---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Sun 08/31/14: 6 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:35 AM - Re: pitch? (Stuart Harner) 2. 01:40 PM - Prop inertia & the B box (Richard Pike) 3. 02:39 PM - Re: pitch? (Jack B. Hart) 4. 03:19 PM - Rudder Failure on my Xtra. (Brad Nation) 5. 05:47 PM - Re: Rudder Failure on my Xtra. (John Hauck) 6. 07:47 PM - Re: Rudder Failure on my Xtra. (Rick Neilsen) ________________________________ Message 1 _____________________________________ Time: 06:35:59 AM PST US From: "Stuart Harner" Subject: RE: Kolb-List: pitch? Thanks Rick, that helps. This list once again proves what a great bunch of guys make it up. I have sent an email to WD about this and will wait for a reply. Holiday weekend and all, plus I am on the road for work next week, so it may be a while before I find out what they say. I will let you know what comes of this. Thanks again to everyone! Stuart From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Richard Girard Sent: Saturday, August 30, 2014 8:20 PM Subject: Re: Kolb-List: pitch? Stuart, I'm re-posting this response just in case it didn't come through. And I'm going to add something after. Before you get rid of your WD prop, know this. Most of the MOI problems on "B" gearboxes come from trying to make the engine idle at too low an RPM. Doing this beats up the dogs and wears out the spring washers in the gearbox. Just keep the RPM at idle at 2000 or more and you'll be just fine. You have one more option before you dump the prop. Have the blades tapered. It's going to mean putting another $200 or so dollars into the prop but tapering the blades gets rid of mass on the blade tips where you get some good out of it. My 2 cents, your $200 bucks if you decide to do it. Rick Girard In the winter of 2006, hot out of LSARM training I built a rig and did the rotational inertia per Rotax Service Instruction 11 UL 91E published December of 1992 (attached). At the time I had six props for various aircraft in the shop. As I recall only the wood two blade that came with my Firestar passed and being of multi-laminate constuction only did barely. Jimmy Young also did tests on two props, a WD and an IVO if memory serves. Both were three blade props. Anyway, I stand by the recommendations above. I know I'm not alone in recommending WD props for one simple reason. They are great at holding up to the trials and tribulations of the pusher configuration. I put an AN 6 bolt through a Warp and didn't even know it until I landed. I put a cheap pair of bifocals through the Power Fin on my trike and it cost me two new blades. Rick On Sat, Aug 30, 2014 at 7:47 PM, Stuart Harner wrote: John, That was the exact impression I had, and the reason I did not question it any further. Seemed like he knew the plane, the engine and the gearbox. I did not get the "used car salesman" red flag. I really did not give it much extra thought until some replies to my starting pitch angle came back, indicating that this combo would not work. The numbers back this up, Rotax did not put the limits in the book just for the heck of it. However, no one has replied that Yes, they are running this combination and it is fine. The flip side of that is no one has said "I tried that and it tore up my gearbox", only some have warned that it would not work, according to the numbers. So, it would seem that it all comes down to whether I want to try it or not. I have been doing some research on this subject today, some of it I did not understand. I like physics, but am not very good at it. To me, a heavier prop (flywheel) would help smooth out the pulses of combustion, at the expense of quick throttle response. It seems to me that a lighter prop would speed up and slow down "faster" so that it would "hammer" the gears more. More rotational mass (MOI) would be slower to reach a set speed, but would also tend to continue rotating at that speed (minus the drag of producing thrust) therefore carrying the inertia into the next combustion pulse. To me this should dampen the "hammering of the gears effect". Maybe I just don't "get it". Something else I find interesting is that the Rotax manual warns never to run the engine without a prop (load) as it will damage the gearbox. They give a max MOI, but wouldn't there also be a minimum MOI? Maybe I am fretting over nothing. Maybe I should bolt it on and fly! I value EVERYONE's input, and thank you one and all. Stuart P.S. I still haven't heard a suggested starting pitch angle.... -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck Sent: Saturday, August 30, 2014 3:00 PM Subject: RE: Kolb-List: pitch? Daryl Heineman, President of Warp Drive, is probably the salesman you are referring to that sold you the prop. Normally, he is the only one selling them. Good man. Knowledgeable when it comes to Warp Drive Props and engine combos. I've flown with Warp, and done business with them, for 21 years. Tested them, unintentionally, to the max. They always come through and get me back home. I don't know what kind of flying you will be doing, but doubt you will ever be able to over stress your gear box with this prop and a FS???? Daryl was not trying to fool you, I am sure. I'd fly that combo. My experience and opinion only. Don't try this at home. