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Matt's Replica Crich-Style Police Box

Started by matt sanders, Aug 03, 2014, 10:41 pm

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matt sanders

Quote from: superrichi1a on Aug 12, 2014, 12:29 pm
This is one of those build threads where I'm learning a lot without meaning to! You, sir, have succeeded where countless fully trained teachers failed, congratulations ;)
Greatly enjoying this build, I always thought I would like to learn how to do Fibreglass properly and do a portable TARDIS some day, this is certainly resurrecting that desire...


Cool!  If you do try and make something in fibreglass, I strongly recommend playing with some small amounts first, on something that doesn't matter - cos there are a LOT of things that can go wrong.

I've been using fibreglass for nearly thirty years, but when I tried to cast the first panel for the base, I was so distracted by adding the black pigment to the resin, that I forgot to add any catalyst!   :o

It was only after I'd painted it on, and waited in vain for it to set, that I realised what had happened, so had to wipe and scrape a load of uncatalysed resin (and knackered matting) off the mould...   :-[

matt sanders

Quote from: Sorvan on Aug 12, 2014, 05:11 pm
So you're effectively gluing the completed piece of textured fibreglass skin onto your wooden frame with a layer of gelcoat?

I'm just fascinated by this.

Colin



Yes, that's about it.  The fibreglass is only 1-2mm thick, so is just to give texture and weatherproofing to the plywood.  I'm not doing the whole box like this, just the base, as I felt it needed a plywood frame to be bomb-proof, and to be walked on.

The rest of the components will not have plywood in the finished items.  For instance, the walls will be two skins of fibreglass, filled with expanding rigid foam, to give a casting that is strong but light-weight, like a surfboard.  That's the theory, anyway!  God knows if it will actually work!

So, as I'm making my box authentic inside as well as outside, I'm actually casting the components in almost exactly the same way as the guys who made the concrete version 75 years ago - just using more modern materials...

Mark

Just re-read you post Sorvan, sorry - I misread it the first time!

Back of the class for me ;/

timewomble

I've never used expanding foam, but a friend used some to fill some external trim on his Golf GTI down in the South of France. A few days later, with his car left out in the sun, the foam came oozing out to form strange burnt orange-coloured piles, so hopefully the stuff you're using will stand up to hot summer weather better than that!

matt sanders

Christ - I hope so!

I made a small test panel, and have left it out in the sun, but it's been mainly raining the last couple of weeks.  That foam can be unpredictable if not measured and mixed correctly, so I'm trying to be extra careful...

Sorvan

Quote from: timewomble on Aug 12, 2014, 09:10 pmA few days later, with his car left out in the sun, the foam came oozing out to form strange burnt orange-coloured piles


This makes me wonder what kind of expanding foam was used.

I'll admit that it's not something I know a whole lot about, but I do know that you can buy aerosol cans of expanding foam at the hardware store (for sealing gaps around window frames etc.) and that you can also buy a two part product which you can mix to make expanding foam.  I'm just wondering if the stuff in the can requires air to solidify - so if you fill a non-porous area, the stuff in the middle might not harden (or not quickly at least).  I know that when I've used the cans around my house, if I try to get rid of the excess too soon that more stuff just comes out of the cracks.  Perhaps the two part product doesn't have this problem?

Colin

Volpone

I suspect it does. My latest can proudly claims to be "reusable."  And the way you reuse it, there's the nozzle that takes the plastic straw.  Then, on top of the sprayer assembly is a plastic plug.  When you are done you bend the plastic straw up and around and plug the end onto the plug.  It seems to work. 
"My dear Litefoot, I've got a lantern and a pair of waders, and possibly the most fearsome piece of hand artillery in all England. What could possibly go wrong?"
-The Doctor.

matt sanders

Well, I promised the next episode would be Column-boxes, but yesterday I had a day off from building, to go with Mark to a nice little Tramway Museum in Derbyshire...

So, today's episode is:  "Crich Cutaway"...


Now, obviously, we took lots more measurements, but I also had a bucket of silicone rubber, so this happened:


IMG_1338.jpgIMG_1339.JPG

These are the last four panes of Pebbled Glass remaining on the Crich box, on the Door and adjacent Wall.  The other (opening) windows on the other walls instead have Hammered Glass (concave dimples instead of convex).  This may be original, or (we suspect) may have been added during its time at Hendon training centre. 

The photos above show a thin layer of fast-setting silicone painted on.  This was then backed up with a thicker layer that had thixotropic added, to stop it dripping off.  Then, some foam-board pieces, to give the mould a flat rear surface, to help with casting...

