Are wheelflats impossible to prevent?

[pompeyfan]

Note to Mods: if you feel this is better placed in the speculative discussion area, feel free to move it.

I notice that SWR are short of diesel units again, and my understanding is that this is due to several units suffering wheel flats due to leaf fall.

I see regular sarcastic comments from passengers along the lines of “if only someone could have predicted autumn was going to happen”.

My question is, is it a reasonable expectation for those not in the know for wheel flats to be completely eradicated? Is it possible? If it is possible is it financially prohibitive. Do the majority of passengers even care?

 

[HSTEd]

It is probably possible to build trains in which wheelflats are much less likely to occur than in legacy stock.

Magnetic track brakes and better traction control would probably help a lot in that regard.

 

[D365]

Magnetic track brakes and better traction control would probably help a lot in that regard.

The fitment of a modern wheelslip protection (WSP) system, along with variable rate sanders, makes the greatest difference when it comes to reducing the likelihood [and severity] of wheel flats.

I’m not sure how a magnetic track brake would help in the event of an axle locking under braking?

 

[HSTEd]

I’m not sure how a magnetic track brake would help in the event of an axle locking under braking?

A magnetic track brake would allow brakeforce requirements to be met without forcing the wheelsets to lock up.

 

[Pigeon]

With all axles individually powered, it is possible "these days" (has been for a pretty long time actually) to separately control the torque and speed of each motor, per fractional rev, in either the "forward" (driving) or "reverse" (generating) directions and through zero as well. It is therefore possible not only to brake by using reverse torque controlled so as to catch a slide before it gets going, but also to allow a controlled amount of wheelslip ie. with the wheel still rotating but at the "wrong" speed. This may help both to maximise the braking force and to mitigate leaf slime accumulation.

 

[edwin_m]

I’m not sure how a magnetic track brake would help in the event of an axle locking under braking?

It wouldn't help with wheelflats but it would be a way of stopping the train that doesn't depend (much) on rail adhesion. The Salisbury and Talerddig collisions probably wouldn't have happened had the 158/159 fleet been so equipped.

With all axles individually powered, it is possible "these days" (has been for a pretty long time actually) to separately control the torque and speed of each motor, per fractional rev, in either the "forward" (driving) or "reverse" (generating) directions and through zero as well. It is therefore possible not only to brake by using reverse torque controlled so as to catch a slide before it gets going, but also to allow a controlled amount of wheelslip ie. with the wheel still rotating but at the "wrong" speed. This may help both to maximise the braking force and to mitigate leaf slime accumulation.

True, but it's a lot more difficult to make this failsafe enough to act as an emergency brake.