Engine running Backwards?
 

Hello all, Well it's a nice day here in Indiana so I think I head to the AMA site today and fly. I usually use a starter to start my planes however the battery was down after the winter and it just wouldn't charge. I am waiting on my new battery from Tower. Anyways, I want to fly so I went out and tried to start my engine with the chicken stick. To my suprise she turned over on the second throw! I am flipping the prop the same way my spinner spins, to the left looking at the model. As I I tried to increase throttle she died but I noticed she started to roll backwards an inch or so as I increased. I did this again with the same result. Only for a few seconds. I then tried to flip the prop to the right and she turned over nicely but this time she was going forward. The prop is on right as I've flown this plane last year, Can my engine run backwards by flipping it to the left? Is flipping to the right ok if it gets the engine going to the left? Anyone else have this problem? Will it be like this after 200 flights on this model? Thanks for the help!

RE: Engine running Backwards?
 

Yes, sometimes it will fire up backwards. I've only had that happen to me a couple of times in a couple of hundred flights, but I always use an electric starter. Using a stick, you are probably going to see this happen more frequently than with a starter. I believe it is just bouncing back due to compression, and happens to fire up occasionally in the reverse direction.

RE: Engine running Backwards?
 

It can happen.

Are you getting a clean transition from idle to WOT? Sometimes that is a symptom of the low end being rich.

It happened on a helicopter of mine once, the tail rotor spun up but the main rotor just sat there, I was quite dismayed until I figured out what happened.

RE: Engine running Backwards?
 

That happens to me at times using a chicken stick. I usually increase throttle til the engine begins to sputter. Just before it dies down I blip the throttle down to idle and slowly give more throttle. The engine usually recovers spinning the correct direction without problems. It may take a few times to get the timing down, but it's not hard to do.

RE: Engine running Backwards?
 

The engine will fire and run backwards if it's flooded. This happens to a lot of pilots in that they over prime the engine. And then it will start and run backwards. Start experimenting with priming less until you find how much to prime it so that the engine still starts but doesn't start backwards.

When your engine does start backwards there are a few things to do. Many pilots will "blip" the throttle stick which can sometimes pop the engine into running properly. Or simply close the throttle until the engine dies and then restart it. It may take a couple of tries until you burn off enough excess fuel for it to run properly.

Ken

RE: Engine running Backwards?
 

Thanks guys, I'll try those things when I'm out!

RE: Engine running Backwards?
 

My OS 75 AX starts up backwards a lot of times after it has warmed up (after the first flight). But, part of that is my fault because this engine starts so easily, that I just flip the prop one time and it will start. Sometimes, backwards, but, as Ken said, I just pop the throttle open and closed real quick and it usually just makes a little popping noise and then runs forwards. Doesn't seem to be a big deal.

My OS 1.20 AX, though, I actually tap the prop hard in the reverse direction with the chicken stick and it will immediately start up running forward.

RE: Engine running Backwards?
 

mine do that when i try and start them with a chicken stick when they are cold, they are usually running quite rich and they do start up in reverse, but open the throttle slightly until it kicks over into forward rotation, or quickly open it and then close it as suggested above

RE: Engine running Backwards?
 

Another trick I use when the engine starts backwards is to pinch the fuel line. This will cut off the fuel supply and burn off the excess fuel. Listen carefully, and you'll hear the engine blip and then start running forward. Works about 90 percent of the time.

Brad

RE: Engine running Backwards?
 

What RCKen said:
Some engines do this more than others due to the engine timing. You should never just prime or choke an engine and then start flipping or bumping with the starter. This is the best way to throw off the spinner and prop when it kicks back.

For a two stroke glow:

Instead, after it is "primed", hook up the glow plug and pull the engine through compression by hand. If it kicks, it is flooded, keep pulling it through compression until it doesn't. Quite often it will start bumping every other turn through compression. If flipping with a chicken stick, flip right after the bump, or with a starter.

RE: Engine running Backwards?
 

I'm not trying to start an arguement here, but IMHO you sould never touch the prop once the glow plug is hot. The reason for this is because it's very easy for it to pop, kick back, or even actually start, and if the person isn't ready for it or doesn't have a good hold on the prop it could do some very serious damage to the hand. I teach all of my students that after the glow plug ignitor is attached the prop should be treated just as if it was running as it's possible to harm.

