Hittade denna beskrivning på en lösning:
"I have a hump yard on my layout, after alot of trial and error I have one that works on gravity without air assist. I have a kadee uncoupler just past the apex on the top of the hill to release the cars down the hill and 2/3 of the way down I have strips of styene inside of the rails with mole skin on them so that the car's wheels rub against them to slow down the cars. I have this set on an electric motor that opens and closes the strips against the cars to control the speed I use a momentary switch to operate the motor. I found this works very well and with a little practice is easy to use without all the plumbing needed to run air to retard the speed of the cars. Granted my hump yard is only 7 tracks but this system works very well. I use a 2 1/2% grade for the cars to roll down from the apex, also make sure that your cars have at least 3 oz of weight in them so that they can get a good run downhill without stalling on the track. Remember to use the moleskin as this helps with to keep from rubbing all of the weathering off the wheels when the retarders engage the wheels."
Läste om en annan lösning, där man använde luft som blåstes mot vagnarna. Tiden som luften blåstes var styrd med en timmer, så att lättrullande vagnar träffades av luften under längre tid medans de trögrullande inte fick någon luft alls på sig. Låter som ett sätt som borde kunna fungera.
På ett annat ställe läste jag om en kille som installerat blåsning "mellan var 3:e slipers" och då i båda riktningar. På det viset så kunde han antingen bromsa eller skjuta på vid behov. (man blåser naturligtvis enbart i en riktning samtidigt).
