This also leaves more of the motor cable available to ease choosing the location for the controller - on a 10ā wide frame that becomes a consideration.
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Some simple thoughts:
- most people (everyone?) will put the Maslow against a wall, so why bother with supports on the ground ? Just the 2 vertical beams extending above the frame, leaning against the wall, provide the best leveling and support. The angle can be changed anytime and sheets can be stored behind it. It doesnāt require cnc cut parts.
- when working with flexible materials, structural integrity and stiffness are achieved by crossing and layering. A grid of beams (less large than 2x4) achieves that. It makes the plywood sheet obsolete (any sheet will do as cutting protection), it also allows for frames of any size. No particular construction angles are required.
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@madgrizzle the verticals could be two 2x4 ll sistered. as @dlang points out their current orientation is their weakest. Your whole frame could easily be strengthened by rotation of the vertical elements. The bottom gussets on the A frame should be replaced by rotating and extending the internal 2x4 (base ones) to the outside ends of the vertical 2x4ās with four screws.
Timber sizes in the UK.
We have wood marketed as CLS (semi planed with eased edges) which are 38 mm x 63 mm (2x3) and 38 mm x 89 mm (2x4) (i.e standard US Sizes) as well as 47mm by 50mm or 100mm (i.e real 2x4) rough sawn. Lengths are 2.4m (94.48"), 3.6m (141.73") and 4.8m (188.96"). Our DIY Stores tend to carry the shorter lengths but the longer are readily available from timber merchants.
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Thank you - that helps me a lot to know.
@Borderline, @dlang, thanks for the constructive criticism 
. When I read the responses as I was going to sleep, I thought the concern was over the top beamās orientation but after rereading this morning, it seems the concern is just on the A-frame supports. I think I understand your comments and stealing from @dlangās design, I propose something like this:
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is there any reason the chain tensioner arm and/or the material support tabs couldnāt be replaced with say, 3/8" allthread/bolts through threaded inserts.?
Based on the other frame design threads, I know thereās a lot of thought around being able to fine tune and level the plane of the chain/sled. Eye bolts would let you adjust the front/back distance of the chain tensioner hook. And replacing the bottom material supports with bolts through from the back (that change would need to factor in solid frame materiel just below the projected cutting area) would let you adjust the support stick-out for material thickness. Ideally you could crank the bolts out/in to just below the material top surface, and then never need to worry about sled clearance on the bottom edge. Also, then you could install multiple support threaded inserts, at say 1ā intervals, and move the bolts around based on material width, or add more based on material weight. The only downside is for the supports, youād need to drill the holes in a pretty straight line, and relatively square.
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I adjusted the position of the motors as @dlang suggested. I was a bit concerned that the lag bolts I propose to use to secure the motor mount to the top beam might interfere with the chain (really didnāt want to recess them) but I think the sprocket/chain is out far enough to clear it. Hereās an update of the front view.
edit: I forgot to turn the legs on their side in the post. Now, I propose to use lag screws to secure the top beam to the legs since Iāve got more meat in the leg. I also rotated the top stiffener for the plywood as now Iām proposing to screw into it through the legs.
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Itās starting to look a lot like @dlangās design, but they have a couple key differences.
First, my legs are further apart. I did this to give structure along the edge of the backboard so that it minimizes its potential to warp or curl. Is this a good idea?
Second, my design builds motor mountās out of spacerās while @dlangās design moves the top beam out using spacers. Both accomplish the same thing, just different waysā¦ which is better or is it a matter of taste?
Third, @dlangās design has a few more bracesā¦ are they all needed?
Finally, I havenāt incorporated a spot for the electronics yetā¦ was waiting to figure out the structure first.
P.S., Iād like to figure out how to terminate the slack end of the chain so that we can keep it in-line with the sprocket as well. I donāt know if @dlang has that worked out in his design either.
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With sheet goods storage in between
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I think itās a trade-off of how much 2x4 material you need.
I built my alternate 2 frame based on buying 10ā 2x4s and using the entire length. It uses a total of 6 of them (with a few feet left over on the last one). your design would require buying 12ā or longer 2x4s and/or would have a lot of leftover lumber and buying more of them
putting the motors out on spacers means that there are more joints that can flex, and the motors now have a much longer lever arm to bow the beam (less than an inch out from the edge of the beam normally, about 6-8" if you space things out)
I donāt trust driving fasteners into end grain (been there done that), so I put a small block at each joint where a two boards meet at 90 degrees.
