Material weight limits for base to model supports

[slookabill]

I've gotten several kits that have bases to go with the model(plus several without bases), and I'm trying to figure out various materials size/thicknesses to connect the two. Is there any formula/rule of thumb for material(brass/acrylic rod/aluminum/etc) thickness, and then length for various weights of models? I've used brass tubes for several, but I'm afraid at the size I've used so far, won't be enough for heavier models, plus have thought about eventually wanting a hollow tube for wires to go through, and also use acrylic rods for support.

[EVApodman]

A brass tube will be stiffer than a rod, either brass or acrylic. In some cases I have used 2 supports for a model.



An acrylic rod gives the nice impression of a spaceship suspended in the air, but doesn't allow power lines to be fed through it. Also remember the longer the support the more flexible it will be, so try to keep them relatively short.

[slookabill]

Yeah, I'm just wondering about diameters/length to weight relationships say 1/4" acrylic rod is good for most models at 5", or need 1/2" or larger size after x inches or similar

[Rocketeer]

Although you could in theory do engineering-type calculations and figure out the amount of deflection a brass or acrylic or steel rod or tube would have, it's probably easier to just buy yourself a handful of various size rods and tubes and experiment.

In any event, it's not usually strength that's the problem; it's (as alluded to by EVApodman) stiffness. You want your support rod to be stiff enough that your model doesn't sway back and forth. It's also good to support the model at its center of gravity, to avoid putting a bending stress into the support (unless you beef up the support to compensate).

That said, here are a couple of my models and what I used to support them:

Aventine is quite a large model. It's supported on an L-shaped 7/32" brass square tube. It tends to sway a bit, and if I were going to do it again I might use 1/4" tube instead.



This little witch is 1/6 scale; she's supported on an L-shaped 7/32" square brass tube. The moon behind her is supported on a 5/32" square tube; it tends to sway a little.



MGP-1 and the Imperial Aeronef Haifeng are both supported on 1/4" acrylic round rod. Both are supported right about at their centers of gravity. No problems with either.




The Edwardian Aerial Housecar is supported on a 1/4" acrylic round rod. But it is not supported at its center of gravity--rather far away from it, in fact--and the rod tends to bend. In fact, I think it may have taken on a slight permanent set.

[Kylwell]

If I'm concerned about weight being a problem I'll see how much the model box, with sprue, deflects what ever I'm thinking of using for support. This is easily done by setting the box on edge, sliding the rod or tube under and lifting. Yes, you'll have to guide it with one hand to keep it from falling off but if it bends too much, go heavier.

[EVApodman]

I like the witch. Reminds me of the Fleetwood Mac song "Rhiannon" which was based on the tales of a Welsh witch.

Since PB will no longer support my 3rd party pics I posted earlier, here they are again.

http://s61.photobucket.com/user/2001shi ... %20shuttle