Baseboard Materials

What? You too?

-Extra mass doesn't vibrate.

-Extra mass stops transmittion of sound.

-Extra mass resists shock forces.

-Extra mass can make the structure stronger during removal.

-Under-engineering can result in a baseboard that warps or distorts after construction, especially during the scenicking stage when more moisture is likely.

-Depending on materials chosen for construction, price difference is minimal. My layout building time is longer than my period of residence in any home so far, so I build in layout sections that will be "transportable".

Regards, Greg.P.

I was arguing for heavy construction, but you seem to be describing my baseboards as light! Generally I use 3"x1" perimeter frames with 2"x1" crosspieces at around 1 foot by 18" intervals. Frame area is kept to 16 square feet (4'x4', 8'x2' etc). I tend to use

12mm(1/2") chipboard plus 12mm "Pinex" (a little softer than Sundella) layered for the track bed whether as a flat top or just track width. I gusset the corners where the baseboard is not table top. Everything is screwed or nailed as well as glued. The legs are 2x2.

Gregory wrote: -

Sorry Gregory, I may have misquoted your post.

I see that you use the grid construction method.

I use "L Girder"

The basic substructure along each of the four walls and down the centre of the peninsular are two "L" girders made from 1 x 4 pine.

Across these and spacing the "L" girders about 24" o c are 1 x 3 pine stringers, laid on edge, on 16 to 18 inch centres and screwed from below through the top chord of the "L" girder.(For easy screw removal).

All the roadbed is then supported by risers screwed to the stringers. The risers are either "T" shaped or, when supporting yards etc, are made from 1 x 3s screwed to the risers so they look like football goals. The road bed, made from a 1/2 plywood and 1/2 compressed paper insulation product, is then attached to these risers, from below, with screws using predrilled 1 x

1 pine as cleats. The risers are what form grades and or are used for final levelling of the road bed.

The whole layout is supported on either 2 x 4s or 2 x 2s depending on the location of the legs and the load (From under benchwork shelving) that the legs are expected to carry.

While this method results in fairly deep benchwork, from about nine inches to over 12 in some locations on my model railway, it is really stable and can be leaned on, bumped against, used as a workbench during early construction (I clamped my vice to it for cutting lumber and later for filing the rail when making hand laid switches/turnouts/points).

You can as I have done for my main staging yard, even suspend hidden yards from under the benchwork by simply dropping the "risers" from the stringers and attaching another stringer between the suspended risers. This was all done AFTER most of the layout was built and sceniced. Not that I recommend this approach as it was somewhat awkward to do, but try doing that with traditional UK baseboard construction.

The other joy of this method, apart from extremely strong and durable benchwork, is that scenery can easily fall below and rise above the track with few, if any, problems.

-- Cheers Roger T.

of the Great Eastern Railway

I beg to differ. Everything vibrates if displaced, preferably at one of its natural resonant frequencies. Increasing the mass of something will alter its natural vibration frequency but (mostly) only because you've changed its geometry.

R.

"Richard"

Perhaps Gregory should have written, Extra mass doesn't vibrate as much?

-- Cheers Roger T.

of the Great Eastern Railway

Perhaps, but he would still be as innaccurate as he was before :-)

If you have a structure and it's vibrating and you want to reduce that, then it may be that it's resonating with some driving frequency (locomotive motor; operator moving about the room; road in front of the house; etc). So you want to shift the resonant frequency away from the driving frequency, which in general you can't do much about. Adding extra mass may do the trick... But it's not adding the extra mass per se; it's because in doing so, you've changed the whole geometry of the structure. Taking away mass might also do the trick. So might altering the distribution of the mass, or altering the rigidity of the structure (I could make some incredibly lightweight baseboards out of mattress foam and they'd be quiet as church mice, but they'd be a bit useless to put scenery on. :-)

Going off on a related tangent; cyclists, particularly heavily loaded ones descending hills at speed, sometimes experience front wheel "shimmy", what motorcyclists fear as the dreaded "tank slap", where the combination of bike + rider undergoes forcing from road irregularities, a resonant frequency is reached, and the handlebars suddenly start to shake/twist violently from side to side. The experience is terrifying and usually ends painfully. Bikers, I believe, can accelerate out of it (and thus change the forcing frequencies, moving them away from the bike/rider natural resonance). But cyclists usually don't have the power to do this, and so when they start to experience this vibration can damp it by clamping their thighs/knees around the top tube of the bike. This doesn't affect the total mass, but it affects the geometry and damping and thus the natural resonant frequencies of the bike/rider, and usually this does the trick and the shimmy/tankslap/vibration/"noise" goes away.

R.

Very true, but I'm not going to build and rebuild baseboards until I get the natural vibration frequency above the audible range - it's much simpler to add mass in the right places and bring it to the bottom end of the audible range.

I think you're using pretty much the same quantity of timber that I am. What you're missing (relatively) is the torsional stiffness that I get with my 5 sided box, but you're gaining versatility.

I've started with my staging yard at the bottom level. Risers then hold the top (station) baseboard above it so that the upper baseboard can be lifted off. The backscene sheets screw to the 3x1" framing to become an additional structural part.

Perhaps you should glue your scenery on!

