To keep the tension on the break cables for the drumbreaks on the velomobiel correct a set screw is available. However in my velo they tend to get loose and the tension on the break cables gets less and less overtime. Even a 100Km bike-ride could already do the 'damage'. To prevent the bolts rattling loose I used to add some glue or some sticky stuff to keep them fixed. However if you need to replace your break cables you need to remove all the gunk. You don't want to damage the threat. To solve the loosen up I printed some very simple distance blocks. I printed 15 blocks each 1mm bigger then next so I can pick the one that I need for the moment. If over time the cable lengthens you just take a different distance block.