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Stiffening a hinge

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Stiffening a hinge

Unread postAuthor: Ragnarok » Tue Oct 04, 2011 8:22 am

Howdy gents.

As you may have noticed, I've not been spending <s>much</s> any time around here at the moment. Unfortunately, it turns out that Charlie - in case you've forgotten, that's this chap:

Image

... is terrified of loud bangs. So, basically, we have the world's most useless gundog, and I can't really do much spudding any more.

So I'm largely working on other things these days.

Right now, one of those things has thrown up a issue. I'm a little behind on the project, so instead of just throwing time at it, I'm hoping one of you guys has got the brainwave I need.

Rather than trying to explain it in text and pictures, here's a video:

[youtube]http://www.youtube.com/watch?v=a7CBSgx4Zeg[/youtube]

Or... TL;DW: I'm building a hinge out of copper pipe and I need to increase the stiffness of it. I can't just jam dowel into it to force it together, as the dowel I can get doesn't come in the right sizes (either too small to jam it, or large enough that it'll take ages to sand down).

Needless to say, I don't want to spend a heap of money on it, so only relatively cheap suggestions please. And relatively simple, as I've got to repeat it for 13 other joints.
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Unread postAuthor: Labtecpower » Tue Oct 04, 2011 8:37 am

I'm in school now, so I can't turn up the volume to hear what you say :roll:

You'll probably hear some brain farts when i'm at home...
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Unread postAuthor: Ragnarok » Tue Oct 04, 2011 9:08 am

Well, short story long, I'm making a hinge out of copper pipe.

There are two outer pieces that form one half of the hinge, and an inner piece that has had part of its circumference cut out so it can fit inside the other pieces as the other half of the hinge.

Unfortunately, this has proven less grippy than I'd like (it's worked well in the joints made from plastic pipe, but the metal/metal surfaces and less springy copper haven't worked well), and it won't hold its position when I put weight on it.

I need to solve that. Ultimately, I may have to accept I'll just have to fix the joints solid, which is acceptable, but rather less than ideal.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 04, 2011 9:42 am

plug and fill with epoxy, 'nuff said.
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Unread postAuthor: Hotwired » Tue Oct 04, 2011 9:50 am

Cocktail sticks.

Non-permanent and easily adjustable. Available at pretty much anywhere.

100 for 25p @ Tesco for example.

If there's a concern of a stick trying to sneak into the gap then use a liner inside the pipe.
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Unread postAuthor: Ragnarok » Tue Oct 04, 2011 10:04 am

jackssmirkingrevenge wrote:plug and fill with epoxy, 'nuff said.

Not sure that would work. It'd fix the inner pipe in place, but I really want it pushing out on the outer pieces.

Hotwired wrote:Cocktail sticks. Non-permanent and easily adjustable. Available at pretty much anywhere.

I'm... afraid you're going to have to explain that a bit more. Are you suggesting I stuff as many cocktail sticks in there as possible until it's forcing the inner pipe outwards?

Could work, although I'd have to reconsider how I was fixing the hinge in place.
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Unread postAuthor: Hotwired » Tue Oct 04, 2011 10:11 am

What is the hinge meant to attach to and what is being hinged?

I wasn't taking into account those factors merely the problem of expanding the inner section to increase friction.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 04, 2011 10:12 am

Ah, TL;DW - now I see the issue better.

12mm dowel wrapped with masking tape and hammered in?

12mm dowel split in two, then hammer a sliver of wood as a wedge in between them?
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Unread postAuthor: Technician1002 » Tue Oct 04, 2011 12:31 pm

Ball peen hammer and put a custom hammer finish on the outer surface will create friction dimples. Adjust quantity and depth to suit.
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Unread postAuthor: Ragnarok » Tue Oct 04, 2011 1:51 pm

Hotwired wrote:What is the hinge meant to attach to and what is being hinged?

