Backing movements - without derailment

[Pacific231G]

Backing movements were/are used all the time on the prototype especially for goods and to avoid facing points yet I've seen rather few layouts where these can be reliably carried out for more than a few vehicles without derailments. In fact when operating other people's layouts this is often a major frustration with locos able to only pull trains not push them. Apart from obvious things like free running axles, decently laid track and avoiding overly sharp points has anyone got any ideas about the best way to achieve this- have you for instance found vehicle weight to be important? I'd really like to be able to back a twenty wagon goods train into a yard or have the station pilot propel an eight carriage empty stock working into the platform and have it stay on the track every time.

[Guest Moria]

Greetings

 

In N gauge, and I would assume in OO or larger, there are four factors that I look to to get pushimg of stock to work.

 

1) Consistent weight based on a weight per length formulae picked up from NMRA.. see below for link.

 

2) Slow speed smooth running from the loco.. a jerking loco will push things off the track

 

3) Couplings. Model rail couplings are designed to pull not push and all too often they provide a lateral push or a small catch at exactly the wrong stage in the manouver

 

4) Back to back of the wheelsets

 

The weight is important as a heavy vehicle at the end of the train with lighter in the middle makes the middle wagons twitchy, as does the loco jerking. Also bear in mind that many try to reverse far to fast with dramatic results usually needing a breakdown crane.

 

The back to back is important as you don't want any wagon attempting to crab through a point and getting confused as to what rail it should be on.

 

The coupling issue is harder to solve. In N gauge, the rapido coupling, whilst looking horrible, doesn't work to badly, but in OO with tension locks.. all the push is going through a very small buffing plate between the wagons and the slightest roughness on those plates can cause a jump.

 

By attention to the above, and the features you mentioned.. "Perfect" track, medium/large points and free running stock, I certainly have no problem either pushing 20 Buxton Lime industry hoppers into sidings, or if I am in preserved railway mode, a train of 40 4 wheel coal trucks, and that includes pusshing backwards over a double slip just for fun

 

Of all of the above, though, I have found the best improvement for reversing from the constant weight per length. and heres a link to the NMRA weighting page

 

Hope some of this helps

 

Regards

 

Graham

[10800]

You don't mention what scale, point radius and type of couplings you are using. If using three/screw-link couplings for example where the buffers actually do their job then the buffers ideally need to be sprung and the bufferheads as friction-free as possible (try smearing them with graphite from a 4B pencil). For coaches if they are buffing up with the corridor connectors then they too need to be as friction-free as possible - I hear that the Keen Systems ones are good for this being in a shiny slippery form of plastic.

[Glorious NSE]

Couplings are very important - working in HO we can reliably back 30' long freights with little bother - but kadee's are designed to work in push mode also - there is also more inherent stability in shoving bogie vehicles with body mounted couplings.

 

 

[Pacific231G]

You don't mention what scale, point radius and type of couplings you are using. If using three/screw-link couplings for example where the buffers actually do their job then the buffers ideally need to be sprung and the bufferheads as friction-free as possible (try smearing them with graphite from a 4B pencil). For coaches if they are buffing up with the corridor connectors then they too need to be as friction-free as possible - I hear that the Keen Systems ones are good for this being in a shiny slippery form of plastic.

 

No, I was really looking for general principles especially in terms of track design and other people's experience . I'm using HO European stock - wagons mostly four wheel and coaches four six or eight wheel- and gradually converting to Kadees- set wherever possible so that the buffers just touch but aren't really buffing. Points mostly three foot radius and Peco track for now but possibly SMP in future as it's pretty accurate for French double champignon (bullhead) track in HO.

 

Taking NSE's point I agree about body mounting and in the days when my layout was a US switching type don't remember having any problems with derailments. I have a couple of France Trains coaches with bogie mounted NEM couplings and though they're beautiful models they derail with monotonous regularity- even when pulled the forces coming through the bogies seem to disagree with good running- so their future will probably include body mounted #5s. There also seems to be a view that when using Kadee NEM couplings the mounts are better locked in the central position.

[BR60103]

On North American trains we used to observe that bogie-mounted couplers helped derailments. They tended to skew the bogie, forcing the wheel flanges against the rail and finding imperfections at rail joints. This was made worse by wheel flanges which were thin and sharp instead of rounded. Of course, the "NMRA" coupler added to this as it has a sideways spring.

So I wonder if this is similar to a 4-wheel wagon, pressure from front and rear making it skew, and some of those square flanges picking at rail joints.

But we need another exlanation for all those wagons that bounce off the double junction when being pulled.

