Anybody have a Key 2-10-4?

[spookshow]

I recently acquired a Key brass PRR J-1 2-10-4 on eBay. And although it runs quite admirably for the most part, I did notice a very slight bind at the extreme low end of the throttle. After a bit of experimentation, I believe I've narrowed the issue down to the bearing blocks on the driven axle. They appear to have just a bit too much free play where they mount in the frame cut-outs, and with the end result being a bit of a back and forth wobble on the drivers (and thus the binding).

Anybody else run into this? I'm trying to decide if they are all this way, or if it's just mine.

Thanks!
-Mark

[christoph]

My J1a binds a bit when running around curves in one direction (I forgot which one). Did not have the nerve to check the details yet.  My assumption was that I did not handle it with the necessary care 

[spookshow]

Yeah, it seems most noticeable on curves with mine.

Cheers,
-Mark

[victor miranda]

Hi spookshow,

the hitch is from imprecise quartering directly
and from loose bearing blocks indirectly.

if the bearings can move the axle can shift a little when
the quartering is off a wee little bit.  then it binds ... a little.

the 'a little' is best seen at slow speeds.  it also gives you an idea of how bad the
problem may be.
wedge a piece of paper into the gap of the frame and bearing block of the loco and see if you get an improvement.
often one side causes more bind and the other causes less bind.

if the problem is so big you can wedge both sides, the bearing block fit is most likely the only issue.

victor

[nstars]

Our J1 runs flawless, one of the best running brass steam engines we have.

Marc

[spookshow]

Thanks, Victor. It's not enough of an issue that I would even bother trying to do anything about it. Was mainly just curious how common it might be.

Cheers,
-Mark

[alhoop]

Hello Victor - now if EBIT would check in.

Al

[mmagliaro]

Forgive the thread hijack, Mark, but this issue interests me because I am battling with a
Key/Yulim 4-8-4 at the moment (nowhere near the same quality drive as that 2-10-4 you have!)

These notoriously have (in my opinion) way too much fore-and-aft slop in the bearings, so as the
rods go around, the drivers wiggle forward and backward continuously, even though you may not have
a rod bind.

It seems to me that in the current one I'm wrestling with, I have the wheels quartered as best as my
"Eyeball Systems Quartering Device, Model 1000"  can do it.  Yet I can see that as a driver is pushed around by
a rod, sometimes the driver wiggles backward in its bearings rather than go around, and that can be bad news because
now the driver hasn't rotated that little bit, and the rod on the other side was counting on that wheel moving so it would be able to continue the rotation.   

I think that if there are little spots where the driver pushes backward or forward in its bearings instead of turning, because of this looseness in the bearings, it can cause binding problems even if the quartering is correct.

Maybe Victor has an opinion on this.   His suggestion about the little piece of paper intrigues me, becuase I was just about to try shimming the sides of the bearings to get rid of some of this back-and-forth play to see if that
helps.

[victor miranda]

Hi Max,
I am pretty sure you know the next three sentences, I want everyone on the same page.
the side rods and the axles must have the same center to center to run without binding.
the crank throws must  all match to run without binding.
the quartering must all match to run without binding.

of the problems, the quartering is the more common problem.
all problems are 'solved' by putting slop in the axles, usually by letting the bearing blocks roam.
So the brass loco makers get locos to 'go' by opening the bearing pockets.

I can't state the easiest fix.  Deciding what is the cause is the hardest part.
the bind at slow speed is the hardest because it means the 'problem' is very small.
so I try to find the error by removing the slop.... and do not trust the first attempt
take out the axle slop and check the siderods for proper fit.

I have found that some siderods are different center to center than others.
... or that the frame was cut by a distracted worker.

hohohoh! are you sure the driver is centered on the axle?

seriously, the issue here is that you have to both trust yourself and
go to the next item to be checked.
If the quartering seems good, check the axle/siderod center to center
if that seems ok, check for a skewed axle, then crank throws.... it goes on.

keep in mind the size of the error you seek.
If the loco does 5 smph and slows to 3 smph and then back to 5.... 
it is a darned small mistake.

victor

[mmagliaro]

I completely agree, Victor.  In my case, the speed can't really hold steady until the engine is up to about
12 mph.   Below that, it will run with a regular "lope" at one spot in the rotation, and it won't ALWAYS lope - sometimes it will go around.  That makes me even more suspect that it's the randomness of he wander bearings that is
at least contributing to this, if not causing all of it.

It seems to me that unless you get rid of the wandering bearings, it's very hard to even know if you have the
quartering correct.  When the bearings are firmly fixed, you can wait until the drivers rotate around to the "tight" spot where the motion binds.  Then you can wiggle the rods a bit with tweezers and see who is "stuck", which usually gives away which wheel isn't where it needs to be.

I'll try some shimming tonight and let you know what I find out.

I think we have now officially pulled this thread completely off course.   Maybe I should go open a separate one
on this subject, and copy some of the last few posts into an "opening post".

I have now done so.  This bearing block/quartering esoterica is continued here:
https://www.therailwire.net/forum/index.php?topic=32234.0

Now, if there's any more discussion about Mark's 2-10-4, it won't get trampled by the likes of me.

[spookshow]

Gosh Max, you are just so darned polite and agreeable. Tell me again, how exactly did you wind up getting co-opted into this crazy forum? 

J/K

As for this thread, I'm all good. I mentioned the slight creep-speed bind in my review and still gave the model an overall "A" rating. It's just not enough of an issue to ding it down to a "B" (especially given all of the other uber-plus features of the loco).

Cheers,
-Mark

[victor miranda]

there are times when I wish you'd give me a 'heads up' on your sales...

[spookshow]

If you were to friend me up on Facebook ("Spookshow N Scale") you'd get all of the latest announcements 

Cheers,
-Mark

[Mike C]

If you were to friend me up on Facebook ("Spookshow N Scale") you'd get all of the latest announcements 

Cheers,
-Mark

Friend request sent...