os50...how much pitch

[dogbiscuit]

I am still very much on a learning curve here with the new trex 600le nitro. I have had three days at the field with it, getting to grips with tuning, setting up beastx and generaly flying a large nitro, all for the first time.....quite a lot to take in! As I begin to push it more each time i fly, I am noticing that the motor bogs on full pitch climbouts (but not every time). the first question really, is how much pitch range should an os50sx be able to handle? Am I asking too much of it to run more than +10 degrees of pitch? or should this motor handle more.

other factors are....

I am running a 12,5 % optifuel.....(perhaps I should run higher but I am only at the fast sports level of flying)
I currently have not set up the govener and am running a v throttle curve, with high points at 100, and low point at 60, in idle up.
obviously, tuning will also play a big part in the power the motor produces.....I am trying to get my senses dialed in to temp, smoke and engine sound, but this will take a bit of time so i dont expect to be getting it spot on imediately....so being on the richer side for safety will be sapping a bit of power I guess.

so, where should i be with the pitch....and any other thoughts also apreciated.

[Baldie]

Im using the 50 Hyper, and run +/- 11.5 deg pitch with no problems, (also run 7 deg cyclic pitch just for info)

But I am using 20% opti slv.

You may do better increasing the centerpoint of your throttle curve, If you think about it, When you go to full pitch, the blades will hit 10 deg before the engine opens up (a bit like letting a car struggle up a hill then only changing down one gear -The engine is already struggling to pick back up)

If you go for a higher point in the middle then it will give the rpm a chance to "stay on top" of the pitch, which is where a gov will help - But you shouldn't use the gov when tuning the engine, It can make it harder to tune.

[dogbiscuit]

ok, increasing the centre point makes sense, but will this then over rev the motor on faster decents......?

[Baldie]

If you have gone full pitch as you are now, When you unload at the top, It will over rev anyway I suspect, If you are powering it down you will be using 100% throttle....

[jimmyhorns]

There are two things here:

1) it it tuned properly?

2) get your governor installed.

There is always going to be 'bog' with a nitro as you go to full pitch, as you are suddenly loading up the engine without warning.

The aim is to limit this as much as possible, but you are never going to get rid of it completely, unless you are running an insanely powerful engine.

Your 12.5% nitro probably isnt helping. That engine likes 20%. I have the same engine and it hates bekra 10%, grumbles a bit on 16% but is flyable and loves 20%. I use optifuel when I can, it seems to run better on it than model technics stuff.

Higher nitro will make it easier to tune (to a point), another helping hand.

How are you monitoring your temp, and dialing in your main needle?

Do you have the 60L (idle jet and main jet) carb, or a carb with a mid needle?

James

[dogbiscuit]

I am monitoring the temperature with my finger on the backplate.....going over ambient, but making sure I can keep my finger on the plate. It has one needle only, and an idle tune (?) behind a brass plate just above the needle.
I have been watching the finless vids on tuning today to help me progress with tuning for the next trip to the field. So far it has been tuned by climbing out a few times, landing, and feeling the temp. leaning if too cold, richening if too hot. so basic at this stage. I am aware that in the finless vids they also tune the mid range and the transition between the two can be seen when you climb and then go centre stick, with the smoke hopefully staying near consistent as you unload the head. the bit I dont get is how am I getting any differences in throttle range tuning with one needle...

[waveydavey]

Any idea what your headspeed is, the OS50 is in the sweet spot at 2058 (17500 at 8:5:1), go a touch higher to give it a chance to stay in it should you bog a touch. I wouldn't run 12.5% on the 50 unless I was hovering about, even then you want the engine to cool properly, 20% as a minimum. Run it nice and rich and allow the engine to run at it's best and it will pull 11 degrees all day long, 12 at a push if you're careful.

[JoeBailey]

The OS 50 likes to scream as well don't be afraid to let it get some serious head speed, my fury55 is running with the gov set to 2100 and the engine just screams but pulls like a train. I have 13 degrees pitch set but don't use it all (well not all the time). I've also found that giving the throttle a blip before a hard punch out will really help maintain the head speed. Every flyer is differant so there will be a bit a trial and error on pitch settings. As to the bogging you just need to gain a softer throttle stick to prevent it.

Going from electric to nitro is hard but it will improve your flying overall. Pitch management is very usefull.

[jimmyhorns]

You should be able to keep your finger on the back plate for a fair few seconds with a 50, but not forever (its the advice I have been working off and was given by someone who has been doing this a lot longer than me.) On a 90 you should be able to keep your finger on there indefinitely, on a 30 for less time.

Personally I think this is a pretty crude way of doing it, and I use the temp telemetry from a head temp sensor. The absolute number isnt very important, but what you will find is, as you lean the engine out it will get warmer slowly, click by click on the needle, and then suddenly (just a couple of clicks) will see a dramatic rise in the temp. At this point you need to back off by a few clicks to get a margin of safety.

Its sometimes difficult to get your head round how the needles work, but the two you have are not completely seperate in their action.

One is called the low speed needle, and it has Most of its effect at low throttle openings.

The other is called the high speed needle, and it has Most of its effect at full throttle.

Most hovering is done at mid throttle, and at this stage Both needles have an effect on the fuel air mix.

As a result, its actually hardest to tune the hover, and that is why some engines have a mid needle too, to fine tune this.

Probably the most dangerous situation is to have the slow speed needle too rich, and then to have the high speed to lean. This could give you the right mix at hover, a reliable idle (albeit a bit wet) but when you go full pitch, it will lean out too much.

