Rotax 582 RPM

[Henni]

Hi Morph,

Thanks, I am definitely going to experiment with my prop settings, a luxury that I've never had before.

One other thing that I'm going to experiment with is: viewtopic.php?t=2076

I'm absolutely convinced that, if managed properly, it could prove to be a huge advantage. (i.e use it for emergency conditions only)

Anyone knows where I can purchase such a system for the 582?

Regards,

Henni

[DieselFan]

Dieselfan, just remember adding pitch to a prop will reduce your max rpm , increase the cruise speed and decrease the climb rate and increase fuel economy, but at what cost. What is also does is adds loading to the motor and loading increases the EGT. Better economy also means less fuel and it needs the fuel in the oil to help keep cool. There is a happy medium that needs to be found.

My egt's are around 1100F, altho on recently on one trip they were VERY low QNH was around 1033 and they were 600-700F, it was my 2nd coldest day of flying. Should I be worried with such low egts? RPM on full throttle was the same as norm tho.

In terms of loading on the motor at 4500rpm I should have around 170nm torque after box. If I compare to some others using a 3:1 box they'd have 166nm @ 6000rpm. At 4000rpm I'd have 155 and some 582's put on a 2.58 ratio which should have 100nm @ 4000. Same am I damaging the motor, is the gearbox not lightening the load.

Where does one draw the line between torque and hp?

Thanks Morph.

[Morph]

930 F - 1150 F are the recommended safe EGT ranges. I don't know how it could have dropped so low as 600-700F. but I have heard that some probes can be affected by ambient temperatures

When I talk about load I mean the drag the prop induces on the motor not the torque measured at the hub. I guarantee you at 6000RPM your EGT's will be higher with a highly pitched prop than with a lower pitched prop at the same RPM

When I first bought my Challenger the props were pitched for 6000rpm max static. The EGT's used to shoot up on take off and generally you had to reduce throttle a bit to keep them down. I changed my prop to a 2 blade wood prop, peaking at 6250rpm I could takeoff at this rpm and run all day, at 6000rpm is was cooler than previously on the other prop

[Duck Rogers]

There is a document somewhere that details wear on a 2 stroke and by running at lower rpm's with a higher loading i.e. high pitch, dramatically increases the wear on the motor

If you're talking about the HALT test (Highly Accelerated Life Test) here it is:http://home.clear.net.nz/pages/s.parker/tech.html

[Morph]

That's the one

Thanks Duck

[DieselFan]

Bugger! I've got a few question tho, perhaps I need to reread and reread. thanks Duck!

There's a few things I don't understand / agree with. I agree that yes lower rpm could labour the motor, but the way he has applied the formula I think is incorrect.

The article suggests and gets the two confused, that A when a motor needs more torque it's more wear and tear and B when a motor has more torque it's more wear and tear.

When a motor is driven / used within it's torque range it should be LESS labourous. One of the reasons why diesel generators outlast petrol ones is due to this fact. Ideally looking at the dyno graph best cruise would be at 6000rpm as the motor would work less ie less fuel to do a given amount of work, ofcourse thats now not taking into account what percentage rpm that is cause that would play a factor too.

It also suggests a 5% reduction in rpm would be 5% more torque required, however that wouldn't hold true at 6500 as the reduction in RPM would mean the engine can actually do more work without hurting. Using the way he has applied the HALT formula diesel engines / cars would suffer big time. So it boils down to what is the definition of labouring an engine? Normally in a car sense it's when doing low rpm (out of torque band) and high throttle position, it will also not accelerate easily. However using an appropriate gearbox the labour is eliminated / minimized and one can cruise comfortably at 50% throttle even with the lower torque band.

[Duck Rogers]

What he say?
Oh, and the other one too

[Henni]

Hi everyone,

Well, after this weekend's flying session I'm not so thrilled anymore.

With two up and 3/4 full tanks, the Mizer runs 80% of the full length of Siera Romeo before liftoff (downhill). I aborted the uphill takeoff as I did not feel comfortable when reaching 80% runway length. (I do not believe in just skimming over trees and telephone lines) Once in the air, I can only climb with RPM settings above 6400 RPM. It takes 6000 RPM to hold altitude in this configuration. Thus, when climbing, the engine runs at max power all the time & I'm not used to that.

