Powder Coat Affecting Lug Nut Seating?
Powder Coat Affecting Lug Nut Seating?
(OP)
Hi everyone,
I have a problem that I inherited from a previous designer that I need help with. My company currently builds wheel assemblies for pivot irrigation systems (among other things), and our current design utilizes a steel T-wheel that is powder coated. The bolt holes in the wheel have a standard 45° bevel to match the lug nuts. Trouble is, farmers are reporting that the lug nuts keep coming loose in the field. They say they do not have this problem with pivot system wheels from other manufacturers. Part of the problem may be vibration - our wheels are completely solid and flat-free, as opposed to pneumatic wheels (which I would think would absorb more of the vibration). However, there are other solid wheels out there, and we haven't heard of this problem with those wheels.
My suspicion is that part of the problem may be the powder coating. When the steel wheel section is powder coated, they do the entire thing, including the lug nut bevels (not my decision - like I said, I inherited this design). I've read in some automotive forums that paint and/or powder coating on the lug nut/wheel mating surfaces may cause this type of problem (though I haven't seen any conclusive proof of this presented).
What do you think? My plan of attack is to try removing the powder coat from these surfaces on a couple of wheels and see what happens in the field. Unfortunately, our CEO (my direct supervisor) overruled me (wouldn't say why except that he thinks it's a "bad idea" - he's not an engineer). He said I should keep trying to find a locking wheel fastener(?? yeah, I know...).
Any input would be appreciated. Thanks.
Richard
I have a problem that I inherited from a previous designer that I need help with. My company currently builds wheel assemblies for pivot irrigation systems (among other things), and our current design utilizes a steel T-wheel that is powder coated. The bolt holes in the wheel have a standard 45° bevel to match the lug nuts. Trouble is, farmers are reporting that the lug nuts keep coming loose in the field. They say they do not have this problem with pivot system wheels from other manufacturers. Part of the problem may be vibration - our wheels are completely solid and flat-free, as opposed to pneumatic wheels (which I would think would absorb more of the vibration). However, there are other solid wheels out there, and we haven't heard of this problem with those wheels.
My suspicion is that part of the problem may be the powder coating. When the steel wheel section is powder coated, they do the entire thing, including the lug nut bevels (not my decision - like I said, I inherited this design). I've read in some automotive forums that paint and/or powder coating on the lug nut/wheel mating surfaces may cause this type of problem (though I haven't seen any conclusive proof of this presented).
What do you think? My plan of attack is to try removing the powder coat from these surfaces on a couple of wheels and see what happens in the field. Unfortunately, our CEO (my direct supervisor) overruled me (wouldn't say why except that he thinks it's a "bad idea" - he's not an engineer). He said I should keep trying to find a locking wheel fastener(?? yeah, I know...).
Any input would be appreciated. Thanks.
Richard





RE: Powder Coat Affecting Lug Nut Seating?
RE: Powder Coat Affecting Lug Nut Seating?
Powder coat is very difficult to remove, and very tough and strong. ... for a plastic. It will, as noted, creep under the load applied by the wheel nut, and will eventually relieve all of the preload applied, leaving the nut loose.
You could cross-drill the studs, castellate the nuts, and apply cotter pins or hitch pin clips. The plastic would still creeep, remove the preload, and the repeated shock would eventually fracture the studs, possibly after the rattling and looseness destroy your reputation.
The proper thing to do is mask the nut seat tapers before powder coating.
If cosmetic rust is of concern, You could electroplate or paint that area if you wish, or wet the tapers with paint or varnish at assembly.
I would paint the tapers and the studs with Never-Seez or Loctite PST at assembly, but that's just me.
Mike Halloran
Pembroke Pines, FL, USA
RE: Powder Coat Affecting Lug Nut Seating?
My experience says that alloy wheels require more torque than steel wheels to stay tight - and the issue is very similar. Alloy compresses more and doesn't provide as much friction.
RE: Powder Coat Affecting Lug Nut Seating?