If im tuning a two needle system, I first get the high speed needle right by doing climb outs. I then adjust the low speed to give a nice reliable idle that isnt too wet (this sometimes doesnt need doing at all, as the factory settings often are pretty close to perfect), and then go back and check the high speed needle, to make sure its not too lean.

Does this help at all?

[dogbiscuit]

Any idea what your headspeed is, the OS50 is in the sweet spot at 2058 (17500 at 8:5:1), go a touch higher to give it a chance to stay in it should you bog a touch. I wouldn't run 12.5% on the 50 unless I was hovering about, even then you want the engine to cool properly, 20% as a minimum. Run it nice and rich and allow the engine to run at it's best and it will pull 11 degrees all day long, 12 at a push if you're careful.

dont know the head speed, how are you calculating you head speed or are you using a tacho (i do have the yellow $30 turnigy tacho from hk that I can drag from the back of the cupboard if its good enough)

[waveydavey]

Your yellow Turnigy thing will work fine. The figures I gave above are calculated from the gearing and the point at which the OS gives you it's all which is 17500rpm. So in short if you go for a headspeed of 2100 and tacho this to suit, changing your throttle curve to give this the engine will pull with all it's might. You may of course want a lower headspeed for pootling around and consequently the engine won't pull in a climb out at it's best. The speeds given in fairness are for spirited flying and you may not want this so adjust accordingly, or fit a governor and forget about your curves, although you do learn a lot about engines this way.

[dogbiscuit]

You should be able to keep your finger on the back plate for a fair few seconds with a 50, but not forever (its the advice I have been working off and was given by someone who has been doing this a lot longer than me.) On a 90 you should be able to keep your finger on there indefinitely, on a 30 for less time.

Personally I think this is a pretty crude way of doing it, and I use the temp telemetry from a head temp sensor. The absolute number isnt very important, but what you will find is, as you lean the engine out it will get warmer slowly, click by click on the needle, and then suddenly (just a couple of clicks) will see a dramatic rise in the temp. At this point you need to back off by a few clicks to get a margin of safety.

Its sometimes difficult to get your head round how the needles work, but the two you have are not completely seperate in their action.

One is called the low speed needle, and it has Most of its effect at low throttle openings.

The other is called the high speed needle, and it has Most of its effect at full throttle.

Most hovering is done at mid throttle, and at this stage Both needles have an effect on the fuel air mix.

As a result, its actually hardest to tune the hover, and that is why some engines have a mid needle too, to fine tune this.

Probably the most dangerous situation is to have the slow speed needle too rich, and then to have the high speed to lean. This could give you the right mix at hover, a reliable idle (albeit a bit wet) but when you go full pitch, it will lean out too much.

If im tuning a two needle system, I first get the high speed needle right by doing climb outs. I then adjust the low speed to give a nice reliable idle that isnt too wet (this sometimes doesnt need doing at all, as the factory settings often are pretty close to perfect), and then go back and check the high speed needle, to make sure its not too lean.

Does this help at all?

This does help, thanks. With my first attempts I was initially only able to hold the finger on for about 4 seconds, then I had to remove it. for safety's sake i richened a little more to the point where I could keep the finger on indefinately......but the motor was still quite warm. So, I should go back to a little leaner then......

the brass plate on the low needle has not been touched by me, but it seems to tickover well. I guess its factory setting or set by the previous owner..... didnt want to touch it in the early stages. I will work out where it is set.

[waveydavey]

The low needle should be either side of 12 OClock a small bit, not 2 or 3 or 10 or 11 but somewhere inbetween. If it works in the middle then I would say for now leave it

[jimmyhorns]

This does help, thanks. With my first attempts I was initially only able to hold the finger on for about 4 seconds, then I had to remove it. for safety's sake i richened a little more to the point where I could keep the finger on indefinately......but the motor was still quite warm. So, I should go back to a little leaner then......

the brass plate on the low needle has not been touched by me, but it seems to tickover well. I guess its factory setting or set by the previous owner..... didnt want to touch it in the early stages. I will work out where it is set.

5 seconds I understand is the golden time for a 50 sized engine, but then you have to take that with a pinch of salt.

For some reason my fingers are very temperature sensitive. A hot mug of coffee is often difficult for me, but my wife will hold it happily without thinking it too hot. The upshot of this is that everyones 5 second temperature is going to be different. Also the less pressure you apply with your finger, the less heat transfer you will get and the longer you will be able to hold it on. Its really just a rough guide to if you are running super lean or super rich.

From your sig it looks like you have a Dx8... why not get the TM1000 which comes with a temp sensor AFAIK, and then you wont have to faff about under the bird on the back plate?....

[dogbiscuit]

Your yellow Turnigy thing will work fine. The figures I gave above are calculated from the gearing and the point at which the OS gives you it's all which is 17500rpm. So in short if you go for a headspeed of 2100 and tacho this to suit, changing your throttle curve to give this the engine will pull with all it's might. You may of course want a lower headspeed for pootling around and consequently the engine won't pull in a climb out at it's best. The speeds given in fairness are for spirited flying and you may not want this so adjust accordingly, or fit a governor and forget about your curves, although you do learn a lot about engines this way.

It is my intention to get the govenor wired in a some point, but as it was done with curves before goveners arrived, I am happy to get used to setting up this way for a while.
I have done head speed calcs on the 500 some time back, but am rusty and cant for the life of me remember how I did it....can you link me to a nitro head speed calculation example, or talk me through how you did it

thanks to all of you who are replying with really helpfull advise on this one, much appriciated