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Post by Deleted on Feb 16, 2008 1:16:55 GMT
Just a little bit of curiousity here. Do train operators notice any difference in performance of their trains when they are fully loaded with commuters?
How significant is the loss of acceleration and braking when driving a full train versus empty?
The D-stock refurbs have also gained weight - do they feel any slower and is braking distance affected by the extra weight versus a non-refurb?
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Post by happybunny on Feb 16, 2008 2:05:21 GMT
I find generally the refurbed D stocks' brakes' are often very questionable. Sometimes you get a decent train, with good breaks. Other times they are really bad. Often you see in the defect logs, drivers reporting "very week brakes" and the fitter replying with "tested in depot, brakes OK"... hmm how they can really test the brakes in a depot with a 5 or 10 mph speed limit I don't know!
Anyway as for loading, if a train is really really packed, I think it can feel slightly more "sluggish" than a empty/quiet train. The braking however, I find is unaffected by loading. And of course there is the problems of gaining/keeping pilot light on a really really packed train.. however I find from experience this is not such an problem on surface stock, as it is on tube stock!
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Post by c5 on Feb 16, 2008 10:35:08 GMT
I find generally the refurbed D stocks' brakes' are often very questionable. Sometimes you get a decent train, with good breaks. Other times they are really bad. Often you see in the defect logs, drivers reporting "very week brakes" and the fitter replying with "tested in depot, brakes OK"... hmm how they can really test the brakes in a depot with a 5 or 10 mph speed limit I don't know! Report it on the road to the Controller and ask a TT or a DMT to confirm it!   |
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Post by 100andthirty on Feb 16, 2008 12:45:10 GMT
And make it very clear on the trouble card that it's "weak brakes when loaded". Then they can't just clear in a depot test run and they would need to check the variable load system.
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Post by District Dave on Feb 16, 2008 16:56:13 GMT
My understanding is that during the reurbishment programme BTUK have adjusted the brake pressures to those in the original train specification and these have remained whilst the trains have remained under the care of bombardier - that is during the warranty period.
However (i have been told), the depot staff use higher pressures and hence 'older' refurbs have better braking performance , although it has to be said not as good as the trains pre-refurb - bearing in mind refurbed trains weigh more. Certainly that appears to have been the case.
Or is that another set of urban myths?
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Post by trainopd78 on Feb 16, 2008 18:04:57 GMT
That certainly is true DD. I got that confirmed from one of the DDM's. It seems the depot try to marry up units in warrantly to units out of warranty to try to improve matters a bit. Only another 12 months and they'll all be better again. |
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Post by happybunny on Feb 16, 2008 22:55:18 GMT
It is a little bad though, I think personally, that if you find yourself in such a situation (as a Driver) the difference between having a SPAD and being very close to having a SPAD (something which will have an effect on you're career) rests on if the train is under warranty, or not! All trains should be set for maximum braking performance. In the best interest of all concerned
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metman
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Post by metman on Feb 17, 2008 0:51:10 GMT
To be fair, that's sounds good to me! Could somebody explain the warranty to me?
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Post by trainopd78 on Feb 17, 2008 16:14:56 GMT
Once a unit comes back from Derby after refirb they have a 12 month warranty. During this time BTUK have to maintain the unit and anything repaired by Metronet will totally invalidate the warranty. Oce the 12 months are over, the unit returns to the care of Metronet.
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Post by auxsetreq on Feb 17, 2008 21:32:35 GMT
Just a little bit of curiousity here. Do train operators notice any difference in performance of their trains when they are fully loaded with commuters? How significant is the loss of acceleration and braking when driving a full train versus empty? The D-stock refurbs have also gained weight - do they feel any slower and is braking distance affected by the extra weight versus a non-refurb? No! Not personally - The newer stocks have variable loading which means the braking and acceleration is adjusted automatically according to the weight of each individual car. The performance of a packed out car and an empty one right next to it should, in theory be exactly the same, and on the stock that I work on, it is! Whether they have variable loading on the wind up 78s I'm not sure............ |
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Colin
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Post by Colin on Feb 18, 2008 2:07:05 GMT
We do have variable loading on the D's - but only on the brakes. The rate of acceleration can be improved by use of the weak field flag where it's use is authorised.
