I just love the inside of that - with 250VAC (at 50 Hz) - and all of the exposed wiring. (As an electronics tech by trade I am speaking sardonically. Touch something in the wrong place and they'd probably have to pick you up with a hoover!)

I guess back then things were either covered up a bit more, or they figured that a policeman would have enough sense to keep his extremities away from such terminal connections (or they didn't care if some criminal was thrown into the box in temporary lock-up and he got fried from poking his fingers, literally, where they didn't belong... a second time ).

Dino.

LOL - yes, I know what you mean. Absolutely shocking!  

But more seriously, the 250 VAC high amperage side is all tight and covered up behind the service box covers (the relay box was only opened to photograph what was inside). The most a Bobby was expected to do down there was make sure the mains power lever was in the "ON" position. If something didn't work, call the Engineering Dept.

Even in this obviously less than nominal installation, all the exposed wiring you see, even the uncovered splice connections inside the bottom part of the relay unit, are on the telephone side. Not that that is exactly safe when the ring voltage comes across the lines, but that's not the usual situation and generally the on-hook static line voltage isn't deadly. The DC line voltage that powers the phone is currently 50-60 VDC in the UK (police box vintage would have been nominally 50 VDC) and relatively low amperage. The ringing voltage, on the other hand, is nominally 75 VAC in the UK, at 17-25Hz depending on the vintage of the ring generator, but the voltage could go a lot higher in some circumstances and can pack quite a wallop.

Regardless, somebody really needs to go in there and clean things up. Here's the installation in the Glasgow-type box at Avoncroft (I believe also courtesy of Mark) to show how it should be done --



The thick horizontal tubes connected to the mains at the right of the board are the heater elements, btw. Met boxes originally only had one relatively low wattage element, but when the rank-and-file complained of inadequate heat in winter they went to two higher wattage units as here. The ones at Crich seem to be missing, probably never restored to the Box prior to delivery by the Met.

I'm not sure that is mine to be honest.

Going back to the chap at the museum, he said he installed all the hardware and wiring for the telephone aspect of the box.

If this is true then maybe the electrical distribution board being intact simply meant the mains electric part?

The cream coloured box on my other pictures is the flasher relay box and the white tube with silver ends is actually a genuine fluid link filled with mercury! This was moved by a relay powered by the power from an incoming phone call which completed the circuit for the mains power to the lamp.

This type of flasher relays box is shown in situ on the Avoncroft police post and I'm pretty certain is in the same place on the Met post at Crich so they were almost certainly used on police boxes as upgrades to the original flasher shown on the gpo plans.

Oh, and yes I did get busy with the ol' sonic to get the interior pictures!

The board and relay look consistent to be original to the Box, with most of the rest looking newer and probably being added on as replacements when he did the phone installation.

The Avoncroft relay looks a lot newer. It's the tall, slim (but deep) cream coloured box at the top. Hmmm, wonder if it was Starcross' photo.

The current Crich relay is of the type they first made for the PA350 system in 1937 when they started siting the Met Posts (though looks to be a newer model made in the 50's for the functionally nearly identical PA450 systems since it is different than the one shown on the GPO plans), so yes, the same type was on most of them as well. This replaced a more bulky unit used only in Boxes in some Divisions with the earlier Dixon relay system and a very different type unit (with different relay scheme) for those Divisions equipped with the Ericsson party line system that immediately preceded the PA350 setup. Those Ericsson/GPO PA101 and PA150 systems required different type relay boxes depending on where a particular Metbox was on the three-way party line.

The history of the phone systems used by the Met for the telephones & signal lights (and thus the internal box electrics) is a tangled one, full of drama and more than a few screw ups on all sides. I think the pivotal part of the story should be called "The Ericsson Folly".  

Been a while and sorry for the taking so long to post info from the visit.

We actually learnt a lot of new stuff from this visit, mainly I think from having Matt's "fresh set of eyes" as somethings I had taken for granted would have been overlooked if not.

Hopefully the following may be of interest to some of you.

First revelation was that the corner posts are not actually square!

Whether this is on purpose or accidental during the construction is unclear but all four corner posts display the same distortion from square. Matt will have to post the exact dimensions but the corner posts are of an angle of about 88º. Not a major thing but thought I would say.

