VL Big Boy Smoke Unit Stopped Working

one thing I noticed is not enough smoke fluid, which caused the wicking to burn.

bigdodgetrain posted:

one thing I noticed is not enough smoke fluid, which caused the wicking to burn.

Thanks BDG, I have fallen into my nemesis - that being starving the units.   Smoke was bellowing out of both stacks before the front one stopped; so, now I am thinking that volume of smoke is not the only indicator; time is the other factor.  After 10 minutes of running, I should have added more fluid.  BUT the gotcha is if you add too much, you mess up the fans and any other circuit boards around.

Have been searching for topics on the forum regarding what I called the thyristor - don't know if that is the right name for the component next to the heating element.  A spec was mentioned in the forum for how close it had to be to the heating element.  I think I saw somewhere where Jon (retired) of Lionel mentioned it.

The thermistor should be vertical off the board parallel to the smoke unit.  That seems to produce good results for my VL-BB.  When I had very poor blowdown smoke, I checked that smoke unit and the whistle smoke unit.  The whistle had it parallel with the smoke resistor, the blowdown had it leaning in right next to the resistor.  I adjusted it to be like the whistle, problem solved.

Thanks GRJ, as a first step to find out why the smoke unit has failed, is there a way that I can test the fans when they are still connected to the board?

You need to disconnect the fans from ANY electronics, then you can try powering them with a 1.5v battery.  Any smoke fan that's good should spin on 1.5 volts.  I believe the smoke motors for the VL-BB don't have plugs, so that complicates it a bit, you have to take the leads off the motor, note where the red one goes before you do.

Another question, when putting new Lionel wick 691SMKP008 in each compartment, how many ropes after shredding per compartment?

gunrunnerjohn posted:

You need to disconnect the fans from ANY electronics, then you can try powering them with a 1.5v battery.  Any smoke fan that's good should spin on 1.5 volts.  I believe the smoke motors for the VL-BB don't have plugs, so that complicates it a bit, you have to take the leads off the motor, note where the red one goes before you do.

Thanks GRJ, per the pictures below, do I still have to disconnect the leads:

If you have it out like this, you still have to disconnect one lead to make sure you don't cook the circuit that normally runs the fan motors.  As long as the PCB is totally isolated otherwise, you can leave one lead on the PCB.

There has got to be a reason for Lionel wick premature burning other than not enough fluid. Looking at the pictures posted I think we can see the reason. Looking at the smoke unit housing the cut out for air flow would make me think that the impeller needs to spin CCW to allow more air passing through the cutout over the resistor. Too me, looking at the impeller the way it’s mounted, it would need CW rotation for air to be pushed away from the impeller allowing maximum air flow. If I’m correct on the CW rotation the air would hit the casting in the opposite direction needed and not allowing the air to fully excape in to the resistor area causing overheating. 

RickM46 posted:

Another question, when putting new Lionel wick 691SMKP008 in each compartment, how many ropes after shredding per compartment?

Any ideas?

One rope per compartment should do it.

Just found some comments in my Lionel notes by Jon Zahornacky regarding the placement of the thermistor to the heating resistor; found them somewhere in the forum (have been looking for them again for hours but no luck) and put the comments in my notes:

Jon Zahornacky, aka SanaFeFan (smoke unit engineer for Lionel, retired) said that the smoke units were engineered for the factory block of wick to work with the heat resistor, a thermistor located 1.6mm from the heating resistor and with the wick block a certain distance and density to the heating resistor.  You cannot buy the factory block of wick.  So, it is critical that you locate the replacement wick and its density and thickness and depth as close as possible to the original factory block and not block the fan air holes.

1.6mm converts to 0.0629921 inches which converts to 1.009/16ths.

Correction to the description to Jon's career: Jon was more than a smoke unit engineer; he was a great engineer and inventor and held many patents for his work; happy retirement Jon!!

RickM46 posted:

RickM46 posted:

Another question, when putting new Lionel wick 691SMKP008 in each compartment, how many ropes after shredding per compartment?

Any ideas?

