Anybody regear a Williams 2R Challenger?

It's not geared too low, it's geared as a proper scale model should be.  How long are your straightaways?  I guarantee, if you put a camera car in front of your Challenger at 45 mph, the video feed would resemble a roller-coaster ride! 

The noise is not an indicator of poor gearing, it's an indicator that the manufacturer didn't take the additional steps to attenuate NVH (noise, vibration, and harshness.)  This is especially important with Brass locos.  (If the loco had a die-cast boiler, we probably wouldn't be having this conversation.  There's a reason they don't make tubas out of die-cast metal!)

Three things you can do:

1. Remove the motor and flywheel from the train.  Balance the flywheel by lightly holding a finishing file against it while the motor is running.  Don't use a lot of pressure, let the file do the cutting, and stop when you feel it smooth out.  By all means, take care that brass chips don't get in the motor bearings!  (Perhaps an easier option would be to install a balanced flywheel that you can purchase as a spare part from one of the current manufacturers.  You might have to file a small flat spot onto the motor shaft for the Allen screw to seat securely.)

2. Install a square of DynaXorb in the crown sheet area of the boiler (above the motor and flywheel.)  This soft latex material is used for car audio installations, to attenuate unwanted vibrations.  It usually has a self-adhesive backing.  It'll add a little weight too!

3. Cushion the motor mount.  Use rubber grommets under the four screws that mount the motor, if they're not already present.  You could also remount the motor to the chassis with an adhesive foam pad under it, and a pair of zip-ties to hold it in place.

Properly geared locos are a rare and beautiful thing.  IMO more of them should have been made this way.  If you want a Challenger capable of toy-train speeds, there are plenty of other options available, beginning with the MTH version from 1993.  You would then have to use gimmicky electronics, tach sensor, etc., to make the train run smoothly at slow speeds.  My $.02.

Many of the Williams brass locomotives have a 44:1 gear ratio, it appears they use a common gearbox.  At around 43 scale MPH, the motor is turning at around 8,000 RPM.  I've run across four in the last few months, all had the same 44:1 gear ratio. 

I don't care how well you balance the flywheel, it's still going to make some noise at that speed.  When I run a Pittman motor without the flywheel attached at 8,000 RPM, it starts to get noisy.  The cheap motors that Williams used in those are bound to be even more noisy.

They run great at low speed, just don't expect freeway speeds out of them.

Take the flywheel out.  Try it.

Yes, I put NWSL in a Williams Challenger.  Be careful - the recent cases need to be re-sized for full worm engagement.  As I recall, a # J drill wrapped with sandpaper corrects the axle bearing hole.

Thanks for the help. I will try some suggestions soon. Some seem easy to try.

It actually runs great with MTH control in it. I just don't like the extra noise.

So I have to ask, what gearing does the MTH version have?  Mine is very quiet and runs great at all speeds, even slow. I have to wonder if it's just the shell?

Bob, I need to look at the NWSL catalog again. Did that quiet her down?

Joe, if you’re happy with the way it runs, a Pittman swap will help knock down most of that noise......any motor screaming at the top of its lungs will keep some noise, but those bigger Mubachi’s sound like they’re gonna fly apart at speed .......my brass Williams Niagara is a great runner, but man, it sounds like things are gonna come apart at anything above 40 SMPH.........Pat

harmonyards posted:

Joe, if you’re happy with the way it runs, a Pittman swap will help knock down most of that noise......any motor screaming at the top of its lungs will keep some noise, but those bigger Mubachi’s sound like they’re gonna fly apart at speed .......my brass Williams Niagara is a great runner, but man, it sounds like things are gonna come apart at anything above 40 SMPH.........Pat

What Pat says, and any motor that is completely enclosed (most Pittmans I have seen)  will be much quieter than those vented motors Williams used.  They form a bit of a siren with air passing around the armature turning at high speed.  At 44:1 the motor is never loaded up so they run cooler and a vented case is not necessary. A Pittman and sound deadening material around the motor will likely cure your noise problem. Some of those Williams motors had a very low static resistance 1.2 ohms or so and will heat up fairly quick.  If you want to go nuts you could install a Maxon coreless and get rid of the flywheel.  However they don't get along with some PWM motor drivers.  The H bridge needs to operate above 20khz for coreless motors to be happy.   Don't quote me but I think at least some of the ERR drivers are above 20k.  Coreless motors run virtually silent and don't cog at low speeds.            j

