taildrager67

Hello Members

I was excited seeing new rc planes with there engines mounted in variuos positions . Giving you options for cowls and muffler placment.
What i need help with is if i mount my new Webra Speed .40 upside down and make sure the fuel tank is in the right position. Is it
going to idel and run correct while flying.
Is there other things i need too take in acount?

Will i have to balance my plane a certain way?

The plane kit i am building is a GP Dazzler .40 - The engine is a Webra Speed 2 stroke .40 .

I would like to mount the engine upside down so there will be less mess with fuel blowing all over the newly monokoted wings and
fuselage. Also im going to build a cowl for the front to cover most the engine. I also like the way the muffler will blow strait down
and how linkages hook up.

I just dont know how well the engines will run being inverted. I am new to this RC Airplane Hobby stuff. I did fly U control with
my father many years ago and build U control airplane kits. But remote control is a whole defferent story. So if anyone
reads this post and knows about inverted engines , I would be thankfull for your advice .

Thank You taildrager67

RevGQ

First, you look to find and inverted muffler. This allows the pipping to hang down. Second, you may have to lean the low-end a tad or simply run a glow system, which can be as simple as a 1.5v batter, battery holder, pos and neg wire and glow plug cap. I have a system from SM Electronics that allows me to plug into my receiver and set when I want the energy to plug to flow.

downunder

The very first thing you must do is be certain the tank is in the correct position for an inverted engine (any engine position actually). For all models the centre line of the tank must be very close to being level with the centre of the spray bar in the carb barrel. Usually the spray bar is around 1" higher than the engine mounts and most models are designed for an upright engine so that the centre of the tank is about 1" higher than the engine mount. But when you invert an engine the spray bar is then 1" lower than the engine mounts so the tank must be lowered by 2" to bring it back to the spray bar level. The ideal position for the tank (regardless of upright or inverted) is to have the centre line about 3/8" lower than the spray bar.

The normal muffler will work just as well but you must remember that now the muffler will be well below the tank level and it's then quite possible for fuel to run from the tank down into the muffler if you overfill. The cure is to loop the pressure line up above the top of the tank (the loop will be hidden inside the cowl) and to make sure it's full of air after filling the tank.

Inverted engines need to have the idle mix set a bit more carefully than you can get away with when using an upright engine because if they're a bit rich then longish idling periods will load up the crankcase with raw fuel which can flood the glowplug when you open the throttle.

They're a little harder to prime because now you're trying to get fuel to run uphill from the carb and into the engine but it's not difficult. The one thing to watch is that you don't overprime or too much fuel will get down into the cylinder head. This not only cools the plug but it can completely fill the combustion chamber and then the engine will lock up solid (hydraulic lock) and you've got a very good chance of bending a con rod. The tip here is that when you think you've got the engine primed, turn the prop over by hand a few times without the glow starter connected and if it seems to give more resistance than usual then it's likely to be slightly flooded. If it won't turn over at all then take the plug out and give it a quick hit with the starter to blow out the excess.

This might all sound a bit complicated but it's not, it's just a matter of paying attention to details.

Jim C.

my .65la is inverted. It runs good but idle and starting can be a pain until you get it set. You have to lean out the idle a bit more.

j.duncker

My Feedback: (2)

IMHO the key line in your post was this

In view of this keep your engine upright. It wil be easier to start, set up and adjust the needle..