Thanks for your explanation, Randy. I am not conversant, or hardly so, with electronic devices, including electric motors, so I accept your statement that the motor becomes just as powerful a brake to itself as it is a motor when the circumstances in the circuit change...as in a short. I hadn't considered that.
-Crandell
They'd pretty much do that regardless of how much energy the flywheels could store for the reason I mentioned above. While spinning, the motor generates power. When there's no load, it spins freely, but if there's a short, the motot has to work against a lot of force, so it stops almost instantly. It's the same basic way dynamic brakes work. Or if you have a portable generator, notice the difference between it runnign with no load connected and then loaded down. Since physics doesn't scale down, it's not too practical to implement a variable dynamic braking in HO scale, however I've always thought that in O scale or larger you could do it, using spur gear drives or a better ratio worm (yes, it is possible for the worm gear to turn the worm) and a large heavy flywheel. Something like that should coast a long way when the power is cut - expecially down hill. Switch in a resistor across the motor and you'd get a braking effect without instantly stopping it, with the weight of such a large loco, even shorting the motor leads wouldn't make it stop instantly.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
CSX Robert Why would you want the engine to run another two or three inches?
It would be concrete evidence that it is worth the additional cost of their engineering and manufacture. So far, I don't see how they contribute much, even to the smoothing out of the drive performance. It doesn't seem to work for so many HO models that stumble and jerk, with or without BEMF. But if the devices really were worth their place in the frame, they'd make a locomotive coast, albeit decelerating, about two to three inches from a scale speed of maybe 30-40 mph. I have several steamers and diesels, and they all stop like they'd hit a brick wall when a short makes the DB150 cut the power.
At the same time, the Stewart Baldwin diesel switchers (the ones with the Canon motors) don't have particularly large flywheels, but they do coast a long way - they have a very free-turning mechanism. They will also stop dead if your power system shorts the track whent eh throttle is at stop - the Canon motor is so efficient that it keeps the LED headlights illuminated while coasting on the flywheels, but you can get a soldi brake action by putting a resistor across the track to make the motor actually do some work - a dead short stops it instantly.
selector...I haven't found a flywheel in a model yet worth a pinch of raccoon poo. They should spin about four times as fast and weigh twice what they do. That might get the engine to actually continue running another two or three inches.
selectorI haven't found a flywheel in a model yet worth a pinch of raccoon poo. They should spin about four times as fast and weigh twice what they do. That might get the engine to actually continue running another two or three inches.
Obviously you don't own any orignal Proto2000 E units, they have very large heavy flywheels and do just that, coast to a stop with the power turned off.
As for traction, as Chuck and David said - more weight OR, I will say it - traction tires.
I have a lot of locos, some with traction tires, some without, and now some with Bull Frog Snot. I pull long trains, increased traction and free rolling cars are a must. But I have yet to burn up a motor or strip a gear train in 40 years - its called common sense.
My newly weighted Bachmann 2-8-4's (rebuilt into 2-8-2's) have about 5 oz of additional weight - if it will fit, it will likely be fine - even with Bull Frog Snot.
Sheldon
Crandell, when the original idea for flywheels in locos came up, they were larger - and geared up to spin faster. They also caused gyroscopic problems
The practical limit for weighting a modern motor may well be the amount of space available for weight - followed by the durability of the drive system. As long as the wheels can spin, the motor won't smoke immediately. Run it overloaded for any length of time and it will overheat.
I'm surprised that no one mentioned either traction tires or Bullfrog Snot. Both offer a shortcut to motor overload...
The only real answer is to trade speed for power, by re-gearing for a lower top speed. If your loco has a maximum speed measured in Mach numbers, this kills two birds with one stone - but doing it isn't for the faint of heart. OTOH, if your loco already has to struggle to reach speeds the prototype cruised at, this may not be a practical idea.
Chuck (Modeling Central Japan in September, 1964 - doubleheading when necessary)
Trying to double the power (voltage) to a motor is a sure fire way to burn it up.
Likewise, adding so much weight that the wheels cannot spin when overloaded can cause a motor to overheat and burn up.
You just have to learn to live with shorter trains or double headed locomotives.
You want stickiness and power, but at the wheels where they touch the rail tops. As David says, the friction at the wheel, plus the power about the axle required to keep the wheel turning about the axle, is what makes your engine move, and move towing cars. All the flywheels are meant to do is to conserve momentum. They store energy as they spin up. When the engine stalls, the flywheels are meant to lose power by continuing to overcome inertia as the various frictions and gravity combine to stall the engine.
I haven't found a flywheel in a model yet worth a pinch of raccoon poo. They should spin about four times as fast and weigh twice what they do. That might get the engine to actually continue running another two or three inches.
How can you double the power of the flywheel motor inside a locomotive so the locomotive will now pull twice the power.