How Much Testing Have You Done?

When I've built steam loco kits the instructions were to add drive components one step at a time, and test for smooth running after each addition.
Install Wheels. Then side rods. Then main rod. Then eccentric rod and valve gear.Push with finger to feel for binds at each step,  and do what's needed to remove them. Then add the motor. It might be a bit much to disassemble your loco completely to mimic this, but you could step it backwards. At each step if the binding disappears you've located the source.

Remove motor and gearbox, and push to test.
Disconnect main rods and eccentric cranks at the drive wheels. Replace the screw to hold the side rods to that wheel. Either use a short length of tubing as a bushing to replace thickness of the removed pieces, or use a shorter screw. Push to test. . This is the test for out-of-quarter and for sloppy holes in the rods.
If it's still binding Remove side rods. 
With no rods remaining, remove each pair of drive wheels and look for rough edges or excessive wear in the bearings. Replace the wheels and test.
Then install and test each pair of side rods with the other wheels free, to try to locate which wheelset is off.

This will take some time, but it should pinpoint the problem better than making intelligent guesses.

Good luck,

DrJolS

Help with a brass steam loco

DrJolS:

Thank you for the step-by-step method to diagnose the problem. I will try this over the weekend. Thank you.

Robert Gross

A couple of other things to

A couple of other things to check before you begin the tear down. see if any of the screws holding any of the side rods draft gear are so tight that they cause binding, and check to see if the toothed driver is installed so as to bind with the others, sometimes just rotating it one tooth will eliminate this. Often a removal of the bottom plate on the space between the drivers will allow this to be checked. These checks are quick and easy and would also show if there is any foreign matter inside the gear area, like hardened grease.

If neither of them turn anything up I would begin the excellent step by step outlined above.

Good Stuff

Rob:

Thank you for your first steps. I'm adding them to my checklist.

DrJolS

Drive Shaft Kink?

Possibility: The motor shaft and drive shaft are not aligned.

Dante

Help with a brass steam loco

Dante:

Thank you for the comment. Can you elaborate?

Robert

The motor shaft and drive

Motor shaft higher than worm gear shaft, thus an angle in the drive system.

Bernd 

CSI Brass

Robert,

You have gotten some good advice here. I have found variations on a couple of points of view on fixing brass to run well:

One is the tear it down and build it back – works well if you are a good mechanic and have some experience in the area.  Drawback is that it is easy to take it all apart, and rebuild it to run worse than before.  Easy to do if you miss something (don’t ask how I know this).

The other approach is slowly try some minimal tweaks until it runs – sort of a CSI Brass if you will – general theme is don’t fix it if it ain’t broke.  Diagnosis in this area can be difficult and some locos can take a long time to track down and fix all the issues.

There are lots of reasons why brass will bind. First thing is definition of a bind:  Are we talking constant drag or friction?  Is this a click or a momentary jerking or slowing that happens intermittently?  Does the loco run great and then suddenly jerk or start running slowly? The type of binding will help suggest causes.

An intermittent bind can be running gear and rods that will move around and get caught as the loco goes around the track.  It can also be a miss-alignment of the gearbox and motor shaft (vertically or horizontally), there can also be parts such as a cylinder that have come loose are catching something as the loco moves.

A more constant bind is one that can be caused by a bad drive train (clogged gear box, poor meshing of gears, fried motor, too much shaft movement in the gear box, worn gears - to name a few).

My first suggestion would be to run it on the bench, in the air and see if it binds, if yes do a visual on the rods and valve gear with an optivisor to look for contact that is causing the bind.  Next would be to remove the coupling between the motor and gear box and roll the loco on a plate of glass to see how smooth it is – it should roll easily with no catches - these tests will suggest some areas for you to explore depending on what you find.

In looking at you photos, ideally the drive train should be aligned so that the motor shaft and the gearbox shaft are at the same angle so a straight line can be drawn along the length – notice that the motor is pointed at an angle and the gearbox is level. BTW: The coupling is supposed to allow for minor angle errors, but there are limits.  Does the gearbox move on the shaft to match the angle of the drivetrain? You can test to see if this is part of the problem by disconnecting the motor shaft and rolling the loco - if it rolls without a hitch you might try adjusting the mounting of the motor or realigning the gearbox with shims etc. to get the angle to match.

Another suggestion is that you find a local brass guru if possible.  I have been saved many times by our local expert. Tracking these types of things down can be frustrating and time consuming.  I have one loco that took a year of problem solving and intermittent frustration to fix all the issues. I worked on it for a while and then would put it back in the box for later when I got to a dead end. It runs well now……Hopefully you can find the problem more quickly.

Good luck,

Guy

While you are rebuilding...

You might try that Nano Oil that is advertised on the forum.  It is supposed to allow parts to move more freely than with using regular lubes.  Nano oil also reduces voltage draw.

