|
|
Post by jamesbrodie67281 on Jan 30, 2015 12:21:23 GMT -8
Gents, This topic must have been asked umpteen times before but this oldish tame Limey is a bit iggerant (sic) of some descriptions. Please could you help/guide me.
Pointwork (switches) seem to be identified by a number but I work in radii described in inches or feet radius.
Is the higher number ie 7.5 denoting the larger radius ? So what radius is shewn by what number please.
Regards to you all JB.
|
|
|
|
Post by grahamline on Jan 30, 2015 13:19:06 GMT -8
The number is the frog's ratio of departure, and most frogs in US and I believe UK practice are straight, not curved. A #4 frog is a right triangle with the shortest side one unit, and the intermediate side four units. On the diverging route beyond the frog, you can swing any radius you choose. What you're looking for is the "substitution radius." This is what Tim Warris of Fast Tracks said in a discussion on his site at fast-tracks.net/forums/viewtopic.php?f=4&t=105 . Hi, The term substitution radius refers to the radius that a turnout can be placed into without altering the radius. Even though a turnout will have a minimum radius in its curvature, that does not necessarily mean that it will "drop" into that radius. For example, an HO scale #6 turnout will have a 43" minimum radius, but can be dropped into a 56" curve, according to John Armstrong in his "Track Planning for Realistic Operation" book. Other substitution radii in HO are: #4 29" #5 36" #6 56" #8 110" Hope this helps! _________________ Cheers! Tim Warris Fast Tracks www.fast-tracks.netservice@fast-tracks.net |
|
|
|
Post by jamesbrodie67281 on Jan 30, 2015 15:15:19 GMT -8
Graham, Thanks for your reply and the frog or crossing info. I model 0 gauge and mainly build my own points but as time is flying by I may have to purchase some points and use the larger size. I have in the past when a sharp radius point was needed used a transition curve each side of the point to ease the rolling stock into and out of the sharper radius. I do have 00 trackwork for my 0n30 models and use Peco six foot radius points and for the duak gauge part add some single rail soldered to suit 28mm back to back for where the 0 gauge models infringe.
Can I presume that an ho no 4 frog 20" would be equal to 40" in 0 gauge ?.
Jim Brodie.
|
|
|
|
Post by grahamline on Jan 30, 2015 15:31:43 GMT -8
I imagine doubling the radius would be a safe approximation. My brother barely let me near his O scale trains and I've been in HO & HOe ever since. If you are building your own switches, you can always curve them through the frog if that suits your plans and skills. Peco used to make a lot of information available. I haven't dealt with them myself in several years.
|
|
