I’ve just had the first opportunity to test-run my brass West Side Models HOn3 C-25 after wiring up part of my layout. The only modifications I’ve made to this locomotive were to re-gauge the wheels to NMRA standards to avoid shorting on turnouts. I’ve uploaded a video here showing the loco in action. Would the addition of a flywheel to the motor of this model smooth out the jerkiness? Or could it possibly be due to tight wheels or something else along those lines?
Thanks in advance,
tbdanny
EDIT: The jerkiness issue has been resolved - it seems that the rear driving axle was just slightly too wide and was rubbing against the frame. However, I would still like to know whether it would be worth adding a flywheel to this locomotive or not?
IMHO, a flywheel is always worthwhile. Flywheels are especially effective in overcoming motor “cogging” at slow speeds.
In an ideal world, the mechanism should be smooth without a flywheel - something you proved. If you had had a flywheel during the initial testing, some or all of the jerkiness might have been masked. That’s the problem with any aid - electronic or mechanical - to smooth, slow speed running. They can mask problems in the mechanism.
The up side of a decent-sized flywheel is that it smooths out any sudden changes in speed, including stops and starts. And it allows the model to coast over a spec of dirt on the track.
Other downsides to a flywheel besides masking mechanism issues: takes space that might be better used for weighting the model; has to be balanced to avoid introducing new vibration issues; may possibly cause bearing wear on the motor (especially with the newer small motor shaft sizes); and in small models it’s difficult to mount a flywheel big enough to have a real impact (diameter is more important than length).
Some of the remotoring and regearing experts recommend supporting a flywheel separately from the motor, especially with a less than 2mm motor shaft. Use a universal and separate bearings.
Replacing the pathetic, unbalanced, cast piece of metal called a flywheel with the real thing in my MDC Climax made a significant difference in noise and vibration. Even the factory junk flywheel had already made the model my smoothest slow runner, despite easy-to-feel motor cogging from the open frame motor.
You´d be surprised, how little a flywheel actually does contribute to a smooth performance of your loco. How much would a flywheel actually weigh? 25 g? How much is the total weight of your loco? The momentum created by such a little weight is not worth the trouble.
Better to ensure, that the mechanism of your loco is really free rolling, maybe add a quality can motor and put some more weight into the loco.
Time to start making flywheels out of something heavier than brass - like perhaps depleted uranium. More mass can make up for smaller diameter, as can speed - although it is highly impractical in HO and smaller to set up a flywheel that is geared to turn 4x the motor shaft speed or faster. Go too far though and you’ll end up burning up the motor trying to get it started.
A free turning motor with a resonable flywheel can go quite a long way - witness the Stewart Baldwin switchers made by Ajin, with Canon motors in them. Cut the power and they coast for a LONG way - and it’s a fairly small flywheel. On DC they coast long and far enough to experiment with actually having brakes by putting a resistance across the rails. The LED stays lighted fromt he BEMF generated by the motor. SHort the track and it stops on a dime, use a resistor and you can slow it down at various rates. None actually approach the prototype, even letting it coast down on its own it stops far quicker than a prototype did if you got it up to 25mph and shut it off. But compared to many models, it’s amazing.
Every once in a while I ask BLI to consider making their steamer frames out of tungsten or a tungsten alloy, and I wouldn’t mind seeing this done in flywheels, too. On the other hand, making a flywheel that much heavier would impose that much more on a spin-up burden on the tiny can motor and bearings.
Sir Madog,
Um, actually, flywheels contribute a lot to the smooth performance of a loco. That’s especially true for any engine that uses a worm drive. Without a flywheel, a worm-drive loco will stop the instant it loses electrical contact. If it’s still on the dead spot, the loco will die and you’ll have to give it a shove to get moving. If the same exact loco has flywheels, the loco will coast over the dead spot (provided it’s a small enough dead spot) and continue on.
I have several brass steam engines without flywheels, and their performance when hitting any kind of dirt or dead spot on the track is to stop instantly or actually skid when running at speed. If I could get a flywheel in these, that wouldn’t happen.
Quite frankly, I am mystified about your comment. All you have to do is look at the Proto E-units from the 1990’s to know what flywheels will do (and these engines weighed around 16 oz.). These locos were notorious at our old RR club for coasting…so much so that we had to move them around the engine facility with a “sprint and drift” method. Sometimes they ended up in the turntable pit because they coasted too far. [:)] My point is that flywheels can do a lot towards overcoming jerky operation.
It appears to me that the drivers are VERY slightly out of quarter and this causes the side rods to bind. I suggest removing the motor and worm (helical gear) so that you can test to determine if the drivers and rod assembly move freely. If not, then checking the quarter of the drivers is a good next step. NWSL offers a quartering tool to help you get it right. It is possible to fiddle with it until you get it right, but that can be tedious and often things get worse before they get better.
I understand that NWSL will re-quarter drivers as a mail-transaction service.
If the wheels and rod assemblies are free, take a hard look at the worm gear (spur gear that engages the worm). It may have a bad tooth or a little wobble that is causing it to bind a little. NWSL can help with replacements.
Regarding flywheels, I think they help a lot because they keep the motor turning during brief power interruptions and they give the motor a load to work against when first starting, but they won’t overcome binding valve/gear rod assemblies.
A few decades ago, MR published an article about flywheels. It was enlightening in that it showed that the diameter is more important than the weight.
I have to agree with Ulrich: a small flywheel is a waste of space, better used for additional weight. I bought one of the early (no tender pick-up) Proto USRA 0-8-0s and was very disappointed in its poor pulling power. I was going to get rid of it, but decided to see if I could make any improvements. By removing the puny flywheel and replacing it with a lead weight, along with some additional weight elsewhere, I was able to double its pulling ability, making it worthwhile to keep and re-detail. I planned to eventually add tender pick-up, too, but it seems to run fine without it (or the flywheel). [swg]
On the other hand, a large flywheel, such as could be fitted to a carbody-style diesel, such as an E- or F-unit, can have some effect, although with 8 or 12 wheel pick-up and good quality motors I’m not convinced that they would be preferable to additional weight. A lot would depend on one’s operating practices and circumstances.
In my experience (a sizeable fleet of steam, diesel and catenary locomotives, plus EMU and DMU) jerky operation has always been attributable to two causes:
Mechanical misalignments and maladjustments. When the mechanical glitches were corrected, the operation smoothed out.
Dirty track. Haven’t had any such problems since I started ‘gleeming’ all my trackwork.
Especially at prototypically slow speeds, the flywheels that can be fitted inside a skinny locomotive boiler can’t store enough rotational energy to make much of a difference. They certainly can’t hold a burned-out candle to a good electronic coasting/slow acceleration circuit.
Thanks for that information, I too have the same loco, and am going to add some weight, glad to hear in your case that in doubled the pulling power.
BTW, I had a Spectrum Tender from a 4-6-0 sitting around, I borrowed the wipers and installed them on the 0-8-0. Mine loco was dying at every Atlas dead frog turnout I had, problem solved!
