Does running on 1st raduis damage our locos?

[meatloaf]

So, only having 38" max space ive been running a 2nd radius oval ( 00 gauge )

 

I wanted to run more than one loco at once so i put in an inner 1st raduis oval. Most of my stock runs round it perfectly fine. Pretty much all diesels including the new Bachmann 47s 24s 20s. The new 37 however derails. Even the accurascale 37 and the siphons are fine on 1st radius.

 

This has got me thinking tho, does running on track below the mnimum recommended radius cause damage?

[JDW]

I suspect it's highly unlikely. I'm sure someone will come along soon and give you dire, apocalyptic warnings of wheels catching on other bits and wearing themselves down until they fall apart, but in reality, I suspect there's no risk of any real damage. The bigger problem is likely to be that the fine tolerances and many extra detail parts sometimes limit the extent of free movement of parts like bogies, coupled with factors like the increasing length of modern stock and the move from nice wide couplings to much smaller ones which won't couple easily on sharp curves (and more so the tighter the curve).

I think it's more a case of that some of the compromises needed to make the much finer models people want these days mean that they're not designed to, or recommended to run on such tight curves, and manufacturers are probably wary of people returning them "because the flanges catch on first radius curves" and such like, but as you've found many will do. Unless you can hear/see something binding and nonetheless run it for hour after hour at full speed around a circle of first radius track, I think it's a safe bet that it'll be fine. 

[RobinofLoxley]

Diesels that have four wheel bogies will probably get round but six wheels where the centre set has to displace relative to the end wheels might not. It depends how much movement they have. This is what you have experienced. So steam locos beyond 0-4-0 might be risky for the same reason. 

 

The derailment happens when the wheels can't move in line with the track and just climb out.

 

If you had space to insert even quite short sections of straight track in between the curves the situation would be improved a lot. Applies to both loops.

[DCB]

The usual problems with 1st radius is long wheelbase steam locomotives with all wheels flanged, My Bachmann 64XX does not like 2nd Radius let alone 1st Radius.  You can get most  pre Mainline/Airfix   00 gauge   RTR round 12" radius curves  because they don't have flanges on the middle wheels, with a simple change to all flanged fine scale wheels they struggle to get round 2ft radius curves.

Logically if a 47 gets round a class 37 with similar wheelbase should also get around the same curves but production tolerances such as back to back measurements and the articulation of the bogies, design and also finish, moulding  flash can be a problem.   Wear also plays a part, a well worn chassis is usually happier on sharp curves  than a brand new one, and tyre profiles, not to mention rail profiles. 

I would run the offending loco round the 2nd radius for n hour or two and clean the gauge corner, the  corner of the rails nearest to the centre line with an abrasive rubber to ensure the rails are not rough.  Dirt on the inside corners made my Locos derail on my garden layout, 

Also some current wheels are pretty poorly designed, I had to turn some Dapol bogie wheels in the lathe to keep their Mogul on the track, over width flanges and undersize treads are common and as long as a loco looks and sounds great, runs up and down a 1 metre straight test track and does not fall over in the display cabinet is all most purchasers are very satisfied.

My next layout has 12" radius curves so I think I will avoid buying a Bachmann 37.

[Michael Hodgson]

1 hour ago, DCB said:

I would run the offending loco round the 2nd radius for n hour or two and clean the gauge corner, the  corner of the rails nearest to the centre line with an abrasive rubber to ensure the rails are not rough.  Dirt on the inside corners made my Locos derail on my garden layout, 

 

If your garden railway derails on ordinary track dirt, I imagine it doesn't cope well with acorns, conkers, hedgehogs, snails etc either..

[DCB]

33 minutes ago, Michael Hodgson said:

If your garden railway derails on ordinary track dirt, I imagine it doesn't cope well with acorns, conkers, hedgehogs, snails etc either..

Slugs are the worst. I used to get excessive flange wear on Lima class 37 and very bad axle box and tyre wear on Hornby all plastic metal tyre wheelsets .  Currently derelict with weed growth and severe baseboard rot at the lower terminus,

[The Johnster]

If a loco will manage no.1 radius without derailing and running reasonably smoothly, I can’t see how it can be damaged physically by the experience (it’s mental health is another matter).  RTR is usually heavily compromised in regard to clearances for bogie swing and steam loco leading bogie/cylinder fouling in order to be capable of running on setrack radii, and excessive (in scale terms) sideplay of axles is usually incorporated.  Some Hornby Railroad pacifics have dummy flangeless trailing pony wheels to help them cope with setrack radii.  RTR locos and stock are specified for given minimum radii, and if you can get them to go around tighter radii without problems, that’s a bonus…
 

There are other issues to consider besides whether or not a loco will negotiate any tight radius, though.  Buffer clearances and couplings have to be allowed for, as does propelling.  The pickup might be compromised as well, as the excessive axle sideplay demands good contact with the wipers throughout the range of sideplay.  Tracklaying must be as nearly perfectly level and smooth between adjoining pieces as can be achieved as wheel flanges already bearing as hard as they can against the railheads will not take much persuading to ride over them and derail.  This in turn makes high demands on your baseboards’ rigidity and level surface, especially at baseboard joins.  And of course speeds must be kept low, as the faster your train is going the straighter it’s momentum will insist on making it want to go… 

 

In opposition to that, rolling resistance of loco and stock is at it’s maximum in a tight curve and the sideplay of the geared driven axles will increase the mechanical drag of the drive, along with long-term gear wear, so power must be increased to avoid the train being slowed by the drag.  Drag may cause derailment simply as a result of the inward-pulling force on the train simply toppling it over. 
 

Clearances for lineside detail and scenery need to be carefully managed as well, and don’t get me started on reverse curves.  Tight curves on gradients are a whole nother set of problems as well, as there is a corkscrew twisting effect that makes it difficult to keep the track laterally level.  

 

 To sum up, good luck to you if you’re getting away with it, but if you are using anything but locos and stock specified for 1st radius, you are pushing the design tolerances, and it may be as well in the planning stage to avoid anything with a long rigid wheelbase or distance between bogies. 

Edited June 21, 2023 by The Johnster

[meatloaf]

Ive tested a few other locos on the first radius as a redesign means the locos need to go over a first radius curve to exit the engine shed roads. All the following are fine  :

 

Accurascale 37, Hornby 56, Hornby new tooled Flying Scotsman and Dapol 73

[DavidBird]

My experience was with an older (split frame, I think) Bachmann A4. Although specified as "2nd radius of greater", it went round 1st radius curves quite happily.  I later found that the front bogie wheels were rubbing on the inside of the cylinders, and wearing a groove in them. But as this was totally invisible from the outside, and didn't seem to affect the performance, I was quite happy with it.

[Halvarras]

15 hours ago, DavidBird said:

My experience was with an older (split frame, I think) Bachmann A4. Although specified as "2nd radius of greater", it went round 1st radius curves quite happily.  I later found that the front bogie wheels were rubbing on the inside of the cylinders, and wearing a groove in them. But as this was totally invisible from the outside, and didn't seem to affect the performance, I was quite happy with it.

 

I'm surprised it didn't derail while rubbing, but instead it seems to have 'self-adjusted' to 1st radius curves. A good result I'd say👍!