| T O P I C R E V I E W |
| Rraven |
Posted - 05/07/2012 : 9:18:57 PM
I'm embarking on building small by most standards a 7x7 foot "L" shaped On30 layout and I want to minimize the weight of the bench work. To that end I have been searching for any information on building Masonite based girder frames sometimes called a warren tress system. It seem to be a very elusive thing to locate. Can anyone lend me a hand, advise or relate your experiences? |
| 15 L A T E S T R E P L I E S (Newest First) |
| Rraven |
Posted - 05/10/2012 : 10:28:33 PM
Well with Palram and most of the newer Sintra type of Foamed PVC boards the Rated heat deflection temperature is 63c or 145f and the VICAT softening temperature is 75c or 167f lets just hope most homes are not kept that warm lol |
| Sean_OBrien |
Posted - 05/10/2012 : 9:05:31 PM
I agree - PVC (foamed, cellular or solid) has a lot of advantages. I use it to do a lot of building work on railroads (cellular PVC especially since you can carve it pretty easily for things like brick work). My only real concern would be the heat related issues with using that as a structural support.
While the scenario would take some doing to arise - it isn't too uncommon for a lot of us... Heat and PVC are great, unless it is holding something up. If a heat register is under your benchwork, it will help to hold in that heat. PVC looses its rigidity pretty fast as it warms up (all the way up to the point where you are working with a wet noodle). Granted, you shouldn't get that warm in a regular room - but keep in mind where the registers are and what not. In the situation that Brian has to work with - the water heater and furnace would likely get warm enough to cause a catastrophic loss of structural rigidity. |
| Rraven |
Posted - 05/10/2012 : 8:49:24 PM
My bad yes you are right it is actually "Sintra" but the product has developed allot in the recent years. we also use one brand called PalRam and it comes in 22 colors etc... One thing to keep in mind with it is that it is PVC and as such you have a wide range to adhesives you can use with it. Should you have the advantage such as myself you have access to specialty tools for dealing with all sorts of cutting needs kinda helps.. sorry if I sould like I'm bragging |
| Sean_OBrien |
Posted - 05/10/2012 : 7:43:46 PM
I think you mean Sintra. If that is the case, I seem to recall that as being sort of crumbly...though it might have been some older stuff that I was working with. |
| Rraven |
Posted - 05/10/2012 : 7:27:52 PM
the alternative would be another PVC based product called Cintra it's a moderately expanded PVC or foamed board and comes in a range of thickness from 3mm up to 25mm and can be cut and milled liked wood. |
| Sean_OBrien |
Posted - 05/10/2012 : 7:21:20 PM
Yep - that stuff is similar to the material we used to use for the floors on C-17s...though that had an aluminum honeycomb instead.
http://www.portafab.com/alum-on-alum.html
Very, very pricey...but you can park a HMMWV on it.
On the laminated ply/foam/ply - the biggest thing to remember is to give it time to fully dry. The first time I did it was to test the feasibility and I tried it out before everything had set up in the middle. However, once it had had time to cure I was able to place a 2x8 foot slab between two cinder blocks and I stood in the middle of it. There was only a 3/4" sag on it with my 200 lb self standing in the middle of the 7 foot or so span on a 1/4" birch / 1 1/2" pink foam / 1/4" birch sandwich.
Also - clamping things like this can be somewhat awkward, so if you don't have any...see about making a few sets of clamping cauls. The slight curve makes sure that you are able to clamp the middle of the sheets together evenly.
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Was just poking about the interwebs to see if I could find something done by someone else that was similar...and stumbled across this:
http://www.kerfkore.com/index.htm
The Foamkore and Foamkore-Green look to be the stuff (though thinner by a bit). Might be something to look at depending on how much they like their stuff (i.e. - how much it costs). |
| Rraven |
Posted - 05/10/2012 : 6:01:25 PM
On the other hand seeing as I own a Large Format print shop I have access to a product called Allucore it's a PVC core with an aluminum skin on either side very tough and pretty light weight, down side even at my "cost it tends to be pricy. |
| Rraven |
Posted - 05/10/2012 : 5:54:28 PM
I'm leaning toward the Ply/High Density Styrofoam/Ply sandwich I just happen to have a couple of good 2 side sub flooring you know those 4x4 square ones from Home Depot I'll do a test and see how that goes for workability and mess etc... |
| railmus |
Posted - 05/09/2012 : 8:56:40 PM
Take a look at Mario's site for some ideas.
