George,

I've never gotten into tooth angles or exact measurements. Those factors determine whether drive wheels can be spun by hand with the worm engaged, but they are not usually a factor in troubleshooting.

The most common method is to adjust the position and angle of the motor for maximum speed and minimum noise for a given voltage. This is done by running the engine at medium speed propped up on a test bench. Shim the motor mount until these conditions are achieved. Sometimes washers are also needed to limit play in the armature when shifting from forward to reverse.

About the only 3-rail locos I know of that might require such adjustments are the 726/736 Berkshire and its derivatives or the 671/681 turbine....and it is rare to find one of these that needs adjusting.

The most infamous case of a poorly designed drive system that often needed adjustment was that of the early MPC Northerns.

Armature play is a factor in some postwar and MPC diesels with the cheapened bearing design such as the sheet metal frame NW2 switchers, etc.

Jim

I don't have experiance with the Northerns but my vote for poorest design is the motorized units from the gang car on up. Lots axle play lets the worm get misalligned with the worm gear, exacerbated by the back and forth sudden direction changes. Keeping the worm centered on the worm gear is very important though less of an issue on big engines with proper gearboxes which hold everything pretty much in allignment.

Pete

With out going into the mellow dramatics....the idea is to burry the worm into the worm wheel, deep enough to achieve the most contact patch, but not to drive the toes of the worm into the base circle of the worm wheel....in the case of the stuff you mess with George, like 671’s 681’s 736’s etc.....tilting the motor sometimes becomes necessary to pitch the worm into the wheel......fortunately, all of those examples as you well know, you can roll the wheels and feel the backlash,......it’s pretty easy to tell when there’s too much backlash, or too much burial...too loose a backlash, and the wheels will rock back and forth like crazy or even skip...too little, and the whole works will lock up since the toes are buried into the base circle of the worm wheel.....I wouldn’t concern yourself with trying to find an exact measurement, ....just find the happy spot where there’s little back lash ( back and forth rocking the wheels) but the motor and wheels aren’t in a bind...that’s what creates high amp draws, and overheats.......

Pat

Plutonic?

The proper mesh of a worm and worm wheel is determined by shaft center distance.  The center distance, C=0.5 (d + D).  d is the pitch diameter of the worm and D is the pitch diameter of the worm wheel.  For gearing design and manufacturing data is would suggest a copy of the book “Machinery’s Handbook” by Industrial Press.  The detailed geometry of most post war gears is in Chapter 30 of the “Lionel Engineering Standards” available from Trainpaper.com.  These two books will run about $600 for both.  

I agree with harmonyards assessment of how to check proper engagement of Postwar Lionel gearing. The gears should be engaged deeply without the tips of the teeth hitting. Most gears are rolling contact. The worm is an exception as it slides across the face of the gear. For worm gears proper lubrication is critical. 

In the middle of the post war era Lionel changed from the older 14.5 degree pressure angle to the current 20 degree pressure angle.  These do not mix well and an effort should be made to try and keep both gears of a set the same pressure angle. The 20 degree pressure angle gears have a fatter looking tooth. The 14.5 degree pressure angle gears will run quieter, the 20 degree pressure angle gears have stronger teeth.

@Jim Policastro posted:

George,

Armature play is a factor in some postwar and MPC diesels with the cheapened bearing design such as the sheet metal frame NW2 switchers, etc.

Jim

Amen on the last issue! Some of the sloppiest, worn out engines (diesels) I have seen have a worm engaging the worm gear and only one axle driven.  Many that I have seen are not "adjustable" or "shimmable" just due to the excessive slop in the bottom armature bearing.

Thanks for the feedback!

@dkdkrd posted:

Pour yourself a glass of your favorite libation, find an easy chair by your computer...or print the following eleventy-seven pages...and read (Old) Northwest Shortline's treatise on gearing....including 'relationships' between worms and gears...

NWSL Gear Link

There'll be a quiz at the end of your reading....just kidding!!

