Starting cold Rojett 61

[Richard Speer]

So…. In 2018 I had learned this Rojett 61 pretty well. I could start it one flip. Now I’m flying it again and I’ve forgotten what it was that I did that made it so easy to start. Takes 20 minutes cold. Hot: no problem: 1 choke and it starts one flip. I’ve tried lots of choke, very little choke— from one choke to five or six. No kick. Finally somehow I get it right and it starts. Evidently I don’t know how to read the engine: cannot tell if it’s flooded or dry…

[FLOYD CARTER]

These engines are fitted with a slightly tapered cylinder.  When new, there is considerable "binding" at the top of the stroke.  This represents a lot of drag on the rotating parts.  It is typically hard to start until it has been broken-in with more than usual amount of running.  It is fashionable to mount the engine inverted in "modern" stunters.  That only compounds the starting problem at first. 

My "Pied Piper" stunter has upright RO-JETT 61 mounted upright.  This solves any starting problems!

[Dave_Trible]

Richard they are usually pretty friendly to start but cranky if they've got cold residual oil left in them.  If the engine is inverted you should do as we with pipes-burp it with the engine upright.   When a glob of oil is slathered in the glow plug it will give you a bad time until you clear it.  Flip the plane over where the engine/glow plug is upright.  Give it a shot of fuel from the syringe in the venturi.  ALWAYS BACK FLIP the motor-never crank forward.  Run this prime out a couple times then you should be good for the day.

Dave

[Dave_Trible]

Richard they are usually pretty friendly to start but cranky if they've got cold residual oil left in them.  If the engine is inverted you should do as we with pipes-burp it with the engine upright.   When a glob of oil is slathered in the glow plug it will give you a bad time until you clear it.  Flip the plane over where the engine/glow plug is upright.  Give it a shot of fuel from the syringe in the venturi.  ALWAYS BACK FLIP the motor-never crank forward.  Run this prime out a couple times then you should be good for the day.  I've had it happen a time or two at contests where I've let the airplane sit in the pits a couple hours between flights,  then have a failed start.  I've learned to pull the ship out and re-burp if it has set very long.

Dave

[Richard Speer]

Upright is the key! Then Start inverted Thanks!Thank you!

[Richard Speer]

I did that. Cranked first flip. Same with LA 46. Again Thank you!

[Brett Buck]

So…. In 2018 I had learned this Rojett 61 pretty well. I could start it one flip. Now I’m flying it again and I’ve forgotten what it was that I did that made it so easy to start. Takes 20 minutes cold. Hot: no problem: 1 choke and it starts one flip. I’ve tried lots of choke, very little choke— from one choke to five or six. No kick. Finally somehow I get it right and it starts. Evidently I don’t know how to read the engine: cannot tell if it’s flooded or dry…

    The RO-Jett 61 is one of the few engines you can leave nose-down and still have a chance of starting it without burping it first. But first run of the day, hold the airplane upside down, dribble some fuel in the intake, flip it a bunch of times until you feel it loosen up, attach battery, back-bump. Repeat 2-3 times. Then when you go to fly, you can start it in the normal position on the wheels. Cold 4-6 pulls through with your finger over the venturi, remove finger and immediately flip forward 5-6 times, attach battery, back-bump and should start right off. Hot, one or two pulls, flip a few times to aerate, attach battery, back-bump to start.

     Brett

[Dan McEntee]

    I would suggest that burping any engine when stone cold is a desirable thing to do and I do it with just about every engine I ever run, with the exception of four stroke engines!!! I really like my Saito .56 , but it really took me a long time to become comfortable with the breed, but I did not sell any of my other 2 stroke engines !! I think any two stroke engine with a glow plug That has been idle for more than a day benefits from it.

  Type at you later,
   Dan McEntee

[kevin king]

Strange. All my planes start up with the wheels on the ground with 2 or 3 flips of the prop. All my engines have a tounge muffler though. Never owned a piped engine.

