Dynamic brake vs Air brake.

[edwin_m]

Using the DRA may inhibit the rheo\regen brakes.

The Driver's Reminder Appliance was intended to be operated only when the train was standing at a platform against a red signal. Where retrofitted to existing trains I believe this was done by wiring it into the traction interlock, and when operators started mandating its use on the move then this would most likely disable the whole traction package including dynamic braking. DRAs on more recent designs (essentially post-privatization) would have been fitted from new so may be a bit more clever in that respect.

 

[aleggatta]

Using the DRA may inhibit the rheo\regen brakes.

It does on electrostars, however I think there was a change to driving guidelines following the realisation that dynamic braking was being isolated through this and excessive pad wear was resulting of it

 

[365 Networker]

Has Great Northern been reading my messages? I've found a video of a 365 at Peterborough with all driving cars using Dynamic Braking! Video is from Saturday 12th October - Skip to 13:40:-

Perhaps Hornsey are finally fixing the dynamic brake, as I have not seen a 365 with all driving cars using the dynamic brake for a very long time!

 

[Philip]

I can remember when the 175s had the retarder working, it would often be in use under one coach but not the others. Any reason for this and is this common on other DMUs with the system like 185s/Hyundai Rotem 22s?

You get a good blast of the 185 retarder noise when braking in Cowburn tunnel for the SP speed restriction heading east; engine revs and then a wind tunnel kind of noise.

 

[craigybagel]

I can remember when the 175s had the retarder working, it would often be in use under one coach but not the others. Any reason for this and is this common on other DMUs with the system like 185s/Hyundai Rotem 22s?

Probably just that early 2000s reliability that Alsthom were renowned for at the time! The hydrodynamic brake was/is fitted to all vehicles on 175s.

 

[jamesst]

I think it depends on the depot you work at aswell. At my toc 99% of drivers work with dynamic, at another depot (same toc) the majority of drivers isolate it.

 

[AlfaPendular]

Sorry for bringing up this old Thread, but I am trying to model some dynamic brake curves. I am looking for figures to complete some parameters.

Can anyone provide with fade speeds of classes that still use dynamic braking? I think I saw a 10 mph for class 377, is it generic or depends on the train class?
(I am considering fade speed as the speed that pneumatic braking is started to compensate for the performance of dynamic brake at low speed.)

Thank you

 

[bramling]

They used to isolate dynamic brakes in leaf fall season, perhaps they still do?

Also I believe they are generally set-up so that the friction brakes will give a slightly better level of retardation than the dynamic brakes under the same brake demand.

That's interesting, as it's generally regarded that rheostatic braking gives a better brake effort than friction braking on trains where they're supposed to be comparable. Hence on LU why an ATO train running on friction brake only can sometimes find itself having minor overshoots. So it wouldn't surprise me for some setups to have friction braking effort set to over compensate for this.

 

[hexagon789]

That's interesting, as it's generally regarded that rheostatic braking gives a better brake effort than friction braking on trains where they're supposed to be comparable. Hence on LU why an ATO train running on friction brake only can sometimes find itself having minor overshoots. So it wouldn't surprise me for some setups to have friction braking effort set to over compensate for this.

It may not be the case, but I was informed that rheostatic/regenerative braking systems were always set up so that the friction brakes gave slightly better retardation