"It consumes my mind"--concrete police box replica...

[Volpone]

Hi guys.  Just a little spam, killing some time with my support group of fellow madmen. 

Having built a TARDIS, I keep mulling better ways to build one--lightweight and portable, solid and stolid, using concretelike Hardiboard products and yes, making one out of concrete.  Truth be told, I think it would be fairly easy.  And it would be fairly permanent and indestructible.  The problem is, from the math worked out in my brain while walking the dog and the pricing on concrete that I've found online, it really wouldn't be any cheaper than a wood TARDIS (and as it stands, I can't justify building another wood TARDIS for what they cost).  But I do have to share my construction brainstorming in case someone has the time and money: 

The base is fairly easy, of course.  People have been pouring square concrete slabs since Roman times.  But I'll come back to that. 

Corner posts aren't terrible either.  Make yourself a big "L" shaped chunk of lumber, close the ends off and stick some inside corner mouldings in it, probably have a smaller "L" to go inside.  Or maybe a "V" is more accurate, because your form is going to be braced up like a "V".  Fill the bugger up with concrete, push your inside form down into it, and let it set up.  Maybe put a hinge on its length to make it easier to get the cast form out of it.  Do 4 times.  The thing I'm missing is the best way to put reinforcing steel in this, but more on that later. 

Actually, the sides are even easier.  Sheet of plywood with a 2x4 frame around it.  Another sheet of plywood goes inside with the center channel cut out of it.  On top of that go 6 beveled panels and 2 2x4 frames for the windows.  I haven't decided if I'd do the "steps" between the wall and the roof on this part or cast them with the roof.  Fill with concrete and sink a steel wire mesh into it for strength.  Repeat 3 times. 

Once you've got 3 walls, you essentially cut your mold in half.  You also pull the top beveled panel and stick the window "frame" from the other side there.  There's your front with the opening for the phone. 

The actual door is wood, so I won't spend time on that here, but depending on how your lumber for the molds has held up, you could repurpose that for your door (well, the plywood, you'd need the trim). 

The roof I'd probably cast in place, one step at a time--essentially like a Jell-O mold or something.  a pair of concentric 2x4 frames with a bottom to keep the concrete from running out.  Then a smaller pair of concentric frames.  The actual sloped roof part, I might wuss out on and just build it from plywood and then spread concrete on it like frosting a cake.  And I still haven't figured out how to do the top signs. 

All this has been rolling around in my head for some time, but tonight was the "A-HAH!" moment.  See, the problem is tying all the pieces together.  I was thinking, sink reinforcing rods into the slab to tie the corner posts into; extend the steel mesh outside the walls so you could fasten the sides together, maybe even pour inner corners to tie everything together. 

Then it hit me:  Pour the slab last.  Stand your corner posts in place and get them shimmed into place.  Lean your walls into position too.  But make them all 6" taller than they need to be.  Then you pour your "base" with everything else in place, freezing it all into one solid piece.  (Obviously there would be gaps between the corners and the sides, but with a solid concrete base fixing them in place and the roof cast in place, fixing the top edge, it would be very stable even without mortaring the seams.  In fact it might actually be better because the seams would allow for ventilation. 

Unfortunately, unless I somehow have a million dollars fall in my lap (or someone hires me to make it), this isn't ever happening. 

[Mark]

Making a concrete box has often found it's way into my head and I knoe Domvar has a notion to do it.

The problem in my head is that I would have to first spend cash and time building the forming boxes to cast the parts from.

I also fear for the thing collapsing, wood would hurt but concrete....

As for constructing the thing, if you study the Trench plans you can see that each part of the box has either a channel or part to fit into a channel. Oncee a bit of mortar has been slapped into the channel the next piece would slot in and be quite solid.

I still have no where to put a fullsize box of any description so will have to leave it to you or Dom to build a concrete one.

[hb88banzai]

I must admit to thoughts of such as well.

The use of plastic beads in place of sand as the aggregate can save a lot of weight.

Use of threaded steel rods or pipes extending beyond the component edges instead of the usual rebar rods and mesh as reinforcement could allow for ease of assembly and disassembly when required.

Of course 1/3 or 1/4 scale replicas would be a lot easier to find room for, and a lot easier to build (allowing one to perfect the technique in the process). A bit harder to get inside, of course.

I think the real reason to build one, though, would be to set it up as a fully weatherproof "Doctor Cave" in the back yard.  

[domvar]

I do plan to make this a reality as soon as we have moved house, due to the housing market in the uk doing the things it has over the past few years this plan has been on hold for 3.5 years.  However we are finally putting ours up for sale in the next 4 weeks so fingers crossed next summer may be the year.  Once I'm in a position to start I plan to get in touch with Wade as he has cast replacment components for his Glasgow boxes, I am also only a stones throw from the criche box so internal and external impressions in silly putty may be a possibility for fiddly bits like the steped section at the top of the panels. I hope to do as close to the real thing as possible.  I even worked out a plan for the windows and phone door involving reclaimed crittal windows.

[Tempus Fugit]

If I do get to build another box after this wooden one, then I think concrete will be the only way to go. I'm toying with fibreglass too but it strikes me that that is only the most use for having a movable prop.

[ironageman]

Perhaps this is widely known, but I've recently discovered the trick for casting walls - cast them vertically, using temporary bolts between the front and back moulds to keep them from bowing. I mention this because all of these pieces of police box will be very heavy: and so I should think that the more that can be cast in situ the easier it will be.

[kiwidoc]

Interesting - casting vertically had never occurred to me.  You say 'discovered' - have you been experimenting or doing some research into how it was done in the past?

[tony farrell]

The Empire (Wembley) Stadium's towers were cast using this methodology.

T

[galacticprobe]

Very interesting, and an excellent idea. (Sure beats trying to stand up one of those walls, which would weigh probably as much as a completed wooden box - say several hundred pounds?) And those bolt holes would be easy enough to fill in with concrete once the forms (moulds) were removed. Then once the paint goes on? You'd never know those holes were even there.

Brilliant suggestion, ironageman! (I'm one that wasn't aware of this, so if it is widely known, I wasn't part of that "widely": until now.)

Dino.

[ironageman]

I was wandering around some second-world-war buildings and trying to puzzle out their construction when someone told me the trick. It's sort of obvious, but only when you know... Anyhow, it's somehow satisfying that it's an authentic police-box-era method.

I can't imagine that the corner posts could be sensibly cast upright but the rest of the box could be cast in situ. I like the volpone idea of having longer posts that will presumably rest on a reinforced slab with the box base being cast around them. I should mention too that the whole thing could do with some decent foundations!

[fivefingeredstyre]

The Empire (Wembley) Stadium's towers were cast using this methodology.

T

As was the main structure of the new care home development we are building as work... Its a bit smaller than the Stadium towers mind...