what am i doing wrong ?

[phill dParticipant @philld]

that sounds like good info.

im only gonna try a very light prop on it tommorow, if aint quick enough ill be taking the decaperm out tommorow night.

Tonight ive seen a site on flea bay that sells 9,000mah c cells, am i right in thinking that they are 9 amp hour ?

and is a c cell the same as the car type batteries 7.2 , 9.6 volt etc

there is even a pic with 9000 written on the sides

phill

[ashley needhamParticipant @ashleyneedham69188]

Phil. Forgive me if I am talking to the knowledgable, but….

AAA AA C Dare allbattery (cell)physical sizes… ie a d cell is one of those big things that go in large torches, and vintage boats etc ;.AA common in bike lights or small radios etc etc

NiMh or indeed NiCad cells are similarly sized, but the capacity is whatever is written on thewrapping of the battery..

So… a very common r/c pack is 7.2vat. say 3000mAh made up of soldered together “C” sized cells individually having a 3000mah capacity. and at 1.2v per cell thats…oooo…about 6 cells taped together.

A 9000mAh pack will have 9Ahr capacity in a voltage determined by the number of cells. As far as I am aware c sized cells go up to about 4000mahnowadays or a bit more…but not 9 ???

Of course a 9000 pack may double up using c cells but more likely uses D cells.

Apols if this is all boring stuff. 9000mAh= 9Ahr, c cells at 9Ahr…

unlikely.

As Colin says… dont fry the `perm, flog it, buy a Graupner 600/700 motor.

Ashley.

Edited By ashley needham on 23/01/2011 10:52:47

[ashley needhamParticipant @ashleyneedham69188]

I will just chuck this in….

The MFA Seahawk i have, which is about 3 inches longer but the same beam as yours I have fitted out as per the MFA spec. (see my pics)

It has an MFA 850 motor, a 50mm X-pitch 2 blade plastic prop, and is powered by a 7Ahr 12v Gell battery and draws approx 9-10A on full power.We change the battery orstop sailingas soon as it shows any signs of slowing so we dont damage the battery.

I know it would go a lot faster with a set of NiMh cells to lighten it up, or a 700/900 motor but it is reasonably fast and more than good enough for our size pond, the lad drives it as “one of his boats” and it lasts a fair while out on the pond, intermittant fast/cruising etc.

Ashley

[phill dParticipant @philld]

Well i tried it with a 35mm prop and then tried a 50mmx prop.

if i was using it in a 6 foot ocean liner it would look good scale speed.

for a planning hull it like a few said NO GOOD AT ALL.

It stayed very cool, infact i dont think the temp changed at all after a 5 min run.

it was about half the speed of what realy want.

As for the 9000 mah batts ive seen.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=370469307968&ssPageName=STRK:MEWAX:IT

phill

[TelstarParticipant @telstar]

Hi Phil As far as cell sizes are concerned look at site, http://www.ectinschools.org/page.php?ps=2&p=941

It gives physical sizes in mm. Capacities of cells are improving all the time, but some ‘improvements’ make the cells easier to damage charging. Treat right and normally no problem. Looking at the ebay site, I don’t know but I think the pack of 4 cells are 4 off individual cells , not connected into a 6V battery (4 x 1.2v) by the supplier if so don’t overheat them as you solder them up.. Two of these packs , if you go this way, will give you a 12V 9AHr battery.

It is interesting the motor didn’t get warm, I wonder what current it was drawing.

Just a thought if you get NiMh don’t use your lead acid (gel cell) charger to charge them, it can kill them. I use a small (computerised) programable charger which will handle lead acid, NiMh LiPo. batteriesup to 24V (variable programable) and up to 12AHr bought on ebay not too expensive. It can be made to check the capacity of a battery by charge/discharge cycle and measuring the current/time integration mA/Hrs.

Cheers Tom

[phill dParticipant @philld]

I did have amp meter connected between motor and speed controller when the boat was running.

 

I saw the reading of about 1 1/2 to 2 amps when flat out using a racing x50mm prop.

 

The motor wasnt struggling at all, just no where near enough revs.

when i put a little 35mm prop on it it showed about 1 amp, but then it was realy silly slow.

I think the boat is just totaly wrong shape for this type of thing.

 

The decaperm is nice, but definitely not for me, i will have to sell it on to someone who knows about them and wants one.

 

someone told me i should go brushless, now that is a complete mystery to me.

 

what is the benefit of brushless against ordinary motors ? or is it just a gimic ?

 

 

phill

 

 

 

 

 

 

 

 

[TelstarParticipant @telstar]

Hi PhilBrushless motors, are the new approach. They are used greatly by the aircraft modellers. Mainly because they deliver more power for their size, also they are mostly more effiecent giving longer endurance for a given battery size.

Both these advantages are gained by not requiring a commutator and brushes (hence brushless). Motors and accessories specific for use in boats are now on the market (are opposed to modifying RC car or aircraft motors) with water cooled motor mounts , ESC’s and motors .Have a look at Phil Winks thread http://www.modelboats.co.uk/forums/postings.asp?th=38379&p=14

 

Having no brushes also reduces radio interferance and control ‘jitters’ sometimes introduced by brushes ‘sparking’

If you look on the other model web site ( I could be struck off mentioning Model boat Mayhem ) there are a lot of modellers ‘playing’ with brushless systems and posting their findings

hope this helps Tom

[phill dParticipant @philld]

The brushless scene is a minefield of gobbledegook.

 

I think ive just worked out that a 1300kv motor means 1300rpms per volt, but i might be wrong.

Its took ages to try and find out what all the lippo and otherstuff is.

 

and getting a simple comparison to brushed motors is almost impossible.

