Forum

raf crash tender

Consider going brushless mechanically the motors are simpler ( no brushes) and they are more efficient. if you take the plunge and use LIPO batteries you can have any amount of performance. Not sure but I think an 800Kv outrunner would give you all the power you need and no gearbox needed. The torpedo motor has a recommended rating of Operating Voltage 12 volts. Current approx. 5.28A at max efficiency. RPM at 12.0v - 4289 at max efficiency. Weight 595g (approx) Shaft Diameter - 6.35mm The 800Kv has a 28A rating at 12 V so a and a bit of fiddling you can match prop to motor and get some performance

7 years ago by Haverlock

Forum

Scudder

I would agree with Haverlock's advice so far and would add the BRChobbies is a good supplier of motors/Esc and batteries. I have used them in the past and their products are 1st class. I also believe you will need a much beefier motor and ESC (your ) will give you the amps and watts used so you will be able to avoid cooking and electrics. NiMh batteries give good power but for your application you need lots of power and LiPos are the best choice. Going back to my flying days it was usual the try several different sizes and pitches of propeller before the optimum was achieved. You cannot just add any prop to a brushless motor as they require a load that enables them to work within their wattage. That is why you need a so you can check and also make sure you are not exceeding the ESC rating or overloading the battery capacity. This is important with LiPos as they should not be discharged below about 3.3v but this should be marked on the batteries. Many ESCs have a built in cut off that can be set to the correct value. Unlike other batteries LiPos change internally if abused and there have been many instances where fires have resulted. U-tube has many examples. If you are new to LiPos then you need to be aware of the correct charging procedure using a dedicated charger. LiPos should never be charged unattended and preferably in a charging bag in an area near to an outside door should the need arise. I have used LiPos for many years without incident so correct use will reduce the chance of any accidents. As with any high speed high power setup you do need to make sure everything is securely fastened and the wiring neat and of the correct capacity. I once cooked a motor because I had not secured it correctly, I now always use bolts locknuts and washers, and check the mounting before every sail. Good luck and some pics and perhaps video on water would be good to see Dave

8 years ago by Dave M

Forum

Precedent Perkasa

Thanks for the advice Dave. I'm sure Chris will be on hand to do some video if I ask him nicely. Not too sure about the mechanics of a 'quick test with a '. Can you elaborate please? Thanks Steve

8 years ago by cormorant

Forum

Precedent Perkasa

Hi Steve I would go for a left and right hand brass 3 blade prop of a similar diameter to the motors. A quick test with a should indicate if all is working within its power rating. You can then move up or down a size to correct to the optimum on water performance. You may need to water cool if heat is a problem but tghis is easily added later. Good luck with the tests - any chance of some video on the water Dave

8 years ago by Dave M

Response

Gunwhale stringers.

Hi Dave. Yes, sorry, my typo. The battery packs are 9.6v at 5000mAh, so the correct figures for the packs in series are 18.2v at 5 amps. I will correct my profile entry 🔨 I do have a in the wiring loom but as the boat has not even been in the test tank (bath) yet I have not been able to measure current under load. I can very easily re-configure the battery set-up to parallel to give me 9.6v at 10A to give me a lower 4800 rpm as an experiment but I will try it as it stands first. At this moment in time I have just put the second coat of red oxide on the lower hull so at the current rate of progress I don't see it getting it's maiden voyage until the spring of 2017. in fact I still need to find somewhere local(ish) to run it and if anyone has any suggestions? I'm in NW London. Rob.

8 years ago by robbob

Response

Gunwhale stringers.

Hi Rob Just read this post and seen your profile details re this model. I believe you may have mis-typed the mAhr figure and think 5000 (5Amp) was your intention. Putting two 5amp batteries in series will double the voltage but the current capacity will remain at 5amp. Putting two batteries in parallel will double the amperage capacity but keep the voltage the same. Using a 500kV brushless at 19.2 volts could result in revs of 9600. Your motor is rated at 57amps with a wattage of 1350. The ESC should be fine but I suspect the batteries may struggle. A would be useful to check the actual current under load. Some pics on the water would be good Dave

8 years ago by Dave M

Forum

Motor Amps

Hi Steve You use an ammeter. You can do this at the lakeside by holding the model in the water and running the motor at full power. This will give an indication of the max current drawn. it will be higher than on the water as the motor will be fully loaded with no forward motion, which will reduce the amps drawn. There are many /Ammeters available for about £20 and allow for up to 100 amps . For smaller models you may be able to use the amp range on a multimeter up to about 10 amps. The meter is wired in series with the motor and Battery. There are bits of kit that will measure the current on the water and transmit the info back to the TX. I use such a system with my TARANIS TX. There is a cost involved and if you are just starting the is a cheaper and easier to use option Dave

8 years ago by Dave M

Forum

Which type of battery?