In fact the only things that were true were the roof stacks and the base which both had 90' angles on the corners as they should have.

All the walls were off true square which was presumably from the tolerances given for the slotting in of the wall sections during building however due to the un-square corner posts, working out what was square and true and what wasn't proved very difficult and even more annoying!

The interior part of the sign lintels are also not flat as I previously thought but are actually slightly sloped with the top of each being slightly shorter than the bottom. This must have been to aid release from the original molds used for their construction as the dimensions and angles are consistent despite this not being noted on the original Trench or GPO blueprints which show the interior faces to be vertical as opposed to sloped.


It was difficult to work out what attached to what when in came to the corner post interior tops because of the years of paint and cement used to attach them so they could have been part of the roof stacks or part of the sign lintels but one thing is for sure, they didn't do a great job of lining them up (or if they did then get it lined up properly originally then more worryingly the box could be sagging).



This picture is a funny angle as I was up a ladder and leaning the camera out at arms length, the box is not channeling the Tower of Pisa  

The windows are quite a mix and match now but it would seem that the windows originally had a clear middle lower section with all the other panes being pebbled/hammered (always get those mixed up) which would agree with the other boxes such as Wimbledom Common.

Some of the panes are now clear (as in the following picture) where they shouldn't be while others have been fixed with a more modern version of patterned glass which is far from convincing.



One thing I thought noteworthy is that the presumably original glass is made up of angular shapes ranging from pentagons upto octogons in a couple of instances. I originally thought these panes would be made up of more liquidy shapes such as the lower panes on the TYJ TARDIS.

Thats all for now but more to follow.

Actually, all the panes in the above window are a fairly small pattern type of "hammered" glass, not "pebbled". In fact, most of the glass panes currently in Crich's windows appear to be one of at least a couple different (but similarly sized) patterns of hammered glass. I'm sure many are original to the Box as received by the Tramway Museum, but they are likely replacements of all those broken or missing panes mentioned in the 1982 Crich memo regarding the visit to Hendon.

There may still be a few panes of the older pebbled pattern glass in some of the windows, though (upper right front and possibly on the right side?). When received from the Met, however, there were many more which were subsequently broken and replaced. Here are a couple of earlier photos of Crich which show some of them --





So, what's the difference, I hear you ask? In the most basic terms, "hammered" glass has a concave pattern while passingly similar "pebbled" glass has a convex one.

"Hammered" glass looks like one or the other end of a ball-peen hammer was hit against the semi-molten glass before it hardened, with the size of the virtual "hammer" and the pattern with which it was "struck" creating quite a wide variety of types of hammered glass, everything from wide, shallow craters (more like in some of the classic TARDIS windows) to narrower, fairly deep ones like in the glass at Crich. Of course, no real hammer is used in making modern sheets of "hammered" glass, they use a pattern roller on one surface while it is still hot, but that's the visual effect they are after. It results in irregular, almost faceted boundaries between the little craters, as Mark pointed out.

In contrast, "pebbled" glass is more like little hemispherical beads are coming up out of the glass sheet or are embedded within it, with much more of a scale-like, or cobble like appearance, and a more regular boundary between the "pebbles". The individual "pebbles" are usually much more regular in size and pattern than the much more variable "craters" that make up hammered glass. How these "pebbles" are arranged can also make quite a variety of patterns, however, from fairly random to semi-regular, almost scale-like, all the way to things that look like a bulls-eye.

I'm pretty sure all (non-Mark 5) Metboxes were originally equipped with "pebbled" glass panes (locations appropriate to the standard pattern for a given Mark). The few times we see what looks to be "hammered" glass it is always quite some time after the Box had been commissioned, and is usually only one or two panes here or there (amongst the almost universal "pebbled" panes) so are undoubtedly just expedient replacements for broken panes.

