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Guys, hi I came down to hartsholme today to trial run the build and was made extremely welcome thanks greatly. Er motor widthThe motors are T4A from mobile marine they were extremely hot so prop size adjustment is needed. I am building again this time an inshore mine sweeper I have 50 mm graupner props on at the moment and am looking for a pair of motors to run off 12v LAB with 15 amp speed controllers per motor but cooler with out going to big I have 50mm per motor width allowance and 70mm length. I would like to keep up speed as inshore sweepers were fairly nippy 20knots real time. Is there any recommendations please ,apart from rebuild again. Regards Nobby
Hi Pilot If you are using 540 can size (35-36mm brushless motor) a 3639-1100kv 800watts, 3648-1450 1600watts or a XK 3674-1900 1769 watts. All run on 100Amp ESCs, but check the maximum voltage they handle. I use car ESCs with the electric fan on top because they run cooler at slow speeds and no water plumbing required. The same with the motors no cooling. Props for these motors 37mm 2 blade or 40-45 mm 2 blade. If you go for a larger motor for a larger prop, a L5055-700kv 1600watts same ESC, but, start with a 2 blade prop about 52mm. Battery a 3-6S 5800mah or more with a C rating of 40 plus. I have used the 35mm motors in 34 to 40" boats, but, for my 46" Vosper Crash Tender I am going to the 5055. To large a prop will cause over heating of the ESC, battery and Motor. A in line amp meter(Hobbyking 9598000004-0) is the one in use. It reads the maximum amps, so for run speed amps slow speed up to maximum as a hit the throttle hard will give you maximum amps. Canabus
Hi Ian Looking at the pics it would appear to sit correctly and certainly planes well. If your ballast is forrard it will mean it has to be lifted to plane, at the cost of increased power. If you are still using the Mtronics 600 motor the prop is about right. The specs say 6-12v so running at 7.2 v will probably account for the heating problem. A higher voltage will allow the motor to run at its optimum design speed and cooler. The stall current is 48 amps! I am assuming you have a good a free running prop shaft and tube and the motor and coupling are aligned? Can you post a pic of your prop? Dave
Thanks pmdevlin,nice bit of engineering especially the motor cooler the belt drive would take a fair bit of power from the motor but you wouldn't have to disturb the propshaft alignment when changing motors or pulleys, good photos thanks again. Steve.
HI Cenbeth As advised above brushless motors are rated by Kv. However they also have a wattage rating (amps x volts) and this needs to be observed unless you want to destroy the motor. Is this a scale model you Intend to build? I ask because you quote 58mm props and this will need large (expensive) motors and ESCs. Could be the advice Is for a brushed motor setup. If you look through this site at other members models of Crash Tenders you will find several working examples and you would be well advised to use a similar setup. Reverse with brushless ESC's Is possible but usually requires the use of a stick with a central off. You have to stop the motor select reverse for a second then select reverse again, when hopefully the motor will run backwards. The ESC's were developed for model car racing and the Initial selection applies a braking effect. If you Intend to have a very fast running model you will more than likely be using high wattage and water cooling of the motor and ESC will be advisable. Marine ESC's are available but make sure It Is reversible and as Ian advises a least 50% higher capacity than the max motor current. Whilst In-runners may be easier to cool I use outrunners which can be cooled via a special mounting cooler. Outrunners provide a big flywheel effect due to their construction and I believe give better performance In a large model boat. I have seen In-runners used In smaller model (30") and they worked fine. As you may now realise this Is not going to be a cheap option and as brushless are power hungry you will need good batteries. Top of the range are LiPo's but you need to manage their use and charging In accordance with the manufacturers guidlines. Special charges are a must and your ESC need to be programmed to prevent any over discharge. NiMh batteries will give good results but will not last as long for each sail. To get the best performance you really need to match the motor/ESC to the props and a useful tool Is a wattmeter which will help you estimate how much power different set ups use. As I mentioned at the start you should not exceed the max motor rating - basically bigger coarser pitch props = higher current. When you find a setup you think would suit I suggest you ask the member concerned for further advice. Good luck, and please post details of your final selection 😀
HI John I must admit I have bought motors designed for power tools but only used In Tugs and slow moving craft. They are quite torky but some are also rather heavy on current. If you are getting heat problems It Is because the motor Is overloaded and not running at peak efficiency. Your ESC Is getting hot because of the high current drawn. Using lower voltage motors with a higher supply voltage Is not advisable for any length of time and will more than likely burn out the brushes or even the motor coils. I know the racing fraternity favour high voltages but they water cool everything and use special motors. With your Perkassa I assume you wish to sail with a nice plane and to achieve that will you need a good high rev motor. The position of your battery and ballast will have a marked effect on the sailing performance - too far forward and you waste energy lifting the boat out of the water to achieve a plane. The other Important bits are the shaft drive and prop. The shaft should turn freely with no high spots and be dead straight. Couplings and motor need to be correctly aligned so they are dead In line. Finally the prop must be of a suitable size and pitch for the motor. Adding a larger prop or Increasing the pitch will Increase the current drawn. A smaller lesser pitched prop will allow the motor to run faster (and cooler) and your model will also go faster. I'm guessing you are using a racing type prop on your model and this may be the cause of your overheating. A good 3 blade brass prop will work much better but you still have to pick a size and pitch to suit the motor. Hope this helps 😀
My motor Is an RC Smart 3480 outrunner with an EZ Run 60A ESC. 11.1 LiPo 2000mA 3 blade 35 mm brass prop. No need for water cooling, ESC has small fan cooler attached. All up weight, boat battery motor ESC and fittings 1900gm.
The video looks great. The boat certanly moves well. However, Id be wary of going up a prop size, you may decrease the speed and Increase the current draw, especially listening to the motor sound. Possibly a sghtly smaller prop would give you more rpm's and still keep the current draw down, plus the motor will run cooler.
HI Chris, I dont think that motor will give much In the way of performance, I have use the 700 bb turbo, 12v on direct drive, and the 8.4 and 7.2 (I think!) on a gearbox reduction belt drive to give longer run time and cooler motor. You can easily over volt the graupner 700 bb turbos, the nominal voltage Is usually quite high, I use two 9.6 packs
Firstly "welcome to the site" and hope you enjoy your visits here as many others do. To go a little further about the motor cooling, If you are going to run a cooling pipe around the motor, Copper Is the best you can use, as the "metal" conducts heat so easily and quickly, wheras silicone piping would only pass water and nothing else so to speak. If you are looking for a cheap source of copper pipe, suitable for bending, go to your local car spares shop and buy some "replacement brake pipe" this Is copper based and Is bent easily around a suitable former [or dowel rod/tube]. Please try to ensure the tube/s when bent are a tight fit around your motor, It will not serve any purpose If Its a loose/floppy fit, nor will It do any cooling. you can also run a cooler pipe under the heatsink of the ESC If you wish, to aid cooling to that also, make It part of the same circuit and the less water pipes and joins Inside the hull, the safer It will be from bursts or hoses popping apart, especially when In the middle of the water !!!!! best of luck .
The brushless ESC Is now In, Its un branded but Is rated for 50 amps and up to 22V so should easily be able to handle the motor. I connected It up to the motor and It works ok just a little cogging at low speed because the motor Is sensoreless. The motor Is a Turingy 3600 KV Inrunner with a built In cooling coil, I found out after ordering It that out runners have more torque and stay cooler. (should have done more research). I'll give It a run with different sized props and voltages, then change to an outrunner If there are problems.