Well we got it all set up. Tried to start it and fuel poured
out of all four injectors. Injectors full on all of the time.
No spark. Flooded the engine. 37 pin D submin connector wired
backwards. Way too easy to do. I got on Tracy case years ago
about
this connector. More about that soon. Hopefully we did not
fry Tracy's computer. Will know more about that on Sunday
night when Tracy gets back from a flyin.
BTW if you are building a slide throttle seal it well
around the bottom. You want the fuel to flow into
the engine and not out between the plates. I'll
makes some changes in the drawings to make this easier.
Does anybody know of a good fuel sealant to use between
the plates of the slide throttle?
Paul Lamar
I have been using the polyurethane glue used to install
windshields for
years to seal fuel tanks. can be found at paint shops or auto glass
shops. Very inert to both auto and av gas.
But watch the temperature. It is not a high temp resistant product.
smale@ncinternet.net
Paul,
A tragic accident happened to one of our BD-5 builders because he
used an incorrect material to seal his fuel system. The material was
partially dissolved by the fuel and blocked the fuel lines causing
the engine to fail. Here are three references to what is commonly
referred to as "Pro-Seal" . It is designed to be used where fuel is
present. It may NOT be the answer in this case if high temperature is
a factor. The point I'm trying to stress is, make sure what you use
will work for your application and not endanger you in the process.
These reference addresses are from Acft Spruce but many other vendors
sell this and similar products.
Regards,
John Lewis
N501BD
Pro-Seal Type Tank Sealants
Pro-Seal and similar products are two-part polysulfide integral fuel
tank and fuselage sealants. They have exceptional strength and jet
fuel resistance as well as excellent resistance to oils, solvents,
all fuels, and weathering. We offer a Pro-Seal equivalent which is a
B-2 type material and meets...
http://www.aircraftspruce.com/catalog/appages/prosealant.php
Pro Seal Type Tank Sealant
Kit A (2.5 Oz.) cartridge -2oz. sealant P/N 09-38500 [PRICE 09-38500]
[BUY 09-38500] Kit B (6 Oz.) cartridge - 3.5 oz. sealant P/N 09-38510
[PRICE 09-38510] [BUY 09-38510] Pro-Seal and similar products are
two-part polysulfide integr...
http://www.aircraftspruce.com/catalog/cspages/prosealtypetanksealant.php
Fuel Tank Sealants
http://www.aircraftspruce.com/menus/cs/fueltanksealants.html
Thanks John.
We need a heat shield anyway so I will have one of these welded up on
Monday.
The tray will catch the raw fuel in the event of another flooded engine.
Perhaps good old JB Weld is the way to go for sealing the slide
throttle. It is epoxy so it should stand up to gas fairly well and
it will take the temperature. The bolts will probably then become
redundant.
Paul Lamar
Hi Paul, As I read it you are looking to seal for the throttle slide
from leakage of fuel. As your injectors are upstream it needs to handle
fuel.
Regards Don
True Don.
Paul Lamar
Paul this is only an idea. Silicon sealant is not what they say
as it has no adhesive properties. In fact the reverse. For your test run
a thin seal may do the job. A spay of silicon on the slide first then
apply the sealant may be the answer .Long term needs more thought.,
Regards Don
Paul
I am trying to work on a solution for your slide throttle situation. It
appears that the fuel is wicking up between the plates due to capillary
action. If that is the case the it could also seep out the sides where the
linkage is connected as well as the top right? In that case you would need
two seals on each side of the Teflon plate around the outer perimeter of the
P ports on the inner side and the manifold pipe on the outer side. The seal
would have to be U shaped in profile and if memory serves me correctly these
seals are used on rotary disc valves. Still need some silicon grease to make
things move easier as well.
I'm sure you know well that circular shafts are easy to seal. The following
idea won't help in the short term but a form of rotary valve might be the
answer.
For ease of discussion imagine two discs with their centers offset above the
ports. The discs have a throttle dia. hole located out near their
circumference and their rotating action is controlled by turning the shafts.
You need one for each P port and they are linked together. To save space
the discs actually would be more like a wedge shape. Lets call them paddles.
With a little imagination you can see that the total outer case could easily
be sealed and the whole unit a bit smaller then what you now have. The
paddles would be made of metal and Teflon inserts (T -shape in profile)
would be placed in P port and manifold side faces. This approach minimizes
Teflon to the frictionally contact area only and makes manufacturing simpler
and less expensive. The case that contains the paddles is sealed with a
flat gasket and is screwed together. The case will retain any excess fuel
and the shafts centers are above the P Ports. The circular shafts can have
and O-ring as well to seal off any chance of escaping fumes.
Doug in Japan.
Can you make a drawing? I am having trouble visualizing
this.
I don't think it is wicking Doug. It would not get past the lowest
point of the intake runners. All four injectors were full on.
They were pouring fuel into those intake runners. They are 50 pounds
an hour each injector or 8 gallons and hour each or a total of 33
gallons an hour!!!! 1/2 gallon a minute!!!!
Not something that happens everyday unless there is a major problem
with the electronics. Under normal starting conditions the intake
is under high vacuum and any fuel in the slide spaces would be drawn
into the intake port along with some air that leaks in around
the slide. There is lots of clearance around that Teflon slide.
I will move the throttle attachment slot up and dam off the
aft end of the slide with a drain pipe. The heat shield/tray
will catch any additional fuel that leaks by the sealed
slide throttle. I am now leaning towards straight epoxy
to seal it as it works well for fuel tanks.
BTW Teflon is cheap. There is only $10 worth in each slide throttle.
Paul Lamar
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