KD

Holy Moly! That's a lot to digest! I guess you win for the longest answer! Seriously, I will study on that a wee bit at a time - thanks! 

@harmonyards posted:

With out going into the mellow dramatics....the idea is to burry the worm into the worm wheel, deep enough to achieve the most contact patch, but not to drive the toes of the worm into the base circle of the worm wheel....in the case of the stuff you mess with George, like 671’s 681’s 736’s etc.....tilting the motor sometimes becomes necessary to pitch the worm into the wheel......fortunately, all of those examples as you well know, you can roll the wheels and feel the backlash,......it’s pretty easy to tell when there’s too much backlash, or too much burial...too loose a backlash, and the wheels will rock back and forth like crazy or even skip...too little, and the whole works will lock up since the toes are buried into the base circle of the worm wheel.....I wouldn’t concern yourself with trying to find an exact measurement, ....just find the happy spot where there’s little back lash ( back and forth rocking the wheels) but the motor and wheels aren’t in a bind...that’s what creates high amp draws, and overheats.......

Pat

Yes, actually my book reading on the 671 was taking me down that "shimming" road that others have tried before me. And in truth, mine is the 1946 model, so the armature shaft has a giant spur gear, not a worm. But there are two worms on a single shaft down below (as I'm sure you are aware) and IMHO, the worms seem to have a fixed relationship with the axle worm gears. It would be difficult to make height adjustments on those rectangular bearing blocks without doing a LOT of disassembly/reassembly and maybe some shims or grinding. Not to mention the geometry between the armature spur gear, the receiving spur gear on the drive shaft along with two worms on the shaft, and their relationship with their respective worm gears! Too much for my brain! I guess I got lucky, mine sounds and works pretty well with no real adjustments. 

Well, I did have to shim the axles, their was a WHOLE LOT of rubbing of wheels going on. And even the reinstallation of 6 of the 8 wheels seemed to go well (i.e. nice and tight) until a drive wheel started moving outward on the axle and stalled the engine with so much rubbing. Then, two of the rear truck wheels simply slipped inward on their shafts and shorted on the center rail - and I didn't even pull those puppies! Some Loctite 243 fixed things right up and all is well now. So in the end, I discovered that the 671M-23 0.010" washers were my best friends!

Thanks Pat

@dkdkrd posted:

Pour yourself a glass of your favorite libation, find an easy chair by your computer...or print the following eleventy-seven pages...and read (Old) Northwest Shortline's treatise on gearing....including 'relationships' between worms and gears...

NWSL Gear Link

There'll be a quiz at the end of your reading....just kidding!!

I sure wish the engineers at K-Line had read this before they decided to mount a tiny motor facing backwards into the boiler.  What were they thinking!?

There is no novel engineering in the drive systems for model trains.  It doesn't require cold fusion, quantum mechanics, etc.  All of it was known and even perfected by the middle of the 20th Century.  Perhaps more attention was paid to it then, than now.  The only reasons NOT to do it the best way possible today are cost cutting, and to facilitate mass production.  Which is ultimately a form of cost cutting, although sometimes it pays dividends to both the manufacturer and the consumer.  

I encourage everyone to study, learn, and know what you're buying.  If I knew years ago what I know now I would have kept a lot of my money in the bank, and left many of those trains in the store!

I remember you posting pics of that early horizontal drive 671 George, ....as I recall, a couple of us pointed out those gears looked really good for their age...( wish I looked that good ) .......if you have no slippage, and backlash feels appropriate ( you’ll know when it’s not ) and you’ve cured the wheels acting as effective brake shoes, then let her eat....It’ll be good to go for another 70 some odd years....😄

Pat

@Ted S posted:

I sure wish the engineers at K-Line had read this before they decided to mount a tiny motor facing backwards into the boiler.  What were they thinking!?

There is no novel engineering in the drive systems for model trains.  It doesn't require cold fusion, quantum mechanics, etc.  All of it was known and even perfected by the middle of the 20th Century.  Perhaps more attention was paid to it then, than now.  The only reasons today NOT to do it the best way possible are cost cutting, and to facilitate mass production, which is ultimately a form of cost cutting, although sometimes it pays dividends to both the manufacturer and the consumer.  

