need help with a 736

I would guess there is a short on the armature.

Hope this helps.

Richard

I’ll take a guess. It seems like it is over heating. Is the field coil getting hot? Do you smell anything like a burnt smell? I wonder if there is a bad connection, likely to the field that is separating slightly from heat expansion or if there is some type of mechanical temperature fail-safe in the coil? 

If an engine overheats, it probably needs a thorough cleaning and lubrication. I use CRC cleaner.

George

While running, use a pencil and push in on the brushes ans see if it run faster. Looking for weak brush springs.

Check operation / condition of E-unit.

Are the Bulb and smoke unit acting normal

Try running the motor isolated from existing wiring

No smoke? Full out with no movement would probably light up a short!

In addition to above, if the motor is getting hot you might want to check rear driver play.  If a bushing is worn, or a wheel lose on the axle you get a lot of power robbing friction from the back of a wheel rubbing on the frame or the wheel flange rubbing on the blind driver in front of it.

From experience, same with Turbines.

Or maybe too tight a mesh with the gears.

I cleaned the armature with CRC contact cleaner

Held a pencil on the brushes and it slowed the motor down

There does not seem to be anything binding in the drive train

I just installed a new smoke unit and it smokes up a storm but this problem existed before that, it's just been getting worse

A new E unit was installed last year

Maybe there is a short in the motor, I don't know how to check for that

Thanks for the replies

How well does it run in reverse when this happens?

Are you using a transformer with enough power? Minimum of at least 60 watts.

Last Engine that I had do this had a bad armature. Ran good at first then starting drawing more current and ran slower as it warmed up. Check the resistance of the commutator poles. You should get 3 readings. All should be equal or no more than .1 ohm difference. Also check between the 3 commutator plates and the armature shaft. There should be no reading here. 

I don't know if it does it in reverse, I will clear a track and try it.

I am using a cw 80 to run that track

Well, let me give my two cents.
As George said, it could be overheating, as electromagnets do lose their strength the hotter they get.
But the cause of the sudden rise in temperature would be a bit harder to diagnose
Maybe you are using a transformer with a wattage too high for the engine to withstand?
This is sometimes the case when someone uses a modern transformer with a higher voltage/wattage that the prewar engines that they're running aren't equipped to handle. Which is why I always choose to use my A type transformer. Do a bit of research on your transformer and your Kanawha, and see if the two are compatible

Voltage maybe but Watts not.  Plus if you applied to high a voltage the engine would go so fast it would not stay on track.  Transformer is not the issue, unless it is UNDER Sized and it overheats and the voltage to the engine droops. G

GGG posted:

Voltage maybe but Watts not.  Plus if you applied to high a voltage the engine would go so fast it would not stay on track.  Transformer is not the issue, unless it is UNDER Sized and it overheats and the voltage to the engine droops. G

Actually, excess voltage did cause me a few issues very similar to these when I used my K-line transformer on my 257, it became weak over time to the point it couldn't even propel itself, much less a train. Be in mind the 257 had a max running voltage of about 15 Volts, while the K-line transformer provided a max voltage of 20 volts. Thankfully, I know better now.

Try a postwar transformer in place of the CW and see if the results are the same. That voltage spiking from the CW may be the cause, since everything else sounds OK.

Before running engine try cleaning the roller assembly that they spin in and the rollers themselves and see how engine responds after 10 minutes running time. Sometimes this procedure can work well.

Also if rollers are deeply grooved replace them.

The rollers are in good condition.

Would a type Z transformer be ok to use?

A Z would be perfect to try. Note that a Z has more voltage output than a ZW. Around 24 volts. So you won't need to crack the throttle very much.

DM, you are blessed to have the best brains in the business kindly and freely sharing their expertise. One big reason I love this Forum!

It sounds to me that George and Berkshire have identified the likely cause, and Chuck has identified the likely solution. Many other suggestions are excellent in themselves, but do not explain the delayed and pronounced fall off in motor performance.  If using an older transfomer doesn't resolve the problem, look for heat creators. Simple start is to check all wire connections. If too few strands carry too much power the result is heat. If the transformer's circuit breaker is not working well, the result is heat. Wherever there is excess resistance there will be heat.

