Point mechanism

[redtoon1892]

I was on Newcastle Central last Friday and I noticed a point mechanism different from the usual lever type around the Central, this one seem to be hydraulic or pneumatic. It looks new and I have not noticed it before. Maybe they are quite common ?

[hq1hitchin]

That's clamplocks, redtoon, a BR standard and they were a 1980s design. Oil filled mechanism, if I recall right, as during a failure you certainly had to pump them by inserting a wee handle in a suitable orifice in the box to the top of your picture. Unlocked by a 221 or 222 key. If seriously damaged, you could bar them across but didn't often had to do that.

[Bryan]

Very prone to tamper attack as well.
A lot easier to use though than the winding handles. No scuffed knuckles.

New installations are using new geared drive systems with a rotating shaft in the 4ft powering a number of point drives to the blades.

[Signalboxes.com]

The points using the geared drive are called HPSS (High Performance Switch System), these are very expensive to install (around £250k i'm told), and also very expensive to repair (the ECU 'the electronic brain') costs £12k to replace!
Currently Network Rail prefer the 'IBCL' In-bearer clamplock, this is similar to the picture above but the hydraulic equipment to move the blades is in the first sleeper, so its no longer tamper bait. Also they use the Hy-drive equipment, these are hydraulic drives that power over the blades at the mid and rear positions powered from an oversized hydraulic pump that also powers the front hydraulic rams, thus doing away with stretchers.

Anymore advice/info required, just ask (i'm S&T!).

PS: please visit my site http://www.signalboxes.com for photo's of signalboxes in the Notts area.

Frankie.

[R. pike]

Clamp locks are awful things compared to an HW point machine. With clamp locks costing around £7500 and an HW circa £10000 i know where my money would be going.. CL renew at 7 years and throw it away. HW renew at 25 years and send for remanufacture...

[Mickey]

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[StevieG]

Regarding manual operation of clamplocks on site, if the signalman suddenly had any set of points fail in either position (points would move but would not detect as set and locked in one or both positions), it was quite usual to try overcoming the problem by swinging them back and forth a few times hoping to clear some possible temporary obstruction in order to get them to detect in at least one, hopefully both, positions.
With Clamplocks though, this problem could occasionally have been caused by earlier unexpected damage or other problem with the pipes, allowing leakage of the hydraulic fluid, in which case, all that moving the points might unwittingly achieve was to cause more fluid to leak out and lower the hydraulic pressure, until the points probably had no chance of locking and detecting at all, in either position. Unfortunately manual operation on site by emergency operating staff using the pump handle in the control unit, IIRC, depended on the hydraulic system being in working order, so someone attending in these circumstances, hoping to help by hand-pumping the points, might find that their efforts brought no improvement and so they couldn't directly assist at all.

Hy-drives: I've been told that where they're used on longer point switches (e.g. those for high speed divergences), for a second or three while the points are being moved, each drive can operate slightly unsynchronised, so if the points are viewed along the track from either direction while they are moving, the switches can be seen to briefly appear distorted in like a double bend alignment until all the drives set and lock their part of the switch. It would look weird, but the flexibility of the switches allow it to happen without damage, and all is well as long as every drive of the switch ends up correctly set, locked and detected.

Regarding checking a route set up by hand, if it's a long or complicated one, like a string of three or more crossovers or through double slips or switch-diamonds, one tip I got from my time on 'the G.E.' (perhaps even more useful at night or in fog/snow) was not only to walk through the route to check it rather than stand back and look, but also to have or find a piece of wood about 3-or-so feet long (a Brake Stick was ideal if you could still lay your hands on one), and drag the stick along the inside edge of one of the rails of your route while walking it. Then, if you'd got something wrong, your stick would start going in a direction you didn't expect or want.