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Saturday, August 30, 2014 11:04 AM Subject: RE: Kolb-List: pitch? Jack, Some others have raised that issue. I was aware of the MOI limits on gearboxes and quizzed Darrell at Warp Drive before I ordered the prop. He assured me it would be OK, but had no hard numbers for me. Now I am beginning to wonder if I was fooled by a salesman. :( I can easily set up and run the MOI tests myself to get the true answer, but I suspect I am not going to like it. Options are buy a new milled aluminum hub, but that is saving all the weight at the center, which won't help the MOI much. I could convert to a two blade hub, but the 60" is probably not able to put enough load on the engine at any kind of a reasonable pitch. I wanted to check out the Power Fin props at OSH, but could not find them on the field nor in the list of vendors. Now what I am going to say next is strictly personal and is NOT meant to start any flame wars over props: I know Travis recommends the IVO, but for me they are not an option due to other's experiences. End of story, no more gas for the flames. I have a good regard for the Warp Drives, related to the above sentence, again, no more gas. I am completely open to any other prop that gets the job done that is reasonably priced. I don't care about looks, but am concerned about vibration, price and noise, but of course they have to take a back seat to proper application. Some things I have read and conversations I have had led me to think that the 3 blade would be a better choice as it would be smoother and quieter than a 2 blade. I also liked the idea of a lower overall folded size (my hanger/trailer situation came into play here). Anybody want to buy a new prop that has not even had the bolts torqued down? Not the first stupid thing I have done, probably not the last either..... Stuart -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Jack B. Hart Sent: Saturday, August 30, 2014 9:02 AM Subject: RE: Kolb-List: pitch? --> > From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] Sent: Thursday, August 28, 2014 3:41 PM Hi, My Warp Drive prop (3 blade- 60) arrived yesterday and I am getting ready to set it up. It is going on my Firefly with a Rotax 447 (single carb), B-Gearbox with 2.58 ratio. ........................ > Stuart, I hope you have considered the following: The B gearbox is rated for a max moment of inertia of 1025 lb-in squared or 3000 kg-cm squared. Ultralight News of Canada found the three blade Warp prop exceeded these numbers. See: http://www.ultralightnews.ca/articles/driveselection.htm Warp Drive should be able to tell you the moment of inertia of your propeller. Or, the above site can direct you to a Rotax Service Bulletin that explains how to determine the moment of inertia of your prop. Jack B. Hart FF004 Winchester, IN -List" target="_blank">http://www.matronics.com/Navigator?Kolb-List FORUMS - _blank">http://forums.matronics.com b Site - -Matt Dralle, List Admin. target="_blank">http://www.matronics.com/contribution -- Zulu Delta Mk IIIC Thanks, Homer GBYM It isn't necessary to have relatives in Kansas City in order to be unhappy. - Groucho Marx ________________________________ Message 2 _____________________________________ Time: 01:40:09 PM PST US Subject: Kolb-List: Prop inertia & the B box From: "Richard Pike" Years ago CPS had a complete series of tech articles in their catalog on Rotax engines and gearboxes and one of those articles was on prop inertia and how much the B box could handle. CPS currently has a number of those tech articles online but not all of them. I still have an old CPS catalog that includes all the old articles and this is the article on prop inertia, so I scanned it, perhaps it will be useful. Also, since I am the list curmudgeon who gripes about ridiculously oversize pictures, and since I am not sure how big these pictures will turn out to be, I thought I better put it in a separate thread... [Wink] -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 My soul shall be joyful in the LORD; It shall rejoice in His salvation. Psalm 35:9 Read this topic online here: http://forums.matronics.com/viewtopic.php?p=429705#429705 Attachments: http://forums.matronics.com//files/prop1_176.jpg http://forums.matronics.com//files/prop2_417.jpg http://forums.matronics.com//files/prop_3_745.jpg ________________________________ Message 3 _____________________________________ Time: 02:39:48 PM PST US From: "Jack B. Hart" Subject: RE: Kolb-List: pitch? From: "Stuart Harner" >>>>>>>>>>>>>>>>>>>>>>> .................. I have been doing some research on this subject today, some of it I did not understand. I