Improving a trolling motor

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Vic130
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Improving a trolling motor

Post by Vic130 » Aug 23, 2017 8:00 am

Hi!

I'm new on this forum although I've been browsing the watercraft section for a while.


I am an avid fisherman and I usually use my trolling motor on a 4.4m deep V boat. It weights about 400kg.
The trolling motor is a 12VDC, 55lbs (245N) thrust installed at the bow. At 12.8V, the motors runs at 1540 RPM.

I want to optimize the design for efficiency at low speed (1m/s) and low noise.
Ideally I would like to keep the maximum shaft power under 600W.
I forgot to do readings over the last weekend, so I'll be doing them this Saturday.


Since I do not want to modify the internals of my trolling motor, I decided to add a Kort 19A nozzle and redesign my propeller.
My stock propeller does not have a spinner so that was one of my first additions. I also wanted to quickly replace blades so I created a modular hub. I can parametricly change the number of blades.

For the blade design, I started fiddling with JavaProp where I optimized off the available power, insuring that the prop would not go beyond 600W. I have access to a well calibrated 3D printer so I can print everything quite easily. Actually I already tested a propeller but it wasn't properly balanced.
I've red that Kaplan propellers would be adequate for my application (Ka-4-70?). Can anyone tell me where I can find the foils to use for the blade profile?

I've included figures of my current design.


Thanks for your help!
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parabellum
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Re: Improving a trolling motor

Post by parabellum » Aug 23, 2017 8:31 am

Vic130 wrote:The trolling motor is a 12VDC, 55lbs (245N) thrust installed at the bow. At 12.8V, the motors runs at 1540 RPM.

I want to optimize the design for efficiency at low speed (1m/s) and low noise.
Ideally I would like to keep the maximum shaft power under 600W.
I forgot to do readings over the last weekend, so I'll be doing them this Saturday.
I am also trying to improve a trolling motor, but the other way, mine is 24V 86lbs, I need more speed and more W IN. There is to little selection on props for trolling motors and mostly no specs on pitch, so I am ordering air props from Hobby King, with different pitches and diameters, to experiment. Then there is variable PWM controller to play with Voltage (for brushed). https://www.amazon.com/dp/B01MSLC1UI/_e ... T17VGJG5YO
Finer and slimmer blades are considered more efficient for your application but at expense of thrust, so you may find it interesting playing with air prop designs to.
Are not ducted fans less efficient?

Vic130
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Re: Improving a trolling motor

Post by Vic130 » Aug 23, 2017 9:18 am

parabellum wrote:
Vic130 wrote:The trolling motor is a 12VDC, 55lbs (245N) thrust installed at the bow. At 12.8V, the motors runs at 1540 RPM.

I want to optimize the design for efficiency at low speed (1m/s) and low noise.
Ideally I would like to keep the maximum shaft power under 600W.
I forgot to do readings over the last weekend, so I'll be doing them this Saturday.
I am also trying to improve a trolling motor, but the other way, mine is 24V 86lbs, I need more speed and more W IN. There is to little selection on props for trolling motors and mostly no specs on pitch, so I am ordering air props from Hobby King, with different pitches and diameters, to experiment. Then there is variable PWM controller to play with Voltage (for brushed). https://www.amazon.com/dp/B01MSLC1UI/_e ... T17VGJG5YO
Finer and slimmer blades are considered more efficient for your application but at expense of thrust, so you may find it interesting playing with air prop designs to.
Are not ducted fans less efficient?
I think ducted propeller are best in low speed, high thrust applications, like a tugboat.

I'm afraid that an RC aircraft prop used in water will not be appropriate. I've red that the efficiency will be the same provided the propeller operates at 1/15th of the RPM in water compared to air although blade loading in water will bemuch higher compared to RC aircraft applications.

Could blade loading deform the blades too much? Just like an aluminum propeller on an outboard versus a stainless steel propeller?

