Questions about rear mounted carburetors.

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Mark D. Fain - 11 Jul 2004 05:22 GMT

On the engines that use the rear mounted carbs like the ZDZ and DA's:

1) I have seen pictures of rear carb engines mounted on flat ( no engine
box) firewalls where the carburetor appears to be directly open to the
interior of the fuselage. Is this correct, or is there some type of internal
carb box closing off direct access to the fuselage?

2) if the carb is open to the fuselage, how would you control any fuel
blowing out of the carb ( such as an over prime?) A fuel proofed balsa carb
box with an open top and a drain line in the floor venting overboard, maybe?

Thanks,

Mark D

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Philip Rawson - 11 Jul 2004 12:05 GMT

> On the engines that use the rear mounted carbs like the ZDZ and DA's:
>
> 1) I have seen pictures of rear carb engines mounted on flat ( no engine
> box) firewalls where the carburetor appears to be directly open to the
> interior of the fuselage. Is this correct,

That's how it's commonly done...

>or is there some type of internal
> carb box closing off direct access to the fuselage?

That could be done also...

> 2) if the carb is open to the fuselage, how would you control any fuel
> blowing out of the carb ( such as an over prime?) A fuel proofed balsa carb
> box with an open top and a drain line in the floor venting overboard, maybe?

In practice, little fuel gets out of the carb. Certainly not enough to need
a drain tube...It's enough to fuel proof the inside of the firewall/engine
box. It's not a bad idea to fit a trumpet also. When in storage, leave off
any hatches etc from the fuselage to allow the petrol fumes to escape.
This'll minimise the impact of the petrol fumes on the plastic parts in the
fuselage... a well known UK servo lead manufacturer has talked to me about
petrol fumes eventually degrading the plastic servo connectors that he
sells. Although this is a very long term thing, it's worth taking
precautions...

--
Philip Rawson

www.flymodels.co.uk

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Model Forum / Radio Controlled / Air Models / July 2004

Questions about rear mounted carburetors.