Thanks Rod!!  Am waiting for comments on your fan rotation above.

romiller49 posted:

There has got to be a reason for Lionel wick premature burning other than not enough fluid. Looking at the pictures posted I think we can see the reason. Looking at the smoke unit housing the cut out for air flow would make me think that the impeller needs to spin CCW to allow more air passing through the cutout over the resistor. Too me, looking at the impeller the way it’s mounted, it would need CW rotation for air to be pushed away from the impeller allowing maximum air flow. If I’m correct on the CW rotation the air would hit the casting in the opposite direction needed and not allowing the air to fully excape in to the resistor area causing overheating. 

I see the point you are making and I noticed the same thing in another VL engine, the Baldwin Centipede, which has four single smoke units. In those units, however, the fan motor was wired so that the impeller would spin CCW so as to propel air directly into the cut out leading to the resistor.

However, I'm not sure that this would account for the sort of heat damage caused here, which is not minor. Also it would be a design defect, meaning that it would have appeared in other VLBBs and (a) I have not seen any reports of that and (b) it has not happened in mine. Going back to the OP's original post, everything (fan, heater) failed, which might indicate a main board failure.

As this engine was serviced by Mike R. I'd email him to ask what he thinks. I would not discount lack of smoke fluid as a cause of overheating as in my experience these units use up fluid very quickly. Mike R. also referred to this in the instruction video made in connection with the issue of engine, which I took as a kind of warning to keep them topped up.

In the pictures above if the impeller spins CCW the air is being pushed via the concave portion of the impellers. The air needs to be pushed via the convex portion of the impeller. I checked this against an MTH unit and they engineered the air to be pushed via the convex portion. There is no way to get this with the Lionel unit as is. You may try pulling the impeller out and turning it over so as to push air on the convex side of the impeller. I’m not trying to discredit the Lionel engineer that designed his smoke unit but I think it is a flaw. 

Gentlemen, thanks for all the help on the smoke unit.  I am now thinking about what components I can check to determine which one is at fault.  I can test the fans but would like any advice on how to check the resistors and thermistors.

The Smoke Elements should read about 8 ohms.  You can measure them right on the PCB since you have it disconnected from the loco.  The fans should spin at 1.5v.  They can take up to about 6v without damage.  I usually put ~3v using a couple of AA cells to check them out.

The damage to the smoke funnel looks like things got very hot.  The batting looks charred, but in reality it is not charred, it is the fluid that burned and produced the burnt residue on the batting.  This is a common misconception that the batting burns, the matted batting in this loco does not burn or char.  It is the burning of the fluid (it is a lamp oil) that produces the residue.  Using the newer "string like" batting does melt however, and the reason it smokes more is the temperature is hotter with the less dense material.

Having designed the electronics system in this loco, I believe the reason your loco failed is the thermistor could not sense the temperature created by the element due to the residue.  The temperature path for the element to the thermistor is through the fluid dampened batting.  When the batting is not saturated, the temperature rises on the element, but the air between the thermistor and the element is a poor conductor of the heat, relative to a saturated batting material. Low fluid level will cause this condition to happen, and then the element will overheat.  The smoke unit can handle this for the most part, but repeated power cycles with low fluid levels will cause the damage you have.  Again, I am guessing a bit here, it may be you just have a failed RCMC smoke circuit...

You may have damaged the RCMC, but the only way to know is to repack the smoke unit and try it.   If the element is ~8 ohms, then you should not get a 4 blink.  It is possible the thermistor failed, it should read about 50k ohms cold, you can measure it with a meter as well.  If the thermistor fails, you will also get a blink code.

I also suggest Lionel premium smoke fluid, as it is non-conductive.  Unless you get the RCMC fully saturated with Lionel premium fluid, RCMC should not be damaged.   Just wipe it off best you can.

Hope you get your loco back running!

Jon,

Thanks as always for your detailed explanation and insights.  Is the original "block" style batting material available anywhere for purchase?  I think Lionel no longer sells it and switched over to the angel-hair or I believe you referred to it as "string-like" batting.  Thanks.  

Glad retirement hasn't taken you off the Forum, but do hope you're enjoying it (and your trains).   

Dave