[craigwelsh]

20/25g per axle weight is quite crucial in 4mm I find.

 

Tension locks never work well, especially with close coupling units, Kadees are fine.

 

Use sprung buffers if they are to do their job.

 

I've managed 16 mineral wagons in P4 before now and they were mostly rigid. Introduce an underweight wagon in the middle and it gets pushed out and off.

 

Putting bogie stock in the middle of a rake can sometime cause issues as well.

 

3ft radius points should be fine in HO.

[newport_rod]

Does anyone have any experience of the relative benefits of sprung (say Masokits or Bill Bedford), internal bearing 3-point compensation (a la MJT) and external 3-point compensation in respect of reversing freight trains in S4? Our club is planning a layout where we'll regularly have to reverse 20+ wagon trains for about 30' over a series of turnouts (typically C10 and B8). It is BR (WR) 1950s practice so most of the stock will 9- and 10-foot w/b four-wheel wagons.

[Tim Lewis]

Does anyone have any experience of the relative benefits of sprung (say Masokits or Bill Bedford), internal bearing 3-point compensation (a la MJT) and external 3-point compensation in respect of reversing freight trains in S4? Our club is planning a layout where we'll regularly have to reverse 20+ wagon trains for about 30' over a series of turnouts (typically C10 and B8). It is BR (WR) 1950s practice so most of the stock will 9- and 10-foot w/b four-wheel wagons.

 

I tend to spring almost everything. In my (albeit quite limited) experience of compensated W-irons, they don't behave anywhere near as well as sprung ones. (Not sure what you mean by 'external compensation). As noted above, you'll still need sprung buffers that actually do their job, and sensibly weighted wagons.

[Dr.Glum]

Hello All,

 

I must be doing something right, or it's all been dumb luck and ignorance on my 00 layout with 'standard' British tension-lock couplers. When I returned to modelling in 1999, I was bowled over by how well 'modern' models ran, even if you had to replace a few dodgy wobbly wheelsets. I took it as a given that I could run and shunt longs trains. Once I got my first running track up, I could back 38 wagons or 13 carriages over cross-overs or through ladders of points (numbers dictated by loop lengths).

 

It's all straight out of the box: Hornby, Bachmann, Dapol, Lima. Track is Peco (Code 100 because I didn't know any better), all electrofrog. I had 12 insulfrog, but had trouble with carriage derailments where they were used in cross-overs. IMHO the rail geometry is slightly different between the two types. I also got fed up with a black blob of rail dirt building up on the curved switch rail (and nowhere else on the layout), as this affected the running of some locos.

 

Points:

*** RTR has the potential to be very free running: if an individual isn't, it gets attention to find out why (and I don't mean just oil it). So the resistance of a complete train can be surprisingly small.

*** All track and pointwork is level, absolutely level.

*** Heresy! All track is well pinned down to MDF or contiboard, to be as flat at the railhead as I can manage. (I don't overly suffer from train noise.) Many of the Peco points that I have bought have curves along or across their track base. Most important to flatten this, especially pins near the crossing nose (frog).

*** Weighted plastic vehicles only. NO whitemetal. Keep everything as near the same as possible. Early on I weighed a load of different types of bought 4 wheel wagons, finding a range 22g to 48g (tank wagons). The few plastic kits I have are weighted up to about 35g. About 4 years ago I took the metal weights out of a couple of Bachmann Mk1s and a couple of Thompsons. They have not been subject to derailments (in fact I had to look at my records to see which they were). I should lighten all the others, so that steam outline call pull as long a train as the diesels.

*** In the few cases where I have an incline I have paid detailed (nay painstaking) attention to the start and end of slopes, so that there is a very gradual transition to the full slope. (I've just been and measured: about one and a half carriages between flat and inclined.) Inclines designed at between 1 in 42 and 1 in 96, so far.

*** (This one isn't much help for you in the planning stage.) Keep a full log of all incidents: what, where, why. Over a long enough period, it highlights rogue vehicles or trackwork.

 

Good luck!

[newport_rod]

... Not sure what you mean by 'external compensation...

 

Tim - by external I was referring to the more common type of three point compensation where the load is on (typically) pinpoint bearings outside the wheels as opposed to the MJT type RTR conversion compensation units that are equipped with internal bearings. I had heard that there were differences in the way the two types of compensation work when reversing trains and wondered if anybody had any comparative experience. I do share your preference for springing though - everything I'm making at the moment has sprung suspension.

 

Dr Glum - thanks for your comments. I think that your points on keepng the railheads as flat as possible are well made, as are your comments on the transition into gradient changes. And I wish I had your disciple to keep a full record of incidents!

 

Rod