It should be possible to setup a test for this. put a bolt in any sort of
anchor, put the sled in a fixed position (or even have an anchor on the other
side), extend the belt to the anchor, measure, re-rig the belt end with the
extension (which needs to be solid enough to not flex under load) and retract
the belt until it’s tight and record the difference.
David Lang
Received 8 ft fiberglass ladders via Walmart for $108 each. I like the ladders. Previously bought emt conduit for another idea. I figure attach conduit to back side of front section of ladder with cunch velcro straps. Usinf 4 total on front. It is about 3 1/8" from bacl of front section to front of leg. Plan on torsion boxes that can be unstalled on conduit. Instead of entire 4x8 ft torsion box. I am thinking 4 boxes 2 ft by 3 ft. With the sled able to travel 2ft 7in on 3 ft leg. Plan to have track in 5 inch area for cla.ps to edge where needed in case of loss of vacuum. Fuguring .5 inch underlayment should be ok for disposable underboard. So these boxes will sit up and down on each side. Think 0.5 in underlayment at 65 degrees should.not sag much but bracing could be added if eeded. I am new to this. Comment welcome.
Can we get a closeup pic of the end of a belt as that will influence the design of the frames I expect. If it’s a flat plate with a hole for a pin then would be good to understand the geometry so frames can be planned in advance.
it’s more like a tube that the belt wraps around, with a bolt going through the
tube into the frame (based on the little that I’ve been able to see from the
pictures).
that seems logical to me, easier to attach to the belt, stronger than a flat
plate that would need to sit at right angles to the belt, and a larger surface
area against the bolt (less wear over time). The tube is also an easy thing to
handle when retracted against the sled.
David Lang
Looks about 8mm ID on the hole @bar …?
Now rethinking the attachment but have some ideas !
It’s a 10mm hole because 10mm is close to 3/8th inch, but we will probably offer a couple different sizes because I can imagine that for different frame designs something different might be ideal. They don’t have to be this shape either so we could offer some different designs if that’s something that’s useful.
EU/UK based means 10mm is perfect as it’s off the shelf for bolts and pins etc
yep, 10mm and 3/8 are both common and the differnce between them isn’t going to
matter for this sort of use case.
David Lang
An alternative to knowing the carabiner size precisely would be to select a range of extra length to get in the ballpark, then precalibrate by touching off on a circle of known size. Perhaps a circuit board taped to the spoilboard could be the precise circle. A 555 circuit and 2032 battery on the circuit board produce a signal that goes away when the touch probe leaves the circle.
The touch probe could be a length of straight wire, or standard pogo pin inserted into a router collet.
While eagerly waiting for my Maslow4 
(I am part of batch #3), I want to start designing a frame out of 39x89mm SLS (equivalent to 2x4”, I guess). To save space, I want it to be as vertical as possible.
I started thinking about the effect of the angle on downforce. Can anybody help with guesstimates?
How much downforce is needed to keep the sled on the workpiece and to drive the bit into the material, 2-3kg?
Contributing factors are:
For pure horizontal 100% of gravity = downforce, for pure vertical, 0%. 10deg~17%, 15deg~26%, 20deg ~34%, …
What will be the weight of the sled incl all parts as delivered? 4kg?
I found 1,9kg for the dewalt router but guess that includes the plunge base. So 1,5kg without?
Total 5,5kg would give 1,4kg downforce for a 15deg angle. Not enough, I guess.
Belt tension helps when the belts are angled down towards the anchors.
In the middle of the workspace, each belt is about 7’ long, assuming 12x8’ between anchors (8x4’ + 24” in each direction ~ 14’ diagonal).
Assuming anchors at level of the spoiler board, I estimate the spools are on average 4” higher. That gives an average angle of 2,7deg meaning just under 5% of belt tension contributes to the downforce.
What is a good estimate for belt tension? I think I read max 30lbs ~ 14kg.
Assuming an average of 10lbs~2,5kg, downforce for all 4 belts would be 0,5kg.
I realize that reality is (much) more complex: each spool is on a different height, gravity results in higher tension in the upper belts, tension changes with sled position, … but want to get a feel for numbers.
My conclusion so far is that, unless some of my estimates are off, the contribution of belt tension is about the same as what I can get from additional 5deg angle.
Will the spools be happy with out of plane forces? If not, I’d rather keep belts parallel to the work surface and live with a larger angle and footprint.
