Is it true that there is an optimum ratio between width and hight of the frame?

it’s worse than that, the sled can’t get close to the edge of the triangle as the angle between the chains gets too wide

If the distance between A and C is 7.5’ (equilateral triangle 6.5’ tall, just short enough to fit through doors), keeping a similar angle to what the maslow is limited to now (140 degrees between chains IIRC) have to stay at least 16" away from the sides.

I you could get to 150 degrees that lets you get down to 1’ away from the edges and lets you pull the sled almost all the way to the motors.

no, chain sag isn’t going to change with the direction. It doesn’t really matter the orientation, when you start moving away from being directly under C it’s now working at an angle and starts to run into limits

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Your thinking much faster than me. That is probably a good thing. It dawns on me my thought process in this is based in sailing rigging. I think yours is much more math.

I like the cut of your jib.


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@Brandon, a lot of it is that I’ve fielded the same or similar questions before

There have been a lot of people who post quick “if they did this it would be
better”, but there are only a few ideas that hold up to being explored in depth.

We’ve all agreed that a triangulation approach would help, but we didn’t have a
reasonable way to implement it until the ‘throwing my hat in the ring’ thread
and the ring and linkage approaches. Those are SO much better that I really hope
that the 3rd batch of kits ships with one of them instead of the stock design.

I think the top-beam frame approach is another significant change, but I suspect
that we have had so many other accuracy problems that the flexing of the machine
hasn’t been the biggest source of error for anyone yet.

David Lang


Building on your diagram, instead of a third motor, take each of the lower two lines all the way across the bottom and up to a multi-purchase pulley system working against the chain take-up sprocket on that side. That way for instance when the left motor feeds out chain and winds in on its take-up sprocket, the tackle attached to that sprocket pulls in on the right lower cable. Inserting a stretchy link into that line, maybe at the router end, would provide the actual tension, the tackle provides adjustment of that tension relative to the chain length and the router’s position. It might take some playing around to decide how much purchase the tackle needs; the sprocket moves one inch for every two inches of chain movement, so using a gun tackle arrangement would move double that half inch so that the tension cable would move one inch for each inch the chain moved. That may or may not be the right amount, it would depend on the tension of the stretch link.
I know, Rube Goldberg would be jealous.

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The problem that you have is that lengthening the chain on one corner does not
mean that the line on the opposite corner needs to be shortened by the same

adding a multiplier in the mix makes it even messier.

David Lang

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That’s true. That’s what the stretch link is about. The multiplier and the stretch link would have to be chosen to provide benefit where needed and not get in the way when not. It’s a crude analog computer, if you like :smile:

I love your use of language, that makes total sense to me. Me and Rube go back,lol. I’ve been called a Peppertree Mechanic.


I’m green here. My kit arrived Monday same day as the router. I have made enough room in the garage to store the Maslow but not operate it. I’ll have to set it up in the driveway for that. I have gotten everything together and cut to length. It’s tough sitting on the sideline until Monday. That is when the bit I ordered will arrive. I will get the final frame together, then a week or two later the Linkage kit should arrive. My aspirations are simple. When I got the Shapeoko 3 my intent was to make chairs out of 15 x 15 inch cut frames. With the Maslow I hope to do 7Ft tall lettering. I have some furniture and cabinet ideas. I am having ideas of cabinetry based on puzzle boxes. I also plan to make big numbers 20 ft tall, for an electronic scoreboard. Has anyone suggested improving the working area by adding a deck around the outside edges so the sled can go to the full 4x8 ? I’m dying to get practical experience. Once I have the basic build done I will look at frame alternatives.

One other topic - if it’s already touched on please tell me but I really want to make a panel saw add on accessory for my Maslow.

As always I appreciate everyones efforts here. I’m glad to be one of the community.

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the headache is that the proper length depends on the position of the other top

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It looks like the proper multiplier will increase the tension of the longer of the two chains more than that of the shorter. In a bottom corner, that would help pull the sag out of that long chain while the tension from the other bottom corner will be proportionally less. Not talking about hard links here, just proportional adjustment to tension.

It looks like your kit is scheduled to ship on Friday! (if you are who I think you are :slight_smile: )

This thread discusses panel saws (among many other cool things).