With my baseboard construction, the only actual "table top" is the staging yard and corner gussets. The rest of the track is raised by risers screwed to the cross framing, so my scenery level is probably as free as yours.

Regards, Greg.P.

The trick is to get all the requirements met in the one baseboard. As failure tends to show up after most of the hard work has been done, I tend to revert to the one method that consistantly works for me.

Yes, it does effect the total mass of the components that are shimmying - it is the frame that is shimmying in the first instance, not the frame and rider. When the rider clamps the frame, he/she adds a portion of his mass to the components shimmying.

Regards, Greg.P.

=>Yes, it does effect the total mass of the components that are shimmying - it is =>the frame that is shimmying in the first instance, not the frame and rider. =>When the rider clamps the frame, he/she adds a portion of his mass to the =>components shimmying. =>

=>Regards, =>Greg.P.

No, the total mass is the rider + bike. If you'vbe ever experienced the phenomenon, you know that the vibration is tarnsmitted to the rider and the rest of the bike, and that the vibrations of the different elements relative to each other that cause the danger of losing control. The rider changes the geometry of that combination, by connecting the masses in a different pattern. In this instance, geometry matters more than mass. It's also essential that the rider _clamp_ the crossbar - merely moving the masses relative to each other won't make much if any difference.

BTW, both of you have ignored stiffness, elasticity, and the nature of the connections between elements of the structure. The first two determine the natural vibrating frequencies of the structural elements, and the last determines how vibrations are transmitted, reinforced, and damped within the structure.

"Gregory Procter"

LOL. I didn't think of it in that context. :-)

I'll agree about scenery. I've found that the grid method requires better carpentry skills than "L" Girder, hence my preference for that system.

-- Cheers Roger T.

of the Great Eastern Railway

Wolf Kirchmeir wrote:

Let's try another example - a loud speaker. (this has more in common with our layout baseboard as it's not travelling along the road) The cone vibrates while mechanically connected to the speaker box. If I hold/clamp the speaker box, the quality of noise produced by the cone changes very little. If I hold/clamp the cone then the sound changes drastically. My baseboard works in much the same way:

- If I use a 4'x4' 3x1" perimeter frame with say 3/16" (I'm mentally converting metric to your funny measurements here) plywood top placed loosely on top, I've created a noisy, vibrating layout. If I glue and screw the plywood to the frame I change the vibration and stop the "rattle". A train running on a circle of track on this baseboard is going to be LOUD. The two options I have tried from this point are a: increasing the thickness of the top and b: adding cross bracing. Adding cross bracing limits the vertical movement of the vibrations - I guess halving the area between bracing quarters the movement/deflection assuming the bracing is effectively rigid. Doubling the thickness appears to achieve the same result but with a much greater increase in weight. The difference is that the thin top sheet still sounds 'harsh' (subjective) even though the volume is reduced and it still needs to cope with the weight of a person leaning/sitting/standing on it. One could keep adding more bracing at ever decreasing distances until the physical strength requirement is met, but my limit for bracing spacing is the length of my electric drill with bit and a riser - about 15". At that spacing, my 12mm(1/2") thick chipboard doesn't vibrate at any audible frequency I can discern. The train itself now rattles on the rigidly fixed track - unscientifically, I guess that the problem is that the loco vibrates and the hard surface reflects the sound/fails to absorb the sound. At this point I add the 12mm(1/2") "Pinex" softboard which is cheap and lightweight, takes pins and can easily be chisled or cut with a Stanley knife to make trakside drains etc.

The system works for me! :-)

Hmmm, I did say that I glue and screw. I also commented that I rejected "L girder" because it lacked the torsional rigidity for transportation.

Oh, and the point of continuing this discussion is to compare methods and to troll for better techniques. :-)

Regards, Greg.P.

Gee, I never considered that my carpentry skills were better than absolute basic standard - the two things I've learned over the years are; to aim for right angled cuts in at least one plane, and to ensure the mistakes cancel each other rather than compound! (no, that's not a joke)

Regards, Greg.P.

=> At this point I add the 12mm(1/2") "Pinex" softboard =>which is cheap and lightweight, takes pins and can easily be chisled or cut with a =>Stanley knife to make trakside drains etc.

By doing this you have changed the connection between the track and the baseboard. The Pinex itself has little internal connectivity (that's one reason it's _soft_), so that in effect you have disconnected the track from the baseboard --> less sound transmission. Etc.

That's what I wanted to achieve! My construction methods work, for me :-) I reached this method in stages, by trying without the Pinex, with thinner and thicker board etc.

Hi. What is Sundeala? I see reference to that material in British model railroading magazines that I receive. John Hudson. Portland ,Oregon, USA What would it be comparable to? Homosote??

What is Homosote? ;-)

Sundeala is a medium-soft compressed paper board. It's almost rigid enough to be used framed as a baseboard.

Regards, Greg.P.

"Almost rigid enough" doesn't properly describe Sundeala as a baseboard material.

For years it was Cyril Freezer's ideal material - that should put you off instantly - used on top of a 2" x 1" wooden framework. Even if you made the framework with cross members every 3" it wouldn't be good enough to prevent the Sundeala sagging over time. I reckoned that the only reason that Cyril recommended it was that it took Peco spikes and pins easily!

As for us>

snip