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Finally the new brass propellers arrived, delayed about a month in one of Canada's regular postal disruptions. After minor modifications to the boss profile (the brass are more streamlined and thus longer than nylon) to give clearance with the rudder leading edges, they were easily installed. Could now refit the electrical equipment previously removed to get access to the shaft couplings. Inevitably took the opportunity to make “improvements”, so then could not get anything to work! After much frustration determined the problem was not from my improvements, but from the cheap and nasty slide switches provided with ESCs. These must have got damp during the test runs and corroded internally. Suggest when using these switches they be consigned to the garbage and replaced with proper toggle ones. Had decided to use the centre brushed motor/propeller for manoeuvring and low speed operation and then the outer brushless for high speed. Brushless ESCs do not modulate smoothly and motor operation is erratic. This was particularly evident when going from forward to reverse and vice versa. Using a lever control Tx, it was also easy to inadvertently operate the brushless control along with the brushed making the model response unpredictable. After some thinking, decided to insert a small relay into each of the white signal wires for the brushless motor ESCs. These relays would be controlled by a RC switch operated by another channel on the Rx. Hoping this way the brushless motors could be switched on and off whenever desired. The two relays would retain the ESCs as separate circuits and avoid any interference between them. The idea worked, can now operate the brushed motor confidently knowing the brushless will not be inadvertently triggered. This means low speed manoeuvers can be gently undertaken using the modulation and control ability of the brushless motors and, by selecting the auxiliary control, can add the high speed capability of the brushless. Am also hoping that when the Li-Pos trigger the low voltage cut-outs in the ESCs, this will retain a “get-home” facility on the brushed motor as that ESC operates independently. Much to look forward to when next on the water.
You're as BAD as me Boaty 😉 but I had a Rover 2000 with fully reclining seats back then - no problem 😁 Re 3 wires on a brushless. Simply put, this is analogous to a 3 phase AC motor (such as used in bathroom extractor fans etc). If you apply a single phase AC voltage to an AC motor it just twitches backwards and forwards in the same place as the voltage crosses from the positive to the negative half cycle. Thus 3 phases are applied giving 3 'shoves' in sequence to keep things moving. A starter capacitor is also needed to give the motor a 'belt' to shove it off. Similarly with a brushless: the ESC senses where the motor armature is in relation to the magnet poles and applies a DC pulse to the next armature coil in sequence. When you shove the throttle up the pulse width lengthens applying a longer shove and thus more energy and speed. Pulling the throttle back with a reversible ESC just turns the pulse train upside down so that negative DC pulses are applied to the motor, reversing the magnetic field created in the armature and thus the rotation. Simple really. It's the sensing and timing done inside the ESC that's the tricky bit, which is why we had to wait about a hundred years from the invention of the AC motor (Nikolai Tesla) until we could use them in models - thanks to micro-electronics. Here endeth today's seminar 😁😁 Happy brushlessing Folks, cheers, Doug 😎 Hmmm, perhaps that's why electric toothbrushes use brushed motors! 😁😜
Hi rapidair65, Most Brushless ESCs seem to assume that you are using either LiPo or NiMh batteries. It needs to know which so it can set the correct cut off voltage per cell, e.g. 3.=V for Lipo. From the applied voltage it can work out how many cells and the correct cut off. If you are using two SLA I assume 2x6V in series giving 12V. So tell the ESC that you are using NiMh and it will assume 10 cells @ 1.2V / cell. I'll be interested to hear how you get on as an SLA has nominally 2V per cell!! You should get away with it as the ESC checks the total voltage applied - it has no access to individual cells 😉 It will probably let the battery voltage go down to 11V before stopping the motor(s)😲 Good luck, Cheers, Doug 😎
Hi Martin, maybe! Maybe not! You might be lucky. Check the RX with just a servo plugged in somewhere. Then try setting up the ESC according to the instructions I sent. Basically all you have to do is tell it what type of battery you are using. Then it sets the correct 'Cut Off' voltage. BTW: since this is a 'One way only' ESC before you switch the system on make sure the throttle stick is pulled right back. Otherwise the motor will start up straight away. Mind yer fingas!! 😡 Also check that the throttle channel is not reversed at the TX - like most Futaba sets for some crazy reason - or again the motor will start up with the throttle pulled back. PDF: as Steve says; click on the Icon, then on [Download] in the top left corner. Windows should then offer you the choice of 'Open' or 'Save'. Click 'Save' and Windows will ask where you want to put the file. Cheers, Doug 😎
Hi Martin, Looks like this one XXD HW30A 30A Brushless Motor ESC For Airplane Quadcopter Which means it ain't got no backuds! But I don't suppose that bothers you. Attached is the manual as pdf. Before you can run the ESC you have to program the type of battery; LiPo or NiMH. The ESC then sets the correct cut off voltage to protect the battery from deep discharge. See second page of pdf file for instructions. The ESC has a 5V 2A BEC. If you use a separate RX battery you MUST disconnect the small red wire from the RX plug! Bon chance, Cheers, Doug 😎
I used this pump from E Bay which pumps well, and with the rubber mounts is quiet. 6-12v (I use a 2 cell LiPo which seems perfect) and am cooling 2 2000kv 28mm in-runners. Have tried a few different pumps and these have been the best so far. You have to be careful that you don't over pressurize your plumbing system, as if the hoses come off while running you can fill your boat up in no time. It's safest to adjust your pump voltage or piping to a 'neutral' pressure rather than risk hosing down your electrics. I used twin pick-ups behind the props and separate feeds, one for the pump and one direct in case the pump stopped or blocked.
