Inverted Engine mounting
 

I asked this question in the general "Questions and Answers" category, before I found the engines category. I think this is a better place to ask, so here goes. It is a known fact that inverting an engine, can make it difficult to start and may decrease the reliability of the idle. Clarence Lee (an engine guy whom I have the highest regard for) as recently as within this last year has talked about the problems of inverting an engine. The question was about inverting a 4 stroke and Mr. Lee strongly suggested the addition of an automatic glow plug driver.

The question is; Inverting can cause reliability problems, so why are manufacturers producing more and more airplanes designed for inverted engine installations? This seems especially true with 3D airplanes! Most 3D designs are not scale, so why invert? In an all out competition scale airplane, I can almost see and can understand why some people invert, to hide the big cylinder. However, I have to say, I just don't get it!

Obviously, we (as R/Cers) are O.K. with this as the manufacturers keep designing airplanes with inverted engines.

RE: Inverted Engine mounting
 

Inverted mounting gives a higher engine placement and still keeps a good looking fuselage profile. This allows for a larger propeller and more ground clearance without long, spindly landing gear legs.

Dr.1

RE: Inverted Engine mounting
 

The UCD's are a prime example of problems stemming from inverted engines, you can't ever move the tank w/out a lot of hassel. There are a lot of nice looking planes around that don't have inverted engines. Side mounting works well for me but will not work out on my Harrier as the muffler will not clear.
We then become involved with pumps, etc. What a hassel, Its time someone designed their planes with the option for upright,inverted or side mounting.

RE: Inverted Engine mounting
 

Hi, this is my first post and frankly this is a great topic . I can say i speak from experience because i have a pilatus pc-9 by seagull models and the engine is inverted. The engine used for my application is a super tigre 51 and i just want to say one thing it has been the worst experince i have ever had simply because of the inverted placement of the engine. Yes it is scale but for reliabillity it has become a dead stick trainning platform. After taking off and flying a couple of patterns around the field I simply decrease throttle and as soon as I drop the throotle it dies dosent even try to idle .Its a beautifull plane and is scale but i would much rather have the engine mounted on the side and sticking out of the cowl than what i have now in all theres no enjoyment for me with an inverted engine. thanks and have a great day

RE: Inverted Engine mounting
 

The issues with inverted mounted engines are rough. Literally - it can cause rough running. In my experience it has been worse with 2 stokes than 4 strokes and it's simply do to the placement of the glow plug in the two different types of engines. 2's have the glow plug in the very top of the cylinder and when inverted the pool of fuel that will accumulate there will directly cool the plug. In 4's the plug is typically offset so that that pool of fuel/oil won't kill the plug as much beacuase the plug isn't at the bottom of it. Plus, 4 stroke plugs tend to be hotter types anyway.

Next is the tank placement issue. The tank placement in ARFs typically sucks - no other way to put it unless they are designing all of these airframes around pumped engines (which they aren't).

I recently modified the heck out of my CG Matrix 40 because the engine is inverted but the tank was a full inch higher centerline to centerline (of the carb). It's now about 1/4" higher and things are drastically better. Heck it even idles well, it's a magnum 91 4 stroke on 20% fuel.

It's hard to argue with someone of Mr. Lee's stature and he simply is correct; glow heat on an inverted engine will make things tons better but my beef is that it is simply treating the symptoms and not the cause.

The cause is a low heat type plug in 2 strokes and improper tank placement overall. Fix those issues and your symptoms will drastically reduce. At that point there are other alternatives to treat these symptoms that can be taken. The next one for me is to use a fuel with more nitro (specifically on 4 strokes) as this will smooth out the idle but it will not overcome loading up due to a rich situation. If the tank can't be moved enough to make all the difference and a proper heat plug can't be used then constant (at lower throttle settings) glow heat is the answer.

Just my take...:D

RE: Inverted Engine mounting
 

geez, if they fixed every problem for ya it really wouldnt be much fun and there wouldnt be that great feeling of "i did it" would there? not trying get anybodys goat, but just trying to get ya to realize that its fun to have a problem once in a while!!! isnt it?:D you guys have fun!!

some of my best learning has come from problems of inverted engines, and fixing them.;)

RE: Inverted Engine mounting
 

A once in a while problem I can handle........a great flying plane that constantly deadsticks unless chopped up to make the engine run properly is not a little problem to enjoy. Wished you had the problem and I had a feather, we would both be tickled.

