Junctionmad

Didn't want to side track debate in to dcc throttles. I wanted first to understand the way a vacumn train brake was used in real life before seeing if it could be transferred across to dcc

Ejectors aren't used on diesels , rotary exhausters were. I dont believe any vacumn brake was proportions, mike84c account confirms that. As long as the valve is open the vacumn brake will continue to increase brake force at a rate determined by the setting of the brake valve/lever . To hold a given brake force the brake lever would be returned to running . This confirms my memory. Of the drivers of 141 ,who would work the train brake on and off , because otherwise leaving the brake lever partially on would result in increasing brake force and a hard stop. On steam locos the large injector was needed for brake release. On diesels typically the exhauster was either electrically or mechanically drive. Which is why I always understood the notch up on stopping of the EMD, this was presumably to exhaust the vacumn and begin the brake release process.

Thanks for the pic , What I trying to ascertain , is that the train brake on a vacuum equipped diesel was or was not proportional , as conventional steam vacuum setups did not have promotional braking, proportional braking is where the force of the applied brake is directly related to the position of the brake lever. with the Independent ( loco) brake , this WAS a proportional system , primarily because it was not fail safe. On a vacuum system , the position of the train brake lever adjusted the rate on the admittance of atmospheric pressure air into the train pipe. hence it was proportional to the rate of air being admitted , but not the application of brake force, but Railer suggested it was proportional and I cant see how that was arranged technically My reasoning for this , is I an programming a new version of MERG dcc throttle and I want to see if I can make the brake lever idea work in DCC dave

Indeed and I think here, many people are mixing air with vacumn and getting confused Vacumn systems got introduced in uk and Ireland , because firstly , the issue of very long trains wasn't as prevalent , the vacumn was simpler all round and suited steam based exhausting via ejector which has no moving parts. In addition at the time, the air brake could not be partially released and this was seen as an issue for the typically faster UK railways. As speeds built however the brake force needed also increased and vacumn ran out of puff Still my question , I don't beleive vacumn brakes force application were proportional to the position of the lever

I think people are mixing up air and vacumn brakes , even Rebelred is, because vacumn bakes operate at low negative pressures around -.7 ( point 7) bar or , and not at +5 bar which is the air brake . Vacumn is by definition maxed out at -1 bar How did it do that , that's not the classic operation of a train vacumn. brake , typically all that happened is you admit air to the train pipe. If you keep admitting air the vacumn keeps getting destroyed , my understanding is leaving the valve lever open ,brake pressure would build. Closing the valve but not engaging the vacumn exhauster ( ie release ) would cause the brakes to remain on , at the current vacumn level. hmmmm , ??? Say you needed 10 " of vacumn , you would open the brake valve until the train pipe vacumn gauge showed that vacumn , the. Shut the valve, if the exhauster was not engaged , the vacumn would remain at that ( less leakages ) , is this not the way it works on the GMs vacumn train brake Note that you are correct in your description of the independent air brake. It's a graduated system , because it's not required to be fail safe. ( ie the same as loco steam brakes etc ) I was specifically referring to train vacumn brakes Note that vacumn is measured in negative bar , millimetres or inches of mercury etc , so , typical train vacumn is low around - 20 inches of Hg , -.7 bar. Full vacumn -1 bar Blended brakes , are a form of interaction of dynamic braking and air brakes and would have been disabled on Irish EMD locos. Bailing off , or bail off , was a /is technique to release the loco brakes while keeping the train brakes on. Historically loco brakes , whether steam, air or vacumn were " servoed " to the train brake, with a small delay to mitigate bunching , bail off control overrode that by allowing the loco brake to be released ( some or all ) while keeping the train brake on. It was available in many steam locomotives by releasing steam pressure in the loco brakes. , but I'm not aware of the extent of that control on Irish EMD vacumn braked systems Ps presumably one of the gauges on Irish EMDs on the console was a vacumn gauge which wouldn't have been fitted to US EMDs

Thanks my understanding is that as the vacuum brake is applied it merely controls the rate of brake application rathe then then pressure of brake application , maybe I'm wrong here. Ie if you leave the lever partially on , the brakes will continue to build pressure on the wheels , is this the case ? dave

no comments ?

while this is positive , it doesn't explain why the success story of ballina isn't being replicated elsewhere

There is at least a railway station still vaguely in rosslare at least

We could do with some of that reverse cascading down here in wexford

What's the one in Belfast Amazingly these things are coming out of the woodwork !!!

this reminds me, how come IE can make Ballina work as a freight depot and basically no where else !

yeah but they are pure sh1te, imho and should never see the light of day on intercity trains

My own view is if passanger numbers increase ie will be forced to implement some additional loco hauled services , abs we could witness the absurdity of them purchasing carriages on the 2nd hand market

I was reviewing some stuff on vacuum and air brakes I was trying to relate the standard US control stand to the brake controls on the 141 GM The black brake lever was the train brake and the red on e, was the independent brake ( i.e. train brake ) The black one had the typical release position ( vacuum being generated and the vac pipe being emptied ) , Then it had a full service , which was typically the full application of the brakes , Normally vacuum brakes had a " run " position , i.e. no vacuum being generated and the driver typically moves the lever from "run" to full service to modulate the train brakes I notice that on the independent brake ( which I presume is air operated ) there is an additional position in front of " Release " which is on a spring detent, This is described as " Release Auto " IN most US controls stands the air brake has 5-6 positions on detents, including release, running , lap, full service and emergency Looking at various videos , and from memory the 141 drivers, brought the brake lever to the mid position and then back to release and modulated the brakes that way, full service only being applied at the very end . Was it that the brake positions just weren't marked on the irish GMs ? in the US, there is the concept of " bailingof, or Bailofff" i.e. applying the train brakes whilst leaving off the loco breaks to avoid snatch and jerk. Since the normal way train brakes work is the the train brake lever also activates the engine brakes , did Irish GM engines not have Bailiff control? The other aside is that on most GM engines there is a amp/power meter , yet I dont think this was every fitted to Irish locos for a treatise on how it worked on steam https://books.google.ie/books?id=1w8TAwAAQBAJ&dq=steam+locomotive&hl=en&sa=X&redir_esc=y&output=reader&pg=GBS.PA163 you can knock yourself out on technical detail !!!!! Dave

That would explain things when I try to contact you !

Thanks , thats an interesting one , my google search terms didnt throw that one up

max size is 900mm by 300mm I am looking at a cell based plywood open frame baseboard design , so I need to cut internal openings etc , best done by laser

I've a friend that writes watch apps , theres interesting stuff in the works , bus as you say , most of it can be done with the iPhone anyway I'm writing this slowly so the forum software can keep up lol

Does any know of a service to laser cut ply in Ireland ? Thanks Dave

John would also consider rerunning the 4wheel van if he had sufficient interest , personally Id buy two, ( the 4w were far more prevalent then the 6w)

Nice models. Maybe it's the light but I agree with Richie , the tumblehome looks odd , makes them look very American

I hope John re-releases the 4w vans as well

Will the irm bubbles be available in orange ?