Lionel 6-31960 Polar Express smoke unit leaking

[CanadianCN]

Need assistance with my Lionel 6-31960 Polar Express smoke unit leaking from underneat. Why is this happening?

I know that I was not impressed with the amount of smoke it was making. What do I need to do to increase smoke?

[wrmcclellan]

CN - I just happen to have one of these locos on my bench for some repairs. So I took the boiler off and took a close look.

The smoke units are pretty simple, but the assembly is a completely vertical assembly.

On top is a 2 piece zinc casting/chamber for the heating resistor and fiberglass wicking. The chamber is swaged to the steel mounting bracket. Screwed to the bottom of the mounting bracket is a plastic receiver/tube for the piston.

The plastic piston (which has a flapper valve to allow air in on the downstroke and closes for the upstroke to push air out the stack) which moves up and down inside the smoke unit assembly is actuated by a lever and cam from the front driver axle.

The lower zinc casting has two holes on the bottom for the air to enter from the piston upstroke.

If one separates the zinc castings (requires unsoldering the common wire from the resistor to the mounting bracket) on top one will see that where the two air inlet holes on the lower casting protrude about 1/8" up from the casting bottom. This creates a "small" reservoir for excess fluid not absorbed by the wicking.

If you overfill the smoke unit, fluid will simply run out the holes in the bottom of the lower casting, all over the piston, and out the bottom of the loco. I suspect this is the case in your situation since you imply the unit is "working" so to speak.

Note that over saturation of the wicking will result in low (to no) smoke production since this is a "conventional" loco and track voltage (and thus the smoke resistor) will be low or the loco speeds off the track. To get the smoke resistor hot requires running at ramming/launching speed for some period of time. There is no regulator in this level of loco to place a constant voltage to the smoke resistor.

These are not great smokers, but the smoke unit itself is a very reliable unit unlike some other locos that use a high heat plastic chamber that eventually distorts or melts if one does not keep smoke fluid in it or keep the smoke unit off.

The good news is most smoke fluids are versions of mineral oil that evaporates a bit and does not hurt the finish of the loco or its mechanisms (barring a dusty environment).

Short of disassembling it to dry it out, you can let it dry out naturally - could take a while - or you could run it on a bench at a higher voltage with the driving wheels up to heat up the resistor and evaporate some of the fluid.

Good luck!

[lionelsoni]

Should you want to increase the smoke-unit voltage in normal operation, a way to do it is to put a voltage-dropping element in series with the motor.  Then you will have to use a higher track voltage to keep up the speed that you want.  The higher track voltage will be the voltage that the smoke unit sees.

A suitable voltage-dropping element is a series string of diode pairs, each pair wired in anti-parallel, that is, cathode to anode.  This will drop the motor voltage by about one-half volt per pair.  Another, equivalent, way to do it is with bridge-rectifier modules.  Connect the + and - terminals of each module together, then wire the modules in series with the motor using their ~ terminals.  Each module will give you about a one-volt drop.

[CanadianCN]

I want to thank you for the responses. So how much fluid should be put in so this does not spill over?

Can the smoke unit be upgraded to a fan type?

Love the smoke.

[wrmcclellan]

CN - you are most welcome.

With dry wicking, the smoke unit can take no more than 20 drops. Otherwise I would avoid any more than 10 since it is soaked and you get it smoking again without the drainage. Run it until the smoke output is greatly dimished to ensure the wicking is ready for a reload. It is not a large reservoir and the fiberglass bat occupies over half the space. The best smoke occurs when you keep it relatively light. The heating resistor nests in the wicking. If too wet it overly cools the resistor. If you run it dry the wicking will char (dimishing smoke fluid contact with the resistor) and/or you may cook/destroy the heating resistor. The replacement smoke unit/chamber/lower piston sleeve/headlight/mounting bracket assembly is Lionel PN 620-8635-200 (Currently $19).

I did some checking around on line and found quite a few comments that older PE locos used a 30 or 33 ohm resistor in the smoke unit. The Lionel PN I gave above is an 18 ohm unit. The newer part will smoke better as it will get hotter at lower voltages.

Converting to a fan unit would be quite a fabrication project. Even the newer Lionchief remote controlled PE locos use the same mechanical smoke assembly, so no easy drop in of a ready-made fan driven unit.

I added an MTH fan unit that I picked up from MTH parts at a York meet into a small Right-of-Way 0-4-0 tank loco that I also added Electric RR TMCC control too. The same unit might fit in the Baby Berk. The unit I used was one of the early MTH units from their PS1 locos where one can run track voltage directly to the smoke unit. Later units (both Lionel and MTH) run off lower DC regulated voltage from the DCS or TMCC/Legacy control boards.

To make the smoke 'puff' requires an electrical or mechanical scheme to interrupt the power to the smoke element/resistor (The ERR TMCC boards provided this electronically). As the loco presently has an eccentric on the front axle that moves the push rod and lever for the present smoke unit I would start there with a magnetic reed switch or lever microswitch.

My tank loco project took quite some time and this would be similar. Unfortunately I do not have the MTH PN of the unit I used (and many are still available - typ around $50). You can also find them on EBay. MTH made dozens of different mechanical configurations so picking one is a project in itself. 

Electric RR

http://www.3rdrail.com/err-3rdrail/

Royz Trains sells ERR products and a smoke unit that might work.

https://royztrains.com/product/blower-smoke-unit/

It appears the Royz smoke unit can work from track voltage and not require TMCC upgrade. It seems possible to operate it with a magnetic reed switch or lever microswitch to interrupt the voltage to the unit using the existing cam/pushrod/lever(modified to make room for the smoke unit). 

Unfortunately there is no promise this will all fit. Good luck!