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RE: PROFI RAMBLER .049 - 12/4/2012 12:04 AM   
MJD



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Status: offline 		No, different company. But Thales eventually bought Racal. Racal and Decca were British in origin. You're more my age then.. my dad would be 95 now if he were still around.

Back to 1/2A's.. all this talk makes me think a 1/2A proto might be fun to put together over the winter, even if I do end up playing by myself. I have two VA's, a KK Tee Dee, not the hottest contenders around but good for some fun anyways. The Profi goes in RC though.

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RE: PROFI RAMBLER .049 - 12/4/2012 12:46 AM   
aspeed


 

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Status: offline 		I never tried my VA or Norvels in a proto, but my TD went about 78mph standing start, and 82 on a speed run.  That was on a fair bit of nitro with a bladder and a KK needle and a TD head that was shaved a bit.

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RE: PROFI RAMBLER .049 - 12/11/2012 9:43 PM   
MJD



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Status: offline 		OMG, what a letdown! The engine was mailed on about the 27th of Nov. 10-14 days typical to up here. We have a central mail box in the village, and like a kid waiting for a new comic book, every day I open the box hoping it has arrived and then mope away with more bills and junk mail. So today, I open the box and hooray!! - there is the parcel box key with the red tag. This lets me open the parcel box and retrieve my package. So I stabbed the key in, and frantically turned and turned and.. click, jam, arrrggghhh! They had left the wrong key and I can't get the %#&%$@* box open.

Now I have to wait until tomorrow to get my new Profi and my wife will have to put up with me pouting and fidgeting all evening.



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RE: PROFI RAMBLER .049 - 12/11/2012 10:01 PM   
forsakenrider


 

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Status: online 		Woo!! im excited for you! but I know how it is. I get those post slips, tomorrow after 1!!! what do you mean tomorrow after 1!!!! haha.

Pictures to come I hope

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RE: PROFI RAMBLER .049 - 12/12/2012 7:08 AM   
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RE: PROFI RAMBLER .049 - 12/13/2012 12:06 AM   
Max_Power



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Status: offline 		So, have you pried that mailbox open yet? I can't wait to see your report on this little screamer!

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RE: PROFI RAMBLER .049 - 12/13/2012 12:51 AM   
MJD



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Status: offline 		I resisted the urge to blow off the hinges, and today the right key was sitting there..

I like the prop nut much better than on the .061 which is a hex nut affair - functional but butt ugly. The other thing I checked right away was the length of the prop stud, and the length on this .049 is better suited to the thicker hubs on higher pitch props. The .061 is too short for my liking, but it is fine with fine pitch composite combat or FF props.

I'll measure it up and draw it in CAD over the next few days. And if weather and busy weekends permit I'll spark it up on an APC 4.2x4 for comparison.

Negatives? My .061 came with a turbo plug and a Nelson plug head, and for $50 less than the .049. But Profi hasn't dried up and blown away yet so "whatever", they're premium engines and you gotta pay the going rate for them I guess.



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RE: PROFI RAMBLER .049 - 12/13/2012 12:59 AM   
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Status: online 		I wonder if it runs on suction? Looks like a beauty! I hope to see a video on youtube soon! and an engine tear down! ha! Gotta love the pictures that are in focus, a bit better then the ones supplied by alberto!

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RE: PROFI RAMBLER .049 - 12/13/2012 1:37 AM   
MJD



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Status: offline 		Gotta learn to use the macro feature.. and hold still. I didn't exactly take these in a studio either, I was using a point and shoot with no flash in the basement, hand held with slow shutter speed..

Tear down, hmm, might not do that. I'll peek in the top and backplate, but that's as far as I'll go for now. I can set it up in the bench pretty easily.

Very tight at TDC. Might warm it up for the first few starts. It came with a few head shims if no Nelson plug head. But now I gotta go buy some turbo plugs. I'll probably run a Driskill combat prop on it first, 4.75 x 2.75 or whatever they are, keep forgetting. They run smoothly (balance wise) and are a lighter shaft load I think. Then switch to the APC 4.2x4.

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RE: PROFI RAMBLER .049 - 12/13/2012 3:33 AM   
forsakenrider


 

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Status: online 		Just make sure the piston isnt at BDC when you unscrew the back plate! you'll break the skirt off the piston on some engines like this profi's brother, the combat version.