I respect Bob2's knowledge of brass.  But these are 3-rail locomotives with as many as eight (8!) rubber tires if they're all still intact.  No skidding.  If you take the flywheel out, and some inveterate postwar Lionel operator hits the "DIR" button, even if the train is running slowly you'll have a bone-jarring stop, and a spectacular derailment.  Even worse you could bend a driving rod, break a crank pin, or cut a burr into the brass worm wheel.  Flywheels are a good thing!

Pat is a wizard, I love his conversions!  But with your stock gearbox, the Pittman motor will be too slow.  Although it's noisy and a little cheap, your stock motor is good for 13,000 RPM at 24 volts (which you could get back in 1990 with a Right-of-Way transformer or a prewar Type Z.)  This would equal the 70 mph speed of the prototype.  The slow-turning Pittman redlines at about 6800, so your loco would be lucky to hit 40 mph with that.  If your current motor is a 3-pole RS-550 you could replace it with a 5-pole RS-555, but it would still have to be the high-rpm winding.

The MTH Challenger has a 12-volt, 6800 RPM Pittman motor and self-locking 16:1 worm gears.  This combo is good for about 90 mph on the top end, which is faster than the prototype, and IMO faster than anyone needs to go.  With 30" of loco, how long are your straightaways?  In a few seconds you'll need binoculars to see the darn thing!  It also has a flywheel that's really too small to be effective at the low RPMs it's turning.  I had the PS1 version.  Again, if a kid hit DIR while it was running at normal speed, you would get a bone-jarring stop.  The old 773 was much more friendly in this regard.  The Challenger was hyped as a "scale model" when it came out in 1993, but it had shiny driving wheel tires and handrails, oversized smoke box hinges, no sprung drivers, etc.  Despite all the hype and the high price it was still very much a toy train, and in some ways a step backwards from the products offered by Williams and Weaver.

With 16:1 gearing, the PS1 version had to be coaxed to run consistently at anything below 10 mph.  For example: pull out of the engine house (no trailing consist.)  As soon as the drivers got on a curve it would slow noticeably or stall.  With all that weight over the rear tires the wheels couldn't skid, and there just wasn't enough torque or stored energy in the flywheel at 800 RPM to overcome the sudden increase in friction.  I gradually became disappointed and traded mine, lost a lot of money.  Instead of installing a separate 30:1 gearbox like they should have, MTH (and Lionel) applied the band-aid of electronic speed control, which gets us to where we are today.

What you have is actually very good, and I encourage you to work with it.  Flywheels aren't expensive.  Order the largest one you can from Lionel or MTH, or try the trick I recommended with the file.  Definitely add the DynaXorb and the rubber grommets, this isn't hard to do.  Then come back and tell us if it worked!

Ted, coreless motors without flywheels will coast down much slower than an iron core motor without a flywheel when the power is removed.  I have some Maxons the size of a 385 and some 385s with flywheels that I bought to add power to a dummy DL-109 I have the Maxons in hand but will have to open a few boxes to find the 385s.  I will try and set up a test with them running side by side and make a video.  I have an optical tach and will  adjust them to the same RPM.  Never tried a side by side coast down between a coreless and iron core motor with flywheel.  Just a guess but I bet their close.   And sure you can use a flywheel on the coreless but it is not vital as on an iron core motor.  Another mod I would like to make to all my Williams steamers is to cut some metal bands to replace the traction tires on one side of the loco I think they would run through curves smoother and with rubber tires only on one side the steel wheel side could slip a bit putting less stress on the rubber tire and likely deposit less rubber on the rails.  I'll likely sell them before getting around to that.  At 73 some projects are just not worth the time they take.  Do hate rubber traction tires though. Geez it's ten till 5am           j

Hmmm. So first off, I'm happy with the MTH PS2 board inside right now. So I'd have to figure out if it would run a coreless motor.

