News:



  • May 05, 2024, 05:29:38 PM

Login with username, password and session length

« previous next »
Pages: [1]   Go Down

Author Topic: Need help setting up pacifier fuel system  (Read 1847 times)

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 262
Need help setting up pacifier fuel system
« on: January 28, 2018, 12:34:35 AM »
Ok so on another post I found out where to buy pacifiers on eBay (thanks Dane) and have some coming. I have an old Sneeker that uses this system and need advice on how to set up and run this type of fuel delivery system. The engine is a modified ST G21 35 with a combat venturi on it. Thanks, Tim
Logged
Baton Rouge Bi-Liners
AMA 179681

Offline katana

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 161
Re: Need help setting up pacifier fuel system
« Reply #1 on: January 28, 2018, 04:08:40 AM »
Back in the day I used pacifiers on G20/15 powered combat planes and method then was fuel up with 100ml syringe then clamp the fuel line with a bulldog clip and re-attach fuel line to the NVA. Screw the needle in to close and open back about a 1/8th turn. Prime down venturi and flick over to distribute, connect glo lead and flick to start. As soon as started with high rpm, unclip the bulldog clip and hopefully it won't stall or flood. If it does adjust minutely until correct - strong very high rpm ( at least it was with a combat wing). Once set, I virtually never touched it again and had very reliable one flick starts - just remember the spinning prop trying to unclip the fuel pipe! If this is in a stunt plane, the usual tiny choke venturi's aren't necessary due to forced fuel feed but the high rpm's will need very short pitch props to keep overall airspeed down. Things may have changed over the years but that system worked for me.
Logged

Online Dave_Trible

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6164
Re: Need help setting up pacifier fuel system
« Reply #2 on: January 28, 2018, 08:40:13 AM »
If you haven’t already you’ll need to fashion a pacifier ‘pod’ or enlarged space between the two wing ribs right behind the engine and make a hole out the top about 1/2” for inserting the pacifier.  I usually would pour some thinned dope inside and work it around,  then pour out the extra to fuel proof when you blow a pacifier.  Don’t make the pod too large.  You are only putting in about three ounces.  Fill one and look at it to understand the space needed.  Not all that.  I would insert a 3/4” long 1/8” brass tube into a piece of silicone fuel line, then rubber band a pacifier on over this with a couple good tight bands.  Fill and clamp as described above.  Open the Tiger needle about 3/4 turn.  Pinch off the fuel line with your fingers and remove the clamp.  Start the engine, releasing the line when it goes.  If it starts to choke out squeeze the line and shut the needle a bit.  The needle band is real narrow here so back and forth till you you get a solid run.  Set just shy of max RPM and launch.

Dave
Logged
AMA 20934
FAA Certificate FA3ATY4T94

Online Dave_Trible

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6164
Re: Need help setting up pacifier fuel system
« Reply #3 on: January 28, 2018, 01:09:13 PM »
Home now so here is photo of one of my Sneekers with pod and pacifier.

Dave
Logged
AMA 20934
FAA Certificate FA3ATY4T94

Offline katana

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 161
Re: Need help setting up pacifier fuel system
« Reply #4 on: January 28, 2018, 02:41:05 PM »
Here is a jpeg plan with 1-2-3 instructions on pacifiers and pod building for reference. I used to use a plastic detergent bottle about 2.5" dia and solarfilm over the balsa cap - didn't really worry about fuel proofing as planes had shorter life LOL!
Logged

Offline Chad Hill

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 309
Re: Need help setting up pacifier fuel system
« Reply #5 on: January 28, 2018, 07:57:13 PM »
Years ago we used Vienna Sausage cans for pacifier pods.
Logged

Offline Dane Martin

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2804
  • heli pilot BHOR
Re: Need help setting up pacifier fuel system
« Reply #6 on: January 29, 2018, 11:21:49 AM »
Tim has an existing plane, pod already built. But all great info given here. So now you know for the next one Tim. I will try to get a video up tonight on my starting procedure. It is simple, quick and effective. Bill Maywald taught me how to start and run bladder systems on combat planes.
Again, these guys giving advice are all good stuff on the building and set up.
Logged