Here are some examples of "pebbled" glass from all the Marks that had patterned glass, and over a wide range of years:

The front windows of a Mark 1 (probably V11 in North Sheen), photo circa January 1931 --


The front windows of an early Mark 2 (V47 on Ashcombe Avenue, Surbiton), photo circa 1931 --


The front windows of a very late Mark 2 (J16 on St. James Street, Walthamstow), photo from the late 1950's to 1960's --


The left side windows of the Barnet By-Pass Box (V63), one of the very first of the Mark 3's - photo taken some time in the 1970's --


The front left window of a late Mark 3 (the much photographed F4 on Chiswick High Road), photo from circa 1947 --


The front left window of another late Mark 3 (M1 at the railway bridge on Waterloo Road, Lambeth), some time in the 1960's --


Now, this photo of M1 is important as it not only shows that the pebbled pattern is on the outside of the Box, like all the various types at Crich, but that it is truly convex. Look all the way at the right edge of the lower right pane and you can see the profile of the pattern standing proud against the white frame.

Finally, and most importantly for this discussion, here's a blowup of a frame from that Park Ranger film featuring the Wimbledon Common Mark 4 (V23) in 1959 --


This shows that the old pattern "pebbled" glass appears to have also been standard issue on the Crich-type Mark 4's as well.

Funny how ones mind plays tricks.

It's only when you posted the above Banzai that I remember seeing the more spherical glass, in fact the photo of the broken pain is on taken on my first visit and is looking out through the door window, the door being slightly open to get better lighting.

The box only has two pains of the original spherical glass, with the spheres being on the outside of the box. These two panes are the top left two on the door.

The window above the "Pull to Open" panel has two reasonably spherical panes either side of the clear glass while the remaining majority are the more angled glass (some of which are concave rather than convex.) and then there are a few modern ones that are just like worm shaped patterns.

With regard to the windows, I wanted to get some paint scraped away to see if there was evidence of the lighter blue paint however as the Museum have just painted the box I thought better of it. All is not lost though as there is one window, the right hand side window of the left side of the box which did have some potential.

This window is missing it's hinges and has been screwed into the actual frame to stop it falling off. Not sure when so will have to try and see if any of the early pictures of the box show anything to suggest it has been like this for a while. If you look either side of the horizontal bar you can see where the screws are.

The point is that the window cannot be opened and as such, the underneath of the ledge looks like this.


Sorry the part I'm trying to show is blurry but it was difficult to focus on and get light from the flash as I was shooting close up.

The underneath of the ledge is certainly blue and the white did look to be applied on top. I suggest that as the window can't be opened it was missed when the frames were painted white. I wouldn't be shocked to find this window was "fixed" like this while it was on the streets.

A couple of other interesting discoveries we noticed (When I say interesting, the vast majority of the world will disagree) concern the lamp base and the panels.

There is as has been mentioned previously a spare lamp base that came with the box. It appears to have been in use in the past and is where we found the paint sample of the lighter blue. This is handy as it is far easier to use this than mess about 11 ft up a ladder while trying to reach nearly 3 ft across the box.

The top of the lamp base isn't actually flat as I had previously thought but is more like a shallow pyramid with a circle cut out to accept the lens.

The two round things are what attaches a metal bracket underneath. As you can see there is a notable slant going on. Back up the ladder I climbed and confirm that the one attached to the box has the same slant.

It would also appear that the sides of the lamp base slant too. This was only discovered upon reviewing pictures so cannot be confirmed until another visit. I know it sounds odd not to notice things like this at the time we were there but I have handled the spare base on three separate occasions and it was only by chance we noticed the top slope let alone the sides. It's easy to miss something when you aren't expecting it to be there or you have always presumed something is a certain way.

The other thing we found was each of the panels on the walls has a straight line from the top to the bottom 2 inches inwards from either side.

This picture shows the lines up the best, one on each side about 2 inches inwards. If you wonder what the cable is, it was crudely installed when the electrics were upgraded and goes in through a rough hole in the wall and around the wall inside the box to the distribution panel. The original electric cable was fed up from under the floor as it would have done when the box was on the street.

Nothing amazing for most, but I found them interesting. Perhaps the lines are something to do with the casting process, or possibly due to the reinforcing bars expanding as the rust? Not sure.

Quote from: Mark on Aug 16, 2014, 03:01 pm
The other thing we found was each of the panels on the walls has a straight line from the top to the bottom 2 inches inwards from either side.
This picture shows the lines up the best, one on each side about 2 inches inwards.
Nothing amazing for most, but I found them interesting. Perhaps the lines are something to do with the casting process, or possibly due to the reinforcing bars expanding as the rust? Not sure.

