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[unicorn]

He's right though, why people are too lazy to use a spell checker beats me - it's right below the box you type your reply in, so why not use it



Mark.

       I am sure your grammatical correctness is far superior, and outshines your knowledge of 12 volt motors that are required to drive a 100mm kort
   prop by an infinite % age and should be filed under chit chat  --   lets get back to the original post by ADIJohn65.

     john do you propose using  a fixed  or steerable kort and be aware that it is the cross section of the kort that gives you the extra thrust  --  up to
     30% extra ahead  and a possible 15% negative astern on full size up to 12 knots.

[ADIJohn65]

 john do you propose using  a fixed  or steerable kort and be aware that it is the cross section of the kort that gives you the extra thrust  --  up to
     30% extra ahead  and a possible 15% negative astern on full size up to 12 knots.
[/quote]


         Wow Sorry it cause so much problems lol,

      To answer Unicorn I have picked to use MMM steerable kort so looking to get best performance. Thanks for all your replies this is the very problems i have been told about the T12 and T24 motors I would perfer to got direct drive to the prop instead of geared option.

  Thanks again for all you replies

      Regards John

[Tug Fanatic]

john do you propose using  a fixed  or steerable Kort and be aware that it is the cross section of the Kort that gives you the extra thrust  --  up to
     30% extra ahead  and a possible 15% negative astern on full size up to 12 knots........................

      To answer Unicorn I have picked to use MMM steerable Kort so looking to get best performance. Thanks for all your replies this is the very problems i have been told about the T12 and T24 motors I would perfer to got direct drive to the prop instead of geared option.

  Thanks again for all you replies

      Regards John

I am going to be interested to hear what others have to say here but my experience differs from the theory about Kort efficiency. In a perfect full sized world where the inside of the nozzle is a good (& large) airfoil shape, the prop is very close fitting to the nozzle and the prop is carefully designed to match the speed of the motor, the nozzle & the boat then I am told that it all works well & we get efficiency gains. I would also remind you that Reynolds numbers (which relate to airfoil efficiency & generally show less favourable results for small (read model) sized airfoils) do not scale.

In modelling we take a guess at the motor, a guess at the prop and buy a nozzle which probably hasn't been optimised for either (if at all). I am not aware of any proof that Kort's improve model efficiency given that an alternative ordinary propeller might be a better or worse design than the Kort example and thus render the comparison of little value. Considerations of efficiency, which effect the economic viability of a full sized tug, do not apply. There are easier ways to get more thrust than by fitting a kort nozzle to a model.

What I would say is that a steerable Kort nozzle improves model boat maneuverability enormously. This is certainly true ahead and even more true astern. To me a steerable Kort is a no brainer for maneuverability and irrelevant for thrust. I would only fit a fixed Kort for scale authenticity.

When you thank respondents for comments on the T12 & T24 on the basis of "the very problems" I am not sure which very problems you are referring to. The negative comments are mainly about 100mm props and 6000rpm 900 series motors - which the T12 & T24 are not. As far as I am aware the T12 & T24 will direct drive a 100mm prop. If in doubt MMM are very helpful. The heater motors that I have used most certainly do.

[unicorn]

 
               Hi john  --  Robbe used to sell a 12 v Power 1000 motor, revs 2200, torque up to 65n/m for driving a 100 mm glass fibre prop which was used in a submarine and three tugs kits they produced,
   its the ideal 100mm prop brushed motor and if you can locate a 2nd hand one buy it, I have one in a tug called C-11 which I converted to a steerable Robbe  Kort nozzle, the steering ahead and
   astern improved dramatically and whilst the pulling power  increased  stopping it, took longer as per full size.It also gives 2 1/2 to 3 hours sailing on a 12 volt  7 amp battery.

               If your going to use a 100mm Kort prop from Prop Shop talk to Simon he`ll keep you on the straight and narrow in regards of rpm and amp requirements.

                                                          rgds unicorn              
  

[ADIJohn65]

 Hi Tug fanatic

    I was referring to problems I have been told else where about the T12 and T24 being over priced and quote "couldn't pull the skin off a rice pudding" so i was looking for help with choosing a motor for my boat.

