---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Mon 04/23/18: 15 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:38 AM - Re: Balance Master (Bill Berle) 2. 06:31 AM - Re: Balance Master (Jack Hart) 3. 06:34 AM - Re: Balance Master (Jack Hart) 4. 06:40 AM - Re: Balance Master (Jack Hart) 5. 06:57 AM - Re: Balance Master (Jack Hart) 6. 07:28 AM - Re: Balance Master (Jack Hart) 7. 08:29 AM - Re: Balance Master (Jack Hart) 8. 10:02 AM - Re: Balance Master (Jack Hart) 9. 11:00 AM - Re: Balance Master (Richard Pike) 10. 11:21 AM - Re: Re: Balance Master (John Hauck) 11. 11:46 AM - Re: Re: Balance Master (Charlie England) 12. 12:50 PM - Re: Re: Balance Master (Bill Berle) 13. 01:04 PM - Re: Firestar 2 / HKS engine progress (Bill Berle) 14. 04:50 PM - Re: Balance Master (Richard Pike) 15. 08:42 PM - Re: Re: Balance Master (Bill Berle) ________________________________ Message 1 _____________________________________ Time: 12:38:10 AM PST US From: Bill Berle Subject: Re: Kolb-List: Balance Master The Balance Master guy came to our EAA chapter meeting and made a presentation. Very impressive. He had a small electric motor driving an un-balanced disc with a weight mounted off center. It shook itself half to death on the table. He installed the balance Master device and the thing ran smoothly. We all looked at it to see if it was some sort of scam, or that he had "rigged" the demonstration, but it looked 100% legit to all of us. Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Sun, 4/22/18, Richard Pike wrote: Subject: Kolb-List: Balance Master To: kolb-list@matronics.com Date: Sunday, April 22, 2018, 3:18 PM Pike" I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=479482#479482 The Kolb-List Email Forum - Navigator to browse List Un/Subscription, 7-Day Browse, Chat, FAQ, - MATRONICS WEB FORUMS - via the Web Forums! - NEW MATRONICS LIST WIKI - Email List Wiki! - List Contribution Web Site - support! -Matt Dralle, List Admin. ________________________________ Message 2 _____________________________________ Time: 06:31:51 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 3 _____________________________________ Time: 06:34:56 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 4 _____________________________________ Time: 06:40:55 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 5 _____________________________________ Time: 06:57:09 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 6 _____________________________________ Time: 07:28:04 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 7 _____________________________________ Time: 08:29:56 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 8 _____________________________________ Time: 10:02:01 AM PST US From: "Jack Hart" Subject: re: Kolb-List: Balance Master Richard, Hold on a day. I have one I will send to you after I find it. Jack B. Hart FF004 Winchester, IN ---------------------------------------- From: "Richard Pike" Sent: Sunday, April 22, 2018 6:20 PM Subject: Kolb-List: Balance Master I have seen these advertised for years, no personal experience. http://balancemasters.com/aircraft.html The engine/gearbox/prop on the FF is a Rotax 277, B-box (2.58:1) and two blade 62" Ivo, and is very smooth over 5200 rpm but terrible between 5100-4000. Performance is excellent other than the vibration. I am thinking harmonics, but who knows??? Wondering if the Balance Master would be worth trying, but before I spend the $, would like to hear from somebody who has actually tried one. Thanks. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 ________________________________ Message 9 _____________________________________ Time: 11:00:38 AM PST US Subject: Kolb-List: Re: Balance Master From: "Richard Pike" Jack Hart: What a prince! Thank you, can't wait to try it out and see how it does. John Hauck: you are correct, I am sure that the Austrian gnomes at Gunskirchen tuned the 277 for optimum power between 6250 and 6500, and I am sure it would happily churn away at that speed all day. However, while 6250 - 6500 rpm is where the engine makes its rated power, that does not necessitate the engine having to be consistently operated at that rpm. Here is a very good website of tutorials by the Australian light aircraft people - https://www.recreationalflying.com/tutorials/index.html and from their page on "Engines and Propellers", "Although aero-engines can quite happily operate continually at their rated power, doing so is not good practice. It is uneconomical in terms of fuel efficiency, but more importantly it may shorten engine life, if engine operating temperatures