Side Winder versus Inverted motors

[Chris Gilbert IRL-1638]

After a while of flying profiles of various sizes I've graduated onto full fuselage models.

What I don't understand is what the elusive better run of the inverted motor is.

Currently my experience of inverted motors is that once I get them running the run seems acceptable, but not different enough from my sidewinder models to justify the difficulty I seem to have starting inverted motors.

I can fuel and prime any of my sidewinders and guarantee a start within a few flicks, often first flick, but the inverted motors are a pain, too dry, or flooded. So far I can determine no pattern in terms of what the difference is. If I follow steps ABC today first start, too dry. Second start, flooded.

I've had to resort to starting them inverted, but neither my flying buddy nor I are particularly happy about turning the model over with a nicely revving 45 or 60 in the nose. And as far as doing that whilst flying solo is concerned.....

My starting battery is a a cyclon lead acid and I use an ammeter to drop the voltage. The ammeter is quite useful as I can tell immediately in the sidewinders whether the motor is too dry or too wet, and with the lead acid I've got lots of capacity for colder mornings. According to my calibrated work voltmeter I get 1.5 V at the plug. All motors use Enya no 3 plugs. Fuel is 5% nitro, all castor.

So,

1) what is the advantage of an inverted motor over a sidewinder
2) How can I get my inverted motors to start promptly.

So far I've been using a mix of old and new motors inverted - ST46s, ST650s and (new) Enya 45s and the results are the same. I've grown very familiar with the irritated hiss of a flooded super tigre.

[Paul Smith]

I agree, side mounted are much more user-friendly.

In my opinion, one major reason they don't perform as well in the air is FUEL TANK placement.  Simply putting a stock tank on the outboard side is bad enough.  But the adjustment gizmos make it even worse.  The fuel pickup winds up almost 2" outboard of the venturi.

By comparison, the tank of an upsidedown or upsideright setup is centered on the engine.  If possible, make a hole behind the engine of one of your profiles and center the tank between the hardwoods.  This might given you comparible performance.

[Bob Reeves]

My latest two stunt ships are sidewinders.. Mainly because I am running 4 strokes and they just work better in a sidewinder configuration.. That being said I wouldn't hesitate to use a two stroke in the same configuration. The only engine I know of that doesn't like to run on it's side is the Fox 35. Don't be concerned about the fuel tank location other than adjusting the height, just run muffler pressure and go for it.. It'll work fine.

I believe the reason most stunt ships were designed with inverted engines is the cleanliness of the installation and crank shaft position. Not because an upright or sidewinder configuration won't work. (Except of course if it's a Fox).

[Bill Little]

IMHO, upright and inverted installations in built up fuselages are an easy way to get everything (like tank installation) to work out easily.  With maple mounts and a side mounted engine, the tank must go between the mounts.  Then the mounts are kinda *suspended* in the fuselage.  Not like when they are glued to the doublers in a *standard* set up.

A full fuselage helps to lessen vibration giving a much more consistent run.  The Imitation and Mustunt I are cases of Profiles built with either upright or inverted engines. 

As to starting, most of our engines need more prime for the first start of the day.  After that, as long as it is fairly soon after our flight, less prime (if any) is usually needed to restart.

For starting that engine inverted, sneak up on it slowly.  Prime it the first time by flipping with the finger over the venturi for two or three flips, then three or four smart flips with the finger removed.  If that is not enough do one or two more with the finger over the venturi again.  If it is too much, then use less the next time.   You will get to learn what it takes for each engine under different circumstances.  After the first flight, only some regular flips might be all that is necessary (no prime).

One other thing, wait as long as possible to fuel up the model.  If it sits for a while, fuel might actually siphon into the engine getting it flooded.

[Bob Reeves]

Bear is correct about using maple mounts with a sidewinder, very difficult to have everything come out right and still be able to install a tank. This is the reason I moved to RC firewall engine mounts. My Score proved to me they will work just as well if not better than maple mounts and in the end the overall weight is about the same.

[Wynn Robins]

there are other reasons to mount motors in the side cofiguration also - with some engines, including the Stalker 66RE I have- the can "burp" or miss at particular parts of the pattern - now, I have heard the stalker does this on the outside part of the square eights.......but mount it sideways, and the problem goes away.....

Radial mounts work great - all the room you need in the back for fuel tanks etc.........just seems like a lot of CL flyers are "old school" - you know, maple bearers, metal tanks etc......

