MaxForce for OR

[edwardk]

Does anybody know what the new MaxForce calculation should be? Originally, weight and adhesion would be used in the calculation, but OR is not using the adhesion line so there must be a new standard since you could operate under simple mode and advanced mode for adhesion.

The same for MaxContinuousForce. I realize Bob is the master in this area because of his knowledge, but there must be a standard formula that can be used to achieve close to realistic results.

[derekmorton]

Continuous Tractive Effort Estimation Formula

I do not take credit for this excellent formula. I found it in a paper by Virginia Tech on Rail Resistance Equations. It is located on page 11.



T = 2650 * (nP / V)

T is Tractive Effort, in Newtons.

P is Horsepower. Remember, the output horsepower, not the maximum horsepower!

V is the velocity (aka speed) in km/hr.

n is the locomotive's efficiency in converting power output to tractive effort. For the F7, I found ~0.72 is best.

[baldwin]

As far as I am aware, the MaxForce line should be the actual HP of the prime mover, no calculation needed.

[derekmorton]

That's MaxPower

[baldwin]

Thanks Derek, I realised that just now when looking at something else. Just put it down to a brainfart moment.

[Erick_Cantu]

The numbers you need are generally on the first page of the locomotive's operator manual, usually under "description." Just enter those figures and you'll be fine. Those figures aren't guesses, they're guarantees. OR does the rest of the work on its own.

Similarly, there is no point in deducting power for accessories. One should only deduct power for transmission losses. The quoted power rating of a locomotive isn't the gross output of the engine, it's the guaranteed output into the main generator (or alternator, as it may be). For example, a 12-567B is rated at 1200HP, but actually produces 1300 gross, and the net power is actually around 1225:



And about 80% of that power will actually make it to the rail. I think that OR takes care of this automatically, but I am unsure if it deducts both transmission losses and accessory load. If it does... add about 100 HP to your max power. If it doesn't, just use the rated output.

[R. Steele]

Erick, there may be a bug in how OR handles the ORTSMaxTractive force curves, in that using them cuts power to the rail by a considerable amount.
Using MSTS eng files by themselves or with ORTSDieselEngines block ( via the Common.inc folder and OpenRails folder) the power at the rail is correct - at Run8 -- up in the 90% range or thereabouts...with the ORTSMaxTractive force curves added to the mix ( in any file configuration) the power at the rail hardly exceeds 50%, if that.
Quite a difference...

But the OP asked about MaxForce --- so these pages should be of interest to all...basic stuff for some, however, a good source.
Well laid out regarding the relationship between Power ( HP or Kw ) and Force ( Newtons or Lbs ).
http://evilgeniustech.com/idiotsGuid...ractiveEffort/

[Erick_Cantu]

Bear in mind that I am working from the assumption that nobody is actually using the tables because there's no real way you can get the data. OR seems to get it pretty close with the legacy MSTS parameters, so I just use those.

[R. Steele]

Bear in mind that I am working from the assumption that nobody is actually using the tables because there's no real way you can get the data. OR seems to get it pretty close with the legacy MSTS parameters, so I just use those.

(my emphasis)

Erick...engmod - post#2 provides the real way to get the data.

Continuous Tractive Effort Estimation Formula

I do not take credit for this excellent formula. I found it in a paper by Virginia Tech on Rail Resistance Equations. It is located on page 11.


T = 2650 * (nP / V)

T is Tractive Effort, in Newtons.

P is Horsepower. Remember, the output horsepower, not the maximum horsepower!

V is the velocity (aka speed) in km/hr.

n is the locomotive's efficiency in converting power output to tractive effort. For the F7, I found ~0.72 is best.

The problem is that after getting the real data, does the OR code incorporate it properly? Probably not, that is being looked into.
The page links I provided, have a link to the Virginia Tech pages which contain the formula...also found on other sites.
Furthermore, the other problem is...many of the MSTS legacy parameters are totally incorrect, unless one has taken the effort to incorporate Bob's work into their trainset. Even then, the better course would be to use as much OR physics as possible, as that does provide better performance.

bandicam 2018-07-07 13-29-15-279.jpg bandicam 2018-07-07 13-28-59-016.jpg

[derekmorton]

Similarly, there is no point in deducting power for accessories. One should only deduct power for transmission losses. The quoted power rating of a locomotive isn't the gross output of the engine, it's the guaranteed output into the main generator (or alternator, as it may be). For example, a 12-567B is rated at 1200HP, but actually produces 1300 gross, and the net power is actually around 1225:

And about 80% of that power will actually make it to the rail. I think that OR takes care of this automatically, but I am unsure if it deducts both transmission losses and accessory load. If it does... add about 100 HP to your max power. If it doesn't, just use the rated output.

Thanks for those figures Erick,
OR needs the gross figure as it deducts Aux load and transmission inefficiency.
I have been adding 120hp to the MaxPower for OR.