Well, long story short, I'm on a bit of a "weird modelling" roll at the moment, building 54mm scale versions of Warhammer 40,000 vehicles.

For example - on the left, my WIP 54mm Rhino (with 54mm model for scale). On the right, the 28mm version:
<img src="http://i772.photobucket.com/albums/yy3/MarcoSkoll/Inquisitor%20Models/WIP%20Models/CIMG1170.jpg">

So when I went completely mad, I decided to make a 54mm scale Warhound Titan (Here you have the 28mm version) - and I'd like the entire thing to be articulated, so that it can be reposed for various reasons (Standing, in motion, half destroyed, etc).

These are going to be the 14 toe joints. They're thus going to be helping support the entire thing really - most of the construction of the upper body is plasticard (polystyrene sheet, if that means nothing to you), PVC sheet, PVC pipe and Milliput - not hugely heavy stuff, but it adds up and there's as much lead, steel and copper in the feet and lower legs as I can manage, to try and keep it bottom heavy.

As far as how the joints will be used, the two outer rings will be connecting to the mid joint of the toe (probably by epoxy), the inner section will be connected to either the end section of the toe or the main foot, depending on which exact joint it is.

I had originally planned on drilling through into the inner pieces, then screwing through into the dowel to fix them more securely (As it'll have a small footprint I'm worried about the possibility of it twisting off its mounting if it's simply glued.)

jackssmirkingrevenge wrote:12mm dowel wrapped with masking tape and hammered in?
12mm dowel split in two, then hammer a sliver of wood as a wedge in between them?

I've considered the first one already, but I think the tape will just peel off. Best option I can think of on that front is trimming paper and then using wood glue to fix it in place as a wrapping,

The second one has also considered at bit already, and is probably the best option I can think of at the moment, as in theory, I can still screw through into the dowel. It's probably what I'll go with if nothing better comes up (perhaps modified as below), but it's not completely perfect.

One idea that has just come to mind would be splitting it and introducing a layer of plasticard into the gap to thicken it up slightly.

Technician1002 wrote:Ball peen hammer and put a custom hammer finish on the outer surface will create friction dimples. Adjust quantity and depth to suit.

Could work, although I'm worried that relying on a rough surface will wear down over time, and it's going to be a pig if it ever needs fixing.

Does anyone know of a form of friction paste/grease that will work on copper/copper surfaces?
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 04, 2011 1:59 pm

Ragnarok wrote:I decided to make a 54mm scale Warhound Titan


Sweet.

How about just soak the 12mm dowels and let them expand?
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Unread postAuthor: Labtecpower » Tue Oct 04, 2011 2:09 pm

Maybe you can give it a gentle tap with a centerpoint?
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Unread postAuthor: al-xg » Tue Oct 04, 2011 2:16 pm

Poor man's drill chuck lathe to turn the dowel down to the size you want ?
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Unread postAuthor: Ragnarok » Tue Oct 04, 2011 2:45 pm

jackssmrikingrevenge wrote:Sweet

Never do things by halves. Setting an Inquisitor game under a Warhound's feet is over the top, but damn, people will remember it.

How about just soak the 12mm dowels and let them expand?

Hmm. Do you think that'll put enough pressure on it or will it have gone too soft by the time it's expanded enough?

al-xg wrote:Poor man's drill chuck lathe to turn the dowel down to the size you want ?

Nice idea, but the problem is that the next size up I can easily get is 14mm, which won't fit a drill chuck.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 04, 2011 2:48 pm

Ragnarok wrote:Do you think that'll put enough pressure on it or will it have gone too soft by the time it's expanded enough?


Only one cheap and easy way to find out ;)

al-xg wrote:Poor man's drill chuck lathe to turn the dowel down to the size you want ?

Nice idea, but the problem is that the next size up I can easily get is 14mm, which won't fit a drill chuck.


Drill though the centre, put a bolt through, bolt fits drill chuck ;)
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