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[RRS01]

How effective would it be to convert an automobile starter motor to power a boat?  I need a motor with a half inch shaft, to mate up to the drive shaft and prop I have already.

 I've heard that it was fairly common to use them in RC "battle robots" when they used to "fight" them a few years ago ... but is there a limit to the length of time they can constantly run before they burn up / melt down?

 AND, if they are effective, does anyone have a link detailing how to modify them??

Thanks in advance! 

[Roadrunner]

An area i know some about for a change...

Car starter motors are used quite frequently in large boats as well as the battle bots.

The majority of car starter motors are 12v in the cases of battle bots they run them at 24V in maximise rpm output and torque.

There life span is the same as any other motor if not over powered so if its a 12v then running on 12v it will last several years before a replacement is needed.

The down side though... esc's you need to locate an esc thats big enough to cope with this type of motor. I can't offer any advice on the esc size as i have never used motors of this scale.
but i would assume it needs to be in the region of 100A +.

Have a look here http://www.teamtornado.co.uk/

This is one of the most popular battle bots, that used twin car starter motors at 24v in there beast. Im sure having a flick through the site will provide more information then any of us can tell you.
The site has a build diary which is more relevant to your interest.

hope it helps 

[Roadrunner]

just a quote taken from the site on the speed controller

'' The speed controller was a custom design, using five 60 amp FETs on each leg of a pair of H-bridges, giving us 300 amps capability. Building almost all of the electronic parts ''

 ''Fork lift truck fuses (200A) were used to prevent fire in the event of a short circuit, and the removable link was made up from a pair of AMP automotive connectors, rated at 75amps each, giving us 100A continuous current capability (including the derating for putting them in a block).''

[Arrow5]

RRSO1, you didnt mention what your model was. Is it a manned model, a half inch shaft means a BIG boat.

[andrewh]

Gents

There are some details needed here. 
AFAIK all car starter motors are shunt wound meaning that the initial start currents are very high and the brief powers available are huge
an unmodfied starter would not last more than a minute or so at full power unless the current was heavily limited

For use as a propulsion motor they are normally converted to series wind  - like a Taycol -  and in this form they will be a well-built heavy duty motor and are much used for gocarts and repowering lawn-mowers.
I have seen recently a how-to on the conversion - Google "converting starter"

also don't forget that motorcycles have dinky little starters, and many asian cars use geared starters (geared about 1.5 to 1) and both of these might be useful to us boaters
andrew

[andrewh]

Found this which illustrates what I was trying to say

http://homepages.which.net/~paul.hills/Motors/Starters/StartersBody.html

the windings really are 3 turns of fencewire

andrew

[Circlip]

Ever heard of "Torque reaction" RRSO1???

  Regards  Ian.

[sweeper]

Some electrical info for those considering using such a motor.

Starter motors are SERIES wound, this gives them their unique characteristics of high torque at low speed and low torque at high speed.
To prove this idea, think of the job they have to do - starting a car engine against compression. It takes a lot of grunt (torque) to achieve this.
The old type (interia starter using a Bendix gear to engage the flywheel) misapplied electrical theory for many years as the motor spun up to high speed before the gear was thrown into mesh. The modern type (with a solenoid mounted on the motor) engages the gear before the motor is energised.
To employ such a motor in a boat could be interesting as a number of factors will come into play - mainly the prop size and pitch and the rating of the speed controller. I've never tried using an electronic unit for these motors, in my time tapped field windings were the only method that we could use.
I would certainly be very wary of using a 12V unit on a 24V supply, a short life but a merry one?
Hope this helps someone

[andrewh]

Sweeper,  how right you are - indeed they are SERIES connected

senility and brian-fade is my excuse
andrew

[john s 2]

Modern Motorcycles can be a source of smaller starter motors. John.

[RRS01]

Thank You all for the information!! 

RRSO1, you didn't mention what your model was. Is it a manned model, a half inch shaft means a BIG boat.

I'm trying to build a Galleon ... from stem to stern it's 110" and the beam is 34"  ... My thinking is, in case the wind dies down, I want something to power it back to shore.

Ever heard of "Torque reaction" RRSO1???

Sorry, I haven't ... BUT, if I had to guess, it would be where the prop doesn't move, but where the thing attached to the motor does ... (Visions of "Wile E. Coyote, Genius" come to mind)     

  I would certainly be very wary of using a 12V unit on a 24V supply, a short life but a merry one?

 
I was thinking of only going 12v  Like you say, 24v would be a SMOKIN' good time!     

[Circlip]

 

[triumphjon]

im sure there must be far better motors than an old automobile starter motor ? after all not only do you need to cut off a large chunk from the front casing , and remove the solinoid , they are heavy ! as for some of the modern geared starter motors have you seen the prices of them ? one for my car would cost me the best part of £300 !

[nick_75au]

I don't know what sized prop you intend to use I would recommend a discarded drill motor with gearbox attached, that will have enough torque to spin a 5-6inch prop on their high speed setting 1200 RPM or so

[tigertiger]

A geared arrangement makes sense. On a galleon, the prop would only need to turn slowly if it is a big prop. Or a small prop and a higher speed smaller motor.

All you need to do is limp homel

Because you are specifying a 1/2" shaft I assume you already have some sort of full size boat prop in mind.

One idea I had for very big models is to modify an electric trolling motor. I think the small ones with under 20lbs of thrust can be got for about 100 quid.

[Yarpie]

Why not consider a 12V DC automobile blower motor?

These have plenty grunt and I use two to propel my 3 metre model of HMS RODNEY. Furthermore, they are controlled by just one 35 amp ESC.

They don't however have a half inch shaft, but this can be stepped up/down via couplings.

