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Scary stuff I was wincing in fear!

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Re: Scary stuff I was wincing in fear!

Post  1/2A Nut on Mon Oct 08, 2018 10:00 pm

Dave your fine right here with this, I have been a busy bee for a Monday.
The bottle shape is a good one for the project. Any idea of how much volume
it holds?

If it was me I would use a rubber test tube bung drill two holes through it for
my pickup line and breather line and use a clunk since you have a good length
on the tank. My first bottle tank was done with a cork I shaped it to size a carfuly
drill pilot holes then followed up with a slightly smaller hole with some water on the
metal tubes I wiggled them in place. Set up the pickup and clunk wet the cork and
wiggled it into place. Once dry I saturated the outside of the exposed cork with CA
glue and made sure some was getting on the inside lip of the bottle to help hold the
cork in place. If you have the right size heat shrink while the thick CA is still wet
slip over the heat shrink over the cork and neck of the bottle and with a heat gun
shrink it up fold over the excess over the top of the cork and around the metal tubes
trim the excess heat one more time and press the heat shrink down around the metal
tubes for a flush finish.  Do not drill out the spring post for a rotary pressure feed.
The pressure is too high and not worth the hassle trust me I know I have done it,
fought trying to make it work good / never really did. Throttle is a plus for any plane
if you can throttle the engine you will help it to last longer. You can buy a RC carb
carb body, NV assembly for the engine which would then allow a muffler with a pressure
tap much more stable engine at idle and at full throttle.



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Re: Scary stuff I was wincing in fear!

Post  Surfer_kris on Tue Oct 09, 2018 12:57 pm

I prefer to use all-plastic bottles as one can make very nice, leak-free, feedthroughs with just the fuel line itself for sealing.
Here is how I do mine, after advice on the RCU 1/2A forum when it was more active some +10years ago. You heat up the back end of a regular drill or other suitable wire and welt a hole through the plastic. This gives you extra material around the hole which is also very smooth and will easily seal against the fuel tube. It takes a bit of practice on a separate plastic part in order to find the right under-size drill for the job, but once you get the hang of it, it is very easy. To stop the fuel line from being pulled out by misstake you can insert a solid plastic tube in the fuel line on the inside, this will effectively stop it from being pulled through the under-size hole.

Below is a picture that hopefully shows what the finished feedthrough looks like for the vent line. The feed-line is done in a similar way through the plastic bottle cap.

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Re: Scary stuff I was wincing in fear!

Post  Dave P. on Tue Oct 09, 2018 8:47 pm

Thanks for the info guys.  The bottle is an oil bottle sold for spinning wheels, my wife is into fiber arts. They are advertised as a half oz of oil, but come about three quarters full, so I'm guessing it's about 18cc's full capacity.  The drawing you did is exactly what I had in mind.

I have a 0.50 carb from EX and an aluminum carb body I am considering using.  Search is on for test tube stoppers.  I've only got one bottle (well two if you count Mama's wheel bottle, but I like dinner too much to try confiscating that one), so I'm not going to experiment too much with melting holes quite yet Kris.  I'll try that with another model.  Thanks for the tip!  Sound's like a good one.

That's what I was thinking about the the spring post pressure tap.  Thanks Brad, you saved me from messing up a perfectly good crankcase.  Do you have a source for a muffler that's compatible with a pressure tap?  I'm guessing that adding one to a throttle type isn't feasible.
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Re: Scary stuff I was wincing in fear!

Post  1/2A Nut on Tue Oct 09, 2018 10:05 pm

Hey that's great you have a RC carb it's a good investment.
The test tube stopper is called "bung" proper name for them.
What size is the ID in mm with the aluminum cap removed?
Make sure you get the right size metal tube not the catch all size typically used
in fuel tanks for your tank think 2mm ID tube approx .08" anymore than that
for a 1/2A .8cc / .05 engine is over kill.