Flying solo is a completely different story with power to spare.

Prop seems to be pitched correctly as I can only get 6800 RPM max in a shallow climb, so no danger of over revving.

Only thing I can think of for now is to try to get rid of all unwanted drag. The correct jets for our altitude might help, but I doubt if it would make a huge difference.

I also need a longer & unobstructed runway for safer flying under full gross weight conditions (I fly like this often). I do not like to put me or my PAX under unneeded risk when doing recreational flying.

I am amazed when I think back of how much easier the MXII seemed to climb with two aboard using only a Rotax 503 engine. I must admit that the Mizer is much heavier and carries twice as much fuel, but I'm still disappointed with her climbing capabilities in that configuration at our altitude.

I've heard some KRII guys mention a 150 fpm climbrate only with two aboard at our altitude. I would never be able to live with that - I dunno how you guys cope with it. Risky, to say the least.

Hope I can find a way to solve this problem rather quickly.(Or should I rather say: a problem at least for me. I might have become a real sissy with aging in the meantime).

Clem, I would really like to hear if you've experienced same with your Mizer. If not, then I have a simple power problem which can & will be corrected soon.

Henni

[Henni]

Hi everyone,

Seeing that it's Friday, we'll all be flying soon and I'm feeling very talkative (as usual), let me just straighten out my misconception with regards to all of the above:

I kept on comparing the Mizer to my ex MXII with the maxi thrust conversion. Well, last night I started reading through some of my saved posts from this forumn (I save every thread that's of interest to me)

I came upon a discussion about fuel consumption and RPM settings for the Cheetah 582.

viewtopic.php?t=4100

To my astonishment, I read that this Cheetah uses 20-22 litres/hour fuel during cruise and cannot maintain altitude at lower than 5800-6000RPM with two aboard & all of this using the 3.47:1 gearbox. Now, the Cheetah is a much cleaner configuration that the Mizer.

Then, on top of this, I've heard that someone with a nearly brand new Thunderbird 582 refuses to fly with a PAX using more than half a tank of fuel due to the poor climb performance at full gross!

Now, this was an eye opener for me - this means that what I am currently experiencing with the Mizer is right on par with other 3-axis types using a similar engine and all of this on only a 2.58:1 gearbox!

I feel much better now. I must just get used to this new environment, that's all. One of you should have straightened me out right away - shame on you for leaving me in my delusion!

Great, so now I can stop whining and start to enjoy flying again without stressing all the time. If the 582 can cope under those conditions in the Cheetah & in the Thunderbird, then it will also cope with the flying requirements of the Mizer.

Have a GREAT flying weekend, all of you.

Henni

[Big-D]

Bitching about lift and take-off roll - You sound like me

I had a Safari 582 with 3.47:1 Gearbox and NC Prop - Climbed (and still climbs with Nkwasi) like a home sick angel.

Got the Gemini with 2:63:1 Geabox, much smaller Warp drive prop - Lift is not the same, and she rolls much longer than a Safari BUT She is also faster and more stable - I have learned that everything is give and take in flying, add speed and loose lift, all about choice.

1-Up I get 650fpm (I weigh 130kg) in the Gem, have never taken pax in the Gemini so I cannot qoute performance there.

My advice to you Henni is fly from a longer runway and don't expect the new bird to climb like the old one, just need to get used to it :D

D

[Henni]

Hi Big D,

Thanx - good advice. It took me an awful long time to come to the same conclusion. Glad I'm not the only one going through these type of convulsions.

A Mizer is NOT a MXII, & a Ducati is NOT a scrambler! Simple things are so hard to understand.

Henni

[Henni]

Hi almal,

Net 'n finale woord oor my Mizer:

Na hierdie naweek is ek nou heeltemal oor my RPM bekommernisse - Dit lyk vir my asof alle 3-as 582 microlights vol krag vir klim gebruik. Noudat ek hierdie feit aanvaar het, is die Mizer net reg vir my soos is. Ek wou baie dinge doen om haar op te gradeer, maar dan kan ek eerder die geld later spandeer om iets beter te koop, veel makliker & minder sukkel met papierwerk.