This engine is 2 rail, and no traction tires.

I'm tempted to get in there again, and check the flywheel for balance. I built another engine and had the homemade flywheel make most of the noise. It was plastic and easy to fix. I just needed it for the tach tape.

I really believe that this particular engine has low gear issues and that's where the extra noise is from. The flywheel spinning that fast must be a big part.

I don't wish to run this engine much faster than say 60MPH myself. Our grandsons push it more than I do and have learned that 45 is a good top speed. It's still loud at 45. I don't wish to fight with the 2 rail crowd over fantastic 2 MPH operation. I think my MTH Challenger runs fine. I considered swapping the main engine frame for a faster fix. I just don't want another carcass laying around in waste.

 My layout goes completely around the basement. I have long straights that can handle long trains. I'm not sure what that has to do here, but I will answer that question. I am not a high rail, high speed runner. Having to run at 30MPH to hide motor drive issues seems ridiculous. It is easy here with DCS, as I can set the top speed of any engine to whatever I wish. I also can build a consist in seconds and every engine gets along with each other. So I wish to retain that and not change my motor control for one engine. It would be easier to get rid of it than change command controls, or just carry on at 30MPH for this one.

Take the flywheel out.

My Williams "J" (2-rail, no traction tires) was really, really noisy.  I thought it was the gears.  Nope, flywheel.

I made the mistake of putting a Pittman in and losing the original motor.  Dead smooth, but way, way too slow.

Take the flywheel out.  Not opinion.

If you have a conventional iron core motor it's almost imperative to have a flywheel. Especially if it has a non coasting gearbox.   A lot of the Williams locos had a flywheel that the hole in the middle was too large for the motor shaft and they just tightened down the set screw and held it on in a non concentric position. These things would almost vibrate the detail off the boiler. The way I fixed the ones like that was to press the smallest pinion gear on the motor shaft that I could. Then hold a file against it,while running, and turn it down till I had a brass collar a couple of thousands thick that took all the slack up in the flywheel hole to the point that you "almost" have to tap the flywheel on. Be careful to keep the surface of the file flat against the gear you don't want a taper. Perhaps rig some sort of tool rest keep the file square.   I tried shims and with enough tinkering you can make them work but turning down a brass pinion gear really does the trick. It does take a bit of time and patience.       Off to see if I can put together that coast down shoot out between a coreless motor without a flywheel and a Mabuchi 385 with a flywheel.  Someone mentioned Coreless with MTH board.   Wonder if anyone at MTH can tell us the PWM frequency of their boards.  20Khz is about the minimum for coreless motors.  Some of the ERR boards claim that.          j

I'm sure you probably know this John, but just in case someone reading along takes your statement the wrong way about tapping a flywheel on. 

NEVER tap anything on a motor shaft without the opposite end of the shaft being supported!  What is likely to happen is you'll slide the commutator along the shaft and kill the motor!

This is the 2-rail section, right?  Two rail locomotives almost never had flywheels before Williams, and the old hands will tell you they ran fine.  Even the Lionel scale stuff from 1939 ran beautifully, although they sorta had coasting gearboxes.

Take the flywheel off, test it, and if that was the problem and you want a flywheel, balance it and re- install, or make a new one.

Well for one thing, this engine comes apart so easy and fast, I should have done that first.

I got the engine on the bench and removed my tach tape. I removed the flywheel and ran the motor in my hand. It's a very loud motor to start with. It screams with only a few volts DC directly to it. That seems like the exact noise that's bothering me. I re-installed it back into the engine. I noticed that it already has a rubber type shim against the mount to the motor housing.

 I put a file against the flywheel as square as I could by my eye, and ran the motor. It filed the edges of the flywheel only and not the center? It felt very smooth. When I've had problems in the past, I could actually feel the flywheel out of balance. I tried the flywheel against the edges and it appears to be balanced.

 So in my opinion, there's 2 things already that I've found. A very loud motor, and the lower gearing so that this motor needs to crank up more. I'm sure it would be quieter without the metal flywheel. I considered making one out of plastic so I could still mount my tach tape needed for command. I don't have the proper tooling to make one better than what's already on there in plastic. My home made ones are usually are slightly off balance.