Muffler:
Option 1:
http://www.exmodelengines.com/product.php?productid=18099&cat=267&page=1
Note where the cylinder exhaust ports are in relation to where you wish the mufflers exhaust to exit
to best clear the plane. Then tap and install a pressure nipple right where one of the cylinder exhaust
ports are. You want to select the one furthest away from the mufflers exhaust hole for best pressure.
Note you can add a header to this with care using all thread tube and two thin nuts.
For the pressure nipple you want a small one suitable 1/2A size. If you need to source
one look for one with 1.2 - 1.5mm ID

Option 2:
http://www.exmodelengines.com/product.php?productid=17862&cat=267&page=1
This is more restrictive / will require you to use a round file and open up the exhaust exit
more right at the manifold where the header starts. There is plenty of excess extra effort here
will get you some more power.  The reward is better goo control and you can put the pressure tap
directly on the header. Go back to page 1 reference the work I did to open up the muffler for better breathing.

Stopper Bung - free shipping recommend buying at least two for future project!
Note shop for best price I like this link as it shows you the size dimensions, from there you can price shop.
Pick out a bung that the center dia. will be a snug fit into the bottle top fit it in place and see just how deep in
it goes before razor blade slicing the excess length for a nice proportional fit.
Drill two holes undersized so it it snug on the metal tube. You will have a fantastic low weight tank that will last for years.
https://www.ebay.com/itm/IK-Solid-Rubber-Stopper-Bung-Laboratory-Engine-Push-In-Sealing-Plug-15-Size-Tid/253319600073?hash=item3afb0657c9Ⓜm9QZUitXgPBjuWwK5h0HwLg:rk:2🇵🇫0

Perfect 1/2A size pressure fittings for .020 to .074
Or dig through your stash to see if you have something small enough.
https://www.ebay.com/itm/CLIPPARD-11750-02-3-56-to-1-16-I-D-BRASS-HOSE-FITTING-PKG-OF-10/272405170975?hash=item3f6c9d0b1f:g:EYUAAOSwNRdX-BM6:rk:7🇵🇫0

3-56 x 1/16 ID
Approx 2.5M thread x 1.5M ID


Once you make your first small nitro tank you will be proud of your effort and sad to see it buried
out of sight in the wing. Note I have the heat shrink clear overlap over that ring on the bottle yours
would fare well if you leave a few threads left on the neck of the bottle for the heat shrink to grip to.
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Re: Scary stuff I was wincing in fear!

Post  Dave P. on Wed Oct 10, 2018 8:39 pm

Thank you Brad, for sharing your hard-won knowledge and for taking the time to go in to such detail and then for finding the links to the parts I need and then posting them.  Way above and beyond and I can't tell you how much I appreciate it. I hope I have the opportunity to follow your example and pass it forward sometime like you have.
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Re: Scary stuff I was wincing in fear!

Post  1/2A Nut on Thu Oct 11, 2018 11:52 pm

Your most welcome Dave Thumbs Up others looking in can do the same. Very Happy

I have finished the all aluminum tank, it's going to be used
with a performance engine for 5 ish min. flights using pressure.
A profile speed plane with the tank completely exposed with
two polished aluminum straps holding it in place. Plane will
be strong enough to handle 180 mph into the wind.

A portion of the anodizing was taken off the lip of the lid so only the front face is left red.
The brass was polished and ID was recovered after using a tubing cutter. I haven't checked
yet but capacity should be more, around 1.85oz filled to the brim 55cc



The .09 has benched well with a pressure tap, needs to be tested with a header / tuned pipe next.
I have a Uctkam 1.5cc tuned pipe just for this engine, the pipe has been tested with the more heavy AP .09.
With the results of the scary TD .05 on pipe I expect the .09 will be quite the screamer!
The mighty TD .09 has taken the DART to 144 mph open exhaust, with a tuned pipe 160 +mph is possible 5.25 x 6.5
Shown here with a beautiful radial mount / all aluminum case, a CNC header will make this a most serious performer.  


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Re: Scary stuff I was wincing in fear!

Post  1/2A Nut on Sat Oct 13, 2018 3:57 am

Last effort was to do a leak check, verify the over fill tube is at the top of the tank and
capacity check shown here the quantity it held was put into a Du-bro tank for reference.
Also full tank weight was checked.


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Re: Scary stuff I was wincing in fear!

