OR Steam Exhaust New Changes
#301
Posted 05 July 2017 - 09:48 PM
Articulated (and some duplexes like the Pennsy S1) locomotives with twin stacks were often arranged so as to provide a separate stack for each pair of cylinders. This means that when the engine is in operation, instead of both stacks puffing at the same time, you get a distinctive alternating puff sequence. The main factor determining this is the difference in crankpin angles on both sets of drivers. For example, if the front set of drivers is closer to its "usual" 90-degree puff interval than the rear drivers, the front stack will puff first before the rear stack does.
The only operating twin-stack articulated as of today is UP 3985, but I have not seen any videos that make the alternating puff timing apparent, so I have taken the liberty of making a reference video using a simple (but crude) model in Blender to demonstrate what the puff timing looks like in various scenarios, including the effect of wheelslip on one set of drivers. Here's a still from it:
http://i.imgur.com/XIMEK0C.png
I won't be posting this to YouTube, since it's intended solely for the benefit of the ORTS development team, but if any deleopers are interested please PM me.
It should also be noted that even on articulated/duplex locos with only a single stack (provided they're either simple expansion or compound Mallets starting from a stop in "simple" mode), the same puff timing scheme holds true. The only difference is that, obviously, all puffs are coming out of only one stack.
And I know I'm getting ahead of myself...
...but it would help of both sets of drivers were part of the same .s and .eng files!
#302
Posted 04 February 2018 - 12:26 PM
Brandon
#303
Posted 05 February 2018 - 12:39 AM
Also you would need a sound set with two independent engines as well - not sure if you could match them well to the wheels in the animation or make them go slowly into and out of synchronisation - it seems like a difficult thing to achieve.
#304
Posted 05 February 2018 - 11:15 AM
Drive wheel sets on a steam engine like a Pacific K4 cannot get 'out of sync' as the left and right side are joined by a solid axle. The drive wheels are precisely timed so the drive rod pinyons are 90 degrees apart from drive wheel on the other end of the axle. 'Quartered' is the term.
Many MSTS steam engine models I notice do not have properly quartered drivers. This is nothing more than a modeler either not understanding how it's done is pure lazyness or inattention to prototypical modeling. These 'models' I consign to the trash bin on the theory that if the modeler does not care how an engine looks then I consider it junk.
A compound (or dual?) engine with two sets of drive wheels and cylinders is actually two steam engines sharing a single boiler. The 'Challenger' is an example.
So a single engine, lets use a Pacific K4 type, can never get 'out-of-sync'! If it did it has a very serious problem.
An engine like the Challenger can get out-of-sync as it's actually two engines. How to model sounds for that is a poser.
Maybe the answer is the engine 'chuff' sounds linked (synced?) to drive wheel diameter and speed?
regards,
vince
#305
Posted 06 February 2018 - 10:19 PM
darwins, on 05 February 2018 - 12:39 AM, said:
Also you would need a sound set with two independent engines as well - not sure if you could match them well to the wheels in the animation or make them go slowly into and out of synchronisation - it seems like a difficult thing to achieve.
I am only referring to engines with TWO smokestacks. It was a common practice on some latter-day articulated steam engines to provide s separate smokestack (chimney) for each pair of cylinders.
When the engine is in operation, and angular difference between the crankpins on both the front and rear drivers is 0, 90, 180 or 270 degrees, then both stacks will puff at the same time. If the angular difference is anything else, then instead of both stacks puffing at the same time, the puffs will alternate between the two stacks.
Since a two-cylinder simple rigid frame engine "puffs" whenever the crankpins reach, say, 3, 6, 9 and 12 o' clock, then all it means that if the crankpins on the rear set of drivers hit say, 3 o'clock before the crankpins of the front set of drivers do, the rear stack will puff first before the front one does.
PM me if you wanna see my video, it'll explain it better.
#306
Posted 08 February 2018 - 04:26 PM
Brandon
https://www.youtube....h?v=EEZpqh__t0o
https://www.youtube....Q9G-VzN8&t=146s
https://www.youtube....h?v=kF-k_bNI9xA
https://www.youtube....h?v=HAwYZHtaack
https://www.youtube....h?v=AFNF1v9s-J8
https://www.youtube....hEce1Wwo&t=945s
https://www.youtube....fxYut4MXgI&t=4s
https://www.youtube....h?v=yjXOiHkeOC8
https://www.youtube....h?v=lmrJ3wiY0nM
#307
Posted 09 February 2018 - 12:27 AM
Cheers Bazza.
#308
Posted 09 February 2018 - 02:30 AM
Personally I am not really fussed about linking exhaust chuff to cylinder movement, that takes up processing power that can be used elsewhere such as linking the cylinder pressure relief where used to the cylinder movement and adding some velocity to the steam from the cylinder drain valves. They will both need their own set of code for particle movement because they are both completely different to the normal exhaust and different to each other.
#309
Posted 11 February 2018 - 11:55 AM
Brandon
https://www.youtube....LjO-13E8&t=318s
#310
Posted 23 February 2018 - 04:21 PM
Brandon