@dlang recommended not using unistrut for bottom beam. what did you use?
Not sure who that was directed to… I used Unistrut for the bottom crossbeam also (the smaller crosssection).
I’ve had a 2x4 “on top” of it, but it stuck out too much… I’m still revisiting that part. I think I’m going to wind up with just a couple of “tabs” that I can move back and forth on the unistrut to support things as needed while hopefully not obstructing the sled (which was the problem with the 2x4).
i was directing to you. sorry wasn’t clear.
dlang was saying that the unistrut on bottom might accidentally
the tabs were for the material to sit on?
does your ply sit on the bottom beam?
Well, I I can see @dlang’s point about cutting it, although with my setup I have the 1/2" or whatever the low profile unistrut “face out” so that the thin edge is up. I have a 3/4" piece of ply as the “backboard” with carriage bolts holding it to the frame which provides most of the strength and rigidity (some cross braces would work also) - and then a spoil board and then the piece I’m cutting… the spoilboard and the workpiece are actually above the plane of the lower strut so, unless I had the bit get way too low, I don’t think I would hit the unistrut.
The 2x4 held things well, but stuck out too far. I had two 90deg unistrut brackets bolted to the bottom crosspiece with the 2x4 screwed (from below) to those brackets. That held things up well, but stuck out too far. I might split it so that it’s more a 2x1 or something (whatever measures right for my spoilboard and all), but playing with it I may just leave the two brackets and let the entire spoil and workpiece rest on it. I will have to watch that I don’t hit the brackets, but with minimal surface area, I think that may be workable…
Still a work in progress
exactly what I ended up doing - works fine.
do you have a photo?
(I recently posted this on the “New Stock Frame” thread but I just found this one - it is much more appropriate here.)
Here is an idea allowing rigid top beam support with easy adjustment to keep the chain aligned for different thicknesses of media. I expect to use the Maslow to cut unconventional materials and want flexibility in the design.
A unistrut P2484 angle support is used to keep the short piece of unistrut rigid. The short piece is oriented with the channel up to allow adjustment for chain alignment in & out. I have also used 1 5/8" strut for the vertical beam supports to compensate for the downward pull of the cantilevered top beam.
The top beam is attached using a carriage bolt, modified square washer and adjustable handle - in this case a Kipp 06601-5A51 but many will work. The washer had to be trimmed to fit inside the unistrut channel The corners are slightly rounded to prevent the washer from catching inside the strut and the hole is squared to hold the carriage bolt from turning. This assembly makes chain spacing relatively painless: the adjustable handle quickly releases the top beam and the square washer smoothly slides in the strut. All bolts are 1/2-13".
I plan to use a 12’ unistrut top beam with the vertical unistrut supports 12" in from the ends to reduce any flex. the top beam will be 2’ above and 2’ to the sides of the 4’x 8’ cutting area. I found 20’ lengths of unistrut at a local plumbing supply and cut it to the 12’ length for the top beam. The extra length is enough for a 7’ vertical support and the horizontal beam support. The design I’m working on has a skirt on all 4 sides to support the sled when cutting near the material edge as well. Obviously this will not fit through your garage door!
Looks very nice… note on your top beam I’m not sure the stock chains will allow for a motor spacing that far apart… Mine is about 10’ and that seems about the limit… of course more chain is pretty easy, but thought I would mention it.
copying (and cleaning up) my comments from the other thread
The potential problem with this is that the chains could hit the supports.
The chain angle at the top is only 10 degrees from horizontal. this is a drop
of just over 2 inches per foot, so at 2 feet, and the need to drop 2 x 1 5/8 +
distance from top beam to the top of the chain, you are actually going to be
getting pretty close (and if you used a 10’ beam so that you only had 1’ or so
to the leg, you would be in trouble)
You aren’t expected to adjust the beam position very frequently, only
when you are changing your workpiece+wasteboard thickness significantly. you
have a 1" or so variation in thickness that you can use in any one setting.
I would flip the unistrut over and have it permanently attached to the top beam,
and the bolts on the brackets get loosened to allow the top beam and support
bars to be moved in and out.
The captured nuts do not slide easily, but since they don’t need to be adjusted
very frequently, that is proabaly not a problem
Yes, going to a 12’ top beam will require about a foot more chain (best to give
yourself a few more inches to make motor measurement easier)
While interference between the arms and the chain is a concern, it might be addressed by putting the 12 foot beam below the arm instead if above it, with the tightener below the beam. Would need to choose a tightener that doesn’t stick out beyond the beam, but that should be possible.
Thanks again David. Good point about chain interference. If there is a problem I may have to move the vertical supports in a few inches. I have found some flex in a 12’ length of strut and want to keep the vertical support as close to the motors as is practical. Downward pressure on the ends can produce a small amount of bowing in the center of the beam. I may even double up the strut across the center between the supports to increase rigidity. I’d rather not add a center beam support. I’ve read what you’ve said about the importance of top beam stability - I agree, it’s probably the most important factor in accuracy. I’d rather overbuild this a bit. (obviously!)
The length of the horizontal beam support struts is just rough cut in the photos. I don’t have my kit yet so I can’t determine the best length.
The nice thing about the adjustable handle is that the handle can be moved out of the way once it is tightened. Probably it would be ok even if it was mounted underneath.
Are you thinking that you’ll adjust that often to make the handle a significant improvement over a socket and wrench? As for the interference issue if you do think that you’ll be adjusting often then why not take a slightly different approach. What would happen if you mount the top beam to the edge of the “extensions” via the bolt holes. That way the relationship with the edge maintains the same then you can make two carage bolt holders like you have for the handle and use the existing nut slots in the 90* brace. that way you slide the whole assembly with out chain issues.
I started a thread -
Please check it out, you may want to condense this there.
that’s another way of saying what I’m talking about
Yes, I expect to make adjustments to the chain often enough to build in the convenience of adjustment handles. When I complete the build I will attach a registration scale to the horizontal beam supports to calibrate the beam adjustment to media thickness.
About chain interference: David Lang suggested something similar attaching the rail to the beam and that is certainly possible. Because of the 12’ beam length and 2’ above the work area I don’t expect interference to be much of an issue. However, I may move the supports in a few inches if it becomes a problem. I want the beam support rail to be as rigid as possible and am reluctant to make it moveable risking flex caused by the chain pull.
I will also be using the same type of adjustment handles on the back supports to change the cutting surface tilt. I’ll post photos of that part when I get it together. What I want in my Maslow is a build quality and versatility similar to better quality woodworking equipment - like the older Delta jointers, shapers, planers, etc…
A better approach is to cut a block of the exact right size and attach it to the
support. The exact right size has top beam abainst the block when the chains
parallel to the bed when there is no wasteboard or workpiece in the machine.
Then you just take a small piece of your wasteboard and material you are cutting
and pinch them betweeen the block and the top rail, and it will be in the
perfect position to cut that workpiece with that thickness wasteboard.
is this clear or do you need a diagram of it?
eliminate measuring wherever you can
are the 1/4" x 2.5" bolts for mounting the motor brackets?
they don’t seem to fit through the brackets that we have.
Good idea to use a piece of the wasteboard and/or cut material instead of measuring each time. I had thought I would put a scale on the adjustment rail with a pointer on the top beam to precisely adjust the chain distance. However using your block idea would be easier.
To apply your idea: I could put a stop on the adjustment rail for the minimum chain distance, then use a block the thickness of the cut material between the stop and rail to set the distance. Yes, I think that would work well.