So I received my kit yesterday. I bought the lumber specified in the assembly instruction which came in the box. I am now reading on the forums that a 12’ top bar with the top of the work surface at 30" below the motors is ideal. What? How does this deviate from the plans in the box? What are the new dimensions for the frame build? I could really use an assist before I start building tomorrow.
Thanks in advance!
I am about at the same stage as you - kit receive, lumber obtained, just waiting on free time to start the build.
I am going to start with a 12’ beam. I won’t quite go 30” above the work surface, but I am trying to fit this under my 7’ garage door. The longer beam will require longer chains. I ordered a 10’ piece of #25 roller chain and links from eBay for around $15.
From what I have read, the longer and higher beam give better accuracy at the bottom corners and top center of the work surface. I don’t want to build a frame and rebuild it later, so starting at 12’.
Also important the beam does not deflect from the weight, so probably best to find a metal beam instead of a 2x4.
There is a very nice spreadsheet with a force calculator that you can experiment with different beam length and position configurations to see what is best. Sorry I don’t have the link, but if you search you will find it quickly.
I won’t be building it into my frame immediately, but setting myself up for phase 2, to add a 6-8” wide skirt around the perimeter of the 4’x8’ work piece, to support the sled when cutting on the entire surface. If this is of interest to you, consider how you would attach it to your frame now.
Thanks for the reply!
I have the spreadsheet downloaded, but to be honest, I have not yet figured it out completely.
I did buy 12’ 2x4’s in order to accommodate a 12’ top beam should I decide to build it.
I am interested in building in a skirt to accommodate cutting a full 4’x’8’ sheet.
I am not sure if anyone has tried it, but simply doubling up 2x4x12 boards might be enough to prevent significant deflection.
doubling the 2x4x12 boards side by side will cut the deflection in half
going to a 2x8x12 will cut the deflection to 1/4 for the same weight (and you
don’t have to go higher, the added width of the board can be below the beam
you can even take a hunk of plywood that’s wider than the 2.5" 2x4 and just
screw/nail/glue it to the back of the top beam to make it more rigid in the wide
center area (not as good as full length, but if you stop the deflection across
the middle 6 ft or so it will not flex as much on the end)
There have been a few people who have built their top beam from plywood, either
laminate a few layers together (the easy way) or by crafting a box (the fancy,
lighter, but harder way)
Now that I think about it, it may be worth checking with your local lumberyard
to see if you can get an I-joist cheap, they will be much lighter than doing it
with solid wood and a 12’ length should be pretty cheap
David Lang