---------------------------------------------------------- RotaxEngines-List Digest Archive --- Total Messages Posted Wed 12/26/07: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 05:34 AM - Replacing throttle return springs (Catz631@aol.com) 2. 05:54 AM - Re: Replacing throttle return springs (Gilles Thesee) 3. 06:54 AM - Re: Replacing throttle return springs (Roger Lee) 4. 11:06 AM - Re: Replacing throttle return springs (Thilo Kind) 5. 12:14 PM - Re: Replacing throttle return springs (Gilles Thesee) 6. 02:31 PM - Re: Replacing throttle return springs (Thilo Kind) 7. 03:32 PM - Re: Replacing throttle return springs (Dave Alberti) ________________________________ Message 1 _____________________________________ Time: 05:34:32 AM PST US From: Catz631@aol.com Subject: RotaxEngines-List: Replacing throttle return springs I own a Kitfox 4 with a Rotax 912UL .I was a recent purchaser of this aircraft and am trying to get to know the 912.It is a different 'animal" then the Lyc/Cont I am used to working on. (in fact I am going to Rotax 912 school in Jan) The throttle return springs on the Bing carbs are very strong and have been overiding the friction adjustment on my throttle no matter how hard I thighten them. It requires constant pull on the throttle to keep the throttle at idle. As a result.I went to a Vernier throttle which seems to have solved the problem as it will hold what I set.However, if I push the button the throttle immediately goes to the full power position. so I then installed weaker return springs and this seemed to solve the problem. One person I talked to told me to remove the springs completely but I didn't feel I should do this as the springs are needed,I think,In acheiving the full open position on the carb. Am I approaching this correctly ? I have had the engine quit on me several times during landing as it appears I am getting the idle back too low (around 1400 sometimes) At 1800 to 2000 rpm idle,this airplane is hard to get on the ground it just floats and floats. Any ideas would sure help. Thanks, Dick Maddux Rotax 912UL **************************************See AOL's top rated recipes (http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004) ________________________________ Message 2 _____________________________________ Time: 05:54:29 AM PST US From: Gilles Thesee Subject: Re: RotaxEngines-List: Replacing throttle return springs Catz631@aol.com a crit : > One person I talked to told me to remove the springs completely but I > didn't feel I should do this as the springs are needed,I think,In > acheiving the full open position on the carb. > The springs are needed when you use a flexible throttle cable. If you are using a rigid push-pull cable, things are different. Another approach would be to modifiy your throttle friction. The diameter/leverage must be sufficient to ensure proper friction. > I have had the engine quit on me several times during landing as it > appears I am getting the idle back too low (around 1400 sometimes) At > 1800 to 2000 rpm idle,this airplane is hard to get on the Rotax advises 1600-1800. Try 1600, then ;-) BTW, do you have a positive idle stop on the throttle lever/vernier, as advised by Rotax ? One must not strain the carb stops. Regards, -- Gilles Thesee Grenoble, France http://contrails.free.fr ________________________________ Message 3 _____________________________________ Time: 06:54:38 AM PST US Subject: RotaxEngines-List: Re: Replacing throttle return springs From: "Roger Lee" Hi Dick, You should have the springs. They are there for a couple of reasons. To make sure if you have a throttle cable failure the carbs will open full throttle and let you fly somewhere safe before you have to shut the engine down to land. It keeps constant pressure on each carb to help for equal opening when using the stranded type throttle cable. Gilles is right you need the springs and you should be able to tighten the throttle linkage so it has enough friction to over come the spring tension with out any problems. You said your plane floats, compared to what. All planes have different landing characteristics. I have a Flight Design CT and that really feels like it floats compared to other planes and lands quick compared to let's say a glider or long wing plane. I doesn't really float bad, but different from what you are used to. Your idle should be up to at least 1700, but better at 1800 rpm because of the vibration and pulsing of the engine on the gear box. This is a Rotax recommendation. Maybe you could use more flaps on landing to land a little quicker? Slower approach? -------- Roger Lee Tucson, Az. Read this topic online here: http://forums.matronics.com/viewtopic.php?p=154313#154313 ________________________________ Message 4 _____________________________________ Time: 11:06:06 AM PST US From: "Thilo Kind" Subject: Re: RotaxEngines-List: Replacing throttle return springs Hi Dick, 1400 RPM idle is too low. Rotax recommends something like 1800 at idle. Also, the sprigs should stay on. Their purpose is to open the throttle in case of a breakage in the throttle linkage. There is at least one report in the archives about a gentleman who also removed / replaced the springs with disasterous results... Thilo -------- Original-Nachricht -------- > Datum: Wed, 26 Dec 2007 08:31:01 EST > Von: Catz631@aol.com > An: rotaxengines-list@matronics.com > Betreff: RotaxEngines-List: Replacing throttle return springs > I own a Kitfox 4 with a Rotax 912UL .I was a recent purchaser of this > aircraft and am trying to get to know the 912.It is a different 'animal" > then the > Lyc/Cont I am used to working on. (in fact I am going to Rotax 912 school > in Jan) > The throttle return springs on the Bing carbs are very strong and have > been > overiding the friction adjustment on my throttle no matter how hard I > thighten > them. It requires constant pull on the throttle to keep the throttle at > idle. > As a result.I went to a Vernier throttle which seems to have solved the > problem as it will hold what I set.However, if I push the button the > throttle > immediately goes to the full