Citazione:
Originalmente inviato da losisi  visto e risposto 
io ho messo il mio Ursus al banco, qualche settimana fa...non ho la risonanza originale OPS ed ho montato una per STx61...il motore gira forte, a 34 cm non ho raggiunto i regimi indicati nel manuale OPS ma comunque mi ha positivamente impressionato,
ho notato solo ( e forse dipende dal tipo di pipa o non avevo la candela giusta) una certa tendenza a "imbrattarsi" nel passaggio ..ma min e max erano regolari e puliti
qua servirebbero la memoria storica e l'esperienza di Pieromuzio...ma nn so se frequenta più il forum....speriamo ci legga e ci illumini..oppure la faccia qualcun altro con esperienza di OPS io, sinceramente, ne ho pochina.... |
Qualche periodo fa avevo letto un bel intervento a firma di Piero Muzio che parlava
della migliore modalità di un buon rodaggio e circa la risonanza diceva :
"...Se fosse molto critico allungare la pipa di 5 mm od allegerire l'elica. Se borbotta sempre la marmitta è troppo lunga, accorciare di 5 mm."
Sul forum si potrebbe rintracciare questo intervento.-
Ho poi anche un altro intervento che non ricordo dove l'ho trovato e chiedo scusa a colui che l'ha scritto ma lo riporto anche se in inglese,penso possa servire :
"I was going to write a small article on how to tune a tuned pipe during the build but decided I will do it now and get it out of the way.
The way I tune the pipe works very well and have had excellent results in the past.
Tune Pipe Tuning
Step one Run-in the Engine using standard exhaust so that it runs at maximum power on the recommended prop for running in.
Step two Decide what prop you are going to use for Aerobatics normally stated in instructions Now remember aerobatic models use a higher pitch prop compared to sports flying. As an example if the prop size recommended for Aerobatics happens to be 12x6 (standard exhaust) then you need to buy two props 12x7 and 12x8.
Step Three Fit the 12x8 prop for tuning. At this stage use the tuned pipe as supplied (nothing cut off) run the engine to max power and note the RPM achieved. Say you achieved 14000 rpm
Step Three "B"Now switch the engine off and let it cool for a while, remove the pipe and cut off about 1/4 inch either from the down pipe or the tuned pipe itself where it's joined by the silicon heavy duty tube.
Step four Start the engine run it up to max power you will see increased RPM Note the RPM and switch off the engine again and repeat Step three "B"
Carry on doing this until you no longer get increase in RPM or you get slightly decreased RPM. That is the correct length of the pipe but it is now too short for 12x8 prop but just right for the 12x7 prop.
Step five Mark the position of the pipe or measure it from a given reference point for future use. Replace the prop with the flight prop 12x7 run it up and you will find you have probably gained 3000 plus rpm.
That is all there is to it, time consumming but well worth the effort. The sliding of pipe in and out for max power without going through the above procedure will not give you the right results. You will have to tune every flight too.
Note: If you change the fuel or a glow plug, (use hot glow plug) from the one you used for tuning the pipe, the performance will altert (most likely less performance) The engines used with tuned pipe wear out faster than the ones used used with standard silencer. It is not uncommon to replace the engine after every 100 flights of 10 min duration.approx 16 hours of total use"
Gemmis.-