Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: Brushless tyro wants one in an outboard  (Read 1406 times)

vintagent

  • Guest
Brushless tyro wants one in an outboard
« on: May 22, 2010, 10:17:54 AM »

Hi, I'm thinking of building model outboard motors as there doesn't seem to be any out there any more with any real power in a small size, so I was considering brushless. I looked on the Giant cod website and found some for very little money that would be ideal for use in a large scale outboard casing.

My question is which smallish sized (physically) motor would give me some power and be capable of running through gears suitable to power something like a 1/4 scale kneeler hydro.

I also don't understand all the battery pack numbers, etc. 
I would need an ESC, but not a reverse one and only a fast slow as it is, after all, a hydro.

Regards,
Vintagent
Logged

andrewh

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,064
  • Location: Melbourne, Australia
Re: Brushless tyro wants one in an outboard
« Reply #1 on: May 25, 2010, 12:43:48 PM »

hi, vintagent

er, simple question, less simple answer

First, a brushless will always give more power and speed than a brushed (cos it doesn't have brushes)
Do you know what power you are looking for to make your 1/4 scale kneeler hydro GO?   

Top of the head calculation - full size is about 8 feet long, so 1/4 model about 2 feet.  Round it up to 30 to 36 inches (for no reason)
If it were mine I would start with a buggy rat-motor (brushed) say 10 cells (12V and 30 Amps = 360 watts) for fairly vivid performance planing

Do you have an outboard body in mind, or are you going to make your own?  (You need only a pair of bevel or contrate gears of about 2:2 or 3: 1 ratio)

If you have an outboard in mind - say one of the Graupner ones, then the Brushless you choose will have to fit the motor mounting OR you will have to fabricate an adaptor plate

If you are making your own outboard (and some idiots enthusiastic people do

then you have the opportunity to create your own mounting

Suggest you use a dead cheap aero ESC (no reverse) as you are planning, but the choice will depend on the motor and battery pack you choose.  It needs to have plenty of spare amps so that it never gets distressed and the smoke remains inside
Please give us an idea of how you are planning to proceed, and we can try and guide you through the motor selection process
andrew
Logged

johno 52-11

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 297
  • Model lifeboats built to perform
  • Location: Dudley "The Blackcountry" West Midlands
    • lifeboat Models
Re: Brushless tyro wants one in an outboard
« Reply #2 on: May 25, 2010, 01:10:26 PM »

Hi Vintagent,

I have just finished rebuilding the outboards on my Atlantic 21 with brushless motors its on here at http://www.modelboatmayhem.co.uk/forum/index.php?topic=23520.0

any questions just ask.

If you are planning to make your own it will require some very fine engineering.

Regards

John
Logged

vintagent

  • Guest
Re: Brushless tyro wants one in an outboard
« Reply #3 on: May 25, 2010, 03:05:59 PM »

Gents, thanks for your kind help on this matter. 
Andrew, if a brushed motor will do the "business" then I'd happily use one of them as the ESC would be cheaper, especially if I don't need more than slow up to the dock and flat out, no reverse!

Is there a proprietary outboard which I can use that's still produced?
I could make, but that would stretch the facilities of my workshop a bit as I only have a small lathe and no mill.  And a fabricated brass one might be a bit heavy! <G>

Johno, nice footage of your o/bs on the Atlantic.  What basic o/b did you use?

I must thank you gents for your offers of help through the mire of electrics technology.
I'll almost certainly be back with questions!

Regards,
Vintagent.
Logged

johno 52-11

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 297
  • Model lifeboats built to perform
  • Location: Dudley "The Blackcountry" West Midlands
    • lifeboat Models
Re: Brushless tyro wants one in an outboard
« Reply #4 on: May 25, 2010, 04:34:43 PM »

Hi vintagent,

My outboards are scrach built mostly aluminium I should have posted a link to the full build history that is on my website http://www.lifeboatmodels.co.uk/atlantic.htm

I started quite a few years back basiclly because I was told you could not run an Atlantic with outboards.

So I set about building a pair. They where powered with speed 400's to start with until I went brushless this year. You only really need a lathe as most of the work is to do with drilling holes or making shafts. I am at the moment still using the plastic gears that I got from HPC gears. The bigest problem you will come across is that the gears wear out and a little bit of serviceing is required from time to time. I have also upgraded the props from 27mm two bladed props to 27mm three bladed ones and that as further improved the performance.

Hope this helps

John
Logged

andyn

  • Guest
Re: Brushless tyro wants one in an outboard
« Reply #5 on: May 25, 2010, 05:47:48 PM »

http://www.offshoreelectrics.com/proddetail.php?prod=grp-2380&cat=123

This propels a 30 odd inch tunnel hull to nigh on 35mph on our tiny lake.
Logged

vintagent

  • Guest
Re: Brushless tyro wants one in an outboard
« Reply #6 on: May 25, 2010, 08:09:16 PM »

Andy, I'm impressed by the flexible shaft idea, but it probably only works aesthetically on a big modern engine such as the Graupner unit represents, but thanks for the assurances about power. If I could get one second hand I'd definately grab it.  200 for my toys wouldn't go down well with my dear bride.  She hates shopping and I like to make stuff. We're the original Mr. and Mrs. Tightwad, but these days have little choice, I'm afraid.

Johnno, equally impressed by your making your own outboards.
I was hunting bevel gears on the net and found some reasonably small acetyl/Delrin ones, but they'd still make a big bump in the leg.  I couldn't find any metal ones at all that would even come close in diameter.
I suppose with the right bearings, i.e. a thrust bearing on the prop side of the gear shaft it should be OK.  I wonder, though, how tight a turn the flexi could make before becoming innefficient or unreliable.

The choice between the two methods must be made first, of course, then I have to see how to camouflage a modern motor, be it brushless or brushed under the bits and bobs of a model Elto 4-60 or similar. I imagine the brushless would be smaller for any given power.
If this all works, then I will definately do a model Soriano Six.  That would be a bit of a mission. Flat six, supercharged, tandem prop. outboard.  OH!!! Nursey, nursey!!
On the back of a Jacoby Flyaway hull, that would be suicide!

Regards,
Vintagent
Logged
Pages: [1]   Go Up