Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: boilerhole on December 26, 2011, 10:21:05 pm
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hi and merry xmas to you all
to start with i have little knowledge of rc equipment or the working
i have built yorkshire cobles for many years and decided to make one that would take a motor and other equipment
so what i would like to fit is lipo batteries cos there thin and long to hide under the deck a motor that would turn slow because yorkshirecobles are not fast
i have a technobot sound card which says a bec reciever should be fitted with a 6v battery and no more!!!!
i would like a simple reciever probably a planet 5 2.4 ghz
coble size is 40 inch by 9 inch so if any ideas as to what i require it would be appreciated
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Is this you?!? ;) http://youtu.be/Fe752_z49Mo (http://youtu.be/Fe752_z49Mo)
What size are your models?
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hi martin
no its not ian is a good freind who got me started and helped me a lot all those years ago and still makes some of the finest cobles around
but neither of us have done a rc model of one in fact i have never seen one so its virgin territory for this kind of mdel hence the help needed
cheers boilerhole
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sorry dont know if i said but overall size is 40 inch x 9 inch beam and 6.5 draft
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SEA LOVER
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SEA LOVER 2
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Goodness boilerhole >>:-( ....you have some explanation on this work below....... O0
Derek ...... :-)).....
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Hi,
Beautiful model,
The receiver runs on 6 volts maximum, so a 4 cell pack is the normal way to run them, some speed controller's have a circuit that supplies its voltage from the main battery pack regardless of the main pack voltage to the receiver. So in that case you do not need the 4 cell pack.
You can run what ever battery type you like, the only caveat being Lipo's should have either a low voltage cut as part of the speed control or a separate LV cut/warning indicator. Other battery types have a much greater tolerance to being discharged completely.
Brushed or brush-less motors can be used they both have low speed types, I would suggest a Brush-less motor in the order of 700 -1000 Kv and run on a 7.4 volt Li-po, a 22 mm diameter 1000 Kv out-runner will drive a 40 mm prop at about 6000 RPM, a Brushed motor set-up should have similar RPM to give the performance you desire. Say a Graupner Speed 500 E, not any other type of speed motor ok2 There are other vendors that have similar low RPM motors.
Cheers
Nick
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hi nick
thanks for the info will certainly look into the info you gave as i really have'nt a clue
derek not sure what explanation i can give to your reply but please tell and i will try to give answers
one question while im replying is the sound card says use a bec and a esc !!! are these part of the reciever or ami totally up the wrong path
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The ESC (Electronic Speed Controller) is what controls the speed of your motor, it can vary the speed and reverse the motor.
The BEC ( Battery Eliminator Circuit) is part of most ESC's. You dont need a BEC speed control, you can use a separate 4.8 volt receiver pack, the advantage of the BEC, simplicity of the wiring and better regulation of the voltage.
The sound unit can not handle more than 6 volts on the receiver connection, some people use a 6 volt Gel Cell battery to power the whole boat, and this is a problem for the sound card as a Gel can be more than 6 volts fully charged. The main power can be 6-12 volts
TO make your Coble RC the minimum you need electronicly, Transmitter, Receiver, ESC with BEC, motor, Servo and motor battery. if your ESC does not have BEC then a 4 cell receiver battery is needed
Have you got the instructions handy for the sound unit, there are diagrams of how to connect everything and if you don't understand it I/other forum members can explain what each connection is for.
Sorry if my previous post was a bit technical, It's hard to judge level of experience on a forum sometimes :-)
Cheers
Nick
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I hope this can be of help. The esc stands for electronic speed controller. From what ive read on the tecbots site, your sound card will plug into the receiver then the lead on the esc which normally goes straight into the receiver plugs into the sound card. This is to send the rec signals to the sound card to tell it to make noise then the signal goes to the esc as well so it supplys varying power to the motor. A Bec stands for battery eliminator circuit. The rec needs power to run. Some Escs have a built in bec which can power the rec via the lead which plugs into the Rec. If your Esc does not have a Bec then power can be supplied by 4 aa cells. The lead from the battery box can be plugged into a spare channel on the Rec. The tech bots card is set up to run on a bec power supply. 4.8v to 6v. Hope this helps a bit. If not or any worries pm me your number and i will talk you through things. John.
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cheers john
yes it seems to make sence so i am looking for the bits andbobs that i need to give it a go
cheers nick sorry i seemed so vague but i know where your coming from now thanks alot for your help hopefully once all together will post some more pics of how it turned out
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I don't want to Hi-Jack this thread...Because there is some good stuff going on I'd like to ask some question?
