Hi this magazine has an article about making cleaning cars http://model-railroad-hobbyist.com/mrh2009-Q3/track_cleaning_car and I have seen a masonite car made that works. You could also do a search on this forum. Also some of the trainboard advertisers probably sell a cleaning car as well.
The only track cleaning car I use are two masonite slider cars I made. I was able to get a piece of 1/8" masonite. I run one in every train, usually right behind the loco. They work very good.
I made one using a loco that I took the motor out of. I built a tank from brass with 2 openings up top and one below. The bottom uses a pad witha piece of cloth wrapped around it with an oring. Fill the tank with 91% alcohol and it will drip on to the pad. Push it around the layout with powered locos and it cleans track and loco wheels. When the cloth becomes dirty simply replace it. Jeff
What type of car are you thinking of? A tanker, a rolling scrubber, a polisher or a rail grinder? The masonite polisher has been mentioned and it is the easiest to build. Are you good with working with metals? Some of the best designs are base on machining skills or access to solid chunks of brass or steel.
These magazine links are always a disappointment because it always assumes that everybody has a subscription which I don't . Check out this Atlas topic. http://forum.atlasrr.com/forum/topic.asp?TOPIC_ID=67055
You don't need a subscription to buy a back issue or an article reprint. With a couple of the magazines now on CD or DVD format you can get large blocks of back issues and they will hardly take up any space.
The price is quite good for Model Railroad Hobbyist - it's free as are all of the back issues. You can read most back issues on line, but the oldest ones can only be downloaded as a .PDF file.
thank you for all the feedback! i liked the masonite board idea and have built the car already. it works awesome. and yes this forum is for sharing knowledge. many of us enjoy building things on our own. because its our own. money does not buy that satisfaction.
Thanks to John Allen! I built this using an old woodside that never looked right. its a masonite board attached to a pice of oak and inserted into the car. It is used on a repair and service loco. I run it about once a week and it keeps the track operational. Cheap! Just a little effort and imagination. Thanks for all the input.