Homemade DPV

montyg

Should one even consider the Bosch GP750 motor? (as used in the Fallaron methinks)

I read that it's noisy, but it seems that's mostly because of the reduction gears.


rgds
monty

lizardland

Some ROV's have a compensation chamber, an oil filled piston with a diaphragm to adjust the oil volume to account for expansion/contraction. One benefit is that all your seals are low pressure as you have ambient pressure on the inside. Downside is that you can't have any unvented voids in any component or you'll get parts imploding or warping.

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rdmmdr

like lizard land said i know guys that have taken minnkotas to 500ft with the piston comp system, the trick is pwm motor controllers to give you the best battery life and making the housing that will not leak, the best that we came up with was some light wieght ss pressure vessels that we precharged to 200psi. Stainless steel sanitary clamps make for a great seal and go up to 12 inches dia can you say torpedo.
rick

Scuba_Vixen

[quote=Scuba Vixen
It depends a lot on where the motivation is coming from.

If you go the DIY route to try to save money, Forget It, .... it ain't gonna happen that way. .... at least not for anything you'd want to depend on


If the motivation is to build the best scooter that can be built, cost not withstanding, then the link Phi posted is testament to that.


The concept of the DIY scooter has been around a long time and many have tried it......

There's 2 basic ways to go, the submersible trolling motor and the Tekna/Mako kort nozzle system.

Trolling motor seals are not designed for depth, so they are only suitable for shallow use.

The T/M kort nozzle setup uses a mechanical seal which works well, even past 100m. It's also a more efficient thruster design.

Real world testing has shown that propeller RPM in the 800 to 1200 range is most suitable to DPV use, so you need to setup your power train design with that in mind.

The Mako uses a purposely built, 8 pole - permanent magnet motor, that runs about 850 rpm in stock form. (SS and Gavin use a rewind that runs about 200 rpm more) ... Most such motors are designed for much higher rpm and need gear reduction, which adds weight and complexity and Noise.

[SIZE=3]Unless you just like DIY projects, the $$$ spent versus "level of usefulness" ratio is usually not very favorable compared to buying a good second hand unit. [/size]
/quote]


I agree that there's all kinds of schemes that have been devised to overcome various problems, some of them quite exotic, keep in mind that we're relating to the realm of home built dive scooters here. Most home builders, (Doc Hammond excluded) have limited budgets, limited tooling, and limited engineering/design skills/experience.

To produce something workable with minimal redesigns, I stand by my original suggestion: "There's 2 basic ways to go, the submersible trolling motor and the Tekna/Mako kort nozzle system."

Successfully re-inventing the wheel doesn't come cheap. ..... And most DIY projects are begun with the intention of saving some $$$ over buying something ready made.

The last statement in the original post is the caveat not to loose track of.


Darlene



For those wondering what this Otto fuel stuff is:

Named after its inventor, Otto Reitlinger, Otto Fuel II consists of the nitrated ester explosive propellant propylene glycol dinitrate (PGDN), to which a desensitizer (dibutyl sebacate) and a stabilizer (2-nitrodiphenylamine) have been added. The chief component, propylene glycol dinitrate, accounts for approximately 75% of the mixture, while dibutyl sebacate and 2-nNamed after its inventor, Otto Reitlinger, Otto Fuel II consists of the nitrated ester explosive propellant propylene glycol dinitrate (PGDN), to which a desensitizer (dibutyl sebacate) and a stabilizer (2-nitrodiphenylamine) have been added. The chief component, propylene glycol dinitrate, accounts for approximately 75% of the mixture, while dibutyl sebacate and 2-nitrodiphenylamine account for approximately 23% and 2%, respectively.itrodiphenylamine account for approximately 23% and 2%, respectively. (thank you Wikipedia)

It's a monopropellant, which means it produces its own oxygen during combustion, but by itself, if burns fuel rich and requires additional oxidant to reach a stoichiometric combustion level. Hydroxyl amonium perchlorate is the oxidant of choice.


This stuff is so powerfull (energy density wise) that it propels a 4000 pound torpedo at 80 kts.

For additional info, check here:

http://www.marconi.com/Home/about_us...13n3s/p150.pdf


Darlene

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Hello Scuba_Vixen it appears that you have not posted on our forums in several weeks, why not take a few moments to ask a question, help provide a solution or just engage in a conversation with another member in any one of our forums?

fireman

So its basically slow burning rocket fuel, sign me up. How about a hydogen peroxide torpedo sort of thing. Like a rocket sled, push the button and go for a ride. One could make a small (canister light) emergency DPV--"get caught in a current, no problem, take your I'm a dumbass brand eDPV, with built in spare air and get 2 minutes of 10 knot safty" Patent pending LOL.

A while ago I got some Chinese knockoffs of a scooter from ebay for less than $100 each, yes they are junk, but they work and are kinda fun for buzzing around the quarry.

SimonK

Seem to going off at a tangent here. For the more advanced homebuilder, some hints and tips.

http://tinyurl.com/2h7k2x


Simon

fireman

Great link thanks. What are the options to seal the prop shaft. Also, how do the variable pitch props work.
Scuba Vixen, looks like a nice unit do you use it often.
Does the energy density of compressed gas come anywhere near Lead Acid batterys? Although I suppose one could deliver energy at a much faster rate with a pneumatic system.
Are there any internal combustion systems that a civilian could play with.

jaap

Kids stuff!

When I done embezzling enough Pu my scooter is going to run circles around those crude things...

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jeff h

Actually I built a couple of gavin clones for what I consider a very reasonable price (~$1500). The only catch was I had access to a full machine shop and it took about 80% of my free time for a couple of months (mostly because I'm not a machinist).

I put about $700 to $800 worth of materials into it. That included new batteries for 20 amp and 26 amp packs (B&B high rate/high discharge). The most expensive pc was a 12"x24"x4" pc of UHMW for the nose cones which cost ~ $250 (shipped).

I added a $700 Tekna (fast, had rewind and Al blades) and come up with one complete scooter with 20 and 26 amp packs and second scooter kit for around $1500.

Since then I've put about another $500 into a second motor, shroud, etc for the second kit (not together yet).

Anyhow, if time = money then it wasn't worth it but I enjoyed doing it and I can say I made my own scooter.

DepthCharge

Mind sharing where you are getting motors so cheap?

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Later,
John

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