I've been looking at using some of the new motors that are out there Like Out Runners and such...But I've run into a bit of snag.
All the "Universal Couplings" I've been looking at post a warning.
"NOT FOR USE WITH A BRUSHLESS MOTOR?" Is this due to RPM constraints?
Jeff
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good question cody which i would like an answer to aswell asi have had to put a universal coupling in my project and could see ther would be more strain on it with a high speed motor
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boilerhole ....... :D ...explanation required? ...in this case is simply a term of admiration of a quality completed model O0 ....if you have any photographic images of the build they would be appreciated as we all learn from a thread that results in such models
I have no real experience in the black art of electronics or things.....and you have stated that a Cobble does not require high speed %%
It doesn't look like a speed boat or a racing boat <*< to me........I would be most surprised if your vessel would need 6000 RPM >>:-( , however I do agree that if an ESC can be $ funded it would provide good scale control over the vessel speed together with a reserve of power to counter any potential issue where you needed greater speed
Are there any similar sized Cobble hulls available from kit manufacturers?....possibly a call to some of the resellers may provide an answer & then ask for a recommendation on an electric drive system
Failing this you could post the dimensions & displacement weight of your build for Mayhem members to offer their thoughts for a "low speed" electric drive system... %)........Derek
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I don't want to Hi-Jack this thread...Because there is some good stuff going on I'd like to ask some question?
I've been looking at using some of the new motors that are out there Like Out Runners and such...But I've run into a bit of snag.
All the "Universal Couplings" I've been looking at post a warning.
"NOT FOR USE WITH A BRUSHLESS MOTOR?" Is this due to RPM constraints?
Jeff
Due to the almost universally accepted myth that all brush less motors are high speed overpowered beasts of things {:-{
I have a brushed motor, 540 sized, with a kv of 8300, the coupling would destroy itself if the motor was run at 2 volts %%
If you were setting up a FE boat then you would not use a universal coupling, brush-less or brushed ;)
Regardless of the motor if the RPM is below 10 000 and the prop was below say 45-50 mm then a universal should hold up OK.
The Brushed and brush-less motors I suggested will not damage a universal :-))
It doesn't look like a speed boat or a racing boat to me........I would be most surprised if your vessel would need 6000 RPM
6000 RPM unloaded motor RPM with a 40 mm prop, works well in a few of my boats springer etc. correspondingly lower for a larger prop, faster for a smaller prop ok2 As you said judicious use of the throttle for normal cruising :-)
Have you seen my article on Brushless for scale boats ?
Pic below is my brushless springer internals, 1000 Kv motor on 6 volts, 40 mm prop, Universal, and the mind boggling peak speed of 3.2 Kph measured with a GPS ;D
Cheers
Nick
(http://s13.postimage.org/kdd15fhz7/02032008_017.jpg) (http://postimage.org/image/kdd15fhz7/)
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Have you seen my article on Brushless for scale boats ?
Pic below is my brushless springer internals, 1000 Kv motor on 6 volts, 40 mm prop, Universal, and the mind boggling peak speed of 3.2 Kph measured with a GPS ;D
Cheers
Nick
(http://s13.postimage.org/kdd15fhz7/02032008_017.jpg) (http://postimage.org/image/kdd15fhz7/)
Got a link for that Nick?
Jeff
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http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0 (http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0)
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http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0 (http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0)
Thank you Martin.
Jeff
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http://www.modelboatmayhem.co.uk/forum/index.php?action=dlattach;topic=20084.0;attach=89307
I wonder whether this should be added to andrewh's thread?
Looks like we are derailing boilerholes thread though....
Nick
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http://www.modelboatmayhem.co.uk/forum/index.php?action=dlattach;topic=20084.0;attach=89307
I wonder whether this should be added to andrewh's thread?
Looks like we are derailing boilerholes thread though....
Nick
HEHEHE...I tried not to... ok2
Jeff
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Hullo boilerhole & Nick.........no :embarrassed: ...I think we are still on track here :-))
Again Nick ........I have no real ELECTRONIC back art wizadary knowledge >>:-(.. but a few basic principals [physics] still apply O0
I am making two broard assumptions here but these can be reapplied to alternate scales & prototype engine speeds and so are offered as an example only 8)
Assumption 1. the scale of the Cobble is 1:12 [1/12 scale]
Assumption 2. the single lunger petrol engine in the Cobble was one of those belt around the pulley to start the engine & had a top RPM of say 200 {-)........
