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Chain tensioning spool

Hi Maslow CNC Community,

I’m a newbie building my first Maslow frame. Here’s my approach to chain tensioner: a spool powered by two springs taken from the largest (10 meter) and cheapest tape measures I could find.

Is there a reason why this solution isn’t used much? I couldn’t find anything similar so far, everything is either bungee cords or weights.

Sending a video and picture.



The reason is probably because your solution is so brilliant that surely I didn’t think of it. Weights were an improvement compared to bungee cords but the weights always dangle in the way when you shift the frame. Your solution solves that and keeps the slack chain always parallel.


Yeah, we didn’t do it because we didn’t think it was possible. Brilliant!!

I watched the video clip again because it is so well engineered. I did notice that from 10 to 15 seconds the chain makes a snapping sound. You can see that the teeth of the sprocket lift the chain. Also at 34 seconds when the rotation is reversed the slack side does the same. You don’t hear it as much because the tension is lower. The chain and sprocket will wear faster or maybe derail at some point.

But again a brilliant solution, respect :slight_smile:

Yes, thank you. I actually noticed that and cringe at that sound myself. I will change the offset of the top beam relative to the work plane. The choice of top beam material is poor, too - plan to go for a metal beam ultimately. Just learning and experimenting.

The slack side is easier to adjust, as the tensioner can be moved to better match the plane of the sprocket.

I think @dlang proposed this a long while back. I’m sure he’ll be glad to see someone did it.

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just keep the tension low so that you don’t end up with more tension on the
slack side than on the sled side (about 4 pounds of tension), but this sort of
take-up should not need much tension as you don’t have a lot of chain dangling

good to see someone build this.

David Lang

can you provide the details of the build (sizes, what sort of spring, etc)

David Lang


Too much tension on the slack side is not a problem with this setup. Rather the opposite, the reason I had to use two springs instead of one was because the pull of one wasn’t reliably strong. I’m still looking at other options for springs, e.g. a spring from retractable vacuum cleaner cord. This should provide for even more compact design.

Currently I use two springs from 10 meter tape measures.

Will be happy to share all the details of the build, stay tuned. Would a video teardown/build of the system be helpful?



Yes please!

Yes please. I came up with the idea and posted some diagrams

you not only came up with the idea independently of me, you actually built it.

David Lang

Elegant! The slack chain is automatically parallel to the work piece. Also would appreciate details of the build.
Thank you,

I’ve spent a productive weekend rethinking and reimplementing the design to make most parts of the tensioner easily machinable on Maslow. I think the goal should be cutting all non-metal parts from a single sheet of thin plywood.

Here is a video with the assembly process and comments on the design in general. As I probably didn’t capture everything that the community wants to know, please ask questions in the forum.


Absolutely brilliant! I love that pin you use to hold the end of the chain in…so clever! A fantastic design :grinning:

Glad you noticed! The pin was one of those small heureka moments.

Excellent video, thank you for your explanation. Never knew how the spring worked in a tape measure either, now I know!

Nicely done.


This counter weight system works really well, my Maslow is on wheels, and I had temporarily mocked up something similar to this, but then couldn’t roll it. Nicely done.
What is your frame made from?

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I like your approach to keeping the weights in plane. Very well done!