Code 40 turnout derailments with N stock - help!

[jonhinds]

Hi all

 

I’ve installed a fiNetrax AV7 FB turnout which runs Mk1 coach stock and Class 47 just fine. However, none of my DMUs will run correctly, as the maximum throw of the straight point blade on the through route isn’t enough to provide clearance for the wheel sets, which jump onto the diverging line. It’s probably about a third of a millimetre out! Everything is glued and soldered so I can’t tweak the turnout, and I can only assume that I assembled it a bit sloppily as a first-time effort.

 

Is there anything I can do here, or is this a lost cause? There seems to be a fair bit of side-to-side give on the DMU wheelsets; are there any aftermarket N wheels that run a bit wider? The DMU sets in question are BachFar 101, 150 and Dapol 142, 156.

 

 

 

 

[dhjgreen]

For chance of helpful replies in handbuilt track forum, I will ask for it to be moved

[scottystitch]

32 minutes ago, jonhinds said:

Hi all

 

I’ve installed a fiNetrax AV7 FB turnout which runs Mk1 coach stock and Class 47 just fine. However, none of my DMUs will run correctly, as the maximum throw of the straight point blade on the through route isn’t enough to provide clearance for the wheel sets, which jump onto the diverging line. It’s probably about a third of a millimetre out! Everything is glued and soldered so I can’t tweak the turnout, and I can only assume that I assembled it a bit sloppily as a first-time effort.

 

Is there anything I can do here, or is this a lost cause? There seems to be a fair bit of side-to-side give on the DMU wheelsets; are there any aftermarket N wheels that run a bit wider? The DMU sets in question are BachFar 101, 150 and Dapol 142, 156.

 

 

 

 

Perhaps an obvious question, but have you checked the back to back dimensions of the wheelsets of all stock your running?

 

Best

Scott.

[jamespetts]

You could try first of all checking and adjusting these wheelsets with a back to back gauge. I am not entirely clear as to what you mean by the straight point blade on the through route not providing enough clearance, however, as there is more than one possible permutation of what this could mean. I have often found with these turnouts that, if I do not file the switch blades enough, the track  goes out of gauge at the point where the switch rail meets the stock rail and wheels can be forced up and out of the track, causing derailments. Carefully filing the point blades after the points have been laid can solve this.

 

On other occasions, the switch blades can be in the wrong position if not soldered to precisely the right point of the metal attachment points; these can be carefully re-soldered in situ. Use a soldering iron with a small flat tip, either a chisel or a bevel tip of 1mm in size.

[jonhinds]

27 minutes ago, jamespetts said:

You could try first of all checking and adjusting these wheelsets with a back to back gauge. I am not entirely clear as to what you mean by the straight point blade on the through route not providing enough clearance, however, as there is more than one possible permutation of what this could mean. I have often found with these turnouts that, if I do not file the switch blades enough, the track  goes out of gauge at the point where the switch rail meets the stock rail and wheels can be forced up and out of the track, causing derailments. Carefully filing the point blades after the points have been laid can solve this.

 

On other occasions, the switch blades can be in the wrong position if not soldered to precisely the right point of the metal attachment points; these can be carefully re-soldered in situ. Use a soldering iron with a small flat tip, either a chisel or a bevel tip of 1mm in size.

 

Here’s the left-hand turnout set to ‘straight’. As the loco approaches from the toe end, the wheel that I’ve indicated will always slide into the ‘wrong’ side of the switch blade and send the loco onto the diverging route.

 

A back-to-back gauge gauge sounds good. Please excuse my ignorance, but is there an accepted ‘standard’ back-to-back, and how do I adjust the wheelsets?

[dhjgreen]

The point blades look not to be sharp enough for me.  Can I still see the head of the rail at the tip?

[jamespetts]

A back to back gauge is a machined brass item that you put between the wheels: if the backs of the wheels can fit snugly between the brass item, the back to back measurements is correct. You can get back to back gauges from multiple manufacturers; mine, I believe, were bought from Markits. I believe that DCC Concepts also produce some.

 

Do I understand that the wheel circled in red catches on the switch blade? If so, you might try carefully desoldering the switch blade from its current position and moving it slightly to the right.

 

Edit: If, conversely, the wheel circled in red does not catch on the switch blade, but seems to lift upwards when it passes the switch blade, you might instead try filing the opposite switch blade.

Edited August 2, 2021 by jamespetts

[Dungrange]

15 minutes ago, jonhinds said:

A back-to-back gauge gauge sounds good. Please excuse my ignorance, but is there an accepted ‘standard’ back-to-back, and how do I adjust the wheelsets?

 

The British Finescale website states "Only recently released models with finer wheels and flanges (models released in the last 10 years) will run on this fine code 40 track system. It is designed to accept stock with a back to back of 7.4mm."

 

https://www.britishfinescale.com/product-p/finetrax-turnout-av7.htm

 

The question is therefore whether the stock that you have issues with are older models (ie those that are more than 10 years old), in which case it may be that the flanges aren't fine enough, or that the back-to-back dimension is less than 7.4 mm, in which case you will have to force the wheels a little further apart to get the appropriate back-to-back gauge to fit.

[jamespetts]

12 minutes ago, Dungrange said:

 

The British Finescale website states "Only recently released models with finer wheels and flanges (models released in the last 10 years) will run on this fine code 40 track system. It is designed to accept stock with a back to back of 7.4mm."

 

https://www.britishfinescale.com/product-p/finetrax-turnout-av7.htm

 

The question is therefore whether the stock that you have issues with are older models (ie those that are more than 10 years old), in which case it may be that the flanges aren't fine enough, or that the back-to-back dimension is less than 7.4 mm, in which case you will have to force the wheels a little further apart to get the appropriate back-to-back gauge to fit.

 

All of the stock to which the OP referred would have modern profile wheels, so this is not an issue here.

[Izzy]

The Farish 101 DMU model used has split-axle collection through the pin-points in a muff, so under-gauged btb isn’t really possible. It certainly looks to me from the photo that the blade isn’t seating properly up against the stock rail. You do need to make sure the very tip of it is hard up against it otherwise the leading edge of the flange hits it and then does as is described, rides up and over.

 

As the point is fixed down careful use of needle files will be required to perhaps thin the blade sufficiently along with tweezers or fine snipe nosed pliers to tease the blade into sitting correctly. I always run a file along the top inside edge to round it off a bit to help with this aspect. Just a little, done gently. Having the tip bent inward very slightly is another dodge to assist when things just won’t ride through okay. Just make sure that whatever you do the blade isn’t curved to sit outward. Bending it to curve inwards towards the stock rail is all that is needed.  It’s all nip & tuck with these kind of issues.

[jonhinds]

Thanks for your help everyone!

 

Turns out the fix wasn’t too difficult. One of the point blades needed carefully resoldering to its chair plate as the blade was jamming slightly (not sure the cause but it might have been a stray particle of gunked-up solder on the side facing the stock rail), and after a further bit of careful filling it’s running perfectly now. Phew!