I tried the engine with the Z transformer and it ran great, did not slow down at all. What I did notice is the 736 takes more voltage than an MPC era engine I have to pull the same amount of cars, 736 16v vs 12v for the 8900, I used a voltmeter at the transformer terminals.

Thanks to all that replied with your help.

The 736 has a heavier duty motor, has a die cast frame vs. a stamped aluminum, and stronger Magne-traction magnets than a 8900.

Berkshire posted:

GGG posted:

Voltage maybe but Watts not.  Plus if you applied to high a voltage the engine would go so fast it would not stay on track.  Transformer is not the issue, unless it is UNDER Sized and it overheats and the voltage to the engine droops. G

Actually, excess voltage did cause me a few issues very similar to these when I used my K-line transformer on my 257, it became weak over time to the point it couldn't even propel itself, much less a train. Be in mind the 257 had a max running voltage of about 15 Volts, while the K-line transformer provided a max voltage of 20 volts. Thankfully, I know better now.

Trust me, it is not voltage.  You can have issues with a modern transformer with a chopped sine wave output which can cause an AC motor to respond different depending on how the manufacture chops it to provide an effective voltage.

Versus the original xformers that are pure AC.  The effective circuit the train and the transformer make via that track control how much amperage is used at a given voltage.  Amps x Volts is WATT.  You need enough Watts to handle the current draw the engine will have.

So I think the op found out he had a combination of chopped wave versus marginal Watts on the transformer.  And if he was trying to run at 12-14V of chopped voltage out of a CW or your K-line the current was higher and causing heat issue in the transformer and motor of the engine.  In the end causing voltage droop and slowing of the engine.  G

Just my 2 cents. I don't think it was voltage drop causing the problem, but heat. The postwar motors don't like chopped waves from a CW. It causes overheating (and growling). The armature windings become very hot and that heat travels down the armature shaft causing the shaft to expand slightly, causing too much tightness at the first bearing in the motor casting. The longer the engine runs, the tighter the shaft becomes in the bearing, causing the motor to slow down. You tend to crank up the voltage a little more to compensate and the cycle continues.

DM, if ever it overheats again just pour ice water over the locomotive and everything will be just fine.😱

HCSader73 posted:

DM, if ever it overheats again just pour ice water over the locomotive and everything will be just fine.😱

OMG! Somebody might take you seriously! Can you imagine the bang?!

George

GGG posted:

Berkshire posted:

GGG posted:

Voltage maybe but Watts not.  Plus if you applied to high a voltage the engine would go so fast it would not stay on track.  Transformer is not the issue, unless it is UNDER Sized and it overheats and the voltage to the engine droops. G

Actually, excess voltage did cause me a few issues very similar to these when I used my K-line transformer on my 257, it became weak over time to the point it couldn't even propel itself, much less a train. Be in mind the 257 had a max running voltage of about 15 Volts, while the K-line transformer provided a max voltage of 20 volts. Thankfully, I know better now.

Trust me, it is not voltage.  You can have issues with a modern transformer with a chopped sine wave output which can cause an AC motor to respond different depending on how the manufacture chops it to provide an effective voltage.

Versus the original xformers that are pure AC.  The effective circuit the train and the transformer make via that track control how much amperage is used at a given voltage.  Amps x Volts is WATT.  You need enough Watts to handle the current draw the engine will have.

So I think the op found out he had a combination of chopped wave versus marginal Watts on the transformer.  And if he was trying to run at 12-14V of chopped voltage out of a CW or your K-line the current was higher and causing heat issue in the transformer and motor of the engine.  In the end causing voltage droop and slowing of the engine.  G

 

Berk's talking about a different issue. You can push too much voltage into poorly lubricated trains and burn them up. This happens with old tinplate made to run at 14 volts. That is not what was going on here.

The CW and its unusual power characteristics was the culprit. The CW performs the worst of all chopped sinewave transformers. It would not run my standard gauge trains at all. 80 watts should be plenty, but they hardly budged. I got rid of it after it ruined one of my old MTH Protosound (1) engines.

