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Posted by:
rojitha.g@gmail.com
Sun, 10/01/2017 - 8:21am

Bouyancy Engine

Hi, I am designing a drone that goes underwater to collect data such as PH, temperature and salinity for my senior design project in University. The main issue I’m facing is the bouyancy engine. The traditional way of using a long drive shaft to pull the shafts of the syringe takes way too much space. I came across your bouyancy engine and it seems to be the perfect solution. The acrylic tube I’m using for my drone is 4” OD and 3FT in length so it needs a lot of water to sink. The 150ml syringe you use won’t work especially since it can only take half of the capacity due to the drive shaft inside. 

Is there anyway I could get the solidworks files for the parts of the bouyancy engine so that I could scale it up to a large syringe? I’m looking to do the same thing for a 400ml syringe.

Also is there another way of doing this and saving space without doing it the traditional way?

Posted by:
Christopher Nunes
Christopher Nunes's picture
Thu, 10/12/2017 - 10:05pm

RE: Buoyancy Engine

Hi, 

You are correct that the little buoyancy engine will not sink much on its own, that is why the gliders are ballasted with steel bars to near neutral buoyancy with the engine half actuated. This allows the engine's small change in water volume to drive the glider up and down equally, with the proper ballasting you could sink anything!! But, having a large vehicle leaves a small force to fight a lot of inertia and body drag so I can see how it would accelerate slowly.

The easiest way to get a couple of extra mL out of the syringe would be to use the shorter lead spool plunger file in the SeaGlide Resources/Printed Parts/Pre release dropBox folder:

https://www.dropbox.com/sh/w2dqhubwyp2w8e1/AABW4JeuoDVwUjn5ch1M7sR1a/Pre...

Sorry, the SolidWorks parts are not available at the moment. On the topic of a larger syringe, I just wanted to warn you that the larger surface area of a larger diameter plunger will amplify the strain on your servo at depth. This is the limiting factor on max depth in many cases.

Another approach to this problem is to you use a small peristaltic pump. The pump can draw water in and out of a bladder/container inside the vehicle (making it heavier or lighter), or it can inflate and deflate an oil bladder on the outside of the vehicle.

Good Luck

Posted by:
rojitha.g@gmail.com
Thu, 11/09/2017 - 1:03am

Hi, thanks for your response!

Hi, thanks for your response! In regards to using a pump, what type of container do you think I should pump the water into? Do you have an amazon or eBay link to one? I believe I need a 1000ml capacity to sink it right now.

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