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I was just doing some rough figuring, but this can't be right. An empty rail car weighs around 30tons which is 60,000lbs. or 960,000 ounces. HO is 1/87 scale so 960,000 ounces divided by 87 is around 11,034 ounces. Then turning that back into lbs it would come out to 689lbs. !!! This can't be right for what the scaled weight of an HO should be. No I am not trying to find any NMRA standard just was calculating what an HO should really weigh.
RE: Real scale weight of an HO car empty???, calr, Feb-10-04, 06:47 PM, (1) RE: Real scale weight of an HO car empty???, Eagleknight, Feb-10-04, 07:09 PM, (2) RE: Real scale weight of an HO car empty???, calr, Feb-10-04, 08:04 PM, (3) RE: Real scale weight of an HO car empty???, ssw, Feb-10-04, 09:18 PM, (4) RE: Real scale weight of an HO car empty???, Matt Vince, Feb-12-04, 07:34 AM, (5) RE: Real scale weight of an HO car empty???, jtr1962, Feb-12-04, 11:27 PM, (6) RE: Real scale weight of an HO car empty???, Eagleknight, Feb-13-04, 00:10 AM, (7)
When you are talking about scale, there are three different parameters to consider. Length is 1/87 as you indicated. Area is the square of the scale or 1/87 squared which is 1/7569! Weight and volume are both cubic functions. Therefore it would be 1/87 cubed which is 1/658503!Hope that helps you to see your error.Cal Rasmussen Beaverton, OR (My email is in my profile)Columbia Gorge Route (Phase 1-- Uploaded)
Yeah, the HO scale weight of that 60000 lb car would be about 1.46 oz! However a 1.46 oz. HO scale car will spend most of its time off the track because it is too light. There is a rule of thumb for HO scale cars that is something like one ounce per inch of length for proper performance on a layout. (or is it 3 oz plus 1 oz per inch). Most HO cars out of the box are too light.Cal Rasmussen Beaverton, OR (My email is in my profile)Columbia Gorge Route (Phase 1-- Uploaded)
Haven't we forgotten something? FRICTION! HO-scale bearings are much more efficient than 1:1 scale bearings, other internal resistances within the car are also less than scale, and HO cars don't have brakes, hence they tend to roll lest your tracks are dead level! Factor in air resistance to the equation too, and we begin to see that you can't expect a 1:87 model to behave like a 1:1 in any way.The other factors to consider are kinetic energy and momentum. If you double mass both momentum and KE will double (for the same velocity). But we're talking scale speeds, so Velocity is different, and therefore, for two items of same mass, travelling at 87mph and 1mph, the faster object has 87 times more momentum but 7569 times (87 squared) more Kinetic Energy, so it's damn difficult to recreate it accuratly.
>HO-scale bearings are much more efficient than 1:1 scale bearingsActually it's the other way around. Real bearings will roll down a 0.1% grade or better. I've done many experiments with HO bearings. The best consistent performance I've been able to get is a rolling coefficient of 0.004, meaning they will roll down an 0.4% grade. This isn't even as good as my bicycle, which I've measured at 0.003. Most typical HO bearings with delrin trucks have rolling coefficients from 0.005 to 0.01-about 5 to ten times less efficient than 1:1 bearings. In fact, in order to get scale performance, an HO scale bearing would need to have 1/87 the friction of a real bearing, or a rolling coefficient of about 0.00001, because the scale speeds are 1/87 of real speeds, and friction-induced deceleration therefore should be 1/87 of the friction of real rolling stock. This kind of performance is obviously unattainable.>Factor in air resistance to the equation too, and we begin to see >that you can't expect a 1:87 model to behave like a 1:1 in any way.On the air resistance, since an HO train travels at 1/87 the speed of the real thing, and has 1/87² of the frontal area, the air drag is 1/87^4 of the drag on the prototype for a given scale speed. This actually works out well because the mass is 1/87^3 of the prototype, so the deceleration caused by air drag is 1/87 of that experienced on the real thing, but that is exactly what it should be scaled properly. In short, if we could design a wheel-bearing system with a rolling coefficient of about 0.00001 as I mentioned before, our HO trains would indeed coast down properly on a perfectly level track due to the affects of air and wheel drag. However, nothing we can do will make them behave properly on gradients, and for prototypical acceleration you would need a ridiculously low-powered motor. Because of the scale ratio, an HO train will have a scale acceleration(or deceleration) of 87 times what the real thing would on a given gradient. Nothing can overcome this except reducing gravity. The long and short of it is that the only way to produce realistic performance with HO models is the have a powerful enough motor that the speed of the train is basically controlled solely by the voltage to the motor, and then to mimic acceleration/deceleration rates electronically. I've built a fair number of circuits which do this, including one which holds the speed even on gradients so that you don't get the stupidly rapid deceleration/acceleration that occurs whenever a track grade changes.Very interesting topic, BTW.
Well the motor could not be direct drive either if you wanted to mimic the real thing. Because with the motors being direct drives that is part of the issue of acceleration speeds.
