Weird Train Acceleration in Nightlies

[Eddi]

imho, no setting should ever contain any of these words: "realistic", "improved", "new", "better"

[Zuu]

So just make it "Frank's acceleration model"

[NekoMaster]

I think Improved Acceleration is better because its somewhat hard to simulate real life acceleration in openttd.

EDIT : like i just suggested in the Chilli patch pack thread, maybe we should move the air drag stuff to a new option to enable or disable it depending on the set(s) loaded this way sets without proper air drag values can run like they should.

Also, another thing I've found that doesnt work so well, I was using a Genesis from the 2cc set to haul only 5 empty 5th gen bi levels (total weight was close to 400t with 4250 HP and 256knTE) and It couldn't even reach full speed (max speed in the vehicle information window was 177km\h, it couldn't get past 168, the bi levels are limited to 230km\h )

[Alberth]

Why not write a patch that gives infinite accelaration, so trains run at max speed instantly?
It would solve all problems.

[NekoMaster]

Why not write a patch that gives infinite accelaration, so trains run at max speed instantly?
It would solve all problems.

BALRGH! 1) I don't know C+ 2) thats way unrealistic, I just want trains that can actually reach its max speed when it should be able to

[Arie-]

Ok, I've just done some testing in OpenTTD with the 2CC set (may be an outdated version), what you say is correct, but, I understand and agree with the reasons for increasing the effect of HP and TE.
Just, currently the ICE3 is useless: the Shinkansen is more efficient. While it's top speed may be lower, it's lower cost + higher TE + higher HP make it accelerate faster, with the face that a 60+ wagons ICE3 only does like 275Km/h at max[1]. On top of that even then Shinkansens capacity is higher! This is something that may have to be tuned. But I think this is rather something for the 2CC set, the airdrag coefficient of those trains has to be tuned I think, rather than a change to the current acceleration model.

[1] Adding wagons doesn't increase weight, every wagon however does add another 1400 HP or so.

[Lord Aro]

Hmm. My thoughts on this subject:
There seem to be many 'bug reports' regarding NewGRFs that haven't 'yet' set specific air drag values and so can't reach their specified top speed. This makes me reach two conclusions:
1. The 'top speed' should be calculated in game, and not specified by the NewGRF (And, if necessary, after the vehicle has been built (for articulated, loaded or train wagons)
2. The default air drag value is too high, so existing NewGRF vehcles cannot reach their top speed

Just my 2cc

[Arie-]

Yep, now only waiting for a TTDP player that can give insights on the top speeds the trains achieve in that game.

[Terkhen]

2. The default air drag value is too high, so existing NewGRF vehcles cannot reach their top speed

That value can be set as Action 0 property, even to "zero" if desired (no air drag).

[NekoMaster]

I think it would be less of a headache for newgrf coders to include a switch to shut off the Air Drag feature so that the all the new grf coders wont have change every vehicle to incude air drag values just to make the set work with this annoying new feature.

[michael blunck]

@Nekomaster, Arie-, Lord Aro

For me it´s EOD now. There´s too much unqualified commenting from your side, and there has been nearly no reception of other people´s input (including mine) on this issue.

regards
Michael

[Nite Owl]

Boys, this has nothing to do with "air drag". (snip)

I agree with michael that this topic is not going not be resolved here as the developers are not going to make changes unless they believe that something is drastically wrong. This does not seem to be the case in terms of their beliefs on this topic at this time. As for my use of the term "Air Drag" - I had originally thought that this all stemmed from this commit:
--
r20303 -Feature: [NewGRF] Air drag property support for trains and road vehicles. Air drag for vehicles with air drag not set or set to zero will use a default value depending on their max speed.
--
However, further research also reminded me of this update:
--
r21106 -Change: Tuned realistic acceleration to be a bit more realistic in order to make acceleration "slower", which highlights the differences between vehicle types more.
--
So it appears that more than one change was made to the acceleration model in the not too distant past. There may be even more commits as far as the acceleration model is concerned but time does not permit me to research them all. So my "Air Drag" theory could be completely true, somewhat true, partially false, or totally false - only the code, and those that understand it, know for sure.

