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Post by Deleted on Apr 5, 2017 19:47:00 GMT
I have just noticed that the new S-Stock trains still use the traditional tried and trusted Tread Braking system, where the cast iron brake blocks act directly on the wheel treads, and keep then cleaned in the process, a very useful idea, especially in the leaf fall season, where the use of the brakes cleans the leaf waste off the wheels, helping to prevent wheel slip etc.
Wasn't there an attempt to move over to disc braking at one time?? - but abandoned once the potential problems of contaminated wheels became known?
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Post by 100andthirty on Apr 5, 2017 21:05:45 GMT
As far as I am aware, nothing other than tread brakes were ever considered. S stock is all axles motored and the overwhelming majority of braking is carried out using the dynamic brake (regenerative and/or rheostatic, so the friction brake hasn't much work to do. I'm sure T697 will be along with chapter and verse.
S stock has excellent wheelslide protection and automatic sanding is due to be commissioned for the coming autumn.
The brake blocks are not cast iron and cast iron hasn't been used on LU passenger stock for a very long time. Composition brake blocks are used, and before anyone asks, asbestos in composition brake blocks was discontinued in 1984
By the way, the newer Siemens trains (class 700 and 707, and, I presume the forthcoming class 717) have tread brakes on the motor cars.
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Post by brigham on Apr 6, 2017 7:51:00 GMT
Disc brakes were tried on mineral wagons for a while, with excellent results, apart from trains disappearing from track circuits.
This was solved by giving each wagon a disc-braked wheelset, and a normal one.
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Post by countryman on Apr 6, 2017 8:02:53 GMT
As far as I know, all of the OBB locos of class 1016,1116 and 1216, recent OBB passenger coaches and DB ICEs have disc brakes. I dont remember seeing any clasp brakes. What I am aware of is that approach speeds are very high, and there is frequently a stench of burnt brake pads.
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Post by fish7373 on Apr 6, 2017 12:18:40 GMT
Hi one time a 1973 tubes stock was fitted with disc-brakes for testing.
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towerman
My status is now now widower
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Post by towerman on Apr 7, 2017 11:36:36 GMT
333O Mk1 72TS was also fitted with disc brakes,they were a pig to change the pads and everyone hated them.The conventional brake blocks are dead easy to change.
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Post by countryman on Apr 13, 2017 15:02:49 GMT
333O Mk1 72TS was also fitted with disc brakes,they were a pig to change the pads and everyone hated them.The conventional brake blocks are dead easy to change. The current problem with discs on cars is that the discs themselves wear at approximately the same rate as the friction material. I would imagine that it would cost a fortune to change the discs and pads on a train! |
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Post by Deleted on Apr 13, 2017 19:43:10 GMT
It appears that disc brakes are false economy, despite being cheap to buy and install, they need replacing very frequently indeed, with the high maintenance cost attached over the life of the train. "Whole Life Cost is too high for disc brakes."
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Post by t697 on Apr 25, 2017 17:44:47 GMT
As far as I am aware, nothing other than tread brakes were ever considered. S stock is all axles motored and the overwhelming majority of braking is carried out using the dynamic brake (regenerative and/or rheostatic, so the friction brake hasn't much work to do. I'm sure T697 will be along with chapter and verse. S stock has excellent wheelslide protection and automatic sanding is due to be commissioned for the coming autumn. The brake blocks are not cast iron and cast iron hasn't been used on LU passenger stock for a very long time. Composition brake blocks are used, and before anyone asks, asbestos in composition brake blocks was discontinued in 1984 By the way, the newer Siemens trains (class 700 and 707, and, I presume the forthcoming class 717) have tread brakes on the motor cars. I hadn't noticed this thread until recently. Yes a good summary on S stock. I seem to recall disc brakes were only considered briefly back at the concept stage. The weight and rotating inertia of discs wasn't thought worth it set against the light friction brake duty in normal service. 10 years onwards one might think about that again for various reasons, but probably would still settle on tread brakes I suspect. It will be interesting to see which way the New Tube for London (NTfL) or Deep Tube Upgrade (DTUP) trains go on this. I think LUL stopped having any asbestos in the brake blocks way back in the 1970s. The changes in the 1980s were to stop using silica. |
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Post by ted672 on Jun 16, 2017 19:31:24 GMT
I can't help noticing that the final application of the friction brakes on S stock results in high pitched squealing as the train comes to a halt. Is this a result of lack of heat in the friction brakes as most of the work is done by regen.? Is any work ongoing to reduce what must be quite a nuisance for residents near stations?
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Post by Deleted on Jun 16, 2017 20:22:07 GMT
You always get some squeaking when friction brakes are used, whatever the type of train, it cannot be avoided and often line-side noise attenuation barriers are installed to quench the noise, I noticed some noise limiting barriers on the DLR Lewisham branch, and on the Elizabeth Line's upcoming Abbey Wood Branch.
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