and pressures are exceeded. Normally the maximum and optimum power setting for continuous cruise operation is 75% of rated power." Then they deal specifically with the 2-stroke; "Two-strokes don't have very good volumetric efficiency, and the engine is generally efficient only in the upper 30% of its rpm and throttle opening range. In fact, ultralight two-strokes tend to run very roughly at speeds below 2500 rpm and achieve their rated power at rotational speeds in the 5500 to 6500 rpm range. The three most common two-strokes are two-cylinder models with individual cylinder displacements around 250 cc; they achieve their rated power at 6500 rpm and 75% power at around 5300 rpm." Something else to consider is that running an engine slower than its rated power does not lug it. Once again from the recreationalflying.com tutorial page: "the power delivered by a propeller varies in accordance with rpm cubed (if everything else is kept constant)" Therefore, as rpm is decreased from the engine/propeller maximum attainable rpm, the load reduction on the engine decreases exponentially. (don't know the right technical term for a decrease cubed, but you get the idea) Back when I was flying a Maxair Hummer with a Rotax 277, it spent most of its time around 54-5500 rpm. The 582 on my MKIII spends most of its time around 54-5500 rpm solo, 56-5700 rpm when I have a passenger. When I am in a hurry, it runs at 6200 rpm and sucks gas like it was free. The 277 on the Firefly is still breaking in, but right now it appears that the sweet spot is going to be around 5500 rpm to run right and fly right. I have not been trying to fly it at rpm's below 5100, it is that (possibly due to still breaking in?) if it gets below 5100 down to around 4000, as in when making a descent to land, it vibrates more than it ought to. This is typically in a semi - unloaded state, throttle retarded, engine providing minimal thrust. Once it gets below 4000 rpm, the vibration goes away. David & I have discussed changing the two blade Ivo to a three blade as a way to deal with the vibration, but only if we have to. Right now we have an 800'/min climb rate, and we would hate to have to give that up by going to a smaller diameter prop. As always, appreciate your input, gives us all a chance to think these things through and stimulate the old grey matter. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=479496#479496 ________________________________ Message 10 ____________________________________ Time: 11:21:50 AM PST US From: "John Hauck" Subject: RE: Kolb-List: Re: Balance Master Don't think I explained myself very well, as usual. I indicated the only numbers I could find were max power. Could not find anything for cruise power. Was not inferring the engine needed to be operated at max power. Not that familiar with fixed wing aircraft, but on several of the Army helicopters I was privileged to fly there were RPM areas to stay out of. When running up, don't hesitate in these yellow zones. 4000 to 5200 may be a similar zone with the 277. If it was me, I'd fly Hell out of it and stay out of 4000 to 5200 except to transit that rpm. Don't know if a 3 blade will solve your problem, but you won't know until you try. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Richard Pike Sent: Monday, April 23, 2018 1:00 PM Subject: Kolb-List: Re: Balance Master Jack Hart: What a prince! Thank you, can't wait to try it out and see how it does. John Hauck: you are correct, I am sure that the Austrian gnomes at Gunskirchen tuned the 277 for optimum power between 6250 and 6500, and I am sure it would happily churn away at that speed all day. However, while 6250 - 6500 rpm is where the engine makes its rated power, that does not necessitate the engine having to be consistently operated at that rpm. Here is a very good website of tutorials by the Australian light aircraft people - https://www.recreationalflying.com/tutorials/index.html and from their page on "Engines and Propellers", "Although aero-engines can quite happily operate continually at their rated power, doing so is not good practice. It is uneconomical in terms of fuel efficiency, but more importantly it may shorten engine life, if engine operating temperatures and pressures are exceeded. Normally the maximum and optimum power setting for continuous cruise operation is 75% of rated power." Then they deal specifically with the 2-stroke; "Two-strokes don't have very good volumetric efficiency, and the engine is generally efficient only in the upper 30% of its rpm and throttle opening range. In fact, ultralight two-strokes