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Carl Bells RV7A N947CB
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Date: 3-12-2008
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Number of Hours: 5.00
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Manual Reference: None
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Brief Description: Hand brakes
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I found out that the hand Rotax hand brakes I installed will not allow me to put them in series with the toe brakes and I really want to have both. Although I can fly with toe brakes only, I just feel better having hand brakes for back up and realty hard braking. This is just a concession I need to make for safety because of my prosthetic leg. So this means going to another alternative, but what? Crappppppppp!!!!!!!!!!!!! On to plan “B”.
I called Matco Engineering the maker of the toe brakes and talked with George, their design engineer. I told him my issue and he said I can put another set of Matco master cylinders in series with the others, but may have to use a vacuum process to bleed the system. George was a great help and the Matco folks offered great service and guidance. I bought two more Matco master cylinders from Aircraft Spruce with clevis ends and started designing a new hand brake. It is similar to the Rotex, in fact I cannibalized the knobs off the Rotax unit. The difference is the mechanical advantage is higher on my unit. I reviewed the design information from Matco and decided the master cylinders required more then the Rotax and added the appropriate mechanical leverage. The handles are about 1” longer then the Rotax and the leverage point is ½” higher. I made the unit from 2024 angle and bar, and rather then boring you with the details on how, there are pictures below. It took over 5 hours of cutting, sanding, buffing and turning, but the results are good and the unit works smoothly. I would have preferred rod ends on the master cylinders, but the weight and length would have become a problem, so I stayed with the clevis ends supplied by Matco. I will spend some time tomorrow to re-evaluate the location placement and brake line run.
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Matco with the clevis end
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Spacer busings
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Assembled unit with Rotax knobs
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