Flying Scotsman (bogie?) changing points on its own

[Chas1969]

Hi, aware that there are posts on points issues but haven’t seen this issue (apols if missed): today when running the FS - only train we have so can’t test with another - it keeps nudging points as it goes through. Audible noise, partial derailment and when you look at the points it’s gone through the switch has moved along with the rails, not fully but enough to cause an issue.

Any ideas?

[RDS]

Hi,

Does this happen:

a) in both directions

b) on any other points

c) if you try gently pushing a wagon or coach over the point

 

Or, is anything on the Loco physically catching either on the lever at the side, or underneath catching the point in some way.

[Chrissaf]

More than likely the 'Back to Back' [b2B] measurement between the back faces of opposing wheels on the same axle are either two close together or too far apart. The optimum B2B is 14.5mm measured by either a purpose manufactured B2B gauge or measured manually with a digital vernier. A ruler is just not accurate enough as a 0.1mm error can make all the difference. Wheel B2B can usually be adjusted as the wheels are typically push-on friction fixed on the axle.

.

Example Digital Vernier                                    Example B2B gauge

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.

Also, check the spring pressure on the point. The spring might be missing, dislodged, weak. When operating the point. The moving rails should not be sloppy and border on a snapping action similar to a toggle switch. If the spring is not correctly performing its function, then the moving rail can easily be moved by the passing loco.

.

[atom3624]

All 'usual' details already mentioned above.

 

Which model of FS is it - fairly recent (within last 10-15 years) or older from the 70's?

 

Al.

[morairamike]

Is this caused by the front of the rear bogie.

I don't have a flying Scotsman. But I'd the rear bogie fixed or does it swivel. If fixed then it should have flange less wheels like the A4s have. If it swivels then ignore this input.

[Chas1969]

Thanks all and sorry for slow reply, work took me away. 

Its the new FS, set bought Dec 2018.

Just seems to be one set of points,new set that came with a track expansion set.

When next back near the track I will check the spring: are such things changeable or is a replacement t track section best?

I’ll admit I don’t really understand the B2B measurement and how I would rectify that!

[Chrissaf]

I’ll admit I don’t really understand the B2B measurement and how I would rectify that!

.

Most wheels are just push on friction fit on the axles, so the distance between the 'back sides' [b2B] of the wheels has an element of adjustability. Push the wheels closer together to reduce the B2B if too far apart, or pull them apart if too close together.........simples.

[96RAF]

Just to clarify B2B adjustment is easy on push fit wagon, coach and the loco smaller (bogie/pony truck) wheels but may not be possible on steam loco main driver wheels without a higher skill set as it can involve total dismantling and shim washers, etc.

[Lb101]

I have this loco from around the same time, assuming it’s the railroad one And noiticed it did sometimes do this on two particular facing points.  i tightened the front bogie assembly (four small guide wheels at the front, sorry if that is teaching you to suck eggs) which was very loose and wobbly compared to my railroad Mallard. This improved things as well as the derailments I was seeing. The screw is easily visible underneath.  Just an idea if what’s been said doesn’t resolve it. I also make sure I push the point in tightly with the slider (I have the latest Hornby track).

[Lb101]

Just as a footnote to my last message, does your front bogie assemby have a spring. I seem to remember mine didn’t. I added one from a spares and repairs Railroad Mallard (which Had suffered a major crash down the loft hatch banging off every step as it went 🫨). 

[atom3624]

I thought Mallards could fly !!

 

Sorry!

 

Al.

[Lb101]

Doh, That’s so bad it’s good  😆

[Flightsimer]

I'm having the same problem with my FS, 2018 model. When runs into the point to switch tracks the front boggie derails.

In another point, as it pulls out of the station, again the switch tracks, the front boggie rides over the point, derailing and also changing the point direction.

This is a new setup, just got the track sorted and testing it. The points are 1st radius, was wondering if I changed then for 2nd radius express points if that would fix the proble. The engine goes over the other points with out issue, but they're not set mother than to go straight on.

[Chrissaf]

Hornby standard points are 2nd Radius not 1st, and Express points are not 2nd Radius, they are a shallower curve than even 4th Radius and have no equivalent Hornby curve radius to compare with..... see curve comparisons below for the evidence.

 

• The radius of the curved part of the R8077 / 78 Express points is 852mm and the arc is 11.25°
• The radius of the R8261 [arc 22.5°] / R8262 [arc 45°] 4th radius curves are 572mm
• The radius of the standard Hornby points R8072 / R8073 [arc 22.5°] are 438mm
• The radius of the Hornby Curved points R8074 / R8075 are 438mm on both curves.

 

You should be checking the 'Back to Back' measurements on your loco wheel-sets. Incorrect 'Back to Backs' can cause your observed symptoms. Derailing due to 'Back to Back' errors can be more prevalent when a curve directly transitions into a point. The issue is less prevalent when there is a straight approach into a point.

 

[ColinB]

I used to have this issue with my old Hornby ringfield motored locos, I found it is was due to the back to back measurement on the wheels and the thickness of the wheels, but your's is a modern one so I doubt it is either of these. Back to back may be the issue, that definitely on my locos "clumped" the points often changing them, you can normally hear it. As someone said sometimes it is the front bogie floating about, in which case as someone also said adding a small spring seems to cure it. I noticed on Hornby's latest Princess Elizabeth class that was one of the differences between the "retooled" one and the previous version.