OK, lets build a scooter....

[Mverick]

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....

[KilgoreTrout]

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.

[DIR Tec Diver]

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.

[JamieZ]

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:

[Mverick]

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....

[Mverick]

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....

[KilgoreTrout]

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.

[Mverick]

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....

[KilgoreTrout]

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!

[DIR Tec Diver]

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.

[blackice]

to neither pass judgement on a Gavin Scooter or the DIY alternative ....

I would sooo love to have access to a scooter, and given the choice a Gavin would be the preference and they have the history / experience / track record of achieving the amazing.

But the idea of owning a scooter is way cool, but it's an expensive toy! or a complex tool, depending on which way you look at it.

Like any diving equipment, the main thing to ensure is that it will do what you intend it to, if that is assist you out of a 500m deep tunnel or move around coral reefs with easy, I feel the main thought should be to ensure that it is tested and works.

It should be adding to the pleaseure of the diving experience not being a distracting worry.

Enjoy diving - no matter where it leads you.

[Windwalker]

Hiya, I know very little about this subject, however I noticed a couple of sites that had "Plans" to build your own DPV and got to thinking, So I dropped by the scubaboard, and low and behold someone is already trying to do their own.

I was just wondering what the stats of said motor would be? Would a High Torque Low output be preferred to a low torque high output motor? For example, Would a 550 inchpound motor chuggin at 2000 rpm be too fast with not enough torque? (These are the specs of a Dewalt Drill, Small motor Planetary gear arrangement, variable speed setting low and high, long runtimes on a small battery)
I looked online for kort nozzles and found a wealth of information, none of it usefull.. :D I guess the question of Motor power really is governed by what kinda prop is being drivin.

Sorry to butt in, hope not to offend with my ignorance.:idea:

[Windwalker]

What about using a Trolling motor? They are already sealed with props and all, they can be got on Ebay for under $100 and come in many ranges of Thrust from 20 - 107 pounds. From what I have been seeing, Most dive scooters have between 20-40 pounds of thrust. That means all you would have to do is buiild a battery compartment and controls.

Just a idea

[H2OHead]

I am starting to get nauseous every time someone mentions _IR. The blind faith that people have in someone is amazing and quite reminiscent of back when Jim Jones was in the Kool-Aid business. Just as that “H” company isn’t the only place on the planet that makes filaments glow using a battery, the Gavins aren’t exempt from competition. I think it’s just a supply and demand thing. The Gavins are certainly considered top of the line by many (non _IR folks too I suppose), but scooters are quite expensive no matter who makes them and there just isn’t nearly the demand for them that there is in the other aspects of the diving industry. I say go for it. Try and copy the thing if you want. As for the motor problem you’re having. Go in on a Gavin motor and take it to a motor shop and get the skinny. If you have trouble getting a motor from Irvine, play to his emotion. The guy is 100% hothead and as arrogant as the day is long. Tell him you are going to dissect his motor, get it duplicated with improvements, for half the cost he gets them done for, and there’s nothing he can do to stop you. He’s sure to get mad and send you one for free.

[jonnythan]

H2OHead once bubbled...
I am starting to get nauseous every time someone mentions _IR. The blind faith that people have in someone is amazing and quite reminiscent of back when Jim Jones was in the Kool-Aid business. Just as that “H” company isn’t the only place on the planet that makes filaments glow using a battery, the Gavins aren’t exempt from competition.

Blah blah blah. *No one* at all makes these decisions on "blind faith." There is a real thoguht process and real decisions and intense debate behind every single gear choice. Look around the board, all the arguments are there. I've never seen a thread that says "well George says to wear a harness so I do." There are an a** ton of threads debating the merits of a bp with wings, or a long hose, or which tanks to have, or whatever. There are really fantastic reasons behind all of it. I challenge you to think so deeply about your own gear.

Seriously, do some searches on the board. All this DIR stuff is extremely well thought out by everyone who pays attention.

[H2OHead]

jonnythan once bubbled...
Blah blah blah.

The expected conditioned response, I see you've memorized your handbook.

The blind faith reference is for the scooter portion of this scooter thread and refers to blindly following a guy who says nobody can duplicate the performance of the rewound motor used in the scooter. To that I say, “unless we’ve issued a patent for the electron and magnetic lines of flux, I will have to disagree”.