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RE: PROFI RAMBLER .049 - 12/13/2012 6:44 AM   
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Status: online 		Sounds like a good game plan MJD.
Bladder has some advantages, especially if the project has limited space for a padded fuel tank.
Fuel foaming [from a conventional fuel tank] is death to any engine...but launching a bladder fed engine with a "false" high pressure setting is very bad also.
The false high pressure comes from either too small of a bladder compartment or overinflating the bladder. Once the excess fuel burns off the remainder of the run has a drastic drop in pressure and the engine has to suffer through a lean run.
This is when you wish you had a simple fuel shutoff.
Fresh latex tubing [I like black for some reson] should last 6 flights if it doesn't get overinflated.
Before you buy the tubing, stretch it out. If it looks dry and rough, it isn't fresh.
I'm happy with 5/32" OD tubing with a thin wall..the wall somewhere between 1/32" and 1/16".
Use Sullivan brand small silicone tubing as an interface between the latex bladder and the needle valve. It really helps to keep a "kit" on hand to service all your bladder needs while at the field.
3/4 oz of fuel is all I ever load..that has always been enough to get a good flight in and get a decent impression of how that flight went.


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RE: PROFI RAMBLER .049 - 12/13/2012 7:05 AM   
airraptor


 

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Status: offline 		Nice engine looks like a smaller version of my 21...

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RE: PROFI RAMBLER .049 - 12/13/2012 8:00 AM   
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Status: online 		Actually the 1/2A Profi doesn't look much like the .21 other than the fact that they are both rear exhaust.



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RE: PROFI RAMBLER .049 - 12/13/2012 1:41 PM   
MJD



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quote:

ORIGINAL: airraptor

Nice engine looks like a smaller version of my 21...


Oooh, purty looking engine. I want a Profi F2A so bad, but despite my spendthrift ways I still can't justify the expenditure.

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RE: PROFI RAMBLER .049 - 12/13/2012 1:43 PM   
MJD



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quote:

ORIGINAL: combatpigg

Sounds like a good game plan MJD.
Bladder has some advantages, especially if the project has limited space for a padded fuel tank.
Fuel foaming [from a conventional fuel tank] is death to any engine...but launching a bladder fed engine with a ''false'' high pressure setting is very bad also.
The false high pressure comes from either too small of a bladder compartment or overinflating the bladder. Once the excess fuel burns off the remainder of the run has a drastic drop in pressure and the engine has to suffer through a lean run.
This is when you wish you had a simple fuel shutoff.
Fresh latex tubing [I like black for some reson] should last 6 flights if it doesn't get overinflated.
Before you buy the tubing, stretch it out. If it looks dry and rough, it isn't fresh.
I'm happy with 5/32'' OD tubing with a thin wall..the wall somewhere between 1/32'' and 1/16''.
Use Sullivan brand small silicone tubing as an interface between the latex bladder and the needle valve. It really helps to keep a ''kit'' on hand to service all your bladder needs while at the field.
3/4 oz of fuel is all I ever load..that has always been enough to get a good flight in and get a decent impression of how that flight went.


I always fill the bladders to capacity on the bench before installing. Apart from bursting, what symptoms do you see when a bladder had had too many runs?

I have a stock of small silicone tubing for 1/2A FF use, it handles bladder pressure well.

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RE: PROFI RAMBLER .049 - 12/13/2012 4:16 PM   
aspeed


 

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Status: offline 		MJD, if you don't want to spend the money on a Profi F2A motor, there is the Irvine .15 Halman Special.  I have no idea where to get them, but they can be made to go well. I would think it is a special order at a 'special' price and you would need to talk directly to the factory.  They at least speak english (British anyway)  Sometimes bladders get a hernia when they get old, but usually you just get the burning in the eyes.

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RE: PROFI RAMBLER .049 - 12/13/2012 10:52 PM   
MJD



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Status: offline 		£450-470 for the Halman special.. ouch!

F2A engine prices are definitely in the rarified air category!

I can get an MB Profi .40 for less. It is the "other" insane engine of choice in my books. However, nobody I know of is flying F2A engines RC at the moment, whereas the Profi is relatively commonplace.

Maybe I'll just dream about the .15..

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RE: PROFI RAMBLER .049 - 12/14/2012 1:01 AM   
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Status: offline 		Oh, I guess I won't fly that anymore.  We used a Rossi when I did it.  They were $120 in 1977 when minimum wage was $1.80 hr.  I had to get a couple of them too.  You could try an F2D motor, they are less trouble to get a clean run and only $230 last I looked.  I bet (not too much) you could get a used one off one of the Combat guys.  That's what I did, They are pretty quick too.

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RE: PROFI RAMBLER .049 - 12/14/2012 1:56 AM   
MJD



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Status: offline 		The F2D engines are very quick, I'm sure. But my whole reasoning is the desire to use a piped hyperactive F2A engine in an RC model. Although not up to a modern F2D motor, I have my ABC converted Conquest with FF venturi which will do a good job on something suitable with the right prop.