Why not search around your local car scrap merchant? (Provided you don't live too near me as I am about to search for a spare matched pair!).

And, by the way, the square-rigger guys in my display team use the same type of propulsion.

[Big Ada]

Why not ask Rathikrishner ?    

[unbuiltnautilus]

One idea I had for very big models is to modify an electric trolling motor. I think the small ones with under 20lbs of thrust can be got for about 100 quid.

Our Manned Battleships use Minkota electric outboard (trolling) motors. These cost us about £130 about five years ago. They turn a prop about 10" in diameter and are designed for constant running, not momentary, as with starter motors. Current drain is about 20 amps at top speed but at lower speeds they start at about 10 amps. The speed control is built into the handle, this we rebuilt as an onboard throttle unit. They give 5 speeds forward and 3 speeds in reverse. Obviously the unit would have to be disassembled for use in a model. Thinking about it, you could sling the motor pod out the bottom of the model, would make a good keel weight but would add greatly to your draught.

[RRS01]

THANK YOU ALL!!!

im sure there must be far better motors than an old automobile starter motor ? after all not only do you need to cut off a large chunk from the front casing , and remove the solinoid , they are heavy ! as for some of the modern geared starter motors have you seen the prices of them ? one for my car would cost me the best part of £300 !

Well, here's the deal, I acquired the half inch shaft and propeller a few years ago, and thought that they would work nicely in this drama I call "my Galleon" sooo, I continued to attacked it from the angle of finding something to drive it ... BUT dammit all,   

YOU ALL are opening my eyes to a plethora of possible alternatives!       

I don't know what sized prop you intend to use I would recommend a discarded drill motor with gearbox attached, that will have enough torque to spin a 5-6inch prop on their high speed setting 1200 RPM or so

 
the props I have, (on the half inch shafts) are 4 inches with 3 blades ... (I just wanted something that had a very low possibility of kinking)
I was definitely thinking of using a drill motor to control the sails, but I'm a bit fuzzy on how to link it up to a servo ...

One idea I had for very big models is to modify an electric trolling motor. I think the small ones with under 20lbs of thrust can be got for about 100 quid.

don't trolling motors need to be in the water to keep them from overheating? I'm hoping that I can make everything pretty much self contained and won't need to put a keel extension on my boat ... plus, a keel extention would scrap my plans to use

[RRS01]

Why not consider a 12V DC automobile blower motor?

These have plenty grunt and I use two to propel my 3 metre model of HMS RODNEY. Furthermore, they are controlled by just one 35 amp ESC.

They don't however have a half inch shaft, but this can be stepped up/down via couplings.

Why not search around your local car scrap merchant? (Provided you don't live too near me as I am about to search for a spare matched pair!).

And, by the way, the square-rigger guys in my display team use the same type of propulsion.

AWESOME ship you have there!!

 I wanna talk with YOU!    what is the shaft size on blower motors? is there any problem with them getting bent? what do you use as a stuffing box?  How do you control the sails?  Can you raise and lower them?  what type transmitter do you use for your square rigger? (are you familiar with Jean-Claude Cornaz and his Cutty Sark? how about the transmitter he made (I guess he made it)


or is his design just overkill? (from my understanding it's a combination of two transmitters)  I must admit, I do like it (I don't really understand it,    but I like it ),  but then, I know nothing about sailing, let alone sailing a square rigger! 

Why not ask Rathikrishner ?    

O Kay, I'll bite, Who is Rathikrishner ?? 

[RRS01]

SORRY, I got cut of in mid thought 

here it is again

One idea I had for very big models is to modify an electric trolling motor. I think the small ones with under 20lbs of thrust can be got for about 100 quid.

don't trolling motors need to be in the water to keep them from overheating? I'm hoping that I can make everything pretty much self contained and won't need to put a keel extension on my boat ... plus, a keel extension would scrap my plans to use a jet ski trailer to haul it with 

(on a side note, just what is a 'quid'?  I know, I know, it's money, but what is it's value ranking in relation to 'pound' (sterling?)  Please forgive my ignorance, but, hey, I'm from the States)

[malcolmfrary]

Rathikrishner = a miss-spelling of  "rathikrishna", a young lady from India who has a reputation for producing excellent models and controllers from pretty much zero resources, apart from talent, imagination and enthusiasm.
quid = slang for "pound".

Having a prop shaft of 1/2" does not demand a 1/2" motor shaft.  A multi-part coupler can have different sized ends, as can a one-piece coupler.  If pulleys are used, the main requirement is that both use the same size/type belt.
Since a square rigger does not need to go like a racing cat, a quite modest motor, geared down to match the prop, will do the job.  If looking at auto scrap yards as a source, motors from radiator fans and heater fans and window winder motors geared down are good candidates, as are the battery tools mentioned.

[triumphjon]

the galleons that yarpie has posted use a bolt on keel , added to the model when they set up to launch , most are using standard 40 mhz  radios the only modification being for the gun armament !  web address for the club involved is , http//. www.pmbdt.co.uk 

[Shipmate60]

Have you considered a Wiper Motor.
These can be large, fairly slow running and continuously rated.

Bob

[Marks Model Bits]

As an ex car mechanic I cannot understand why you would want to fit a motor in your boat that could possibly draw in excess of 150 amps under light load and up to 400amps + if the prop gets fouled!!!!!!!!!! (just look at the cross section of wire going to the starter motor) Also a starter motor is only designed for momentary operation and continuous use even for a few minutes under light load will overheat the motor and flatten the battery in very quick time.

I would follow the advice above, blower motors, electric window or seat motors, or wiper motors are a much better option.....


Mark.