My theory is that these are leftovers from the concrete forms. They would have had three parts, the two 2" outer strips and a block for the middle bit. You remove the middle bit and the two strips would be able to just fall out. Or so the theory goes anyway.

That was the main theory me and Matt figured. Would make the most sense.

Very interesting about the panel lines.

I concur they are likely mould lines. Pretty sure they couldn't be from the steel reinforcing rods, regardless, as both the GPO plans and what demolished box photos/films we've seen suggest they run along the rails and stiles or centre divider, not within the panels themselves.

Wonder if Barnet had anything similar?

I've come to the conclusion that the new paint job may be a bit of a boon in some ways. Looks like the very dark paint makes it a lot easier to spot imperfections in the concrete (both original flaws and the many patches) due to the contrast between the paint colour and the glossy highlights. Short of a complete paint strip, it seems about the next best thing - revealing quite a bit that just kind of blended in before.

Curiouser and curiouser. 

That is just good planning, regarding the lamp base.  Water is pernicious and pervasive and that slight slope is wonderful for keeping it from coming down the lamp opening.  The dimples for the lens chimney to rest on (if I'm understanding things correctly) make me happy because I did a somewhat similar construction on my new lamp base.  I just wish I'd thought of (and figured out a way to) sloping the tin. 

The raised strips on the panels are going to drive me nuts because I clearly see one in the picture.  I don't see the one on the other side as well, but if you say it is there--and that they are on all the panels, so be it.  They just don't make sense.  I was going to present an argument towards them as an artifact from the painting process but that didn't make sense.  I couldn't come up with a plausible theory for how they would be involved with the mold proc...aaah. 

Are the strips raised or lowered?  Is the main part of the panel higher or lower than the strips? 

Suppose you're casting a concrete wall with recessed panels.  If I were doing that, I'd take a sheet of plywood and fasten eight 12x14x1 wood boards to the plywood--slightly beveled on the edges to aid in mold release and in shedding water. 

If I were doing this in the days before widespread use of drywall screws and cordless drills for driving them, I'd probably nail the panels to the plywood.  I suppose you could just glue the panels on or nail them from the back side, but both these could be problematic on a mold you'll be using for limited mass production.  This leaves the problem of nail heads.  If the nails are left flush they could cause a problem with the molds.  If they are sunk with a nail punch, concrete would get into the tops of the nail holes.  So suppose you did the sort of thing you would when hanging drywall:  you "tape" your nail line. 

Of course if you are hanging drywall you add some plaster to hide the edge of the tape, but that didn't happen for building police box molds.  Voila!  Almost a century later, nerds are debating your construction techniques. 

A plausible theory, but I certainly wouldn't stake my life on it. 

Volpone, if you look at where the black cable passes over the lower part of the panel recess you should see a slightly darker line in the paint which (if you had a ruler) lines up with what looks like three white dots (light reflecting) at the top of the panel near where the cable enters the box.

At first we thought the same as you and thought brush strokes but they are on every panel and and althought they are only slightly raised, they are too raised (in my opinion) to be paint. The center portion is slightly lower than the parts after the lines.

As for the lamp base, the two bobbles don't support the lens as such, but attach to a metal bracket underneath the base unit. The lens just sits on the top in a slightly recessed circle while the bracket is probably used to attach to the lightbulb holder.

As for your theory of casting - its as good as any other! I hunted around for filled screw holes where a St John plaque may have been and found nothing so finding nail holes is nigh on impossible.

As for nerds, I hate to think what people said about me and Matt while we were there lol.

I've just checked and although not quite as prominent, there is evidence of these lines on the panels prior to this paint job.

I've had a look at older pictures I have nothing with high enough resolution or close enough up on the panels.

Oddly, the panel below the phone door has these odd but evenly spaced things

Used a pre dark paint job picture as they are easier to see. I honestly don't know if they were there before the earlier restoration, or what was there before.

They don't look to be spaced wide enough to be filled screw holes from the early style of plaque which had the telephone instructions on before the door had them. Food for thought.

A few pictures of that spare lamp base



As with all the pictures posted, they are all resized and sometimes cropped to allow posting