I did a experiment,perhaps unscientfic;
I had some bricks,9inX4.5in,=40 sq.in. 5lbs each.
I laid a 8in wide pieace of 2in blue foam across supports 24in oc
useing a 4ft level as a guild.
at 10lbs it started to sag,but at 25lbs it still did not break,sag about 1/4 in
At 16oc saged at 15lbs,
A 3/4 pink peice at 16oc started to sag at5lbs, but held 20 befor breaking.
I'm not sure but I think you would have an awful pile of MR equipment to come uo to 5lbs in just 40 sq in.
anyway now I know
Thanks for informing us of your results. I believe those of us who have used extruded foam insulation board (EFIB) extensively have understood that the thicknesses of 1.5" and greater are plenty stiff. They should support virtually any conceivable hobby item made from a kit or purchased assembled if the are supported on centres near 24" or less. Even substantial electrical hand tools. I would use 16" centres for the one inch stuff.
I sure do wish some of our HO locomotives weighed as much as those bricks, though. Imagine what they could haul up our grades if their drive mechanisms were designed to withstand the demands.
Use beaded foam, almost no sag at 25LB 16oc.
selectorThanks for informing us of your results. I believe those of us who have used extruded foam insulation board (EFIB) extensively have understood that the thicknesses of 1.5" and greater are plenty stiff. They should support virtually any conceivable hobby item made from a kit or purchased assembled if the are supported on centres near 24" or less. Even substantial electrical hand tools. I would use 16" centres for the one inch stuff....
During layout construction - not the benchwork stuff, but the things that follow: track laying, scenery, etc., etc. - does no one ever have need to lean on the layout, or, as required on my upper level, actually get atop the layout?
Today, I was painting rail on the upper level. To reach much of the track, I stood on a stepstool, and to paint the normally-unseen side of the rails (a must if you take on-layout photos with the camera on the layout and pointing towards the aisle) I had to lean on the layout just to see that side of the rails....
On another part of the upper level, where it's 59" high and 38" deep....
.....I used a stepladder to climb up and onto the layout in order to paint rails out of reach and also the backside of them, normally out of sight.Last night I repaired a bunch of Micro Engineering turnouts, all with tight flangeways, and one so tight some locomotives couldn't even pass through it. Others had high frogs, and while most equipment passed through, almost everything from locomotive to caboose was jostled so much that I thought that it would derail. For all of these it was necessary to use files, and with some force, too, but with solidly-built benchwork, I had no worries of causing damage or ripping the layout from the wall.I'll be doing some scenery work with foam, but not anywhere where I might, at some point, need to support my weight on it. While my plaster-on-screen scenery won't likely support my full weight...
I know that I can lean on it, bent over and stretched as far as I can reach, supporting myself with one hand. I just now checked, and the reach is about 5' at the location shown.
I know that some layouts are narrow shelves, with no such reaching requirements, and perhaps not too many bother with scenes of any appreciable depth, but during construction, all manner of tools and supplies can be on the layout. You shouldn't have to worry that the layout will sag, or, even worse, collapse.In my experience, better to over-build at the beginning than to worry later when you need to do something not originally anticipated. Suit your construction methods and materials to your particular situation.
Wayne
many rc wings, especially saiplane wings, are foam covered with fiberglass or carbon fiber and are very strong and stiff.
while studying airplane wing spar design, i did simple experiment.
i took a piece of 1/2" foam, about 2ft x 4", glued a thin sheet of balsa on once side and put packing tape with the glass fibers on the opposite side.
with the packing tape side up, the "spar" was very rigid. the balsa resisted compression and the glass fibers in the tape resisted expansion. Basic concept of an I-beam.
of course there was nothing to prevent the tape from compressing or the spar bending upward.
i'd be curious to see if putting any glass fiber packing tape under the foam would improve its rigidness (minimize flexing)
greg - Philadelphia & Reading / Reading
gregci'd be curious to see if putting any glass fiber packing tape under the foam would improve its rigidness (minimize flexing)
If the foam was fastened, glued on all four sides of a frame,like open grid. I think you would get same results.
But, why? At 24oc or 16oc supports, you can't park enough MR stuff to make it matter.
I don't thinkyou can walk on it , but why would you want to?
Just to show how strong the beaded stuff is, I have a feind who is disabled and put his hand on a grassy spot to lift himself up, I cringed as it was beaded foam covered in plaster wrap with ground foam on top. Didn't say anything except be careful and when I went to look at it closely after he left, I was amazed as no visable damage.
UNCLEBUTCHI don't thinkyou can walk on it , but why would you want to?
it's not a question of how much weight can it hold w/o breaking
it's a question of how much weight does it take to start bending (stiffness)? ... or deform over time
i have cars that will roll on no noticable grade.
gregc UNCLEBUTCH I don't thinkyou can walk on it , but why would you want to? it's not a question of how much weight can it hold w/o breaking it's a question of how much weight does it take to start bending (stiffness)? ... or deform over time i have cars that will roll on no noticable grade.
UNCLEBUTCH I don't thinkyou can walk on it , but why would you want to?
I have no clue to as if that data even exist.
What I can tell you is what I've seen; I have never seen a sheet or piece of foam. in any tickness, that was bent,cupped or twisted.
I've seen a vast amount of plywood,and OSB, and other wood based produccts deformed to the point of being useless.
I guess it might depend on just how mutch weight over how mutch space,over how long a time.
BTW I would fix those cars, I prefer mine to stay where I drop em
A very neat experiment.
It appears that the sag was measured with the weight in place. Very reasonable.
I wonder what the sag was after the weight was removed.
I wonder what the change in sag would be over time. This is important, as most layouts are designed to exist for quite a bit of time.
So, with that 2" stuff, where it sagged 1/4" at 25lbs, to what extent did it "spring back" to flat? And then, how did/would things work after maybe a month or two of 25lbs?
I worked on a project where the plastic failed months and maybe years later.
Or, put another way, the "famous" plastic axles on P2K locos didn't fail right away. It took a long time for them to get around to doing their trick.
Ed
7j43k A very neat experiment. It appears that the sag was measured with the weight in place. Very reasonable. I wonder what the sag was after the weight was removed. I wonder what the change in sag would be over time. This is important, as most layouts are designed to exist for quite a bit of time. So, with that 2" stuff, where it sagged 1/4" at 25lbs, to what extent did it "spring back" to flat? And then, how did/would things work after maybe a month or two of 25lbs? I worked on a project where the plastic failed months and maybe years later. Or, put another way, the "famous" plastic axles on P2K locos didn't fail right away. It took a long time for them to get around to doing their trick. Ed
In my ''unscientific'' try; the foam sprang up as the wt. was lifted. We are talking a few minutes.
As to long term; ?? But then in realty, would there be a case where say, 15/20lbs would be placed on 40sq. in. and then left there for any amount of time ? Even at 10lb per 40sq in,if my math is right comes out to <30>lb/sq ft. Thats a lot of something on a layout.
I'm sure there are many factors I didn't consider. It was a spur of the monent type thing.
But it did prove to me, that 2in foam is plenty strong enought for a layout.
Right now I'm useing 3/4 pink stuff,just because I have a pile of it.
UNCLEBUTCH As to long term; ?? But then in realty, would there be a case where say, 15/20lbs would be placed on 40sq. in. and then left there for any amount of time ?
As to long term; ?? But then in realty, would there be a case where say, 15/20lbs would be placed on 40sq. in. and then left there for any amount of time ?
A very good point.