tend to run very roughly at speeds below 2500 rpm and achieve their rated power at rotational speeds in the 5500 to 6500 rpm range. The three most common two-strokes are two-cylinder models with individual cylinder displacements around 250 cc; they achieve their rated power at 6500 rpm and 75% power at around 5300 rpm." Something else to consider is that running an engine slower than its rated power does not lug it. Once again from the recreationalflying.com tutorial page: "the power delivered by a propeller varies in accordance with rpm cubed (if everything else is kept constant)" Therefore, as rpm is decreased from the engine/propeller maximum attainable rpm, the load reduction on the engine decreases exponentially. (don't know the right technical term for a decrease cubed, but you get the idea) Back when I was flying a Maxair Hummer with a Rotax 277, it spent most of its time around 54-5500 rpm. The 582 on my MKIII spends most of its time around 54-5500 rpm solo, 56-5700 rpm when I have a passenger. When I am in a hurry, it runs at 6200 rpm and sucks gas like it was free. The 277 on the Firefly is still breaking in, but right now it appears that the sweet spot is going to be around 5500 rpm to run right and fly right. I have not been trying to fly it at rpm's below 5100, it is that (possibly due to still breaking in?) if it gets below 5100 down to around 4000, as in when making a descent to land, it vibrates more than it ought to. This is typically in a semi - unloaded state, throttle retarded, engine providing minimal thrust. Once it gets below 4000 rpm, the vibration goes away. David & I have discussed changing the two blade Ivo to a three blade as a way to deal with the vibration, but only if we have to. Right now we have an 800'/min climb rate, and we would hate to have to give that up by going to a smaller diameter prop. As always, appreciate your input, gives us all a chance to think these things through and stimulate the old grey matter. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=479496#479496 ________________________________ Message 11 ____________________________________ Time: 11:46:29 AM PST US From: Charlie England Subject: Re: Kolb-List: Re: Balance Master What John described is actually quite common in certified fixed wing a/c, as well. Many that are equipped with metal constant speed props have a 'yellow arc' (usually around 2000-2200 rpm on an engine with max 2700 rpm). While not a problem to transition through that range, continued operation there can result in a broken crankshaft or prop. Remember, these are FAA-blessed aircraft. It's worth pointing out that just because you don't feel it, doesn't necessarily mean it's not there (might not be exciting the airfame so you're feeling it at higher rpms, but still out of balance). But if it's bad enough to be annoying, you probably want to stay away from that speed range; you're probably operating near the natural resonant frequency of the system and stuff can sometimes break very quickly there. Have you tried *dynamically* balancing the prop? It isn't cheap to pay an a&p to do it, but many EAA chapters have one of the less expensive models you can borrow or rent. Charlie On Mon, Apr 23, 2018 at 1:20 PM, John Hauck wrote: > > Don't think I explained myself very well, as usual. > > I indicated the only numbers I could find were max power. Could not find > anything for cruise power. Was not inferring the engine needed to be > operated at max power. > > Not that familiar with fixed wing aircraft, but on several of the Army > helicopters I was privileged to fly there were RPM areas to stay out of. > When running up, don't hesitate in these yellow zones. 4000 to 5200 may be > a similar zone with the 277. If it was me, I'd fly Hell out of it and st ay > out of 4000 to 5200 except to transit that rpm. > > Don't know if a 3 blade will solve your problem, but you won't know until > you try. > > john h > mkIII > Titus, Alabama > > > -----Original Message----- > From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list- > server@matronics.com] On Behalf Of Richard Pike > Sent: Monday, April 23, 2018 1:00 PM > To: kolb-list@matronics.com > Subject: Kolb-List: Re: Balance Master > > > > Jack Hart: What a prince! Thank you, can't wait to try it out and see how > it does. > > John Hauck: you are correct, I am sure that the Austrian gnomes at > Gunskirchen tuned the 277 for optimum power between 6250 and 6500, and I am > sure it would happily churn away at that speed all day. However, while > 6250 - 6500 rpm is where the engine makes its rated power, that