Bachmann class 117 v Hornby R607

[Kit7148]

Hi, 

The new Bachmamn ckass 117 DMU states it needs a minimum of 2nd radius (18 inches). As the Hornby R607 is not quite 18 inches will this cause any running issues?

I'm at the design stage of my new layout and just need to know if the plan needs amending.

Thanks

[34theletterbetweenB&D]

That's just 'rounding off'. All RTR OO except for high price brass is made to run on 2nd Radius, because this track is present on the majority of OO layouts.

 

11 hours ago, Kit7148 said:

...I'm at the design stage of my new layout and just need to know if the plan needs amending...

However, if you are at the design stage, and there is the possibility of using larger radius curves and points then it is worth looking at. The relatively modest step of adopting 24" minimum radius using Peco's streamline is very worthwhile.

[Kit7148]

I'm building a corner layout with 3 loops comprising of 2nd, 3rd and 4th radius curves but a return on the outer loop will be via a 2nd radius curve so although the majority of the loop will be 4th radius there will be 2nd radius for the 117/159 to negotiate. 

[The Johnster]

You'll probably 'get away' with a curve very slightly tighter than the Bachmann specified minimum, but it's worth bearing in mind that a Bachmann model will have been tested on Bachmann's own track.  Pay attention as always to smooth and level laying, aligned joints to the next piece, and the avoidance of changing levels in the vicinity of turnouts.  My general advice would be always to use the largest radius you have room for, and to try to make the minimum a size above the specification, especially if there is propelling involved, as there always is with dmus.

 

If curvature is of less than 24", which I regard as the absolute minimum for Peco Streamline flexible track, it is better IMHO to use setrack curves.  Attempts to force Streamline into sub-24" territory risk distortion and the rail pulling out of gauge, and sometimes out of the chairs.  It is in fact difficult to lay flexible track accurately to curves of this radius without the aid of traksettas, and problems caused by transition curves which make the central part of the piece much sharper than you measured will result in poor running and possibly insufficient clearance for passing stock.  

 

Nearly all model railway curves, even on finescale P4 layouts, are very much sharper than scale allows, for reasons of space.  Even very sharp real running line curves, which carry severe speed limits, would need 6 or 7 feet of radius to replicate to scale in 4mm, whereas it is not unusual to use no.3 or 4 radius RTP or 3' flexi as 'express' curves capable of high speed use.  

Edited July 18, 2020 by The Johnster

[andyman7]

20 hours ago, Kit7148 said:

Hi, 

The new Bachmamn ckass 117 DMU states it needs a minimum of 2nd radius (18 inches). As the Hornby R607 is not quite 18 inches will this cause any running issues?

I'm at the design stage of my new layout and just need to know if the plan needs amending.

Thanks

 

12 minutes ago, The Johnster said:

You'll probably 'get away' with a curve very slightly tighter than the Bachmann specified minimum, but it's worth bearing in mind that a Bachmann model will have been tested on Bachmann's own track.  Pay attention as always to smooth and level laying, aligned joints to the next piece, and the avoidance of changing levels in the vicinity of turnouts.

Bachmann's own 2nd radius track is made from the old Hornby tooling and is identical, so you can take it as given that it is OK.

[Kit7148]

Thanks for your answers. It wouldn't be a problem if it was ovals but because I need to have a smaller radius (ie a 2nd radius on the outer line which is mainly 4th radius) to return the curve its had me worried. 

[Kit7148]

Footnote: I've done away with 2nd radius and only have 3rd and 4th radius on the new plan.

[pheaton]

I can  confirm 158s negotiate 2nd radius with no issues.