I recognize the smoothing effects of a flywheel for our lit'l motors, my question is: Would doubling the mass of the flywheel, same size, lead to damage to the motor? I realize that the motors have some upper limit of how much flywheel they can throw, but I don't know how close current generation motors are to that design limit. The main objective of doubling the flywheel mass has nada to do with changing the performance of the electric motor. Rather, I'm investigating options for increasing the locomotive's overall mass, improving the tractive effort of the loco in the process.
Traction tyres may help if it is not eqquipped with them already??? In all probability yes adding excess weight to the flywheel could cause premature Motor Damage due to excess stress..
the amount of energy stored is directly proportional with the weight (assuming no speed change), however, i agree with magnat, the extra loads on the bearing surfaces of the motor could lead to premature failure. beast
Bikerdad, I think adding stationary mass to the loco might be better than adding dynamic (moving) mass. Either one will add some stress to the mechanism, but I'm not quite sure how much of a concern that should be. It seems to me that Life-Like uses one motor in everything from their GP-20s (light) to their Erie-Builts (heavy). Same flywheels, though. I'm pretty sure that you can get to a point with flywheels where they are so heavy that they will decrease torque.
Rotating mass is double the weight of stationary mass so maybe you don't need to add too much to the flywheels.
In terms of what goes down to the rails, there's no difference between stationary and rotational mass.
Pete, you are absolutely correct. I think what MK was trying to say is that the flywheel is doing double duty: 1) Adding weight to the locomotive drive wheels for traction, and 2) Adding rotational mass to smooth out drive train performance. Stationary weight accomplishes only #1
I'm no expert, but here's my theory: As long as that flywheel is quite well balanced, it should not change the motor's lifespan a bit, unless it is so heavy that it damages bearings while sitting still.
Mike, thanks for clearing it up. That's exactly what I was trying to say. Sometimes it's kind of hard to type a long winded post here at work. Oh hi boss.........
The purpose is to increase the total weight, or in limited instances, keep the total weight the same by going to a denser, yet smaller flywheel. As we know, space in an N scale locomotive is often at a premium, as in "there ain't any more". One good example would be the decoder installation on an MDC teakettle that removes the flywheel to make room for the decoder. Smaller flywheel, same mass, space for decoder, who's not gonna love that? Any improvements in the motor characteristics are simply byproducts, beneficial, but not purposeful. I suppose I'll have to either experiment or find an electric motor guru.
Balance is another concern when making your own flywheel. Unless you can machine a new flywheel from an existing metal block that had been cast under controlled conditions, you have no guarantee that the density of metal will be consistent throughout the block. If you plan on casting your own block from a heavy alloy like type metal that is inexpensive, readily available, and easily worked, the block could have imperfections that would throw it out of balance. Static balance may not be a problem, but dynamic balance when the motor is spinning at operating speeds would ruin the bearings very quickly. An imbalance of just a few grams could cause bearing failure in short order. That's why model manufacturers normally use brass for flywheels, it is relatively heavy, flows evenly in molds, is easily machine worked, and is inexpensive in mass quantities. I agree with the advice above - add static weight, but don't mess with the flywheel.
A better approach would be to get motorman to make you a gear reduction of say 2:1 or 4:1. and using the same flywheel that came with the locomotive. So the balance issue wouldn't be an issue. What the gear reduction would do is step down the motor speed to the worm, The motor however would turn twice the revolutions, or in the case of 4:1 four times the revolutions with the flywheel. This increased speed of the motor at lower rpms would enable the flywheel to impart more inertia. The worm would have more torque in the low end for overcoming frictional losses. Far better low speed operation would result. also increased noise unless you mount your motor/gear reduction with an techique that will minimize vibration transmittal to the shell. Some type of rubber coating on the motor frame contact points should help in the noise department.. An example of a commercially made loco with an increased gear reduction is ER models sharks (now Bachmann) they have a top speed of approx 90 mph. Which considering Atlas or Lifelike locomotives is about 20 percent lower for the sharks. Atlas and Lifelike are very close, with top speeds around 110 115 depending on the individual motor, This is LL's and Atlas's current slow speed motor version. On the LL's I'm referring to the split frames, FA's GP's etc. On the E 7 old plastic frame I believe the motor was taxed somewhat too much because of the very large flywheels. To over come that more gear reduction would of helped, but then again would of reduced top speed and created more noise to boot. Why I say the motor was "taxed"? Well all the E7's split frames and PA's I owned seemed sluggish at low speeds. Like the motor was trying to over come the weight, Mind you I like the lower speeds of LL's split frame, and they will pull toasters accross waffle irons. but it one instance where I think the flywheels and lead weight were too much, and not enough reduction for the gearing caused it to be somewhat sluggish, (its the best description I can give) On the other hand ER models sharks are too light, they could probably use alot more weight with the reduction they do have. I imagine they could pull quite a respectable train if they wieghed twice there wieght. Rob
Let me add on to Rob's observations about the old LL plastic frame E-8s. The flywheels were very large in diameter. The output end of the flywheels was connected to the worms with a piece of plastic tubing. The torque must have been tremendous, because I stripped that plastic tubing on all four engines I owned (one or both ends). LL replaced the first two; I used a crimped brass tube on the other two. I also think, though I haven't measured precisely, that the LL split-frames all use the same motor and flywheels. The models I own are GP-20, FA/B-1, FA/B-2, Erie-Builts, and C-Liners. The weight difference between the GP-20 (light) and the Erie-Builts (heavy) is considerable. There's a big difference in their acceleration/deceleration under DCC. I haven't had time to really explore this. The E-R sharks, I've found, really smooth out over time. I'll agree they are light. Doubling their weight might be a challenge, but the motors seem robust enough to add as much as possible. I wish all engines were capped at their prototypes actual top speed! That seems to be happening slowly.
