Completely frustrated with Atlas, Kato pulling and climbing performance

mtntrainman · Mar 24, 2014

Randy has always included lots of data from experiments he has done. I think his data holds merit in a lot of ways. Surely a lot of info to mull over.

That all being said...we all know locomotive weight has a lot to do with traction.

IMHO manufactures should include the weight of their locomotives along with other info they list:

Scale dimensions and details
Directional lighting
DCC / DCC Ready
Blackened metal wheels
Dual flywheel equipped 5-pole skewed armature motor with a low friction mechanism
Factory-installed knuckle couplers
Endrails
Rivet detail
Ready-to-run

Locomotive Weight xx.xx oz.

Of course listing the weight of a locomotive may steer buyers away if its to light. Therefore I dont see many manufactures including that data...unless the thing weights a ton and they are proud of that fact. ;-)

LOU D · Mar 24, 2014

randgust said: ↑

The 'built-in differential' on railroad wheels (and to a lesser extent, the models) is a properly tapered wheel tread and flange fillet. As the wheel goes to the outside of the curve, the wheel gets slightly larger due to wheel tread on the outside, and smaller on the inside, and assists in keeping the wheels from slipping at all. When you hear flanges and wheel treads screeching, that's when it's actually sliding and not keeping up. That, in conjunction with track speed and superelevation, is supposed to keep the cars riding down the middle of a curve; as a track inspector you're always looking at the high and low rail for excessive headwear indicating that speed or superelevation is set wrong; when it's set "just right" you won't see flange shine the upper OR lower rails, but that's the minority of times. On a lot of ex-65mph track on E-L that had been downgraded to 40mph or less, the low-inside rail was just getting destroyed and the high rail wasn't touched because the superelevation was WAY too high to be running that slow. I've seen beautiful multiple reverse-curve track on BN that was PERFECTLY set, and talked to crew that said, yup, 'you hit that curve a 42mph, period, and listen, and it won't make a sound'.

I've seen this on some models; namely my old Kato F's. The wheel treads are too flat on those. and you can actually hear them slipping slightly on curves. That's the only ones I've ever seen do that, and wow, is it evident. Most models have enough taper that they 'sort of' work, you don't realize its working as well as it does unless you manage to see truly flat wheeltreads.

One of the techniques that 'old heads' will use coming downhill is to take a single steady air set on the train and apply some locomotive power to keep it stretched out; doesn't apply to dynamic brakes, but it's a time-honored method called power-braking and has been outlawed by many railroads as it can really beat up brake shoes when used excessively. The physics of a downhill vs. uphill train on curves and engineer braking patterns and methods take most of the 'perfect science' of track and wheel design and throws it out the window.

One of the odd things that happens with tapered wheels is that if you are running through curves too slowly, the drag can actually increase because there's not enough centrifugal force to move the cars 'up' on the curve where they belong, the cars are 'rolling low' and now the wheel taper is actually working against you. If you've ever been on a passenger train on a main line and got a restricted signal, and roll through a sharp curve at low speed, you'll hear and feel all kinds of odd things going on that normally aren't there as the 'design speed' of the curve is no longer effective.
Click to expand...

Randy,I would think all of that goes out the window on model railroads.Yes,I run superelevation,I sand it right into my roadbed,but I doubt many guys bother.Even with it,it's more for looks than anything else.The actual relative speed of a model certainly won't push the car to the outside by centrifugal force,if anything,the probably more than likely get pulled to the inside.And model wheelsets are certainly not consistent,some are just plain flat,others have tapers that are greatly exaggerated.Even if everything else was actually "right",the radii of our turns are usually so tight compared to the real thing,you'd need 25 degrees of superelevation to match everything up,LOL!!! Would look like Daytona...

locomcf · Mar 25, 2014

Anyone who's been in N scale for a while knows that the later LL locos will out pull pretty much any other similar loco. The ones I have are much heavier than my Atlas and Kato locos, and that's no doubt a large part of the reason.

But DON'T overlook the difference in the wheels. Straight out of the box, LL wheels are very grippy, whereas Atlas wheels have a shiny surface and are very slippery. Once you've worn that slippery surface away, your Atlas locos WILL pull more cars. After many hours of running, my Atlas SD24s now pull upwards of 50% more cars than they could straight out of the box.

Regards,
Ron

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Completely frustrated with Atlas, Kato pulling and climbing performance

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