The Gavin motor may very well be the most efficient electrical motor ever developed and the envy of all who know of its existence, but I am reserving a small bit of skepticism for myself there. George, undoubtedly the foremost authority on atomic particles and how they interact, may have solved all known issues related to electrical motor design and discovered the key to perpetual motion, but I doubt it.

Not as a means of flattery, but as a means of economics; I suggested buying a Gavin motor and using it as a starting point. This is common in industry where development of products to compete with an existing product line is the goal. I’d say building a scooter comparable in every way to one commercially available, but with far less monetary outlay is one of the goals when homebuilding. Building something in a place other than Irivne’s garage doesn’t necessarily make it inferior, but I won’t continue to try to convince you of that since you seem to have already taken your vow. If you’d put down your checkbook at some point and put on your thinking cap, you’d eventually realize that safe diving can actually occur in the absence of logos like Gavin and Halcyon. I don’t use a Halcyon brand HID light, I actually put a lot of time, effort, and ability into designing my own and built a couple so I’m not on the short list when DIR Christmas party invitations are sent out, but I think I’m actually a better person for that.

I am all for safer diving and collaboration on how to achieve that, but I won’t be sold on the notion that I’m not intelligent enough think “Right” without being told how to do that.

[PhotoTJ]

See my related post this thread (http://www.scubaboard.com/showthread.php?s=&threadid=31908&perpage=15&display=&pagenumber=3)

I am glad I am not the only one who doesn't follow the _IR path!:D

[GlockDiver]

This is just a thought, but would it be possible to modify an AL80 to have a valve on it such that it could be controlled via a throttle? Thus the thrust would come from escaping air from the bottle? Is this feasible?

[Windwalker]

I think escaping air itself would not be that effecient, however harnessing it for a pneumatic Engine could.. Something like this.. http://quasiturbine.promci.qc.ca/QTPneumatique.html

Also, I remember Lego has some Pneumatic engines. I am not saying build a scooter from lego's but, they are pretty buff for their small size and low air requirments.

What about using a Liquid Gas cylinder, that would give you more energy density for expansion (Co2) but the problem would be in keeping it warm and not frozen.

[Aquamaniac]

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.
Do you a deal Mr DIR Tec Diver.
I will build an exact replica of a Gavin.
Once its complete you can dismantle it, test drive it, dyno test it, whatever you like.
If at the end of your examination, you can tell me one thing thats differant, or not as good as the Gavin, You will foot the bill.
If I fail, you can have all of my dive gear, including the copied Gavin.
Looking forward to your response
Dave

[Windwalker]

Regarding using an Airtank as a "Powersource" I had a cool idea to use an AirDrill or Power Grinder.. They average 3cfm @90PSI, for 22,000RPM You could probably knock the PSI down using a regulator and get better gas mileage. Also a Stepdown gear could give better torque and drop the hideously high rpm. Off a AL80 you could get about 20minutes of continous operation, Possibly. or 40 minutes from a 120. Recharges would be quick. and if something happened you could have another airsource there.

[ShoalDiverSA]

Aquamaniac,

I hope that DIR Tec Diver is up to the challenge! It would be great to see a Gavin replica being built - especially if you furnish plans at the end of the exercise :mean: .

I am also attempting to make a very similar scooter to the Gavin myself. At the moment, I am trying to source the motor. I have looked into a couple of options, but a trolling motor still seems to be the best idea. I am looking for a second-hand motor ideally (to keep costs down!).

What I would like to know is: do you have information on the specifications of the Gavin motor that would guide the search for an ideal motor?

I'm looking for power (kW or hp) or current - even thrust would be helpful (though this is dependent on propeller pitch). Thrust will be meaningful if I can get hold of a trolling motor and matching propeller, because these are rated in lb of thrust. From what I have gathered from my research is that the optimal speed of the motor is in the range of 1000rpm or slightly less.

Right now I am flying blind, but I have faith in the ability of *mere mortals* to manufacture a "Gavin":D

Windwalker, great idea! Are you going to build a prototype? Pneumatics is not my forte!

