Help with point radius

[Mossala Hill]

Could someone please direct me to a conversion of point/curve numbers to radius? I know that LGB R3 is about 4 ft, (1.2M) but what about AMS #6 and #8?

Thanks,

Rob

 

[Rhinochugger]

I was advised that these US tuunouts are not built to a true radius and follow 1:1 practice in their layout on plan.

As I'm not very well versed in 1:1 point layouts (apart from the fact that Nitwork Rail have been undertaking massive upgrades improvements post Grayrigg) I can't help much more than that.

There may be some info on one of the US large scale websites.
I have one Aristo #6 and one USAT #6 - they are both different in the amount that they offset from the straight, but I've assumed that is just a question of the length of track provided on the turnout.

 

[ntpntpntp]

I was advised that these US tuunouts are not built to a true radius and follow 1:1 practice in their layout on plan.

Probably referring to the practice of keeping the trackwork straight on the way through the frog, in both normal and diverging routes. Unlike a typical toy train point where the diverging route is curved all the way through the frog (ie. you can lay a piece of curved track on top of the point and it will match exactly)

 

[Gizzy]

I Googled No 6 Switch and quote this from Wikipedia:

Classification
The divergence and length of a switch is determined by the angle of the frog (the point in the switch where two rails cross, see below) and the angle or curvature of the switch blades. The length and placement of the other components are determined from this using established formulas and standards. This divergence is measured as the number of units of length for a single unit of separation.
In North America this is generally referred to as a switch's "number". For example, on a "number 12" switch, the rails are one unit apart at a distance of twelve units from the center of the frog. In the United Kingdom points and crossings using chaired bullhead rail would be referred to using a letter and number combination. The letter would define the length (and hence the radius) of the switch blades and the number would define the angle of the crossing (frog). Thus an A7 turnout would be very short and likely only to be found in tight places like dockyards whereas an E12 would be found as a fairly high speed turnout on a mainline.

As AMS is a US product I guess that the No 6 designation mirrors that of the prototype....

http://en.wikipedia.org/wiki/Railroad_switch

 

[MRail]

...referring to the practice of keeping the trackwork straight on the way through the frog, in both normal and diverging routes. Unlike a typical toy train point where the diverging route is curved all the way through the frog (ie. you can lay a piece of curved track on top of the point and it will match exactly)

This has been baffling me.
I photographed some pointwork at Porthmadog a year or so ago.

On both the FR and the BR std gauge, the diverging line appears to be curved right through.

 

[mmts]

...referring to the practice of keeping the trackwork straight on the way through the frog, in both normal and diverging routes. Unlike a typical toy train point where the diverging route is curved all the way through the frog (ie. you can lay a piece of curved track on top of the point and it will match exactly)

This has been baffling me.
I photographed some pointwork at Porthmadog a year or so ago.

On both the FR and the BR std gauge, the diverging line appears to be curved right through.

Quick someone get Gizzy a damp towel.............he'll come over all funny at the sight of all that point-work

 

[Gizzy]

...referring to the practice of keeping the trackwork straight on the way through the frog, in both normal and diverging routes. Unlike a typical toy train point where the diverging route is curved all the way through the frog (ie. you can lay a piece of curved track on top of the point and it will match exactly)

This has been baffling me.
I photographed some pointwork at Porthmadog a year or so ago.

On both the FR and the BR std gauge, the diverging line appears to be curved right through.

Quick someone get Gizzy a damp towel.............he'll come over all funny at the sight of all that point-work

Too late.... :love:

 

[spike]

A turnout's number expresses how much it will cause a train to diverge when it is thrown. The number is calculated by taking the number of units of forward travel for one unit of divergence. For example, if after traveling six inches from the point of divergence the train has diverged one inch, then you have crossed a #6 turnout.

 

[ntpntpntp]

...referring to the practice of keeping the trackwork straight on the way through the frog, in both normal and diverging routes. Unlike a typical toy train point where the diverging route is curved all the way through the frog (ie. you can lay a piece of curved track on top of the point and it will match exactly)

This has been baffling me.
I photographed some pointwork at Porthmadog a year or so ago.
On both the FR and the BR std gauge, the diverging line appears to be curved right through.

Yeah, I know what you mean. My understanding is that keeping the trackwork straight on the diverging route through the frog is more US practice than UK (same as rhinochugger originally mentioned I think).

I found this text (borrowed from the following link):

[size=14pt][size=14pt][size=14pt]http://bellsandwhistles.us/modelrailroading/Clinic08_handout.pdf [/size][/size][/size]​

[size=14pt][size=14pt][/size][/size]​

The curved leg is not smooth.

American prototype turnout has straight switch-point rails and straight rails through the frog on both legs of the turnout. On the curved leg the switch-point rail makes an angle of about 1°​

or 2° when the point is against the straight stock rail, which is a sudden change for the wheels. Thus, the curved leg is not a continuous curve but is a combination of angle-straight-curve-straight.​

In the prototype, straight rail through the frog promotes reliable tracking and simplifies the stocking of right and left-hand turnout parts. A large radius closure curve minimizes the effect of this.​

​

 

[Mossala Hill]

Thanks for all the replies. It's as I feared, the number gives you the angle of divergence at the exit of the diverging road but the (minimum) radius depends on the actual combination of straight and curved sections, and this will be something less than a calculation assuming that the diverging road has a constant curvature over its length.
I'm still surprised that some makers of track, e.g. A.M.S. don't quote the minimum radius, given that this will dictate whether a given loco can negotiate a curve.

Rob

 

[alecescolme]

Rob,
#6 is about 9.75ft radius
#8 is about 15.5ft radius
http://www.llagastrack.com/pricelist.html

Alec.

 

[Mossala Hill]

Alec,
That's really useful, cheers.
The cast frogs and point blades on the Llagas site almost tempt me to have a go at putting a point together. Have you used any of their stuff? Is it compatible with Peco G45? Can't see a U.K. dealer listed but they do say it's in use here.

Rob

Rob,
#6 is about 9.75ft radius
#8 is about 15.5ft radius
http://www.llagastrack.com/pricelist.html

Alec.

 

[Gavin Sowry]

As usual, nothing is simple, or standardised. With the 'straight' frogs, there are two ways of measuring the divergence..... the English 1 in x method, or the American # method. A 1 in 9 turnout is NOT the same as a #9. The English system uses the ration as a tan
when working out the angle, and the Yanks use 2 times half the tan ratio. Get your calculater out and work it out, you will see the difference.

 

[Sea Lion]

Alec,
That's really useful, cheers.
The cast frogs and point blades on the Llagas site almost tempt me to have a go at putting a point together. Have you used any of their stuff? Is it compatible with Peco G45? Can't see a U.K. dealer listed but they do say it's in use here.

Rob

If it helps Peco are about to bring out scratch build points parts for G-45 . So far I've had samples in of the sleepering (with end caps), standard chairs, and slide chairs. Presumably the switches and crossings will be appearing soon.

Happy steamings,

John

 

[alecescolme]

Rob, I have not personally used any of thier stuff, but comes highly recomended.
Should be fine with Peco, just that the Peco has a narrow base.
I grind my own parts with code 250 rail from Back2Bay6.

Alec.