will ever see a #4 or #5 frog in prototype.
  9. zedob

    zedob Member

    I was looking at the same problem on my layout last night. I was playing around with a branch from the curved mainline and I didn't much care for the jog through a #6 turnout. I was planning on a wide sweeping curve throught the yard and that would kill the look. I plan on using CVties and turnout ties, which allow for curving, but I don't know if they will allow for a constant curved track and a straight diverging(?) track.

    As for why manufacturers don't make them is just a supply and demand thing. Although, it would be nice if they did offer bigger selection.

    Handlaying is for people who don't want to bother with the the limited selection of commercially available turnouts and RTR crowd are pepole who don't want to bother with handlaying. Both groups have their pros and cons, it's just that one group gets to run thier trains sooner.:mrgreen:
  10. BigJim

    BigJim Member

    I would think that it would be very popular if anybody made one. Sure makes layout easy. Draw a circle / draw a line.

    Although I now have my double crossover assembly fixture (great fun - also works to make standard turnouts) it won't make the curved/tangent one.

    I would highly recommend getting at least the Fast-Tracks point form tool if you are going to make any turnouts. Get the one for the double crossover as it has the frog, point and crossing angles.

    There are multiple remote sales (internet & phone) people for Fast-Tracks. I recommend Jim (not me) at Fast Tracks | . Give him a call at (888) 252 3895 ext. 709 and I think you can get a discount.
  11. Bones

    Bones Member

    This does allow allow for a straight route, and a constant curved route.

    It's all in the points. Just modify your geometry to allow a straight rail to form the point for your diverging route, and a curved rail for the constant.
    Only one rail ever does any work in your points.

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