    Thanks for the help Unicorn will have a chat to Simon at prop shop.
  Regards John

[Andyn]

A 555 on 3.5:1 gearing would be more than perfect....

[RAAArtyGunner]

He's right though, why people are too lazy to use a spell checker beats me - it's right below the box you type your reply in, so why not use it



Mark.

Spell checkers are not fool proof as they will not correct an incorrect word eg, rite or right or wright would all pass a spell checker so which word is grammatically correct?????.
You need grammar and spell check, not to mention the spell checker has to have a full comprehensive vocabulary of English English and not American English oops
After all what's the use of a spell checker, if you can't spell, you still wouldn't know what is correct.
If the message is being conveyed and understood, well success.
Spelling as a serious discussion has been flogged to death before on this forum.

Ina oz weeez no hour ta spell

[RAAArtyGunner]

I should of said in my post that I would have geared it 2 to 1  using T5 gears and belts from Tecknobots, I tend to gear ALL my motors so as I don't need to mess with water cooling and do away with couplings, I do not find them noisy at all , toothed gears can be though but at these revs not really a problem.

Peter

Now that's food for thought 

[RAAArtyGunner]

I am even more dismayed by people who do not punctuate correctly by ignoring the need for question marks, full stops and sentences.  

If only we were all perfect!      

Ever thought of migrating to Australia???????????????? 

[nick_75au]

A similar motor to the Robbe Power 1000 is the model glow motor starters, of which I'm sure it is based on the same case and armature. Being cheap the the savings are made in the brush holders and end-caps being made of plastic and bushed rather than bearings.

On 12 volts and relatively light use the starters will be adequate but IIRC the RPM would be a bit high. I modified a pair to be used on 24 volts by rebuilding the brush holders out of fibreglass and metal brush holders from a blower motor.

A mid range 700 with a 10-12:1 planetary gearbox on 24 volts has gobs of power, the same motor on 12 volts and a 6:1 not quite so much but still very good.

My Nexus Tide which I enlarged by 2.5 times used a 24 volt motor extracted from a marine water pump was excellent as a direct drive with a 100 mm prop turned at 1500 RPM at 24 volts. Moved the boat which weighed 30 Kgs + and the hydrodynamics very nearly brick like with excellent authority.

The earlier post that recommended 1000-2000 RPM is spot on, anything more will either overpower the model or cause huge amp draw on the motor.

The Mobile Marine Motors T12-T24 look suspiciously like the 100 watt scooter motors, but they don't show RPM specifications which are vital in selecting the correct motor. Guessing here (where is the RPM?) but I suspect the BF24 will have similar spec's to the water pump motor I used in the Nexus Tide.

Cheers
Nick

[Kim]

I love Mayhem .. i really do...

You can get pulled up for spelling & grammer, pulled up for double posting ... You can get people arguing with adverts (despite the advert being subject to UK law) get a million and one opinions but when your looking for help  .... well best of luck to you!

Here is a link to a prop calculator for full size boats - Please bear in mind its from 1:1 scale but may give you a guide on how to calculate preferred motor output etc... http://vicprop.com/displacement_size.php

Problems come when predicting slip, wind & wave height in the model world .... thats assuming we can get down to that need for accuracy... our first problem seems to be even agreeing a ball park figure for rpm  ... did we even consider pitch ...
enough from me & best of luck to you!
Kim

[john s 2]

I have a pair of 12v T 12 motors in my lifeboat. They are ok but in my opinion overhyped. The run time is not particuly good. I feel the price is not worth it.John.

[tugnut]

Hi John i have a car fan motor in my Hollygarth she tows realy well also running the 100 nozle.

regards John B

[john s 2]

Car fans do seem to work well. From what i can see they are efficient and good value. I we certainly be trying them later this year. John.

[Andyn]

Why go out and spend upwards of £400 on a kit, hours to build it, hundreds of pounds worth of electronics and radio then go pull a crappy motor out of a clapped out Nova to power it? It seriously beggars belief.