[Bill Little]

Over 15 years ago, my oldest son was learning to fly the pattern.  We had pretty well *used up* a TF Tutor (small original one).  Having to replace the fuselage (again!) in front of the wing, we went with a 1/4" Ply firewall, some blocks shaped into the fuselage, and a K/H R/C mount.  A Fox 35 inverted and it flew better than it ever did!

[Shultzie]

The late Tim Dunlop of Portland Oregon...loved side mounted engines and used that configuration throughout the years in the majority of his beautifully crafted and unique stunt models. They ran beautifully with the most consistant engine runs you can imagine.
 However that said...anything my friend Tim Dunlop flew or built...regardless whether the engines were upside down, sidemounted or upright, alway ran with perfection.
 Tim even once built a model that he inclosed the engine at an angle so as to completely hide that OS Max muffler into the cowling itself.
 (He used one of the first firewall shock-resistant molded graphite mounts that was an experimental one that I think Bob Wilder found somewhere. That too...ran smooth as glass....

perhaps due to the fact that Tim was a STICKLER FOR SPENDING A HUGE AMOUNT OF TIME...BALANCING EVERYTHING THAT WAS ATTACHED TO THE ENGINE---STARTING WITH THE PROP-THE SPINNER...AND EVEN THE CRANKSHAFT AND INNER GUTS OF HIS ENGINES. 
Anyone who remembers TIM DUNLOP...was precise and dedicated in everything he did. Maybe due in part to his many years as a Portland Oregon Fire Dept. Captain and then Chief.
GADS! WE MISS THAT WONDERFULLY BLESSED AND GIFTED HUMAN BEING...that we were so lucky to call our friend and stunt model peer.
Although Tim built many models side mounted...this example is my favorite looking and flying side mounted that I have ever had the pleasure to fly.
Tim with one of his modified Thunderbirds using side mounted engines to perfection.

[Willis Swindell]

My last two planes I built had side mounted engines. I used the fire wall mounts with a hatch on the bottom to mount the tank. This system works great and makes it easy to work on the engine.
Willis 

[john e. holliday]

Starting inverted engines(planes sitting upright) is easy if you know the secret.  Bigiron taught me and I have seen Silver Fox do it also.  Before hooking up lines you turn the aiplane over so the engine is upright.  Prime it and flip the prop.  Hook up battery and pull the prop thru.  May feel a bump, may not.  Flip the prop and run the prime out.  Prime it again, hook up battery and flip the prop.  Then if you don't take all day to get to the circle the engine should start fairly easy.  It takes practice to learn to start one without turning the plane over.  Have fun,  DOC Holliday

[Kim Doherty]

Perhaps the most successful side winder design of all time, Arden Zhang's two time W/C winning "SkyWriter" Fully molded fuselage, full depth maple mounts (just in the engine compartment - tapered to 1/8 x 3/8 from behind the engine compartment to just ahead of the wing), motor mounts are webbed in all directions with vertical grain balsa outboard to the fuselage shell. No vibration, no flooding, easy starting, needle directly on top of fuselage for easy setting.

Arden said that the reason for mounting the engine on its side was to ensure that the engine "saw" the same internal forces both upright and inverted during insides and outsides. It definitely ran quite well.

Pictured here is one of my SkyWriters.

Kim.

[don Burke]

Something that will help an inverted engine retain a prime is to put a screen over the venturi.  Fine wire mesh or a piece of nylon hose held on with a tie wrap or wire wrap works well.

[Chris Gilbert IRL-1638]

Finally got my inverted motors beat.

First flick starts are not unusual any more, just like my sidewinders

I thought I'd better put this here in case some others had the same trouble with inverted motors as I was having

This is my procedure, and what it means to me is that inverted motor models are no longer scary - I don't worry whether I will spend my day flicking or flying, 'cause I know I'll be spending it flying now.

When I get to the field I furst burp my motor a few times to clear out any congealed oil. It seems I only need to do this before the first start of the day.

Before flying I do the following:

1) Invert model and prime the motor (using a very small syringe) 0.3 to 0.5 cc seems to be about right
2) Turn prop over a few times before placing the model back on it's wheels.
3) Fuel up
4) 10 to 15 rapid flicks just before starting
5) Connect glow driver and signal to judges
6) backflip
7) walk out to handle and start flying.

[john e. holliday]

So very glad to hear things are working for you.  DOC Holliday