Gearbox in a Twin Cat?

[Espresso]

I was just curious if the use of a gearbox was ever common in a twin cat build or even a twin powered mono (45"-50" size)? Is it possible to setup a counter rotating gear box linked to a motor and dual flex cables? What are the pros/cons and limitations that doesn't make this a popular choice?

I would assume such a setup would require a slightly more powerful motor but the weight savings of a gearbox could limit Lipo and an additional motor weight? Can a gearbox not handle the RPMs in a boat setup? Just looking for some info.

[Fluid]

You will have problems finding a twin output gearbox which will handle BL power. Single gearboxes used to be common but today the choices are limited.

[mtbenjamin77]

Its my understanding that a direct straight drive is the most efficient. Gears just add drag. The motors we use nowadays can swing good sized props so there's no need for gears boxes. I've considered building a drag hydro with a single motor and a dual CR gear box to mimic the real drag boats, but's it just makes more sense to have two CR motors and drive lines.

[mtbenjamin77]

I've also been told that the most efficient direct driveline is a solid shaft over the flex shaft. I believe the real unlimited hydros use solid shafts.

[egneg]

I've also been told that the most efficient direct driveline is a solid shaft over the flex shaft. I believe the real unlimited hydros use solid shafts.

They have to ... there is not any other that can handle the torque at the start.

[Fluid]

If full scale unlimiteds could use a flex shaft they would! The solid shaft has less parasitic drag but the flex is more efficient because the prop thrust is directed where it needs to be - straight back instead of downwards. Much more efficient in fact.





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[Espresso]

Good info guys. Appreciate it.

Its my understanding that a direct straight drive is the most efficient. Gears just add drag. The motors we use nowadays can swing good sized props so there's no need for gears boxes. I've considered building a drag hydro with a single motor and a dual CR gear box to mimic the real drag boats, but's it just makes more sense to have two CR motors and drive lines.

I know it's less efficient. Running twin motors doesn't add much weight instead of having a single larger motor + gearbox. Having another ESC also isn't that heavy. The weight savings I figured would come from the Lipos. Adding another 8S or 10S 2P brick can be heavy.