 So I'm tempted to either lower the gearing, or swap out the motor with another engine I have lying here. Maybe a quieter motor would help the most I feel.

 I can always put the stock motor back in. I really feel that it's the motor making this annoying noise I hear! It's tuff for me here because I respect Bob2's opinion so much already.

here's the before video ( I should have parked the cars!)

here's just the main drivers. The clicking is from the plastic drive coupling flopping around.

BTW there's some type of adjustment that seems to angle the gear box drive? Maybe changes the pitch of the main gears?

I'm not sure what it does or how to adjust it properly.

Joe, the air-raid museum called, they want their motor back....😉

good god that’s noisy!...I take Bobs suggestions as gospel as well, but I’d try a motor swap and see if you could get happy with the speeds......my Niagara is noisy, but not that noisy.......Mubachi’s are land fill material IMO .....I hate them!....I hope you get it fixed, that’s a sharp looking video, although I didn’t see the Cessna come by?........Pat

So what informed your decision to not remove the flywheel?  That is exactly the noise my "J" made until I pulled the flywheel.

Yes that motor is an extremely high rpm deal - we think it is a windshield wiper motor.  A 9000- series Pittman will slow that thing down to switcher speeds.

Show us a video without the flywheel, and I will publicly "eat crow" if it is not lots quieter.

I did remove the flywheel. I ran the motor disconnected from the engine.

It now has the flywheel back on with a new tach tape. I will remove it again and make a video for you later tonight. I'm getting a motor from Norton.

I got around 43-45 scale MPH from a Williams Niagara with the 44:1 gearing at full speed.  While not exactly "warp speed", it was sufficient for the job and the customer was happy with it.  OTOH, I'd like my locomotives to top out at at least 60 scale MPH, not that I'll run that way a lot, but it's nice to have gas in the tank.

gunrunnerjohn posted:

I got around 43-45 scale MPH from a Williams Niagara with the 44:1 gearing at full speed.  While not exactly "warp speed", it was sufficient for the job and the customer was happy with it.  OTOH, I'd like my locomotives to top out at at least 60 scale MPH, not that I'll run that way a lot, but it's nice to have gas in the tank.

My Challenger will go much faster than 45MPH. It's just that it sounds like it's tearing itself apart. I don't even like the sound at 45. It's better around 30 MPH and that probably sounds good for users here. It's just too slow for me. I expect my engines to do 50MPH easily. Not like they're going to croak.

Well for some reason today the motor is slightly quieter than I remember last night running in my hands. Here it is laying on the bench which more closely mimicks the sound it makes in the shell. It is quieter without the flywheel. I'd still need something for the tach tape to attach to with the PS2 board set.

This is with about 6 to 8 volts DC!

The only other thing I could think of would be to move the flywheel to the other end of the u-joints at the gear tower. It wouldn't fit there as is. Or have a motor with dual shafts and put the flywheel on the back of the motor like MTH does. I'd have to create an attachment to replace the u-joint shaft that's built into the existing flywheel. Still need a flywheel for the tach tape. Too much work and no gain.

 1) Lower the motor's gearing so that it doesn't even need to spin so fast.

or

2) change out the drive shaft assembly to rid the flywheel yet still need another one for the tach tape.

or

3) find a quiet high speed motor and hope the drive is quiet

or 

4) swap out the whole thing for an MTH chassis

First get a rubber hose and try the thing without the tach tape.  If you put that flywheel on a Pittman or Mabuchi or whatever it won't get any smoother.

Change to a Pittman 9000 and change the gearing around in the box. Worked great for the NWA.

That is true.  I did one like that with NWSL 25:1 and 8000 Pittman.  Worked great.  Really nothing wrong with the Williams gears, though, and at $200 for parts before labor you are looking at a real investment.

By the way, this particular model is stunning, in my opinion, and needs only a wider firebox to make me happy.  I have off and on thought about adding one to my collection, but await the proverbial steal.

gunrunnerjohn posted:

I'm sure you probably know this John, but just in case someone reading along takes your statement the wrong way about tapping a flywheel on. 

