Besides the cost of special track, what are some drawbacks to the old rack railways?

[Matthew T]

I really don’t know about them past one of the books from The Railway Series.

Thanks!

 

[30907]

Rack (and pinion) railways were a (late) 19th century solution to the need to overcome large differences of height in a short distance. The only alternative would be extensive spirals or a long deviation, which would also be costly.

Apart from the need for specialised track and locomotives (probably the most disproportionately expensive item, and also expensive to maintain), the major disadvantage was speed (or lack of it).
As locomotive capability improved, and especially with electrification, gradients became less of an issue, to the extent that gradients of 7% (1 in 14) became perfectly feasible and many rack sections on normal routes became redundant. Others have been replaced by re-routing, even in very recent years.

Even in Switzerland I can only think of a couple of routes which serve mountain communities rather than essentially tourist purposes - there are plenty of the latter still.

Incidentally, while there are a couple of preserved rack sections (I know of one each in CZ and SK), and a number of lines that operate historic trains on their own tracks, pretty much every rack line in Europe operates a regular commercial service.

 

[edwin_m]

What are some drawbacks to the old rack railways?

That's a matter of a pinion.

As the rack is higher than the rail, the pinion must be either of smaller diameter or not on the same axle as the normal driving wheels. Either way it introduces extra complication to ensure that the driving wheels aren't slipping relative to the rails when running on the rack. Unless the trains can only run on rack, in which case every piece of track has to be fitted.

The rack is always greasy. Does this have to be applied along the track or is it dispensed from the loco? Possible risk of environmental damage in the sensitive areas these railways tend to go through.

The brakes must be good enough to stop the coaches using adhesion only if the train uncouples, unless either all the rack gradients are one way and the loco is always at the lower end, or the coaches have their own pinions for braking purposes.

As locomotive capability improved, and especially with electrification, gradients became less of an issue, to the extent that gradients of 7% (1 in 14) became perfectly feasible and many rack sections on normal routes became redundant. Others have been replaced by re-routing, even in very recent years.

Something as mundane as the Sheffield Supertram uses adhesion on 10% gradients, albeit it needs all axles motored. I think Lisbon trams have 13% gradients.

 

[Ploughman]

I think speed is the biggest problem or lack of.

 

[Tim M]

That's a matter of a pinion.

As the rack is higher than the rail, the pinion must be either of smaller diameter or not on the same axle as the normal driving wheels. Either way it introduces extra complication to ensure that the driving wheels aren't slipping relative to the rails when running on the rack. Unless the trains can only run on rack, in which case every piece of track has to be fitted.

The Snowdon Mountain Railway follows Swiss practice with the wheels being free to rotate on the axles, their only function is to carry the loco or carriage. On mixed rack/adhesion railways the pinions are often on a separate ‘axle’ with independent traction power for pinions and wheels.

 

[edwin_m]

The Snowdon Mountain Railway follows Swiss practice with the wheels being free to rotate on the axles, their only function is to carry the loco or carriage. On mixed rack/adhesion railways the pinions are often on a separate ‘axle’ with independent traction power for pinions and wheels.

Thanks for that. I did wonder about Snowdon as it seemed to have the rack right into the platforms at the lower station.

 

[Bald Rick]

That's a matter of a pinion.

Very good. You must have racked your brains for a while to come up with that.

 

[30907]

Very good. You must have racked your brains for a while to come up with that.

An Abt response

 

[edwin_m]

Very good. You must have racked your brains for a while to come up with that.

Yes, I had to do a fair bit of cog-itating.

I'll slope off now.

 

[Richard Scott]

There must be an efficiency cost too? Extra friction between cog and rack would add to energy costs. The time I went on one in Switzerland noticed it was quite noisy.

 

[ainsworth74]

Something as mundane as the Sheffield Supertram uses adhesion on 10% gradients, albeit it needs all axles motored.

Yes the first time I used the Supertram I was left somewhat in of awe of the way it bounded up these seemingly impossibly steep gradients.

 

[Ploughman]

An Abt response

I FELL about the place on seeing that.

 

[30907]

I FELL about the place on seeing that.

I give up - I'll stick with adhesion

 

[edwin_m]

I give up - I'll stick with adhesion

Need to get a grip on this, or it will rapidly slide downhill.

 

[Welly]

I once went from Chur to Brig on the Glacier Express run by the RhB, parts of the route has racks and we changed to a pinion fitted locomotive at one station. Even way back from the locomotive it was possible to tell that the pinion is engaged to a rack by the vibration!

 

[43096]

I once went from Chur to Brig on the Glacier Express run by the RhB, parts of the route has racks and we changed to a pinion fitted locomotive at one station. Even way back from the locomotive it was possible to tell that the pinion is engaged to a rack by the vibration!

Locomotive change is done at Disentis/Mustér, which is the "border station" between the Rhätische Bahn and Matterhorn Gotthard Bahn. As I understand it, each coach is also rack equipped - should there be a coupling part, the train still needs to come to a stop - which is what you can feel as you enter a rack section.

 

[Welly]

Locomotive change is done at Disentis/Mustér, which is the "border station" between the Rhätische Bahn and Matterhorn Gotthard Bahn. As I understand it, each coach is also rack equipped - should there be a coupling part, the train still needs to come to a stop - which is what you can feel as you enter a rack section.

Ah! Now I understand, the coach has pinions as well!

On this topic, I have just watched this interesting video of a rack and pinion tramway close to Stuttgart

I love the bicycle wagons!

 

[Midnight Sun]

That's a matter of a pinion.

The rack is always greasy. Does this have to be applied along the track or is it dispensed from the loco? Possible risk of environmental damage in the sensitive areas these railways tend to go through.

Lube is sprayed directly onto the cog wheel teeth. The lube used now is Biodegradable.