Home › Forums › Free Flight › The Swap Meet › Wanted Venturi for OS MAX .19 111
- This topic has 19 replies, 8 voices, and was last updated 13 years, 7 months ago by Anonymous.
08/07/2009 at 11:53 pm #41169AnonymousInactive
Need a venturi for Max .19 111.
Cheers,Dan08/08/2009 at 4:22 am #47630
I make my own, and can do the same for you. $20.00 shipped. However, mine are for pressure feed. Do you need suction?08/08/2009 at 3:49 pm #47631AnonymousInactive
I found some venturi stock and will make one with it. Wanted to make engine run on suction for now.
Cheers,Dan08/09/2009 at 7:48 pm #47632
Suction feed does exactly that! It really sucks. Once you go to bladders, life becomes much simpler. Even if there is no performance gain, the steady needle setting, even engine runs, and ease of starting is worth it.08/09/2009 at 9:24 pm #47633
Dean, I thought bladders replaced hard tank pressure systems?
Not that they are that great.
Are you saying that if you don’t change the venturi diameter that a bladder is all plusses and if you open up the venturi and use a bladder you get performance too?
Dennis08/09/2009 at 9:48 pm #47634George ReinhartParticipant
It doesn’t matter what size the venturi is.
A “bladder” system is a primitive form of fuel injection.
C/L speed flyers used in the fifties (maybe earlier) where it migrated to C/L combat which I was flying as well as Free Flight and so, started using bladders about 56 or 57 in Free Flight models.
Didn’t dawn on me you should open up the venturi.
I think the Fox 29R mught have been the first production engine to recognize the advantages of a super large venturi because they wouldn’t run on suction (there just wasn’t any with that big hole in front).
And.. bladders meant rubber pen bladders from the stationery(sp?) store.
Cheers!08/10/2009 at 2:11 am #47635
To answer your question last first. If you open the venturi there is generally a performance boost due to more air flow being available. A large venturi will make suction feed impossible so the need for some sort of pressure system is neccessary.
The hard tank is far more complex than the simple bladder although many of our UK bretheren like them, possibly due to the technical challenge they pose. Remember, these folks developed the score keeping system in Tennis 🙂
With the hard tank you have many, many, many opportunities for leaks, and a check valve is needed in the pressure line to keep fuel from flowing back and flooding the crank case.
All this is eliminated with the bladder. Engines up to .15 can be easily hand started by pinching off the fuel line with a thumb and cranking with a few drops of prime in the intake. Larger engines really need some sort of starter due to the need to use two hands to grip the fuselage.08/10/2009 at 10:51 am #47636
Thanks Dean, I thought it more curious that a bladder worked well with a std venturi. Since the amount of air going thru is limited, so is the fuel and that seems to mean maintaining a miniscule fuel flow under pressure. Seems that the flow could be difficult to maintain in a situation where the needle is almost shut down.
Maybe bladders don’t produce that much pressure?
My only experience is with the old pen bladders and I only used them with large venturi’s[c/l speed].08/11/2009 at 2:40 am #47637
Go to Hank Nystrom’s TexasTimers.com website for an excellent how to making bladders with modern materials. Also kittingittogether.com has good info as well. Hank has all the fittings you need.
I still use actual pen bladders actually called ink sacs. Get them at Pendemonium.com. #12 works for 1/2A and #14 for larger. While the fuel tubing bladders are cheap and easy to make. The ink sacs are neoprene and as such, last much longer. Not unusual to last several contests.
My point about the smaller venturi is that even without a power increase, the bladder system ensures a very steady fuel flow, and no sag during launch acceleration. 🙂08/11/2009 at 11:26 am #47638
Dean, Thanks for the clarification.
I picked up bladder materials from Hank at the last Nat’s.08/11/2009 at 8:38 pm #47639AnonymousInactive
The Swapmeet isn’t really a place to discuss fuel tanks, but it was the French that developed the scoring system in tennis. So far as bizarre scoring systems and fuel tanks relate, remember the Electral College System and maybe things get a bit more balanced 😀 (ribbing for fun only, no disrespect intended).
No problems at all with hard tanks and pressure, just as easy as a bladder, the only disadvantages are a tiny bit of weight and you have to solder metal to make them. No pinching, no syringe, constant pressure, no overboard dumping or showers of fuel for the unexpecting on the ground!
p.s. I agree, don’t bother with suction, and yes, I’m from the UK.08/11/2009 at 10:01 pm #47640gosParticipant
Good onya JB.
And I’m from OZ and also LOVE hard tanks on pressure.
THE only way to go.
Those pesky bladders are soooooo messy. But I have used them……Until I saw the light.
Flame suit well and truly on. 🙂08/11/2009 at 11:24 pm #47641AnonymousInactive
Wow, was just looking for venturie. I also fly UC and use hard tanks on pressure/ uniflow/ and bladders for Combat ships.
Dan08/12/2009 at 2:34 am #47642AnonymousInactive
Sorry Dan, I couldn’t resist!
John08/12/2009 at 3:06 am #47643JIM MOSELEYParticipant
>Those pesky bladders are soooooo messy. But I have used them……Until I saw the light.
That’s odd. I used those pesky hard tanks .. Until I saw the light
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