I have a couple of excellent track cleaning cars which I use once or twice a year to remove dirt accumulation from the rails of my model railroad. The use of graphite or NO-OX-ID on the rails allows for such long intervals between cleanings. See my blog posts of September 11, 2020 and August 21, 2021 which outline these methods.
Track cleaning cars only clean the rails. They do nothing to remove the light layer of household dust that falls on the entire layout. Ideally, a vacuum cleaner should be used from time to time. However, this is one of those jobs that is quite prone to procrastination, at least for me.
I am aware of a couple of commercially built HO scale cars that contain small vacuum cleaners. However, I thought I would tackle making my own. Here is a picture of the final result:
This is how I built this car:
- I began with a Roundhouse Hobbies high-cube boxcar. As with most such cars, the floor of the car complete with both trucks and couplers is easily detached from the car body. I removed the steel weight that was fastened to the floor of the car with two plastic pins and double-sided tape. The components that will be added to the car will provide sufficient weight to allow the car to track well.
- Using my 3D printer I created an oval-shaped insert that will serve as the vacuum nozzle on the underside of the car. The interior is slightly cone-shaped to create a venturi effect to the flow of air sucked in to the car. Here is a graphical depiction of this, showing the nozzle from two perspectives:
- I carefully cut a hole in the underside of the car slightly to one side of the mid-point of the car to fit the nozzle.
- I next cut the bristles off an inexpensive synthetic paintbrush and carefully glued a thin wall of bristles around the outside perimeter of the nozzle using Gem-Tak adhesive (available from Michaels and Amazon):Once the adhesive set I trimmed the bristles so they reached about halfway between the railheads and the tops of the ties using a sharp pair of small scissors. I cut away slightly more bristle material where the bristles rub on the rails. Later, when the car was complete and much heavier because of the various components inside, the bristles can be "fine tuned" to eliminate derailments that arise if they are too long. I had to remove the first set of bristles and apply new ones because I was too aggressive at cutting away the first set of bristles. The purpose of the bristles is to help stir up some of the dust but, more importantly, to help ensure that the vacuum force is as strong as possible at the top of the ties and ballast.
- I needed to create the means by which electrical energy could pass from the rails, through the metal wheels (insulated on one end of each axle), through the axle and into the car itself. For this I used the same wiper system I explained in my blog entry of December 21, 2020 titled Flicker-free Car Lighting.
- I had two 12 VDC brushless fans in my parts bin that I have owned for years. I don't recall where I obtained these from but they appear to be cooling fans from some sort of electronic device. I likely purchased these from either Princess Auto or B&E Electronics. I carefully cut an opening in the top of the car to accommodate the fans, as follows:
- I next installed a small sliding on/off switch through the underside of the car bottom.
- I next built the circuit which will power the fans with slightly more than 12 VDC. The circuit consists of a bridge rectifier (minimum 1 amp), five 3-volt 1-farad supercapacitors wired in series and a 5-ohm resistor. Note that the sum of the voltage ratings of the capacitors must be more than the maximum voltage that they will be subjected to [5 X 3 volts = 15 volts; there is more than enough margin between 12 volts and 15 volts; if the sum of the voltages is exceeded the capacitors will "pop" (i.e., in a mini explosion)]. These components are available from DigiKey or Mouser. The resistor is placed in the circuit to slow the in-rush current as the supercapacitors are charged (a high in-rush current can be interpreted as a short circuit by the Digital Command Control ("DCC") system). The circuit diagram is as follows:
- I next 3D printed the container shown in the following photo. It is mounted over the top of the vacuum intake nozzle. At one end the container is a space into which a fairly thin piece of filter material can be inserted (this is the roll-type filter material that can be purchased from many hardware stores). The container is mounted onto styrene so the underside of the container fits snugly. A piece of styrene is positioned at one end as a retainer for the container and a styrene swivel is positioned at the other end to hold it firmly in place. When the top of the car is mounted in place the fans blowing out from the car create a negative pressure inside the car. This causes air to flow upward through the intake nozzle and out of the container through the filter material. The filter material traps the dust in the container.
- Finally, the male side of a two-conductor connector was mounted to the car floor using hot glue. The female side of the connector was mounted to the inside of the car top. When the car top is lowered into position the connectors mate, completing the circuit to the fans. See the arrow pointing to the connector in the diagram below. This connector is one of many different connectors I have collected over the years; I don't recall the source. However, connectors are easy to come by.
- Finally, I used my 3D printer to print a grille to cover the fan outlets as well as to cover the tops of the fans.
It gathers a surprising amount of dust. It is not powerful enough to pick up heavier objects such as loose ballast. The fans make a low whine when they are running but it is not bothersome. I simply include the vacuum car in a train occasionally to take care of dust along the rails. If there is any interruption in the power to the car, such as over a turnout, the supercapacitors keep the fans running at top speed. If the car is removed from the rails while operating the fans will run for about 15 seconds before the supercapacitors are fully discharged.