Tender weight is included in the incline method as long as you weigh only the locomotive first. Tender weight reduces net drawbar pull available to pull the cars.
Tender weight reduces net drawbar pull by the draw resistance of the tender. That will reduce maximum height of the incline proportionally at the point the drivers begin to slip.
Nobody needs to know the pulling power of a steam locomotive without its tender.
Yes, now you’re hitting on why just calculated by weight assessments of drawbar pull have some real limits. This number is good to know and gets you in the ballpark, but doesn’t help that much is you’re trying to make (and measure) gains in performance,
Traction tires, for example, can positively affect tractive effort. More often, other factors detract from it and thus you want to be able to record via some standardized method with common units the incremental change that would result in solving issues that detract from TE.
While fewer people run steam now, there were lots of things that could detract from calculated TE. Often the use of springing, etc on leading and trailing trucks could detract from weight on drivers. You often needed some way to help things track, but here it was more beneficial on TE to try to add weight to these trucks rather that using springing, wihch would have more effect on TE.
Just some examples, there’s plenty more, including for diesels, that suggest the usefulness of being able to measire TE in units that can then translate between subjects for comparison purposes, etc.
not sure what you’re trying to say
in general, TE is 20-25% of the weight on the drivers, assuming the weight is evenly distributed. just adding weight to the front or back may not have the expected result.
i recently posted the thread “loco modifications affecting weight on drivers - Reading” to discuss when prototypes realized this. weight wasn’t evenly distributed on RDG I-5 2-8-0s built in 1891, but was very even with the I-10s built in 1918.
Yes, among other things, weight and where it balances certainly can affect TE. That’s why simply calculating it acxcording to weight provides a general value, but doesn’t help much in telling you whether it’s best balanced front to back. Then you need a way to measure any tiny improvements or detriments to TE as you adjust things for best balance.
The following will illustrate what Mike is talking about. I took down a few locomotive TE measurements, as follows. Note the wide difference in weight to TE ratios. I’ll add side notes that will also explain the inconsistancies. Recorded weight is of the loco only, not the tender. The tender’s weight affecting TE would only really apply on grades, which I have none. The tender’s rolling r**esistance will have whatever effect it will.
On all locos, I usually let the wheel slip over 1 revolution, and then took the lowest TE. On some they’re pretty consistent, but traction tire ones can vary considerably.
Loco Weight TE TE/weight ratio. Notes
Pocher Genoa 4-4-0 4.77 oz 1.5 min 31.4% Stock weight, stock traction tires. new motor and flywheel in tender, shafted to drivers
Pocher Inyo 4-4-0 8.58 oz 2.6 oz min 30% Same as Genoa, but with a ton of lead weight added.
Pocher "JW Bowker 2-4-0 4.65 oz 1.6oz 34 %? Stock weight, 2 traction tires. Early- motor in tender/steel chasis version. Very inconsistant TE, all over the place.
Bachmann 4-4-0 5.40 oz 1 oz 18.5% Stock weight, stock tt (2)
MDC 0-6-0 switcher 8.1 oz 1.58 19.5% Has plated Mantua drivers with one traction tire. Pretty consistant TE
Athearn SW 1500 10.58 oz 2.75 26% NWSL plated wheels
Mantua 4-6-0 (“Dixie…” 8.88 1.03 11.5% Shiny plated drivers.
Rivarossi 2 truck Heisler 9.04 1.9 18.3% Stock model, no traction tires
Atlas YB Austria GP 38&
Dan,
Great data! Shows how having a scale is necessary to get beyond approximations. While things are flat on your layout, if they weren’t you’d probably be looking at ways to improve the TE on some of those locos, where an accurate scale to measure this would be quite handy.
Hello everybody!
Here it is how I measure the traction force of my locomotives:
https://forum.lokomotiv.ro/threads/tfm-traction-force-meter.15579/
It is a Romanian forum, but images speak for themselves.
Dragos