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Another loco stalling on points issue

2066 Views 29 Replies 7 Participants Last post by  Graham Plowman
Apologies for regurgitating this all over again - I have looked at previous posts on the subject, but I wanted to ask a specific question, in relation to a theory about the points design/manufacture, that I couldn't find an answer to.
My layout (controlled by DCC) incorporates Peco insulfrog points. My two locos, a J94 and a class 4575 small Prairie both tend to stall at low speeds at several sets of points, as the central of the larger wheels reach the plastic of the insulfrog.
I thought I had the problem sussed when I tried applying a small weight (about 10 grams) to each loco - at the front of the J94, and the rear of the 4575. (Each loco moving slowly in a forward direction). However the issue returned, despite the weights still being in position, when running in the opposite direction. I'm starting to suspect that the locos are being lifted imperceptibly at the frog which is affecting electrical contact to the driving wheels, and the application of the weights is just enough to keep the wheels in contact at one end.
So, here's the question. Would you think that the base of plastic insulfrog mouldings are not made low enough to the base of the track, to allow the wheel flanges to pass over them unhindered. If this is correct what remedy can be taken?
Thanks for taking the time to read
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I think you will find the flanges are not contacting the bottom of the crossing moulding, Peco are pretty good at getting their mouldings right. (It takes a very coarse flange such as the old 'pizza cutter' flanges on Lima to foul on the bottom of the moulding.)

You have actually begun to identify the problem by seeing the 'balance' issue. The problem is that the point base has a slight upward bow imparted by the curved rails attempting to straighten - that's an issue Peco haven't corrected. What happens as a result is that the centre coupled wheel is raised slightly on the plastic crossing, and the loco balances with both of the coupled wheels either side out of contact with the rail - and there is no pick up!

If you take one of these points off the layout and sight along the rail top - which should be flat, i.e. horizontal - you will be able to see the upward bow. Comparison to a steel rule as a straightedge will make the slight deviation apparent. It's not gross, but it only needs a tiny airgap between tyre and rail to prevent current collection.

Cure. My preference is to glue down the point on the ply base.I have some steel blocks which sit on top for at least 24 hours as the glue goes off. (I do this on Peco live crossing points too, rail top should be horizontal, on all except intentional gradient transitions.)

Then again with the steel rule straightedge. If there is any hint of a rock across the crossing, use some fine abrasive paper on a small block to bring the plastic crossing down to match the metal rail top. Gently does it, there shouldn't be much to remove and avoid scratching the rail top.
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...My mirror tip will help you look along the tops of your rails: Using a Mirror to Align Track - Model Railways On-Line
Can't believe I forgot to mention this, it's such a good 'detector' for points already laid. Needs to be 'nailed up' somewhere in a 'hint and tips' file!
This is typical 'learn as you go'.

Yes, live crossing is superior: 'electrofrog' in old Peco speak, but now we have 'unifrog' from Peco as their new standard, which can be wired for live or dead crossing. (Peco have to offer both options as a great many layouts are still constructed on the basis of using the points for power isolation, a bodge that simply won't go away...)

Suzie is quite right about the potential for DCC shorts on dead crossing points; but you haven't mentioned your DCC system tripping when a loco stalls on a point so that presumably isn't happening at present? Some wheel forms and 'arrangements' found in RTR OO are worse than others for this problem, I can definitely point at Hornby's class 30 and the flangeless wheels in their pacific trailing trucks among current products; there are probably more. (It is possible to modify these dead crossing points to eliminate the problem completely, essentially altering them to live-crossing-alike' but that is for another day...)
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...I don't know if other newbies experience similar problems...
They certainly do. There are a great many many key pieces of know how, to get the best out of model railway based on two rail electrical pick up.

Happily you appear to have the engineer approach of understand what the evidence is revealing and learn how to systematically rectify. This is an essential because the production of RTR OO product isn't as well engineered as is truly desireable. Every single piece I own has been altered, adjusted or worked on to optimise performance and/or appearance. It does become easier as experience is obtained.
That's correct. Unfortunately you are using OO 'set track' (made to a 1960's design, and introduced by Triang-Hornby in about 1971, now manufactured by all of Hornby, Bachmann and Peco) which has had no updating to better suit DCC.

Far the better option readily available in the UK is Peco's OO 'Streamline' range which offers a much wider range of live crossing points, which hopefully you can start using in time.
On the Bachmann class 4575 they are 14.2mm to 14.3mm, whereas the EFE Rail J94 is 14.3mm to 14.4mm. I'll apply some gentle persuasion to see if the wheels will move, but I don't want to overdo it...
An owner may be able to confirm, but I suspect attempts at any such adjustment on the EFE (ex-DJM) J94 is inadvisable due to the split axle construction. Once loosened, this construction tends to deteriorate in operation.

On the Bachmann model which has a conventional steel axle, a gentle 'tap' on the axle end from a pin hammer and a drift is typically effective in slightly increasing b-t-b. Patience required, gently does it, rather than a wallop that pushes the axle out. This is the only way to perform this operation without any risk of disturbing the wheels quartering or perpendicularity to the axle.
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