Some serrations - either on the wheel or on the lug nuts. Those would act like lock washers. I'm thinking a simple sharp edged dent or 2 on the tapers of either.
RE: Powder Coat Affecting Lug Nut Seating?
I'll try to use what you've said as ammunition to convince my boss that we need to remove the powder coat on the bevels. Just for clarification: these pivot wheels are going on someone else's pivot irrigation system, usually already in the field. I can only control the design of the wheel itself, not the wheel studs or the lug nuts. Nor can I paint or coat the lug nut/wheel interface after the lug nuts are applied, as the farmer will in most cases be doing the install.
RE: Powder Coat Affecting Lug Nut Seating?
If there is nothing to be done to any part but the wheel, a weekly re-torque for several weeks is the only option I can think of.
RE: Powder Coat Affecting Lug Nut Seating?
RE: Powder Coat Affecting Lug Nut Seating?
So my idea of serrating ((or notching) the lug nuts would not work - but you could do the wheel.
And more thoughts: How about roughening the taper a bit before powder coating? Or adding a bit of grit to the tapered area just before baking?
RE: Powder Coat Affecting Lug Nut Seating?
Are the wheels centered by a pilot diameter feature on the hub, or by the fasteners?
Do the steel wheels have some stamped in curvature to provide a belleville washer effect?
http://taxilimoautoparts.com/images/rr1%20024.JPG
Preventing the fastener from un-screwing is desireable, but only to prevent a mid term problem of fastener loss.
Lug nut$ with nylon patche$ might serve that purpose, but I would not expect them to prevent loss of preload from powder coat embedment, and the resulting beating up of the studs, nuts, wheel, and hub.
As mentioned by others The loss of fastener preload can result in fastener fatigue due to 10X higher alternating stress. Then that busted hunk of fastener with the nut still secured by a cotter pin or whatever will fall into the furrow, and the surviving (loose) fasteners, possibly laden with hungrily progressing fatigue cracks will be left to handle even greater loads.
RE: Powder Coat Affecting Lug Nut Seating?
RE: Powder Coat Affecting Lug Nut Seating?
You can probably find a 'stock' locking lug nut, retaining clip, and tab washer from Stage 8.
They will prevent the nuts from loosening enough to fall off.
They will NOT compensate for loss of preload from yield of the powdercoat, so the nuts will still get loose, and if nobody does anything about it, the loose nuts will eventually cause the studs to fracture.
On second thought, maybe Stage 8 could provide locking lug nuts with Belleville washers roll staked on the cones. I would still use the clips and tabs, but inserting an actual Belleville washer in the stack might be enough to offset the yield of the powdercoat. Don't expect to get specials like that for free.
Mike Halloran
Pembroke Pines, FL, USA
RE: Powder Coat Affecting Lug Nut Seating?
Sounds even more like the (inherited) wheel design is the boss's own baby and he needs it to work no matter what.
Norm
RE: Powder Coat Affecting Lug Nut Seating?
Are the wheels centered by the studs, or a pilot diameter?
Aren't automotive lug nuts commonly 60 degrees included angle?
RE: Powder Coat Affecting Lug Nut Seating?
Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB
RE: Powder Coat Affecting Lug Nut Seating?
RE: Powder Coat Affecting Lug Nut Seating?
I have confirmed that the chamfer used on the irrigation system lug nuts (at least all the ones I've seen so far) is 45°.
The center hub fits through the center pilot hole with a slip fit, so there is some centering action there, at least during installation (see picture). And yes, this is definitely an ancient wheel design - very heavy.
RE: Powder Coat Affecting Lug Nut Seating?
The newest car I know of with lug centered from the factory was a 1978 Honda Accord.
RE: Powder Coat Affecting Lug Nut Seating?
"...verboten not only to avoid fitment ISSUES, but in the......." and "...too deep and I've seen torque LOSS occur before."
Tim Flater
NX Designer
NX 8.0.3.4
Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB
RE: Powder Coat Affecting Lug Nut Seating?