How fast is your train running? Do you know?

[ginzokid]

I ran across an interesting article yesterday in an old magazine of mine about how to make a "Speed Trap" for your trains to determine the scale speed. I can't believe how simple it is. The formula I'll give you in a minute looks weird, but it somehow takes into consideration the coefficient of friction. Don't ask. Just plug in the numbers and it works. How to make the "Speed Trap": Measure off a level straight section of track a minimum of 2 feet long and mark it with "mile posts" or something. The longer the section you can measure, the more accurate the figures will be. (I am fortunate enough to have a 6 foot section to use.) What to do: Run your train through the "Speed Trap" at the speed you feel is "right" and time it with a second hand or stop watch if you have one. Be sure the train is running at speed before it gets to the measurement area. The Formula: Take the measured distance and divide it by the seconds it took to traverse it. This will give you Feet/Second. Now Multiply this figure by 59.3. The result will be Scale Speed in MPH. The scale of your trains does not matter. The same formula works for all scales. Here are some of my figures. I ran the 2-8-0 through at 9 seconds which gave 6ft/9sec = .666 f/s x 59.3 = 39.5 smph. A 12 second run gave; 6ft/12sec = .5 f/s x 59.3 = 29.6 smph. The Shay and Climax were both run through at 25 seconds; 6ft/25sec = .24f/s x 59.3 = 14.2 smph. I next took a 4 foot section of my N scale test track and tried it with the only N scale engine I have, the Shay. Was I ever off on that one! First run was 5 seconds or 4ft/5sec = .8f/s x 59.3 = 47.4 smph. For a Shay, that was "Rocket" speed. Second run was 15 seconds or 4ft/15sec = .26f/s x 59.3 = 15.8 smph. Now that is better and you can see the comparison between both scales at the slower speed. Just for kicks I figured out the length of time it should take for "A mile a minute" in a 4 foot run; 3.95 seconds. Have fun with this guys and how about reporting any results you get. I learned to slow my trains down. What will you all learn... The Codfadda B-) Try it guys. I think you will find that what you "feel is right" might be a bit fast.

[70novahound]

Wild Child, I have click clacks AND wrist bruises!;) CJ

[ginzokid]

Here's another test you can do with the speed trap. You know that there are different diameter drive wheels on your steamers and diesels. The diesels usually have drive wheels somewhere around 33". Steam engines however, have different size drive wheels. Look at a 2-8-8-2 vs a 4-6-0. The 4-6-0 has much larger wheels. Larger diameter wheels are usually used on fast passenger type locos. The smaller diameter wheels are found on heavy freight engines. Here's the test. Scale the wheels on a diesel, a small wheeled steamer and a large wheeled steamer. Then run the three of them through your speed trap at the exact same throttle setting. That is the important constant here, the same throttle setting. Notice any speed difference? You should. Even in scale. The larger diameter wheels cover more distance with each revolution than the smaller diameter wheels and therefore should be going faster at the same throttle setting. This is not a perfect test because we are dealing with different manufacturers and gearing, but it should give you an idea of what happens in real life. The ideal test would be to use the same model engine and change out the wheels for each different pass through the speed trap. This is just for fun and not a truly scientific test. Someone try it please. All my engines have the same size wheels or I would do it for you, but alas, the CodFadda does not have that huge roster of engines he once had. B-)

[beastranger]

Pete I think that like you said you would realy need an engine that you could swap tires on to do this test. For example the Challenger takes almost half throttle to get moving where the NYC LL consist only takes a quarter throttle. Punk

[ginzokid]

Punk, Well as I said, it was just for fun. We are victims of 3 pole vs 5 pole motors which you have so amply quoted above. Maybe I'll make a test engine if I can find the parts cheaply guess where...but the theory should hold. B-)

[ginzokid]

I actually ran a "cleaner" train around the whole layout today and then did a speed trap with the two "critters". The Shay at half throttle (step 14 out of 28) covered the 6 feet in 21 seconds or 16.9 smph. The Climax at about one third throttle (step 10 out of 28) covered the 6 feet in 30 seconds or 11.8 smph. Try walking 6 feet in a slow 30 seconds and you will see how "creepy" this really is. As a point of info, DCC throttles can be set at 14, 28, or 128 speed steps. 28 is OK for on the road, but 128 will let your engines crawl in the yards like you would not believe. By the way, did you guys know that the average person walks at a rate of 5 mph? No, you can not walk along side the Climax at your normal pace. You have to slow down because of the scale difference. (I just know Mark will ask about this. 😉 ) B-)