Bob
found your motor 11hp, 2300 rpm on 48v or 8 hp, 1600rpm at 36v
what prop do you have?
The 36v setup is simpler. Similar torque in direct drive as the 48v system but less horsepower
The 8 hp comes at 165 amps - that's a lot unless you have huge capacity packs
No problem is short duty cycle or run time apps like a cart - 1 or two minutes from hole to hole , or or two starting spikes, very low current once the car is rolling
In a boat that wont work. A boat needs consistent torque (ie amps= torque & also heat). My guess is the motor should be rated more like 4hp on 36v 6hp on 48v for continuous loads such as marine use.
If you go to 48v the 11hp rating is 170 amps even more - I cant see you pulling those amps continuously for a long time. Thats more than the world record electric boat pulls and it is getting hard on its brushes at those amps and it has 4 sets well ventilated brushes.
Brushed motors are more difficult to cool than brushless - The coils heat and cant be directly cooled. The comm/brush interface is a very hot place! Position the motor so you can see the comm and brushes; at night turn the lights off and allow it to free run on 36 or 48v - you will see what I mean. A strong fan pushing air over the brushes into the motor and exhausting out the bearing plate end will help. Because its harder to get the heat out of a brushed motor it is important to avoid overload and the death of the commutator.
It is a great idea too if you can cool the brush hoods with water. Also you may find some of the metal around the brush end of the motor can be cut away to enable better air cooling of comm and brushes.
BTW is the motor new, reconditioned, or used? Are the brushes and their springs new? Has the commutator been trued? If the comm look blackened or like it has been sanded with an 80-120 grit paper or a file it should be trued (machined smooth) and brushes and springs replaced. If you cut the comm a nice gentle run in of the brushes/comm also helps as much as running a gasoline motor in. This improves the motors performance significantly and enablew it to run much more efficiently and last much longer. Pushin a worn comm, damged brushes or floppy springs can destroy it. Finally you may find some of the metal around the brush end of the motor can be cut away to enable better air cooling of comm and brushes. Same at the bearing plate end.
Depending on your prop and the number of blades I would be planning a reduction of at least 1:2 or more so the prop is spinning at about 1150rpm; that will double the motor torque output by the time it reaches the prop. The high torque name seems to be because the motor has a lower Kv that the high speed version of the same motor. That gives it more torque poer amp but it doesnt mean the motor is built to take more amps.
A 1:2 reduction ratio will double the torque level at the prop. If the prop is a little smaller the amp draw will be lower. You win both ways
Is your current controller electronic or electro mechanical? I note that for the 36v model they recommend a 400 amp controller
Apart from anything I have suggested get down to alocal hobby store and ask for a infr-red contact free thermometer. You can get real temps of different parts of the motor quickly and see immediately how it is affected by the setup. Brushed motors are great - but it is more important to set them up so they have plenty of headroom and then the brushes and comm will last well.
regards Andrew
On 2/28/2012 3:55 PM, Robert Jorgenson wrote:
been sailing professionaly for over 20average motor run time for 6 day San diego harbor to oceanside to Catalina to San diego is about 30 minuets total on charter.10 min recreationally for 6 days.Talked to my friend this afternoonwill try 24 v system thur controllerwith a direct hot wire 48 volt without controller insystem in case i want to motor at night solo if i ever have guests with a schedule.Also have a 15 hp gamefisher long shaft mounted on the transom for Canal transite with 24 gallons of fuel for boat delivery.
24 v 70 lbs trurst mini cota outbard = anyone found a good power prop for this motor = goes great on my 17 ft flat bottom 33 in beam with cargo of of 600 to7oo lbs inclding batteries , wife and dog. Almost ready to give up 30 ft sailboat and use a tent and a visa card for a motel.Rented a 25 ft Cayuca and visited with the Cuna Indians for a week in Panama.Met by 6 strong indians one night who picked up my boat and all possesion and put them in the local school house.WHAT HOPITALITY!!!!
Capt bobShockwaveCornado 30
From: Andrew Gilchrist <andrew@fastelectrics.com>
To: electricboats@yahoogroups.com
Sent: Monday, February 27, 2012 6:22 PM
Subject: Re: [Electric Boats] Prop size for 10500lbs 30 ft. coronado sailboat
Ken
nothing against run what ya brung -
but particularly because it is whats availble rather than a planned optimum a little data and some tweeking can result in big improvements in efficiency & performance and give a lot of insight into why or where problems might be experienced.