I’d rather not count on suction force.
Comments are appreciated!
Will share my design (will use Fusion360) when I get somewhere.
This is a very well researched and thought out post.
Answering these kinds of questions for Maslow4 is hard, because the answer is usually a continuum instead of black and white. I would recommend at least 15 degrees on the frame angle…but if your space only allows for 14 degrees will it still work? Yes.
You have done a fantastic job of pulling information from all different places. 14kg is the amount of tension introduced by the motors, but in the top center of the frame, the force of gravity pulling down on the router will be much higher than that. Think of 14kg as the tension on the lower belts where gravity is not a factor.
This lines up nicely with my experience in practice. I think that your estimates are very good. I’d say it could contribute maybe even up to 10 degrees. It’s also a different sort of constraint because if the sled tries to move away from the wood the belts won’t let it so the force goes up. IE on the original Maslow where we were using gravity instead of the lower belts it was physically possible to lift the entire machine away from the wood while it was cutting, but with four belts that is not possible because the belts will hold it down to the surface.
Yes, the angle isn’t an issue for the spools unless you want to cut really close to the anchor points. Keeping everything in plane would let you make the frame smaller in X and Y at the cost of more angle needed to keep the sled pressed against the wood.
I think you have very good intuition. This comes up a lot, but I don’t think suction is a factor at all, at least as the sled is designed now. Picking it up off the surface with the vacuum on or off doesn’t feel any different. I’m sure that we could design a sled which used a lot of suction to hold down, but then we would have issues with some dust collectors being too powerful and other not powerful enough. In my mind the vacuum is there to remove the sawdust and that’s it.
Thanks, @bar !
I know and don’t expect you to tell us it should be 15,256 deg. I just want to get a feeling for the factors that play before I start designing.
Right, so 14kg in each belt is more the mimimum we can count on to generate downforce on the sled.
Good point, my bad, I didn’t consider the fact that it is a controlled system (which is kind of the whole point of Maslow 4, I guess 
) that will actively try to keep its position.
I couldn’t agree more.
Besides, the requirements for both functions (downforce and dust extraction) are opposite.
For high downforce, you need a strong vacuum (sealed pressure) sucking the sled against the workpiece which means low airflow.
For good dust extraction, you want to maximize air flow to carry the chips.
Anyway, looks like 15 deg with angled belts is a good starting point. Will see where I end up and whether compromises are needed wrt available space.
It seems like you have really good intuition for how it all works, and I am excited to see your frame design. Now that we have removed all of the robot stuff off of the frame and onto the sled I think that we are going to see some really interesting and novel frame ideas. The scope of possible solutions is pretty large.
After seeing maslow4 run horizontally with good results. At my age bending over is difficult. Disliked my older plastic folding sawhorses anywatm so found some heavy duty ones and ordered a pIr called WorkPro. They are heavy duty. Has brackets on each side for 2x boards. Thinking of 4x8 sheathing base covered with .5" styrofoam as waste material the routing material on top. Maybe a boarder of plywood or 1x to hold board in place. Still working on 2ft extentions for the corners.
one possible approach that I drafted up
take 2x 10-12’ long 2x4s, put a wasteboard on them, then get a pair of 2’
interior doors to go on the sides (looking like a wide H). This is just under
the 2’ vertical spacing but is lightweight and very stiff.
David Lang
I like your approach somewhat. But something else I want to incorporate. A piece of aluminum flush with work surface just to the side of work surface for calibration.
I have also considered it being like 6 inches long so that bit could touch one end with the other side making electrical contact with metal in router for calibration. So it could move into position and test without having to hook up electrodes.
It would be awesome if you guys could do some documentation on them (some photos, a list of parts used…etc). I will have instructions and documentation for more than one frame option, but Maslow4 is so versatile that I think we will want to create a space to share a whole bunch of different frame options because the best option for one person might not be the best option for someone else…for example wanting a horizontal frame, but not wanting to bend over (my back is young and even I don’t love bending over all the time…so I think many people will be interested in this).
As soon as I have something to share, I will.
When not in use, my Maslow needs to go where I currently have my stock of raw sheet material. I am planning a cart with the Maslow4 frame on one side and storage for sheet material on the other to solve this catch22.
So, it will be a relatively specific design but might nevertheless be useful as inspiration for others.
