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> Peco double slip, Double slip in a terminus approach
DavidNZ
post 11 Aug 2012, 21:47
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Hello again
I've not been on the forum for a while as not had much time for my layout. But now the centre board (see plan earlier in the 'on my layout forum) has been built and I am working on track design for the central terminus station. My layout is basically a four track mainline in a large room with the two inner lines leading by way of a triangle to a central terminus.

see http://www.modelrailforum.com/forums/index...18227&st=15

I want the station to accomodate 8 coach trains and this need to minimise the lenght of pointwork on the station approach. As part of this I am considering using a Peco code 100 insulfrog double slip where the two sets of entry tracks meet on the Y. I notice the curve on the double-slip appears to be under 36 inches. Does anyone know if I'll have trouble running/shunting coach rakes over this without buffer locking?

I hope to work out how to put soem new photos in soon also.

Cheers
David
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kristopher1805
post 12 Aug 2012, 06:38
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This is a great point, much better than the long cross-over, I have a line of slips and they work fine, also what works can be a W made of long Y points where I go 3 into 2. Should be some shots on my blog.

I too have a 4 track main line and have 8 through lines in the main station, sadly I cannot get trains longer than 6 Mark 1's but that is pretty good anyway.

So go for it, not cheap but a really good point.
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RFS
post 12 Aug 2012, 08:09
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Whether you suffer from buffer locking depends on how you couple your stock, and how closely. For example, the latest Hornby Pullmans work very well with the Roco close coupling (not the Hornby longer version). Gangways almost touch on straight track. But if you propel them through a crossover, even a large radius one, the buffers will lock and derailment follows. The solution here is to retract the spring buffers. Strictly speaking, unless you're using 3-link couplings, buffers should always be retracted as the couplings we use on our stock basically equate to buck-eye couplings.


It might be worth laying some pieces of flexi-track curved to the same dimensions as the double-slip and doing some tests with your stock.


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barrymx5
post 12 Aug 2012, 09:13
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QUOTE (RFS @ 12 Aug 2012, 08:09) *
Whether you suffer from buffer locking depends on how you couple your stock, and how closely. For example, the latest Hornby Pullmans work very well with the Roco close coupling (not the Hornby longer version). Gangways almost touch on straight track. But if you propel them through a crossover, even a large radius one, the buffers will lock and derailment follows. The solution here is to retract the spring buffers. Strictly speaking, unless you're using 3-link couplings, buffers should always be retracted as the couplings we use on our stock basically equate to buck-eye couplings.


It might be worth laying some pieces of flexi-track curved to the same dimensions as the double-slip and doing some tests with your stock.

The article in RM this month on Customising Proprietary Coaches also recommends the Roco couplings in place of the longer Hornby look-alikes. It also explores the Keen System couplings. It claims both can traverse minimum radii of set track No. 2 which I believe is a little under 2'. Unfortunately it does not explore the reverse curve scenario.


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Barry in Somerset


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RFS
post 12 Aug 2012, 09:37
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QUOTE (barrymx5 @ 12 Aug 2012, 09:13) *
The article in RM this month on Customising Proprietary Coaches also recommends the Roco couplings in place of the longer Hornby look-alikes. It also explores the Keen System couplings. It claims both can traverse minimum radii of set track No. 2 which I believe is a little under 2'. Unfortunately it does not explore the reverse curve scenario.



A good article but it doesn't mention that the Hornby/Roco lookalikes work very well with Bachmann MK1s without the need to go to the trouble and expense of installing the Keen Systems version.

But the article doesn't mention propelling coaches where the buffer locking problem arises.


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Titan
post 12 Aug 2012, 10:08
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I had a similar issue with my terminus - space limitations meant that I had to make the station throat as short as I possible. I went down to second radius and spent some time playing around with the plan to get the absolute shortest throat I could, whilst still maintaining access to each track from either direction on each of the two main main lines.

This is what I came up with:



The key was realising that putting extra points in the main line rather than going via the central diamond meant that that diamond did not need to be a double slip and therefore could be a short diamond with larger angle, and it also removed a couple of points from the throat itself, by putting them on the mainline instead. It also I thought made the throat look more impressive as it became wider.
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Jack P
post 12 Aug 2012, 10:40
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In Auckland you say? Korr! If you ever need a hand!! biggrin.gif I'll happily come up and play trains! The drive up from wellington doesn't take that long! The double slip idea is something I will be saving a a reference for later times!


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DavidNZ
post 13 Aug 2012, 11:09
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Hi folks
Thanks for all your comments. I took one of the suggestions and tried joining different point configurations. Printing the peco point templates online I determined that the curve on the double slip is the same as the inner (tighter) radius on the peco curved point. I have a couple of these in the curved entrance to the passing station on my main line and coaches can be reversed over this without any problem.

I will just ensure that when I lay the triangle the tight curve of the double slip joins to a more gentle curve eg as on the large peco points. The main trains needing to use the curve on the double slip will be ones entering the station, so they will not be travelling fast anyway!

When I lay the track i will post some photos.

Thanks again for the input.
David

... and to my Wellington friend, have you seen the brand new train now running from Wellington to Auckland. Its amazing!
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Jack P
post 13 Aug 2012, 11:38
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QUOTE (DavidNZ @ 13 Aug 2012, 23:09) *
... and to my Wellington friend, have you seen the brand new train now running from Wellington to Auckland. Its amazing!