RE: Inverted Engine mounting
 

didnt mean to pyo gizmo, i would be glad to help you move that tank in your 60 size ucd, but your right about the 46(not easy but not needed), sorry if you took it wrong[:o]

RE: Inverted Engine mounting
 

I've had several different engines running inverted, and have had ABSOLUTELY no problems with any of them, in fact I don't treat them any different then my uprights... I've had both an irvine .53 and saito .72 inverted in my ucando, and a tower .46 inverted on my airboat...

setup and proper starting procedures become more important, but nothing that you shouldn't pay attention to anyway IMHO.

RE: Inverted Engine mounting
 

I currently have 2 Saito .72's, 2 Mag .91'a and an Irivine .53 mounted upside down.. No problems at all to speak of.. I use a remote glow starter to strart them as the glow plugs are kind of close to the ground... No onboard glow driver... I hate cutting up good looking cowls.. A hole in the bottom is usually necessary for cooling so upside down works nice.

RE: Inverted Engine mounting
 

The centre of most carbs is about 1" above the mounting lugs so with an upright engine the tank C/L is set for this height. Mount the engine on its side and you've effectively raised the tank one inch. Invert the engine and you've effectively raised the tank two inches. Unless the tank can be lowered then you've got problem #1. An inverted engine is more critical on the idle tune, it won't tolerate as rich as mixture as you can get away with when upright so problem #2 is learning to set the idle mix better. In almost all cases, fixing #1 and #2 will make it dead reliable but if not then try an idle bar plug or even a 4 stroke plug which has the extended nose so fuel can't collect and drown it.

RE: Inverted Engine mounting
 

(In reply to Iron Cross)
Although parts of my question relate to the known decrease in reliability of inverted engines, the gist of my question really isn't how to operate an engine inverted. The question is why are the manufacturers designing airplanes for inverted engine operation? I have been in the hobby since 1969. 20 years or so ago, the 4 cycle caught on and has increased in popularity ever since. Until recently, manufacturers/designers understood inverting engines was to be avoided and designed aircraft accordingly! As I said, I can almost understand scale folks deciding to invert for scale appearance, however, many of the new 3D designs have inverted installations and I want to know why. These airplanes are not scale, do not need to have fully cowled engines and I don't understand why the designers are doing this. In 3D, is there a benefit? I could imagine the large portion of cowl below the thrust line and ahead of the CG to be beneficial for slow speed knife edge work.

If just done for aesthetic reasons, it seems awfully silly to me! However, given the times...

RE: Inverted Engine mounting
 

daboosailing
If you want to know how to run an engine inverted that is a whole nother subject :D. I think the manufactures figure most people into 3D etc have enough experiance under there belt that it doesn't matter what position the engine is in... I see threads on here about certain models that have a "bad" tank position on them and then I go to the field and see the same planes flying fine inverted with no problems at all.. I am sure there are some bad designs out there (tank position) fortunatly I haven't run across one yet.. If a plane has a nice cowl on it I choose inverted every time... IMHO it looks much better. From what you say the manufacturers must think the same way...

RE: Inverted Engine mounting
 

I have several planes with inverted engines, OS 1.08, Jett, G2300, TT , Saito 100 etc. I lower all my fuel tanks and they all run as good as if they were upright. I learned first hand that mounting the tank at or above the carb line will cause nothing but problems. If you install a fuel tank in the planes original slot and install the engine inverted , your going to have problems. Some engines I run with glow drivers and some I don't but all run very well.

RE: Inverted Engine mounting
 

who knows, maybe the pump and regulator guys are paying someone off, maybe with a free dinner too:D

RE: Inverted Engine mounting
 

Iron Cross, are you a WW1 guy? If so, I are also!

Mark

RE: Inverted Engine mounting
 

WW1 is my favorite... Love those old planes...
Also a MN transplant wanting to get back :D

RE: Inverted Engine mounting
 

Iron Cross, I always thought Northern Calif as a nice place to live! However, MN is good too.