Offline Fredvon4

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2099
  • Central Texas
Re: Need help setting up pacifier fuel system
« Reply #7 on: January 29, 2018, 12:26:15 PM »
When I started using pressure I was really frustrated util several of the guys taught me how to initially set the needle

Fill bladder/pacifier, pinch off, attach to NVA, invert engine ( so not to flood) Un pinch fuel line and adjust drops OUT of NVA on to ground to be between 4 to 6 per second for a Big block engine .25/.36

Good starting point on needle..   some further tweaking will be necessary.... if it sags too much a quick pinch of the fuel line will usually peak it some as you lean or richen the needle to fine the sweet spot.... richen slightly before launch to account for the in air unloading.... 14 minuet very lean run at 100+MPH is a royal PITA

Then they schooled me to find exactly what MY engine liked for a good PRIME

When it was all done I learned how to get a Nelson or Fox MK VI started in one or two flick starts
Logged
"A good scare teaches more than good advice"

Fred von Gortler IV

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 262
Re: Need help setting up pacifier fuel system
« Reply #8 on: January 30, 2018, 03:37:55 AM »
Thanks a lot for all the info and advice on running this type of setup! I really do appreciate this very much. Dane, I can’t wait to see the video on this. Tim
Logged
Baton Rouge Bi-Liners
AMA 179681

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 262
Re: Need help setting up pacifier fuel system
« Reply #9 on: February 01, 2018, 04:23:39 AM »
Dane, the pacifiers from eBay should be here tomorrow, do you know how much fuel they will hold? Thanks, Tim
Logged
Baton Rouge Bi-Liners
AMA 179681

Offline Dane Martin

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2804
  • heli pilot BHOR
Re: Need help setting up pacifier fuel system
« Reply #10 on: February 01, 2018, 08:49:07 AM »
About 3 oz I think? I would only do 1 or 2 for now. Also, you'll want to "train" the bag to inflate away from the insert plug.
I didn't forget about the video. But I gotta wait until at least tomorrow to get it going.
Logged

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 262
Re: Need help setting up pacifier fuel system
« Reply #11 on: February 03, 2018, 06:06:06 AM »
Thanks Dane! Can’t wait to see the video. I will be working on the Sneeker’s fuel system this weekend but I am also on call. Tim
Logged
Baton Rouge Bi-Liners
AMA 179681

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 262
Re: Need help setting up pacifier fuel system
« Reply #12 on: February 03, 2018, 06:53:57 PM »
I ran the plane today! I really like the pacifier system. Thanks to everyone for their help, Tim
Logged
Baton Rouge Bi-Liners
AMA 179681

Offline phil c

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2480
Re: Need help setting up pacifier fuel system
« Reply #13 on: February 04, 2018, 02:23:48 PM »
Quote from: Tim Chenevert on February 03, 2018, 06:53:57 PM
I ran the plane today! I really like the pacifier system. Thanks to everyone for their help, Tim
Pacifiers are nice because they produce less pressure- 4-6psi making them much easier to set.  They blow up pretty much evenly all around, but eventually they start to get lumpy and give uneven runs.
Surgical tubing bladders (1/4in id x 1/16in wall) produce a lot more pressure- 15-20 psi.  That requires a very narrow taper needle, such as F2D, or an engine that gulps fuel such as a Nelson- 5oz. in 2-1/2min.  Super Tigre style needle valves work OK, but are a bit sensitive.  The heavy bladder wall holds up better, often 30-40 runs, before it starts to develop weak spots.  The long tube, 3-5inches, does need to be trained to blow up consistently.

For any pressure bladder drain the fuel out completely between flights, or certainly at the end of a session.  Leaving a bladder with fuel in it in the plane in the hot sun will make it go soft after just a few flying sessions, or even 4-5 runs.
Logged
phil Cartier

Offline Tim Chenevert

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 262
Re: Need help setting up pacifier fuel system
« Reply #14 on: February 06, 2018, 03:49:27 AM »
Thanks to everyone with their advice and it was all well taken. My Sneeker flew yesterday on  pressure like in its old days! What an experience for me! Awesome plane and loved the speed and sound of it. Perry said it sounded like a piped engine. Tim
Logged
Baton Rouge Bi-Liners
AMA 179681

Advertise Here
Pages: [1]   Go Up
« previous next »
Tags:
 


Advertise Here