I also built it so that the top and bottom beams can be removed without the frame falling apart.
Part of this is the desire to make the top beam adjustable.
Part of it is the desire to be able to remove the bottom beam when it gets too damaged from the router (we are talking new CAD users, they are going to make programming mistakes that will end up running the router where it shouldnāt go (and sometimes you want to cut off the edge, and accept the damage to the support)
and part of it is the desire to be able to detach the extra long pieces for moving/storing the machine
I figure the underside of the top of the frame is a great place to put it
thatās what these spacers on the bottom are for (although take a look at the post I made a couple days ago about a circular chain take up approach that would let us shorten the bottom beam to match the plywood)
if you mount the motors on the outside of the bracket then you would definitely clear the bolt heads. This would introduce a larger moment arm on whatever fasteners were used to secure the bracket to the frame, but I think that 4 screws in each bracket should be able to deal with that.
As a picture usually helps:
I have since made a small plate for mine (the picture is @mrfuguās) to hold the loose end of the chain in the same (ish) plane as the sprocket. I will try to edit this post with a picture of mine tonight.
**Edit: here it is, though hard to see:
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unless it canāt clear the bolt, I would put the motors on the inside, itās not just moving on the bolts, itās the long-term effects of flexing the entire beam.
I may be overreacting to the existing problems, but where possible, I like to minimize the potential for future problems at the design stage
are you worried that the additional moment arm on the bracket would twist the top beam?
the difference in flex should be negligible since the sprocket ends up at the same offset from the beam, but being on the outside of the bracket would certainly introduce a twist. From what I have seen it is not an issue for the unistrut, but I could see it being a concern with a single 2x4, especially with the 2x4 oriented as it is with the strong axis perpendicular to the motor offset, but I think that either way you will end up with a similar moment arm applied to the top beam since the force is applied at the sprocket and the sprocket should be located in the same place in either case. The difference being that you could eliminate some of the forward distance of the wood to support the motor mounts (in @madgrizzleās design that looks like you could take out one of the 2x4 blocks, see below) but the end result is the sprocket at exactly the same place.
Though my design looks to scale, I wasnāt really focused on dimensions nor how the lumber gets cut. I donāt like any lumber over10-foot so Iād have to look at that. But my question is whether or not there is any concern about warpage along the edge (i.e., bowing or bending when looking down from above)? My backboard has a bit of a bend in it and Iāve applied some extra braces to try to straight then thing outā¦ still not perfect.
To make sure Iām clear, this is what Iām trying to avoid (and I exaggerated the twist in the top so itās easier to see). Iām just asking if this is likely or not in your design. The bottom brace my resolve it. I donāt know.
I assume this is what you are describing? If so, this is what I initially thought your concern was last night.
madgrizzle:
Same here, I only added one for the top plywood stiffener just to add some strength (my original design didnāt have any connectionā¦ that piece was there just to flatten out the plywood).
Got itā¦ makes sense in that way that you need more horizontal pieces.
Seems reasonable.
I donāt see the spacers on the bottom of the top beamā¦ maybe talking past each other. Iām referring to the end of the chain that, in the current stock design, passes through the motor mount plate and is secured by the cotter pin. Are you talking about the same thing?
No, if the motor is outside it is the thickness of the motor further out from the beam.
Yes, but if you move the mount closer to the beam, then the sprocket stays in the same place. Thatās why you can remove a part of the blocking in @madgrizzleās design as I tried to show above
Some of this has to do with selecting reasonable lumber to start with. I think that with reasonable lumber a foot unsupported should be ok. The original dedign was completely unsupported (except the bottom rail) both of our designs provide a LOT more support
Yes
No I wasnāt. I was talking about the connection to the bottom beam.
Zip tie the chain end to a lag bolt
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How do you move the mount closer to the beam? Itās the same thickness as the beam
In @madgrizzleās design there is a piece of 2x4 that is mounted to the beam with bolts.
It was clearing these bolt heads that was the reason I suggested mounting to the outside of the bracket. As I look at the design, it appears that there is just one block of 2x4 attached to the beam, which would then mean that if you removed that block you could attach the mount directly to the beam. Given that the sprocket needs to be in the plane of the balance point of the sled, leaving the block in and mounting the motor to the outside of the frame would both clear the bolt heads and move the sprocket closer to the balance point of the sled.