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Model Forum / Radio Controlled / Water Models / October 2004Non electronic speed controller
Running an Air Boat ( single 8" x 6 prop) and to get the full blast of power I am using 2 x 7.2v battery packs which at full charge gives up to 16.8v. It goes like a bomb but never reaches the full potential as fuses blow. Started a 10amp progressed thro' 15, 20, 25 and finally 30amp and still blowing the fuse. As electronic speed controllers are expensive and I don't wish to blow mine, does anyone know of an electromechanical controller (not a bobs board) which would cope with the power. Alternatively, any plans for a suitable one. Hoping to really Zoooooom JB why a fuse? never seen a mechanical speed control with a fuse. Just run 13 or lower gauge wire and dump the fuse. > Running an Air Boat ( single 8" x 6 prop) and to get the full blast of power > I am using 2 x 7.2v battery packs which at full charge gives up to 16.8v. [quoted text clipped - 10 lines] > > JB run it through a couple of switches set it to give 7.2 with the batteries in parallel and then full throttle run the batteries in series and ditch the fuse Kevin > Running an Air Boat ( single 8" x 6 prop) and to get the full blast of > power I am using 2 x 7.2v battery packs which at full charge gives up to [quoted text clipped - 11 lines] > > JB Kevin R I do not get the speed required at 7.2v (8.4 full). At 14.4+ it goes fast but as I said never reaches full power. I do not think my expensive speed controller would cope with the added amperage. JB > run it through a couple of switches set it to give 7.2 with the batteries > in parallel and then full throttle run the batteries in series and ditch [quoted text clipped - 15 lines] >> >> JB > Kevin R > [quoted text clipped - 25 lines] >>> >>>JB I race in the SWAMBC fast electric powerboat series here in the UK and our formula 4 guys use AStec 100 amp high frequency speed controllers these can handle 12 cells comfortably I assume that the 16.8 volts that you record are the product of surface charge which disappears very quickly so I'm unsure what you have against electronic speed control,if your controller is up to it there really shouldn't be any problems HTH  SignatureThe Goose Trolls & spammers Nuke them till they glow And shoot them in the Dark if it won't handle 30amps, it is not very good. Get a Astroflight 207, it will handle 60amps quite well. How expensive was it? An Astroflight 207D handles 60amps continuous and 6 to 40 cells at $89. http://www.astroflight.com/e/env/0001shtQU6xYrncLTs908Y2/store/store-Controls.ht ml?link=/store/store-type-tem.html&item=products:af-207dmaybe . > Kevin R > [quoted text clipped - 23 lines] > >> > >> JB http://www.jkmiller.net/ntxbg/pgOnTheWays/pgMotorSpeed.html JM >Running an Air Boat ( single 8" x 6 prop) and to get the full blast of power >I am using 2 x 7.2v battery packs which at full charge gives up to 16.8v. [quoted text clipped - 10 lines] > >JB Forget about the varible resistor unless you have a high wattage one lying about as 30amp at any resistance is going to get very hot and burn out quicker than a fuse Kevin > http://www.jkmiller.net/ntxbg/pgOnTheWays/pgMotorSpeed.html > [quoted text clipped - 17 lines] >> >>JB There must be some way of utilising the power generated to give maximum speed. There is surely an answer somewhere. I agree about the heat generation but I have the space and the weight capacity to fit a cooling fan. John Mianowski's solution would not give me the control required but is a very interesting concept for slower boats. Thanks JB > Forget about the varible resistor unless you have a high wattage one lying > about as 30amp at any resistance is going to get very hot and burn out [quoted text clipped - 21 lines] >>> >>>JB Maximum speed needs no resistance connect the motor directly to the batteries with a heavy duty switch for control and that will cut out a most of the losses and it will give you the best speed if you want some sort of control and to be honest do you really need fine control of an air boat they always run flat out normally, if you do buy a FET based speed controller 40amps + are avalible Kevin > There must be some way of utilising the power generated to give maximum > speed. [quoted text clipped - 34 lines] >>>> >>>>JB Kevin, you have the advantage - what is a FET based speed controller? JB > Maximum speed needs no resistance connect the motor directly to the > batteries with a heavy duty switch for control and that will cut out a [quoted text clipped - 41 lines] >>>>> >>>>>JB just a type of transistor in one of the modern speed controllers rather than a old style speed controller any of the small modern types will have a low insertion loss http://www.ripmax.com/FS_Access_XtraElectronics.html this sort of controller rather than one with a big bulky heatsink most you will have trouble in destroying as they cut out if over loaded or overheated just go for an aircraft one Kevin > Kevin, you have the advantage - what is a FET based speed controller? > JB [quoted text clipped - 46 lines] >>>>>> >>>>>>JB K I am currently using the Ripmax P-Xtra Volcano which is primarily a Car Controller with a heat cut-off and in theory should not burn out at the maximum power output that I can give it. Having said that, the aircraft one which I had installed initially (forward only) went up in a spectacular puff of smoke in the middle of the pond when it was going flat out.( no fuse fitted at that stage) Would the P-Xtra Volcano be any better? Costly if it isn't JB > just a type of transistor in one of the modern speed controllers rather > than a old style speed controller any of the small modern types will have [quoted text clipped - 54 lines] >>>>>>> >>>>>>>JB If you want a little more in depth description try this link: http://burks.brighton.ac.uk/burks/foldoc/12/42.htm And here is one on the most commonly used JFET: http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/active/jfet/jfet.htm Plus I like it as it comes in colour ;-) All the best Vaughn > Kevin, you have the advantage - what is a FET based speed controller? > JB [quoted text clipped - 44 lines] > >>>>> > >>>>>JB FET means Field Effect Transistor. Can treat it as a voltage controlled current source. Please concern the maximum power of the motor instead of maximum speed. Higher speed, less running time. Running at maximum power of the motor is compromise btw speed and power consumption. > Kevin, you have the advantage - what is a FET based speed controller? > JB > > > Maximum speed needs no resistance connect the motor directly to the > > batteries with a heavy duty switch for control and that will cut out a > > most of the losses and it will give you the best speed if you want some I am currently making up a basic controller as suggested by John Mianowsk in his post of 12 Oct with one or two modifications to give slow speed control. news:rpmom0d8cvlec070crj9eu3g0fk1gl2iuo@4ax.com... We'll see how it works in due course. JB > FET means Field Effect Transistor. Can treat it as a voltage controlled > current source. [quoted text clipped - 9 lines] >> > batteries with a heavy duty switch for control and that will cut out a >> > most of the losses and it will give you the best speed if you want some Starting to construct a basic controlled based on your post. Modifying slightly on lower the lower voltage to give some control at slow speeds and in a reverse (just in case I have to!) mode JB > http://www.jkmiller.net/ntxbg/pgOnTheWays/pgMotorSpeed.html > [quoted text clipped - 17 lines] >> >>JB I'm curious about modifications. Please post details when you're done. JM >Starting to construct a basic controlled based on your post. Modifying >slightly on lower the lower voltage to give some control at slow speeds and [quoted text clipped - 23 lines] >>> >>>JB |
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