Ken

RE: Engine running Backwards?
 

Ken, surely it is much safer to hold the prop and pull the engine through compression than have it backfire and throw the entire prop and spinner. When the engine has the exhaust open, it can not kick regardless of the mixture with the glow plug driver on the engine.

I base this on more than 40 years of experience of starting these beasts.

RE: Engine running Backwards?
 

Highplains,
Actually, I think that both of them are dangerous. I appreaciate the years of experience that you've had, but I still stand behind my thoughts that the prop shouldn't be turned over with the glow driver attached. It's dangerous advice to give to people starting out in the hobby. While you know from your experience that you should have a good grip on the prop from your experience, beginners may not have that experience to rely on or may not realize how tight to hold the prop. And that's all it takes for the prop to kick over and cut their hand. IMHO it's just good saftey procedures to treat an engine with an ignitor attached as running. Good safety procedures such as this are what keeps a pilot from getting hurt from a running engine.

Ken

RE: Engine running Backwards?
 

It should also be pointed out that glow engines can start without the ignitor being connected. The glow plug acts as a catalysis to react with the methanol in the fuel.

Part of the trouble with our sport has been it's rapid growth. So quite often we have people showing people the ropes without all that much experience. Back when people actually had to build their airplanes, they spent a lot of time watching others fly and helping out which gave rise to a better training and sharing of knowledge. It generally takes two to fly control line for instance. Starters were rare 40 years ago, so starting by hand was routine.

I learned from modelers that started flying models in the 40's. So I accept that there is much less experience, and a general dumbing down of relevant knowledge. It's that way everywhere in all aspects of life for the last 50 years.

RE: Engine running Backwards?
 

just another not while we are on the subject of safety. if it is running backward and you open the throttle, remember that the plane will BACK UP! just something to remember. ask me how i know this.

RE: Engine running Backwards?
 

on my OS 1.2 surpass it actually tells you in the manual, yea....who reads those, that when starting by hand to flip the engine the oposite of it's normal rotation.......works like a champ. if you try to hand start it in the normal running direction it starts backwards everytime.

RE: Engine running Backwards?
 

Thanks everyone for your input and I know now at least I'm not the only one to encounter this. I didn't want this to turn into a safety forum, I know how to keep my fingers. I have a few things to get me out of this jam next time though. Thanks for the support so quickly![8D]

RE: Engine running Backwards?
 

I'm in agreement with RCKen. After you put the igniter on--treat it like it can cut your hand off. It's "HOT" now and can hurt you.

I also agree that this condition is mostly from over-priming. A flooded engine will be much more likely to start backwards. I use a chicken stick 90% of the time. I don't grab the electric starter unless it's really cold outside.

RE: Engine running Backwards?
 

Ok...definitely confused now. Which way is the prop supposed to spin when starring at the nose of the plane? :eek:

RE: Engine running Backwards?
 

Counter-clockwise if looking at it from the front.

If you were sitting in the cockpit, it should be spinning clockwise.

Edit:
I don't recommend sitting in the cockpit. Balsa is too weak to support most of us. My butt is getting larger in my middle age. It wouldn't fit if I tried. [sm=lol.gif]

RE: Engine running Backwards?
 

Bump starting does work quite well for both 2 and 4 stroke. I usually do it on bigger engines by snapping the spinner against compression with the throttle at low to 1/4 open. But don't recommend it to rank beginners.

RE: Engine running Backwards?
 

If your engine starts running backward don't panic. This isn't a bad thing, just not a good thing. Merely "a thing". Let is run for a bit so the engine will warm up and any EXCESS fuel (from being too rich) will burn off. Then reverse the engine by your favorite method. If the engine stops it will restart easily in the correct direction.

RE: Engine running Backwards?
 

I've seen a glow engine start without the battery attached. I have had them start (one time) when the battery is attached, before flipping. So I hold the prop firmly while I attach the battery. If you are going to hold the prop, assume the engine is going to fire and have a good firm hold. Probably it won't fire, but better sort of safe than really sorry. I do the turn over for the bump. then flip forward. If it is a hard bump, as in flooded, then I hit the prop backwards. I recommend a good leather glove if hand starting. . A piece of radiator hose makes a good chicken stick.

