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? 2 speed automatic geerbox

Posted: Sun Jan 13, 2019 1:17 am
by ScottyB
Light sport aircraft are limited to ground ajustable propeller but....... If there was a 2 speed transmission with a governor to keep prop speed around 2700 rpm
In low gear with a ground adjustable prop over piched you could run up to Max rpmand have power to spare
Once up to air speed your automatic transmission would shift to high gear letting you back off on the throttle or cruise at 139 miles an hour
Transmission like this could be built to be about 25-30 lbs and remove your gear box that is from 21- to 40 lbs just a thought

Re: ? 2 speed automatic geerbox

Posted: Sun Jan 13, 2019 3:57 am
by bryancobb
In the mid 90's, I went to Sun-N-Fun and there was a WWI-type Experimental that had a Harley engine on it.
The builder chose to install the gearbox too. He would takeoff in low gear and climb steeply. Then he'd reduce his angle of climb and shift.
He changed gears 2 or 3 times in the same fashion as he gained altitude.

It was hilarious.

Re: ? 2 speed automatic geerbox

Posted: Sun Jan 13, 2019 9:19 am
by drseti
ScottyB wrote:Transmission like this could be built to be about 25-30 lbs and remove your gear box that is from 21- to 40 lbs just a thought


Scotty, I don't doubt that a variable transmission could be produced at 25-30 pounds, but you've been misinformed about the weight of what it would replace. The existing Rotax 912 series gearbox weighs in at around 9 pounds. The extra weight would be significant - but more important, with up to 20 more pounds right in the nose, thus would raise havoc with CG!

Nice concept though. ;)