brass engine binding


gregc

gregc

Apprentice Modeler
i just received a brass 0-6-0 engine by Gem i acquired on ebay for what i thought was a very reasonable price. but after reading about how old these engines are, and craftmanship at the time, i wasn't sure it would even run. furthermore, it has a motor that sits vertically and mates with the drive gear between the axles. the motor is stamped with KMT.

i was relieved to see that the motor works, and could work at low speed. but i quickly saw that something was binding. it looks to me that it's the crosshead, the part connecting the rod going into the cylinder and the coupling rod connecting it to the driver. it looks like the rails it slide on are too tight at the far end of its travel closest to the cylinder.

i bought the engine to run, not as an investment. some cleaning, filing and bending of the crosshead rails helped. and while it was most pronounced on the one side, i realize the same problem in on the other.

is this a typical problem? should a little filing fix the problem?
 
Before you remove metal from anything, there are some checks you should make. Rermember, you can't put the metal back once it's gone. This assumes you have the necessary mechanical skills.

Remove the boiler from the chassis. There are usually three screws, one in front through the cylinders, and two at the rear under the cab.

remove the gearbox from the driver it is connected to. There should be two screws under the model at either end of the gear.

Roll the chassis and see if anything binds. Clean out the old grease form the gearbox and check both the motor and gearbox for binding. Lube them.

While old, these models generally ran well, especially anything by KTM. Detailing was not up to modern standards, but the mechanisms were well engineered. If you have a bind in the running gear something is out of whack. The most common problem is an out of quarter driver pair. This makes the model lope as it runs, and no amount of filing will fix it, only re-quartering. You can look for the bind by rolling the mechanism on a smooth surface until it binds, and look for the tight spot. You can also remove the main rods (cylinder to driver and see if the mechanism rolls without them in place. This can be a painstaking procedure but it will work, and with an 0-6-0, you should find the problem without too much trouble. one thing, do not file out or enlarge the rods themselves. There are no replacements for these handy unless you find another model, or are lucky enough to know someone with a huge section of old parts.

Can you post a photo?
 
Espeefan said:
Can you post a photo?
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the crosshead rides between two rails. i believe the rails are not far enough apart nearest the cylinder. i determined this by disconnecting (desolder) the coupling rod from the rear driver and moving the crosshead by hand through its range of travel.

i measured the distance between the crosshead guides: 0.162"(right) and 0.158(left) closest to the cylinder, 0.170 about midway and 0.165 farthest from the cylinder. the crosshead measures 0.192 from top to bottom. the crosshead gets as close as 0.090" to the cylinder.

another possibility i haven't ruled out is that the cylinder rod itself may be binding against something in the cylinder.
 
gregc said:
the crosshead rides between two rails. i believe the rails are not far enough apart nearest the cylinder. i determined this by disconnecting (desolder) the coupling rod from the rear driver and moving the crosshead by hand through its range of travel.

i measured the distance between the crosshead guides: 0.162"(right) and 0.158(left) closest to the cylinder, 0.170 about midway and 0.165 farthest from the cylinder. the crosshead measures 0.192 from top to bottom. the crosshead gets as close as 0.090" to the cylinder.

another possibility i haven't ruled out is that the cylinder rod itself may be binding against something in the cylinder.
Click to expand...

Oh yes, the camelback! It's very unlikely that the crosshead guides are too close together unless there has been damage to the model. I didn't see any in your photo. That sort of defect would have been caught during testing at the factory. Also, the cylinder rod does not travel al the way forward. The cylinder itself is not solid, so all the piston rod only travels through is the end cap you see.

Have you disconnected the motor yet and roll tested the mechanism? I'm still voting for an out of quarter driver pair. That's the simplest explanation, and these sorts of problems tend to have a simple explanation. Disconnect both main rods and see if it still binds. A correction to my earlier post: on this model the two rear boiler mount screws should be back by the fireman's footplate. You've got to get the hotor disengaged for roll testing. On this model, the worm is either soldered or set screwed to the motor shaft, and all you have to do is remove the motor from the frame.

Be careful not to break the crosshead guides loose from the cylinder assembly. That repair would require resistance soldering gear, and keeping everything in line can dbe difficult! Go through one step at a time.

If you don't have a NWSL quartering jig, you should get one.
 
gregc said:
see previous
Click to expand...

Understood. Make sure you roll test to check the driver quarter. These mechanisms are funny in that a problem in one place can manifest itself somewhere else, kind of like that old story about the dentist that pulled the tooth that hurt, but was not the problem. Don't be that dentist! :)
 
Espeefan said:
Understood. Make sure you roll test to check the driver quarter.
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I did this, with the motor removed, and the crosshead rod both connected and disconnected, and came to the conclusion I've stated. But maybe I fixed one problem, and there's still another. I assume the acid test is to try this with both crosshead coupling rods removed?

My understanding of quartering is that the drivers on both sides don't actually have to be mounted at 90 degrees to one another. But all the drivers on one side must be mounted at the same angle. is a quartering tool such as the one from NWSL needed to fix this problem? Is this what you think the problem might be?

Espeefan said:
... kind of like that old story about the dentist that pulled the tooth that hurt, but was not the problem. Don't be that dentist! :)
Click to expand...
Ironically, a similar problem did happen to me. I went to a doctor because of headaches, who treated me with antibiotics. But it turned out to be an infected wisdom tooth that needed to be pulled.
 
The acid test would be to disconnect both main rods, and roll test the mechanism to make sure there are no running gear issues. If there are none, then bend or file the giudes as necessary for proper clearance.

You are correct, 90 degrees isn't necessary, just the same angle. You could do 60 degrees if you wanted, but most models are done at 90 degrees. Some three cylinder models use different timing but that's onother subject and we don't want to get into running gear setup and valve gear prototype operation.

