Maybe one of the railway men who lurk here can tell us if they still have tires on modern wheels, or do they scrap the wheel once it's worn down too far?
No they don't have tires over here, they have tyres. If the tyre starts losing it's profile - the curve from the tread to the flange - then it will be put on a ground lathe and turned to get the profile back to it's correct shape. The tyres will also be turned on a lathe to remove flats caused by skidding during the leaf fall season (it's no joke). Once the tyre has been machined to it's limits off it comes and a new one goes on.
Also today we have monobloc wheels that are treated just as above until they are due for replacement with a new wheelset. As to the original question it is as likely to be a sandite applicator as a grease pot. Sandite is a slightly sticky mixture containing sand that aids adhesion in the silly season. Found in places of known poor adhesion, on approach to stations/junction signals etc..
Tyres are still standard on the older locomotives (you can tell by looking for white paint marks on the tyre and wheel to detect a slipped tyre when they mis-align) but the standard wheel is now monobloc. Probably cheaper with new manufacturing techniques and far less work.
I have, in the past, had great difficulty persuading people to believe I was telling the truth when I mentioned that I had been helping to change the tyres on a (steam) railway engine over the previous weekend. "Don't be daft, they don't have tyres, they're all made of metal" was the general answer.
By tapping the wheel the resulting sound gave an indication as to whether all was well or not. Quite reassuring when one is bowling along at 80mph.
There is a techie name for the process - "Time Domain Reflectometry". When I sold kit for Tektronix in the 1970's we had a box that would test cables up to 50,000 ft long and give an indication as to any faults and their location by sending a single pulse down the line. An inverse fast fourier transform would reconstitute the pulse from the harmonics of the returned echoes for comparison purposes. I remember the blurb in the manual describing it as being similar to wheel tapping on railway stock.
Whelltapping still does happen on depot checks but it would only be of use on wheels that have tread brakes (traditional brake blocks). Wheels with disc brakes have cheek plates attached to the wheel faces which would not allow a true sound from the wheel when tapped.
Location: Why oh why would I wanna be anywhere else?
No they don't have tires over here, they have tyres.
True enough. Now.
It didn't used to be like that though. I have some old British encyclopaedias where some of the entries date from the 1920s or earlier which clearly use the spelling "tire" as well as "tyre". This got me doing a spot of research.
Tire is the more proper way of spelling it. It comes from the practice of attiring wagon wheels with a band of metal to stop the wood wearing down. It doesn't take a genius to get tire from attire. The Cousins kept the original spelling and the Brits went hoity toity with their new spelling!
but the standard wheel is now monobloc. Probably cheaper with new manufacturing techniques and far less work.
Might be country-specific. DB ( German Railways ) had a terrible accident some years back ( Meschede ? ) when one of the high-speed ICE trains came of the track and hit a bridge. From memory a monobloc wheel ( a money-saving innovation on that train ) failed catastrophically and they reverted to tires/tyres.
Well I got that well and truly wrong. Eschede, 1998, 101 people killed because a tire came off the wheel, wrapped around an axle and catapulted the train into the bridge.
Last edited by AlpineSkier; 29th Dec 2012 at 14:49.
The monobloc wheels on the MK1 ICE trains were prone to forming very slight ellipsoids causing vibration and were replaced with thin metal tyred wheels. These were on the train that derailed. It was subsequently found that the wheel inside the tyre fatigued and disintegrated when passing over a set of points causing the derailment. ICE trains are now fitted with advanced monobloc wheels.