RE: Engine running Backwards?
 

The G21 .35 Super Tigre is/was notorious for wanting to start backwards when flipped counterclockwise.

RE: Engine running Backwards?
 

High Plains, all your posts here reflect on a person with great knowledge concerning the care and feeding of the 2 stroke engine.
As one that started with ignition, and in short-order over to glow, when there were no "starters" other than a few big wheeled units used mostly by CL Speed fliers, I also learned the "bump and flip" technique. That was almost mandatory in my CL Stunt days when the 1 minute rule, signal to start to being airborne, was in effect for the 5 points.

Your input is very refreshing to myself where in today's world and with most fliers of 20 years or less experience they simply expect the Glow engine to be a plug and play operation. I get a lot of startled stares when I choke, turn-over using pull-through, feel a "bump", flip, and the engine is running.

Unfortunately, today's modeler has no time and no desire to learn the basics, especially if it is not in the instruction booklet. [:o]

Great Posts, HP.

BTW, I have experienced both the running-backward start, especially with cold high compression racing engines, and a few starts without the battery connected. Nothing is 100% certain. Always use care and awareness.

RE: Engine running Backwards?
 

agreeing with the comments about flipping the prop with the glow circuit active.

its common sense, once the ignition circuit is live the engine has the potential to start, so to have a prop in your hand whilst cranking it over isnt the best idea

you wouldnt hold the blade of a blender whilst you turned it on at the wall would you?

RE: Engine running Backwards?
 

When my engines start backwards, I slowly close the throttle trim, as the engine idles slower and slower, it sometimes will suddenly reverse. This will be accompanied by a sudden jump in idle rpm because the intake timing is correct for forward rotation and incorrect for reverse rotation.

RE: Engine running Backwards?
 

I'm guessing due to some of the comments on this thread, that some of you really don't understand how a 2-cycle engine works. In particular, comments about what going to happen when you hook up the glow plug. As I posted earlier:
That means that there is no way the engine will jump, bump, move, or start just because you hooked up the battery, regardless of the amount of fuel present. You may have a small fire going on inside the exhaust and muffler, but that is all. Before mufflers were common, you often caught the grass and model on fire from excess fuel, and since it was mostly alcohol your first indication of the fire would be the covering burning away or the grass burning under the exhaust. (Methanol burns without visible flame).

Now there are several conditions that can cause serious problems. It is sometimes possible to fill the engine crankcase with fuel, due to tank position, engine installation, or careless handling (carrying the model around nose low with a full tank is a no-no). What happens when the starter is applied is hydraulic lock, which can bend the rod inside the engine and/or spin the prop and spinner off and throw them some distance depending on how hot a starter set-up you are using. Many of our props are rather sharp and it’s a bit like closing your eyes and throwing a knife over your shoulder. So before you grab the starter, pull the engine through a couple of turns and stop with the exhaust port open.

Now with a primed engine, it is quite possible to have too much fuel present in the cylinder. So when the starter is applied instead of turning the engine over smoothly, the mixture fires too soon and kicks back against the momentum of the starter/prop/spinner. Impulse is one of the more interesting functions in engineering and mathematics. So the shock wave from the cylinder is enough to cause the prop nut to spin right off the threads, and again an uncontrolled sharp object can go flying though the air. Fortunately, the most common result is having to disconnect the battery and go get a screwdriver and prop wrench.

But none of these problems need trouble you if you just learn to firmly grab hold of the prop and pull it though compression until the hard bumps are gone. As long as the engine is not left in compression, it will just sit there and wait for you to start with your starter. When you go start it, it will never throw or loosen the prop again.

RE: Engine running Backwards?
 

HighPlains, I have read all the post and have a couple questions. First I understand your method but might be something best taught to a beginner and not to just practice on your own until one sees how it is properly done. Perhaps a video would be great. My question is a beginner question, About how many revolutions should it take before the hard bumps are gone and also can this step be achieved with-out the glow igniter attached?

