CLIMB ON

[claycts]

I have struck a nerve with the "CVIL ENGINEERS" among us. Using the standard deflection calculation for plywood. 5/8" on a 12" o.c. 2x4 grid will hold 900 psf. That is the floor of my storage garage that has 4 cars on it. Using the same calcs I came up with 1/4" ply PLUS 2" foam on a 16"o.c. grid of 1x4 should hold 125 to 130 PSF. Or more than enough for an HO railroad. THe problem is that is perfect world calcs with dry wood. Using the famous "IT WORKED BEFORE DESIGN" I am going with 3/8" plywood, 5/8" homasote and 2" foam for scenery area only. That translate to 1. plywood, 2. homasote, 3 Cork Road bed, 4. track.
Thank for all the input, mad my day!

[jacon12]

I just built my benchwork using 1/2 inch plywood with 2 inch foam on top. Like the others I think it is overkill in some ways. On the other hand I didn't know if I was good enough to keep the benches absolutely braced square and I knew the plywood, if I cut it right, would keep it rigid. I think if you build the benches square and you put the right bracing under it you probably could dispense with the plywood. I knew I'd never brace it correctly [:D]
Jarrell

[rrinker]

My benchwork is a max of about 2' wide. I don't need to nor do I plan on climbing on it. I HAVE leaned on it while standing on a chair so I could look straight down on some track while placing it, with no problems. Spread out, I think it could take my weight, but not on a knee or foot.

--Randy

[HAZMAT9]

Larry:

Using the cookie-cutter method I was able to fit in a river as well as risers. In fact, the layout calls for 13 bridges which is more than enough for me. The framing is the key which includes 1X3's cut to various widths to allow for the rise/fall of the plywood. Here's a link to my benchwork so far:
http://www.geocities.com/hazmat9us/Picture130.jpg

Steve

[Anonymous]

HAZMAT9,

I think if you want to have any rivers with bridges or anything like that, you are going to have to have something to cut down into. I think a 2" foam base on top of your plywood provides that capability.

Larry

[HAZMAT9]

Originally I had planned on a foam top layout but decided to go w/ 3/4" plywood since my track plan was based on a cookie-cutter type. Now I'm at the point of laying track and can't figure out if I want to lay track directly to the plywood or cover the plywood w/ 2" foam and go from there, since most of my other scenery will be foam. Steve

[howmus]

Hi claycts, I pesonally do not climb around on stuff on the layout. Nor do I climb around on steep roofs on buildings or climb up in Oak trees to cut of limbs. Found out about the last two the hard way.... Luckily I didn't damage anything permanently. LOL Your room sounds ideal for your layout. By keeping the room within close specs, you have eliminated the biggest reasons people have warping and other related problems. If you are not going to have a lot of weight and put supports reasonably close together, 3/8" plywood should work well as a sub base. 2" foam, again properly supported would work with no plywood. Go with what will work best for you. I don't think you are going to need 4 x 4 posts (pressure treated, of course) and 2 x 8 cross beams with 3/4" plywood to do the job! [}:)]

[Anonymous]

I agree with claycts Having benchwork you can drive a truck on and then change the oil from underneath is overkill. With the addition of 2"foam to even relatively light benchwork increases the the combined strength since the foam in essence becomes part of the benchwork.

[Anonymous]

George,

One other factor to consider in using an all-foam table top- will you be mounting anything under the top, like switch machines?
Mounting devices under the top onto foam is much more complicated vs. if you can mount to plywood.

Just some more food for thought.

Good luck,

Doug

[canazar]

I have used 2" thick foam on 2 different layouts now and I have great luck with it. I have gone as far 26" between supports. (dealin giwth 2 foot width) Some think i am a bit nuts for skimping on the wood but it is just money and time thrown away. Reason being, you should never consider "climbing on the foam" I have found while maybe it might hold you, you will cause dents and impressions in the surface. (I did that once and learned the hardway)

Just my .02 cents

John k

[selector]

You essentially have it right...although....and I don't have experience with 2" foam....I would hesitate about climbing up on it without at least some 1/4" plywood under it. I'm sure the 2" stuff is plenty strong, and 16" between joists or supports is nice and tight, but I would feel that much better about plywood. That's just me.

I know that others will say you are very safe. So, lay your foam over the 16" gaps and put some real weight on the gaps. Do it in such a way that you can measure sag as you add weight. If at some point you get sweaty palms, go get the plywood and do it the way I suggest.

Of course, if you are building in a series of hatches, then climbing up on a 'finished' layout should be avoided in the extreme....to my way of thinking. That would obviate the requirement for even 18" gaps; you could get away with 22-24" and save that much more in lumber costs, also minus the plywood.

[claycts]

At least you have a railroad all I have are plans! To busy with my other hobby, making money, but I will work on it soon, I HOPE!

[ukguy]

If you are using 2"foam over 16" spacers from what I have read you do not need any plywood beneath the foam (presuming you will not be climbing on it, although climbing on the foam would damage it regardless). This makes sense to me. Depending on your scenic construction and hence the road bed(foam OR ply) then warping may become an irrelevant issue, Obviously if you have included 'hatches' in the design then climbing on the layout will also be irrelevant.

Wanna send me $1200 so I can get the HVAC guy into my 18x21 workshop/trainroom, it sure is gettin warm down here in the south (MS).

Have fun and be safe
Karl.

[claycts]

After reading all the posts about plywood 1/4 up to 3/4" and the Foam deal. How many of you have to CLIMB ON THE TABLE? After the layout is done (I know they are never done) and the scenery is in you can not CLIMB on the layout. If you use open grid then you work between the grids. If you use a flat top you have to design in the REACH FACTOR so you can rerail and clean.
Am I missing something or is the point of how thick in MOST CASES a matter of over engineering due to fear of the WARP MONSTER?
I have designed access hatches any place that is more than 30" from the front of the facia. Th eroom is 18ft x 22 ft with full heat and a/c and stays at 68 to 71 deg with 40% or less humidty year round. I am in S.C. and for the cost of $1,200.00 I had my HVAC man set up the room. I figure that the money I save on wood and damage will pay for the a/c modifications.
This is my humble opinion after reading the posts.