I encourage everyone to study, learn, and know what you're buying.  If I knew years ago what I know now I would have kept a lot of my money in the bank, and left many of those trains in the store!

I’ve found the Kline mini-motor cure Ted,...it’s called a MTH chassis.....with the motor where the good lord intended it....in the back....😉

Pat

@GeoPeg posted:

What should be the relationship between a worm and a worm gear?

Close, very close.

@gunrunnerjohn posted:

Close, very close.

With just a little bit of backlash!!

@harmonyards posted:

I remember you posting pics of that early horizontal drive 671 George, ....as I recall, a couple of us pointed out those gears looked really good for their age...( wish I looked that good ) .......if you have no slippage, and backlash feels appropriate ( you’ll know when it’s not ) and you’ve cured the wheels acting as effective brake shoes, then let her eat....It’ll be good to go for another 70 some odd years....😄

Pat

Yeah, I decided against gear pulling, the more I looked, the better they looked! In the end it seems to be running well. It does have the armature growl as I call it - I know, many folks call it the Pullmor growl. But it annoys me that I would have to pull the main spur gear just to get the armature out. I would like to clean, inspect and lube or even replace the armature bearings. But I probably won't - not worth the effort as long as it's running this well. Besides. most bearings I've gotten from train parts vendors, even those that are NOS from Lionel don't really seem to offer the perfect fit. McMaster Carr on the other hand has provided a number of near perfect bushings, plus i can get longer ones to install (where there's room, of course) to get a more solid bearing surface. 

Well, I thank all of you who responded with clarity, mind boggling reading, and humor!! Thanks!

George

@jhz563 posted:

With just a little bit of backlash!!

Sort of like marriage! 

 George where gears are adjustable I run them with as much engagement as possible without the teeth bottoming out. If the bearings are snug so the shaft does not have a lot of runout I use a sliver of heavy typing paper about 1/8" wide and press the gears together with the paper at the contact point then tighten them down and rotate to remove the paper.  Most model trains the lash is built in and the only thing governing is how snug the bearings are.  I saved all the gears from my slot car days and they have come in handy in a couple of bashing projects. The motor that came with the O scale Rivarossi Casey Jones kits were small for an HO loco so I made a intermediate box and use a pair of 2:1 bevel gears to turn a shaft with a 8:1 worm and wheel and powered it with a mabuchi 385. The bevel gears were way to noisy for todays sound systems.  I have a Maxon motor that I want to put in that Casey Jones loco and get rid of those bevel gears. Just need to figure how to get a worm on that coreless motor shaft. It is very difficult to press gears on coreless motors without destroying the rear bearing. Likely I'll drill the worm out a couple thousands larger than the motor shaft and solder it on.          j

Link to all the info on gear theory you ever wanted to know.

https://khkgears.net/new/gear_knowledge/

I recently bought a Williams brass USRA 2-8-2 off Ebay.  Haven't tried running it yet because the rubber traction tires were rotted away.

Yesterday I took it apart to replace the tires (I'm becoming quite good using 2 tiny screwdrivers, a clamp to hold the new tire in place, and both hands to do this ), when I tried to turn the drivers I noticed how stiff they were to turn.  I couldn't pinpoint the issue at first, thinking it was the motor I disconnected it but the problem remained.   I lubed the running gear which helped some, but I noticed when I loosened the steam chest screws it ran better.  I ended up placing a shim (2 washers) between the steam chest casting and the chassis, problem solved.  Now I'm wondering if the other 2 engines I have like this have a similar issue.

I wish I had my old Machinery's Handbook from my days as a draftsman, I'm sure it covered tolerances between worms and gears.

Speaking of worms (in love).  Close, but not this close.  This is just sick.    

[NOTE to moderators:  Penn Central let their copyrights lapse so this image should be OK]

George

@Bob Delbridge posted:

I recently bought a Williams brass USRA 2-8-2 off Ebay.  Haven't tried running it yet because the rubber traction tires were rotted away.

