Point blade movement

Discuss the prototype and how to model it.
Hardwicke
Posts: 537
Joined: Sun Sep 14, 2008 10:25 pm

Point blade movement

Postby Hardwicke » Tue Sep 13, 2016 10:18 am

Does anyone else have problems with point blades not switching fully? I'm using C&L Exacto points and underboard unit, Tortoise motors and Ambis bars. I've adjusted the throw of the bar on the motor but something is still not working. A finger prod and it pushes up against the rail. Suggestions?

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Tim V
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Joined: Tue Jul 29, 2008 4:40 pm

Re: Point blade movement

Postby Tim V » Tue Sep 13, 2016 3:06 pm

Disconnect all connections to the blades, including any soldered to them. Now do the two blades sit snuggly against their stock rail?
Tim V

Armchair Modeller
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Joined: Thu Jan 06, 2011 7:34 pm

Re: Point blade movement

Postby Armchair Modeller » Tue Sep 13, 2016 3:52 pm

Thicker, less springy wire on the Tortoise?

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David Thorpe
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Joined: Tue Oct 21, 2008 11:13 pm

Re: Point blade movement

Postby David Thorpe » Tue Sep 13, 2016 3:53 pm

This may sound unduly simple, but when I built my turnouts using ply sleepers and Exactoscale chairs, I found that the blades sometimes rubbed on the surface of the Exactoscale slide chairs and didn't close (or open) properly. I cured that by filing a little off the offending slide chair(s).

DT

Hardwicke
Posts: 537
Joined: Sun Sep 14, 2008 10:25 pm

Re: Point blade movement

Postby Hardwicke » Wed Sep 14, 2016 11:51 am

Thanks everyone. Yes they do fit snugly. I sanded the baseboard underneath and fitted the wire on the opposite side of the retaining nut. This gives a bit more movement so it is now within a thou or so of fitting. When the motor was disconnected it moved very freely and fully.

Terry Bendall
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Joined: Sun Jul 27, 2008 7:46 am

Re: Point blade movement

Postby Terry Bendall » Thu Sep 15, 2016 8:16 am

I gave up on using the turnout operating units under the baseboard a long time ago and now use Ambis stretcher bars in functional mode with a crank operated by a rod through the baseboard. Having inherited Longcarse West which had the Exactosale system, they have all just been changed and are far more reliable. No more droppers to fall off half way through and exhibition. :( Longcarse will be at Scaleforum so anyone who want to see what has been done can request a peep under the baseboard and one day I will write it up for the News. However if you want to talk to me about the method come and find me since I may be a bit busy with one or two other things. :)

The operating wire on the Tortoise motor has been replaced with a flat aluminium strip 10mm x 2mm so that does not flex. When I did use the springy wire on the Tortoise I usually fitted a piece of brass tube over it to reduce the flexing.

Terry Bendall

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grovenor-2685
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Re: Point blade movement

Postby grovenor-2685 » Thu Sep 15, 2016 8:41 am

If they work by finger, presumably applying the finger to the under board TOU, but not by the Tortoise then the problem is with the Tortoise or linkage not the points.
Are you fitting the Tortoise as per the Exacto design?
Its quite likely the Tortoise is pushing to hard on the TOU and causing the droppers to bend, in this case adjust the tortoise to reduce the throw, and/or reduce the motor voltage with a series resistor.
If the point blades are actually stopping short then either the tortoise throw is not enough or there is binding in the linkage. A tight fit of the tortoise wire in the TOU throw bar could have this effect.
Regards

allanferguson
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Joined: Sun Jul 20, 2008 6:27 pm

Re: Point blade movement

Postby allanferguson » Thu Sep 15, 2016 12:42 pm

I have on occasions found that the hole in the baseboard does not match the operating rod, and friction or blockage there can cause a problem. Making the operating rod from the Tortoise stiffer and adjusting the throw to match the switches may also help.

Allan F

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Russ Elliott
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Re: Point blade movement

Postby Russ Elliott » Fri Sep 16, 2016 12:08 pm

Assuming no mechanical impediments (baseboard apertures, slidechair tops*), I tend to agree with Keith - probably a bit too much TOU movement resulting in an excessive inclination of the dropper at the blade attachment area.

blade-inclination.png
blade-inclination.png (2.93 KiB) Viewed 1632 times


If all else fails, this might help:

blade-inclination2.png
blade-inclination2.png (4.04 KiB) Viewed 1620 times


* In my (heretical) opinion, slidechairs should be thinned so that their tops do not make contact with the underside of the blade. (Our 4mm rail does not need vertical support like the prototype does.)

Hardwicke
Posts: 537
Joined: Sun Sep 14, 2008 10:25 pm

Re: Point blade movement

Postby Hardwicke » Sun Sep 18, 2016 9:29 pm

I checked the droppers were fitting the tubes and found one was miss-aligned. I re-fitted it and bent the blade as per Russ' suggestion and it works fine now. I also drilled out a bit more of the baseboard. Sadly the Ambis tiebar broke off.....
The last point has also had some adjustment and I think as soon as I refit the chairs to gauge, it will work fine.


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