My Fokker DVII Project - Page 117

Von Writter · 20 August 2008, 09:45 AM

Quote:

Originally Posted by Jeff Brooks

He says he is interested in the Anemometers when they are done ... Troy, any update?

Thanks for the input Langdon!

Not yet Jeff;
I'm still trying to get a hold of Vet, without sucess I might add! I'll post an update as soon as I know anything. Is Vet gone on vacation or?? Jeff?

ulpilot · 20 August 2008, 03:36 PM

Quote:

Originally Posted by Von Writter

Not yet Jeff;
I'm still trying to get a hold of Vet, without sucess I might add! I'll post an update as soon as I know anything. Is Vet gone on vacation or?? Jeff?

I'm here, just super busy with a bunch of new projects and idea's. Not near the phone much anymore, as Jeff knows!

Vet

Jeff Brooks · 2 September 2008, 07:40 AM

Hi all,
I have been jumping back and forth from one part to another. I have finished with three sets of ribs for the lower wings, just putting the doubler ribs together. While at work, I have been figuring out the fuel system, and putting the plumbing on the instrument board. Here is a diagram of the fuel system setup I finally settled on.

I chose this set up as it very close to the original setup.

Here are a series of slides showing how I will use the valves during various operations.

The first one is with all the fuel valves closed.

The next is to test the operation of the electric fuel pump.

j ferguson · 2 September 2008, 07:47 AM

Jeff,

Are you sure the return from the carb should go to the pressure side of the pump and not back to a tank?

Jeff Brooks · 2 September 2008, 07:57 AM

After testing the fuel pressure generated from the electric fuel pump, it may be necessary to relieve the pressure in the line to get a good reading for the next operation. So selecting the fuel pressure reading from the carburetor clears the pressure in the line to the gauge, and prepares for the next step.

Routing the fuel from the electric pump through the mechanical pump primes the mechanical pump before the engine starts. You can be sure the fuel has gone through the pump when there is an increase in fuel pressure on the gauge. I am told that sometime the mechanical pump looses it's prime and does not funtion correctly when the engine is running. The pump also uses fuel to lubricate it, and if it loses it's prime, it will burn itself up.

After the mechanical pump has been primed, the fuel can be routed directly to the carb for starting the engine. Also note, that if the fuel pressure at this phase is significantly lower than when checking the fuel pump pressure directly from the pump (see page 2), it may ba a good indication that there is a potential leak in the system. This is good to know before you start!!!

Once the engine is started, both the mechanical and electrical pumps will be running parallel, providing redundancy.

Jeff Brooks · 2 September 2008, 07:59 AM

next is checking the operation of the mechanical pump. this is accomplished by turning the valve that routes the fuel of the electrical pump off. you can measure the fuel pressure that the mechanical pump is developing.

and last, the use of the reserve tank.

Jeff Brooks · 2 September 2008, 08:01 AM

Quote:

Originally Posted by j ferguson

Jeff,

Are you sure the return from the carb should go to the pressure side of the pump and not back to a tank?

There is a one way check valve to stop the pressure from going to the pressure side of the pump.

I initially had a pressure relief valve just before the carb, routed to go back to the main tank. But I have read the both the electric pump and the mechanical pump have pressure relief built into them, so it doesn't appear that I need it. The Allison Carb requires only 4 to 7 psi.

Von Writter · 2 September 2008, 08:12 AM

Looks good Jeff, the plumbing should be fun

RobW · 2 September 2008, 08:18 AM

Jeff,
I'm wondering about that reserve tank... does it have a real utility for you? It seems to me to add uneccessary complexity to your fuel system, plus, assuming that the aircraft only gets used a limited number of hours a year, I can foresee issues with old fuel, or contaminated fuel. I understand you wanting to do a fair representation of the original... and perhaps you'll have standard proceedures that ensure that reserve fuel is burned off regularly, but this one has me a little concerned.

You've thought through all the other stuff on this plane quite well, so I'm sure that you've already considered this and worked it out and I'm missing something obvious.

Rob,

Hey, we'd love to hear more of your project at our project forum during our WWI fly in event.

Jeff Brooks · 2 September 2008, 09:19 AM

I have thought about the reserve tank for a while. Although the reserve is small in capacity, it does serve many purposes which justify the need for it.

1) A reserve tank was on the original, which I am trying to preserve as much of the original design as I can.

2) The obvious one - switching to the reserve when the main fuel is low.

3) This last reason came to me from one of the emergency procedures on the Blackhawk helicopter. When a fuel filter is clogged in flight, it can quickly and easily be remedied by switching to another tank until a forced landing area can be found. To me, this last reason outweighs the threat of leaking plumbing!