does not > necessitate the engine having to be consistently operated at that rpm. > > Here is a very good website of tutorials by the Australian light aircraft > people - https://www.recreationalflying.com/tutorials/index.html > and from their page on "Engines and Propellers", > "Although aero-engines can quite happily operate continually at their > rated power, doing so is not good practice. It is uneconomical in terms o f > fuel efficiency, but =C3=A2=82=AC=9D more importantly =C3=A2 =82=AC=9D it may shorten engine life, > if engine operating temperatures and pressures are exceeded. Normally the > maximum =C3=A2=82=AC=9D and optimum =C3=A2=82=AC=9D pow er setting for continuous cruise operation > is 75% of rated power." > > Then they deal specifically with the 2-stroke; "Two-strokes don't have > very good volumetric efficiency, and the engine is generally efficient on ly > in the upper 30% of its rpm and throttle opening range. In fact, ultralig ht > two-strokes tend to run very roughly at speeds below 2500 rpm and achieve > their rated power at rotational speeds in the 5500 to 6500 rpm range. The > three most common two-strokes are two-cylinder models with individual > cylinder displacements around 250 cc; they achieve their rated power at > 6500 rpm and 75% power at around 5300 rpm." > > Something else to consider is that running an engine slower than its rate d > power does not lug it. Once again from the recreationalflying.com > tutorial page: "the power delivered by a propeller varies in accordance > with rpm cubed (if everything else is kept constant)" Therefore, as rpm i s > decreased from the engine/propeller maximum attainable rpm, the load > reduction on the engine decreases exponentially. (don't know the right > technical term for a decrease cubed, but you get the idea) > > Back when I was flying a Maxair Hummer with a Rotax 277, it spent most of > its time around 54-5500 rpm. The 582 on my MKIII spends most of its time > around 54-5500 rpm solo, 56-5700 rpm when I have a passenger. When I am i n > a hurry, it runs at 6200 rpm and sucks gas like it was free. > > The 277 on the Firefly is still breaking in, but right now it appears tha t > the sweet spot is going to be around 5500 rpm to run right and fly right. I > have not been trying to fly it at rpm's below 5100, it is that (possibly > due to still breaking in?) if it gets below 5100 down to around 4000, as in > when making a descent to land, it vibrates more than it ought to. This is > typically in a semi - unloaded state, throttle retarded, engine providing > minimal thrust. Once it gets below 4000 rpm, the vibration goes away. > > David & I have discussed changing the two blade Ivo to a three blade as a > way to deal with the vibration, but only if we have to. Right now we have > an 800'/min climb rate, and we would hate to have to give that up by goin g > to a smaller diameter prop. > > As always, appreciate your input, gives us all a chance to think these > things through and stimulate the old grey matter. > > -------- > Richard Pike > Kolb MKIII N420P (420ldPoops) > Kingsport, TN 3TN0 > > Forgiving is tough, being forgiven is wonderful, and God's grace really i s > amazing. > > ________________________________ Message 12 ____________________________________ Time: 12:50:58 PM PST US From: Bill Berle Subject: Re: Kolb-List: Re: Balance Master There are several FAA certified airplanes with fixed pitch metal propellers that also have those "caution" and "avoid" ranges of RPM. The mathematics and engineering for figuring that out are way above anything I can understand, but I know that these vibration and resonance issues are very real. There is a famous video of Sikorsky doing "ground resonance testing" on a Chinook (I believe) where the helicopter just tears itself apart on the ground. Terrifying spectacle. John H I hope you were not the test pilot sitting in that aircraft in that video !!! I needed a change of underwear just watching the video on a computer... Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 4/23/18, Charlie England wrote: Subject: Re: Kolb-List: Re: Balance Master To: kolb-list@matronics.com Date: Monday, April 23, 2018, 11:45 AM What John described is actually quite common in certified fixed wing a/c, as well. Many that are equipped with metal constant speed props have a 'yellow arc' (usually around 2000-2200 rpm on an engine with max 2700 rpm). While not a problem to transition through that range, continued operation there can result in a broken crankshaft or prop. Remember, these are FAA-blessed aircraft. It's worth pointing out that just because you don't feel it, doesn't necessarily mean it's not there (might not be exciting the airfame so you're feeling it at higher rpms, but still out of balance). But if it's bad enough to be annoying, you probably want to stay away from that speed range; you're probably operating near the natural resonant frequency of the system and stuff can sometimes break very quickly there. Have you tried *dynamically* balancing the prop? It isn't cheap to pay an a&p to do it, but many EAA chapters have one of the less expensive models you can borrow or rent. Charlie On Mon, Apr 23, 2018 at 1:20 PM, John Hauck wrote: "John Hauck" Don't think I explained myself very well, as usual. I indicated the only numbers I could find were max power. Could not find anything for cruise power. Was not inferring the engine needed to be operated at max power. Not that familiar with fixed wing aircraft, but on several of the Army helicopters I was privileged to fly there were RPM areas to stay out of. When running up, don't hesitate in these yellow zones. 4000 to 5200 may be a similar zone with the 277. If it was me, I'd fly Hell out of it and stay out of 4000 to 5200 except to transit that rpm. Don't know if a 3 blade will solve your problem, but you won't know until you try. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@ matronics.com [mailto:owner-kolb-list- server@matronics.com] On Behalf Of Richard Pike Sent: Monday, April 23, 2018 1:00 PM To: kolb-list@matronics.com Subject: Kolb-List: Re: Balance Master Jack Hart: What a prince! Thank you, can't wait to try it out and see how it does. John Hauck: you are correct, I am sure that the Austrian gnomes at Gunskirchen tuned the 277 for optimum power between 6250 and 6500, and I am sure it would happily churn away at that speed all day. However, while 6250 - 6500 rpm is where the engine makes its rated power, that does not necessitate the engine having to be consistently operated at that rpm. Here is a very good website of tutorials by the Australian light aircraft people - https://www. recreationalflying.com/ tutorials/index.html and from their page on "Engines and Propellers", "Although aero-engines can quite happily operate continually at their rated power, doing so is not good practice. It is uneconomical in terms of fuel efficiency, but more importantly it may shorten engine life, if engine operating temperatures and pressures are exceeded. Normally the maximum and optimum power setting for continuous cruise operation is 75% of rated power." Then they deal specifically with the 2-stroke; "Two-strokes don't have very good volumetric efficiency, and the engine is generally efficient only in the upper 30% of its rpm and throttle opening range. In fact, ultralight two-strokes tend to run very roughly at speeds below 2500 rpm and achieve their rated power at rotational speeds in the 5500 to 6500 rpm range. The three most common two-strokes are two-cylinder models with individual cylinder displacements around 250 cc; they achieve their rated power at 6500 rpm and 75% power at around 5300 rpm." Something else to consider is that running an engine slower than its rated power does not lug it. Once again from the recreationalflying.com tutorial page: "the power delivered by a propeller varies in accordance with rpm cubed (if everything else is kept constant)" Therefore, as rpm is decreased from the engine/propeller maximum attainable rpm, the load reduction on the engine decreases exponentially. (don't know the right technical term for a decrease cubed, but you get the idea) Back when I was flying a Maxair Hummer with a Rotax 277, it spent most of its time around 54-5500 rpm. The 582 on my MKIII spends most of its time around 54-5500 rpm solo, 56-5700 rpm when I have a passenger. When I am in a hurry, it runs at 6200 rpm and sucks gas like it was free. The 277 on the Firefly is still breaking in, but right now it appears that the sweet spot is going to be around 5500 rpm to run right and fly right. I have not been trying to fly it at rpm's below 5100, it is that (possibly due to still breaking in?) if it gets below 5100 down to around 4000, as in when making a descent to land, it vibrates more than it ought to. This is typically in a semi - unloaded state, throttle retarded, engine providing minimal thrust. Once it gets below 4000 rpm, the vibration goes away. David & I have discussed changing the two blade Ivo to a three blade as a way to deal with the vibration, but only if we have to. Right now we have an 800'/min climb rate, and we would hate to have to give that up by going to a smaller diameter prop. As always, appreciate your input, gives us all a chance to think these things through and stimulate the old grey matter. