I have noticed recently that something that looks to be a plastic object has been put on the wheel lugs of New York City buses. I haven’t seen these on other vehicles except for Access-a-ride vans (which I think are operated by the MTA).
It’s tough to describe them and I can’t find an image but here goes:
The object is a small plastic piece that is almost teardrop shaped. The large round end is between the lug and the lug nut. It is installed so the small pointed end is pointed directly at the next lug. The piece is the highly visible green/yellow color. There is one of these on every lug, all installed to point to the next lug.
I can’t figure out why they are there or what purpose they could possibly serve. If they have a purpose why don’t other truck type vehicles have them.
They are torque indicators. When the lug nut has been torgued to the correct value, the indicator is applied. If the bolt or nut loosens, the indicator will be pointing in a different direction and will be easily noticed. The maintenance folks will then correct the problem.
Here’s a link to free patents on line that appears to be the item in question: Torque Loss Indicator
And of course the ever popular Wiki entry: Wiki Link
Not at all. What one would think is an inexpensive non-moving parts logical way to indicate a change in tightness has actually become a cottage industry, replete with paybacks, scandals and underage workers in Sheepshead Bay crafting the indicators after hours.
So, how many jokers are running up to buses now and re-positioning these things so the drivers or maintenance crews think the nuts are coming loose? Similarly, how ften to they just fall off?
The wiki article makes it sound like the things are just slipped over the nuts after they’ve been torqued, so it would be simple for people to mess with them.
The wiki article mentions one type of tag that they use where it’s actually two tags pointed at each other and connected by a stong peice of plastic. They say this is to prevent the nuts from turning in the first place. It seems like this might allow for the nut to turn without the tag moving and causing a false sense of security.
What ever happened to the age-old art of using safety wire for this type of application? Why do we need these little plastic widgets that really do nothing when smarter people had already provided a fool-proof solution by the turn of the previous century?
Wouldn’t that only work if the lug nut goes on and is properly torqued at exactly the same spot each time? I would think over time with wear and tear (and different lug nuts being used on different lugs each time) it wouldn’t properly line up each time.
You answered your own question. The application of safety wire is an art. Apply it wrong and it is useless. Also you can use the plastic indicators and tell from 30 feet away if all the nuts are still tight. With safety wire you have to get up close and personal with the item in question.
The way these work is that there are six to 12 slots in the top of the lug or the top of the nut. Then the wire or pin can be put through no matter where the final torque ends up. There will be a 1/6 or 1/12 of a revolution that the nut can travel before it is stopped by the pin. I had these on the rear wheel of one of my motor cycles. They are sort of a pain. I can imagine they would be a real pain if I had 12 of them for each wheel to deal with.
I see the plastic pointy things on lots of truck here in southern California perhaps on 1/4 of the big rigs.
