Setting the pitch (IVO)

[Dirtydog]

60" IVO UL 3-blade....
I have noticed that my RPM's have been running high on my 503 Rotax engine it has the 2.58 to 1 B gear box on it and the max RPM should be set at 6800.

I have tried to set it this past weekend, but ended taking the pitch out it seemed like because I lost power.

I have been told it should be 5-1/2 turns from neutral or 0 pitch to the left to increase. If you turn to the right it will decrease pitch.

Any comments?

I will try the other way this weekend and I guess it would help to have a scale to set it to max pitch and power.

[Fl90]

I set mine at 6500. If you look at the tips, you can see more or less pitch. What was your max rpm tied down and full throttle...before?...after?

Phil

[Earthboundmisft]

Chris, I have the exact same prop on my 582. I will be interested in your findings, as I have to set mine too. I have no advice beyond the included instructions. Keep me posted please. Thanks, Mike.

[SideKick]

I have the same prop on my 447 which has the same max rpm of 6800. Although that is the max it does not produce anymore torque at 6800 than it does at 6500.
So what I do is to tie down the gyro and keep adjusting pitch until it turns 6200 at full throttle. Then when I am flying it will turn 6500.
Again. 6200 while tied down will give you 6500 when flying.
Hope this helps.

[ckurz7000]

Originally Posted by SideKick

...Although that is the max it does not produce anymore torque at 6800 than it does at 6500....

Just to clarify: the same torque at 6500 as at 6800 will produce 5% more power at the higher rpms.

-- Chris.

[scottessex]

I had my Ivo set at 6200 on the ground but could easily see 6800 in flight.
You should not hold the rotax at 6800 for more than 5 minutes, unless it is a 618, then fly it at 7000 all day.
The IVO seems to unload more than the warp drive.

[Dirtydog]

Thanks for all the input guys,
But Well I thought I would ask this: The IVO prop is like the governor on the engine? (Right)
Ok so if you turn the pitch up the engine should not turn any more RPM's than 6500 at full throttle (right or wrong).
OR
Do you have to set you throttle so the engine can not go any higher than Max RPM's?


(TIED DOWN) The reason I ask this is I tied the bird down the other day to get the throttle set to MAX 6500 rpm's at the stand still. But when I got out on the runway and got the blades turning up I pushed the throttle to go I was dead no power to push me so I had to remove the stop bolt.

This is one of those questions you hate to ask because you because it makes you feel like you are beating your head against a wall to ask...... (You should know the answer)

[getut]

Dog, don't feel like that. I consider myself an expert at being green and scared of two strokes. I haven't ran across anyone yet who tried to make me feel stupid asking the questions that I asked with my 582 on the Soma before I sold it.

The prop should be the RPM limiter with the carbs slides completely open... that is of course wide open throttle. Don't limit the RPMs by limiting to less than full throttle.

I agree... 2 strokes seem more like black arts than science. From tuned exhausts getting the resonance right combined with jet needles and needle jets and jet airplanes and flying witches aaaaaaahhhhh.

I was never comfortable... but i thank everyone who ever answered my stupid 2 stroke questions and I apologize for the blank stare with drool dripping from my chin in return when I got some of the answers I got.

[GrantR]

Chris,

Yes set your max rpm with full wide open throttle tied down. Think about it if you had the prop set with little pitch you could rev the engine to maybe 10K rpms. If you limited rpm with the throttle to 6500 rpms your engine would only be putting out maybe ½ the horsepower it could and about half the thrust it could. So your 50hp would be 25 even though its turning 6500 rpm. No load equals less power to do the same work.

Look at it this way a much smaller engine could spin the same prop at 6500 rpms no problem with little to no pitch set in it but all you would get is a fast turning prop not blowing any air!

What stop bolt are you talking about?

[scottessex]

Yes the prop is the LOAD on the engine, it needs to be set to limit or Govern the RPM,
at wide open throttle, or WOT.

You should have no stop bolt on the throttle.

[Jason O]

I think you should have a stop bolt on the throttle, it should just be set up so that the throttle stop is hit on the carb a fraction of an inch before you hit the stop on the throttle lever. This save allot of stress on the cable and maybe prevent you from pulling an end off of the cable.

[Redbaron]

Not sure what you use to adjust your throttle with dog but on my plane I use a fitting on the firewall that grips the housing the throttle rides in. For adjustment I loosen the fitting and open the throttle to max move the housing till the throttle hits the top of the carb and tighten the fitting up, this will leave slack in the cable when at idle but doesn't put stress on the cable at full throttle!

Originally Posted by Jason O

I think you should have a stop bolt on the throttle, it should just be set up so that the throttle stop is hit on the carb a fraction of an inch before you hit the stop on the throttle lever. This save allot of stress on the cable and maybe prevent you from pulling an end off of the cable.

[Earthboundmisft]

I have a Brock throttle on my 582. I found by observing my slides as I opened the throttle, that the slides lift past the throats by 1/8th inch or so. I carefully installed a roll pin on the throttle housing to limit the travel, and allow the slides to be flush with the top of the throats at wot. Side benefit is the cable cant ever bind.