Improving the New AF Northern Smoke Unit
Silencing the squeak and making more smoke.
Click on images for larger view
|The Northern's smoker as shipped has
some design issues that can be modified to improve the smoke
output and silence the annoying squeaking.
This is the chassis as is comes from the factory
|To access the smoke unit, the Electronics
need to be temporarily moved out of the way by removing the mounting screws
and cutting the tie wraps.
Since the Northern has Railsounds a mechanical chuff generator is redundant but it still needs the air flow for proper smoke generation and modulation.
|Be prepared to make some new baffle
plates from some tin can stock. They are not hard to make.
To remove the baffle you need to remove the six screws holding the smoke unit top.
After the top is off the baffle needs to be removed but it is swedged in place so tight that removing it will destroy the original baffle . Use a strong channel lock or needle nose pliers to twist out the baffle like a sardine can lid.
|I used metal that was slightly thinner
than the original so the baffles are easy to slide in place.
You see the replacement baffle I selected was one that totally silenced the unit. It has a 3/16x1/4" eyelet inserted in the hole. Note that it has an air gap on both sides of the baffle.
The design needs an air gap on the inlet side of
the baffle to allow fresh air into the piston chamber in the reverse
|I noticed that the piston by itself
also had a slight squeak but found that it was easily silenced too.
To remove the piston chamber first remove the piston rod and piston by removing the hex screw in the drive gear.
|A jewelers screwdriver is used to remove the two Phillips screws that hold the piston chamber to the smoke unit.|
|The air hole on the inside of the cylinder needs to be chamfered to eliminate the sharp edges|
|The outside of the air hole also need a slight chamfer added to it.|
This chassis has a 27 ohm element and the regulator board has been removed so the element gets the full track voltage. You can see it smokes adequately running at 9 volts and above.
This element also works for TMCC conversions when the TMCC boards provide the smoke voltage.
Now we will address the smoke element.
Looking at previous Lionel smoke unit designs and comparing the applied wattage to the elements, it is obvious that the Northern's element is too cold to make smoke properly. The Northern's smoke regulator board only provides 2-4 volts to a 18 ohm element which is only .9 watts at the hottest voltage.
Assuming an average track voltage of 9 volts at running speed, the 27 ohm element used in many of their other units has 3 watts of element heating.
I suggest not using using the existing regulator and original element.
regulator board and use a 27 ohm element.