Cheers,

Andrew

[Scuba_Vixen]

Air motors are only efficient at outrageous RPMs. (much like turbines and turbo chargers) They have about zip for starting torque, and often can't start under load. You'd need an incredible gear train to get one down below 1000RPM, without a Lot of loss. maybe a planetary arrangement. A regulator that will break 3000# down to several scfm at 125#, and do it while compensating for increased presure at depth isn't listed in the Mc Master Carr catalog. You'd need one way more than 3 cfm to move a scooter anyway.

Now maybe a hydrogen peroxide propulsion system might work. Those old WW2 torpedos moved along pretty well, lol

Interesting thought though, I'd stay with electric.

Darlene

[Aquamaniac]

ShoalDiverSA once bubbled...
Aquamaniac,

I hope that DIR Tec Diver is up to the challenge! It would be great to see a Gavin replica being built - especially if you furnish plans at the end of the exercise :mean: .

I am also attempting to make a very similar scooter to the Gavin myself. At the moment, I am trying to source the motor. I have looked into a couple of options, but a trolling motor still seems to be the best idea. I am looking for a second-hand motor ideally (to keep costs down!).

What I would like to know is: do you have information on the specifications of the Gavin motor that would guide the search for an ideal motor?

I'm looking for power (kW or hp) or current - even thrust would be helpful (though this is dependent on propeller pitch). Thrust will be meaningful if I can get hold of a trolling motor and matching propeller, because these are rated in lb of thrust. From what I have gathered from my research is that the optimal speed of the motor is in the range of 1000rpm or slightly less.

Right now I am flying blind, but I have faith in the ability of *mere mortals* to manufacture a "Gavin":D

Windwalker, great idea! Are you going to build a prototype? Pneumatics is not my forte!

Cheers,

Andrew
Andrew

All Gavins use a Mako/Voyager motor. George buys old Makos, rewinds them, and puts them in his scooters. He may even be buying them direct from Oceanic now.

The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts

Now it must be noted that George rewinds the motors.
How is a mystery, but from what I have learned so far, I believe he is changing the number of poles, to increase the speed, without reducing torque.
New Gavs run around 200 ft/min

At this point, im not completely sure, But I think an off the shelf Mako runs 600 RPM, and the rewound version runs about 1000RPM

Being an ex motor winder, Im doing everything i can to work out the most efficient, and fastest winding data!

As soon as I work it out, Ill be sure to publish the results.

The biggest issue with trolling motors, is that you will also need to build a clutch and Variable pitch Prop. This can be cost ineffective when you can buy a used mako, with all those bits for around $700.00.

Dave

[Aquamaniac]

Dont rule out these kind of options either........

Would need modifying, but can be a good starting point.
Clutches can be machined up, and the seals are off the shelf. All you need is the Variable Prop.

http://www.grainger.com/Grainger/motor_guide.jsp?a3=24VDC&a2=1

[Windwalker]

Someone here mentioned using Air for Propulsion, I thought about the regulator problem.. Couldn't a regular first stage be used? as it keeps the LP hose down around 150-200psi.... the LP hose would connect up to the Airtool. You are right about the speed problem.. Some wierd type of gear setup would be needed and I think that is the Achilles heel of trying to use an Air Turbine in this application.. The other one is keeping it dry. I don't think starting would be a problem because (if you managed to solve the gear problem) the resistance against the motor would be pretty low.

I am going to be building my own "electric" motor DPV. I purchased the "ScubaTow Torpedo" plans. I wanted to see if there was anything that I was not "getting." I am probably going to use an Metal hull and not a PVC one. This is going to screw up the ballast characteristics, so I am going to compensate with a sliding battery compartment. We shall see. I am still in the design phase.

I am also looking into a 74-80# Trolling motor for my application as well. The Motors alone can be purchased as replacements from West Marine (so I'm Told) cheaper then a Whole Trolling motor setup. Also, I was reading that Higher Voltage Motors require less battery drain and will work longer on smaller batteries.. For example a 12V .025HP motor would have a 2/3 less runtime then a 24V .025HP motor. Also I am thinking of checking out the characteristics of a 400V AC motor. (Aviation grade) Would the loss of the transformer negate the effeciency of the system. Also Higher Voltage AC motors tend to be smaller then the DC counterpart. I will have to talk to my EE dad on that one.