Would you look at that! I could bring my trains, on a train, to come play trains!

TRAINS!

Thats cool though, is it one of the newer ones? or is it an overnight service?

- Jack smile.gif


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Modelling the Southern, from the Southern Hemisphere!
My 7mm Workbench


'Imbecile!' I wasn't sure if he meant me or Mr Bulleid, But thought it impolite to ask.
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34C
post 14 Aug 2012, 08:28
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QUOTE (barrymx5 @ 12 Aug 2012, 10:13) *
The article in RM this month on Customising Proprietary Coaches also recommends the Roco couplings in place of the longer Hornby look-alikes. It also explores the Keen System couplings. It claims both can traverse minimum radii of set track No. 2 which I believe is a little under 2'. Unfortunately it does not explore the reverse curve scenario.



QUOTE (RFS @ 12 Aug 2012, 10:37) *
A good article but it doesn't mention that the Hornby/Roco lookalikes work very well with Bachmann MK1s without the need to go to the trouble and expense of installing the Keen Systems version.

But the article doesn't mention propelling coaches where the buffer locking problem arises.

I have been using the combination of the Roco in Hornby, Hornby clone of Roco in Bachmann, for some years with every success. Provided the Hornby sprung buffers are retracted, (as already mentioned) the gangway faceplates are smooth, and the mechanisms are working freely (test, remove any small moulding defects, apply graphite powder lubrication) and the wheels truly free rolling (they tend to be very good as supplied now) with operation at prototype speeds, then the following may be said:

Pulled or pushed, a train so formed will go through any track formation which the individual vehicles will consistently traverse successfully on their own as far as the end clearance managed by the camming mechanism is concerned.

So, respecting the underlined element, test one is that each vehicle needs to be able to go through the formation solo without any trouble at all. Events such as slight 'trips' on point crossings causing the occasional derailment are NBG

- because -

The italicised result is delivered by flange forces - and these are greater when pushing - and if there is any irregularity, off they will come.


Now, there has to be limit imposed by the force required to move the train and actuate the mechanisms, and the angularity imposed by the track formation. I can operate 'full size' trains (fifteen coaches) through any track formation formed on the basis of Peco's large and medium radius points and a 30 inch minimum plain curve radius, pushed or pulled. The Peco system double slip, curved point, and small radius point will not permit this and are accordingly not used on passenger rated routes and access to coach sidings. These 'no go' points are all much larger radius than the circa 18"/450mm radius of set track points

The limit must be lower on set track, gut feel says half a dozen vehicles pushed through the radius 2 reverse curves of point crossovers; and the points had better be the latest spec. (Some time ago I paid a visit to a layout with some Hornby points from the 1970s, and oh my word, the current RTR wheelsets just fell into 'the holes' at point crossings all the time. Elsewhere on the same layout there were recently purchased set track points, and here the running was much better.)
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Bear 1923
post 14 Aug 2012, 10:55
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QUOTE (Titan @ 12 Aug 2012, 10:08) *
The key was realising that putting extra points in the main line rather than going via the central diamond meant that that diamond did not need to be a double slip and therefore could be a short diamond with larger angle, and it also removed a couple of points from the throat itself, by putting them on the mainline instead. It also I thought made the throat look more impressive as it became wider.

This spreading out of the pointwork was what the railways prefered to do if they could. Double and single slips are no more of a running problem than any other pointwork can be - but they are a lot of metal and require a lot of maintenance both of which make them expensive - so the railways avoided them as far as possible (except the NER apparently).

In my experience the Peco slips are no problem at all - provided that they are not just well laid themselves but that the geometry leading into them is good. This applies to all pointwork of course. If the approach sets up a problem it won't matter what efforts are put into the slip any "issue" will never go away - because the work is bing done in the wrong place. It's pretty much the same issue as bad reverse curves - there is no absolute reason that there can't be reverse curves - they just have to be done right.

I like the idea of juggling curved points around. In fact a crossover made of opposite handed points can also make interesting wiggly variations.

Lastly, while termini do tend to be different and many modellers like to be able to get from anywhere to everywhere the ralways frequently could not achieve this even at termini. The problem was not just with how what track arrangements could be made, nor even with the signalling. The signalling, especially in semaphore days, could be a problem for Drivers to read as an increasing number of route options became an increasing number of signal arms but, where traffic was moving slowly (always a good idea when approaching a dead end) this was not the major problem. Beyond a certain level the significant issue became the interlocking of all the different bits and pieces. This was clearly established by a head-on crash (very rare in the UK) at Hull Paragon. The Inquiry established that the cause was that the lever frame in the controlling Signalbox was too long - and that the interlocking tray under it was therefore also too long with the result that parts were able to flex - this allowed the incorrect lever actions that should have been impossible - with the result that the conflicting movements could be set up and the crash happened.

IIRC the Board of Trade subsequently Required that mechanical lever frames were no more than - a lesser number than Hull Paragon that I can't recall - which physically solved the problem.

There is an advantage for all modellers if the railway practice of not being able to go everywhere from everywhere is accepted. It is simply that operation is made more interesting and even challenging. It makes the whole thing more of a puzzle. If, like the real thing, you can't just use a pilot engine to switch a rake of coaches from one platform to another but have to take them right away out of the station to a carriage siding then you get more movements and - the modeller's Holy Grail - more interest.


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