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Ideal Max and Min Chain Tension and Counterweight Recomendations

After inputing my design data into the Chain Geometry Spreadsheet, I have obtained the following:

Max Chain Tension = 39.9 lbs / 18.1 kg
Min Chain Tension = 7.15 lbs / 3.24 kg
Counter Weight = 13.5 lbs / 6.1 kg (per chain)

What I would like to know is the following:

  1. Where do my chain tensions stand when compared to an expected or an ideal?
  2. What is the appropriate counterweight per chain that I should be using?

@dlang or @madgrizzle, I’m tagging you two because you seem to have contributed the most to this subject. There has been a lot o time spent discussing this but my forum searches don’t seem to be coming up with a specific answer to my questions

on the spreadsheet @

it lists some common examples

you seem to be about the same as a 12’ top beam at stock height, significatnly
better min tension (improving the bottom corner) slightly higher max tension
(more likely to run into grief in the top center). Raising the top beam a bit
will improve the top center significantly without hurting the bottom corners s
much, but may or may not end up being needed. I would leave it as-is unless you
run into problems.

you don’t want the tension on the slack side of the chain to be higher than the
tension on the sled side. with a sled-side tension of 7.15 lbs, and a 2:1
mechanical advantage (the pully/sprocket), 13.5 lbs is really pushing the limit
(I would say beyond the limit, since the sled-side tension assumes no friction)

David Lang

Thank you for your input. I needed a sanity check.

Just to make sure I understand you correctly:

  1. I could improve the top center by raising the beam height, but it may not necessarily be needed. I’ve maxed out my headroom (in a basement) so that will have to wait until I can get a better shop location anyway.

  2. I may want to consider decreasing the ammount of counter weight I am using because its pretty close to exceeding my minimum chain tensions (if it isnt already).

I should point out that my work surface is smaller than a normal Maslow. It’s only 43" H x 66" W.

Thank you for your input. I needed a sanity check.

Just to make sure I understand you correctly:

  1. I could improve the top center by raising the beam height, but it may not necessarily be needed. I’ve maxed out my headroom (in a basement) so that will have to wait until I can get a better shop location anyway.

the stock design is 33 pounds tension in the top center, some people with
marginal power supplies have had problems there, but 40 pounds should be ok. We
know that 50 pounds is enough to be a problem

lowering the workpice will also work :wink: or if you have trouble, feeding a bit
slower.

  1. I may want to consider decreasing the ammount of counter weight I am using because its pretty close to exceeding my minimum chain tensions (if it isnt already).

yes

I should point out that my work surface is smaller than a normal Maslow. It’s only 43" H x 66" W.

the beauty of working with the tension figures is that the size you are talking
about doesn’t matter. The tension figure tell you if the motors can provide
enough force at the top center, and how well gravity will move the sled in the
bottom corners.

David Lang

Ok, got it. I decreased the CW down to 12 lbs to start. I’ll run some tests to see where to go from there.

with the counterwights too heavy, what will happen is that at the point where
the tension towards the sled matches the tension on the slack side, there will
be a small amount of motor movement that does not result in sled movement. It is
a small amount and you may not notice it, and the line where this happens is a
curve.

David Lang

Perfect, now i know what to look for.

Limiting chain tensions is a good idea to limit strains on them and the motors, but for stability you really want them to be as high as you can get them. Also, its not as simple as looking at chain tension. You have to look at the X and Y components to really understand the expected stability. The maslows biggest design weakness is the low X tension in the lower left and lower right corners of the work areas. Try using my version of that spreadsheet and see what numbers you get.

Per your version of the calculation I am sitting at 40lbs at the top center and 7lbs in the lower corners.