Lionmaster Big Boy Problems

That test of motors is not valid.  The motor with the tach reader provides feedback. So it you try to stop it, the circuit adds more voltage to keep it going.

If you try to stop the none tach motor, it is on a fixed voltage (low in your case).  Stopping it is easy as no more voltage is applied because there is no mechanical coupling via wheels and track.

Spray clean the motors, ensure no debris in gear box of front motor, reassemble and try again.  But some minor jerkiness at speed step 1 may just be normal.  G

That's good to know about the motors. I will try cleaning the motor as I have some cleaner. The jerkiness does show up through about speed step 12 and then stops at higher speeds.  It didn't use to do this at all. At speed step 10 it can really get lurching causing the tender to smack back and forth. I have already lubed everything and verified that the gear box turns smoothly.  

Also on a side note, if I really tighten down the single screw that holds the wheel assembly to the motor, it makes the jerkiness worse.  I've been careful to make sure no wires are getting stuck between the two when reassembling. If I loosen the screw a little bit it helps but then over time it can loosen more and fall out. 

I've looked closely at the worm drive shaft on the motor and it almost seems like it has a slight bend in it but it's hard to tell as the worm gear itself makes it hard to tell with the way it spirals. Maybe a slightly bent shafts would cause the motor stalling. Do they even offer replacement motors? I couldn't find one on the lionel website using the model number.

What you describe is likely an issue with the motor shaft or possibly the power truck. I had a locomotive some time back that I had to shim the motor very slightly to tilt the worm a bit for proper engagement with the truck gear.  It's still running fine, though it pained me to have to fix it that way.  It had the same symptom, it ran good if I loosened the screw half a turn, but obviously the screw would work it's way out and cause a larger issue if I left it that way. 

If this is on the motor with the speed sensor, you'll probably have to contact Lionel to see what parts are available.  There may be another model like the Lionmaster Challenger that uses the same motors, hard to say.

Edit:  I presume you HAVE removed the rods to see if this is an issue with one of the rods or the non-driven wheels binding and not really the motor or gears, right?

Thanks for the advice.  I did remove the motor and verified the wheels all turned freely without binding.  I followed your suggestion and shimmed the motor and it seems to have solved the problem.  It is running smoothly now. You guys are awesome!

I cringed when I did my shims, but as you say, it did solve the problem.  Glad it worked out.

Don't know anything about that particular engine.  However if the drivers spin well when totally disconnected but stutter when connected that could say quartering is not right.

Tom, since changing the angle of the motor mesh to the truck gear solves the problem, I don't see how quartering would be the issue.

A dial indicator on the motor out put shaft checking for the perceived runout mentioned above would be interesting.  So would a dial indicator on the face of the gear's teeth.  

I like to isolate every mechanical  function.  When there is a bent shaft the drive force can vary even to the point of a hesitating falter.  If a gear's axle is a hair off center there can also be a faulter. 

If there is a slop, a shim forcing certain contact could override a falter.  That may be a false sense of success just delaying a subsequent bearing or gear mesh failure down the road.

Secondarily,  the wheels need to be checked for runout.  Then check for quartering, then check for equal rod lengths  and rod pin placements.

Diesels have an easy drive to produce.   Steam engines another story. I have seen quite a few diecast, unsprung, captured axle steam engines demonstrating erratic behavior.

Each and every mechanical dynamic needs to pass muster on it's  own designed merit.

If a designed  transmission does not work as presented, rework needs to take everything into consideration.

Example:  You may silence an automotive front engine accessory bearing squeal by loosening or tightening tension on a drive belt but the problem has not been solved, only the symptom  has been addressed.

My favorite quote:

"I'm not an expert, I only play one on the forum."

Tom, all certainly good things to check, but if you did that for every problem, simple repairs would take hours, not to mention require tools that many folks probably don't have.

Agreed John.  Most things on our RRs can be a simple fix with common hobby tools.  Many times a fudge fit will git 'er done. 

What set my words running on was the perceived note on 1/6 @ 9:45 AM of a shaft runout. 

Bind due to wheel quartering can be a real pain to isolate if you are not looking for it. That was just another suggestion.

Shimming a worm over a gear would cause me to want periodic inspections at the least.  The shaft centerlines of the worm and the gear were designed with performance and durability in mind.   My primary concern was performance at the cost of durability.  That engine should run smoothly for years as manufactured w/o shims. 

When I reentered 0 gauge 23 years ago my first five engines  (some new some used)   were dead on arrival each with a different problem.  Some real sharp guys lead me through a steep learning curve much like what we all experience on this forum.  Much like yourself,  I always look to pay forward some of the things I have learned.

That experience gave me pause.  I want to know the "why" of things.

Thank you for your comment.

PS: for the casual tinkerer Harbor Freight has a dial indicator for $16.99 and a magnetic base with fine adjustment for $12.99.

No disagreement on the shims Tom, the one that I had to do that to was an MTH diesel.  I cringed when I put the shim in and tightened down, but it's run ever since.  I did check the gears recently, I didn't see any signs of wear.  I confess I didn't have a dial indicator to test, I just "eyeballed" it.  Since I got it used, I don't know if someone dropped it on it's head, or what.

John, I have been on the receiving end of your workmanship and I am sure anything custom you would do would be done the best way possible!   Thanks for what you bring to the game. tt

Well, replacing the motor and/or the truck would have probably fixed it as well, but for a RailKing diesel, it just wasn't worth the expense!