I HAVE A PAIR OF ATLAS GP-7'S IN TH&B COLOURS. NOW #73 IS VERY FAST WHILE #76 IS VERY SLOW. I ALSO HAVE AN ATLAS CP- GP35 WHICH IS MEDIUM. I CLOCKED THEM ALL. #73 TAKES 11 SECONDS TO GO AROUND MY TRACK AT 40 MILES AN HOUR, #76 TAKES 15 SECONDS AND THE GP35 TAKES 13 SECONDS. THEY LOOK GOOD MU-ED TOGETHER. MY QUESTION IS. DO I RUN THEM SLOWEST TO THE FASTEST OR VISE VERSA? RIGHT NOW I HAVE THE GP35 FIRST, #73 SECOND AND #76 LAST. MEDIUM IS FIRST, FAST IS SECOND AND SLOWEST IS LAST. WILL I COUSE DAMAGE TO THE FAST ENGINE IF I RUN IT FIRST? WITH MY KATO'S, I DON'T SEEM TO HAVE THIS PROBLEM. THEY ALL SEEM TO BE EVENLY MATCHED. MY RS2'S THAT HAVE BRAND NEW MOTORS IN THEM, (REPLACED FOR FREE BY KATO) ARE EXACT. SD90 AND SD40 ARE EVENLY MATCHED. MY ATLAS TRAINMASTERS ARE NOT EVANLY MATCHED, ONE IS FASTER THAN THE OTHER. SO IS IT FAST FIRST OR FAST LAST IN AN MU SITUATION?
I don't know if there's a scientific answer for this one, but I have several A-B combos and on most the A is just a little slower than the B (perhaps because of the light?). I generally will run a slower GP, etc., in front with the faster behind it to prevent uncoupling on grades. If there is too big a difference in speed, I will not run them together at all. If the speed difference is minimal, I don't worry about it. I've been at this since the late 60's and haven't burned out a motor by double or triple-heading yet.
There seems to be a general rule within our NTrak club to run the fastest in the lead. Keeps the couplers nice and straight!
THANKS GUYS FOR THE REPLY. SO RUNNING THE FASTEST FIRST WON'T PUT STRAIN OR UNDUE STRESS ON IT? IT WON'T BURN OU THE MOTOR BECAUSE IT IS WORKING HARDER? OR IS IT WORKING HARDER?
Pour yourselves a cup of coffee, a glass of wine, a cup of tea, or a glass of scotch and sit down and think seriously about the subject of MUing engines that run at different speeds at the same transformer throttle setting. It doesn't really matter whether the fastest running engine is at the front of the MU or at the back. If the faster running engine is at the front, then it is trying to pull the slower running engines and if you could put an ammeter on that engine's motor you would find that it is drawing a lot more current than the slower running engines behind it. HEAT KILLS! Contrarily, if the faster running engine is behind the slower running engines, then it is trying to push them...SAME STORY...HEAT KILLS! That engine's motor is still drawing a lot more current. An MU of this nature is working somewhat like dynamic brakes do, but instead of using reverse electrical power to slow the motor you are using the whole motor of another engine, or engines as a brake. That is hard on the motors of all the engines. The fastest running motor is trying to pull the slower ones and the slower ones are trying to brake the fastest running one. You will find that the fastest running engine's motor will start to get warmer than the others if you run it in this configuration for any considerable length of time. In all probability the short length of time you may be MUing different engines with different running speeds on your home layout, would not impact seriously on the survivability of the engine's motor, or specifically it's brush wear. However, if you are MUing engines at a train show and the MU setup is going to be running for a long period of time for a display, then it would probably be a good idea to pick engines with the same running speeds for that type of continuous operation. From an electrical engineering standpoint, MUing engines that run at different speeds at the samre throttle setting, is not really good for either engine. Whether they are N scale or full size. The first impact point is the motor brushes because they are bearing the current load. What I did with my three F3A units and my four F3B units, when configuring them for MUing, was space them evenly about 6" apart and run then around a large circuit of track all at the same time. I removed the faster running ones and turned them around so that they were running backwards in the same configuration, just to see if they would run at a different speed going backwards. A lot of them did. So I just turned the shells around and marked on the bottom of all the engines which units should be MUed together. Of course this switcherooo is not possible on the newer diesels that have specific cab positions on their chaassis. So, if you can't do that or don't want to go to all that trouble, then just MU the engines for about 30 minutes and feel each individual engine for heat. Then remember to MU the hottest ones and the cooler ones together.
As an adendum Jerry, to your question about MUing engines, I think we've just discovered how you ended up with fried motors on your Kato RS-2's.
GARY, I THINK YOU MAY BE CORRECT ABOUT THE TWO RS-2'S, ONE ALWAYS RAN FASTER AND HOTTER. ALSO THEY WERE DEMO'S AT THE SHOP WHERE I BOUGHT THEM AND I THINK THEY DID HAVE ALOT OF RUNNING TIME THERE BY ONE OF THE N-SCALE GUYS. OH WELL I HAVE NEW MOTORS, SO THAT'S GOOD. I LIKE YOUR IDEA ABOUT REVERSING THE SHELL. I THINK IT IS POSSIBLE ON THE GP-7'S. I WILL TEST IT RUNNING BACKWARDS AND SEE WHAT SPEED THEY RUN AT. IF I CAN'T REVERSE THE SHELL, I CAN RUN IT BACKWARDS IN AN MU. THANK YOU ALL FOR YOUR REPLYS, KEEP THEM COMING..
OK GUYS!! NEW FINDINGS!! GARY WAS RIGHT, MOTORS CAN RUN FASTER OR SLOWER IF THEY ARE REVERSED. NOW #73 WHICH IS THE FAST ONE, RUNS SLOWER IN REVERSE. #76 RUNS FASTER IN REVERSE. SO I WILL ALWAYS RUN ONE FORWARD AND ONE BACKWARD AND THEY WILL BE EVAN. I CAN'T REVERSE THE SHELL, BECAUSE THE TANK WILL BE BACKWARDS. SO BY RUNNING THIS WAY AND REVERSING THEM OCCASIONALLY, THE MOTORS WILL GET EQUAL TIME RUNNING BACKWARDS AND FORWARDS. THANKS GARY!
