Cabin Heat Bowden Cable Puts Up A Fight

As mentioned briefly in the previous post, the Bowden cable for the cabin heat control was installed in the instrument panel, routed through the grommet in the firewall and around the right side of the Rotax 912 engine along the engine mounts per the plans.  The cable is supported off the engine mounts by utilizing pairs of Adel clamps at three locations. One of the Adel clamps is placed on the engine mount tubing and the other around the Bowden cable then the two clamps are bolted together. Sounds easy enough right? The first pair of Adel clamps on the upper right engine mount tube gave me quite a fight. There was just no room to compress the ears of the Adel clamps while trying to slip a bolt through the clamps yet alone start a nut. The main issue is the coolant hose and #3 cylinder’s exhaust pipe prevent a hand from getting onto the clamps, so only fingers can reach the clamps. I after fighting and fighting it became apparent, I could not do this task by myself so called Bernie for help.

The two Adel clamps and the cabin heat Bowden cable are hidden behind the #3 cylinders exhaust pipe. Between the exhaust pipe and the three black coolant hoses blocking hand access, it was very difficult to install the clamps at this location.


Friday, Bernie assisted with installing the Adel clamps in the tight spot. One idea that I came up with that ultimately worked was to make a loop out of safety wire that Bernie could place around the ears on the Adel clamps and pull the wire to compress the clamps while the bolt was inserted. I was using a nut driver reaching in from above along the backside of the engine and finally got the nut to thread onto the bolt. Sounds easy, but working out the details and finally getting the parts onto the airplane took at least an hour of trial and error.

Well buried, the two Adel clamps on the upper right engine mount tubing put up quite a fight … but with Bernie’s help we knocked it out in the 12^th round.


Bernie and I finished routing the cabin heat Bowden cable under the engine where an additional two pairs of Adel clamps are used to suspend the cable from the lower engine mount tubes as the Bowden cable traverses the bottom of the engine on its way to the cooler door. The two pairs of lower Adel clamps were a piece of cake to install compared to the upper clamps. Thanks for the assistance Bernie.

Two pairs of Adel clamps are used to suspend the Bowden cable for the cabin heat as the cable traverses the bottom of the engine on its way to the cooler door.


A suggestion to fellow builders: Consider installing the Bowden cable for the cabin heat prior to installing the exhaust system or cooling system. The Bowden cable can be installed without any difficulties … but would suggest leaving the bolts threaded onto the nuts, but not tightened down so the clamps can be moved or the cable positioned for best fit as necessary after the exhaust and coolant hoses are installed.


I could not quite finish up the task of connecting the Bowden cable to the cooler door because I forgot to prime and paint “the comb” that is installed on the Bowden cable between the two pairs of Adel clamps under the engine in the above photo. The comb in the following photo is used to add friction to the cable by weaving the cable through the fingers. The added friction is desired to combat the forces of air pressure on the cooler door creating unwanted movement.

Painted “comb” for the cabin heat Bowden cable. Weaving the cabin heat Bowen cable through the slots in “the comb” will add friction … this will combat the forces of air pressure on the cooler door.