Eng Files for USA diesels Looking for data...
#22
Posted 15 August 2021 - 04:24 PM
R H Steele, on 14 August 2021 - 10:12 PM, said:
My understanding is that in the real world starting TE (MaxForce) is not capped as such, it could reach a much higher value. The MaxForce value is the typical "design" value when wheel slip may start to occur, and hence in practical terms the locomotive cannot produce a greater value of starting tractive force (otherwise wheels start slipping, and the locomotive won't move).
OR caps the MaxForce to the value set by the user, however the performance of the locomotive is also dependent upon the adhesion of the locomotive. Hence if the MaxForce exceeds the Adhesive force (related to adhesion) then the locomotive will not be able to exert its full starting TE.
#23
Posted 19 August 2021 - 02:10 PM
Traindude, on 14 August 2021 - 05:06 PM, said:
The minimum speed for the ORTSMaxTractiveForceCurves I've constructed is set when Notch8 attains maximum Tractive Effort. Other power settings lower than 100% will also attain this MaxTE, however, it will be at a lower speed. The lowest speed of each notch is zero m/s, Hopefully the OR interpolator will generate the correct tractive effort for each notch for speeds that fall below the minimum speed down to zero.
Two possible problems: Does the OR interpolator work properly in this instance? (I'm assuming – yes ) ...and...That I've capped the maximum for each notch...I'm not entirely positive that presents no problems. Especially since steamer_ctn in post#22 provides this information:
steamer_ctn, on 15 August 2021 - 04:24 PM, said:
OR caps the MaxForce to the value set by the user, however the performance of the locomotive is also dependent upon the adhesion of the locomotive. Hence if the MaxForce exceeds the Adhesive force (related to adhesion) then the locomotive will not be able to exert its full starting TE.
I'm working on refining the curves and this is something I'm going to work on. Additional speed points below the minimum already given in the curves may be necessary ( especially if the OR interpolator does not apply to this case )...knowing more about the interaction between MaxForce and Adhesive Force will be helpful. Sources –- anyone?
Traindude, on 14 August 2021 - 05:06 PM, said:
I'm assuming the spreadsheet example was for an EMD E8? If so, that brings up another question I have. The E8 is listed as 2250hp –- power delivered to traction motors. My understanding is that rail horsepower is used to calculate tractive effort.
One item that would help me is to have an example of the “light consist” that gave you problems starting --- locomotive/s, number of cars, and total car mass, grade...that would help me test. The starting problems could be from other factors that neither you or I have thought of. I would like to try and duplicate your experience so I could refine my testing.
#24
Posted 19 August 2021 - 02:49 PM
https://i.imgur.com/BuoLkFk.png
The habit many OpenRails creators have of limiting the tractive effort curves to not exceed the adhesion rating of a locomotive is outright wrong and I abandoned that practice in my physics set months ago. I'm pretty sure this practice came about as a crude way to reduce wheel slip (since, ya know, wheel slip protection isn't simulated and every time it's proposed there are just excuses and workarounds proposed instead of actually solving the problem), which is fair enough, but we shouldn't go telling ourselves this is realistic.
#25
Posted 19 August 2021 - 03:49 PM
steamer_ctn, on 15 August 2021 - 04:24 PM, said:
This is true for the first generation diesels as they had no control of current.
The second generation with electronic controls ( sd40-2 and later ) did limit the starting current. I don't know when GE started electronic control.
#26
Posted 21 August 2021 - 12:10 AM
R H Steele, on 19 August 2021 - 02:10 PM, said:
I'm assuming the spreadsheet example was for an EMD E8? If so, that brings up another question I have. The E8 is listed as 2250hp –- power delivered to traction motors. My understanding is that rail horsepower is used to calculate tractive effort.
I am using the "rated" 2250hp as a basis for my spreadsheet. So the formula for the E8, as described in the specification card would be:
(308*(2250hp*(throttle notch/8)))/mph
R H Steele, on 19 August 2021 - 02:10 PM, said:
One item that would help me is to have an example of the “light consist” that gave you problems starting --- locomotive/s, number of cars, and total car mass, grade...that would help me test. The starting problems could be from other factors that neither you or I have thought of. I would like to try and duplicate your experience so I could refine my testing.
In this case, I was using first a single "A" unit (148.4205 short tons), and then an "A-B" set (292.7076 short tons combined) of Richard Cowen's repaint kits and 5 of midneguy's Burlington heavyweight passenger cars--one RPO (69.9 short tons) and 4 coaches (76.2 short tons each). The total tonnage of the passenger cars is therefore 374.7 short tons. All .eng and .wag files were modified from their original versions for experimental purposes. This is all on a flat grade on CTN's test route, specifically the "Level Path Over Water Trough" path (SW corner to NE Corner).
Without my modifications of the added low speed steps, the train would not move when I moved the throttle from idle to notch 1. It was only when I advanced the throttle from notch 1 to notch 2 did the consist start to move--and that's at the start of the run!
My modified .eng and .wag files, as well as the .con files, are available via PM.
#27
Posted 21 August 2021 - 05:53 AM
#28
Posted 21 August 2021 - 11:28 AM
darwins, on 21 August 2021 - 05:53 AM, said:
And there's another assumption everyone seems to make that's outright wrong. Notch 1 is not 1/8th power, notch 2 isn't 2/8th power, etc. It's not directly proportional by any means, for the exact reason that applying 12.5% power in notch 1 would be far more than anyone would want for a light engine.
In general, the power grows under-proportional per notch...climbing very little at lower notches but increasing significantly in higher notches, while the starting tractive effort (ie: the motor current limit) increases over-proportional with each notch...climbing most in low notches but leveling off in high notches.
#29
Posted 21 August 2021 - 11:39 AM
Quote
I am very relieved to hear that.
Could you give me some idea of the approximate % of full power that the 8 US throttle notches might correspond to?
#30
Posted 21 August 2021 - 04:54 PM
darwins, on 21 August 2021 - 11:39 AM, said:
Could you give me some idea of the approximate % of full power that the 8 US throttle notches might correspond to?
Varies a lot per engine, but for something modern you might be looking at like 6% power in notch 1, 13% in notch 2, 28% in 3, 39% for 4, 52% in 5 (note how we didn't even reach half power until after notch 4), 69% in notch 6, and 84% in notch 7. Older locomotives may have the power curve even more biased towards the higher notches, and this curve would be pretty relaxed in comparison. The point being, there is no one size fits all for notch-by-notch power output.