Need some advice

[Guest]

Hey guys I need help on two quick things.
I am a nurse not an engineer.
I'm building a sub from scratch and amazon for the challenge and to get my brain off of covid.
Mostly printing with 3d printer. So far its coming along great.
1. I am going blind on most of this and just learning as I go. the entire electronics system just had its first test and works. But the peristaltic pump I'm using is slow as molasses. It took 10 min to get 225 mls into the ballast. Is this normal? I'm wiling to buy a more powerful pump but I'd need it no bigger than 3 inches. The pump says 5000rpm on 12volt. No way was it going that fast.
2. A lot of this I'm building as I go. The hull is next. Its based off of a video game and was downloaded. It will be anywhere from 30 to 40 inches long. 5 inches wide I don't know how big my ballast will have to be. I thought 250ml would be more than enough especially if I trim it to sit low. I know! it's impossible to tell me with out knowing weight, water displacement, size and on and on. But does anyone have a ballpark I should aim for?
And while I'm here what size propeller should I be looking at?
Any advice is always appreciated. And when this thing is running I'll be posting a video and you better believe I'll be thanking this group first and foremost.
Mark
OH!!! AND MY WTC IS WATER TIGHT!!!!! Man did I celebrate when I got that working!

[crueby]

Great on the WTC! For the pump, was the battery charged? If run down the speed would be way off, check with a voltmeter while running if you have one. Leak in a hose connection, not primed? Does the pump say what current it will draw?

[Guest]

No it was a cheap pump. 12volt 5000 rpm. I have a volt meter. I'll check that out. Pump was primed. I hate figuring out how to read draw. Its like greek to me. Well youtube here I come!!!

[bob_eissler]

And that is why you don't see peristaltic pumps used very often. They are always slow.

[bob_eissler]

The weight of the water in the ballast tank has to equal the weight of the part of the sub you want to have above the water line when surfaced.

[greg w]

The pumps are usually rated in ml/min. That would give an approximate fill depending on your voltage

[crueby]

No it was a cheap pump. 12volt 5000 rpm. I have a volt meter. I'll check that out. Pump was primed. I hate figuring out how to read draw. Its like greek to me. Well youtube here I come!!!

Just check the voltage on the battery with/without the pump running, will give you a good read on whether the problem is the battery or not. If the voltage drops way off when running, the battery is not charged or no good.

I remember the peristaltic pumps we used in printers for moving ink, as Bob says they are usually very low liquid flow, they only move a little bit per revolution.