IMG_1341.jpgIMG_1342.JPG

matt sanders

Now - the thing is - did you realise these windows have two different types of Pebbled Glass...?

Here are the silicone moulds, lit from above, so the raised domes that were in the glass here show up as concave recesses...

IMG_1358.JPG

The mould on the RIGHT is from the glass on the DOOR - it has very regular spherical lumps, which almost retain circular shapes, with assorted little flat areas between.  It's as if some clay were rolled out flat, and a ball-bearing was repeatedly pushed into it, to make a mould.

The mould on the LEFT is from the adjacent WALL - the shapes are less circular, and more like polygons.  And instead of irregular flat areas between them, they have more even valleys.

So - the big question is - did this box originally only have ONE type of glass, and if so, which is the earliest?  If the door's glass doesn't match the wall's, is that another indication that perhaps this door was a later replacement...?

matt sanders

By the way, before we went to Crich, I used some foam board to make this:

IMG_1331.jpgIMG_1332.JPG

Then, when we got there, this happened too:

IMG_1334.jpgIMG_1336.jpgIMG_1340.jpgIMG_1343.jpgIMG_1345.JPG

matt sanders

So, now I've got a silicone mould...

IMG_1355.JPG

... it would be rude not to paint in some polyester gelcoat...

IMG_1356.JPG

... and some resin with glass fibres...

IMG_1357.JPG

... and when it's set, you get one of these...

IMG_1360.JPGIMG_1361.JPG

Now I just need three more, then I can join them together, and make a nice big mould of the whole thing...   ;D

Mark

I have to add at this point that on three separate occasions I had to point out to various NTM staff that Matt wasn't damaging the box and was simply making copies with the potential to have spares should the real ones on their box break. One of the chaps thought Matt was painting the glass white and wondered if that was how they were supposed to be.

I obviously saw these casts in the flesh so to speak and they are amazing, and the resulting lens looks even better.

When I get a chance I shall post some pictures on the Crich thread about the windows, and I shall also post a picture on this one of the amazing fibreglass test piece Matt brought along.

matt sanders

Yes, it was very helpful, having Mark to fend off the staff - whilst also holding the ladder!  Luckily they generally seemed to assume that someone else had given us permission  ;)

A few things about the Lamp Housing:

-  Top of the Lamp-Base:  As we were about to leave, we suddenly noticed that the top surface of the square base isn't actually flat, but slants down towards each edge, like a shallow pyramid.
-  Rods: It was only when I measured my mould, that I realised the Rods aren't actually vertical, but actually lean outwards, so they are a quarter inch further apart at the top, than the bottom.
-  Sides of Lamp Base:  I only noticed this just now, when looking at the photos that I've just posted - the sides of the Lamp Base look like they aren't actually vertical, but slant inwards - perhaps to aid release of the metal casting from its mould...
-  Top Disk:  And now, looking again at those pics, I also wonder of the Top Disk also has slanting sides (wider at top than bottom), also to aid mould-release...

Damn - I wish we'd had more time to get measurements of all this stuff...


Mark

Aug 15, 2014, 12:04 am #43 Last Edit: Aug 15, 2014, 12:05 am by Mark
I was uploading the pictures to my laptop and was thinking the same about the slight slant on the lamp base.

At first I thought it could be lens distortion but every picture that shows the lamp base on the box shows a slight slant no matter how close or how far away the camera was.

Does this mean another visit is required  ::)

As promised below is a picture showing the fibreglass test sample Matt had made and brought with him.

DSCF4087 SIZED.jpg

You can make out the police box's left corner post to the upper left of the picture (flask related coffee is compulsory on TARDIS travels, bottom right) and Matt's test piece is at the bottom.

The texturing on the sample board is almost 100% perfect as a match to the actual top part of the police box base, and the colour was pretty close to the version the NTM used to repaint her.

More impressive is how strong and light this sample was. It has no flex to it.

This build is going to be amazing. The amount of research Matt has put in (14 hours that I saw in person on site over 2 days) plus even more on the planning for the build that he must have done. Just after and handling and seeing the fibreglass test piece I want to put my name down for the 2nd box you pull from the molds (presuming there are more?  ;D).

Sorvan

Quote from: matt sanders on Aug 14, 2014, 11:30 pm
Luckily they generally seemed to assume that someone else had given us permission


I just find this hilarious.  It's the assumption that no one would have the gall to do this without permission. 

Reminds me of the story of a couple of guys who stole a canoe from a sporting goods store.  Everyone assumed that they had purchased it, and when staff looked at the security camera footage afterwards, it clearly showed them walking out of the door - but they had a canoe over their heads so they couldn't be identified.

Colin