[Brett Buck]

Strange. All my planes start up with the wheels on the ground with 2 or 3 flips of the prop. All my engines have a tounge muffler though. Never owned a piped engine.

   Yes, that is not a problem on muffler engines. On conventional engines, put it nose-down, and the residual oil in the pipe will run back into the engine and tend to load it up. Almost all of them more-or-less require you to do something about that, or it will hydraulic lock. The VFs were really bad about it, always removed the plug to run the oil out. You could turn the airplane upside down and rock the piston back and forth and get enough oil of of it to start without taking out the plug on the PA40 and 61, I haven't run the 75 but it seems to work similarly, except that it almost always kicks the prop loose. The Jett 61 is the only case where you even have a chance of starting it without burping, but I always do anyway.

     Aside from that, these engines are usually absurdly easy to start, to the point you have to be very careful with them any time you have raw fuel anywhere in the engine. Always expect them to start as soon as you drip fuel in, battery or not, particularly when it is hot. At the 93 NATs, I gave up trying to choke my 40VF, it either burped or started every single time with no battery, and at least a few times my PA61 it popped while  was trying to burp it when it just rocked back against compression, once when it was dead cold engine and 50 degrees out!  Always have your holder be ready before you try to choke it for a start.

    Brett

[Howard Rush]

    The RO-Jett 61 is one of the few engines you can leave nose-down and still have a chance of starting it without burping it first. But first run of the day, hold the airplane upside down, dribble some fuel in the intake, flip it a bunch of times until you feel it loosen up, attach battery, back-bump. Repeat 2-3 times. Then when you go to fly, you can start it in the normal position on the wheels. Cold 4-6 pulls through with your finger over the venturi, remove finger and immediately flip forward 5-6 times, attach battery, back-bump and should start right off. Hot, one or two pulls, flip a few times to aerate, attach battery, back-bump to start.

[Motorman]

If you make a thin mixture of lighter fluid and transmission oil then run a couple of primes off after your last flight, you will flush the goopy oil and nitro/alky out of the engine and leave everything nicely coated with atf. Keeps them loose for long term storage too.

[Brian Hampton]

If you make a thin mixture of lighter fluid and transmission oil.....

I use a mix of Mobil Jet Oil II (~18-20%) and methanol then go fly! Also used to prepare an engine for storage after a few minutes of running. Jet oil is the turbine equivalent of an ATF because the oil is contained in the gearbox. I store my models on a rack so they're sitting flat, no chance of oil running into the engine from a pipe.

[kevin king]

Might be off topic but last year i helped launch a piped plane with the wheels down and when he put the glow plug ignitor on the engine, it started by itself. Thankfully his hand wasn't near the prop.

[Brett Buck]

Might be off topic but last year i helped launch a piped plane with the wheels down and when he put the glow plug ignitor on the engine, it started by itself. Thankfully his hand wasn't near the prop.

  Always, always, always, *hold on to the prop when attaching the battery*, precisely because of this. It has nothing to do with the exhaust system, it is the quality of the fit of the cylinder/piston. Also, always have your holder holding on before you start choking it because it might pop or start any time there is fuel in the engine.

     Brett

[GERALD WIMMER]

  Always, always, always, *hold on to the prop when attaching the battery*, precisely because of this. It has nothing to do with the exhaust system, it is the quality of the fit of the cylinder/piston. Also, always have your holder holding on before you start choking it because it might pop or start any time there is fuel in the engine.

     Brett

Hello Am I reading this right or do you mean hold on to the model?
Seems a bit scary but I suppose it won't start that way.
Regards Gerald

[Dan McEntee]

Hello Am I reading this right or do you mean hold on to the model?
Seems a bit scary but I suppose it won't start that way.
Regards Gerald

    If you have a helper, they will be holding the model, but YOU should also hold the prop to keep it from turning over. Put the piston at BDC and wrap you hand around the spinner a prop blade securely, then attach the battery. I have had this happen on OS LA, FP, and Supertigre engines. Not a lot but it CAN happen when conditions are right. Expect the unexpected and be prepared for the engine to fire at any time fuel is present. Another reason to fuel the model on the circle just before flying.

