Need help with V-wheel adjustment

Hi, I’ve just finished assembling my shiny new LongMill 30x30 and I need some help with adjusting the V-wheel eccentric nuts.
I’ve consulted the assembly instructions, I’ve watched the video of Chris assembling and earlier version of the machine (V2, I think whereas I’ve got V4). I’ve done a little bit of searching on the forum about this - enough to know that I’m not the only one facing this issue.
The only criterion I can find for how tight to make the eccentric nuts is “when the wheels are hard to turn by hand”. That’s a pretty loose description - especially for an old guy like me whose grip and finger strength isn’t what it used to be!
Well, supposing that’s as good as the factory specification is going to get, are we talking about the top wheels? the bottom wheels? Am I supposed to somehow offset the weight of the gantries resting on the top wheels (and tending to free up the bottom wheels)?
When I jog the machine get very inconsistent results. I’m jogging 100 mm and sometimes it goes well and sounds like a healthy CNC stepper machine and just as often it stalls or makes a low-pitched grinding sound. In both of those cases I’m sure the actual position of the router would have been thrown off and any ongoing project lost.
I’d really appreciate any help there can be with this - I like the overall machine design but I don’t think I can actually use it until I get this resolved and have it stepping reliably without ever missing a step.
Thanks -

BTW, I’ve double checked all the electrical connections and couplers and they’re good - I’m pretty sure it’s the V-wheels and possibly a bit of the anti-backlash “robot” nuts.

Possibly happy ending here… after a bit more fiddling around I tried loosening and re-tightening the MOUNTING BOLTS for the anti-backlash (robot) nut and realized I’d probably never tightened them enough to begin with (fear of crushing the plastic part) and had mistaken the resistance of the nylock nut for the feeling of “snugged down”.
I think the (general) solution here is to break out the torque wrench and measure just how much resistance is due to the nylock nut and then come up with a target tightening torque which is comfortably more than the nylock resistance and comfortably less than what might crush the plastic.
I blush to report discovering an apparent solution which involved neither of the parts I’d decided were the problem.
The machine appears to be traversing pretty well now and I look forward to advancing to the next problem :slight_smile:

2 Likes

@BillFrog Bill. You seem to have solved the problem already, but I’ll butt in anyway. The wheels that you are playing with are, of course, the top ones. You already guessed that, when tightening them, you want to take the weight of the gantry off of them. You can simply lift up with your free hand, or use a wedge of some kind. I think that a little bit too loose is better than a little bit too tight, when dealing with the Y wheels, but that is only my unscientific opinion. As for the anti-backlash nuts, when adjusting them, tighten in 1° increments. It does not take much at all to take all the play out and an equal amount to make them too tight.

Have fun.