Yesterday I took it apart to replace the tires (I'm becoming quite good using 2 tiny screwdrivers, a clamp to hold the new tire in place, and both hands to do this ), when I tried to turn the drivers I noticed how stiff they were to turn.  I couldn't pinpoint the issue at first, thinking it was the motor I disconnected it but the problem remained.   I lubed the running gear which helped some, but I noticed when I loosened the steam chest screws it ran better.  I ended up placing a shim (2 washers) between the steam chest casting and the chassis, problem solved.  Now I'm wondering if the other 2 engines I have like this have a similar issue.

I wish I had my old Machinery's Handbook from my days as a draftsman, I'm sure it covered tolerances between worms and gears.

Bob I have owned perhaps as many as twenty Williams steamers and I have yet to take a new one out of the box that did not need some tweaking to run properly.  The worst have a high speed drill motor and a 42:1 gearbox, when you run them at scale speeds above 30mph they sound like a mini air raid siren. If that is not enough some of the flywheels have holes which are not centered and could function well as a "Magic Fingers" massage motor.  All I have owned seem to have one of two gear ratios, the infamous 42:1 and a reasonably good 21:1, in an outwardly identical gear box. BTW the early Weaver brass steam locos have all the same problems. Also made by Samhongsa. I still have four of these Williams steamers and one Weaver all new in their original boxes. A related discussion started by engineerjoe, a few weeks ago prompted me to pull them out and give them a test and tune. I plan to post a thread on what I found and my solutions as soon as I finish. I'm on the last one.          j

@Bob Delbridge posted:

... when I tried to turn the drivers I noticed how stiff they were to turn.  I couldn't pinpoint the issue at first, thinking it was the motor I disconnected it but the problem remained.   I lubed the running gear which helped some, but I noticed when I loosened the steam chest screws it ran better.  I ended up placing a shim (2 washers) between the steam chest casting and the chassis, problem solved. 

Bob the wheels on a Williams loco are not supposed to be back-drivable.  It's a self-locking worm gear drive.  You can damage the mechanism if you try and turn the wheels with the motor stopped.  If you're referring to the 1989 "Crown Edition" Mikado, it has a SAMTech (Samhongsa) gearbox that determines the mesh between the worm and worm wheel.  It's a well-made piece.  Unless the gearbox clamping screws are stripped, it's not adjustable.

Shimming the steam chest might have resolved a bind in the side rods, valve gear, etc.  There's no way it could have affected anything related to the gearbox, motor, or worm.

EDIT: John I agree with you regarding the unbalanced flywheels.  A lot of Williams locos had that problem and it's easily solved.  I disagree with you regarding the gear ratios.  For years, high quality O scale models like Lobaugh, Max Gray, US Hobbies, etc., used ratios around 30:1 or higher and proudly proclaimed it in their advertising so customers knew they weren't buying a toy.  Those motors were probably slower-turning than what we have today, no one cared about the loss of top speed.  The motors were mounted in rubber grommets to quell vibration.

IMO 36:1 is about ideal for steam and 21:1 is too fast for realistic operation.  Friction increases suddenly when the loco enters an un-eased sharp curve as found on most 3-rail layouts.  Rubber tires make this problem worse because they prevent the wheels from skidding.  So the loco slows noticeably, ruining any illusion of realism.  It's most noticeable when the loco is running light, such as when easing out of the engine house.  You need a LOT of torque and flywheel RPM to prevent this slowdown.   By switching to a taller ratio, you're leaving slow-speed smoothness on the table in exchange for 100 mph top speeds that have no place on most home layouts.  If the problem is NVH, then solve the problem.  Don't dumb down the gear ratio to avoid it!

Here's another post I stumbled across that touches on the mesh between worm and worm wheel: 

https://ogrforum.com/...5#146423788496769985

Ted, oops.  What I should have said I was trying to turn it by rotating the flywheel with my fingers.  I could tell it wasn't right just by that.  The shims under the steam chest solved the problem, the guide rods did look a bit odd, but not by much.