like physics, but am not very good at it. To me, a heavier prop (flywheel) would help smooth out the pulses of combustion, at the expense of quick throttle response. It seems to me that a lighter prop would speed up and slow down "faster" so that it would "hammer" the gears more. More rotational mass (MOI) would be slower to reach a set speed, but would also tend to continue rotating at that speed (minus the drag of producing thrust) therefore carrying the inertia into the next combustion pulse. To me this should dampen the "hammering of the gears effect". Maybe I just don't "get it". >>>>>>>>>>>>>>>>>>>>> Stuart, May be I can help you "get it". The moment of inertia is the spread of the mass about the center of rotation times the radius of gyration squared. Take a large hex nut and tie to the end of a string. Give it a whirl in the horizontal plane with a short radius and notice the tension in the string and the revolution count. Double string length and try to keep the rotation speed the same as before. You will find that the string tension more than doubles and the energy you have to exert to swing the whole thing goes way up. In this case the system mass "the nut" is constant but as the mass is moved out from the center of rotation more torque is required to keep rpm constant. These represent the loads as seen by the gear box and the crank. It is desirable to have a low inertia propeller so that the propeller can accelerate and de accelerate and absorb some of the firing impulse exerted on the crank by the piston and connecting rod. This reduces the peak oscillatory torque loads in the crank and on the face of the gear teeth. It is some what counter intuitive. With a lower inert propeller, the engine and gearbox will jump around a little more on the mounts. But internally the gear box and crank and piston rod bearing assemblies will be operating under lower peak loads while the system is delivering the same hp as it would with a higher inertia propeller. Jack B. Hart FF004 Winchester, IN ________________________________ Message 4 _____________________________________ Time: 03:19:42 PM PST US From: Brad Nation Subject: Kolb-List: Rudder Failure on my Xtra. Kolbers, The good news is that no one was ingured and the aircraft damage was relatively minor. It could have been a lot worse if it happened in the air. Recently we had a taxi test in my Xtra with a once around the pattern and shortly after landing the right rudder failed! Atfter a sharp left turn to exit off the runway, without the benefit of a taxiway, the Xtra ending up off the runway with both axels sheered off at the wheel and a bent right wing tip. After getting the plane back to the hanger I found that the rudder failure was caused by the weld failing between the upright square bar that connects the rudder to the cables. I also noticed that the axel is hollow. Should the axel be solid? Have any of the Kolbers experienced this before and if so, any suggestions as to the cause of the failure and the best course of action, repair or replace the failed part? I have attached the photos of the failed part and the sheered axel. Brad Nation MK III Xtra ________________________________ Message 5 _____________________________________ Time: 05:47:44 PM PST US From: "John Hauck" Subject: RE: Kolb-List: Rudder Failure on my Xtra. Not rudder failure, but what looks like a rudder crank that failed, not because the weld failed, but the round tube wall stressed cracked over time and failed. I had a similar aileron crank failure on a Ultrastar in 1985. Weld was good but the rotating tube wall stress cracked and failed. First I have heard of this type failure in a rudder crank. That doesn't mean much. Axles are normally tubular. Looks like yours are the popular 5/8" OD axles that use little ball bearings which cannot be adjusted. I upgraded to 3/4" OD axles with tapered roller bearings after I lost a wheel at Muncho Lake, BC, in 2000. Never had another problem with wheels, axles, and gear legs. Our MKIII aircraft are heavy when we strap in a couple husky guys, a full load of fuel, and anything else we can stick in there. I think MATCO advertises the 5/8" axles as 600 lbs static and 2000 lbs max. Most of us exceed that number a great deal. If you land at 3 g's, that's 1980 lbs. 4 g's is 2400 lbs. See what I mean. That is if you and your airplane weigh 600 lbs. 900 to 1000-1200 lbs is more like it. I guarantee those wheels, axles, and bearings have been constantly overstressed. I didn't realize that 14 years ago when I broke mine. Sorry it happened. It always hurts to break our airplane. john h mkIII Titus, Alabama From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Brad Nation Sent: Sunday, August 31, 2014 5:19 PM Subject: Kolb-List: Rudder Failure on my Xtra. Kolbers, The good news is that no one was ingured and the aircraft damage was relatively minor. It could have been a lot worse if it happened in the air. Recently we had a taxi test in my Xtra with