I would be interested in trying this. I was taught to start with my finger and on my Evolution .46 this is no prob. Its prime 3 to 4 pumps then a finger pop forward or backward on the prop and off it goes. Now on my new JBA .56 this is a diffrent beast. I tried the same steps but primed 6 pumps for a richer start, did the finger pop and snap. It started so quick I about dropped a, well lets say it was fast. It sort of startled me that it was that much more powerfull than the .46 so I went to the electric starter. This motor sure is touchy/aggressive and would much rather use a smarter approach. I don't really like the way the electric starter seem to slam start the motor.

RE: Engine running Backwards?
 

I too learned to pull an engine through by grasping the prop with my hand waiting for the "bump" unless we primed directly into the open exhaust port like is common with the Cox engines. This is how it was done 35 years ago when electric starters where not prevalent (I still have the one I made from a 1958 Oldsmobile power seat motor), and while I feel comfortable doing it today I don't show my students how to do this (but I also teach them how to start the plane using a starting stand or tail restraint, not holding onto the fuselage with one hand and flipping the prop with the other). I also make sure the prop is well sanded so I don't cut my hand, have a very tight grasp on the prop and wont do this on anything larger than a .60.

For starting and running backwards, my Evolution .61 was doing this today and would actually start to accelerate over 1/3 throttle and keep running without reversing to the correct direction [X(]. Since this is a new engine (now has 10 flights on it) and with the temperature swings we are having right now I know the engine is a bit rich on both the high end and idle. It starts and runs the right way by flipping it backwards using a chicken stick while almost every forward flip caused it to run backwards [>:]. I have also found this particular engine requires about 13 choke flips with my finger over the carb after fuel starts to move through the fuel line to start when starting for the first flight of the day (probably flushing out the afterrun oil), and about 5 choke flips after its been run that day - guess just a quirk of this engine and it not being completely worn in yet.

Hogflyer

RE: Engine running Backwards?
 

This "bump" felt by turning over the prop is just that, a bump. It's not a flesh tearing off-to-the-hospital KABOOM. Just hold the prop firmly and turn it into compression. It'll only happen if you've primed the engine and then got at least some of that prime up into the combustion chamber. If the crankcase is full of fuel but none up top then it won't go bump. This is the art of priming, finding out how little fuel can be drawn into the crankcase and then spread around inside the cylinder by a few quick flicks. Of course the priming and spreading is done first and then the plug heated. Usually an engine will only bump the first time because anything combustible gets burned but if you continue turning the prop fairly fast it might send a little more vapour up into the cylinder ready to bump again but you're better off just giving the prop a flick because the engine has told you it's ready to start. If you don't want to flick then one turn of the prop with an electric starter should have it running.

All of this is pretty much standard practise in CL stunt where one flick starts are the norm and most engines are at least a .60 size (and inverted as well).

You won't get the bump without the glow ignitor attached although I've heard stories (from reputable people) of glow engines firing with a cold plug. Never in my 50 years of turning/flicking over an engine have I ever felt even the slightest bump if the plug's not lit but it's something to keep in mind anyway.

RE: Engine running Backwards?
 

Lots of good safety info here. One habit I've gotten into is find compression on the back stroke then turn spinner counter clockwise about 1/4 turn to get piston away from compression. Make sure transmitter and reciever are turned on and throttle turned down to idle, now attach glow power while keeping clear of prop.
I also now wear a glove on my right hand after getting wacked once and cut once last year. Seems like there is always something to learn or a procedure to improve upon. ;)

RE: Engine running Backwards?
 

Bump

RE: Engine running Backwards?
 

I had forgotten how long ago we had this discussion. Still relevent information on how to start an engine.

RE: Engine running Backwards?
 

Twice in some 40+ years, I have had a glow engine start when I connected the glo plug battery. As a result, I ALWAYS hold on the prop very tightly when I attach the glow plug battery in case it wants to fire.

RE: Engine running Backwards?
 

My Tower .46 engine will almost always starts backwards when I use a chicken stick. I just let it run for 10-20 seconds and it quickly corrects itself.

RE: Engine running Backwards?
 

Yes do not worry about this I have had this happen to my rc cars. I believe it happens after the engine has been sitting for awhile.