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. ________________________________ Message 13 ____________________________________ Time: 01:04:36 PM PST US From: Bill Berle Subject: Re: Kolb-List: Firestar 2 / HKS engine progress Just a quick update on my HKS installation in the Firestar. After waiting months for the guy to be available, I finally had the last of the exhaust parts fabricated and welded! So now I have two 1.25" stainless exhaust pipes coming down from the engine exhaust ports, joining together and running down the rear of the fuselage cage, then a 2-into-1 collector at the right "tuning" location, then a 1.5" diameter "flex coupler", then a length of stainless tube that swings down and around to the bottom of the tailboom (fuselage tube), which then inserts into the front of the home made "Swiss Muffler" exhaust silencer. whew ! Now that the exhaust is complete, I will re-mount it on the aircraft and I can finally do a weight and balance to see where I have to mount the battery. I have waited to mo unt the battery because I literally have no idea whether it's nose-heavy or tail-heavy. With a little luck and no major obstacles, the Firestar should be ready for flight testing by this summer. Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 4/23/18, Charlie England wrote: Subject: Re: Kolb-List: Re: Balance Master To: kolb-list@matronics.com Date: Monday, April 23, 2018, 11:45 AM What John described is actually quite common in certified fixed wing a/c, as well. Many that are equipped with metal constant speed props have a 'yellow arc' (usually around 2000-2200 rpm on an engine with max 2700 rpm). While not a problem to transition through that range, continued operation there can result in a broken crankshaft or prop. Remember, these are FAA-blessed aircraft. It's worth pointing out that just because you don't feel it, doesn't necessarily mean it's not there (might not be exciting the airfame so you're feeling it at higher rpms, but still out of balance). But if it's bad enough to be annoying, you probably want to stay away from that speed range; you're probably operating near the natural resonant frequency of the system and stuff can sometimes break very quickly there. Have you tried *dynamically* balancing the prop? It isn't cheap to pay an a&p to do it, but many EAA chapters have one of the less expensive models you can borrow or rent. Charlie On Mon, Apr 23, 2018 at 1:20 PM, John Hauck wrote: "John Hauck" Don't think I explained myself very well, as usual. I indicated the only numbers I could find were max power. Could not find anything for cruise power. Was not inferring the engine needed to be operated at max power. Not that familiar with fixed wing aircraft, but on several of the Army helicopters I was privileged to fly there were RPM areas to stay out of. When running up, don't hesitate in these yellow zones. 4000 to 5200 may be a similar zone with the 277. If it was me, I'd fly Hell out of it and stay out of 4000 to 5200 except to transit that rpm. Don't know if a 3 blade will solve your problem, but you won't know until you try. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@ matronics.com [mailto:owner-kolb-list- server@matronics.com] On Behalf Of Richard Pike Sent: Monday, April 23, 2018 1:00 PM To: kolb-list@matronics.com Subject: Kolb-List: Re: Balance Master Jack Hart: What a prince! Thank you, can't wait to try it out and see how it does. John Hauck: you are correct, I am sure that the Austrian gnomes at Gunskirchen tuned the 277 for optimum power between 6250 and 6500, and I am sure it would happily churn away at that speed all day. However, while 6250 - 6500 rpm is where the engine makes its rated power, that does not necessitate the engine having to be consistently operated at that rpm. Here is a very good website of tutorials by the Australian light aircraft people - https://www. recreationalflying.com/ tutorials/index.html and from their page on "Engines and Propellers", "Although aero-engines can quite happily operate continually at their rated power, doing so is not good practice. It is uneconomical in terms of fuel efficiency, but more importantly it may shorten engine life, if engine operating temperatures and pressures are exceeded. Normally the maximum and optimum power setting for continuous cruise operation is 75% of rated power." Then they deal specifically with the 2-stroke; "Two-strokes don't have very good volumetric