V-wheel to rail pre-load tension

[bLouChip]

Can someone please comment on the sufficient pre-load when adjusting each of the 3 axes V-wheel to rail tension via the eccentric spacers ?   I had no discernible wobble or play in the plate assemblies and gantry (trucks) when I mounted each to the rails, and nice smooth rolling action. But in anticipation of wobble or play from the loads of actually routing a work piece, I adjusted the eccentric spacers just a tad anyway to "snug" up the wheels.   As expected, I noticed that the force necessary to move the "truck" or axis (without lead screw installed) down the rails had increased. Wanting to know how much force it takes to move, I came up with a repeatable and perhaps universal method which uses a light coil spring approx. 3 inches long, 3/4 inch dia, and made from 0.030 steel spring wire, 3 wraps/inch. Any similar spring should work also.  I "calibrated" my spring on a digital kitchen scale, it takes 20 oz. of force to compress 1 inch. I then used the spring to push each truck and measure the force it takes to get it moving.  I adjusted each truck / axis to 25 oz., a purely arbitrary force which happens to be a "tad" adjustment of the eccentric spacers and resulting in "snug" V-wheel to rail relationship.

I'm hoping someone can measure their system and comment on this force.  Or is this a moot point given the wheels are a cushioned material, bearings and rails are stout, and other forces on the axes can far exceed a mere 25 oz. ?

In the meantime, I'm waiting on some back order parts to complete my Carve King assembly.  Chomping at the bit

Thanks,

CNC newbie

Lou

[Derek the Admin]

Hey Lou. The way I check this in my builds is to block the mechanism from moving with one hand (IE: Hold the gantry in place) and see if you can still turn the wheel with your index finger and thumb. If you can't they are probably too tight. If you can turn them with some resistance, you're good to go.

Hope that clears it up.

Derek

[bLouChip]

Ok, good answer. I tested as you recommended and found the v-wheels a little tight, so I backed off the tension. For what it's worth, the force to get them rolling now is about 22 oz. thanks.

[Derek the Admin]

Awesome. Thanks for the feedback.

[bLouChip]

CK build is complete ! System is GO! Hope to mill a test project today. I still have to build an enclosure and mount the laser, but one step at a time...

[Derek the Admin]

Awesome. Show off what you make!