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Date:  2-27-2008
Number of Hours:  6.00
Manual Reference:  6W7B
Brief Description:  Build wing fuel pump mounting channel

A failed do it yourself design/fabrication project.

Because I plan to burn mogas in my plane as often as possible, I want to mount the auxilliary fuel pump(s) in the wing, right next to the fuel tank. That way, I hope to reduce the possibility for vapor lock to occur in the fuel system. This project was inspired by the info posted by builder Joe Motis on the CH601.org website. See Fig. 1. Note that the nose ribs has changed since Motis built his 601. On Motis' wing there are 4 nose ribs inboard of the fuel tank. On mine, there are only 3. On my 601, there is a 160-mm space between ribs 2 & 3, and a much smaller space between ribs 1 & 2. In Motis' plane the pump installed between 2 & 3, one rib away from the tank; in my plane it must be installed in the space adjacent to the tank.

My design goals were:

- Pump and fuel lines easy to remove for maintenance, etc.
- Fuel pump as close as possible to the level of the bottom of the fuel tank.
- Pump should not interfer with removal of the finger screen from the fuel tank

I designed a bracket that would cantilever the pump near the bottom of the nose skin and forward of the location of the tank outlet/finger screen. The unbent blank is shown in Fig. 2. The pump would be bolted to the bottom of the channel. This puts the pump inlet very close to the level of the tank outlet. I planned to rivet two pieces of L-angle to the bottom of the channel to strengthen the assembly. To avoid the flanges on the lightening holes, the support arms of the channel were bent inward in two steps. Fig. 3 shows the channel clamped between the angles for nose ribs 3 & 4 on the right spar.

When I clamped the assembly in place, it was obvious that it was too flimsy. The .025" aluminum just didn't have the stiffness needed to hold the pump. In addition, the two bends in each support arm introduced a degree of freedom that made it easier for the structure to flex.

I must design a new channel.
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Joe Motis Fuel Pump

Joe Motis Fuel Pump

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Blank for mounting channel

Blank for mounting channel

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Channel clamped in place

Channel clamped in place

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