A quartering jig will set the drivers at 90 degrees. It is best to have one handy. I know a few guys who don't need one (including me, after many years of practice:)) but it's nice to be able to have the gauge to check them with...to be sure. It's tough to troubleshoot without the model in hand. I was just thinking simplest things first and wheelset gauge & driver quarter are the two most common problems with brass. If you fix the problem by working on the crosshead guides, that's great. I just was advising care, as you can't exactly run down to the LHS and get parts for these models any more! Let me know how you do!
 
I have seen cross head guides that were soldered to tightly together at the cylinder end before on a PFM C&S 2-8-0. I had to unsolder them and resolder them to correct the binding. Anything is possible on older brass models, KTM was good, but not the top builder or drive system by any means. PFM/United, Tenshodo are usualy more bulletproof. The KTM diesel drives can be made to run fairly well with all wheel pickup being added. My troubleshooting would be to remove the rods to the cylinders from the drive wheels, then recheck for binding, if its gone, then there are no driver quartering issues and the problem lies in the crosshead guides. You also can try moving the cross head back and forth by hand to check for tight spots. I think you have it found as well, just take your time. Nothing better than a fine running brass engine!
 
i found that with both crosshead coupling rods disconnected, the frame would roll easily. After a little filing and polishing of the corsshead guides, the problem was at least significantly reduced and the frame seems to roll better even with the crosshead coupling rods connected.

But I was looking at a picture of painted engine (below) with the coupling rods including the crosshead guides, painted. Considering the tight clearance required between the crosshead and the guides, I find it difficult to believe that the crosshead guides can be painted, as in the picture and the engine be operable. Are crosshead guides, or any parts requiring tight clearances, normally painted?
 
Don't know for sure but the valve gear may have been turned black with something like Blacken-It from A-Line. That wouldn't cause any increase in diameter of the parts since it's just a chemical reaction of the brass. I know that's what I would use rather than paint.
 
malletman said:
KTM was good, but not the top builder or drive system by any means. PFM/United, Tenshodo are usualy more bulletproof.
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Yes and no. United or Tenshodo running gear was excellent quality but lots of coffee grinder gearboxes!

malletman said:
The KTM diesel drives can be made to run fairly well with all wheel pickup being added.
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Let's not confuse Katsumi Mokeiten (KTM) with KMT whose early diesel drives are notorious for gear failures. KTM had excellent gearboxes and motors. PFM running gear with KTM motor & gearing would have been just about perfect!

malletman said:
My troubleshooting would be to remove the rods to the cylinders from the drive wheels, then recheck for binding, if its gone, then there are no driver quartering issues and the problem lies in the crosshead guides. You also can try moving the cross head back and forth by hand to check for tight spots. I think you have it found as well, just take your time. Nothing better than a fine running brass engine!
Click to expand...

Take note of how far forward the crosshead travels. It should stop short of bottoming.

You can paint the grosshead guides but the paint will wear off rather quickly where moving parts rub. "Blacken it" might be better, but not sure how it stands up to rubbing...probably the same issue. I usually leave these parts unpainted.
 
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Espeefan said:
KTM had excellent gearboxes and motors. PFM running gear with KTM motor & gearing would have been just about perfect!
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Encouraging to hear. I've never seen a vertically mounted motor. (see photo).

Espeefan said:
Take note of how far forward the crosshead travels. It should stop short of bottoming.
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yes, it stops about a 16th inch from the cylinder.

Because of the binding, i'm not sure how much use this engine has had. Does it need to be broken in? Would this help the binding problem? If so, how should an engine be broken in?
 
Some of the PFM gear reduction drives were quite noisy, smooth by noisy due to straight cut fiber gears, like in thier Mallet engines. All the noise in my Tenshodo SD9 is from the same type gears in the tower on the front truck. Might look into different gearing there. The open frame motor is very quiet and powerfull for its age. Looks like your getting it running better. KTM had excellent gear drives, KMT (Kumata) are the ones that are just ok. I have rehabed a few KMT diesels to run smooth as silk, but still noisy. Cheers Mike
 
malletman said:
Some of the PFM gear reduction drives were quite noisy, smooth by noisy due to straight cut fiber gears, ...
Click to expand...

are you saying the shape of the gear causes noise, square cut vs rounded?

how difficult is it to replace the gear on the driver axle, and find replacement gear and worm?
 
The teeth are straight cut instead of at an angle, that combined with the material, which appears to be some sort of fiber causes the noise, both in the PFM Mallets like the Sierra and the C&O 2-6-6-2 and many of the early diesels. The early automotive/truck transmissions were the same way with gear noise. The gears in the PFM Mallets are not on the axle, but on the motor and on the drive shaft going to the gear boxes on the truck. It gave a gear reduction to allow smooth slow speeds using the motors avaible at the time of production, the trade off being the noise. The diesel drives are much like a Hobbytown of Boston drive with 3 spur gears on a tower transfering power from the motor down into the truck. Many of the Kumata drives have a tendency to split thier plastic axle gears like the early Proto 2k diesels do. NWSL makes replacments for them. It is possible to replace the gears in the tower and quiet the drive down, but from what I have read and replaced on my own, they will always have some noise. I kind of enjoy it, these models are now part of the long history of model trains. I get mine running as best as they can and only replace motors and gears when necessary to get them running again. Yes my Tenshodo SD9 is noisy, but she is very smooth. I had to replace the axle gears in my Alco models SW1500 as they were all split. My PFM/Tenshodo USRA 0-8-0 will just creep along nice and slow, forwards or back wards, and nothing other than proper service has been done. She still has the big open frame Pitman motor in her. Enjoy your early brass models, I know I do! Cheers Mike
 
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