    Type at you later,
    Dan McEntee

[Brett Buck]

Hello Am I reading this right or do you mean hold on to the model?
Seems a bit scary but I suppose it won't start that way.
Regards Gerald

    Have the holder hold on as soon as you start choking/priming, because it might start any time you have fuel and the prop is moving. While the holder is holding, with (as Dan says) the prop off of compression, grab the blade and hold it, attach battery The reason is that this is far and away the most likely instant it will start unexpectedly.

     I will say that, in my case, never once has any of my 3 RO-Jetts popped, kicked, or started unexpectedly with the battery off, or when attaching it. I always have had to do something positive to make it start. But given that I and *many other people* have had very similar setups do exactly that in a wide variety of conditions, you really want to take every effort to avoid safety issues if it were to start unexpectedly. The first time is just as dangerous as any other time.

    Conditions where the odds go up are about what you would think - hot (right down next to the blacktop), choked and aerated, and ready to start normally with battery. My 40VF at the 93 NATs started repeatedly with no battery while I was flipping it to aerate it, not just once or twice, numerous times, and I almost got burned on an official flight because of that. That doesn't preclude other conditions, I once had a similar engine pop first thing in the morning when it was around 50 degrees and still dead cold, in that case, I had primed it as described and aerated it a few times, it just *rocked back against compression* and fired.

    These engines are *extremely safe* in some ways because they are so predictable, but they *are* extremely powerful and almost always spinning extremely sharp propellors at very high speeds, with nearly no built-in safety mechanisms. You do need to take care, develop a routine that encourages good habits.

     Brett

[M Spencer]

Hello Am I reading this right or do you mean hold on to the model?
Seems a bit scary but I suppose it won't start that way.
Regards Gerald

ALLWAYS treat a big nasty cabon fibre prop(ellor) as LIVE , on a ' big nasty engine ' .

the .40 schneurles , they called the HP 40 a ' chain saw engine '  Nuff said . If testing for ' Bump ' a grasp of the blade , like a hand trowl / gardening fork , handbrake ,  etc . A Good Battery - the ' bump ' will try'n start It . sometimes . You then turn the prop forward against compression . If the port blade is near horizontal , a good wack on it has your hand clear before its backfired FWD. across compression , ands runn9ing .
sometimes . Some just use thumb & finger or two , center - at the hub. If it ' catches ' the thing will leap at you , go for the throat , if unrestrained . WHICH IS WHY , on a ' grunter '  , a pistol grip hold , onna da prop ,
will stop it before it starts ,. Sometimes it'll Lurch Your Hand . when checking its primed & hot ( live ) . ' bump ' , for a instant start . Obviously prematurely is inadviseable .

Had a FSR start soft ,  plug not to battery  connected  , tank empty , twice in sucession . As in it turned itself over a second or two , on nuthing but fumes . But if ' fueled ' might have done anyhing .
This was AFTEr a flight  , so obviously warm .
A bloke starting a 5 Hp Corsair with a 24 inch carbon prop in whangarei , doing a demo at work , second time , distraced as the secretary had asked to see it , the holder ( not a aeromodellor ) didnt .
and Id Previously been told that day by someone that ' He had burnt his fingers up to his elbow ' . this bloke had too - Parts off two fingers , scars ( meaty ones ) up the outside of his arm , to the elbow .
and eight weeks off work .

He hadnt enyoyed the first six .

Anything past an old baffled loop scavenged 35 , can get ya , real good . Even a Old OS 30 can go to the bone , when the flyer pulls the handle sharp ,
with a  hand on inner wing  .

Pitman should scan field before release . Pilots ' In Control ' of PIT before that . HE should scan vicinity ' all clear ' and no irrelevant poisons near at hand .

I guess you could say ' the pilots the Captain . ( and will be obeyed ) unless he has his back to the pitman ( going out to the handle ) . but a Good Pitman will see he hasnt made a blue .
As in he will have SEEN FOR HIMSELF , that theiers no forign obstacles in the flightpath , Before Lauch . As he is the one whos done it , if he lets it go into someone .
And the pilot and the pitman should see that ' someone ' isnt there , in the first place ,  who has no need to be .



