Originally Posted by Brutus1967

Place a constant, elevated pressure at the ventpipe of that mariotte bottle, and STILL the liquid flow would be constant. Faster, but constant, because again,submerged admission of the gas, fixates the pressure at that level in the liquid.

Agreed. That is why it works well in a constant throttle set-up, like in CL or pylon racing.

It also works very well in constant attitude setups like non-aerobatic helicopters.... (resultant of vectors Always near parallel to the mainshaft)

I understood exactly that the submerged vent tube provides resistance to siphoning because of the depth to which it is submerged. That resistance would be different and reduced if the lower end of the tube was above the fluid. Resistance is caused by the pressure of the liquid column at the bottom of the submerged vent tube. In order to flow the siphon draws on both the liquid and the additional resistance caused bu the liquid column. Got it. No failure to comprehend. I never indicated that its diameter was a factor. I have a reasonable understanding of fluid dynamics. I just failed on the initial view to grasp it's benefits.

Honestly, I appreciate the clarification. You have to be doing something right to go 65 minutes on 6 ounces of fuel.

Apologies if I came across wrong.....

Still... you are using "resistance", where you should be using "pressure". Resistance is not a factor in this set-up.They are two fairly different things, which led me to the wrong assumption about your understanding... Must be the language barrier on my side...

Nobody raised a needle issue? Bad needle o-ring will also give the same sympton.

Worth a try I guess?!

My TT F91S had the same issue with the stock carb. Engine quits when backed off from full throttle.

Changed it to ASP FS 91 carb (with few mounting mods), and the issue went away.

I know it is a 4 stroke.. but the issue wasn't about the back pressure.

Originally Posted by David2011

Honestly, I appreciate the clarification. You have to be doing something right to go 65 minutes on 6 ounces of fuel.

Seeing the extended flight times is very interesting. Yes, something right !
Helps one to appreciate the Maynard Hill Transatlantic flight . Over 38 hours on .8 gallons of Coleman Fuel. That works out to around 22 minutes to the ounce of fuel !

Originally Posted by Gary Cee

Seeing the extended flight times is very interesting. Yes, something right !
Helps one to appreciate the Maynard Hill Transatlantic flight . Over 38 hours on .8 gallons of Coleman Fuel. That works out to around 22 minutes to the ounce of fuel !

I did not manage that much.... but I am getting about half of that (10 minutes to the ounce) and actually, not bad for something as quickly thrown together as mine....

I think he was getting about 2hours, 15 minutes for 6 ounces burned. He chose Coleman Fuel for it's clean burning and high specific energy content.

If I were burning gaspoline type fuel, Coleman would likely be it. I know it isn't cheap but.. .. ..

Brutus, in Modelbouwforum I read one of the inlet valves is leaking. Of which engine is that? Does it has to do with overheating?

TF

While this thread seems to have gone a little ways off the reservation, it did inspire my next project. After having just finished a new build, I decided to come back to my little Revolver and go about putting the stock muffler on. I plan to remove the baffle. I will need to use a spacer, but the one I have will need some grinding as it does not come close to matching the width of the stock exhaust port. The bolt pattern is the same, as well as the port height, but its much narrower. By the time I get to the cowl I may as well just about cut the bottom half off
Maybe after this muffler experiment Ill order a new cowl and cut it out for whatever muffler stays on there, but I have a feeling its going to be the stock muffler.

Put the stock muffler on it and test fly it without the cowl first.

That's what I plan to do, but from the sounds of it the stock muffler will be staying on there.

Originally Posted by Eric_04

That's what I plan to do, but from the sounds of it the stock muffler will be staying on there.

Let us know how it goes. I've gotten my pitts muffler singing pretty good after I ditched the uniflow system, but I wouldn't be against putting the stock pipe back on if it meant a significant increase in power.

The stock exhaust may not be a significant increase in power, but it will definitely be a significant increase in throttle response and reliability. If you want more power and don't want to spend the time to tune a full length pipe, call Dub Jett and get a Jettstream muffler. It will give you about 80% of the powre increase of a tuned pipe with bolt on convenience. Just let Dub know the engine and RPM range you run so he can tune it to your application.

Scott

AX 55 s are very happy with APC 12x4 s I think you are over propped with 12x10s Stick with those 11x7s a 12x8 is too much prop for an AX 55