# Rotational Radius - Bit to Chain Tip or Bit to Ring

Having calibration issues and trying to limit variables.

I have a non standard sled ring I put together walking around home depot. Bear with me the ring is from a tomato cage and the roller bearings I found in the sliding door parts isle.

Now, is the rotational radius from the center of the router bit to where the chain mounts to the bearing holder(in red) or center of router bit to ring(in yellow)?

1 Like

Rotational radius can be thought of as the amount of extra chain that would be required to reach the router bit. So in your case it would be the red line. Though I also see that you have your chain doubled over a little bit at its end. So you either want to subtract that excess chain value from your measured red line. Or you can put a few links (whatever number that you double back near the ring) over the sprocket when extending your chain the first time

3 Likes

Ok thank you @johnboiles.

3 Likes

to be precise, itâ€™s the extra distance from the part of the chain that it at the
12 oâ€™clock position when you start moving (so the middle of the first link, not
the pin or end of the first link), if you feed an extra link through so that you
anchor to a solid link, you subract that extra length from the measurement.

the good news is that the calibration routine is designed to calculate this, so
as long as you are reasonably close when you start you should be in good shape.

David Lang

1 Like

I like precise. Although it might not show in the build of my crappy sled.

How round is the ring? Itâ€™s critical that itâ€™s as close to perfect as possible or calibration will suffer.

As far as I could tell its a consistent curve and sturdy enough. I added a second one that doesnâ€™t contact the roller bearing because the mounts were flexing, however Iâ€™m beginning to think itâ€™s not ideal. Weâ€™ll see.

1 Like

Hey Jay! Kudos to you for getting this far! A lot of us are spoiled by being able to build the Maslow from the kits. If you are struggling with your ring, the alternate pantograph solution is successfully being used by many folks. I think kits are availabe, as well as plans to make your own. No one has proven either solution to be the â€śbestâ€ť.

Good luck!

1 Like

I think @Bee is working on this!

1 Like

Yes! Kits are available at this link. Or, making your own is certainly feasible, if you make your own I would suggest stacking your bars and drilling them all at once so they are consistent. The actual lengths donâ€™t matter much as long as they are the same as each other.

As far as I know this is also correct. They both have their advantaged and disadvantages but itâ€™s uncertain if one is â€śbetterâ€ť. For some it just comes down to preference.
If someone has a ring and is willing to do a controlled test between the linkage and the ring Iâ€™ll send them a linkage! Just message me.

1 Like

and Iâ€™ll send them the top mount metal linkage.

David Lang