Birdcage question

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muggins
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Birdcage question

Postby muggins » Sat Nov 21, 2020 5:22 pm

I've only just noticed that the axles of my birdcage coaches run in metal pressings which have tabs that disappear up into the bogies. What's that in aid of then?

mahoganydog
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Re: Birdcage question

Postby mahoganydog » Sat Nov 21, 2020 5:36 pm

Probably for installing lighting if the user so desires.
In a world of fences and doors who needs windows and gates?

muggins
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Re: Birdcage question

Postby muggins » Sat Nov 21, 2020 5:51 pm

Well that's all I could think of, but I'm rather hoping somebody actually knows. I don't recall seeing anything about this in the bumph.

Mike Parkes
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Re: Birdcage question

Postby Mike Parkes » Sat Nov 21, 2020 6:27 pm

https://grahammuz.com/2017/09/08/the-fi ... ts-arrive/

"No internal lighting is fitted but each bogie includes wiper pickups so this might be a potential option in the future."

muggins
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Re: Birdcage question

Postby muggins » Sat Nov 21, 2020 6:37 pm

OK, so it really is just a sort of halfway house to coach lighting! Seems weird to me that they'd go to the expense of the press tooling and fixtures to make and fit that gubbins to the bogies and then not actually take it any further, but hey, what would I know.

Bigmet
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Re: Birdcage question

Postby Bigmet » Sat Nov 21, 2020 7:57 pm

First saw this on the unpowered bogies of their BR MU's , With split axle wheelsets the pick up off the pinpoints is achieved with no incremental friction, since the bearings are necessary, and the actual friction is very small. Also found on the mk1 Pullmans and the Thompson gangwayed stock; and quite probanly on the Stanier Porthoie stock, though I have not purchased any. (These various vehicles will typically roll away from rest on an estimated 1 in 250.)

It's a good system, and one I wish Bachmann would think to use on outside bearings tender wheelsets, if only to show Hornby the error of their high friction method.

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stuartp
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Re: Birdcage question

Postby stuartp » Sat Nov 21, 2020 8:47 pm

The Portholes have them as well so they appear to be standard. Future-proofing the tooling presumably.

In theory they should improve running as the pin points are effectively running in a metal bearing rather than plastic.
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RFS
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Re: Birdcage question

Postby RFS » Sat Nov 21, 2020 9:45 pm

If you are using automation, and want to fit resistors for track circuiting, then doing that on these coaches is a doddle.
Robert Smith

Bigmet
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Re: Birdcage question

Postby Bigmet » Sun Nov 22, 2020 10:38 am

stuartp wrote:The Portholes have them as well so they appear to be standard...

Thanks, that's useful to know.

Further to which, swapping the bogies about within the Bachmann range is very simple, and is provoking thoughts of working tail lamps on my passenger and bogie van trains, and there are inevitably some LMS bogie vehicles on the layout...

stuartp wrote:...In theory they should improve running as the pin points are effectively running in a metal bearing rather than plastic.

They very nearly match the most free running vehicle on my layout, which runs on a pair of Trix Commonwealth design bogies made in a polymer formulation which approaches PTFE for 'no friction'. This item has long been used to detect gradients on layouts which are nominally level.

It's all good news on coaches where the close coupling mechanism is used, carefully adjusted so the coach gangways are in contact on straight track. 'Loose coupled' using tension locks or other couplers with significant slack, the vehicles can be seen 'bumping about' at low speed, not so good. (I would hang a draggy vehicle on the rear to keep the train stable.)

If you have enough of them and a gradient they can also do a very railway thing. A light loco can get a long train going on the level, but will quickly slip to a stand as it starts going up the gradient: and running onto a downward gradient may well be unable to stop the train. Very noticeable on 0-4-4T designs which have stability problems in model form which can 'unload' the driven wheels (more in some orientations than others).


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