Point blades opening amount

Discuss the prototype and how to model it.
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Re: Point blades opening amount

Postby Noel » Wed Nov 16, 2016 11:14 pm

Have you eliminated possible problems with the stock? Your original comment
CaptainTony wrote:a wagon occassionally derails here when set to the curve
is a bit ambiguous. I assume that it is not a specific vehicle which has problems, so is there any pattern to which vehicles derail and under what conditions?

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Re: Point blades opening amount

Postby grovenor-2685 » Wed Nov 16, 2016 11:35 pm

I'll see if I can dig mine out and measure them

The relevant hairclip gauge in my set measures 1.6 mm, a little bit over as you said but would be easy to correct.

Julian Roberts
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Re: Point blades opening amount

Postby Julian Roberts » Thu Nov 17, 2016 7:05 am

Hi Tony I am with Russ on this. I'm still a beginner in trackwork. Edit. Sorry. I see you are an old hand. All the following is inappropriate really. But having posted it earlier I suuppose I may as well leave it.

My first points in P4 are three B8 turnouts for our group project and the first one is down on the boards and gave no problems on its first exhibition outing last weekend even though the normal move that they are for, is a train of mineral wagons propelled through. It has a 1.3mm open blade gap. You can see I didn't make things easier for myself by modelling some lock stretcher bars, not quite accurately as Keith showed me on the separate topic a few weeks ago.

When I was finally fettling it before installation I found I had one wagon that gave occasional trouble on the diverging route so I fettled it still further (on the Murphy's Law principle, what can go wrong will go wrong). The fettling was first of all with a riffling curved knife shape file aiming to continue the 60 degree angle that Martin Wynne suggests for filing the blades which I thought I'd already done (and which I find a lot less easy to do adequately than he suggests it is!). Then with about 600 grit wet and dry.

2016-11-01 12.40.56.jpg

As I go into Glasgow Central station every time I take the train to work I have plenty of opportunity to look at points. At the very tips the top level is below rail height and they gradually taper upwards, so, it seems to me, gradually knife their way into a flange if it is against the rail. Very crudely I am aiming to do the same. So Russ's 0.5mm blade tip is zero in this case. The gradient or taper up to rail level is the critical bit not to have any roughness to catch the flange. Where it meets the rail height it's about 0.2mm thick. As my cut throat razor knife has that thickness blade I reckon that's a minimum! Obviously these tips are now very delicate even with the rail foot intact so the lock stretcher protects them. I learnt most of this from the discussion that Russ refers to on the Forum. I think it was this

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