power position. so I then installed weaker > return > springs and this seemed to solve the problem. One person I talked to told > me to > remove the springs completely but I didn't feel I should do this as the > springs are needed,I think,In acheiving the full open position on the > carb. > Am I approaching this correctly ? > I have had the engine quit on me several times during landing as it > appears > I am getting the idle back too low (around 1400 sometimes) At 1800 to 2000 > rpm idle,this airplane is hard to get on the ground it just floats and > floats. > Any ideas would sure help. > Thanks, > Dick Maddux > Rotax 912UL > > > > **************************************See AOL's top rated recipes > (http://food.aol.com/top-rated-recipes?NCID=aoltop00030000000004) -- GMX FreeMail: 1 GB Postfach, 5 E-Mail-Adressen, 10 Free SMS. Alle Infos und kostenlose Anmeldung: http://www.gmx.net/de/go/freemail ________________________________ Message 5 _____________________________________ Time: 12:14:40 PM PST US From: Gilles Thesee Subject: Re: RotaxEngines-List: Replacing throttle return springs Thilo Kind a crit : > Also, the sprigs should stay on. Their purpose is to open the throttle in case of a breakage in the throttle linkage. There is at least one report in the archives about a gentleman who also removed / replaced the springs with disasterous results... > Thilo, The springs are there because many builders use *FLEXIBLE* cables. This is common practice in the ultralight community, but it has some drawbacks. Sometimes badly routed cables bind between throttle lever and cable outer case, leaving the engine at idle. That is because only the spring actuate the throttles at the carbs. Any undue friction in the cables leaves the pilot helpless. On the contrary, no problem at all when one use a push-pull cable, like in most Lyco-Conti. This gives the pilot a positive action on the trhottles. In this case, the springs *may* stay in, but are not mandatory. Most airplanes don't have one. Best regards, -- Gilles http://contrails.free.fr ________________________________ Message 6 _____________________________________ Time: 02:31:43 PM PST US From: "Thilo Kind" Subject: Re: RotaxEngines-List: Replacing throttle return springs Hi Gilles, one very important function of the springs is to open the throttle fully in case of a breakup in the throttle linkage. This will ensure that the engine keeps running at max throttle and theplane thus is still flyable. I know of at least one case (should be in the archives somehwere) where a guy removed the springs for the reason you mentioned, lost the throttle linkage in flight, and the throttles on both carbs closed (due to engine vibrations). Very uncomfortable during take-off.... I highly recommed to leave the springs on and play with the friction of the throttle linkage instead. Thilo -------- Original-Nachricht -------- > Datum: Wed, 26 Dec 2007 20:19:33 +0100 > Von: Gilles Thesee > An: rotaxengines-list@matronics.com > Betreff: Re: RotaxEngines-List: Replacing throttle return springs > > > Thilo Kind a crit : > > Also, the sprigs should stay on. Their purpose is to open the throttle > in case of a breakage in the throttle linkage. There is at least one report > in the archives about a gentleman who also removed / replaced the springs > with disasterous results... > > > Thilo, > > The springs are there because many builders use *FLEXIBLE* cables. This > is common practice in the ultralight community, but it has some > drawbacks. Sometimes badly routed cables bind between throttle lever and > cable outer case, leaving the engine at idle. That is because only the > spring actuate the throttles at the carbs. Any undue friction in the > cables leaves the pilot helpless. > > On the contrary, no problem at all when one use a push-pull cable, like > in most Lyco-Conti. This gives the pilot a positive action on the > trhottles. In this case, the springs *may* stay in, but are not > mandatory. Most airplanes don't have one. > > Best regards, > -- > Gilles > http://contrails.free.fr > > > > > -- GMX FreeMail: 1 GB Postfach, 5 E-Mail-Adressen, 10 Free SMS. Alle Infos und kostenlose Anmeldung: http://www.gmx.net/de/go/freemail ________________________________ Message 7 _____________________________________ Time: 03:32:42 PM PST US From: "Dave Alberti" Subject: Re: RotaxEngines-List: Replacing throttle return springs I know of 2 planes that lost throttle control with the solid cables on certificated airplanes so nothing about the throttle system is fool proof. Design for the worst case scenario for whatever cables you use but keep it simple! ----- Original Message ----- From: "Gilles Thesee" Sent: Wednesday, December 26, 2007 1:19 PM Subject: Re: RotaxEngines-List: Replacing throttle return springs > > > Thilo Kind a crit : >> Also, the sprigs should stay on. Their purpose is to open the throttle in >> case of a breakage in the throttle linkage. There is at least one report >> in the archives about a gentleman who also removed / replaced the springs >> with disasterous results... >> > Thilo, > > The springs are there because many builders use *FLEXIBLE* cables. This is > common practice in the ultralight community, but it has some drawbacks. > Sometimes badly routed cables bind between throttle lever and cable outer > case, leaving the engine at idle. That is because only the spring actuate > the throttles at the carbs. Any undue friction in the cables leaves the > pilot helpless. > > On the contrary, no problem at all when one use a push-pull cable, like in > most Lyco-Conti. This gives the pilot a positive action on the trhottles. > In this case, the springs *may* stay in, but are not mandatory. Most > airplanes don't have one. > > Best regards, > -- > Gilles > http://contrails.free.fr > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rotaxengines-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RotaxEngines-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/rotaxengines-list Browse Digests http://www.matronics.com/digest/rotaxengines-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.