Ballast shifting

[redboat219]

Has anyone tried internal mass (ballast) shifting for pitch control?
I reckon it's good for something like the Moebius Flying sub.

[Albacore 569]

Its interesting idea for some subjects. The shape, the moment arm (pitch) longitudinally (fore and aft), and the scale speeds expected are the considerations IMO.

A 'flying sub' (VTTBS) in my opinion doesn't need a weight or ballast shifting for pitch. it would respond too slow and motors turning waste too much precious battery energy.

The flying sub is best (as demonstrated in model videos) as a dynamic diver, with near neutral or slightly positivity buoyant and use thrust vectoring for pitch and yaw because its 'fly's'

A model that might benefit more is a 'Denice'.- Cousteau's Surcoupé. It is very stationery and moves so deliberately slow if operated at scale speeds. It could use a tiny worm gear to pitch ever so slightly. (depending on the model's size maybe as little as an inch off each way of the center of gravity/buoyancy). But it may be over engineering? Its shape makes it have such a short moment arm to play with pitch.

The real submarine used weight shifting for pitch, pumping mercury between two sealed reservoirs fore and aft.

But for a flying sub?. Sure,you need it?

[MFR1964]

I'm using a balance weight in my type VII, this is done to keep the boat balanced during the shooting of my torps.
Each torp is trimmed slightly positive for easy retreval, so shooting them takes the boat off balance.
This weight is propelled by a spindle which on his turn is coupled at the levelkeeper of my boat.
I'ts not intended to use for pitch control, by flipping a switch i can activade this system.
You can use it also when the boat is submerged and steady at one spot to get the balance right

Manfred.

[Subculture]

You can just use a normal servo to shove the battery fore and aft, very quick. Sort of thing that wouldn't be practical in a fullsize craft, but you can get away with in a model.

[redboat219]

Turns out Maximus Modellbau has such a system.
Pitch control is brisk.

[redboat219]

1 use I see is as alternative to David's propeller pitching mechanism for the Disney Nautilus.

[Subculture]

It won't react the same.

[RCSubGuy]

Ballast shift would be for trim modification, not for pitch authority underway. Two different critters altogether.

[redboat219]

Ballast shift would be for trim modification, not for pitch authority underway. Two different critters altogether.

I'll take it under advisement.