Back Flipping

I have heard of something called “Back Flipping” as another method to hand start an engine.
What is this?
In what circumstances would I use it?
Any benefits?

you 'back flip' whenever the engine is flooded... BEN

Actually you stand in front of the engine and do a back flip. If you land on your feet the engine will start on the next flip. If you fall on you keester it won't start until next Tuesday.

I hope this helps.

>Actually you stand in front of the engine and do a back flip. If you land on your feet the engine will start on the next flip. If you fall on you keester it won't start until next Tuesday.
>I hope this helps.

Do you suppose we can perfect a method where some of us old guys who are too doggone old to do a back flip can just jump up and down a few times and get the "next flip" start?

>I have heard of something called “Back Flipping” as another
>method to hand start an engine.
>What is this?
>In what circumstances would I use it?
>Any benefits?
>
>Chris

Hi Chris,

"Back flipping" is proably the method of choice to start the current crop of larger more powerful two stroke engines. It is less popular for the big four strokes, most of which are started with electric starters for no other reason than the consistency factor.

Back flipping, how it works:

The system was developed by combat flyers who were tired of getting their knuckles rapped by tiny props on very powerful engines. The wanted a system where their fingers wouldn't be in the line of fire when combustion took place. The bottom line was they determined that a large percentage of the "whacks" they took came when the mixture was too rich and the engine backfired and took a chunk out of the finger that was trying to pull the piston through the ignition process. Usually, the finger lost the battle.

Some wise guy with sore fingers decided that if the engine wanted to backfire, why not let it start itself by doing so! TaDa the back flip was invented.

This wise fellow decided that if he flipped the prop backwards and "bounced" it off of compression that the overrich mixture would ignite and cause the engine to backfire off in the "other direction" ... which, in this case turns out to be forward. Turns out it works like a charm and, when the proper technique is used you can actually start these super critters with merely a flick of the spinner...although a good bop of the prop is a more sure fire bet.

If you get a chance to watch just about any of the hot shot stunt guys (other than the four strokers, as I mentioned) you'll almost certainly see the technique in action.

Here's how to do it:

Because the method depends on an excessively rich mixture to induce the backfire you need to choke the engine enough to get it wet...pretty much enough fuel in it that you'l be unlikely to even attempt to flip it through compression. Experience will teach you what is right for your engine. For instance, my P.A. .61 requires three flipped chokes for the first start of the day or after a significant cooling down period. If we are flying back to back flights, our preferred method, the engine will usually fire right up without a choke at all on subsequent flights.

Once the choking is complete, flip the prop through compression three or four more times to insure good atomization and be sure you haven't overdone it and created a hydraulic lock from too much fuel. Once again, experience will soon tell you exactly who much your engine requires and, once this is determined, it will pretty much work the same every time.

Now, hook up your battery and, surprisingly, don't turn the engine over to feel a bump as you'd normally do. Doing so just wastes the mixture you've worked to get just right.

Instead, bring the prop up lightly against compression exactly as you would if you intended to flip it through. Now give the prop a decent whack backward rotating the blades through a little less than half a revolution and forcing just enough compression in the backwards direction to cause the backfire to occur.

Done properly your fingers will be well out of the way before ignition takes place. When it does fire it will do so in the forward, desired, direction and for all intents and purposes start itself.

One caveat (shortcoming). The system works "best" on nice free ball bearing engines with little drag between compression. Because the method depends on the momentum of the flicked prop to achieve the compression necessary for combustion to occur, a draggy cold soaked castor infested Fox is a poor candidate for the system. Modern AAC/ABC non ball bearing engines like the FPs and (probably, I've no personal experience) the LAs will work fine with the system once the congealed oil in the bushing main bearing is loosened up with fresh fuel.

Chris, this is THE technique for starting the modern high powered two strokes with the utmost consistency and safety. I encourage you to learn the technique. Hope this note helps.

Good description!

I disagree with your excepting 4 stroke engines. I have a Saito 45 on a profile that I have started using a backflip for years. The key is that the engine has to be really wet, I know my engine is ready when I have a large stream of fuel shoot out the exhaust. 90% of the time I get a first flip start. My engine has mild timing, may not work with more aggresive timing as some engines have.

Ted,

>>Chris, this is THE technique for starting the modern high powered two strokes with the utmost consistency and safety.<<

A starter is pretty consistent and safe too.

Strangely, the first flight of the day, I can always hand start my Saito 56 with pretty much the process you outline. Have to get it pretty wet, but it works every time. After the engine is hot, I've never been able to get it hand started. And I've tried a lot of different approaches.