@Ted S posted:

Bob the wheels on a Williams loco are not supposed to be back-drivable.  It's a self-locking worm gear drive.  You can damage the mechanism if you try and turn the wheels with the motor stopped.  If you're referring to the 1989 "Crown Edition" Mikado, it has a SAMTech (Samhongsa) gearbox that determines the mesh between the worm and worm wheel.  It's a well-made piece.  Unless the gearbox clamping screws are stripped, it's not adjustable.

Shimming the steam chest might have resolved a bind in the side rods, valve gear, etc.  There's no way it could have affected anything related to the gearbox, motor, or worm.

EDIT: John I agree with you regarding the unbalanced flywheels.  A lot of Williams locos had that problem and it's easily solved.  I disagree with you regarding the gear ratios.  For years, high quality O scale models like Lobaugh, Max Gray, US Hobbies, etc., used ratios around 30:1 or higher and proudly proclaimed it in their advertising so customers knew they weren't buying a toy.  Those motors were probably slower-turning than what we have today, no one cared about the loss of top speed.  The motors were mounted in rubber grommets to quell vibration.

IMO 36:1 is about ideal for steam and 21:1 is too fast for realistic operation.  Friction increases suddenly when the loco enters an un-eased sharp curve as found on most 3-rail layouts.  Rubber tires make this problem worse because they prevent the wheels from skidding.  So the loco slows noticeably, ruining any illusion of realism.  It's most noticeable when the loco is running light, such as when easing out of the engine house.  You need a LOT of torque and flywheel RPM to prevent this slowdown.   By switching to a taller ratio, you're leaving slow-speed smoothness on the table in exchange for 100 mph top speeds that have no place on most home layouts.  If the problem is NVH, then solve the problem.  Don't dumb down the gear ratio to avoid it!

Ted lets not put words in others mouth. While 21:1 is not my ideal it is a FAR better ratio than 42:1 unless you care nothing about having a mini siren run around your layout with the motor screaming at 16-20k rpm. At those rpm no removable flywheel is going to be concentric enough to not vibrate a thin brass boiler to distraction. It is also an improvement over the 16~18:1  found on Lionel and MTH locos.    So far I have seen only two ratios on Williams gearboxes 21:1 and 42:1 not that I claim to have seen every gearbox they ever put in a loco. I hear people talk about a 44:1 but have never seen one nor would I want to. I have about 30 two rail brass locos and their gearboxes all fall between 25:1 and 32:1  I would readily concede that is the sweet spot for a DC powered conventional controlled loco. Even those with universal motors like the seven pole K&D and the nine pole Lobaugh preform well at those ratios. It is undeniable that digital control is here to stay and it does a commendable job of allowing the 16:1 gear box to operate smoothly at 2~3 scale mph and cruise control will hold it where you set it. I'm more than happy with all it offers at 16:1 or even 10:1 on diesels. 

   Since this current thread on gearboxes, ratios, flywheels and wheel travel got started a couple of weeks ago I pulled what Williams and Weaver steamers I have left out of the closet and have been swapping the 42:1 boxes and the 21:1 boxes around so locos that I am likely to run slow have the 42 and locos which are likely to pull passenger trains have the 21 box.  The most significant thing I found that differs between the two gearboxes is the worm.  The worm on the 42:1 box is a single helix worm and the worm on the 21:1 box is a double helix worm. So where the 42 box turns the helical spur (worm wheel) one tooth for each turn of the worm the 21:1 box turns the helical spur two teeth for each revolution of the worm thus the precise doubling of the ratios between the two boxes. I am working on the last of these locos and have made photos. When I finish this last one I will post what I found and what I did.        j

@JohnActon posted:

Ted lets not put words in others mouth. While 21:1 is not my ideal it is a FAR better ratio than 42:1 unless you care nothing about having a mini siren run around your layout with the motor screaming at 16-20k rpm. At those rpm no removable flywheel is going to be concentric enough to not vibrate a thin brass boiler to distraction.