[NekoMaster]

--
r21106 -Change: Tuned realistic acceleration to be a bit more realistic in order to make acceleration "slower", which highlights the differences between vehicle types more.
--

Well this change doesnt look like its doing what it should, I can understand making trains accelerate slower but like i've said a million times now, this new acceleration code makes it harder for most trains to get full speed (especially if its a passenger train where speed is necessary)

[Arie-]

Ok it took me a while, but finally I got (using an illegal version of Transport Tycoon Deluxe) TTDP working with a settings program thingy and made a test case of TTDP 2.6 r2360 vs OpenTTD r21611 using UKRS. Train would start in the depot at the bottom right and where a certain speed was achieved I build a road. In OpenTTD the train did not accelerate beyond 130MPH and even that was somewhat beyond the 140MPH mark in TTDP. Attatched: the savegame in TTDP after the first test run and the OpenTTD screenshot after the second test run.

edit: oops I did not check the multipliers in OpenTTD, I've understood that TTDP is 5* and 5%, checking whether I didn't make an error.
edit2: OpenTTD savegame attached as well, I think I didn't do anything wrong.

[NekoMaster]

Im still having problems with this stupid new acceleration code. I tried using a Budd RDC from the 2cc set and NARS v2.03 and both struggled to get their full 85 MPH speed. Also, I tried setting up a TEP60 with only 7 empty passenger cars and its chugging along at 85, unable to reach its full 100MPH.

Another example, 2 Sharknoses from the 2cc set, plus 2 4th gen mail cars and 8 4th gen regional passenger cars. The train should be able to reach 87 MPH but chugs along at 80 MPH because of this stupid acceleration code.

This code is really inconvinent in that because most sets haven't been adapted for this code yet, it makes it hard to run express passenger and fast freight services.

[michael blunck]

Im still having problems with this stupid new acceleration code. I tried using a Budd RDC from the 2cc set and NARS v2.03 and both struggled to get their full 85 MPH speed. Also, I tried setting up a TEP60 with only 7 empty passenger cars and its chugging along at 85, unable to reach its full 100MPH.

Another example, 2 Sharknoses from the 2cc set, plus 2 4th gen mail cars and 8 4th gen regional passenger cars. The train should be able to reach 87 MPH but chugs along at 80 MPH because of this stupid acceleration code.

This code is really inconvinent in that because most sets haven't been adapted for this code yet, it makes it hard to run express passenger and fast freight services.

For the umpteenth time: Sets cannot "adapt" to it. Setting the air drag factor would be useless for the examples you are giving (130 km/h, IMO). Air drag factors only come into play for high velocities (i.e. the ICE problem: 280 .. 330 km/h).

That very weak acceleration is a "feature" of the new acceleration code (see post by michi_cc). I´ve set up a test game under r21464 yesterday and acceleration is indeed much slower than in the past, without taking air drag into account, i.e. even for slow (freight) engines.

Michael

[peter1138]

In r21106, the an arbitrary factor for air drag changed from 10000 (20000 for maglev) to 500.

At the same time, internal units for acceleration were changed from mph to km/h-ish, so many other arbitrary factors were changed.

For NekoMaster's last example (orange is max speed, purple is speed achievable):

Pre r21106:


Post r21106:


TTDPatch:

[PikkaBird]

Haven't tried the latest version yet, but I must say I like this new acceleration model. It really makes the difference in HP between locomotives more meaningful (and I'm fine with an underpowered loco with a heavy train not reaching "top speed").

[Rubidium]

The new acceleration model was basically introduced due to http://www.tt-forums.net/viewtopic.php?f=33&t=50739 which complained that OpenTTD's acceleration was too fast. However, the graphs as plotted by petern show that OpenTTD's realistic acceleration has always had a lower top speed and more resistance while the force was roughly equal.

OpenTTD calls UpdateTrainSpeed (which basically applies the acceleration) twice per tick. Some historical digging in OpenTTD shows this has basically been always the case, so I'm wondering whether TTDPatch might be calling UpdateTrainSpeed only once per tick. Or does TTDPatch half the result of the acceleration function before applying it to the consist?

On the other hand, TTDPatch's formulae are (as far as I can see from the comments) based on Imperial units instead of SI units. So maybe that's causing the difference between the used acceleration value from both acceleration formulae?

In any case, michi_cc has changed some constants so please test the binaries at http://devs.openttd.org/~rubidium/cf/h37d5ee14/ to let us know whether this is better, but still not too fast.

[Uwe]

I just checked this binary, using the DBSetXL with freight multiplier=5 and slope steepness=5%. To me, it looked quite good. Years ago I made a weight table for DBSetXL and TTDPatch (Download here), and the trains behaved quite similar. That is, going over the limits given in those tables resulted in trains not being able to reach their top speed, staying well below the limits gave good acceleration, and running at about the maximum loads for full speed resulted in slow acceleration, but the trains reached top speed eventually. I tested this with some of the early steamers and electrics, but also with the fast BR 05, which is only capable of hauling light express trains at top speed. I did not test the other versions where problems were reported, though, so I cannot compare them.

Regards,
Uwe