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Rotax 912 crossover carburetor link

 
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ronlee



Joined: 25 Dec 2006
Posts: 141

PostPosted: Tue Feb 26, 2008 4:38 pm    Post subject: Rotax 912 crossover carburetor link Reply with quote

Has anyone put together some sort of crossover rod for linking the Rotax 912 carburetors together? This is not a new idea, as I have seen this sort of link between carburetors on other engines. I have mine working fine on my CH701, but must say it was a chore routing a cable to each carburetor, trying to keep them the same length so they advance properly, and making the whole mess look neat. If they were linked together by a rod of some sort and activated by one cable at one carburetor it sure would help cleaning up under the cowl. The carburetors  would probably stay synchronized forever..

Ron Lee
Tucson, AZ


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Gilles.Thesee(at)ac-greno
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PostPosted: Tue Feb 26, 2008 6:32 pm    Post subject: Rotax 912 crossover carburetor link Reply with quote

Hi Ron,

Quote:

The carburetors would probably stay synchronized forever..


That is, provided the carbs don't move relative to one another.

Best regards,
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Gilles
http://contrails.free.fr


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rholder(at)avnet.co.uk
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PostPosted: Wed Feb 27, 2008 12:55 am    Post subject: Rotax 912 crossover carburetor link Reply with quote

ronlee wrote:

Quote:
Has anyone put together some sort of crossover rod for
linking the Rotax 912 carburetors together? This is not
a new idea, as I have seen this sort of link between
carburetors on other engines. I have mine working fine
on my CH701, but must say it was a chore routing a
cable to each carburetor, trying to keep them the same
length so they advance properly, and making the whole
mess look neat. If they were linked together by a rod
of some sort and activated by one cable at one
carburetor it sure would help cleaning up under the
cowl. The carburetors would probably stay
synchronized forever..

I have spent a lot of time attempting this. The problem
is that the starboard carb is about an inch further
forward than the port one, so the normal (SU carburretor)
linkage doesn't work.

It might be possible with a linkage that is perpendicular
to the crankshaft with unequal length operating rods to
the carbs, but the geometry is tricky. I decided that the
geometry required the cross shaft to be in a certain place
which went straight through the inlet manifold (headers !)

In the interests of avoiding all those bends I designed a
connection box with a single cable from the throttle to a
box which connected the one cable to two much shorter ones
that went directly to the carbs. They went round a
cylinder. It was very smart, but the PFA didn't like it !

I am contemplating reducing the length of the cables
considerably (in the Europa they are over 6 foot long and
thread around a lot) making the cable run more direct so
less friction and less bends. I have spare cables from my
previous attempt to smoothen off the engine, so that will
be next !

The smoothness of the engine is very very dependent on the
balance of the carbs, and one flt on the cable adjustment
makes a big difference ! (Maybe I am over sensitive !)

Richard
G-OWWW
High Cross


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Float Flyr



Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

PostPosted: Wed Feb 27, 2008 6:21 am    Post subject: Rotax 912 crossover carburetor link Reply with quote

There are several cars etc that use linkages to join two or three carbs
together... but... Those carbs don’t have the diaphragms and additional
parts in them that the Bing 64 has. This I expect is why the 64 is mounted
on rubber and springs and as has been mentioned, that doesn't lend itself to
linkages. I'm sure you could make a more secure method of mounting the
carbs and then install links but that is going to be heavy.

Noel

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Noel Loveys
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PostPosted: Wed Feb 27, 2008 7:48 am    Post subject: Rotax 912 crossover carburetor link Reply with quote

For those interested in one solution to the linkage issue, check out Klaus's

http://www.utdallas.edu/~klaus/Airplane/airplane.html

George May
601XL 912s
Connect and share in new ways with Windows Live. Get it now! [quote][b]


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dcsfoto



Joined: 24 Aug 2006
Posts: 120

PostPosted: Wed Feb 27, 2008 10:46 am    Post subject: Re: Rotax 912 crossover carburetor link Reply with quote

I looked at the 601 setup,looks to me like when the engine vibrates the rods are attached to a linkage fixed to the firewall and will pull or push the carbs different .
My Kitfox 7 throttle is an aircraft throttle that is split,and each end is secured at the carb. each carb is moved the same.

why reinvent the wheel.

David Kitfox 3 and 7


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