The O gauge locomotives I have, have their idlers gears exposed. Similar to real trains, when O gauge equipment passes over track, small fine particles of stuff gets airborne. The rail equipments body-mass disturbs the still air, as it passes over the track, and that swirling vortex of air can pick up small lose particles/debris... in it's path.
Are ya paying attention, lad? Are ya getting this...
A tech from one of the manufactures actually suggested that, I shouldn't use anything that could trap contaminants in the idler gears; because trapped contaminants can cause impaired operation... including binding and ultimately, the truck(s) can seize up.
I actually had to replace a seized up truck, once. I tried everything I could think of..., but I just couldn't get the wheels to budge.... and turn again.
BTW, hair, especially longer hair, can really foul up a truck... if it gets caught up and wound in tight.
Re Kilts:
A while back, I did some research on the famous Scottish rigs(kilts); and the good ones... are quite dear(expensive). There's also a wee bit of protocol that goes along with it...
I wouldn't mind sporting a big bad beard and a kilt one day, me son. I might have to resort to borrowing one of me mom's old plaid frocks though, if the official route becomes too challenging and expensive.
An idea:
When you finally complete this great new O gauge layout of yours... don one of you favorite kilts, strap on the bagpipes and have a proper opening ceremony. You might want to make a video of the occasion and post it here, as well.
Your a good lad, Davy.
Cheers to ya,
Rick