efficiency, and the engine is generally efficient only in the upper 30% of its rpm and throttle opening range. In fact, ultralight two-strokes tend to run very roughly at speeds below 2500 rpm and achieve their rated power at rotational speeds in the 5500 to 6500 rpm range. The three most common two-strokes are two-cylinder models with individual cylinder displacements around 250 cc; they achieve their rated power at 6500 rpm and 75% power at around 5300 rpm." Something else to consider is that running an engine slower than its rated power does not lug it. Once again from the recreationalflying.com tutorial page: "the power delivered by a propeller varies in accordance with rpm cubed (if everything else is kept constant)" Therefore, as rpm is decreased from the engine/propeller maximum attainable rpm, the load reduction on the engine decreases exponentially. (don't know the right technical term for a decrease cubed, but you get the idea) Back when I was flying a Maxair Hummer with a Rotax 277, it spent most of its time around 54-5500 rpm. The 582 on my MKIII spends most of its time around 54-5500 rpm solo, 56-5700 rpm when I have a passenger. When I am in a hurry, it runs at 6200 rpm and sucks gas like it was free. The 277 on the Firefly is still breaking in, but right now it appears that the sweet spot is going to be around 5500 rpm to run right and fly right. I have not been trying to fly it at rpm's below 5100, it is that (possibly due to still breaking in?) if it gets below 5100 down to around 4000, as in when making a descent to land, it vibrates more than it ought to. This is typically in a semi - unloaded state, throttle retarded, engine providing minimal thrust. Once it gets below 4000 rpm, the vibration goes away. David & I have discussed changing the two blade Ivo to a three blade as a way to deal with the vibration, but only if we have to. Right now we have an 800'/min climb rate, and we would hate to have to give that up by going to a smaller diameter prop. As always, appreciate your input, gives us all a chance to think these things through and stimulate the old grey matter. -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. ________________________________ Message 14 ____________________________________ Time: 04:50:45 PM PST US Subject: Kolb-List: Re: Balance Master From: "Richard Pike" This one? https://www.youtube.com/watch?v=0FeXjhUEXlc Or maybe this one? https://www.youtube.com/watch?v=RihcJR0zvfM Congratulations on surviving! victorbravo(at)sbcglobal. wrote: > There are several FAA certified airplanes with fixed pitch metal propellers that also have those "caution" and "avoid" ranges of RPM. The mathematics and engineering for figuring that out are way above anything I can understand, but I know that these vibration and resonance issues are very real. > > There is a famous video of Sikorsky doing "ground resonance testing" on a Chinook (I believe) where the helicopter just tears itself apart on the ground. Terrifying spectacle. John H I hope you were not the test pilot sitting in that aircraft in that video !!! I needed a change of underwear just watching the video on a computer... > > Bill Berle > -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=479503#479503 ________________________________ Message 15 ____________________________________ Time: 08:42:55 PM PST US From: Bill Berle Subject: Re: Kolb-List: Re: Balance Master No, this one: https://www.youtube.com/watch?v=D2tHA7KmRME Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Mon, 4/23/18, Richard Pike wrote: Subject: Kolb-List: Re: Balance Master To: kolb-list@matronics.com Date: Monday, April 23, 2018, 4:50 PM Pike" This one? https://www.youtube.com/watch?v=0FeXjhUEXlc Or maybe this one? https://www.youtube.com/watch?v=RihcJR0zvfM Congratulations on surviving! victorbravo(at)sbcglobal. wrote: > There are several FAA certified airplanes with fixed pitch metal propellers that also have those "caution" and "avoid" ranges of RPM. The mathematics and engineering for figuring that out are way above anything I can understand, but I know that these vibration and resonance issues are very real. > > There is a famous video of Sikorsky doing "ground resonance testing" on a Chinook (I believe) where the helicopter just tears itself apart on the ground. Terrifying spectacle. John H I hope you were not the test pilot sitting in that aircraft in that video !!! I needed a change of underwear just watching the video on a computer... > > Bill Berle > -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing. 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