LAST EDITED ON Oct-02-03 AT 04:11 PM (CDT)
 
>Done properly your fingers will be well out of the way
>before ignition takes place. When it does fire it will do
>so in the forward, desired, direction and for all intents
>and purposes start itself.
>
>

>Chris, this is THE technique for starting the modern high
>powered two strokes with the utmost consistency and safety.
>I encourage you to learn the technique. Hope this note
>helps.
>
>Ted Fancher

Ted,

does it beat (as far as safety is concerned) the old chicken stick?

I am now a "chicken stick convert".

A "revelation" came to me after gettin a whack in my fingers delivered magistrally by a CB.46 stunt I'm breakin in.

I thought: "why put my precious fingers (I need all of them to play my horns) in the line of an unforgiving prop if I can put someting else, like a chicken stick?

Does the chicken stick have any drawbacks?

I'm all ears...

In Christ,

>Does the chicken stick have any drawbacks?
>

They scare the heck out of me. The possibility of getting them caught up in the works, and having them either sling out at high speed, break the prop, or get caught and drag you into the prop always seems too high. I just don't think it's possible to control them as well as your fingers, and given safe practices, like back-flipping, it's just not necessary.

But that's just my opinion.

LAST EDITED ON Oct-06-03 AT 03:57 AM (CDT)
 
For back-flipping, I don't think there's any danger of any of this. Yeah, I suppose one could mistakenly stick it in a whirling prop, I'd rather stick the stick in a whirling prop than my finger, high speed slinging or not.

For regular flipping, a protected finger might be better. Flipping with a chicken stick does seem awkward.

I make my own, using dowel and tygon tubing from the hardware store. I leave a short piece of Tygon overhanging the dowel at the end - very handy for stopping backward-sputtering engines.

>
>>Does the chicken stick have any drawbacks?
>>
>
> They scare the heck out of me. The possibility of getting
>them caught up in the works, and having them either sling
>out at high speed,

This danger is the same as the one of a prop being thrown. It can be avoided by keeping cclear fromn the prop arc.

>break the prop,

Still beats breakinbg a finger.

>or get caught and drag you into the prop always seems too high.

Unless you glue the chicken to your hand this is a far, far fetched possibility.

>I just don't think it's possible to control them as well as your >fingers, and given safe practices, like back-flipping, it's just not
>necessary.

Has it occured to you it's just a question of getting used to it?

> But that's just my opinion.
>
> Brett

You can make these my words also, Brett. Please, don't allow yourself to even THINK I'm trying to play the wise guy, or that I don't have the utmost respect for your knowledge! It's not w/out a reason I have almost all your writings saved in my computer.

In Christ,

>>
>>>Does the chicken stick have any drawbacks?
>>>
>>
>> They scare the heck out of me. The possibility of getting
>>them caught up in the works, and having them either sling
>>out at high speed,
>
>This danger is the same as the one of a prop being
>thrown. It can be avoided by keeping cclear fromn the prop
>arc.
>
>>break the prop,
>
>Still beats breakinbg a finger.
,
<>

By all means, use whatever makes you most comfortable. I contend that you run a chance of having accidents that you wouldn't otherwise have, but that's just my opinion.

But, you DID ask....

Brett

I have an OS .40FP on my model. I always put my finger over the venturi opening and pull the prop through four rotations, remove my finger from the ventiri and flip the prop four times to atomize the fuel. I connect the battery and "back flip" the prop to start the engine. I "back flip" to prevent my knuckles from being hit by the prop. This is a starting procedure I learned from Bob Whitely because the carbon fiber props can easily slice the fingers and some engines are known to "start" faster then the fingers or a chicken stick can clear the prop arc. Hope this helps.

Lucky

Lucky Pyatt
Tucson Arizona

This is
>a starting procedure I learned from Bob Whitely because the
>carbon fiber props can easily slice the fingers and some
>engines are known to "start" faster then the fingers or a
>chicken stick can clear the prop arc.

Aha! Another very good reason that back flipping is the method of choice with the super dooper carbon props. By back flipping you are smacking the leading edge, not the trailing edge. The trailing can slice 1" heater hose right in two. Bob G. has pieces of his heater hose flying off all the time, but the most damage definately comes from the trailing edge (that is off course unless you use the PW sharp leading edge).

The truly "hip" way to start the big ABC's is the "spinner back flip". It is held in high regard in Dallas.