[RAAArtyGunner]

Andyn,

 I suppose because those crappy motors are cheap, (I may not have enough left after forking out for the kit for another 400 for the electrics etc), readily available and outperform what suitable motors may be readily available, if there are any.

Don't know about your cars but our 'car' motors, fans, aerials, seats, mirrors, windows, etc are good quality and indeed some are branded Mabuchi.

Not to mention power tools with gearing, makes the budget go further.

[Tug Fanatic]

If you look on ebay you will find new fan motors at below 720BB or 900 prices prices. The fan motors are designed to run for thousands of hours and will turn a big prop all day and barely get warm.

I have never had a car heater/ cooling motor fail to deliver. They are silly prices for the quality & power. As an example just look at this new motor. This not an advert & I have absolutely no connection with the seller - it is just an illustration of what is available if you look. The motor comes out of the middle of the fan. Check the size of what you are buying as some can be quite large.

http://www.ebay.co.uk/itm/Genuine-Vauxhall-Cooling-Fan-Motor-Astra-F-Calibra-Corsa-B-Tigra-Cavalier-New-/190640068258?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2c630896a2

[nick_75au]

Exactly what he said. But without the spelling mistakes

There would be thousands of blower and fan motors powering model boats, I know of a few in our club that are in boats 20 years old, and that's after the service they provided in the donor vehicle

Nick

[Tug Fanatic]

There would be thousands of blower and fan motors powering model boats, I know of a few in our club that are in boats 20 years old, and that's after the service they provided in the donor vehicle

Nick

Absolutely. I still own a couple of models that are 20 years old & have motors that I freed from the scrap yard crusher. Most of the motors were open so you could see the condition of those lovely big brushes & bearings before purchasing them. 20 years on & they really haven't changed or worn at all. Unfortunately, as I posted in the "brushed motor" section scrap yards here don't seem to welcome visitors any more. I can buy a new one for less than they value their time at to remove a used one for me. £25 used or rather less new is I am afraid a no contest.

£20 for a new blower or fan motor makes most model motors look incredibly overpriced and undesirable if you are building a model that can use one. I can't understand why you would spend £400 on a model that took 500+ hours to build & then fit a poor quality model motor if you have the choice of a good quality industrial motor instead.

Free choice reigns. 

[Subculture]

Most industrial electric motors are designed for lifespans of 60-70 thousand hours of use. As most models are luck to get a couple of hours use a week, they should comfortably outlast the owner!

For a 100mm prop depending on pitch you want 1500-2500 RPM. If you assume 25 per cent slip use the following formula to calculate speed in MPH-

Pitch(in inches) x RPM / 1408

So in this case if we assume 1:1 pitch and take a median RPM- 4 x 2000/1408= 5.68 mph

[tt1]

Tyne models recommend car blower motors for use with their tug kits - obviously for sound reasoning I would of thought.

 

[tugmad]

Vauxhall Astra mk 11 cooling fan motors  perfect job.

[Kim]

They are ok but in my opinion overhyped. The run time is not particuly good. I feel the price is not worth it.John.

Run time ... Is that not dictated by the battery amps?

Like i say best of luck!
Regards
kim

[john s 2]

Run time is varyed by many things. A battery is a storage device. It is how the power is used which effects run time. Motor efficiency. Generally the more poles the better. Brushless are more efficient. Revs, hull drag, prop choice etc and the big variable how fast we run the boat. There are also losses in the speed controller etc. So throw this lot in and run tine becomes a difficult thing to work out exactly. Watching and talking to the lads at your local pond gives a good idea of things. John.

[Kim]

Run time is varyed by many things. A battery is a storage device. It is how the power is used which effects run time. Motor efficiency. Generally the more poles the better. Brushless are more efficient. Revs, hull drag, prop choice etc and the big variable how fast we run the boat. There are also losses in the speed controller etc. So throw this lot in and run tine becomes a difficult thing to work out exactly. Watching and talking to the lads at your local pond gives a good idea of things. John.

I'm no ellectrician .. but .. If a motor draws... lets say for easy maths ....1Amp and you have a 5 amp battery then the max you are going to get is ....... Drum rolll ...... 5 hours  ... seems simple to me.
Regards,
Kim