Much Thanks to you - Have a great weekend.

And I did (feeling a bit stupid now)
None of this is claimed to be true. Just some random outcome of spending time being wasted, without the feeling of wasting time.

No 1 is the guy that bought a lighthouse and the Maslow. He thought:
‘The wider and higher the better? I don’t have width, but height! My frame will have the ratio 1:1.’
He ended up with a frame 3.65 m (~11.98 ft) in hight and width to fit his plywood in the ‘comfort zone’ of the py script. (Yes, he could have built a slightly smaller frame by moving his sheet up to the top curve, but he would have to climb a long ladder for tool change.)
No 2 is the guy that bought a barn and the Maslow. Sadly, whoever build it placed the 1st floor very low, to make it easy to throw up the hay. He thought:
‘The wider and higher the better? I don’t have height but width! My frame will have the ratio 4:1.’
He ended up with a frame 7.63 M (~25.03) wide and 1.975 m (~6.48 ft) high, to make his sheet fit in the white.
No 3 is someone I know and the guy feeling silly.

Suddenly the numbers 1220x2440 and 4x8 started flashing up in his Prefrontal Cortex, together with a ratio of 1:2. The ratio of a ply-sheet.
This guy will never be able to hire a Housemaid, because the Maid-Room is the Maslow room now.
Since the space requirement for Human Labour here is slightly unfair, compared to what Animal Rights recommend for chicken, he neither had width or hight to waste. He figured that the smallest frame for him to build would be 3,125 m wide (~10.25 ft) and 1,562.5 m (~5.13 ft) high.
Anything bigger then that, at a ratio of 1:2 and centring the sheet to an equal distance from the curves could add accuracy.

I think I am done with my research for building the second and hopefully final frame.
Thank you all for the constructive feedback and always the pleasant collaboration.
Cheers, Gero


I have a Dream - I’m just getting started so I’m probably way off and behind the curve. Assuming a standard round sled at 18 inches. My goal is to able to go edge to edge on a standard sheet, this would require a outer bezel of ~10 inches and the ability to adjust the z depth of the 10 inch tall / wide waste board. This would allow the sled to go fully off the edge of the sheet and still be supported.

Any thoughts on this?


Yup, in the picture, the orange is a frame (half the width of the sled) around the sheet (brown). The light orange is my sled at the corners. I plan to have that frame exchangable in the 2 or 3 thicknesses of material I will cut. Exactly for the reason of being able to cut cut from corner to corner without the sled starting tiling. I have seen already pictures here of the same thing being done.


so 8ft +20 inches + 4 ft + 20 inches

9 ft 8 inches X 5 ft 8 inches for a base dimension

104 inches x 56 inches

or 2641.6 mm x 1422.4 mm

you don’t need that much support 2-3 inches around the workpiece is probably
enough. You just need enough to keep the sled from getting ‘tippy’


This is the same plan that I have, but I have figured that I can get away with a 6" outer edge (this is dictated by a 4" rim of 1/4" UHMW I have planned under my 18" steel sled, all of which is still in design phase) with the idea that if 1" of the rim is still on the edge board, having 3" of the circular sled hanging over, there should be no tilting issues since a great majority of the sled would still be supported. Initially I had planned on 9 inches so that the sled would be fully supported, but then realized that the extra three inches supports only a small chord of the circle.

Reading I I see that David @dlang has indicated that only 2-3 inches is necessary, so if you have a flat sled bottom, I would follow his advice. For my design, I am still going to need the 6" (I could probably get away with 5" but I’d rather have the wiggle room to prevent the possibility of the UHMW catching)

Glad I found this thread. I’ve been having the same thoughts and just asked about availability of co trolling another motor. I was thinking two at first with bingos to reduce accuracy requirements, but it could even be done with one. Circular loop of chain at the bottom with a single point that is moved back and forth that attaches up to the bottom of the sled and is directed to be at the division of the other two angles.

If uniform pull is desired it could be done with a weight and pulleys. Sled weight could be reduced then, and cutting speed probably increased. I think two motors would be easier and more effective though.

Just initial thoughts…

Has this link been posted? Its a good one with a lot of info on this design machine

and a quick pic for attention :slight_smile:

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yep, our simulation code started out from there.

David Lang