Actually thee currently is a problem with the UP trains using a section of the track. In between mile 12 & 9(Etobicoke North & Weston station), UP trains are limited to a maximum of 60mph when traveling eastward because of excessive lateral sway. Strangely enough when traveling at the same speed westward the issue is barely perceptible and so the speed restriction does not apply in that direction. Somehow going downhill seems to make it worse, as that's the only difference. Basically the trains vibrate violently when traveling at 70mph and above in this section of track. But apparently(most sources) have said they haven't been able to find anything wrong with the trains or the track.
I thought that they'd tracked that down to "subsurface conditions" by the golf course. I'll ask any of my contacts in T&S to see what they may know.
Very interesting. It may not be, but my first thought is undamped resonance in the bogies. The addition or modification of the existing lateral dampers, if any, might vastly reduce or eliminate the problem. It could be a 'corrugation' in the track inducing the behaviour in the bogies, and I noticed some harsh corrugation in the track at Mt Pleasant when waiting for a train last summer. How did it manifest? *Audibly* as a freight went by. It sounded like core lamination buzz in a faulty transformer, really loud, and my first thought was since it was a heavy stone train, there was some sort of electro-dynamic braking system being pulse-applied. As time went on, and the train speed and buzz frequency remained the same, I realized it had to be the rail-head, possibly the result of being recently laterally ground by a track maintenance train. I walked up and down the platform as the train passed, the sound was constant.
Whatever, rather than theorize, here's some research on bogie resonance, cause and remediation:
http://www.skf.com/binary/82-62732/RTB-1-02-Bogie-designs.pdf
https://sem.org/wp-content/uploads/...ction-Can-Explain-Rail-Corrugation-Growth.pdf
Here's a surprisingly good article at Wikipedia:
https://en.wikipedia.org/wiki/Hunting_oscillation
IIRC, the Amtrak E-60s had a severe problem with this that was never resolved. Googling, I can't find direct reference, but this might be related:
The locomotive was designed to be operated at speeds of up to 120 mph. However, its heavy weight caused the model to lean when operating at speeds in excess of 100 mph, resulting in the locomotive becoming unstable. As a result the Federal Railroad Administration limited the E60's top speed to just 90 mph, somewhat crippling its ability as a fast and efficient passenger locomotive.
http://www.american-rails.com/e60.html
(Addendum: The GMD (London, Ontario) Type 66 sold to AWS in the UK (and others later) had to have lateral and yaw dampers added to meet the requirements of the UK Rail Inspectorate (IIRC), track wear and stability being much more a concern in the UK and Europe in general, even though the 66 had triple axle self-steering bogies. The need for the added dampers was established by the forerunner Type 59. )
I've noticed more than a few times riding UPX for the Sharyo bogies (trucks) to hunt and flutter, sometimes causing what sounded like distress in the Cardan shaft joints. The only things I can relate the feeling to are the SRT and LRC coaches, both of which have small wheeled low-mass trucks. (The ride feels like casters sometimes!) Although the inducement might be in track irregularities, just like a car, within reason, it's the suspension 'tuning' that is responsible to accommodate it. The Cardan shaft drive might just exacerbate it, partly by reducing the unsprung mass evem further by having the drive motors inboard, and an unneutralized kick going back through the shaft to the motor. Again, not unlike front wheel drive stub-shafts on a car when wearing, especially the universals.
If this is the cause, it's an easy fix in terms of the mechanics, but a tough one to get the tuning right. It might take experimenting on the SMART cars not yet in service to get this right, albeit they might already be in service now. It might also take computer modelling. (Just adding an absorptive mass like a sand-bag on the trucks as an experiment might show a shift in the behaviour, and a hint on where to add dampers and their required counter behaviour).
Very curious...the field techs aren't going to fix this one. It's probably an engineering challenge.
