Dear All
 
I am hoping that someone can help me with a problem I am experiencing with a double slip shown below
 
It has been built to OO standards, along with the rest of the track on the layout (which with the exception of another double slip that I have yet to finish trouble shooting, all works ok).   There have been a number of issues with the build of the slip but I think they have been now resolved (mostly around the gauge around the slip rails and the quality of the K checks.  My intention is to lift the whole point and completely rebuild improving from the lessons learnt so far.
 
However there is one area which is still giving me problems, when a train exits the branch platform (1) and heads towards the branch (4) the majority of times it will go straight on through the slip road towards 3 (or some axles will go to 3 while others go to 4 causing a derailment. 
 
Before I rebuild the slip, my concern is that this is being caused (or at least compounded by) the reverse curve between the platform and the slip. 
 
I would welcome any advice as to whether this is the case, (or conversely if I have made a silly error on the slip design), and whether it is possible to improve the design in order to mitigate the issue.  Would an extended check rail through the vee at (1) assist in keeping the loco / coaches to the right hand side of the track guiding them the right way through the slip?
 
When finished the main operations will be a 4500 class with between 2 and 5 coaches going heading from the platform (1) to Kingsbridge (4), or the 4500 taking through coaches from Kingsbridge for Paddington from the platform (1) to the up main via the single slip at (3).
 
All other points are fully built, hence limitations on routes 2 (next point starts circa 1 inch from the end of the vee), on route 3 there is a 3 inch curve between the double slip and the single slip on the down main, while on 4 there is approximately a 12inch curve before the next point.
 
I will upload the box file later when I get home, but for the moment I have attached a diagram below

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message ref: 22635

Hi,

Welcome to Templot Club.

It's difficult to see much from your small image, but we probably don't need to.

A curved slip in "00 Standards" is always going to be difficult. The wide flangeways don't provide for sufficient (or with some wheels, any) checking at fixed K-crossings at the flat angles suitable for adding slip roads. Even straight slips are tricky.

One solution is to change to narrower 1.0mm flangeways as 4-SF (00-SF), the same as EM. You can do that on individual areas of trackwork without needing to change the rest of the layout. But if you do that you MUST reprint the template in 4-SF for the reduced 16.2mm gauge and rebuild from scratch, don't try to adjust an existing slip or diamond from 16.5mm to 16.2mm because it will be too long between the vees and it will be physically impossible for the rails to align properly.

Templot can now create slips, including curved ones, with a couple of clicks.

But even after all that it is still going to be tricky with fixed K-crossings for a curved slip.

The much better solution and strongly recommended is to build it as a switch diamond with movable K-crossings instead. That is actually much easier to build because there are no K-crossing check rails to find space for. But it does mean you will need two extra point motors (or only one, with a suitable rocking crank)*.

To create the template for that, click real > K-crossing options > movable K-crossings menu item.

*If they are Tortoise pattern point motors and fitted the opposite way round from one another to make room, you can drive them both in parallel from a single panel switch.

regards,

Martin.

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message ref: 22636

Thanks Martin for the feedback, I have now uploaded the .box file.

I think I understand what you are saying regarding the K crossings, can definitely see how both solutions would result in improved running (much less of a bounce through the gap). However I am not so clear on how it will resolve the more fundamental issue, in that the derailment is being caused at the switch area. Would tightening the gauge to SF standards through the Vee area potentially provide similar improvement here (in that there will be much less slop between wheels and rail, hence less chance of a wheel riding up and over the switch rail?)

Thanks again
Rich
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message ref: 22638

Hi Rich,

There isn't any significant difference between a switch in a slip and any other switch.

Most switch over-riding problems are caused by the switch being under gauge. And that is nearly always caused by not providing a sufficient set in the diverging stock rail. It's very important to check that the stock gauge is correct (or at least, not too small) before fitting the switch blades.

For a slip, this applies to the outer stock rails. They will need a set at both ends, so some careful matching to the template when marking the set positions is important.

More about all that here:

 http://85a.co.uk/forum/view_topic.php?id=491&forum_id=1

regards,

Martin.

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message ref: 22640

Thank again, so in conclusion the reverse curve from the platform into the slip shouldn't be an issue (assuming that the switch area has been built correctly).

As a result I think I will redraw the double slip with moveable K crossings. Accept the need to buy an additional two Tortoise motors in order to power it, and then fully lift and rebuild (this time I think I will build it off layout so that it can be tested in isolation prior to installing.) Hopefully that will resolve the final issue. First of all I have a couple of P4 points which need making for my exhibition project, so I think building these will be good practice before returning to working in OO for Brent's slip!
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message ref: 22641

RPEDDER wrote: Thanks Martin for the feedback, I have now uploaded the .box file.

I think I understand what you are saying regarding the K crossings, can definitely see how both solutions would result in improved running (much less of a bounce through the gap). However I am not so clear on how it will resolve the more fundamental issue, in that the derailment is being caused at the switch area. Would tightening the gauge to SF standards through the Vee area potentially provide similar improvement here (in that there will be much less slop between wheels and rail, hence less chance of a wheel riding up and over the switch rail?)

Thanks again
RichJust a thought. How are the tie-bars for your switches arranged? Are you using a single tie-bar for both switches at one end? If so you'd need to get it spot on so that both corresponding switch blades close together.

I wondered because your problem sounds a bit like a switch blade not closing fully.

Cheers
Nigel

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message ref: 22642