NEVER tap anything on a motor shaft without the opposite end of the shaft being supported!  What is likely to happen is you'll slide the commutator along the shaft and kill the motor!

Right John, I think the phrase in question is "almost have to tap the flywheel on"  Almost is the qualifier.  I have been winding motors, removing and pressing gears, since the tenth grade in high school and  can forget many on the forum are lacking in experience and if you leave room for error someone will surely find that room. So folks never ever tap anything on a motor shaft unless the end of the shaft protruding on the opposite end of the motor is pressed against something like a steel plate well supported so that shaft cannot slip within the armature or crush supporting structures which keep the armature centered. This goes doubly for the coreless motors which only have a shaft on one end. The rear end of the shaft forms a needle and runs in a deep cup. To mount a gear or anything that presses on it you must grip the shaft with something like wire cutters against the front of the case holding the needle bearing  up enough in it's seat that it does not bottom out. Some of them have an E clip on the shaft which is supposed to keep the needle from pounding against it's seat. Works for running. Don't depend on it for pressing gears on.

The problem with the Williams 44:1 gearing and 1.4" drivers is you need 12,900rpm for 60mph. The only motors that will turn that fast and not whine like a banshee have closed cases. High RPMs mean low static resistance, sometime called terminal resistance and for an iron core motor that means heat and a short duty cycle in a closed case. Not well suited for model trains.  The only motors suited for this task are coreless they are approximately 50% more efficient than iron core motors and don't heat up like iron core motors. All that and they coast several times longer than an iron core motor.  See post of my video  immediately following this one                          j

In the flywheel vs no flywheel debate I mentioned a couple of days ago that I would do a coast down comparison between a Maxon coreless (with brushes) no flywheel  vs a Mabuchi 385 with flywheel.  for the test I have both motors adjusted to between 6500 rpm and 6600rpm the Mabuchi was turning about 40rpm faster than the Maxon.  The two motors have different static resistance Maxon 5 ohm and the Mabuchi is 3.8 ohms they require different voltage to acheve the same rpm. The Mabuchi was adjusted to a hair over 7V and the Maxon about one volt more. In the video you can see that both motors running just shy of 6600 rpm the Maxon with no flywheel coast approximately one second longer than the Mabuchi with a flywheel. The Maxon is without a doubt quieter than the Mabuchi in fact the Maxon at 20v is quieter than the Mabuchi at 7v by quite a bit.  It hardly makes more noise at 20v that at 5v. I bought a bunch of these before converting to TMCC for use with Dallee solid state reverse units at 18v. They will not develop full power on the Lionel Drivers that only output 12v

 To my statement about the Lionel H bridge drivers I have not tested all of them and none of the Legacy drivers however one which I have tested delivered higher voltage to the motor than any others which I have tested.  The DCDR as used in the Alco PA-1 from the 90s maxed out at 15.8v driving two 500 series can motors. I have also measured a couple of TAS boards that were just under that around 15.5v driving two mabuchi 385 motors. At 15v my Maxon motors may  be useful in some applications. Depends on the PWM frequency and I plan on testing some boards for that. 20khz is the magic number.          j

All I'm sorry if I misled the thread.  Despite the obvious title, it escaped me that this was a 2-rail model without rubber tires, which are a pet peeve of mine as a 3-railer.

John your video was very instructive, thanks for posting it.  I surmise that the rotating part of a coreless motor has more mass compared to the "armature" of a typical can motor (which is a comparatively small diameter contained between two heavy magnets.)  Does the coreless motor coast longer because it has lower friction bearings, or more stored kinetic energy?  Does it also use permanent magnets?  Low-friction bearings are great, but it's the stored kinetic energy that will keep the train moving. 

I would love to see the experiment repeated with each motor yoked to a self-locking drive as used in the Williams or MTH locomotives.  In such an application, the stored kinetic energy, net of the total friction in the system, is what determines how far the train will "coast."