Hi Steve I have a Billings White Star that I restored some years ago. if yours is like mine then it will most likely be on the heavy side for the size of the model. A 380 motor with a 30mm 3 blade brass prop powers mine. I have a small Action 10amp esc and homemade BEC. To reduce weight I cut a 7.2 NiCad pack into two sticks and joined them with a soldered length of wire across the bottom end. This allowed me to place the batteries either side of the prop shaft. My rudder servo is over the propshaft in the stern. Correct ballasting can be achieved by moving the batteries fore or aft. Any small 15 amp ESC would be suitable and most now have a built in BEC. The main consideration needs to be weight and size. I agree with Haverlock's suggestion re a if you intend to use the higher voltage batteries with the existing motor. Its a small boat that sails well, but on my club sailing waters it is a fair weather sailor. Good luck Dave 😀

8 years ago by Dave M

Forum

ESC problem

Hi Ashley All s are much the same. Can be sourced on E-bay but also from OK suppliers eg Component Shop http://www.componentshop.co.uk/catalogsearch/result/?q=meter&cat=0 - their 150Watt meter is £17.95. Just about to leave for the Blackpool Show so no yime to post further Dave

8 years ago by Dave M

Forum

ESC problem

Hi Ashley Your calculation is correct at full loading. I can understand your logic regarding using the ESC at 50%. This I believe will limit the voltage output of the ESC which at full loading will result in increase amp draw. In selecting a power set up it is easier to limit the current draw to about half the motor rated max, in your case 105/2 = 52 (approx) amps. Using a 7.4v battery will result in a wattage of 385 at 52 amps. You can ensure your model is running at this rating by fitting a between the ESC and motor and measuring the Watts and /or current whilst holding the model in the water. The 160 amp (max current) ESC should be good for 80 amps continuous so well within the spec for your motor. If you are drawing more current than 50amps its possible the motor is overloaded for the thrust propeller in the unit. A 3760Kv brushless is more suited to a model plane or helicopter. A brushless with a Kv of 300 to 800 would be much better, drawing less current and giving you longer sailing time. As regards the amp rating, my experience is that almost all manufacturers quote the max current value rather than the sustainable running current value. Probably why most use an ESC rated at twice the expected running current. With the wattage values you are running I would expect some form of water cooling would be required for both motor and ESC. Hope this clarifies and good luck with getting the correct setup Dave 😀

8 years ago by Dave M

Forum

ESC problem

Hi Ashley Welcome to the site. With such high currents it would be advisable to fit a fuse in the wiring to the battery. I would reiterate Haverlock's advice, LiPos need correct handling in both the charge and discharge. The lowest recommended charge (should be with the paperwork received with the battery) for your battery should be observed and should be set in your ESC. Don't store them charged, the safe voltage is 3.7volts per cell and most decent chargers have a facility to discharge to this voltage. A would be useful the check the actual current under load. Exceeding the motor or battery rating will cause damage and for about £20 a will save you time and money. The Graupner Jet Drive is interesting to me as I am awaiting two jet propulsion units from KMB for my Shannon lifeboat. There is a max rev limit of 20000 revs on these units so it is important to match the brushless revs or risk damaging the bearings. I can't find specs for the Graupner but I suggest you check your documentation. Good luck and please keep us posted. Dave

8 years ago by Dave M

Forum

Brushless

Hi Brian I am not sure which model you are referring to but your description of period photos suggests it is from the late 1930's and yes they were not a planing hull. Does your model have one or two props? A few pics of the model would help, you can upload by clicking the yellow box to the left of this input panel. Brushless can be a bit daunting at first experience but they are not difficult to use once you are familiar. You will already have seen they have three input wires and these need to be connected to an individual Brushless ESC for each motor. Doesn't matter which wired connect to which socket on the ESC but if your prop spins the wrong way you can swop any two connections to change the directiopn. The kv rating refers to the unloaded speed of the motor for every volt you apply so for say a 1000kv motor supplied with 11.1volts the motor would spin at 11100 revs. There are two types of brushless motor "in-runners" and "out-runners". This refers to the construction used with in-runners generally being less bulky. The outrunners will produce more tork and can be more suited to slower speeds. if you need to water cool the in-runners have a jacket fitted around the motor body whilst the out-runners use a water cooled mounting attached to the bearing. Both are suitable but I personally prefer Out-runners. For your model I suspect an inrunner may be preferable due to the restricted space available. Unlike brushed motors brushless do not like being overloaded and work best when they can achieve their max efficiency at near max revs. They have a max watt rating which should not be exceeded (Watts = Amps x Volts). The casing may be marked with numbers 42-56 which is the diameter 42mm and length 56mm. In my 48" Sea Queen I use a 42 size 850Kv water cooled motor of 700 watts and it is happy driving a Prop Shop prop of 42mm at 45 amp on full throttle. To measure your wattage you need to acquire a to measure the actual current draw with the model in the water. This will give an indication of the max current at max load as you hold the model stationery. If the watts are greater than the motor's rating you need to reduce the prop size/pitch. I like scale props so use 3 bladed brass and avoid using racing plastic/nylon props as they can overload the motor. The ESC should also be of a sufficient rating to handle the running current, I usually try for at least a 50% margin ie 75amps for a 50amp max current. Finally your setup must be really secure (I know from personal experience) and free running. The revs produced are possibly higher than what you may have experience before and any fault can and will escalate very quickly. At high currents the motor coils will fry in about 2 seconds should anything stall the motor and you can expect to see smoke and a ruined motor. If you post some pics we can give you more detailed help on your particular setup. Dave

