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1/2" Plywood vs 3/4" Plywood?

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Posted by UNCLEBUTCH on Saturday, August 17, 2019 9:44 AM

betamax
I actually did some rough testing of the deflection in a 5' by 2.5' frame built out of Baltic Birch. The boards were 3.5" wide. For the test I piled precision weights on the center of the frame, with a total of 73.8 lbs. in the center. Using a laser I marked a zero point, added the weight, and measured the difference. With the frame made of 12mm plywood, with five crosspieces of 12mm, the deflection at the center was 1/8". Same construction with 18m

  How is it even possible, to get 70lbs of MR stuff in a 5ft span ?

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Posted by carl425 on Friday, August 16, 2019 10:39 PM

One more vote for 3/4.

I have the right to remain silent.  By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.

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Posted by betamax on Friday, August 16, 2019 10:28 PM

I actually did some rough testing of the deflection in a 5' by 2.5' frame built out of Baltic Birch. The boards were 3.5" wide.

For the test I piled precision weights on the center of the frame, with a total of 73.8 lbs. in the center. Using a laser I marked a zero point, added the weight, and measured the difference.

With the frame made of 12mm plywood, with five crosspieces of 12mm, the deflection at the center was 1/8".

Same construction with 18mm: 1/16".

 

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Posted by snjroy on Friday, August 16, 2019 10:24 PM

I went with 3/4". Thicker ply allows you to do a lot of hard banging without damages... it also allows you to reduce the number of supports. But it makes it more complicated when installing Peco switch motors under the layout.

Simon

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Posted by ATLANTIC CENTRAL on Friday, August 16, 2019 7:14 PM

3/4" Birch plywood here, and benchwork framing with 1x4 Poplar, yes, like a piece of furniture........

Homasote sheets for yards, homabed roadbed elsewhere.

Foam? What is that?

But seriously, a lot of different methods work fine. Thicker plywood means fewer supports, better lumber means easier construction and more stablity in lots of ways.

I have used laminated OSB, every thickness of plywood, dimensional lumber, build framing from high quality Poplar and surplus 2x4's.

And I have used every framing method, open grid, L grider, table top, cookie cutter, etc.

And I always build benchwork that can support my 200lbs........

My new layout will be a combination of open grid and table top benchwork, which will also mean a few "cookie cutter" transitions.

Still don't understand the attraction of foam? But to each their own. 

Sheldon

    

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Posted by SeeYou190 on Friday, August 16, 2019 7:05 PM

Mark R.
Tony Koester many years ago when asked why he used 3/4" plywood for his road bed. His response was that nobody made 1" plywood.

.

That is exactly how I feel too.

.

-Kevin

.

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Mark R. on Friday, August 16, 2019 6:47 PM

I'll always remember a comment made by Tony Koester many years ago when asked why he used 3/4" plywood for his road bed. His response was that nobody made 1" plywood.

Mark.

¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ

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Posted by UNCLEBUTCH on Friday, August 16, 2019 6:46 PM

 Depends on how mutch money you want to spend. They will both do the job,as well as Mel stated 1/4.  or3/8 or 5/8  I've seen OSB used also.

IMHO 3/4 is over kill and wasted money,along with ''prime''

Was it me, 2in. foam.

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Posted by doctorwayne on Friday, August 16, 2019 6:34 PM

kenben

Wayne, reach is not an issue. There is a center open area that I "could" place a pop-out area for scenery in the future. But everythign is within a 2ʻ reach.


Okay, that makes sense.  I was going only by the dimensions.
 
Wayne
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Posted by RR_Mel on Friday, August 16, 2019 6:33 PM

Well I normally over design and build everything but . . . .   When I needed to elevate my layout after many hours of thinking I decided it was a lot easier to go with ¼” plywood.  That was back in 1988 and the ¼” plywood has worked perfect since day one.
 
I used 4” width for the roadbed and 1”x 4” bracing between the basic ½” plywood base.  My layout is HO scale 14’ x 10’ x 33” off the floor, the grade goes from 0 to 10” in 25’ or about 3.3% all on ¼” plywood.  It levels out at 10” then back down on a 30” radius helix back down to the basic level.
 
I also used ¼” plywood for the helix with 1”x 2” side bracing, again no problems after 31 years.
 
I did use a lot of wood screws and Carpenters glue on all of my layout.  Too make things even more acceptable to problems my layout is built on casters and I move it around the garage and even out onto the driveway when I need to clean the garage floor.  Out on the driveway it is a neighborhood kid magnet.
 
So I would say it depends on your carpentry skills when it comes to sizing the plywood.  I would say that ¼” is most likely half as hard to work with compared to ½” and 75% easier than ¾” plywood and a lot less weight.  The cost would also be a lot less.
 
 
 
Mel
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by kenben on Friday, August 16, 2019 6:17 PM

Wayne, reach is not an issue. There is a center open area that I "could" place a pop-out area for scenery in the future. But everythign is within a 2ʻ reach.

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Posted by SeeYou190 on Friday, August 16, 2019 4:27 PM

I always spend the extra and over-build. 3/4" plywood only for me.

.

-Kevin

.

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by hardcoalcase on Friday, August 16, 2019 3:48 PM

For the subroadbed, I use 1/2", 4 ply plywood, on risers spaced about 14" to 16" apart, and over three layouts, I've been well satisfied with it.  Its sturdy enough for me to lean on it if I need to do a long reach over the layout.  IMHO, 3/4" ply for subroadbed is overkill.

I used salvaged 3/4", 8 ply plywood, ripped to 1" x 4" lumber for the benchwork which is a combination of open grid and L-girder, and I highly recommend it.  Using new 8 ply is about the same cost as buying prime stick lumber, and its virtually free of warp or distortion issues.

Jim

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Posted by doctorwayne on Friday, August 16, 2019 2:23 PM

Most of the sub-roadbed on the main level of my layout is 3/4" firply, good one side.  Most of it is also cut-out curves of varying radii, supported by risers...

The few areas of straight track are on either the same plywood cut into strips, or on 1"x2"s or 1"x4"s.  Staging yards and all of the partial upper level are on sheet plywood of various thicknesses.

If you're making a table-top style layout, 1/2" or even 3/8" plywood, properly supported, is suitable, while cookie-cutter style roadbed is better, in my opinion, in 3/4" plywood.

The dimensions of your layout may cause some issues with "reach", especially once you have scenery and structures in place.

I'm not sure what you mean by "prime plywood", but good-one-side in most grades is sufficient.  Once the scenery and ballast is in place, the plywood won't be visible.

Wayne

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1/2" Plywood vs 3/4" Plywood?
Posted by kenben on Friday, August 16, 2019 1:22 PM

Finally building my first HO layout, 8ʻ x 6 1/2ʻ. For the subroadbed is 1/2" or 3/4" plywood better? Iʻll buy 2 sheets of 4ʻx8ʻ prime plywood and they will be cut up a bit for track elevations etc.

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