The switch to can motors happened a few years before the widespread adoption of command control, so in the late '80s/early '90s the output of the decoders wouldn't have been the limiting factor.  I wonder why more manufacturers didn't specify coreless motors as original equipment?  Cost, perhaps?  Also, have you looked at Lenz or Zimo decoders marketed for G-scale?  They might be rated for 24 volts.  Very interesting and informative thread!

Coreless motors have less mass. The rotating section is just a cylinder made of copper wire.  Its not wound on an iron core, hence the name. The magnet resides inside the cylinder. I can only assume it rotates longer after removing power is due to better bearings. 

Pete

There is no ferrous material in the armature to be attracted by the magnets. Open the circuit ,remove power, and they just coast. Now Short the connections out and they develop tremendous dynamic breaking and will stop faster than an iron core motor. Less armature mass to stop. Much lighter than a comparable similar sized iron core armature.   Not much of an issue in toy trains but useful in slot-cars. The needle bearing on the back does tend to have very low friction however  no magnetic attraction to the unpowered armature is the real key.   Another point, double the voltage and RPM and the coast down on the iron core motor increased by about 25% on the coreless it almost doubles. So if you loose power on your loco at high speed the coreless will come to a much more gentle stop.  And, then you can always add a flywheel to the coreless if you like. It must be well balanced however as it will create a yaw along the axis of the armature and stress the needle bearing causing early failure.     j

Ted,  Iron vs Coreless ?     COST 

Also the first PWM drivers operated at much lower frequencies and did not play well with coreless motors.     DCC had been around for years before a 20K driver was available.  The coreless can tolerate 15K however it starts to loose it's advantages as frequencies get lower. On a motor control forum I ran across some guy saying they did not really come into their prime till 80k. By the way, there are many H bridge drivers on eBay for cheap that are over 20k. I am tempted to buy a couple and see if I can make them talk to a R2LC some are rated for 15A and will drive 4 can motors "AA diesels" .                        j

Lost me.  Most 2-railers don't use DCC or other command control systems.  But it is my understanding that such systems actually mimic flywheel action - you spike the throttle to zero and the program gently brings the locomotive to a stop.

I do know something about inertia.  If your coreless motor has very little rotational inertia, then removing voltage from it will result in a sudden stop, because the gearbox has no way to overcome friction.

On the other hand, take a giant K&D motor (ACDC, like Lionel before Pittman) and remove the voltage.  Its giant iron armature will act as a flywheel, allowing your locomotive to coast a bit.  

Try your experiments hooked up to a gearbox.  Spinning a motor under no load conditions will not inform you of much.

A few points that may help some understand the faster coast down and lower efficiency of iron core motors vs coreless.  If you hold an iron core motor in your hand and turn the shaft with your fingers and then do the same with a coreless motor you will find the coreless motor offers nearly zero resistance to you turning it manually. The iron core motor is entirely different you definitely have put some effort into turning it. It is this resistance to turning that the current in the coils of the armature must overcome before the armature can turn. Again if you are turning it by hand the faster you turn the armature the more effort it takes to overcome the drag from the static magnetic field surrounding the armature. The motive force supplied by electricity flowing through the coils of the armature must work increasingly harder as you apply more voltage and current in order to achieve more RPM and more of the power applied turns into heat until the heat destroys the motor. This is not the case with coreless motors they have virtually zero magnetic drag caused by the field magnets attraction to the iron in the armature. There are other small factors that affect efficiency such as airflow around an irregular shaped armature, the siren effect,  vs airflow around a very smooth cylindrical armature which creates little if any turbulence in the air which surrounds it. Also the coils on that cylindrical armature have much more surface exposed to the air and transfer heat more efficiently. Google: "photos coreless motor armature"  most of these photos will carry you to articles which discuss theory in depth.     j          

bob2 posted:

Lost me.  Most 2-railers don't use DCC or other command control systems.  But it is my understanding that such systems actually mimic flywheel action - you spike the throttle to zero and the program gently brings the locomotive to a stop.

I do know something about inertia.  If your coreless motor has very little rotational inertia, then removing voltage from it will result in a sudden stop, because the gearbox has no way to overcome friction.

