Raptor 50 Tuning...

[tailStrike]

Hey guys,

A couple of q's:

I am still trying to get my throttle curves and engine setup properly. I used the method discussed on Raptor Technique that suggests setting the initial throttle curve to 20-40-50-60-80 and adjusting the middle points +/- 10% until the heli hovers at mid-stick. In order to achieve this I ended up with a 20-50-60-70-85 curve, which is at the limit of the range before the author suggested leaning out the motor.

I think my motor is obviously running rich as it really feels sluggish in the air and a friend at the field let me use his IR thermometer after a flight and the temp was only about 105-110F on the block and 115F on the portion of the pipe connected to the exhaust port.

1.) Any pointers on when one knows the motor is tuned properly? Is this temperature way too low? I am scared to pop another piston as this is my 2nd motor and I really don't have any other small engine experience. All things I have heard are rather ambiguous (motor shouldn't be too hot, not too cold; not too much smoke, but no smoke bad; and now this "if it doesn't hover at mid stick below 60% throttle" thing)

2.) Secondly, I can't seem to get the full amount of negative pitch out of the head before the collective arm binds. I'm only getting -7 deg. Am I missing something?

Thanks in advance,
Kyle

[nitro burner]

What engine are you running, what pipe and whats your top pitch before binding.

[tailStrike]

Sorry forgot to mention the motor/pipe - OS 50 SX-H w/ the standard 50 muffler heli proz puts in their combo kits (not sure of brand). I just checked and I can get about 14 deg pos pitch out of my setup. I had the travel dialed down on the high side of the pitch servo to keep my pitch curves reasonable. On a CCPM setup, I would just shorten the lengths to the swash, but the fore/aft cyclic links are not adjustable on the MPM Rappy, so I don't see how I could shift some of that travel to the low side.

Should I shorten the links to the mixing arms? I set everything up with the lengths specified in the manual.

[BarracudaHockey]

Adjust it for symetical end points on your pitch, I run -11 to +11 yes you will have to tinker with the rods on the head to get that, its no biggie, just make sure they are the same length.

Start leaning out the engine, you will be in the 190 degree range on the head when its broken in.

You will probably end up hovering with the throttle point around 35 percent or so because of the power output of the hyper. I'd suggest your next purchase be a governor when you start thrashing it about.

[tailStrike]

Thanks, Andy. I'll start tinkering with the mixing arm links and leaning that sucker out now that I have a target temp.

A governor is definitely the next thing on my list along with some stiffer dampers and greenies.

Kyle

[tailStrike]

After shortening the lengths from the 100mm the manual suggests to 97mm, I am spot on with +/- 11 deg with my pitch servo travel adjustment at 100% on both ends. Good deal. Now hopefully I can get to the field this weekend and lean this motor out.

EDIT: Made it out today and she flew like a champ. Cyclic is much more responsive and right where I like it now after moving the balls to the outer holes on the mixing arms. I leaned it out about 10 clicks and it did seem to have a bit more pep, but it looks like I have some more room to lean it out as the head only reached about 130 - 135 deg F.

[tailStrike]

Adjust it for symetical end points on your pitch, I run -11 to +11 yes you will have to tinker with the rods on the head to get that, its no biggie, just make sure they are the same length.

Start leaning out the engine, you will be in the 190 degree range on the head when its broken in.

You will probably end up hovering with the throttle point around 35 percent or so because of the power output of the hyper. I'd suggest your next purchase be a governor when you start thrashing it about.
Ok, we had a nice day today in Bristol, TN, so I made it out to the field and worked on the carb some more (I know - is this guy ever going to get his heli tuned properly?). Anyways, last weekend it puttered out on me again (I brought her down w/ a lovely auto, if I do say so myself, thanks to G3) and I hadn't tried to restart it until today. Anyways, turned out I killed another plug (haven't been getting more than a few flights out of them).

I replaced with a spare and decided that the low-speed was rather rich as you there was a distinct change in pitch in the exhaust note at around 3/4 throttle. This seemed to help idle some and it did sound more consistent throughout the flight. I also ended up leaning the high speed a couple of clicks and ended up with a head temp of 200 degrees.

It still seems to me to bog quite a bit using +/- 11 deg pitch. I notice that Michael Prewitt recommends 9 degrees. Should I back the pitch down some, or do I have some tuning to do yet? Also, I still need to put a longer servo arm on my throttle servo as per this advice:
http://www.raptortechnique.com/throttle.htm

I have been reluctant to do so as I came across that bit of info after getting my fuel curves and endpoints setup on my governor, etc.