Balance tube size

Roger Lee wrote:

It just isn’t necessary. I would like to think that Rotax over the years has tested things like this. May someone from Rotax here will respond.

Definitely. If a larger balance tube smoothed out carb unbalance, Rotax would have discovered and implemented long ago.

I have no doubt that Rotax considers this an acceptable solution within the design constraints they had.  Depending on what those constraints were, it might not be the best solution for power or smoothness.  There's always room for improvement, though I have no proof this would actually be an improvement.  I'd also like to believe Rotax knows best, but we can't be afraid to question that assumption.  Trust but verify :-)

Cheers,

Rusty

This is a great conversation that takes me back to the days of hot rodding cars. There was always some new mod to try out, and the prospect of that incremental performance increase was ever-present.  Having worked on engines most of my life, I can count on one hand the times when an aftermarket part or modification actually worked better overall than the factory designed part.  Sure, you put in an aftermarket cam and headers and you might get a modest high RPM power increase, but now the car won't idle smoothly or produce enough vacuum to properly operate the brake booster, and your headers keep getting smashed on speed bumps!  Still, it was great fun when you stomped the go pedal!

Most all mechanical design is a compromise between performance, economy and reliability.  And be it an automotive engine or aircraft engine, the factory usually has it nailed after producing thousands of units. Maybe we just want to believe that a small company or an individual, with almost no R&D budget, can out-think a company with a multi-million dollar R&D budget, but that is a rare occurrence.  Its in our nature to try to improve on things, but I draw the line at tampering with my aircraft engine.    

There is a very long thread about exactly this idea on the General Tech area. I tried to bring it to the top of the list with a new post but it didn't work. Search on that area for "balance tube" and you will see 16 pages of discussion. 

Alan 

I did a lot of searching, and read the other thread before posting this one.  It was 6 years old, so I figured I'd let it rest in peace :-)

If I end up trying this, I'll do it in such a way to allow me to try various size tubes from the original to maybe 1".  Of course even if it works, no one will believe me :-)

Cheers,

Rusty