[PSUBS-MAILIST] Motor Suggestion?

Wed May 16 05:42:47 EDT 2018

Hi All,

Thanks for all your input.  A lot for me to absorb there so I will
study it all.  Like the sound of the golf cart motors.

Emile, the idea is to put a generator inside the hull.  Motor in a can outside.

Regards
James

On 16 May 2018 at 04:08, Alan via Personal_Submersibles
<personal_submersibles at psubs.org> wrote:
> Steve,
> thanks for all the info.
> Great that you mastered the Vesc. I have someone trying to get
> the data off the Vesc for me. He failed using a raspberry pi but
> is having more success with an arduino. He intends to display
> it on a smart phone. Any chance he could email you if he gets stuck?
> My previous tests were with the Saite 6374 60kv.
> It wasn't an enclosed motor like the Maytech skateboard motor &
> I oil compensated the thruster to help with cooling.
> The Saite motor was working a bit like a vein pump & throwing the oil
> out of the housing & up the wiring tube. Nevertheless I got 30 hrs of
> continuous running out of it. I think I mentioned that I thought the oil
> I was using had dissolved the glue on the hall sensor board & put the
> timing out, also I hadn't press fitted the propeller shaft well & the motors
> rely on a good press fit as they don't have a can bearing to support
> the can.
> Were you oil compensating them or just running them as is inside a
> housing?
> I was thinking of drilling holes in the end of the Maytech housing to
> facilitate oil flow. I have read of brushless oil filled underwater linear
> actuators
> having their own little circulating propeller to cool the inside of the
> motor with
> oil, & they expound the benefits of being able to fit a smaller motor in the
> actuator because of this.
> As far as propellers & load goes, I initially went on a propeller calculator
> but
> have been buying props that are used on similar horsepower motors.
> I will test these props out & hopefully find something that works
> efficiently
> with the motors! Or at least see what direction I need to be moving with
> them.
> Also complicating things is that I need a prop that is made left & right
> handed.
> There is a bit of information out there on the 8085 motors in the electric
> surfboard
> builders forums. Will make quite a fast DPV!
> Cheers Alan
>
>
>
>
> Sent from my iPad
>
> On 16/05/2018, at 1:21 PM, Stephen Fordyce via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>
> Hi James & Alan,
> My trials with the Maytech 6374 brushless motor did not go well, although
> the VESC is amazing and I cannot recommend it highly enough.  Bit of a
> learning curve, but I can now change all the parameters and monitor
> everything (temperatures/voltage/current/RPM) via bluetooth and Android
> smartphone.
>
> Maytech recommended the 6374 motors based on the specs I gave them, and
> promised they would have certain resistance, etc.  Well, they arrived and
> didn't, so were only running at 50% efficiency with the propellor loads
> (roughly 27V, max 20A, ~500W, 800RPM) I put on them, and quickly triggered
> overheating protection as a result.  So if anyone wants a 6374 60Kv or 70Kv
> (I have one of each) let me know - I'm hoping to try the 8085 which is the
> next size up, but may have to go elsewhere if Maytech don't want to take the
> 6374s back or refund me on them.
>
> It's critically important to match (at least ballpark) the motor and prop -
> and both are highly variable (just think about the infinitely variable
> number of coils and prop pitch).  Otherwise a huge chunk of your electrical
> input power is turning to heat and you may not even realise (I suspect this
> may have been happening to Alan with some of his issues).  Just because a
> motor is rated to however many volts, amps or watts, doesn't mean it will
> perform well outside of the sweet spot.  Efficiency is difficult to
> determine because it's hard to measure power out - but a good approximation
> can be found from the motor curves.  I have a spreadsheet/calculator if
> anyone is interested - email me direct at
> stephen.fordyce at tfmengineering.com.au .
>
> The prop has a performance curve and so does the motor and matching them
> scientifically is a bit of an art form.  But apparently a good rule of thumb
> is to start with your prop RPM and torque under desired load.  To find
> nominal unloaded motor speed, multiply loaded RPM by 1.25.  Use this with
> your battery voltage to determine the Kv of the motor.  Then use the
> required prop torque to determine motor current and size.
>
> I'm finding that often the RC motors are not well designed for continuous
> operation and the associated cooling, so they need to be derated
> significantly, or better cooled.
>
> Cheers,
> Steve
>
>
>