Sy is definitief loshande die beste aerie wat ek tot dusver kon bekostig - ek beskou haar nou in dieselfde klas as die Thunderbirds, selfs al lyk sy nie so indrukwekkend soos hulle nie. Die verbleikdheid pla my ook glad nie meer nie, nie na hierdie naweek se lekker vlieg nie. Sy voel niks vir ruk-dwarswinde nie - ek het die hele naweek sonder moeite gevlieg toe die meeste ander microlights in hangars weggekruip het. Vir die geld wat ek vir haar spandeer het kon ek nie beter kry nie - ek kan nie glo dat die vorige eienaar so moes sukkel om haar verkoop te kry nie, maar dit was alles tot my voordeel!

Morph, ek is baie dank aan jou verskuldig vir hierdie "deal". Ron, dankie dat jy haar na my toe laat gaan het. Graham, dankie dat jy my "uitgesort" het toe ek weer terug Skyfoxes toe wou neuk! Vroulief, dankie dat jy my toegelaat het om haar te koop en selfs bereid was om saam te gaan om haar so ver te gaan haal.

Henni

[Morph]

Spleasure

BTW if you do have an EGT watch it next time you climb out at full throttle. My 503 ran cooler at WOT than she did at cruise.

When I first bought my Challenger the previous owner took me for a few circuits and one of the things he did on every takeoff was reduce throttle by 100 to 200 rpm once climb out was established. I always questioned this since at that time she was running at 6000rpm WOT and significantly lower than the maximum 6800. He told me it was to keep the engine cooler as the engine should not run longer than 5min at WOT and it would prolong engine life. K@K

I did a lot of testing and changed the prop to give me 6250 rpm on climb out and she happily runs at WOT and cooler than at 200rpm lower. I have taken off from Nooitgedagcht at 1000ft AMSL and had to climb (2-up) for a solid 15 minutes at 400fpm to clear to 4000ft mountains surrounding the airfield. It's a different story if you are running above the recommended max of 6800

Morning Star is surrounded by trees and my brain tells me to get as much altitude as quickly as possible at max rate of climb. A technique I have used is to hop off the ground asap and stay within ground effect to build airspeed. Then pull her back into the best rate of climb speed and she will climb like a fart in a bath and it's great fun. I have never understood the take off, throttle back and gradually climb, mentality. Altitude is your friend. Get away from the ground as quickly as possible in case of problems.

[justin.schoeman]

I am not sure about the rotax carbs, but the jabis use a tapered needle so that at full throttle it richens the mixture a bit. This causes the EGTs to drop, and the engine to be a bit happier. Bringing the throttle back will drop the RPM but also lean the mixture, raising the temperatures.

So, in a climb (low airspeed), it is better to run at max continuous RPM. This way you get lower temps, and the better climb rate means you can throttle back to cruise earlier.

Climbing at a lower power setting causes a leaner mexture and higher temp, without the extra airflow you get at cruise speed.

-justin

[Henni]

Hi Morph & Justin,

Thank you - you guys are causing me to feel better all the time. Running at full throttle for long periods (10 minutes or so) is a completely new experience for me. But you are completely right, the temps stays well within limits unde those conditions.

I have not yet jetted my 582 for the Highveld - it's still set up for the coast. To play it even safer, I'm going to leave as is - I'd rather run richer but also cooler.

Full throttle in a climb for me is 6700 RPM, a little close to red line, but still within limits. I'm hesitant to increase my prop pitch at this stage as I might just loose some climb performance.

As soon as I have some spare funds available, I'll purchase a wide bladed Powerfin prop & sell my Ivo. This would definitely help the performance, I'm totally convinced of it. But it'll have to wait until I'm ready.

Morph, I'm going to try out your takeoff technique next time I fly - I'd like to see if it helps to gain altitude more quickly for the amount of ground covered.

Regards,

Henni