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
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| Subject: | 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
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Message 2
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| Subject: | Re: 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
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| Subject: | Re: Replacing throttle return springs |
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
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| Subject: | Re: 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)
--
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Message 5
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| Subject: | Re: 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
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| Subject: | Re: 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 <Gilles.Thesee@ac-grenoble.fr>
> An: rotaxengines-list@matronics.com
> Betreff: Re: RotaxEngines-List: Replacing throttle return springs
> <Gilles.Thesee@ac-grenoble.fr>
>
> 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
>
>
>
>
>
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Message 7
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| Subject: | Re: 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" <Gilles.Thesee@ac-grenoble.fr>
Sent: Wednesday, December 26, 2007 1:19 PM
Subject: Re: RotaxEngines-List: Replacing throttle return springs
> <Gilles.Thesee@ac-grenoble.fr>
>
> 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
>
>
>
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