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I noticed that Lionel added a new 3" Fastrack straight section in the 2023 catalog (page 219). As someone who's created plenty of track plans with Fastrack, including my own layout, I was curious to see how many new lengths were possible with the 3" section.

It turns out this is a version of the "Subset Sum" problem. After some research and writing some code to use an existing subsetsum Python library, I can now answer that question!

Note: I know that cutting Fastrack to make custom lengths is possible and has been done. There are posts on this forum about it. I'm not considering that here as I expect many of us (myself included) don't want to cut up our relatively expensive Fastrack sections. No need to comment and suggest that as an option

The following lengths that were previously impossible to create can now be created using the 3" straight section:

fastrack_formulas_new_with_3in

Additionally, some of the lengths that could already be created without the 3" section now use fewer sections when the 3" section is involved - one example is a 7 1/2" length, which would have required 4x 1 3/4" sections before, but can now be created with 1x 4 1/2" section and 1x 3" section. Here's an updated "Fastrack Formulas" table which includes the new 3" section.

fastrack_formulas_consolidated

PDFs for both of these images, as well as the full table which includes the lengths still not possible, are attached. Happy track planning!

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@PRR1950 posted:

Now, someone has to inform all the track planning program developers!!  But I think they may have to wait for exact measurements when the product hits the shelves.

Chuck

I requested the update for RailModeller Pro (my primary track planning software) and AnyRail already!

http://forum.railmodeller.com/viewtopic.php?t=4542

https://www.anyrail.com/forum_...hp/topic,3973.0.html

I don't have an account on the SCARM forum, so I'll let somebody else put in that request. Feel free to use one of the above as reference as it includes the link to the online catalog, page number, and the part # for the new section.

@PRR1950 posted:

Now, someone has to inform all the track planning program developers!!  But I think they may have to wait for exact measurements when the product hits the shelves.

Chuck

I would think they could take the model for an existing straight section, copy it, and adjust the length to 3". I don't imagine any of the other parameters (width, height, etc) will be changing for this new section.

For those of you who use SCARM and would like a handy work-around for the new 3 inch piece, in the attached SCARM file there is a 3.00 inch piece of FT that has been precisely "Snipped-off" from a 4.5 inch piece.  You're welcome to cut and paste it from the attached file into your SCARM project if you want to use the new piece in your design(s) before the next update is released.

3 Inch Fastrack- cut from 4.5

Note; if you generate a Parts List using this work-around piece it will show up as follows:

Part List_3 Inch Fastrack- cut from 4.5

Attachments

@Mike0289 posted:

I requested the update for RailModeller Pro (my primary track planning software) and AnyRail already!

http://forum.railmodeller.com/viewtopic.php?t=4542

https://www.anyrail.com/forum_...hp/topic,3973.0.html

Quick update - the next versions of Anyrail and RailModeller Pro should have the new section!

https://www.anyrail.com/forum_...hp/topic,3973.0.html

https://railmodeller.uservoice...k-3-straight-section

Now I am really curious.  Lionel had the opportunity to put a lot of thought into the Fastrack lengths that they came up with and it appears that they did put a lot of thought into it.  I imagine that they created their own fit charts before producing Fastrack and then locked most of them up to give modelers the fun of figuring out how to use Fastrack.  Now I wonder if this 3" section was planned from the very beginning and designated as a "secret weapon" that they could launch in whatever year they chose to generate sales and renew interest in the system.

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