I'm Not a Tec Diver, so this is more just for fun then anything serious. If it Pukes out on me, I won't be a mile into a cave. With that said, I don't want it to puke out on me at 1000 feet (not saying that I am going down that far) so its going to be "Beefy"

First prototype will only be good to 250FSW due to the use of a Trolling motor (and that is where their shaft seals seem to rated at)

[Aquamaniac]

Windwalker once bubbled...
Also I am thinking of checking out the characteristics of a 400V AC motor. (Aviation grade) Would the loss of the transformer negate the effeciency of the system. Also Higher Voltage AC motors tend to be smaller then the DC counterpart.
True, but how would you power the AC motor?

If you were to use batteries, you would not only need to step it up, but invert it to AC.
The losses, complexity and cost would far outweight the benifits.

Dave

[Windwalker]

Nah.. I have a circuit design for High Voltage, It requires me to wind my on Transformer, But the Inverter / AC-DC is a very simple design and about 80%-90% efficient, and can be done solid state.

HID lights require a similar setup, except they need a starting voltage in the thousands of volts. This is no more then a Ballast modification.

I have not settled on a 400V motor. My first design is going to be a Trolling motor.

Here in Oregon there is a Surplus store called Wacky Willies, They sell all sorts of Really Neatsy Keen Motors for under $10. Most of these motors would go for more then $300 new.

I do not plan on investing lots-o-Cash on the 400V experiment.

[Scuba_Vixen]

Aside from a lot of technical reasons why the ac motor system isn't the better choice, 400 Volts and Water ought not to be anywhere near ech other. I'll bet they are not actually 400 volt, but 400 cycle (hertz). That was pretty common in aircraft since inductors (that means transformers and motors) for higher frequencies are much smaller and lighter than for 60 cycles. If you use a trolling motor, use an adjustable prop. Some motors have 2 or 3 speeds, but to do it, they have series dropping coils (in the motor housing at the brush end) to effect this. That just turns some batter energy to heat, instead of motion on the lower speeds.

Anyway, good luck


Darlene

[Windwalker]

Yes, You are right, it is 400Hz. My memory is failing me.. However, It would not be any less zap then getting hit by a HID canister light. (those things can run into the thousands of volts) :D

Good advice on the Trolling motor!
Thanks!

[oxyhacker]

Anyone thinking about using a trolling motor should be aware that they tend to be high speed/low torque motors, which are the opposite of what you want for towing a diver - a diver has a lot of drag compared to your average bass boat, so a bigger, slower moving prop is desirable. So they are usually not as efficient when used on a DPV as a purpose-built high torque motor like the Mako.

Scubapro used what appeared to be a standard trolling motor powerhead made by sister company MinnKota on the Sea Shuttle DPV, which was rated for 180'. This led a lot of people into thinking a trolling motor would work just fine - not exactly so, since it turns out the Sea Shuttle motor was specially made for SP, and had a set of planetary reduction gears sandwiched into the case, a special larger, slower prop to match, and better seals.

Trolling motor seals are a concern because most of them are designed to handle only 1 atm/33'. Some will handle 60-90' for a while, and others will go much deeper, but you can't count on it. Some of the guys using these motors on homebuilt subs actually fit each motor with a scuba reg and pony bottle for active pressure compensation to try to keep them try. Others fill them with ATM fluid.

This isn't to say one shouldn't try to use a trolling motor. The seals can usually be upgraded And the inherent inefficiencies of the high speed motor and prop can be just lived with. However anyone who thinks they are going to build something equivilent to a Gavin using a trolling motor will be, odds are, disappointed.

[Windwalker]

The Motors I have been looking at are 1500RPM. Using a Modified "Ninja" prop (slow turning prop) in a Kort nozzle. I am not looking for something as buff as a Gavin. I don't need it. But I like building stuff, for the sake of building stuff. Then trying to improve it. The fun is in the Chase.

[oxyhacker]

Amen - I'd be one of the last people in the world to disagree with that!

Gavins are nice, but most of us don't need one. However, the basic Gavin design concept is hard to beat, and think there's a lot of possibilities for a low cost "fun" DPV made by combining cheaper drive with a Gavin-style housing.