George

Don't worry I have no intention of pouring water hot or cold on my engine!

I would not have thought the transformer was the problem, but since it ran great with the Z supplying the power I will stick with a PW transformer for my PW and MPC trains.

Thanks again for the help

Dave

Chuck Sartor posted:

Just my 2 cents. I don't think it was voltage drop causing the problem, but heat. The postwar motors don't like chopped waves from a CW. It causes overheating (and growling). The armature windings become very hot and that heat travels down the armature shaft causing the shaft to expand slightly, causing too much tightness at the first bearing in the motor casting. The longer the engine runs, the tighter the shaft becomes in the bearing, causing the motor to slow down. You tend to crank up the voltage a little more to compensate and the cycle continues.

Chuck, They are related like the chicken and the egg.  You can't get heat without more amps needing to flow, and once you get heat and resistance of wire changes your going to draw more current.  At that point there is a voltage droop. Unless there is designed regulation.  Even generators have the effect.

If you have a voltage an amp meter on a transformer you will see it.  MTH Z-4000 powering a board on the bench tester at 12V and turn smoke on raising current by .4 amps and voltage drops to 10-11V.   It is an electrical relation V=IR and P=VI  or Isquare*R.  Running an MTH train of the test track at 10V I will have higher current then if I raise the Voltage to 13.  Because in the end the power requirement is about the same, so as V go up, current goes down too a point. 

Anyway, it is fixed.  G

George S posted:

GGG posted:

Berkshire posted:

GGG posted:

Voltage maybe but Watts not.  Plus if you applied to high a voltage the engine would go so fast it would not stay on track.  Transformer is not the issue, unless it is UNDER Sized and it overheats and the voltage to the engine droops. G

Actually, excess voltage did cause me a few issues very similar to these when I used my K-line transformer on my 257, it became weak over time to the point it couldn't even propel itself, much less a train. Be in mind the 257 had a max running voltage of about 15 Volts, while the K-line transformer provided a max voltage of 20 volts. Thankfully, I know better now.

Trust me, it is not voltage.  You can have issues with a modern transformer with a chopped sine wave output which can cause an AC motor to respond different depending on how the manufacture chops it to provide an effective voltage.

Versus the original xformers that are pure AC.  The effective circuit the train and the transformer make via that track control how much amperage is used at a given voltage.  Amps x Volts is WATT.  You need enough Watts to handle the current draw the engine will have.

So I think the op found out he had a combination of chopped wave versus marginal Watts on the transformer.  And if he was trying to run at 12-14V of chopped voltage out of a CW or your K-line the current was higher and causing heat issue in the transformer and motor of the engine.  In the end causing voltage droop and slowing of the engine.  G

 

Berk's talking about a different issue. You can push too much voltage into poorly lubricated trains and burn them up. This happens with old tinplate made to run at 14 volts. That is not what was going on here.

The CW and its unusual power characteristics was the culprit. The CW performs the worst of all chopped sinewave transformers. It would not run my standard gauge trains at all. 80 watts should be plenty, but they hardly budged. I got rid of it after it ruined one of my old MTH Protosound (1) engines.

George

That is not what he said, he said he switched transformer and it resolved.  Even with the correct transformer and poor maintenance or a stall, you will raise current in motor and overheat or damage it.  But a good motor would just try to go faster at higher voltage and you would never raise it to the max.

MTH standard gauge traditional (AC Motor made in china (poorly)) runs fine on a Z-4000 more closely AC sine and up at 22-24V will work fine.  You just never raise voltage that high.  G

 [Droopy]: dr-ew'-ew-py: adj: describing how less voltage changes speed of engine on three rail:

Wikipedia suggests that "Droopy Voltage may cause slower running, as in Less voltage = less speed.... "

Miggy posted:

 [Droopy]: dr-ew'-ew-py: adj: describing how less voltage changes speed of engine on three rail:

Wikipedia suggests that "Droopy Voltage may cause slower running, as in Less voltage = less speed.... "

Who knew?! I thought George was making that word up.

George S

Me make up things, no way.  G