 

But im very suprised at how cheap brushless is when you think of the power output.

 

ive seen a 52inch lifeboat absolutely fly across the pond with brushless, and a

few huntsmans that could keep up with 6cc multi boats on the straights.

 

so mow im thinking if im going to be spending money on a new motor, then i might as well go

brushless and get the boat out to rescue my ic’s a bit quicker.

 

still not sure if i need a dedicated esc for brushless ? ive been told i can use either nimh or lead acid batts !!

 

phill

[Tony BurtonParticipant @tonyburton83970]

Hi phill

You have to have a dedicated brushless esc and make sure it has reverse cos a lot of them are made for aircraft and for some reason they dont need reverse. and you definately need nimh or lipo`s which are very scary things ( just the lipo`s that is) Lead acid dont have the oomph. Your right about comparisons…best to ask at your local model shop if you have one near.

Tony

[phill dParticipant @philld]

Hi Tony

 

I think i will be getting nimh, but ive seen a lifeboat that uses brushless and he uses 2x12volt sealed lead acids and the boats flies.

He has 2 motors in a 54 inch long lifeboat that weighs 15kilo’s, and gets 45 min run time,now that i think is very good.

The speed from it realy is fast, i would say equal to 6 cc ic engine .

He uses 2 jets for propulsion, and being as a i have a jet sitting here doing nothing im also thinking about this route.

 

Here is a link to the 54 inch lifeboat boat on video going pretty quick

http://uk.youtube.com/watch?v=Jn2QxbhaJUs

By using jet unit, it would allow me to rescue a boat if it was say caught in weeds or a reedy area that normally would kill the props.

Also allow for very shallow running again handy if on the shallows on other side of lake etc.

My jet unit has the reverse facility as well, but im now wondering what the draw backs of the jet might be.

 

I do now know that the electric side of boats is a lot more complicated than i ever dreamed it would be.

 

 

phill

[Tony BurtonParticipant @tonyburton83970]

Hi Phill I think your right about gel batteries, but they are so heavy…too heavy in my case. I am using 2 small brushless outrunners in my boat which is a seaplane tender 206. It only weighs 3.6k. if I put a lead acid in it would sink it. My motors are ony 20mm diameter and they are turning 45mm 3 blade brass props.

Look on youtube.com for “Seaplane tender 206”, I have a short clip of her at speed

Tony

[phill dParticipant @philld]

Your seaplane tender goes very well.

 

now what motor s are these exactly.

how long does it last and what batteries are you using and also what do you use for speed control.

 

I would be realy happy if i could get that performance for my boat.

 

Im now thinking of either going single jet unit, single drive, or maybe even twin drives.

 

i just need info on these brushless set ups, they are amazing.

 

it seems that a few people prefer the outrunners to inrunners as well.

 

have you any pics of the set up in the boat

 

 

 

phill

[Tony BurtonParticipant @tonyburton83970]

Hi Phill.

Now your gettin technical……I havent a clue I just read the build instructions and the guy said they were 28mm diameter out runners ( which means the body of the motor spins rather than the shaft, which means you have not to let any wiring etc get in the way.

I got them as a match set of motors and esc`s from Mtronics

By the way…….you bear a striking resemblance of Churchill

Tony

 

. They cost £49 each for a motor and esc. I only have 2 pics of them in situ and 1 is a bit blurred

[phill dParticipant @philld]

That looks a real nice neat set up.

I have heard that most of the outrunners have the outer body of the motors spinning the same as the shaft.

 

It looks realy good,did you have to get special couplings for the motor to shafts ?

I like the way they are mounted as well, is that alloy sheet ? or is it something else that has to come special with the motors ?

 

and do you seriously get 55 minutes run time at this sort of speed ?

 

ive also been told i look like alf agrnet !!

 

 

 

phill

[Tony BurtonParticipant @tonyburton83970]

Hi Phill

I cannot remember if they were groupner or robbe or even huco but they are all pretty much the same you can get them with a threaded end for the shaft and the other end plain for motor all in different sizes.all the outrunners run with the body spinning as far as I know and the in runners have the shaft spinning. yes I do get 55+ by using 2x 7.2 3300 ninh batteries one for each motor and 1 of them powers the esc`s. the motors came with a front mounting plate and I made th beds in Aluminium.

The motors have 3 connections and if you get a prop turning the wrong you just swap any 2 of the 3 round. I have quite a few pics of the build process but not any more showing the motors.

 

Tony

[phill dParticipant @philld]

Thats real good amount of run time Tony.

and if flat, by the time youve got your flask out ,had a cup of tea, had a check and clean the boat,

the batts could be charged up and ready for more, brilliant

 

you must be realy happy with the set up.

 

I know i would be ha ha

 

strange how such small motors can do so much, brushless definitely seems the way to go.

Its opening up a different world to model boats thats for sure

 

 

phill

[Tony BurtonParticipant @tonyburton83970]

Hi Phill

You can actually get rapid chrgers that run from a car battery for the nimh and ni-cad batteries, but they are not really recommended cos they shorten the life of the battery.

 

normal charging is 15hrs

Tony

 

[sean frenchParticipant @seanfrench43428]

hiya all whats the best speed controls to run 3/ 500 motors off iam trying to run up a mtb boat many thanks

[TelstarParticipant @telstar]

Sean You could:

A Add together the max current taken by each motor, and connect them to a ESc capable of carrying the total current.

B Connect each motor to a ESc suitable for it and connect the ESc’s together useing “Y” leads.

C Visit Dave Milbourn’s Site www.action–electronics.co.uk and look at the various combinations of ESc/Mixer units he has for sale. I’ve found him helpful (when approached ) with advise on suitability of choice

 

Quote “Your choice” cheers Tom

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