On the other hand, take a giant K&D motor (ACDC, like Lionel before Pittman) and remove the voltage.  Its giant iron armature will act as a flywheel, allowing your locomotive to coast a bit.  

Try your experiments hooked up to a gearbox.  Spinning a motor under no load conditions will not inform you of much.

Bob, this what your talking about ?   Just happened to have one in my pocket.  I love the old K&D motors and actually replace Lionel Pullmor motors with them. One neat thing about universal motors is if you loose power the field collapses and you don't have magnetic drag on the armature. However that is not the case with Pittman or Mabuchi or any other permanent magnet iron core motor. Checking the US code on Westlaw I can find no laws against using flywheels on coreless motors. If you take the brass flywheel off the Mabuchi 385 in my test and install it on the Maxon, rev it up, cut power, it will still be spinning when you get up in the morning.   Well maybe not.  However, what you speak of with a non-backdriveable gearbox must be examined on a case by case basis and may not be all that simple.  Imagine a model locomotive pulling a long train. Now imagine a screw loosens and the worm jumps out of place. What would happen ? The train, loco and cars have efficient smooth rolling trucks, properly weighted cars and a nice smooth Lobaugh loco well quartered drivers etc. etc. and inertia.  it will coast to a smooth stop not abruptly slam to a stop. So now we have a shiny new five pole Pittman driving that same train and a solder joint fails on a wire to the motor.  The motor looses power and the flywheel is now driving the train.  NOT that little flywheel. What they are doing is trying to overcome some of the magnetic drag from a permanent magnet field on the iron in the armature. Keep the worm ahead of the spur till the train coasts down. The worm can drive the spur(aka worm wheel, worm spur) but the spur cannot drive the worm. As long as the worm's spiral is just leaning against the back side of the spurs teeth the gearbox will not lock up and the loco / train will come to a civil stop. The tiny flywheel is not trying to drive the train it's too small to do so but it is just right to drive the worm. It may slow the rate of deceleration in some minuscule way but won't add 10% to the coast down distance. What it will do is keep the gearbox from locking up so the coast down uses the full inertia of the train.  Remove power form an iron core motor and the permanent magnetic field puts on the brakes.  When power is lost coreless motors do not put on the brakes and neither do universal AC/DC motors as the fields magnetism collapses with the loss of power.  However these old K&D motors have a good bit of bearing friction as well as big brushes and lots of tension on them.  Photo below is a K&D in the firebox of a Lionel 18009 Mohawk, it makes a big improvement in low speed performance.

That little flywheel on the mabuchi cans does have considerable effect when the motor is starting the loco to limit cogging.    j

Just checked an MTH PS-2 3V engine and the PWM frequency is 22 khz. I am guessing PS-3 engines are similar but haven't checked those yet. 

Pete

Norton posted:

Just checked an MTH PS-2 3V engine and the PWM frequency is 22 khz. I am guessing PS-3 engines are similar but haven't checked those yet. 

Pete

Pete, Great news.  Thanks !          j

I am not anti-flywheel.  They are truly nice if properly balanced and you have room.

Joe had a vibration problem.  I think it is that horribly balanced Williams flywheel.  He thinks it is the motor.

There is an easy way to find out, and it is not by running the motor in your hand.

I truly wish I had known that before re-motoring my Williams "J" and losing its original motor.  Even with an 8000 Pittman it is painfully slow.  Nice model, though.

Agreed the Williams flywheels suk.  The most offensive have a hole too large for the motor shaft and are not concentric.       j

You would think that if the flywheel was out of balance that bad, that I could feel it with the file against it right in my hand! It ran smoothly. The file drew lines completely around both outside edges of the face. If anything, it's slightly convex shaped but not out of round. It is heavy so the mass at anything but perfect would be a problem. Spinning at the required speed doesn't help here.

You want the video (another one) of it running completely without the flywheel. That is going to take some work as I already threw the engine back together. I have to have something for the tach tape to attach to for motor control.

 I'm not ready to tear it apart just for that test right now. The motor screamed with no flywheel. I didn't like that. I did hold the motor in my hand the first time. My other similar motors don't make that kind of scream.