So, the Iron Cross deal must be because of an interest in Germany WW1 aircraft, which isw my interest, too. If you'd like to go direct, my email is [email protected]

RE: Inverted Engine mounting
 

Well, here goes my question....
I'm VERY tempted to get a seagull pc-9 pilatus to replace my decathlon...But my issue is HOW would my saito FA-65 react to running inverted in it??? Any last minute advice before i make a terrible mistake would be apreciated.

Thanks

Dave

RE: Inverted Engine mounting
 

Since most of the 3D arfs i've seen look basically alike any way and it's obvious to most of us that it's a pretty expensive type of fun, why not just fabricate a tank out of brass thats longer and flatter and put 1 in all of you're planes and seal that hole in the firewall up. Then just swap it out when u need to. THERES A TON OF SPACE UP IN THE FRONT OF MOST OF THOSE PLANES ANYWAY. SHEESH!! My heart bleeds for all those picky people with all that time and money on their hands that can't fix a minor tank placement issue. Leave the engines mounted the way they run best and quit whining about the probs you create by being in 3D. Or just go real big and put a 30 oz. electric setup in it.:D
BTW not flaming any 1 in 3D as it looks real cool. Just can't feel the pain of any 1 that mounts an engine upside down then complains when they can't get it to keep running. Or it could be I got up on the wrong side of the bed this morn! ;)

RE: Inverted Engine mounting
 

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If the fuel tank and plumbing are done properly, the engine will run just fine inverted.

Fuel pooling in the head is an old wives tale that is used by the inexperienced and the inept. Running glow engines is science and art, which is why I enjoy it so much. Get the tank height and plumbing right, THEN learn how to start your engine inverted. Or, turn the model upside down in a cradle and start it normally. Inverted has nothing to do with how your engine runs other than in relation to the fuel tank set up once it is running. Honest Injun. I wouldn't lie to you.

RE: Inverted Engine mounting
 

I don’t understand also.

There are no dead stickers (inverted engines) in my fleet. Well … the gas engines are inverted but they don’t count. If the glow engine can’t be side mounted or upright I don’t want the hassle or the airplane. If problems are desired I’ll annoy the female.

The very best engine tuner that I know has repaired at least 10 dead stick landings this past year. Appearance above reliability simply doesn’t seem like a smart approach for me. The upside down fliers always seem to be continuously engine fiddling. And yes someone can make anything run upside down for a little while. Not me, I pass. After all it is an airplane and reliability should be foremost.

It is my opinion and I’m sticking to it. No offense intended for anyone.

Bill

RE: Inverted Engine mounting
 

Well, after some research on inverting a glow engine, i came up with a solution...
Some people on the net call for installing an onboard glow system which consists of a "C' size battery and a microswitch that would basically deliver power to the glow plug at low and idle throttle settings to avoid flameouts....
What do you all think of this simple system? I found some other more expensive ways of running an onboard glow system to improve reliability but they are out of my budget when buying a $140 airplane...

RE: Inverted Engine mounting
 

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If the fuel tank is at an improper elevation to the carb spraybar, the engine will not run properly - upright or inverted. If the tank centerline is even or slightly below the spraybar in the carb, the engine does not need assistance from onboard glow heat.

Buy models that have the tank at the proper height and which are isolated from engine vibration (no part touching the model solidly). If everyone did this, eventually those selling models with no regard for tank height/vibration would either change their designs or go out of business. Problem solved.

Other than improper tank height/vibration, the largest factors causing flame-outs (regardless of engine position) is insufficient break-in time on the engine and improper adjustment of the carb needles (tuning). Following those two factors are use of an improper glow plug, poor fuel choice/prop choice, etc.

Onboard glow heat is a crutch and a band-aid that is used to cover other problems. Eventually, it will bite you in the posterior. At the very least, the extra weight will make the model perform below what it is capable of. Spend some time to get to know your engine and what it needs. It really isn't that complicated.

RE: Inverted Engine mounting
 

Great to know Artisian!!!
Aparently there's a lot of misleading info out on the net....It kinda made sense to me since at idle the fuel leftover (leftover = not properly tuned) would flood the glow plug so adding heat to that plug would keep it hot hence, not flame out....But yeah, i have to give it to ya, tuning is KEY to a smooth operation as well as the other factors...
Besides, a C cell can only last so long before it dies and we are faced with the deadsticking to the ground...LOL!
Still haven't decided on the Seagull Pilatus PC-9 or repairing the injured Seagull decathlon....
Thanks,

Dave