Adjusting Eccentric Spacers for Resistance

So I started building my Sphinx C-Beam Machine last night.

And the first plate I assembled was a Y-axis plate. I found that I had to adjust how much I needed to torque down on the M5 locknuts in order to allow the wheels to spin without too much resistance. I noticed that some bearings feel smoother than others.

I then assembled the next Y-axis plate and because I did it once the next one went faster. I did not need to loosen the nuts from torquing down too much on them.

I installed both on the c-beam and can tell that the first one rolls easier than the second one. Which is odd. I would have thought that since I did not put any excessive forces on the bearings that the one i assembled second would have been better. Now..i reality neither one is really bad..they just aren't the same. And since the Sphinx C-Beam uses two stepper motor to move the Y-axis I have to believe that if they both move equally as free then that is better for the stepper motors and the accuracy of the machine.

So I am thinking I need to get some silicone lubricant to spray onto wheel bearings because I have now loosened the screws and they still feel like there is still some friction. And perhaps I should start all for adjusting the tension by rotating the eccentric spacers so they roll as loosely as possible and then adjusting them going from perhaps the small wheels to the large wheels from inside to outside.

Any suggestions would be appreciated.

Thank you,

Blake

 

NO I did not forget to install the shims..one between the bearings inside the wheel and the one that gets installed between the eccentric spacer and the wheel/bearing/shim assembly. But now that you mention it, it seems that a shim should be installed between the wheel assembly and the locknut but the build guide did not call out for one. Would that help?

The larger wheel assemblies have a shoulder to keep the bearings separated in the assembly process so unless you torque down on the locknut A LOT those bearings should never make contact. I never torqued down on any of the locknuts to the point where the wheels could not spin

The friction I am feeling is not significant..but it is still noticeable if you know how to properly assembly stuff. I've built lots of things throughout my from motorcycle engines to jet engines ( i worked for GE Aviation). I actually work for an aerospace bearing and seal manufacturer now and i run the machining department for bearings. I know how to machine stuff.

 

The wheel kits I used were OpenBuilds wheels. Both sizes of wheels had two spacers that measured 1.01 to 1.03 mm when I used my Mitutoyo digital caliper. I know a micrometer is more accurate but I don't have one.

I used some silicone lubricant and experimented with adjusting how much to tighten the locknut on the bearings. I found that how much to torque down on each locknut varied greatly in order to allow the wheels to spin without any of the rough feeling. The smaller wheels were more prone to having that rough feeling.

As I said I made sure to use a shim between the bearings when building the assembly.

I did notice that even though a member did say the locknut is smaller than the outer race and does not hit the outer race is not true if you install the nut with the hex side towards the bearing....which is what I had done. I did not see anything that explained that the nut should be installed with the round end towards the bearing. Since the round end of the nut is the end that has the locking ring part of the nut that seems like should actually be better since that way ensures that it is making full contact with the screw threads.