Lightweight Layouts
http://www.modvid.com.au/html/body_aluminium_modules.html |
| Sean_OBrien |
Posted - 05/09/2012 : 3:56:52 PM
quote:
Originally posted by Rraven
wow this is allot of really good info thank you guys. What I was envisioning was the "I" beam concept but had thought assembling them into triangular shapes hence my reference to a warren truss look when viewed from the top down. I'll play around with a couple of possible merging of the two concepts both the "I" beam and the sandwich.
I have seen that done a few times but you need to consider how the forces are going to play against what you are trying to build.
For us, in this case - the primary force that you need to deal with is gravity. There are other forces as well - the paint and glues used to finish scenery on top of the board will contract and have a tendency to pull up on it...but that actually is moving in the same plane as gravity, just the opposite direction. Using a triangular grid in the benchwork which is oriented horizontally will not due much to counteract that force. If you do not make sure your intersections are nice and tight it will also reduce the strength of the benchwork against the vertical forces as well.
Anywho, the S&S bench work is sort of a fancy torsion box. I am not too sure how much weight is being saved per unit by cutting the holes in the bottom of the frame work. If my memory serves me right (and it rarely does) you are looking at around 20 lbs per 1/4" sheet of Luan, so you won't be saving much overall. It looks neat and you can access the bottom area for wiring if you need to. For permanent (or semi-permanent) installations I would probably forgo the extra work of cutting those out and use full sheets with a chase at the front or back or both for the wires. You can then use an aircraft bit to drill into the grid and fish the wires through the resulting holes.
Remember, your stresses will only really act on the top and bottom of whatever support material you decide to use (granted the thickness of that support material increases the strength though it is less due to the thickness and more due to moving the two stressed surfaces further apart but still binding them together so that they move in conjunction with one another). That is why I-beams are designed the way they are and things like wing ribs normally are Swiss cheesed with lightening holes.
Along a similar idea though...the S&S benchwork would be stronger still if they cut the holes in a manner which left an "X" in each section. That would allow forces to transfer from corner to corner on the exterior skins as opposed to only along the vertical supports. |
| dti_nut |
Posted - 05/09/2012 : 3:10:44 PM
I built some very lightweight/thin benchwork for my staging yard area. Since it surrounds my furnace and passes in front of the water heater, it is all removable, and is mounted on shelf brackets and bolts together with a couple 1/4 inch bolts and t-nuts.
I wanted it to be light weight/rigid, and somewhat simple to construct.
So far - it is working out nicely.
Regards,
Brian
Modeling the DT&I of the 60's & 70's
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| MarkF |
Posted - 05/09/2012 : 12:13:58 AM
Take a serious look at the way the Sipping and Switching Society builds their benchwork, mentioned in Sean's post above. I have seen their layout a couple of times and quite honestly, their website doesn't do it justice. It's gorgeous and well built.
I examined their benchwork closely one time when I saw them at a show and was extremely impressed with it. Not only is it lightweight, but due to the materials used, it appears to be extremely stable as well. Best part is, you can really customize each section to just about any size and or shape you want. |
| Rraven |
Posted - 05/08/2012 : 9:54:29 PM
wow this is allot of really good info thank you guys. What I was envisioning was the "I" beam concept but had thought assembling them into triangular shapes hence my reference to a warren truss look when viewed from the top down. I'll play around with a couple of possible merging of the two concepts both the "I" beam and the sandwich. |
| AVRR-PA |
Posted - 05/08/2012 : 4:34:52 PM
quote:
Originally posted by dti_nut
I would say that some of the lightest/stiffest benchwork I have seen comes from the modular layout builders.
Take a look at the design here:
http://s-ss3.home.mindspring.com/id1.html
It is pretty cheap to build, and is nice because the shape can done anyway you like.
Regards,
Brian
Good link, Brian. I've built some waffle frame modules, for my own use (with a local FreeMo group) and for a client. It's certainly more work than the usual module construction, but it's definitely light and VERY rigid since it's a torsion box type of construction.
Don
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| dti_nut |
Posted - 05/08/2012 : 11:14:25 AM
I would say that some of the lightest/stiffest benchwork I have seen comes from the modular layout builders.
Take a look at the design here:
http://s-ss3.home.mindspring.com/id1.html
It is pretty cheap to build, and is nice because the shape can done anyway you like.
Regards,
Brian |