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parabellum
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Re: Improving a trolling motor

Post by parabellum » Aug 23, 2017 9:36 am

Vic130 wrote:although blade loading in water will bemuch higher compared to RC aircraft applications.

Could blade loading deform the blades too much? Just like an aluminum propeller on an outboard versus a stainless steel propeller?
That why I ordered 14-17" diameter props, to cut down to <10" diameter. They are bigger, fatter, stronger and I plan to start with 10" and reduce the diameter until I have the desired load on the motor. You have the advantage of 3D printer, so it is not one of your headaches. :)

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Monstarr
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Re: Improving a trolling motor

Post by Monstarr » Aug 25, 2017 3:00 am

I also have a motorguide 24 volt troller modded with Kelly KDS brushed controller.
Works like a charm and you can use a standard hall or potmeter throttle for power regulation.
Which can be thumb, twist, foot or whatever your application needs. Even RC powered if you'd wish that.
Still looking for a nice boat lever type throttle though. :roll:
Goldenmotor has a nice one, but expensive :?
https://www.goldenmotor.com/eBoat/frame-eboat.htm

I also shortened the shaft and put a m10 thread through the top part mounted with m10 ball joints for flexible steering control.
You can easily use standard boat steering assembly for actuation.
https://nl.aliexpress.com/item/Free-Shi ... 0.0.Kgzv75

Only thing, them 'cheap' PWM drives dont have a reverse.
A quality reverse contactor is expensive and also needs economizer circuit when you want efficiency.

What will be an evenly cheap option to address this issue?

jimbo_bubbles
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Re: Improving a trolling motor

Post by jimbo_bubbles » Sep 14, 2017 9:09 pm

Monstarr wrote:

Only thing, them 'cheap' PWM drives dont have a reverse.
A quality reverse contactor is expensive and also needs economizer circuit when you want efficiency.

What will be an evenly cheap option to address this issue?
This one does. I am currently using it on my canoe mounted trolling motor.

https://www.amazon.com/gp/product/B073S ... UTF8&psc=1

It really does put out 40A at 4S. I mounted a computer fan on it and haven't noticed it getting too hot. The LED is a % throttle indicator. 0-100.

My fish finder on the other hand only last like 2 min at 16.8V. Disappointing.

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Monstarr
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Re: Improving a trolling motor

Post by Monstarr » Oct 12, 2017 7:47 am

jimbo_bubbles wrote:
Monstarr wrote:

Only thing, them 'cheap' PWM drives dont have a reverse.
A quality reverse contactor is expensive and also needs economizer circuit when you want efficiency.

What will be an evenly cheap option to address this issue?
This one does. I am currently using it on my canoe mounted trolling motor.

https://www.amazon.com/gp/product/B073S ... UTF8&psc=1

It really does put out 40A at 4S. I mounted a computer fan on it and haven't noticed it getting too hot. The LED is a % throttle indicator. 0-100.

My fish finder on the other hand only last like 2 min at 16.8V. Disappointing.
Only, I would need 60 A @ 7s :) for the 24 volt motor.

Ah well, either way i just bought a 48 volt brushless trolling motor with 160 lbs (according to the sticker :))
Lets see next year how that goes.

Vic130
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Re: Improving a trolling motor

Post by Vic130 » Jan 11, 2018 2:44 pm

I've done some testing throughout the summer without the Kort Nozzle.

I did not get Amp readings though as the 3d printed propeller deflects too much when using ABS.
I'll have to try again next year using PLA.

Also getting the whole propeller balanced proves rather difficult.

blisspacket
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Re: Improving a trolling motor

Post by blisspacket » Jan 14, 2018 8:14 pm

Do trolling motors have ball bearing shafts? That's a basic question. I know the last trolling motor I took apart had only a single ball bearing on the front end. This absorbed the thrust, and it served as the bearing, sitting in a round recess of the commutator shaft. Pretty basic, cost-effective, but is this the way to use precious battery energy effectively?
There's high-tech, high-dollar energy invested in the Torqeedo motor. Those warrant consideration.

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