Ok... Currently trying to build a Itaieri Schnellboot, ...but am questioning if what little I think I know to be correct/ workable... I have amassed the following : 3- Hobbyking ST3007 1100KV brushless motors each direct drive to 32mm plastic props.... (2 right hand drive and 1 left hand drive props... swapped over leads on on motor to get it to run as yet untested the left hand prop) 3- Turnigy nano tech 3s 3000mh 25-50C Lipo ( Have got a balance charger and board , flame proof charge bag , battery voltage check/ alarm units, and will check and charge them await the only local help I have in RC / lips battery a helicopter flyer who has no experience with RC boats ) I just read the post on WTail mixer and wonder if I need that or if my current unkowning idea to just connect all 3 ESC ‘s together to one channel on the radio , again was give Eflite Blade SR HP6DSM 2.4GHz to try out ,Will this unit work or do I need something else , currently will/ can use all 6 channels but would / could use more if I had them ... last time I had anything to do with RC was a a kid/ teen and back then you had ground radios and flight radios and the two should not be mixed .. Ok please advise , how far off am I or am I still within range of keeping it simple ? Thanks All Bill
OK, Understood, I think! If you just want to boost the bow thruster why don't you just fit a small 12V (or 11.1V LiPo) just for that? Frankly I might start with an 9.6V batt before I jump from 7.2 to 12V. I assume it's just either On or OFF, i.e. no ESC. As you can see from the specs of your Booster, as the output volts increase the deliverable current (for a given input volts) decreases inversely, as I predicted! Ya don't get summat for nuttin! Soooo, you need to carefully check the specs of the thruster motor; max voltage, current at maximum efficiency versus volts applied! That will tell you the max volts battery that you can safely and most efficiently use, and you can check if your booster can deliver the required current at the voltage needed. I'd just use a separate battery and a servo operated micro switch, but then I'm just a dumb engineer!😲 Bon chance mon ami👍 Cheers, Doug 😎
Thanks for the in-depth answer Doug, much appreciated! The component was incorrectly labelled - my fault.. it’s a Voltage Booster! Pic attached... to clarify, it’s really the bow thruster (a very small one at that!) I’d like running a bit faster, you’re right about tugs not being sprinters! Regards, Eric
A somewhat confused question if I may say so Eric!😲 You can't 'regulate up' only down. The regulator's job is to produce a constant lower voltage from a range of higher voltages. I often use one to produce 5V for the RX and servos from a 12V SLA drive battery. A little 3 legged device (type LM7805) which looks just like the power FETs in a high current ESC. My version of a UBEC! 😉 What is this 'regulator' you have? Type number? Manufacturer? Photo? To get 12V from 7.2V you would need to use a Voltage converter (also known as an inverter). This works by converting the DC input from the battery to an AC voltage which can then be increased using a transformer. More elegant (and expensive!) versions use a transistor oscillator and amplifier. This uses hi-power transistors instead of the transformer. The AC output of the transformer (or amplifier) is then rectified back to DC. All this is very inefficient which is why it is normally only used for very light currents, where the losses are not so significant, and when there is no other alternative, not often the case! You can't beat the physics and you will never get the same power out that you put in. This leads to a basic design question:- What is the total current consumption of the load? I.e. the motors. A simple example:- Let's say that at 7.2V the motors draw 10Amps total, i.e. 72W (or VAmps). Assuming a utopian 100% efficiency at 12V this would equate to 6A. Due to the three stages of conversion; DC to AC, transformation / amplification of AC to 12V, AC back to DC, you'll probably be lucky to get an efficiency of around 60% to 70%. Thus if you stick 720W in you'll get around 430 to 504W out. Not much of a gain is it!🤔 Your battery would be exhausted in about 2/3 the time it is now 😡 If your motors draw more than 10A the problem just gets worse. So what is it you really want to do? If you just want to up the volts to your motors stick a 12V SLA or an 11.1V LiPo (3S) in and hope that you don't cook your motors! Frankly I don't really know why you're bothering, tugs aren't sprinters! If you want more pulling power with the existing setup try experimenting with prop sizes and pitch. Will probably achieve much more than fiddlin' about with voltage converters. BTW: All this assumes that the RX has it's own separate 5V battery supply or from a BEC in the ESC. Some clarification needed from your side. Cheers, Doug 😎
Evening all, I have a voltage regulator I’d like to fit to my Southport tug (currently running on 7.2v Ni-MHs) in order to get it up to 12v. I’m after more speed/power and would particularly like the bow thruster running a bit faster than it does on 7.2v. So, the questions are, where to fit it in the wiring loom, and what will the effect be on the battery life? Advice please! Thank you in advance...
Don't know what happened MOTOR COMPARISON Model Number Caldercraft CEM 900T MFA Torpedo 850 Nominal Voltage 12v 12v Operating Range 6-24v 12v Type Brushed Brushed Current Cons No Load 0.4A 1.9A Current Consumption Max Eff 5A 10,8A Stall Current 20.3A 40A RPM at Nominal Voltage 3000r/min 9778r/min Prop Caldercraft 75mm The Motor I am putting in this Sea Queen is a Torpedo 850. This is due to the Caldercraft motor only manages just above walking pace.
Hi John, Yes, two or three times actually. I wanted to know the current the charger is rated for. Should be on a label or embossed on the case somewhere. Given that the calculation is easy. V=I*R --> R=V/I Given an initial charging voltage of approx 7.4 +10% = 8.14V and a charge current of 0.5A; V=15-8.14 --> 6.86 R=6.86/0.5 --> 13.72Ω so you need a 12 or 15Ω resistor. P=I*V = 0.5*6.86 --> 3.43W. So you need at least a 5W resistor. A ceramic resistor if there is enough space. Alles klar Herr Kommissar? 😉 Cheers, Doug 😎