Post  balogh on Sat Oct 13, 2018 4:03 am

Great work Brad. I see you added a pressure tap to the stock COX muffler..how does it work with the black slide ring also added? Do you then shim the cylinder to non-SPI?
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Re: Scary stuff I was wincing in fear!

Post  1/2A Nut on Sat Oct 13, 2018 4:26 am

As you can imagine in the field this can be open as far as you wish making the SPI function breathable enough.
The exhaust window was opened up just a bit as shown in the pic for the test. It should do even better wide open.

url=https://servimg.com/view/18577711/1604][/url]

I have modified my stock muffler, put a pressure tap in place of that useless power robbing
exhaust header. Big improvement with a peaked NV to sing mode good and steady. Pic shows
how much I had the window open for the exhaust, the pressure tap really woke this one up.
The pressure is only there when at full throttle so the idle is really good no flooding idle can
go way down with no issues. Nearly 2lbs of thrust strong HP/W output!

6.25x3.5NN Combat prop:
Static 20,914 rpm / 30.7oz thrust / 1.9lbs / .326hp / 243w / 64 mph pitch speed.
What would be the next move is ask Greg scale up a CNC header for this engine and try it with
a 1.5cc tuned pipe. I have a Utckam on the ready if it happens. Need to do the testing on the CNC
header TD .05 yet, hopefully soon, seen a preliminary milled unit it looked fantastic, low weight not bulky.


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Last edited by 1/2A Nut on Sat Oct 13, 2018 11:34 pm; edited 9 times in total
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Re: Scary stuff I was wincing in fear!

Post  balogh on Sat Oct 13, 2018 4:34 am

Thanks I also find the 09 with its large dia and unscreened venturi does not draw fuel really well but because I use balloon tank a pressure tap does not make much sense. I place the tank instead as near and high as the fuselage structure allows.
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Re: Scary stuff I was wincing in fear!

Post  RknRusty on Sat Oct 13, 2018 9:16 pm

Boy, you guys' dedication is amazing. I'm slightly humbled as a bolt 'em and go kind of hobbyist. Back in the days when I felt better and wasn't yet committed to CLPA, I had started tinkering, but never quite aspired to reach this level of performance. I do have a Q40 Pylon racing friend and he's a lot like y'all with the bigger power plants. These are amazing machines. Thanks for sharing all this cool stuff. I need to re-read some of it, as I just woke up from snoozing in front of my computer, Lol. I do that with my YouTube watch list too.

Carry on having fun,
Rusty

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Re: Scary stuff I was wincing in fear!

Post  RknRusty on Sat Oct 13, 2018 9:20 pm

balogh wrote:Thanks I also find the 09 with its large dia and unscreened venturi does not draw fuel really well but because I use balloon tank a pressure tap does not make much sense. I place the tank instead as near and high as the fuselage structure allows.
Andras, have you ever tried a double balloon? The fuel is in the inner balloon, and pressure is applied to the outer balloon. I honestly can't remember if I actually heard about that or if I just made it up.
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Re: Scary stuff I was wincing in fear!

Post  balogh on Sun Oct 14, 2018 12:40 am

Thanks Rusty that is also a good idea. It needs the outer balloon to be just a bit larger than the inner one so that the pressurization should start right after the engine is atarted. It practically means identical balloons one pulled into the other. The lead out of pressurization tube from the outer in a gas-tight way needs to be thought over.
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Re: Scary stuff I was wincing in fear!

Post  Surfer_kris on Sun Oct 14, 2018 2:05 am

You could also place the balloon inside a regular hardwalled tank, and mimic the Tettra Bubbless tanks.
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Re: Scary stuff I was wincing in fear!

Post  balogh on Sun Oct 14, 2018 2:23 am

Thanks Kris good idea I will check what hard wall tanks will fit in the nose as this is an issue with my smaller planes like the TeeDeeVooDoo that carries 1oz in a balloon tank good for a 4-5 minutes flight. I assume a 1.5oz hard wall will accommodate the 1oz balloon with some allowance for imperfect match of their contours.
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Re: Scary stuff I was wincing in fear!

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