@grim it’s all going to depend how rigid the result is. Some pipe connectors allow a significant amount of flex at the joints
I’m thinking that the sacrificial board can provide additional rigidity to compensate for any movement.
I am planning to screw it down to the tubes.
I modified the onshape doc to put dogholes in the arms to hold the spoilboard (and show dogholes in the spoilboard)
and now I’ve tweaked it so that you can choose between a few different spoilboard sizes (2x4, 5x5, 4x8)
with the anchor dimensions I’m looking at (144x102 with 24" spacing between the rails), putting a 2x4 spoilboard on a frame setup to hold a 4x8 doesn’t work, the spoilboard would fall through the middle.
it takes a long time to calculate things because of the dogholes, so there is a checkbox that can turn them off to speed up the processing.
For another option, I just came across this video for a breakdown grid for working with plywood, including loading arms. I’m guessing it could be modified to work for the Maslow.
Here’s a link to his plans: Handling and Cutting Plywood Plan – Workshop Companion
That dude rocks. I’m going to have to check out some more of his videos.
With the calculators for area vs precision of cut now being more available and them suggesting for full sheets a 4000x3000mm layout. Would you change the design somewhat in response to that? Especially with regards to flex?
Your design is perfect for storage when not in use, and double perfect for my circumstances where I’ll use the Maslow 4 in my garage. Hence the obvious self interest in these questions
for anchors that large, you would need to go with 10’ long boards.
As for flex, testing is needed, I suspect that if you fastened a board perpendicular to the flat side of the arms, it will go a long way towards reducing flex. a 1x board or 1/2" plywood would probably be enough. I would build it and measure the flex. I hope that it’s good enough to reinforce the board outside of the rails, but we would need to test.
see the lite frame calculator I put together at Onshape
With a board/plywood glued perpendicular to the flat side any flex might be at the lap joints or any other connections.
It look as if this is the route I will go so testing will be done
Why? Because the floor in my garage is “non-planar”. There is a grease-pit in the middle and the floor was shaped for drainage into the pit. A vertical frame is not practical due to size and use. Hence the interest in a horizontal collapsible frame.
Rolf wrote:
With a board/plywood glued perpendicular to the flat side any flex might be at the lap joints or any other connections.
yep.
It look as if this is the route I will go so testing will be done
Why? Because the floor in my garage is “non-planar”. There is a grease-pit in the middle and the floor was shaped for drainage into the pit. A vertical frame is not practical due to size and use. Hence the interest in a horizontal collapsible frame.
something to keep in mind, once you have a working system, you could use it to
cut up plywood to make box beams that are both stiffer and lighter than the 2x4s
to use for the arms.
I look forward to your work.
David Lang
Have done something similar before. Scarfed ply, some epoxy and glass. Both “T” beams and box beams for chainsaw milling. T beam is stiff longitudionally, but torsionally not so much. Box beam was demountable and sags in the middle but is easily straightened with a string and a jack. Box beam is 7,5 meters long when the two parts are joined.
If there are other ideas - please share
since we are only talking about ~3n beans, it’s easier, only one joint.
I wouldn’t bother with scarf joints, but I would put a reinforcement plate on
the inside of the beam spanning the joints.
With the maslow cutting things out, you can cut box joint type notches in the
pieces to make them easy to assemble.
I think that fiberglass on the outside is overkill (but now that you bring it
up, I wonder what you could do with foam and poor man’s fiberglass (use either
cloth ot window mesh anchored in place with glue and latex paint). They would be
very light, would they be stiff enough? I think it’s probable.
David Lang
“Everything is a spring” comes to mind. And cross sectional area is king for stiffness of course
Used fiberglass on the outside of the box section in the picture because the jig lives outside in our humid harsh weather (west coast of Norway). Not for additional stiffness. Regular ply does not live long outdoors here unless fiber glassed with epoxy and we wanted that jig to last
The box jig was made with a joint for easy disassembly for storage reasons and transport. Any sag is corrected by the aforementioned string and a jack.
Posted the pictures to jog ideas both in planform and execution for a Maslow for collapsible horizontal frame
Funny, just saw this, I’m looking at using 4 speed horses for a 3.2M x 4M frame
This is a 3300 x 4000 frame of this design (10’ long arms) this is using stanley plastic sawhorses (17.75" spacing between rails)
Well I’m late to the party. @dlang has already been on the case with a number of solves which is great. I’ve been too distracted to focus on the M4 much lately, but these questions have got my wheels turning. Here are a few thoughts I have been mulling on over the weekend:
-
I wasn’t aware of the update to the preferred frame size. Seeing it grow by ~30% on the long axis and ~20% in the short axis is a tough pill for me to take; it’s a true space killer in my little garage. I get the precision gains are better on an overall sheet, but this rules out use in a lot of single car garages. It’s a toss-up for me on whether there is enough value making a larger frame, at least until the weather stays above freeing. However, if you have the room to do this, rock out.
-
I have been looking into the flexibility question of the outriggers as posed by @dlang. I personally am not concerned with flexibility running normal (with/against gravity) for the outriggers. Adding a vertical member to the outriggers will reduce vertical flex there, but there is no force that the M4 is apply in that direction that should effect cut accuracy. This feels like a “more rigid is good” line of thinking.
-
I do agree that the lateral flexure (running in plane with the M4) is effected by the increase in the frame size, which does require one of a few changes. Easiest is increasing the outrigger members profile to 2x6s of quality construction softwood (SPF, Doug-Fir, S Yellow Pine) or an engineered laminated stud.
-
I ran a deflection equation based on a 30 lbs uniform live load (~120 lbs overall per outrigger), which seems to be more that the M4 can pull. Based on the span from the frame rail connection to the M4 pivot point being somewhere around 4’-5", the max deflection you could get would be ~.009". Given the expected tolerance for the M4 is ~.04", I feel good enough about this wiggle room. While I do admit this is a ‘best guess’ exercise and results could be improved w/ better data, but I don’t expect the deflection to exceed the overall tolerance boundary.
-
HOWEVER, if you want to really reduce the odds of flexure you can try turning the outrigger ends into a compression chord of a truss. By using ratchet straps that pass through a M4 attachment point (think eye-bolt attached under the outrigger) and connecting the straps back to the frame rails at equal-ish angles, that outrigger will now have the shear properties of a simple truss w/o the need to add extra members. I am yet to test the concept on my existing frame, but I have used this rigging in construction for temporary bracing of long cantilevered posts. Attached below is a screenshot of the concept; green representing the path of each racket strap.
-
Last, adding greater shear strength could also be achieved with a bigger outrigger member, a box beam member or shear plates / panels as discussed in the thread. It’s worth noting that many of these concepts are at odds the initial purpose of this design: to make a frame as minimal as possible so it can be assembled, disassembled and moved easily. Granted, everyone has different needs and priorities. Mine just require these somewhat restrictive constraints. I’m interested to see what you all come up with your own constraints and priorities.
Aloha,
I am looking at using my M4 to cut box beams for my next frame iteration; my goal is to have a frame that can be disassembled into pieces that (except for spoilboard) will fit in my Ford Fiesta and easily assembled on-site wherever that may be.
I don’t have time at the moment to design it—I’m working on design requirements for a project at the moment—but when I’m burned out on that, I explore ideas.
What I’m hoping to accomplish:
- excellent rigidity
- portability and compact storage
- ideal anchor spacing for edge-to-edge cutting of a 4’x8’ sheet of plywood
I’m sure that, as always, I’ll learn a lot along the way.