Best of all it means even systems can change from ones which are unknown outside a part throttle settings to ones which run cooler, longer with better performance and can be used hard without fear of 'undersirable problems'
On 2/28/2012 3:21 AM, KEN wrote:
(its all theoreticals to me, I sure wont deny it.)not doubtin your opinion at all Andrew, I'm a deffo rookie to this stuff..and some of us rookies are on the "run what ya brung" kind of budgets.we also like to tinker, which also has to be within a realm of realistic (somehow!).I do think if Bob gets some calculations together, it could work out fairly decent.gear ratio, prop pitch, motor rpm etc. water being definite constantly variable load,currents, windage, its all gonna mess with stuff, calculations too.a golf cart might run 5-10 minute bursts, 12-15mph, is definitely a different kind of duty.wouldnt think it impossible to safely adapt with some decent efficiency from it tho.I'm open and curious about opinions and criticisms, only helps me learn more-better!I'd also think a handheld tach would be more than just handy to see the motor's free spinning rpm's at 24v, and whether it can reach 80-85% of that under full load, as an indicator of a prop pitch being too much a load, they arent real spendy. its likely more important than what kind of hp the motor can actually put out, reliability-wise. same for keeping good track of the motors temp until its behavior well known stable.
From: Andrew Gilchrist <andrew@fastelectrics.com>
Subject: Re: [Electric Boats] Prop size for 10500lbs 30 ft. coronado sailboat
To: electricboats@yahoogroups.com
Date: Monday, February 27, 2012, 10:00 AM
I'll be matter of fact here - it sound dangerous to me
the proposition your float is essentially a motor used to push 1500 lbs with short term usage, spikes dropping down rapidly to a very low average amperage and lots of cooling time, will now propel 7 times the mass at 50% more voltage than previously, through a underrated old tech speed control, through liquid.
the load could be 10.5 times that of the buggy; and its long term 100% duty cycle instead of the short time light load of the buggy
Establish the amp draw of the controller - but things don't look great a 36v controller being run at 48v and probably a much higher load than the cart could create if it is a resistive coil set up ditch it its dangerous and wasteful
and a 10hp motor - is that max power or continuous power
whats the kv - the the torque per amp and the efficiency levels
* first make sure your charger is correct type for that battery type and you have a battery management system on it.
* Make sure everything is well insulated
* establish the motor kv, peak rpm, 92% of peak rpm and amp draw at max efficiency
* get your prop pitch and use it to establish how fast the prop will try to push the boat at 92% of peak rpm; if its 20 knots you are barking up the wrong tree all round - if its 2-3 knots that may be survivable
* ditch the electro mechanical controller and well overrated PWM type
if you persist with the current setup try running it at the dock and so you can observe the controller directly - if it is electromechanical it will probably glow red hot - unworkable - have fire suppression ready
At the very least you need an overrated PWM controller
Andrew
On 2/27/2012 11:21 PM, Robert Jorgenson wrote:48v battery supply
36 v controller
10 hp General electric DC motor
can the golf cart controller handle the load?
what size Prop will be most efficient????????
fire hazzard lithion ion batteries =factory sealed 24 v battery packs in heavy alluminun box.
what size prop should work well??
I realize I will have to experiment but i need a starting place.
was not getting consistent voltage even though the battery cells read fully charged.
battery terminals factory sealed with foam.
removed foam from top of connectors
two of the nuts on top of batteries required a 360 degree turn to bring them to he same torque as the other 14 9/16 nuts.
this is why I have had an electrician guide me thur such a simple p
ocess as battery instalation.
Capt. Bob 435 678 3436
Shockwave
Golf of Mexico
Equal opportunity Crew openings with Drivers licens Mpving 30 ft Coronado from blanding, Utah 84511
to Houston Texas, one ton Chevy stick shift
Individuals will be incouraged to cruise for a couple of weeks in golf of Mexico
What tourque should the 9/16 nuts on the battery terminals be set at????????
-- AJ Gilchrist Fastelectrics 0419 429 201
-- AJ Gilchrist Fastelectrics 0419 429 201
-- AJ Gilchrist Fastelectrics 0419 429 201
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