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solidbond
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Post by solidbond on Feb 18, 2008 6:44:07 GMT
We do have variable loading on the D's - but only on the brakes. The rate of acceleration can be improved by use of the weak field flag where it's use is authorised. Tut tut Colin - you obviously weren't paying attention on that day in the classroom ;D The air that goes through the Variable Load Control Valve, and the Variable Load Valve, not only goes to the brakes, but also to the RPA (Rotary Pneumatic Accelerator) to vary the acceleration as well ;D ;D ;D Regarding the brakes on refurbs, at a meeting a couple of years ago where this was raised, (and PRJB can confirm ) one of the project engineers claimed that the problem was that the brakes on D stock were ABOVE specification, and all that was happening was that they were being adjusted to be WITHIN specification. Now make of that what you will |
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Colin
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Post by Colin on Feb 18, 2008 14:40:39 GMT
Tut tut Colin - you obviously weren't paying attention on that day in the classroom ;D The air that goes through the Variable Load Control Valve, and the Variable Load Valve, not only goes to the brakes, but also to the RPA (Rotary Pneumatic Accelerator) to vary the acceleration as well ;D ;D ;D oopppsss  |
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mrfs42
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Post by mrfs42 on Feb 20, 2008 0:55:24 GMT
<this may or may not be related - but helps when you're calculating overlaps> 16 bums to the ton.  |
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Post by Deleted on Feb 20, 2008 1:12:14 GMT
In response to the OP, yes, there is a significant difference! On 72s it's not so much the braking as the acceleration. Coming downhill to Charing X we lose an estimated helluvalot of passengers at rush hour. It is VERY noticeable as the train takes off like a rocket. Which can be a bit unfortunate for the unwary as there's a signal 7 cars out and not visible from the platform. |
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Post by District Dave on Feb 20, 2008 8:36:40 GMT
It is a little bad though, I think personally, that if you find yourself in such a situation (as a Driver) the difference between having a SPAD and being very close to having a SPAD (something which will have an effect on you're career) rests on if the train is under warranty, or not! All trains should be set for maximum braking performance. In the best interest of all concerned **Puts Instructor Operator's hat on** I'm afraid that I would take a bit of an issue with you in this. As a Professional Train Operator you should adjust your driving and braking technique to suit both the environmental issues (e.g. low rail adhesion) and the performance of the individual train that you are operating. I would suggest that when you first pick up any train you should use the first couple of stations to assess the individual performance of the train and make any adjustments to your normal technique as are necessary. You should always be driving in such a way as to always be operating the train within its limits (we all know they vary - they always have - it's like two cars off the production line; each will be slightly different) and be ready to react to situations in a controlled and timely manner. This is a bit like the 'that signal always drops off' school of thought that some driver's appear to excercise - yes, signals may often clear as you approach them - until the one occasion that it doesn't! Finally, you are aware that the performance between individual trains is variable, so allow for it! **Removes Instructor Operator's hat** |
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Post by Deleted on Feb 20, 2008 10:59:41 GMT
**Borrows DD's Instructor Operator Hat** I've heard it said that there is no such thing as a good driver or a bad driver and that sometimes spads just 'happen'. This is ball hooks. Yes occasionally signals will go back and someone will go through them. But the vast majority are the result of simple errors on the part of the driver and nothing whatsoever to do with how the train handles or what the conditions were like at the time. Any new train should be put through it's paces before you settle down for the drive. And working on the assumption that 'The next signal is red' is not a bad way to go about things - even if it's probably going to be green! *Removes DD's Instructor Operator Hat** Say, that's quite a nice hat. I should get one sometime. |
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Post by Deleted on Feb 20, 2008 21:09:36 GMT
Have to agree with Dave. Now, where do I get my hat?
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Post by Deleted on Feb 21, 2008 20:01:53 GMT
This is a very interesting read and discussion. Never knew that the acceleration of the train was electronically controlled (at least in the D stock). Thanks for all the input!
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solidbond
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Post by solidbond on Feb 21, 2008 20:51:26 GMT
This is a very interesting read and discussion. Never knew that the acceleration of the train was electronically controlled (at least in the D stock). Thanks for all the input! It isn't electronically controlled - it is pneumatically controlled |
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Post by singaporesam on Sept 22, 2008 13:11:47 GMT
Its been ten years since I touched a D stock, my new toys are a lot more sophisticated and don´t have drivers, however, as I recall the device that uses the variable load valve output is actually a variable load relay and this works with Notching relay to adjust the rate of the RPA in rheo and motoring . So actually it is electrical control in response to a pneumatic input.
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