I'm sorry, no offense, I didn't mean to put words in your mouth.

I prefer die-cast bodies for this, among other reasons.  For example, I was told that the Williams by Bachmann "Old Timer" 4-6-0 is geared at 44:1.  I don't own one, so I'm not sure if this is true.  Many people say that it's one of the best "conventional" runners, and I haven't heard many complaints about noise.  One trick I learned to quiet down brass is to install a ~3" x 3" square of DynaXorb inside the boiler shell directly above the flywheel.  DynaXorb is a soft vinyl used to line the inside of loudspeakers, car stereo installation, etc.  It really helps!

My train room is 18 x 11 so I don't have the straightaways for passenger train speeds.  If a loco can make 40 mph it's fast enough for my railroad.  But I agree that speed control can force even a poorly-geared train to run well.  I would love to see the manufacturers build more steam locos geared in the 25:1 to 32:1 range, so they will run well with any control system.

Based on what you said it sounds like Samhongsa used the same gearbox on all your Williams models, and just substituted the worm.  I think I read a long time ago that the Weaver USRA 0-6-0 (which was also made by Samhongsa a few years later) used a 25:1 gearbox.  The prices on these have come way down so if you can get a deal you might want to check one out, just to see what's different about the gearbox.  I look forward to reading more of your findings!

I have done a few Williams brass steamers with the 44:1 gearbox, and that's too high a ratio IMO.  I also agree that the 18:1 is not an optimum value either, too bad they couldn't have split the difference. 

Regardless of the gear ratio however, I still think that speed control is a must-have option.  Opinions vary, but IMO it'll be a rare layout that you can run on and not see significant variations in speed without speed control.

IMO  Worm shaft, (or motor shaft with a worm gear applied), should be tight with no end play, matched to a mating gear with the same bevel cut.  A different look, this is a turntable worm and associated gear. A worm should operate smoothly either direction.  First check, if not smooth, would be end play on the worm shaft.  Shaft bushings pictured below are tight against a brass insert, either side. 

IMO Same should applied to either a diesel wheel set, or a steam locomotive drive box.  IMO  

@MikeCT .....lemme make sure I’m reading your wording correctly?......when you’re referring to the end play of the shaft, you mean the driven shaft from either a motor or bearing support??...correct?...because there should be play between the worm and worm wheel....that “play”” or backlash is the space needed for lubricant of whatever is designed to be used, be it grease or oil.....just making sure that’s clear....the gears themselves ( in theory) should ride against a thin layer of lubricant, not each other or total destruction will occur....just don’t want folks getting the wrong idea and attempting to smash gears together.....that’s like the first fundamentals taught in engineering.....😁

Pat

@harmonyards posted:

@MikeCT .....lemme make sure I’m reading your wording correctly?......when you’re referring to the end play of the shaft, you mean the driven shaft from either a motor or bearing support??...correct?...because there should be play between the worm and worm wheel....that “play”” or backlash is the space needed for lubricant of whatever is designed to be used, be it grease or oil.....just making sure that’s clear....the gears themselves ( in theory) should ride against a thin layer of lubricant, not each other or total destruction will occur....just don’t want folks getting the wrong idea and attempting to smash gears together.....that’s like the first fundamentals taught in engineering.....😁

Pat

Picture shows a lubricant, left edge, upper corner.   One problem with a lot of diesels or locomotives is the grease in the gear box can be improperly applied, or dry, from years of storage.  Should be checked.  IMO.  

@Mike CT posted:

Picture shows a lubricant, left edge, upper corner.   One problem with a lot of diesels or locomotives is the grease in the gear box can be improperly applied, or dry, from years of storage.  Should be checked.  IMO.  

Just curious, what are you referring to when you say some folks apply the grease improperly? Is that like filling the gearbox but didn't get any on the gears?

@GeoPeg posted:

Just curious, what are you referring to when you say some folks apply the grease improperly? Is that like filling the gearbox but didn't get any on the gears? 

Yes.