To start a Nelson combat special, and perhaps other engines,
the common approach is to flip it backwards. Assume you're
standing in front of the plane and your buddy is holding it,
and everything is fueled, primed, and ready to go...
Turn the prop counter-clockwise until the you're up against
the compression (just like a normal start).
Then flip vigorously (wack it!) backwards (clockwise).
The prop will spin around about 180 degrees, then bounce
off the compression and the engine will start. Hopefully.

There's a big safety advantage in that your hand has more
time to get out of the way (while the prop is doing that
180 degree spin) during the follow-through of your
vigorous wack. If you practice enough, you'll find that the engine
c\starts reliably too, first flip, every time.

Ron B.
F4Fguy

It is a way of clearing a flood,but it's also a very effective way of starting under normal conditions.The main requirement is an engine in excellent condition and well broken in.Here's how it works:

(1)Prepare to start in the normal manner,i.e.engine primed,& ready.
(2)Holding the prop,turn the prop until it"bumps"(fires while pulling it toward top center)one time.
(3)Turn the prop back off compression just until you feel compression start on the reverse rotation.
(4)Bump the prop sharply in the clockwise direction (note:Do not "flip" it through TDC).
(5)The engine will fire on the up stroke and turn the prop counter-clockwise,starting the engine.

Actually ,using this technique,you get a much stronger/faster CCW flip from the engine than you can do by hand.This works especially well on inverted engines.

I find that any time that an engine is kicking back against your finger sufficiently to cause difficulty flipping it through in the normal direction, it is a candidate for a good healthy back flip as pointed out above regardless of whether or not it is bushing or plain bearing, AAC, ABC, or steel/iron pistonand liner.
I also find that the larger the engine, the easier it is to get a good back-flip start. I have NEVER been able to start a 1/2 A by back flipping. I have started good 15s on up though.
Bigiron

LAST EDITED ON Oct-03-03 AT 02:48 AM (CDT)
 
This seems to work especially well on Schnuerle ported engines. I've used it successfully with engines as small as a .15. Most people don't hit the prop with bare fingers - most use a starting glove, I use a chicken stick, a friend uses a piece of car heater hose. A good hard whack is what is needed, not a timid flip, so it also requres a sturdy prop (and one with enough mass to get a good bounce off the compression). I've broken wooden props doing this (those really thin Top Flite pylon racing props I bought real cheap). This is probably the main reason why people don't use this technique to start F2D engines, which use those thin, toothpick-like props.

As Ted mentions, you need a healthy prime for this to work. For Combat, we flip the plane over, close the exhaust port, fill the opening with fuel (it is held there by the flange and the piston), and then open the port to let the fuel into the cylinder. That's a BIG prime!

Excellent narrative Ted. Your explaination is very informative and detailed.

The following is how I "backflip" the OSLA25 stock with the Super Tiger Needle valve on stock venturi.

Prime the engine with two flips (first start of the day), flip the prop 5-6 times to loosen up the engine, atomize the fuel Grab the spinner with the thumb and first two fingers and rotate quickly back and forth several times for (1) additional amotization and distribution of the fuel and (2) to limber up my arthritic fingers and practice quick and powerful spins with the prop spinner, Attach the power to the glow plug and exercise a vigerous back spin of the spinner. Usually works the first time and often the second time.

When the engine is warm only one prime is necessary.

The other day I flew six flights with seven flips. Pretty hard to beat and pretty impressive for onlookers.

Bob Smiley
A Lancair 360 bulder/pilot trying to be a modeler

...I have NEVER been able to start a 1/2 A by back flipping...
> Bigiron

Hah! I can tell you never had a Babe Bee before the spring starters were added.

George!!! I try to forget "unpleasant" memories. Yes I have started the Baby Bees by cranking them backward. BUT not by the methods listed above. I would just try yo flip them through compression as if trying to start them to run backwards. Yes, they would often start and run in the correct direction. But just as often they would go ahead and start and run backwards.
Really, I was just speaking of the Tee Dees and AMEs and VAs. the higher performance little buggers.
Bigiron

Hey guys thanks! I can see this method is not as rare as I thought. Be assured, this will be the “Go-To” method for me now.

My fingers thank all of you.
Chris

Flipping any of the Cox engines up through the 15 Special is an exercise in futility. If there is no starter spring, give a healthy head prime, then rotate the prop backwards until it is vertical. Connect a 2-volt battery, and hit it forward with your gloved finger. You will usualy get a one-hit start, and with the reeds you will almost always get it running the right direction.

I don't care for chicken sticks. However, I am a believer in a heavy leather glove. I have lately found that an electric starter has its uses.