Are DPV noisy ?

[lucca brassi]

I like to ask community in DPV which run different types of scooters : Do you feel that are DPV noisy ?

I'm asking that because of choice between :

- planet geared propeller with brushless motor ...and choice ...

- of belt driven propeller with brushless motor

 

[tbone1004]

i think anyone who says no either hasn't been on a DPV, is deaf, or is lying. Certain scooters make more unique noises than others. My UV-26 makes a very different noise than my buddies Magnus *which I find VERY annoying*, and that is different than the original minnus *more annoying*, and the current minnus *less annoying due to helical cut gears*.

I guess my question is why do you need to gear it? Cost savings from a higher RPM motor? 1200rpm is a good sweet spot for max RPM from what I understand, and I know that the sound and overall feel of my direct drive UV26, granted it is brushed, is very different than some of the geared dpv's like the Minnus.

you can hear the lower pitched whine of the magnus throughout the video and the higher pitched whine of the minnus with the gear reduction. Both are annoying to me.

vs. a very different, and in my opinion less obnoxious noise of a Suex XK1

 

[KeithG]

yes they are noisy. i have only seen them twice in the water in bonaire. both time they were cruising the reff about 20 feet above me. i had my head stuck in the coral looking for small things.

the only reason i saw them was that i heard them.

 

[Jack Hammer]

Yes, scooters are noisy but not deafening. I've used quite a few different scooters and they all make that droney pulsing noise, just the pitch and relative volume differ. Scooters are a tool and the trade off for using them is you have to listen to the sound. You get used to it.

 

[cool_hardware52]

Not all scooters are equally noisy, although all make some noise. Electric motors make a *lot* more power per pound of motor as the rpm goes up, and the mass of the motor plays a significant part in scooter design. In addition nearly all "off the shelf" motors are designed to run at fairly high rpm. Propellers OTOH are most efficient at RPMs much lower than the typical motor.


DPV's that predate the Tekna (which later became the Mako under Oceanic) typically used high speed "off the shelf" motors and some form of Gear Reduction. The gear reduction can be a significant source of noise.

Tekna was unique in that the designers commissioned a custom motor from the previous owner of Astroflight in Santa Monica. This motor was designed from the beginning to be hi torque, low rpm, as opposed to the low torque, high rpm motors use previously. The low speed, hi torque allow it to drive a prop directly without any gear box.

Tekna suffered some scooter explosions due to hydrogen gas generation from charging the lead acid batteries and Oceanic ended up buying what was left of the company and the Tekna became the Mako.

Recent focus on smaller, light weight hi performance DPV's has lead some designers to revisit the light, small, hi output, high rpm motor and gear reduction approach to reduce the mass of the "drive train" These scooters do generate more noise than the direct drive designs.

Scooter noise can be a plus for team diving, as it provides a means for separated team members to locate each other. In low viz with fast scooters in open water separation requires only a moment off the trigger. Listening for the hum and the looking for the dull green glow becomes a practiced skill.

Tobin

 

[Jon Nellis]

For noise reduction, any speed reducer will make additional noise on top of the motor noise. How much noise, depends on the design of the speed reducer, but belts typically make less noise than gears. Noise from motors, results from a few different variables, like switching frequency, wave form and winding design. There are a few tricks we use to reduce noise from these and at lower speeds the Genesis is nearly silent, but implementing noise reduction features also increases cost, and most manufacturers are more concerned with their bottom line than noise.

The reason high RPM motors are used with a speed reducer is that most off-the-shelf motor configurations are designed to spin at a higher RPM (3000-4000) than what is optimal for marine propellers (500-1500RPM). It's related to the design and manufacturing process of the motor, which makes it cheaper and easier to achieve higher efficiency with a higher RPM motor. A high RPM motor can be wound to spin at a lower RPM, but the power conversion efficiency will be lower. Unfortunately, using a higher efficiency, high RPM motor with a speed reducer does not provide much if any efficiency increase, due to the mechanical power losses from the speed reducer.

Increasing the efficiency of low RPM motors is more difficult and expensive, but this is what we do on the Genesis and why we have the best power efficiency. Unfortunately, the OP will have a tough time getting one of our DPVs in Slovenia.

As for noise comparison, do not rely on video clips. The microphone pickup is never the same, since most cameras try to automatically adjust the mic gain to produce sound at the appropriate level. You really need to dive them to tell the true difference, ... but in any case, they all beat kicking.

Edit: Apparently I was typing at the same time as Tobin and the answers are pretty much the same

 

[tbone1004]

the video wasn't for volume, more for the way the sound. Volume wise none of them are that bad, it's the way they sound that are annoying to me.

 

[3D diver]

Yes. My buddy used to use one & I created an MP3 of "underwater noise" to use in my videos when his scooter was running.

 

[lucca brassi]

Thanks's guys for that info . I'm looking for some challenge in winter months so I thought can I made it? I have DIY several lights and they work without any flooding so no need to build them more ;-) ...then......I looked that Bonex system ( and several others -and that build looks easy but it is heavy !)

Bonex system

and I was thought in similar system. I have found nice motor with 1300W and 48V and cca 3000 rpm , to get better torque I thought to reduce rpm with '' standard'' gear ratio 3:1 to get 1000 rpm (not optional but cost effective) ; also that system have 7,6 kg on motor +cca 2 kg on reductor and controller ..... for instance shaft have 22 mm in diameter
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Then in our local forum ''electronics forum'' someone show me belt reductor

O.S. OMA 4043 f3a brushless inrunner motor (ore detailed pics)
OS MOTOR OMR-4043-172 whole system have 0,625 kg ( shop )

of course that is idea - how to do right - not buy for $$$ . But i think more and more that that is right way... even more it is cheap and effective and ''relative silent''
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also have looked myself some old DIY attempts like:

dykking.info (belt driven) ( PS : anyone know these propellers used in DIY ?? It looks complete different than all others (i think they are very effective (large surface - many blades) and used for really low rpm (cavitation at higher rpms))

http://subsurfacetech.synergize.co/ScooterLaunch.php?i=1

http://www.silent-submersion.com/Products/Magnus/Magnus Instruction.pdf

PS : I have read some comments on SB pages about buoyancy trim problems due heavy brushless motors

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@Jon Nellis , thank you very much for yours reasonable comments - like them very much

In Slovenia we have only 1 hour to get to Trieste to visit SUEX - Dive in the fast lane which are used also ander Halcyon brand name.

 

[rjack321]

PS : I have read some comments on SB pages about buoyancy trim problems due heavy brushless motors
.

Do not underestimate the need for your scooter to be 1) neutral and 2) float close to level - both ideally in freshwater. The usual issue is having inadequate air volume (buoyancy) towards the tail and a heavy motor in that same area so that it wants to point straight up. Most manufacturers compensate by lengthening the body so they can push the batteries forward and have a modest sized air buoyant space in the middle of the body with batteries on one end and the motor on the back. Good luck with your project.