> On Wed, May 16, 2018 at 9:01 AM, Brian Cox via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>>
>> Yes I am a proponent of golf cart motors as well.   If you can find a
>> place that repairs them you can find some good deals.  Best plan is to just
>> make multiple back up motors and switch them out if you have any problem.
>>
>> Brian
>>
>>
>>
>> --- personal_submersibles at psubs.org wrote:
>>
>> From: hank pronk via Personal_Submersibles
>> <personal_submersibles at psubs.org>
>> To: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
>> Subject: Re: [PSUBS-MAILIST] Motor Suggestion?
>> Date: Tue, 15 May 2018 22:15:05 +0000 (UTC)
>>
>> James, for an inboard motor, you can't go wrong with golf cart motors.
>> They are available in 48 volt and up to 8 hp I think.  These motors are
>> extremely durable and cost effective.  Gamma has a 2 hp traction motor from
>> a tenant sweeper, same as golf cart.  At full load it barely gets warm.
>> Hank
>>
>> On Tuesday, May 15, 2018, 3:28:36 PM MDT, Alan via Personal_Submersibles
>> <personal_submersibles at psubs.org> wrote:
>>
>>
>> Hi James,
>> just had a look at the motor & it's a bit of a beast.
>> Looks like an in-runner. It says elsewhere it is cooled with a fan but has
>> the option in the check box for air or water cooling.
>>    If you have a look at the Dragon submersible, they have gone with some
>> large diameter but short motors that resemble the high torque direct drive
>> bicycle hub motors that are popular. On the Dragon submersible it looks
>> like they have developed thier own propeller so that the thrust isn't
>> hitting
>> the body of the thruster.
>> The cooling system on your motor isn't going to work if you put it in a
>> water/
>> pressure proof enclosure. With the in-runner the coils are on the outside
>> & can dissipate their heat through the can, so there would be the option
>> of fitting the motor tightly in to a housing & letting the heat go through
>> the
>> housing into the water; but the fins on the motor won't let that happen in
>> this case. Maybe grind them off. It has a temperature sensor so there is
>> the
>> option of monitoring the temperature & running it at a suitable power.
>> Some
>> escs can drop the power automatically if the temperature gets too high.
>> The motor is very expensive. There is this Maytech motor designed for
>> electric
>> surfboards that is rated at 600W
>>
>> http://www.michobby.com/product/electric-surfboard-skateboard-e-bike-brushless-motor-8085-160kv-motor/
>> It is an 8085 160 kv out-runner & priced at $188- US. I am wanting to test
>> one of these but will test my smaller motors first to get a better idea of
>> what
>> kv winding I should have. Maytech will wind to your specifications; I
>> think you
>> have some knowledge of the RC world so you will understand this.
>> This motor being an out-runner has the coils on the inside & so I am
>> relying
>> on oil for cooling.
>> You will need to replace the propeller shaft with a longer stainless
>> shaft.
>> Your motor is designed to drive a pulley & you would have to check
>> what axial load the bearings take. In my thruster design I have my motors
>> suspended between two bearings in the thruster housing that take the
>> forward & reverse axial load.
>> Alien Power in England have some large brushless motors & motor
>> controllers.
>> I think he's a small operator & he will respond to questions. Got an idea
>> he's
>> in Birmingham.
>> I am focussed on my thruster testing at the moment, but could not put a
>> time on when I will test the 8085 motor. You can keep an eye on my
>> progress
>> if you want to hold off your thruster build.
>> There is an electric surfboard site that are using large DC motors, that
>> may be
>> of help, but these boards are doing 40kph, so are more like planning boats
>> rather than submarines that fall in to the work boat category.
>> Good luck.
>> Alan
>>
>>
>>
>>
>> Sent from my iPad
>>
>> On 16/05/2018, at 3:51 AM, James Frankland via Personal_Submersibles
>> <personal_submersibles at psubs.org> wrote:
>>
>> hi all
>>
>> I am thinking about what motor I should use for my main thruster on
>> Skadoc.  Its got to be big.
>>
>> All these ideas are just thoughts at the moment, as I am working on
>> battery pods now.
>>
>> Expecting delivery of pipe from UK today.
>>
>> So I have time to think how motor configuration is going to work.
>>
>> What do you guys think about this motor choice here?  As a possibility.
>>
>>
>> https://www.miromax.lt/en/m-6/c-39/c-45/product-500-bldc_motor_hpm-5000b_-_nominal_power_5-86kw
>>
>> I have room for 12 x12v batteries, so all voltages are a possibility.
>>
>> I am also thinking of running an inverter and working at 120v AC.
>> investigating this.
>>
>> Regards
>> James
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