there’s a version of this tweaked a bit to be more useful to us at
http://lang.hm/maslow/v-plotter.py
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this thread (or at least links to the spreadsheet) should probably be made sticky somewhere.
also, is there a strong desire to have a metric version of this?
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From my single person point of view the desire is strong in me.
I made a copy and played around with sheet converting my numbers, but it is a hassle.
The current sheet has like several tables that could use an explaining header.
Am I correct to assume that the relevant table is the top left one to play with (A-I / 1-18)?
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I added some colors to highlight different areas (green for the areas you are expected to edit, blue for the results, yellow for the diff between the two versions)
does this make it clearer?
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I also added a line of explanation at the top.
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Oh wow! Thank you David! It’s like a lightbulb lit over the head now. 
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thanks for pointing out the problem, I was too close to it to see it.
unfortunantly we don’t know where the limits really are (the stall torque of the
motors is 20kg/cm, but their running torque is a bit lower, but how much
lower…)
But if anyone can put in the parameters for a machine config that is known to be
a problem along the top, and see what the calculated peak tension is, we can
note that (and possible turn things bright red if they exceed the known limit)
Perhaps overly simplified but I had played around with v-plot script on the http://2e5.com/plotter/V/design/ site and generated the PNG plot file. I then inserted the .png file as a canvas into Fusion 360 and did a calibration to the size of my current machine, this is a trick you can use to be able to sketch on top of a photograph at scale!
My first attempt was done at my current machine dimensions at 10 ft top bar and sketched in a 4’ x 8’ board on top of the canvas. The problem areas are close to what I have experienced.
Orange: poor resolution
- Light Blue: too little tension in one of the lines
- Dark Blue: too much tension in one of the lines (and poor resolution)
- White: drawing area candidate
On my second drawing I set the calibration to 12 ft between the marks, and then overlayed the 4’ x 8’ on top, and it seems to fit inside the constraints.
@dlang as you mention this does not take things like torque, friction into account, but this helped me visualize the problem.
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I could not witness a stall of the motors with my last setup. The 2 of them together will lift me.
Made good progress with the standard kit parts switching to bottom feed and will connect amp meter to main power supply soon.
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take a look at http://lang.hm/maslow/v-plotter.py this took that script and
updated it to have variables to support representing the maslow and let you
experiment with different sizes
yes, it helps to visualize the problem. unfortunantly we don’t know where the
limits (too much, too little tension) really are, so it’s a rough guess
David Lang
let me try again
the 66 pound max rating of the motors is only achieved at stall, when they are
actually moving, their max force is actually a bit lower.
So we will run into problems along the top (the ‘hooking’ symptom moving towards
a motor) at a chain tension somewhere less than the 66 pound rating, but we
don’t know how much less.
So we don’t know what number in the ‘max tension’ box is actually too much to
have the machine work.
David Lang
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@dlang, I ran your version of the script, I like what you did by adding the grid. I referenced your 9.77 ft for calibrating the canvas in Fusion 360 and came up with the following.
Your current model seems a lot more optimistic, especially at the top.
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very probable, this was created before the kickstarter kits shipped, and looking
at the file, it says it’s setup for 30kg/cm instead of 20kg/cm so change the hi
value to 2.0 instead of 3.0 (on the line that starts with lo,hi about line 19)
and see if that’s better (you will have to change the height value to get to a
good image, and probably want to change the image size to get the bottom visible
again)
David Lang
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I tweaked it so it’s probably closer to real-world accurate (I don’t know where the side limits really are)
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I modified the spreadsheet to lock down all the formulas, but let you enter values in the green fields.
I also added a menu (Maslow Presets) up to the right of the help menu that lets you reset the values to any of the samples in the bottom right, and to copy a set from the top set of green values to the bottom set. This will hopefully help people make quick comparisons and reset the values on the sheet after others have tinkered with it.
You can always clone the sheet into your own account where you have full control of it.
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That graphic should be pasted right into the spreadsheet!
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@dlang I am not trying to re-invent the wheel here but in reading about the spreadsheet and motor ratings and chain tension a thought occurred to me that is just nagging me. I looked at the two images of the original frame and the new straight top bar and see the chains are wrapped around the sprocket in opposite directions but still have the black elastic pulling on the chain loop (original is vertical and top is horizontal) The nagging thought is how much tension is applied by the elastic … or more like what if instead it is INTENDED to apply tension or maybe instead of elastic you use cable to a pully that has a counter-weight equal to some portion of the max tension in the spreadsheet so it would lessen the high end of the motors force. Like a counterweighted elevator is able to use smaller motors.
dmac257
There are definitely Maslows out there that use a counterweight system. I don’t know if anyone has gone so far as to calculate the max tension in the way you describe, but it sounds like a reasonable approach.
dlang has recommended using counter weights in the past. it helps but not as much as you think becasue the gear motors lock in place, they are not freely rotating.