a once around the pattern and shortly after landing the right rudder failed! Atfter a sharp left turn to exit off the runway, without the benefit of a taxiway, the Xtra ending up off the runway with both axels sheered off at the wheel and a bent right wing tip. After getting the plane back to the hanger I found that the rudder failure was caused by the weld failing between the upright square bar that connects the rudder to the cables. I also noticed that the axel is hollow. Should the axel be solid? Have any of the Kolbers experienced this before and if so, any suggestions as to the cause of the failure and the best course of action, repair or replace the failed part? I have attached the photos of the failed part and the sheered axel. Brad Nation MK III Xtra ________________________________ Message 6 _____________________________________ Time: 07:47:29 PM PST US Subject: Re: Kolb-List: Rudder Failure on my Xtra. From: Rick Neilsen The kolb list is very valuable in spreading the word if there is an issue. Thanks for reporting it. I think the issue might be that the rudder control system wasn't designed to handle the load that toe brakes put on the rudder control system. Flight loads and ground control steering just doesn't put that much load on it. Like so many things when a seemingly small change is made it can effect a bunch of other things. Those of us that have the old heal brakes shouldn't have a issue. For those that have toe brakes check for stress in the area described. Also check the rudder control horn on the rudder and the rudder hinges. It would seem that some beefing up of the rudder system is in order when using the newer toe brake setup. Seems like there was one toe brake installation that increased the leverage to the master cylinders for this very reason. Maybe both areas need to be looked at. In the mean time don't stand on those toe brakes. As always worth what you paid for it and refunds anytime. Rick Neilsen Redrive VW Powered MKIIIC On Sun, Aug 31, 2014 at 8:47 PM, John Hauck wrote: > Not rudder failure, but what looks like a rudder crank that failed, not > because the weld failed, but the round tube wall stressed cracked over ti me > and failed. I had a similar aileron crank failure on a Ultrastar in 1985 .. > Weld was good but the rotating tube wall stress cracked and failed. > > > First I have heard of this type failure in a rudder crank. That doesn't > mean much. > > > Axles are normally tubular. Looks like yours are the popular 5/8" OD > axles that use little ball bearings which cannot be adjusted. I upgraded > to 3/4" OD axles with tapered roller bearings after I lost a wheel at > Muncho Lake, BC, in 2000. Never had another problem with wheels, axles, > and gear legs. > > > Our MKIII aircraft are heavy when we strap in a couple husky guys, a full > load of fuel, and anything else we can stick in there. I think MATCO > advertises the 5/8" axles as 600 lbs static and 2000 lbs max. Most of us > exceed that number a great deal. If you land at 3 g's, that=99s 19 80 lbs. 4 > g's is 2400 lbs. See what I mean. That is if you and your airplane > weigh 600 lbs. 900 to 1000-1200 lbs is more like it. > > > I guarantee those wheels, axles, and bearings have been constantly > overstressed. I didn't realize that 14 years ago when I broke mine. > > > Sorry it happened. It always hurts to break our airplane. > > > john h > > mkIII > > Titus, Alabama > > > *From:* owner-kolb-list-server@matronics.com [mailto: > owner-kolb-list-server@matronics.com] *On Behalf Of *Brad Nation > *Sent:* Sunday, August 31, 2014 5:19 PM > *To:* Kolb-list > *Subject:* Kolb-List: Rudder Failure on my Xtra. > > > Kolbers, > > The good news is that no one was ingured and the aircraft damage was > relatively minor. It could have been a lot worse if it happened in the ai r. > > > Recently we had a taxi test in my Xtra with a once around the pattern and > shortly after landing the right rudder failed! Atfter a sharp left turn to > exit off the runway, without the benefit of a taxiway, the Xtra ending up > off the runway with both axels sheered off at the wheel and a bent right > wing tip. > > > After getting the plane back to the hanger I found that the rudder failur e > was caused by the weld failing between the upright square bar that connec ts > the rudder to the cables. I also noticed that the axel is hollow. Should > the axel be solid? > > > Have any of the Kolbers experienced this before and if so, any suggestion s > as to the cause of the failure and the best course of action, repair or > replace the failed part? > > > I have attached the photos of the failed part and the sheered axel. > > > Brad Nation > > MK III Xtra > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message kolb-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Kolb-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/kolb-list Browse Digests http://www.matronics.com/digest/kolb-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.