For the homebuilder the nice thing about Gavin-style construction (besides that fact that it works!) is that its very much modular - since it's essentially an oversized divelight battery canister with both ends latched on, you can fit different power units just by changing or modifying the back plate, and different capacity batteries by changing the tubes. This makes it infinately upgradeable, all the way up to "real" Gavin specs should a Mako drivetrain turn up.


Windwalker once bubbled...

I am not looking for something as buff as a Gavin. I don't need it. But I like building stuff, for the sake of building stuff. Then trying to improve it. The fun is in the Chase.

[Windwalker]

Perhaps I should. Sounds like the modular way would keep me from having to rebuild chassis. Good Idea.

[ShoalDiverSA]

Aquamaniac once bubbled...


The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts

Dave

Dave,

Been diving :thumb: , so I haven't had a chance yet to say thanks.

Thanks! :D At least now I have something to aim for with my search.

Cheers,

Andrew

[ShoalDiverSA]

oxyhacker once bubbled...

Trolling motor seals are a concern because most of them are designed to handle only 1 atm/33'. Some will handle 60-90' for a while, and others will go much deeper, but you can't count on it...

...This isn't to say one shouldn't try to use a trolling motor. The seals can usually be upgraded...


I was thinking of using the trolling motor as a "rough and ready" DC motor. I would like to use a different seal though, as I have heard that some of the trolling motors even use grease as a seal!

Thinking along the lines of pool/spa motor seals (John Crane/Burgmann). These are good for about 20ATM at 1000rpm. They really have good pressure ratings at the relatively low speed of DPV motors.

Now to find that motor...

Enjoying the thread, by the way - keep it coming!

Cheers,

Andrew

[Aquamaniac]

Pump motor seals are perfect.
Here is what a Gavin Has.

[Straggler Dave]

...Any plans for a book on building scooters? :)

[oxyhacker]

We have one in the works, but it won't be for a while. It's a big subject, and a lot to build and test first.



Straggler Dave once bubbled...
...Any plans for a book on building scooters? :)

[DennisS]

oxyhacker once bubbled...
We have one in the works, but it won't be for a while. It's a big subject, and a lot to build and test first.




Sounds great, if it's as good as the reg repair book, I'll be buying a copy the first day its out

[michael-fisch]

[QUOTE]Aquamaniac once bubbled... [B...

quote: Aquamaniac once bubbled...


The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts

Dave


Dear Dave,

The Mako motor does 800RPM,
at 24VDC using an average of 10A.
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust. The propblades have to be pinned for the higher thrust otherwise they will bend/warp.

[Jaap]

Is the Gavin really using that much less power than the Mako?

-------------------------------------------------------------
quote: Aquamaniac once bubbled...
The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts

quote: michael-fisch once bubbled...
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust
---------------------------------------------------------------

If the numbers above are correct that should imply that the Gavin only uses about half the power (17Ax24V=408W) compared to the Mako?

But the Gavin is faster, can it really be that much more efficient? Sounds like something is wrong here?

[Aquamaniac]

Jaap once bubbled...
Is the Gavin really using that much less power than the Mako?

-------------------------------------------------------------
quote: Aquamaniac once bubbled...
The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts

quote: michael-fisch once bubbled...
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust
---------------------------------------------------------------

If the numbers above are correct that should imply that the Gavin only uses about half the power (17Ax24V=408W) compared to the Mako?

But the Gavin is faster, can it really be that much more efficient? Sounds like something is wrong here?

Im just quoting from the Oceanic data they sent me.

[pipedope]

is confusing peak power and average power.

[Aquamaniac]

All motors are rated at FLA (full load amps)
What they actually draw when towing a diver, or sitting on the bench is irrelevant

[pipedope]

The power and current draw during use is FAR more important than the "ratings".

Electric motors use power depending on the load (and their design).
I can use a motor rated at 100 HP to drive a load that is only 5 HP. Probably not very efficient.

I can also show you places where you can use a motor rated for 20 HP to actually make 100+ HP.

Useage is more important than rating.
The ratings are mostly useful when shopping for motors as it gives you something to tell the sales rep so that you get into the right series of motors. You still have to match the motor to the *actual* loads and speeds it will see in use.

[Aquamaniac]

Respectfully, I disagree (to a point).