Rule 4. Scale thrust requires that the RPM of the propeller on the scale model be increased by the square root of the scale factor
If the scale is 1:12……then the √12 = 3.46…so with an original 200 RPM engine speed multipled 3.46 = ~~~~692 RPM on the model shaft
I would be interested to read the set of calcs from boilerhole based upon his actual vessel to the scale & engine speed etc........ {-) .....Derek
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Here is an image of an original Cobble hulled vessel courtesy of GOGGLE ........the single cylinder 'lunger' engine :embarrassed: is located under the wooden box.....& leading to a very small prop ;D
http://www.coast-alive.eu/sites/default/files/article/images/715.JPG
GOGGLE also offers original example [post 1900] sized Cobble vessels as approx 30' in length...so that reduces the scale to approx 1:10...but this has little effect in the scaling of the engine speed without knowledge of the prototype %) ........
The following links are typical of the single cylinder 'lunger' engine ..... http://www.youtube.com/watch?v=bxtKzz6CvCw&feature=related ...... http://www.youtube.com/watch?v=AV6ZZ82shdU&feature=related
http://www.youtube.com/watch?v=q7l_Vy9BfG4&feature=related
Derek
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What sized prop would one of the lugger engines drive?
Nick
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:embarrassed: Nick .....I am not able to state in a factual sense.... %) ...however remembering through the eyes of an 8 year old boy some 50++++ years ago... {-) ...I seem to remember that the diameter of the flywheel was approx the same as the diameter of propeller
Now when we research propellers as originally used in small steam engined vessels of the early 1900's we find a ratio of approx 1.25+..... pitch x 1 diameter...from this I suspect that original propellers for steam engines were reused in vessels propelled by those new fan dangled >>:-( petrol engines <*<
Again a few assumptions......but they may help boilerhole with some answers............ :o .....Derek
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cheers derek
sadly i dont know of any prefab hulls for coble's that exist and has i build mine from scratch out of larch on oak i doubt you could make a fibreglass one without destroying the original
i will post some photos of the build has i took some along the way when i built it so it could be repeated if necessary although i like to make it as near to the original as possible and every coble is slightly different in character because it was designed by the fisherman that bought it for his exact requirements
the photo is of love divine which is from my home village and was built in whitby by clarksons it is a double ender similar to the coble but it has a bow at each end coble's are flat stern long time since i have seen that d/ender about dont know what happened to it
going to order the bits required today to start the rc but not quite sure whether to go for lipo or nimh might try both just to see how it balances the boat has i have put the speaker for the diesel sound emulator right at the bow and its a bit heavy so Will try to balance it out
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If the speaker is a little to heavy or large then you may wish to fit a smaller one. Just make sure the Ohms are the same ,probably 4 ohm and that the wattage is suitable. You probably will not want the sound very high. If running on a budget then old radios are a source or try your local recycling centre.John.
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dear boilerhole what a lovely model if of interest i dont know if you are uk based orion mouldings do a couple of f/g coble hulls they seem very nice seen a couple at shows they all seem to have small motors 400 size hidden under engine cover batteries under floorboards or netting etc steering is by a control rod fitted to one side of rudder if you look at orions web page under gallery some models of cobles on it some photoes on fishing forum maybe dribble but i hope of some help slug
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dear boilerhole just came across another site www.danwalker.co.uk/boats.html looks interesting slug
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Hello Derek,
1 inch prop at 5000 RPM 4.7 Mph assuming no slip 7.6 Kph
At 700 RPM 0.66 MPH 1.0 Kph
Assuming 50% slip going by my springer which is worse at 65% (theoretical 10.7 Kph actual 3.7 Kph) and I don't think our little props can achieve anywhere near 25%+ like the big boats...... Those figures above will be halved.
What do you think?
Nick
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Morning Nick......I cannot dispute calculations, however consider there is a vast difference between a springer & a cobble
%) ----- the former has the hydrodynamic finess of a floating brick with rounded corners <*<
:} ------the latter is more like an under water greyhound O0
Possibly best if boilerhole could further research :D ....to validate the actual cobble engine speed....... Derek
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Agreed. If you took that 1000kv motor and 40mm prop and installed it in a slim hull designed to cut elegantly through the water you would see much more impressive figures.
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I don't disagree with different hull forms having different speed, but you cant achieve 0% slip. I dont think the OP would be happy with somewhat less than 0.66 Mph which was the point of my calculations....
Its all speculation until the prop size is known in any case ;)
Nick