Brake Master Cylinder Installation
Since the brake pedals were installed, i installed the Matco master cylinders. An interesting little thing i learnt when reading about this system was the fact that the cylinders bypass. If you look at how Van's has you plumb the system, the fluid comes from the reservoir to the co-pilot cylinders, then from the output of those cylinders to the pilot cylinders. What happens is that in the last 1/16" of travel (when fully extended) the master cylinders will bypass any fluid pressure - so it's important that there is very little friction in the pedals, so the internal spring can fully extend the cylinders when you release the pedals. If they do not fully extend, there will be no bypass and a co-pilot brake input may not get to the brake callipers.
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| Grease was used where the bolts pass through the master cylinders |
Rudder Pedal Assembly Installation
Before installing the rudder pedals, i had to match drill some bolt holes through the UHMW material which are used to hang the rudder pedal bars. These are match drilled with a template first then taken to the drill press to drill the whole way through. I used a square to make sure the initial drilling was not askew.
The centre blocks are match drilled using the bracket in the fuselage in a similar fashion (instead of using a template), and were then drilled through using the drill press. They are then split in half. The plans state to "use a bandsaw or a hacksaw" and a maximum kerf of 0.063". I figured it was important to keep the kerf thin - so used my Japanese razor saw to do the cut. (More on this later!)
The rudder pedals were then installed by using grease on the end of the bars:
Wobbly Centre Support
When installing the bolts for the side and centre blocks, the plans state not to use normal torque, but only tighten the blocks until the resistance is felt in turning the bolts. For the centre block, the plans called out one NAS1149F0363P washer (an AN3 thick washer) between the 2 halves of the block. So i installed the block using this washer, and tightened the bolts until the resistance in the bolt changed. After doing this, the centre bracket was very wobbly on the rudder bars - like there was no clamping force on the rudder pedal bars at all. So i removed the 363 (thick) washer and replaced it with a 332 (thin washer). But the issue was still the same:
As always, it was Van's Airforce to the rescue.
I posted a query about if this wobble was normal, and someone suggested using a thinner shim, so i made up some shims from the thinnest sheet i had - 0.016". The wobble was still there, but was a lot better.
I believe the issue was that i used the Japanese saw for the cut - this removed so little material that with the use of the washer, or even a 0.016" shim, the blocks were being held too far apart to clamp onto the rudder bars. Van's intent in the instructions to give a maximum kerf was not actually an instruction to keep the cut as small as possible - but to make sure the cut didn't exceed the thickness of an AN3 thick washer. By using the very thin saw, i had inadvertently made the cut thinner than the washer, or even the 0.016" shim, so the blocks could not clamp.
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| I measured my thin Japanese saw and it is only 0.012" thick. |
Someone posted a reply to my VAF post and suggested i try a soda can - so i drank a Bundaberg ginger beer can (#straya), cleaned it up and made it into a pair of shims. This did the trick! The aluminium on this was only 0.0040" thick - so 1/3 the thickness of the Japanese saw. Once installed, i tightened the nuts until the resistance in the bolt increased, and checked again - no wobble in the bracket anymore, and the pedals still swing freely. Success!
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| I used this jig to draw the trim lines, and then to bend the tabs. |
Rudder Cable Links
The last task in Chapter 33 was to separate, deburr, paint and install the rudder cable links. I installed them on the furthest forward most pedal position - these will likely need to be adjusted later on once i get some seats etc!
That completed Chapter 33 (except for leak testing the brake system).
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