You need to know the FLA, so you can calculate what cable to run to the motor, what protection it requires, how much power you need to run it etc etc.

You need to know the HP rating, so you can ensure the load is matched to the motor.

The Power rating of the motor is a product of the Supply voltage, multiplied by the FLA and divided by the efficiency rating.

Amps times volts does not mean anything unless you have an accurate efficiency rating.

Im curious as to how you can get 100HP out of a 20HP motor?
(remembering that nameplate ratings at rated at shaft HP)

Dave

[Aquamaniac]

Aquamaniac once bubbled...
All motors are rated at FLA (full load amps)
What they actually draw when towing a diver, or sitting on the bench is irrelevant

My point here was, if someone tells me its a 20 amp motor, that SHOULD mean that it draws 20 amps at FULL LOAD, not 20 amps when its towing a diver, or sitting on the bench.
The nameplate ALWAYS lists FLA.

[pipedope]

First, take an ADC 9" DC series motor, run it on 144VDC (12x12v batteries or 24x6v batteries). The normal battery load in a car will limit the run time and keep from burning up the motor. Also driving style makes a difference.
DC motors are usually current limited. You can run then on a higher voltage and make lots more HP (because the RPM is higher) without exceeding the curent limit. Lots of electric cars have 36VDC motors in them and are using 96 or even 120V battery packs.

Same thing in a DPV, we can run far beyond the designed rating because we both limit the run time and have the ability to keep the motor cooler than most applications.

I prefer to wire for more than rated current or actual current wichever is higher.
Fuses, if used are there to keep the wiring from burning up.

The nameplate is a snapshot of one point on a set of operating curves and especially for DC motors is often not even close to where you actually operate them.

Often the quoted rating is the 'continuous' rating. For shorter run times you can often make a LOT more power.

[Aquamaniac]

OK, I see what your getting at, and yes I agree.
I was commenting only on nameplate data, and not considering duty cycles, over rating etc...

Fuses protect the wiring, Yes I agree there as well.
Motor protection devices protect the motor.

We are going in circles here, and it has nothing to do with the original point.

My issue was:

The Mako motor does 800RPM,
at 24VDC using an average of 10A.
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust.


Volts and Amps alone do not determine how "fast" or efficient a motor is.

[pipedope]

Here is what I was looking at;

quote: Aquamaniac once bubbled...


The Mako motor specs are
Speed:2.7 Mph
Thrust: 50lbs
Voltage: 24 VDC
Current: 34 Amps
Power: ~800 watts

Dave


Dear Dave,

The Mako motor does 800RPM,
at 24VDC using an average of 10A.
The tuned motors George is now using turn at up to 1200RPM, burn @ 17A at 24V and produce 55LBS of thrust. The propblades have to be pinned for the higher thrust otherwise they will bend/warp.


There are the nameplate specs for the Mako and then a jump to average numbers without detail of the conditions of the tests.

The wind of the motor will determine where the 'sweet spot' is.
Will the motor want to turn fast with low torque or slow with high torque. Picking the right frame and wind is important as they need to match the load of the prop. The prop needs to match to thrust needed to pull the load.
The idea combination will be different for a rec diver with a single tank and a deep tech diver with twins and stages.

It is helpfull to look at the entire system including the diver and gear. Much like setting up a power boat. A light speed boat will use a small prop turning at high speed. A tug will have a very large, slow turning screw. Most boats are somewhere in between.

Getting something to work is pretty easy. Getting both performance and efficiency is not so easy.

[Scuba_Vixen]

from known values, you can fill in the unknowns.

Typical batteries for the tekna/mako are 18 to 20ah (20 hr rate) and only 10 to 12 ah (when looking at their 1hr rate.... (the realistic one for this application)

Most rec divers get close to an hour (give or take, depending on conditions) of run time, before the battery seems tired.

That tells us that the motor draws about 10 to 12 amps on average.

If you get less than an hour, you can look at the battery spec sheets and get a close approximation of draw for the conditions that gave less burn time.

I'm thinking that maybe the 34 amp figure was for locked rotor amps .... fair sized 12v trolling motors are less than 35 amps.

Just can't resist a scooter thread,

Darlene

[pipedope]

May I move in with you and build scooters?
:D