OK, lets build a scooter....

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Mverick

Guest
Messages
646
Reaction score
1
Location
St. Louis
I got outbid on 2 Farallons I wanted. So I figure I'll build a Gavin copy.

For the rear engine compartment and Old Al80 cut in half. Machine the inside to fit an Oring at the edge.

Question. I've used packing to seal a shaft in my boat. But I know it won't hold 100 feet of pressure. How to seal the shaft into the hole coming out of the AL80's neck. It already has a nice thread to it. But how to seal it???

Thanks for any help....
 
Go there and search for Shaft Seals.

The pressure at 330' is ~150psi so the unbalanced shaft seals listed should be fine, especially since most are rated to 250psi.

For the al80, you will probably have to ditch the threads completely. I doubt you would be able to find a threaded seal insert (unless you made it).

The speed is basically RPM*circumference of the shaft. The rpm is very dependant on the selected prop and the motor.

I am still hunting for decent kort nozzle propellers. They are starting to put kort nozzles on some trawling motors, so they have to exist! Any ideas about a source? I have bought small (2-3") versions before but I lost the the info on the source.

BTW, it was interesting to see some magnetic coupling seals that completely isolates the internal shaft from the external. Technadyne uses this approach on their ROV thrusters. I wonder how much they actually cost... I.e. are they even practical for a scooter?

Also, www.epm.com has some good pics of the seals so you can see how they work. (choose mechanical seal)

Hope this helps.
 
Not trying to rain on your parade, but you can not copy a Gavin. All who have tried have failed. Yes you can get some of the parts, but the engine, how it is wound and the performance can not be duplicated. George keeps that to himself.
 
DIR RECDIVER,

Your statement is horse pucky. You can purchase a Mako motor for $600 (brand new) if you know the right person and get it rewound. Lots of people have copied these, lots of people are using these rewound motors in their Tekna's and Mako's. You need to get out of the assumption that George is a God.:bonk:
 
DIR Tec Diver once bubbled...
Not trying to rain on your parade, but you can not copy a Gavin. All who have tried have failed. Yes you can get some of the parts, but the engine, how it is wound and the performance can not be duplicated. George keeps that to himself.

Well if you'd of read the post, you'd see I was using a AL80 as part of the housing. Which like you said wouldn't be a Exact copy of a Gavin. I said copy, not exact copy.

And to be honest. They aren't using the Best motors for there scooters. There are much more efficient motors with longer run times on the same battery as there's. They took the easiest route by using what was already built. And adapting it to there use.

They didn't build a New, Superior, Scooter. They rebuilt a Mako to a superior design...

A Gavin is a great scooter though.....

DIR Tec Diver once bubbled...

Yes you can get some of the parts, but the engine, how it is wound and the performance can not be duplicated. George keeps that to himself.

This statement shows you know absolutely zero about the mechanics of a electric motor...

And George doesn't rewind the motors himself. So yep, somebody else does know.... And came up with it other then him. Since he isn't an electronics whiz. He's just a great very skilled diver....
 
KilgoreTrout once bubbled...


BTW, it was interesting to see some magnetic coupling seals that completely isolates the internal shaft from the external. Technadyne uses this approach on their ROV thrusters. I wonder how much they actually cost... I.e. are they even practical for a scooter?


We used them on our pumps for very corrosive materials. They didn't last 1 batch. But would be great for this. That pump cost around $50000. So I'm thinking that part would be around $5000... If so, it's a little pricey for me. They were cool though. It was a small pump too.... Ours got to hot and melted the whole assembly....
 
Did these things getting eaten? Was the material that corrosive? One question I am curious about is what kinds of materials are good for this. Any non-ferrous materials?

I guess these things have been around in pumps for a long time. Hermetically sealed, etc... We could use something similar with alot of the hydraulic pumps we use underwater...

I found other fun stuff, such as a motor using the same barrier. If you stop and think about it, it should be very easy to adapt a regular DC motor to this type of operation. The version I found is designed for industrial operations.

The body of the motor could spin, leaving the windings stationary relative to the system. Basically the principle is to hold the motor shaft and let the body spin. The main trick is to keep the wiring attached to the brushes separate from the spinning can.

You just design your propellers around a larger diameter hub (aka motor body). What you end up with is a simple, streamlined thruster. It's like making your prop hub the motor too. No bulky can attached and no need for seals.

Other benefits...

- If you jam your prop for a second, it just decouples the magnets and you don't burn or repeatedly chop anything.

- Depending on magnet polarity, you can avoid the need for any lubrication. I.e. there is no actual contact between the housing and the spinning hub.

- Oil filled housings don't introduce any more friction than regular motors.

- Friction and vibration virtually gone!

Etc, Etc, Etc...

Now all I need to do is sucker someone into paying me develop one o' these! Any takers?

Good Day.
 
The pump was teflon lined. It was used to produce PolyAluminumChloride. Reaction creates lots of heat and hydrogen gas. Top of reactor has a nitrogen blanket on it. To keep free Hydrogen from going to the atmosphere and potentialy Hyndenberg effect...

Both the impeller and pump housing were coated in Teflon. Completely sealed from the motor unit. The magnet would spin on the outside and turn the impeller on the inside. With the heat it got soft and ruptured the teflon seal on the magnet. And in turn ate the magnet. But it was spinning in the pump and destroyed the inside housing of the pump while it was getting eaten....

We have had pumps made of Hasteloy C that were Steam jacketed not last in applications. Bad engineering. From our own people. They don't listen...LOL

Magnetic coupler would work great. If I could find one for a resonable price it's the way to go. Spinning motor housing would add to many extra problems into the equation. It could be done. But alot of extra engineering to get around. More things to go wrong too....
 
Not for the DIY scootering kind for sure! Engineering would be involved...

It would be more suited to AUV propulsion where space and reliability are a premium.

AUVs are also platforms that depend heavily on engineering innovation.

The ChemE stuff is out o' my area... Interesting still, but not for me!
 
SCUBANARC

your reply was uncalled for.

The less you know about something the stronger your opinions are.

You obviously do not own a Gavin, you do not understand a Gavin, and do not know anything about a Gavin. I and many other people do. Your statements are also incorrect about the Gavin vs. Mako. It is not an opinion but a fact that no one has matched the performance, quality, and durability of a Gavin. If you feel otherwise post the data and prove it. I have tons of field trials with all kinds of scooters at my disposal.

By the way, I do not NEED to do anything you say, nor will I go down to your level and call you names. I hold George in the highest of respect, I know him well, have spent a lot of time talking with him, learning and listening. You don't know him, so please refrain belitteling one of the worlds top divers.

Also when I rec dive I am always DIR also, so your attempt of an insult calling me DIR Recdiver is happily accepted. It is my choice and I am proud of it.
 

Back
Top Bottom