Am I missing something?

Is there supposed to be a video in this post? Because I don't see your technique just a couple of paragraphs leading up to it.

Missing video???

I am not sure what the problem is? I embedded the link and it shows up for me?

Try this........

Geoff

No Missing Video

The video works for me. Nice woodworking ezio.

Joe

Video's there

Geoff,

Nice little tutorial. I like the spline idea, better than screws.

How well do you think biscuits would work?

Bernd

Very cool idea!

Very cool idea!

How well do you think biscuits would work?

Biscuits work fine if the plywood is thick enough. I used biscuits for 3/4 inch thick O scale roadbed with no problems.They'd probably work  for 1/2 inch but below that doublers under the plywood would likely be better.     That's a nice trammel in the video but I just swing the arcs with a steel tape hooked to a nail or if I have a lot of curves of the same radius to cut I make one template piece then use it to lay out the others. By nestling the sections together there's very little waste when cutting most radius curves.....DaveB

biscuits

Bernd,

I tried biscuits and they do not work well because they do not secure the entire end of the pieces. The football shape only allows for a minimal contact area and the biscuits are not as strong as a full length piece of plywood spline. After my segments are glued up they are virtually one continuous piece of plywood with no flex or weakness at the joint.

Biscuits were my first choice but the joint was not strong, and you always got a bit of flex at that point. What is known as a "scab joint" has been suggested and that does the job just fine as well. That is when you butt the two pieces together and then glue and clamp a third piece under those two.

Geoff

steel tape

Dave B,

Your method may work for a quick piece or two, but I do not believe you can get the accuracy from simply using a steel tape with the hook over a nail and holding a pencil in position. The idea of making a single pattern sounds alright, except that you have no way of marking the track center on each duplicate piece. What I am suggesting not only provided the accuracy of a purpose built jig, but also the convenience of making all the marks for each piece with no guess work and all at the same time. The two most important marks are the track centers which must be a true and constant radius when joined together, and the cuts at the ends of each segment that must be truly tangent to the curve, otherwise your segments will not form an accurate and constant radius when assembled. Don't get me wrong, if the tape works good enough for you, that is fine. But I don't see how you can maintain the consistent accuracy that I was looking for?

Geoff

Switched devices, can see the video now

On the iPad and on my corporate computer the video didn't even display as not playable, it was just a blank space.

I do have one question though, why the space between the pieces, why not increase your roadbed width enough to account for saw kerf and reduce the total number of cuts made?

Football shaped biscuits

Geoff,

Great to know you tried them and it didn't work for you. Guess I won't reinvent the wheel then.

Thanks for the reply.

Bernd

+1 scab joints

Scab joints work well for me. Simple, easy, uses up scrap ply, plenty strong enough. When screwed from below the sub-roadbed section can easily be removed and reinstalled. Not possible with biscuits.

Joist hangers?

Alan,

What kind of "hangers" are you using in that second picture above? They almost look like joist hangers except they seem like the are just 90 degree brackets. Home improvement stores carry those?

Bernd

Hangers

The nailing brackets are common Simpson StrongTie products pt# A-34 and LS-30. Yes, big box stores have them.

Here is a detailed post on the subject:  http://www.lkorailroad.com/benchwork-construction-methodology/

Biscuits

   They work fine as long as one knows how to use them correctly. They should only be required to align the top surfaces of the roadbed at the joint, the roadbed should have a support near the biscuit joint( don't put a biscuit joint at the center of a 24 inch span for instance) The sections should be assembled with biscuits on the supports as one works around the curve and not pre-assembled into a long floppy curve section. I pre -cut all the sections, turn them top side down on a work table and cut all the biscuit slots, then assemble each section working around the curve installing biscuits and shooting finish nails into the supports to hold everything in place till the glue dries. The time saving is in the speed of cutting the biscuit slots and using store bought biscuits instead of shop made splines in harder to cut slots..DaveB

Those hangers

I thought I saw them some place before. Thanks Alan.

Bernd

Maintaining the accuracy?

  The key is knowing where the radius points and the tangent points lie so one can relate all the track to them. The curves should all lie tangent to the straights without kinks. Laying out a curve can be done from the centerline or from an offset line( edge of roadbed for instance) If you have 1.5 inch wide roadbed and measure 35.25 to the edge you'll form a 36 inch radius curve as accurately as drawing a centerline on the roadbed and measuring 36 inches.Go out to any construction site and look at the stakes and they will not be down the middle they will be offset along the sides(and you'll see guys swinging in curb forms with a steel tape hooked on their radius point nail).  If you want to use centerline it only needs to be marked on the ends of pre cut sections since they are rigid and can't flex in the middle anyway. The important thing to keep in mind is that accuracy needs to be applied in the places it matters like the curve/tangent relationships and the minimum radius for equipment requirements so don't spend lots of time and effort in places it doesn't matter. If the big picture is designed right for 36 inch radius it won't matter if the flextrack is put down at 36 1/8 or 35 7/8 radius.......DaveB

Those hangers

Those framing clips also come in a wider version for 2X6's that have bendable ends which are handy in spots...DaveB

...

Or here is a radical idea.... work from an accurate blueprint that was created with the necessary considerations incorporated. Oops, forgot there is a widespread aversion to engineering before building in this hobby. < wink> < wink>

a widespread aversion to engineering before building

 Haha, I've never felt there is an aversion to engineering in the hobby? an aversion to wasting time  and resources  is not an aversion to engineering. A fancy accurate drawing won't help if the designer doesn't know how to design a proper layout. I'm a surveyor, I work for civil engineers, I'm just saying focus on the stuff that matters and don't sweat the things that don't. If you want to design an elephant you don't start with his fleas you design the animal and let the fleas take care of themselves...DaveB

Elephant with at least the important fleas

How many times have we read or heard "Just build something"?

The topic of this thread is about finding a use for scraps. It dawned on me plywood scraps may be incredibly trivial when compared to the costs of poor planning. When I read your statement "don't spend lots of time and effort in places it doesn't matter" what immediately came to mind is how does one know what matters and what doesn't unless they have a plan? I'm not referring to model railroad experience, I am talking about construction of any sort. The site stakes you mention are not randomly placed on the fly but rather are the real life manifestation of a site plan. I am of the opinion it is advantageous to spend more time on the site plan than many layout builders do. Just my opinion, nothing more.

How many times have we read or heard "Just build something"?

Sometimes that's all it takes.  How many guys spend weeks or months trying to design a shelf layout where they could buy the track and switches and try out every possible configuration in a couple of hours?    Engineering needs to be appropriate to the job at hand, it's not the finished product it's only the mission.

  The original post was a good way to layout plywood segments and no one will go wrong cutting them that way(although I'm a bit concerned with cutting the notches on a table saw unless they are skilled in it's use?) but they still need to know how to assemble plywood segments into a smooth working layout and that's where discussing various ways to do it can help....DaveB

Reduce the total number of cuts made?

Great idea, but you can not make a single cut that would be both the outside edge of one segment and the inside edge of the next segment! They are not the same radius.

Taken to an extreme, if you are making sub roadbed for double track of 36" and 33 3/4" radius (2 1/4" between track centers) and the overall width of your segment is 5 1/4" (1 1/2" from track center on each side) than your inside edge is a 32 1/4 radius and the outer edge is a 37 1/2" radius. 

Geoff 

can not make a single cut

 Yep, There's always going to be a small slice of ply wasted between the cuts. with a template one can draw the first section then place the template against it to draw the second segment and reduce the waste to the minimal amount. The longer the plywood segments the harder it is to lay out the sheet for less waste but the tradeoff is less joints in the segments.....DaveB