Thanks for the link … it is a different alternate frame than the one I was going to build. Some great ideas in your design.
This is way out of left field, so forgive me. If the goal is to make a stiff frame, what about using a Harbor Freight or Northern Tool 4x8 steel utility trailer kit? I have never owned one personally, but I know people modify and use them to build teardrop trailers frequently, that they are cheap and often on sale ($200-300), that they bolt together (for people who can’t weld), and that harbor freight will ship them to your door (at least in the U.S.). If you assemble the trailer sans the axel and use the two tongue/hitch pieces for the “motor arms” (some reconfiguring would obviously be necessary) it might be a great frame. The frame is a U shaped steel, and with a piece of 3/4 plywood bolted to the front I imagine it would be very stiff. You might even be able to resell the axel and wheels to make some of the money spent to purchase the trailer back!
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I love the Idea! Are they available in 6x12? Tires make good planting rigs and the rims to keep hoses tidy. It adds a couple of bucks, if you buy it new though. If you want a wall hinged version like me, it adds plenty of weight.
But for future upgrade to plasma cutting, still highly interesting.
I really like that idea (plus it reminds me I need a new trailer, but that’s another story :-))
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that could work, but you are putting a lot of strength where it’s not really
needed. The main thing you need strength for is to keep the motors in the same
position relative to each other. The rest of the fram just needs to support
itself and the workpiece, but it’s not under any particular stress when cutting.
but the motors apply a lot of force against each other, and if they (or the
frame between them) flex, your position is wrong.
Hey, leave the wheels/axle on the back and you’ve got the ultimate portable Maslow 
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I have been looking at your 2 alternative designs look very good and straight forward. Has anyone made one of these yet? would love to see pictures. (dont have my kit yet but wanting to build the frame before it gets here to be up and running quicker.)
Also you mentioned moving the top beam in and out depending on thickness of materials to keep the chains aligned correctly. Any solution to make this easy? would this be needed for the differences in your typical plywood thicknesses say between 1/4 and 1 inch?
I have been looking at your 2 alternative designs look very good and straight
forward. Has anyone made one of these yet? would love to see pictures. (dont
have my kit yet but wanting to build the frame before it gets here to be up
and running quicker.)
I don’t know of anyone who has followed my plans exactly, but the various
unistrut designs are the same basic idea
Also you mentioned moving the top beam in and out depending on thickness of
materials to keep the chains aligned correctly. Any solution to make this
easy? would this be needed for the differences in your typical plywood
thicknesses say between 1/4 and 1 inch?
1/4" to 1" is probably around the max you can get away with without having to
adjust.
If you make brackets that are at a right angle to the front of the frame, you
can slide the beam in and out on those brackets.
build your sled and find the balance for it. Position the beam so that with the
sled balanced and nothing on the machine (no wasteboard, no workpiece), the
chains are parallel to the frame.
mount some blocks (or a piece of 2x4) across the brackets touching the back of
the beam.
Now, when you go to cut something, slide the beam forward, get a small chunk of
wood the thickness of your workpice (and one for the wasteboard) and pinch this
between the top beamand the blocks.
now the beam is perfectly positioned for your work.
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This may have been asked elsewhere but I cannot find two dimensions that I need to better understand the alternative frame construction:
- Could I get the distance from the bottom of the frame to the bottom of the 4x8 work surface?
- I also need the dimension from the bottom of the frame to the bottom of the cross support holding the motors.
Thanks
Kirk
The width is about 3000 mm The actual motor distance is 2998 mm on the stock design
And the height is 2200 mm(?) not 100% sure.
In the github wiki this is documented somewhere. I’ll try to look it up.
This may have been asked elsewhere but I cannot find two dimensions that I need to better understand the alternative frame construction:
- Could I get the distance from the bottom of the frame to the bottom of the 4x8 work surface?
not a critical dimension, but if you use a standard 18" diameter sled, it should
be at least 9"
- I also need the dimension from the bottom of the frame to the bottom of the cross support holding the motors.
what actually matters here is the distance up to the center of the motor shaft.
This needs to be at least 12" (for the stock motors to pull the stock sled up
to the top of the work area), but I believe the stock frame is closer to 18"
In the alternate design, I used 66" 2x4s for the vertical elements, with 4"
wheels below the frame (5" tall), then a 2x4 (1.5"), then a 2x4 on edge
(3.5")=10"
It would probably be good to drop this 1/2" to 1" to give the bottom rail
support across the full width of the frame, and going ith 5" wheels would give
you the same total clearance. I think I’ll tweak the CAD to use 5" wheels and
have the bottom beam flush with the bottom 2x4
66" - 3.5" - 48" = 14.5" (16" after the change I mention above) from the top of
the 4x8 plywood to the bottom of the top rail.
When I tweaked the design to show the unistrut beam, it lowered the beam by
1.5", but I really don’t think that will be a problem.
does this answer your questions?
This is determined by the distance from the router bit to the bottom of the bricks attached to the sled. Leave enough room so that when the bit is at the bottom edge of the workarea, the bricks do not hit the floor 
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