Then theres ties , hats , pens in pocket , etc . can lead to a chain reaction , if over in front of the prop . can get nasty real quickly .

[Steve Helmick]

ALLWAYS treat a big nasty cabon fibre prop(ellor) as LIVE , on a ' big nasty engine ' .

the .40 schneurles , they called the HP 40 a ' chain saw engine '  Nuff said . If testing for ' Bump ' a grasp of the blade , like a hand trowl / gardening fork , handbrake ,  etc . A Good Battery - the ' bump ' will try'n start It . sometimes . You then turn the prop forward against compression . If the port blade is near horizontal , a good wack on it has your hand clear before its backfired FWD. across compression , ands runn9ing .
sometimes . Some just use thumb & finger or two , center - at the hub. If it ' catches ' the thing will leap at you , go for the throat , if unrestrained . WHICH IS WHY , on a ' grunter '  , a pistol grip hold , onna da prop ,
will stop it before it starts ,. Sometimes it'll Lurch Your Hand . when checking its primed & hot ( live ) . ' bump ' , for a instant start . Obviously prematurely is inadviseable .

Had a FSR start soft ,  plug not to battery  connected  , tank empty , twice in sucession . As in it turned itself over a second or two , on nuthing but fumes . But if ' fueled ' might have done anyhing .
This was AFTEr a flight  , so obviously warm .
A bloke starting a 5 Hp Corsair with a 24 inch carbon prop in whangarei , doing a demo at work , second time , distraced as the secretary had asked to see it , the holder ( not a aeromodellor ) didnt .
and Id Previously been told that day by someone that ' He had burnt his fingers up to his elbow ' . this bloke had too - Parts off two fingers , scars ( meaty ones ) up the outside of his arm , to the elbow .
and eight weeks off work .

He hadnt enyoyed the first six .

Anything past an old baffled loop scavenged 35 , can get ya , real good . Even a Old OS 30 can go to the bone , when the flyer pulls the handle sharp ,
with a  hand on inner wing  .

Pitman should scan field before release . Pilots ' In Control ' of PIT before that . HE should scan vicinity ' all clear ' and no irrelevant poisons near at hand .

I guess you could say ' the pilots the Captain . ( and will be obeyed ) unless he has his back to the pitman ( going out to the handle ) . but a Good Pitman will see he hasnt made a blue .
As in he will have SEEN FOR HIMSELF , that theiers no forign obstacles in the flightpath , Before Lauch . As he is the one whos done it , if he lets it go into someone .
And the pilot and the pitman should see that ' someone ' isnt there , in the first place ,  who has no need to be .



Then theres ties , hats , pens in pocket , etc . can lead to a chain reaction , if over in front of the prop . can get nasty real quickly .

I was pretty sure that Spitfires didn't have carbon fiber propellers, but I'm happy to learn new things.  Steve

[M Spencer]

Was a Corsair that tried to take the guys arm off . Sans wings . Bloke from his work ' holding it ' when he thottled it up to ' impress ' the office bird . 5 Hp. zenoha or suchlike on a 24 inch three blade C F prop .

Tho a un modellor got a FP 40 to chew up his fingers hospitabley on a 11 in master  C F reinorced nylon. Reached thru prop to adjust the needle . Think that was worth two weeks holiday . If thats what youd call it .

Spit Props are Hydrgaminium or compregnol or oweva yer spellsit . Which is compressed resin impregnated wood , perhaps . https://www.tandfonline.com/doi/full/10.1080/17480272.2012.751935

was pretty sure that Spitfires didn't have carbon fiber propellers, but I'm happy to learn new things.  Steve

My one does ! or can , sometimes .   

Apparently , the Griffon engined Shakelton , has alloy props , which Hinton used on His R B 51 . if thats close nough . always been illegal on model engines . Supose the Griffon wouldnt fit .