Another thing that could be causing you issues is that aged lubricant can harden and crack.  That can cause binding as well.

Den

Gradual teardown

I would start by looking at the mechanism run withut the boiler to see if I can find and binds or rubbing.  Look from both sides.  Listen, see if you hear anything rubbing.

Then remove the motor.  That should tell you if the bind is in the motor or in the gears, wheels and rods. Roll it by hand.  Where does it bind?  Is it when the side rods are in the same place? (problem with wheels, side rods or valve gear)  Does it happen at "random" places?  (problem in gears)

If you still have a bind, start taking off the valve gear, then the side rods.  At each step, rolling model back and forth to see if the bind is still there.  Don't take off more than you need to or you will never narrow it down.  If you atke off all the side rods then you will not know which part of the rod or which driver has a problem.  If you take off one piece or collection of pieces at a time you can feel when the bind changes, and that will narrow down your problem.

Visual is important

As the others have said, you need to take it one step at a time.  I have found that only slight deformations or bends can be the culprit.  These will usually become apparent visually during the motor removed free rolling tests.  

The bind is almost always associated with the wheels and rod assembly.  It is likely a conflict between a rod and bolt head.  The bolts frequently will start to work themselves out causing the interference.  

The proper bolts should seat with enough clearance for the rod movement.  These fixes always take time and are often a culmination of small issues. Good luck.

Great Advice for Brass

Everyone,

This is an excellent forum. The advice given with the links have provided me with some new ideas to look for as well.

I too have "a project brass loco" in a box that frustrates me that will not pass the "glass test". It is my opinion if you can get past this test you are well on your way. I would add that you should do the glass test after each step as you go. This will help narrow down a specific piece of the mechanism to focus efforts on before moving to the next step. 

Thanks for the additional step by steps. A lot of experience here to help, and thanks for passing on the knowledge!! 

Scott 

Help with a brass steam loco

You've gotten some good advice. One of the things I do is remove the gearbox and see if the chassis will roll down an incline. If you have to go greater than a 10% grade to get it to roll on it's own, then you probably have a problem. The reason I use the incline rather than my finger is that you won't be influencing how it rolls. If you are planning on working on a lot of brass steamers I recommend purchasing a North West Short Line quartering tool and puller. While you're on the  NWSL website order some "Wimpy Springs". These springs work great. One of the common problems with older HO scale brass is that the springs are too heavy. These wimpy springs will allow the drivers to work up and down freely when going over imperfections in the track, and they make a big difference in how an engine runs. 

As one of the previous people mentioned, a common problem is old grease that has become hard over time. If you can afford it get an ultra-sonic cleaner and degrease all of the working parts. Then re-lubricate with grease in the gearbox and light oil on everything else. Nano oil is a good place to start, but there are other products too.

Another thing to focus on is the electrical circuit. Poor electrical connections combined with mechanical binding means that the motor won't get the voltage it needs when it needs it the most. A high resistance connection causes a voltage drop across the connection and the motor won't get all the voltage it needs. 

As others have said, don't make a whole bunch of changes without testing along the way. Test everything as you go.

Hope this helps. Good luck with your projects.

What I have noticed with my brass

What I have noticed with my brass is that the frames are not always true. They are slightly cocked to one side or the other.

Put the engine on a piece of glass and shine a flashlight at the drivers. Make sure all drivers are touching the glass. If you have some blind drivers make sure they are in alignment.

measure the frame from corner to corner and make sure they match.

I really like the http://www.bachrus.com/ running stands. I can put my engine on it and watch it run.

Good luck.

--Bill B.

Obscure but possible

Sometimes a fully assembled steam locomotive mechanism will run like a fine watch until the boiler is attached.  Brass boilers usually are stiffer than brass frames.  I had an On3 locomotive in which the axles would bind slight only when the boiler was screwed to the frame.  The spring rigging was cast integral with the side frames.  It turned out that one of the cast springs was just barely touching the boiler.  Since the boiler was more rigid than the frame, the frame torqued just enough to make one or more of the axles bind.  A little filing on the spring rigging corrected the problem.  

Typically boilers are attached at three places and so should not rock when just resting on the frame.  It appeared that all three points were seated before the boiler was screwed down, but were not.  Another problem might be that a boiler or frame was assembled incorrectly so that all three points will not sit without rocking, in which case some shimming or other adjustment might be required.  This is just something else to consider.    

Thank you for the info

Thank you for the great info here. I am no stranger to modeling and kitbashing and the like. I am now forcing myself into learning how to tune brass locos. I love the info. I made copies and put it in a binder along with some other info about modeling and tuning brass locos. I refuse to spend the money on new brass locos when I think I have the skills to tune these brass locos myself. I will keep you informed of the progress.

Robert Gross

Brass Tuning

Roll the mechanism down a sheet of glass. It should roll smoothly, no loping.   If it stops, very gently lift the side rods, valve gear etc.   They should be all floppy.  If not , that is an issue.  There have been times when I take off the parts and add them one at a time to find the bind.  Don't accept "good enough"...it will only bug you later!

