[PSUBS-MAILIST] Motor Suggestion?

Wed May 16 06:40:41 EDT 2018

James,
you could have a through hull propeller shaft with a small deisel engine
driving it by a pulley & belt & another belt drive for your electric motor. You
could then use your electric motor as a generator when surface running.
Would be a lot easier than making a thruster. Most modern motor controllers 
have regenerative breaking.
Alan

Sent from my iPad

> On 16/05/2018, at 9:42 PM, James Frankland via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 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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