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RE: PROFI RAMBLER .049 - 12/14/2012 2:16 AM   
aspeed


 

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Status: offline 		My Conquest has the steel piston/cyl, and is pretty strong but not like the Fora.  Maybe a Novarossi .21 or one of the Novarossi .15's from a rc car.  You could check into what they use.  I think HPI motors are made by Novarossi for the buggies.  You don't really need the 8 port ones a three or 5 would be more suitable.  You can't really use the pipes or the flywheel etc, and they need machining though.

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RE: PROFI RAMBLER .049 - 12/14/2012 3:18 AM   
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quote:

ORIGINAL: MJD
I always fill the bladders to capacity on the bench before installing. Apart from bursting, what symptoms do you see when a bladder had had too many runs?

I have a stock of small silicone tubing for 1/2A FF use, it handles bladder pressure well.


Ideally, a healthy bladder GAINS fuel pressure at the end of the run and the engine dies rich. The walls of the tubing regain original thickness as the bladder empties and so pressure should go higher than when the bladder was full.
The "hernia" or "annuerism" from wear & tear, "ODing" or not being fresh tubing causes the reverse to happen. First sign [of FUBAR] will be a sloppy shutdown with no signs of the engine going rich towards the end of the run.
If you have the room for a tank...crankcase pressure sure is easy. I don't know why the CLspeed guys don't use it..unless centrifugal force makes it less reliable


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RE: PROFI RAMBLER .049 - 12/14/2012 5:08 AM   
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Status: offline 		Wow.... I can't believe they 3D machined the inside of the exhaust spigot..

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RE: PROFI RAMBLER .049 - 12/14/2012 1:52 PM   
aspeed


 

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Status: offline 		The control line guys do use backplate pressure.  It doesn't work well with a pipe without a cenrifugal fuel switch which is unreliable because of air leaks.  The ground setting has to so rich that the plane usually won't take off.  Bladders don't work either.  The combat guys I think use the bladder because of the good even run but also because of the positioning  of the tank is less critical, as well as being well protected from damage.  Goodyear racing and slow goodyear racing are great for backplate pressure, but it is usually specified to use suction, so it isn't popular. Speed events without a pipe often use a bladder because of the rich cutoff being easier on the motor than a hot run and a lean ending.  That is the kind of reverse of blowing up a balloon which is very hard to start but much easier and even after the first puff. Air leaks are a major problem with backplate pressure but otherwise it is great.  I was reading somewhere on one of the forums that a test was made on a motor with the same prop, and it was slightly faster with a bladder than a tank. It wasn't really done as a test for a tank but I thought iti was interesting, maybe the pressure loss makes it slower?  ( I think I am on these forums too much, but it is too cold to fly)

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RE: PROFI RAMBLER .049 - 12/14/2012 2:02 PM   
MJD



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ORIGINAL: combatpigg

Ideally, a healthy bladder GAINS fuel pressure at the end of the run and the engine dies rich. The walls of the tubing regain original thickness as the bladder empties and so pressure should go higher than when the bladder was full.
The ''hernia'' or ''annuerism'' from wear & tear, ''ODing'' or not being fresh tubing causes the reverse to happen. First sign [of FUBAR] will be a sloppy shutdown with no signs of the engine going rich towards the end of the run.
If you have the room for a tank...crankcase pressure sure is easy. I don't know why the CLspeed guys don't use it..unless centrifugal force makes it less reliable


I probably have not flown bladders enough to have run into a herniated or weak bladder*, so far I have had my RC models apart at frequent intervals and replaced the bladders before any trouble. I only dabbled in C/L and the vast majority of that was on Coxes and the rest with wedge tanks on sport engine.

My film canister clunk tanks are a bit wide for this RC speed model. If I design the model properly so that fuel system maintenance doesn't require surgery, I'll just stay on top of the bladder life cycle.


* although after getting it banged up in a car accident 30 years ago I think I might be seeing the symptoms now..

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RE: PROFI RAMBLER .049 - 12/14/2012 5:27 PM   
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Status: online 		Aspeed..you're saying that pipe pressure delivers fuel pressure proportionally to demand better than bladder or crankcase pressure...?
That was told to me by Henry Nelson about his FAI .40.
With extreme engines like these that make extreme fuel demand changes while unloading this must be the truth.
Otherwise, regulators that work off a diaphram actuated check valve can reduce the need to launch the plane extra rich. Problem is the added complexity expecting the little spring loaded check valve to perform flawlessly 600-700 times per second.


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