Irvine 39 abc setup help

[snukiedog]

Hi , I have recently installed an irvine 39 abc in my heli , fingers crossed I have completed the running in correcly(1.5 lts of fuel(15%nitro 18%synth oil))I followed the manual for throtle and times. My problem now is the fine tuning, at the moment I have the main 2 turns from closed, when I start to lean in alittle more I can notice the change in sound at high throtle but when I drop the gas nothing happens for half a second and the revs increase with a distinct lack of smoke(up until this point there is plenty of smoke) and after a second or 2 the revs begin to come down, would I be correct in thinking that this is a sign of too lean? forgot to say that the engine is in the heli strapped to a bench with no rotor head or tail rotor assembly; if anybody could pass me any tips or infomation they would be much appreciated!!!
many thanks Snukiedog

[Heli Head]

First off, you need load on your engine. You should really mount it in your heli, or at least mount a propeller on it - that size engine would probably take a 10/6, but still the best is to mount it in your heli. Perhaps you did this already?

The first thing that is critical with all ABC engine is proper heat cycling when breaking in as you know from the instructions. With no load and if you didn't have a propeller installed for air cooling or have the engine in the heli for fan cooling - I am thinking you might have done considerable damage to your engine already. If you had a cooling source and load no problems. There are many ABC break in procedures - I am now a full believer in breaking in an ABC engine just on the slight side of rich, not super rich as has been the long standing normal procedure. Run them for 5 min at varying throttles and then let the engine cool right down - increasing the run times and the high speed throttle durations during the break in procedure and slowly leaning it out. The whole idea is to get proper heat cycling to expand and contract the piston and cylinder for a 100% perfect running fit. If you are running rich and cold, this will not happen to the same extent. Since using this hotter needle method in my nitro cars, my ABC engines have huge compression and last for years.

I personally feel, a ringed engine in a heli is a better long term choice, but that is just my own opinion from 20 years of flying.

Once you get the break in sorted out, you will want your heli to run just a bit on the rich side and set your idle needle mixture screw so when you pinch your fuel line closed at idle speed, the engine will continue to run and then speed up and die in about 4-5 seconds from when you pinched off the fuel line.

These are good base settings, but things like fuel used, altitude at your location, and specific bird set-up will alter these settings. If you have an air bleed screw in your carb (forgive me, I am not 100 % familiar with the Irvine 39 ABC heli engine) you can further improve the carb settings. The air bleed is used to set your idle, your idle mixture is used to set your mid range, and your needle valve to set your high end. This (3-setting) carb adjustment method is ideal for nitro helis because you no longer have to have your idle mixture set super rich to compensate for lean mid range.

Hope that Helps,

H.H.
www.rchelicopterfun.com

[Heli Head]

Forgive me,

I misread that the engine was in the heli, and the heli was strapped to to the work bench. I originally thought you just had the engine on a test bench - sorry.
So cooling would not have been an issue, but with no load, the engine would over speed and not get up to correct running temp. So you must put the rotor and tail rotor blades on to make the adjustments.

I actually do something kind of dangerous when I am setting up a nitro engine on a heli, but it works and rarely do I have to mess around with things at the field after words.

I clamp the bird onto a Work-Mate bench and then crawl under the heli and perform all engine adjustments (low, mid, and high) while the bird is running. As long as you have a good way to clamp it down and make 100% sure you don't lift your head up, this is a very quick way of setting all carb adjustments to get everything almost perfect for your first flight in less than one tank of fuel usually.

If you do try this, be very-vary careful. Wear impact goggles, ear plugs, and even a helmet just in case. Keep your hands low and away from the main gear or fan. After making the adjustment, throttle down to idle and crawl back out from under the heli and then recheck the engine transitions etc. You will get nitro oil mist on you and your radio, so spend as little time under the heli as possible. It is not a nice environment under there.

Just a thought - The last thing I want is for someone to loose their head over this method - literally!

H.H.
www.rchelicopterfun.com

[snukiedog]

Hi , heli head , thanks for the tips, as soon as I've tried them I'll let you know how everything went, have taken note of your saftey advise . Many thanks !!

[hawkman]

You can use a 'headloader' which bolts in place of the main blades...basically headloaders are alloy poles with balls on the end...the balls are perforated and as these rotate they are meant to give the same resistance as the blades. The idea being you can run the engine in the heli and on the ground.

Trouble is you can set the carb up accordingly but when you fit the blades and go fly the settings are no good anymore.

The reason is that the headloaders cant truly replicate the true resistance of the blades, as the blades turn and so on, there are differing loads...add cyclic pitch too and it gets a bit more difficult.

Headloaders have their place in getting a 'problem' engine to run, as long as you accept that final adustments have to be made once the engine is running and the blades are fitted.

Not being cheeky here...at all...but bolting to a table will not represent the true 'in flight' loads that the engine/carb have to cope with.

You basically have the carb settings about right with what you have mentioned before.

Rob

[Heli Head]

Hey Rob,

Totally agree the real flight loads are not the same. With a fastened heli, you are actually putting more strain on the entire system than you would in a hover or forward flight. This is especially true when running at full pitch/throttle and while holding in full tail rotor pitch too giving maximum engine loading. This makes high speed idle setting actually quite accurate and able to handle the most aggressive flying without running lean.

My biggest tuning pain has always been mid range and running too lean while the rotor transitions or during fast descents when I am pulling negative pitch. A fastened heli certainly doesn't reproduce this 100% accurately, but it gets it pretty darn close and in the ball park. Fine tuning will always be required. As you know, even fuel and weather conditions can have an effect, everything about tuning a helicopter engine is a compromise.

All that said, it is a dangerous method, and you are correct to point out it has limitations.

Cheers,

H.H.
www.rchelicopterfun.com

[hawkman]

The most dangerous I ever saw was in some magazine in Argentina. I was on holiday and reading through this and found an article on RC helis...the bloke only had the thing by its skids above his head...and appeared to be tweaking the carb with someone else by his side looking on.

The Heli was a Shuttle, so not the most powerful thing ever but even a heli this size will give you some injuries.

I have heard of the table method before, and agree that for all out power its a good option. I used headloaders in the past but while they are good for a 'baseline' setup on a carb they dont really replicate the real deal.

I have spun the head up without blades before, but only at a fast idle..up to half power but no more. Its ok to do this but the learner must be aware of the tail rotor...this will pull one way or the other...so be very careful of what you are doing...better to clamp the skids down with something...and be careful of the flybar paddles...these can still cut/hurt you.

Rob