Also "wimpy" springs are to wimpy for much over an 0-6-0.  I use the medium springs and find they work well.

Rick

Re-motor

Let us know how you get on Robert. I am in the middle of doing a similar job on an old Sierra RR 2-6-6-2 Mallet and we may have shared problems!

Andrew

Check the bearings too

I have had several brass locos that have had trouble with binding, and after I've eliminated the drive train or quartering as a problem, I've found that the eccentric rod is hanging up.

On one PSC engine I have, I found that the brass brushings that are there to keep drive rods, main rods and eccentric crank at the correct distances were either missing or in one case, much too large.  Replacing them with small brass or copper washers has seemed to do the trick for me.  I haven't had an opportunity to run the loco on a layout yet, but on the test stand it has run for several hours with no problems.

Help brass steam loco

block up the engine so you may run it with the wheels not touching anything.  Use the smallest amount of power to move the drivers.  At the point it binds, turn off power.  Lightly touch each rod until you find one that does not have any movement in it.  Look to see if anything is binding on that side.  If you do not find anything remove the that rod, on both sides of the engine.  Start engine running again as above.  If it does not bind, chances are the driver that was disconnected may be out of quarter.  Get a NWSL quartering jig and wheel puller.  Note: first check the quartering of drivers not causing a problem and then see if the suspect drivers match the quarter as the good one.

Remember:  the drivers do not have to be exactly 90 degrees, so long as all of them are the same.

Tom Stamey

Some really great info in this thread

I have tuned up quite a few brass locos over the last 30 years or so and can only echo the comments on here.  My only comment is to work systematically to find the bind.  I'm currently building a brass 0-6-0 tender loco from a kit (uk prototype) and have been going through it to get the smoothest running mechanism.  I do these things when looking for the problem:

1. Disconnect the motor and gearbox first to perform the rolling test.  If there is a bind here, then do the check of which rods or wheel set is tight, and that will hint where the problem is.  I then leave it where it is in terms of the wheel rotation and do the next step

2. Check for any fouling of rods with crankpins, other rods, back of the cross head, brake gear, spring rigging etc.  Look at the back of the wheel rims to see if they are rubbing on the frames, screws, etc (though this usually will announce itself as a short depending on the side.  Hopefully this is where the problem is if the loco had previously run sweetly.

3. If the above two don't fix it, then start removing the valve gear only (leave the connecting rod and coupling rod in place). Do the rolling check again.

4. Remove the con rod and try again.

5. If still binding with only the coupling rods in place, it is highly likely that it would be due to quartering.  To check this, use a bit of brass angle to line up the crank pins in either the 90 or 270 degree position on one side (have the vertical bit of the L against the wheels).  Check the other side to make sure they are all in exactly the same position (they should be perfectly at 90 degrees, but the angle doesn't matter as said before, as long as they are exactly the same).  Use the check of stiffness in point 1 again, this should indicate which wheel set is binding.  If more than one, then you will need to remove one wheel set first, and recheck.  Sort out the first bind and then you can add the  wheel set and connect the rods to sort out the next one.

6. If you don't have a quartering jig, then a tip I learnt was to look through the wheel set and line up the spokes when the wheels are roughly quartered.  If you line up all the wheels the same way, then you should be very close.

7. Once you have sorted the bind through the rolling test, do as was previously suggested and connect up the motor and gearbox (still with only the coupling rods in place) and under very light power with the chassis suspended, run the mechanism.  This will pick up even the slightest bind, so sort that out through the elimination process in 5, it's likely that the quartering might need a fine adjustment.

8. Add the con rods and check through power again.

9. Add the valve gear and check again.

10. Reassemble the loco and check again.

everyone will have their own methods, but this is what works for me, so hope it helps.

cheers

Tony

Electrical Connection

I'm currently working on a Brass Shay which did not run as smoothly as my other locomotives. It ran perfect on test rollers but not so well on the layout.  Suspecting electrical pickup issues a wire was wrapped around the kingpin of one truck and soldered directly to the motor.  Problem solved---it now runs like the proverbial hot knife through butter. For me this solution seemed easier than installing axle wipers or pickup shoes. 

Keep us posted,

Wayne 

Lets assume Accem's Razor is

Lets assume Accem's Razor is correct: the simplest answer is correct. If the engine ran ok before the previous owner changed the motor and now it doesen't, start there. As mentioned above, missaligning. The motor,worm and gears is easy to do. Looking at the picture, there is a lot of fat tape around the motor to isolate it. Try Kapton insulating tape.

If you end up going into the dissasembly phase, work on an uncluttered space, use a box/tray to hold the parts, preferably compartmented. Take before photos and label sub-assemblies.

Good luck, be patient.

Bob Beauty, MMR

Occam's razor ...