Gravity-based Chain Tension

Hardware Frame
1

I surprisingly received a MakerMade Maslow kit for Christmas complete with the pre-cut sled, and have begun the process of obtaining the router & other hardware and planning my frame design. I’m planning to run WebControl on a Raspberry PI 4b, and the ‘standard’ Ridgid 2202 router.

I’m fairly sure that my kit came with the ‘standard’ 11-foot lengths of chain, and I’m looking for ways to optimize that while still allowing as wide a top beam as possible. From what I’ve seen in the forums, proper chain tension is a busy topic, but I stumbled across a frame design (that I can no longer find again) that used weighted sleds riding a parallel surface beside the cutting area, and was thinking of doing something along those lines.

Does that sort of tension setup free up enough chain length to be able to go to a full 12’ beam, since it wouldn’t have to run into the center along a pulley setup, or should I start narrower and eventually upgrade the width when I can get my hands on some longer chains?

Overall, I’m thinking something similar to the 80/60 build, with a sled-support border of 12" all the way around, and then a 9" vertical ‘slide’ zone. I’m thinking that should keep the weights clear of the sled.

Are there pitfalls to that design that I should be aware of?
How much weight should I expect to need on each side, I’m seeing some people say 5 lbs is too much, and others saying that’ll be fine?

2

Just cut this in half and add to each side

3

I’m fairly sure that my kit came with the ‘standard’ 11-foot lengths of chain,
and I’m looking for ways to optimize that while still allowing as wide a top
beam as possible. From what I’ve seen in the forums, proper chain tension is
a busy topic, but I stumbled across a frame design (that I can no longer find
again) that used weighted sleds riding a parallel surface beside the cutting
area, and was thinking of doing something along those lines.

Does that sort of tension setup free up enough chain length to be able to go
to a full 12’ beam, since it wouldn’t have to run into the center along a
pulley setup, or should I start narrower and eventually upgrade the width when
I can get my hands on some longer chains?

unfortunantly it does not. you would still need to double up the chain through a
pulley or you don’t have enough vertical movement of the sleds (note, they can
be free hanging weights)

Overall, I’m thinking something similar to the 80/60 build, with a
sled-support border of 12" all the way around,

you don’t need any border on the top, and only a couple inches on the side
(3-4), and on the bottom you need 6-8 in.

and then a 9" vertical ‘slide’ zone. I’m thinking that should keep the
weights clear of the sled.

the weights are easy to keep clear of the sled, the motors are well clear of the
sled and so you can have the weights hang down under the motors without an issue
(they can be behind the workpiece)

Are there pitfalls to that design that I should be aware of?
How much weight should I expect to need on each side, I’m seeing some people say 5 lbs is too much, and others saying that’ll be fine?

you don’t want more than ~3.5 lb of tension on the chains (in the very bottom
corners), so due to the mechanical advantage of the pulley, no more than about 7
pounds on the slack side (and I am one who has forgotten the mechanical
advantage and said more than about 4 pounds is too much in the past)

when you can get a little extra chain to let you go to a 12’ top beam, the
tension increases to ~7 lb, so you can go to 12-14 lb of weight.

David Lang

4

There are lots of ideas from forum posts in the wiki manual here.

1 Like
5

This image is the design I was referring to with the weights sliding up and down alongside the work surface. I like it because it keeps the chains operating in a single plane.

I thought I remembered finding a build thread about it, but I can’t locate it again.

However, I don’t really understand why it still needs the gear ‘pulley’ rather than running the chain straight to the weight in order to ‘reclaim’ some extra chain length? Does the Maslow actually use up all/most of that doubled-up length to the point that there’s nothing significant left to ‘reclaim’?

Edit: And looking at the picture again, I just realized that even if there were a bit of extra length to ‘reclaim’, you need to double-up the length unless you actually had enough vertical distance to hang all of the chain length when the sled is closest to that corner. And now I realize that’s what dlang was saying in the first section of his reply.

2 Likes
6

I was sketching out my plans, and suddenly had a horrific realization that is going to completely alter my build plans.

The lowest part of the ceiling in my garage is a stretch across the center with air duct buried inside it, leaving me only 7’ of vertical space. If my calculations are right, a 15 degree angle for the front, and 1/4" of clearance for moving it leaves me with a total sloped surface height of just under 7’. That makes the extra height (~30") needed for a 12’ motor mount span with just 6" between the bottom of the plywood sheet and the floor.

Now I’m considering the options of:

  1. making sure I can easily tilt the frame for moving it around, so I can take advantage of the full 8’ height everywhere else in the garge, or
  2. going with a half-sheet build for the time being, or
  3. figuring out how practical it might be to build the Maslow into the shed in my back yard, and just run an extension cord from the house when I want to run it. (Or get a circuit run to the shed itself, but that’s a longer-term concern.)
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trying to go to 30" reduces the tension at the top center. So option 4 is to
build it and see how well it cuts at the top center. you may need to reduce your
feed rate to be reliable in that area, worst case you may not be able to cut
there (you can always flip the board to use that area)

but I would try it before going to extreme measures.

make the rear legs reasonably temporary so that if you do need to make it able
to tilt more you can easily modify them.

David Lang

1 Like
8

The 6" height at the bottom would mean that the sled would hit the floor 3" before the bit got to the bottom of the sheet. Even if I only went with a 24" rise, that would only leave me with 12" to the floor, which is going to be tight with the bricks, and even tighter for dust extraction.

I may spend the extra time/materials to build the work surface & top beam as a torsion box, to maintain rigidity, and mount it on a stand that allows it to pivot to horizontal for when I need to move it around. That’ll let me make full use of the 8’ height, buying back both the top rise and the lower clearance.

It might even let me mount the Pi & controllers inside where I can give them filtered air flow more easily. Fortunately, I’ve got a month or two to puzzle this out before weather gets good enough to be able to large construction projects.

This is all reminding me of the year we bought our first artificial Christmas tree, and then discovered that our house has 7.5’ ceilings, rather than the normal 8’. (We thought we had sized the tree to allow our topper to fit below the ceiling, but the tree was touching before we put anything on it…)