8 years ago by Dave M

Forum

Speed Controller

Hi Clifford I suggest you invest in a and measure the actual current and wattage your motor and prop draw. As already said you do need a battery and ESC that capable of supplying the max current. However the choice of prop will determine the current drawn and if it exceeds the spec for the motor/ESC or battery you will have problems. Reducing the prop size and pitch will bring the current down. Water cooling is almost certainly a requirement and with very high wattages you may well need two feeds. I have a club member who is into fast electrics and he seems to manage with a single cooling supply, but he does use some state of the art kit and achives about 47mph. Good luck Dave

8 years ago by Dave M

Forum

Poor run time

HI Richard I agree with Flack. The SLA is not a good choice for a brushless motor. Basically the motor is a low resistance device that needs a low resistance power supply. SLA's have a realtively high internal resistance which limits the current they can deliver. The best batteries are LiPo followed by NiMh with SLA least suitable. Nimh batteries of 5000 Mahr capacity will give much better performance and the reduced weight will improve the models overall performance. You have not said what prop you are using but generally brushless motors work more efficiently with smaller props than those used for brushed motors. ideally you need to connect a in circuit and see how many amps the motor and prop set up is drawing. You should adjust the prop so that the current is within the range of the motor /ESC/battery. if you exceed the max values you will generate lots of heat and run the risk of damaging the motor and/or ESC. I suggest you borrow a battery of a fellow club member and see how it performs. If you have the funds and really want the Sea Queen to fly then a LiPo will match the performance of the IC engines originally installed. This is not a cheap option as you will require a dedicated LiPo charger, charge bag and your ESC needs to have a cut off voltage to protect the LiPo. Please do some research on LiPos before you proceed as they are new technology and require much more careful treatment than NiMhs. I am attaching a pic of my Sea Queen setup. Both the motor and ESC are water cooled and I use a 11.1v 5000MaHr LiPo. Good luck and please let us know how you progress Dave 😀

8 years ago by Dave M

Forum

what esc with graupner 900 motors

HI tugboatguy the specs for your motor are: Motor Nominal Voltage Voltage Range No-Load RPM NO-Load Current Current @ Max Effic. Stalled Current Max Efficiency Speed 900 BB TORQUE 12v 6-40v 6,500 1.1A 8A 54A 71% Depending on the prop in use the current on load will probably be in 10-20 amp range. With a stall current of 54 amps you could need a 100 amp ESC but a 50 amp protected by a fuse would be OK. You should always fit a fuse less than the max ESC current. The alternative is to risk a fire and probable loss of your model. I suggest you initially connect your motor to a 12v battery via a (measures watts and current) and put the model in a test tank with the chosen prop and see how many amps the motor draws. This will be the current at heavy load so you can probably halve this for normal running. With this info you can make an informed choice on the ESC. Generally you should have one that can handle a continuous current of twice your max running current. I checked on the web and ESCs are available in the 50-100 amp range. Tower Hobbies came up on a Google search but there were others listed. You will need to check carefully that your chosen ESC has a reverse function if this is required for the model. Good hunting Dave

8 years ago by Dave M

Forum

Twin Electric Set Up for Marx Chris Craft Constellation

HI Biggles Gone rather quiet on the suggestions for a brushless. I have little knowledge of the Marx Chris Craft Constellation model boat and was hoping another member would make a suggestion. It's not a large model and two turnigy d3536/6 1250kv may be a bit too much. The numbers actually relate to the length and circumference dimensions in mm and the kv rating is the number of revolutions per minute for each volt applied, so for the example a 10v battery would result in an open max speed of 12500 revs. You could try two 2826 with a kv of round the 750/1500 mark. Most sites give stats regarding the power output and current draw and suggested ESC max capacity. The larger the motor the heavier the current and dearer the ESC. Battery capacity needs to be considered as weight will be a problem even if you use LIPOs. If the props load the motor too much it will get hot as will the ESC so you may need to fit water cooling. A will indicate the current drawn by each motor and can help you keep within the rated values. There is a balance between motor and prop and often a smaller or finer pitch prop will increase the speed and reduce the amps drawn. Good luck with the upgrade and please keep us posted with your progress. Dave

9 years ago by Dave M

Forum

Twin Electric Set Up for Marx Chris Craft Constellation

HI Biggles If I may just add to Mark's reply, yes you do need two ESCs. Brushless motors run much faster than brushed and the original props on your Chris Craft may be a tad on the large size. This may cause your motors and ESCs to overheat so you need to check this on the water after a short test run. if you have or can borrow a this will help measure the amps used in the water. Brushless ESCs can be reversed via the transmitter but many do not. in a fast boat this may not be a problem but it is something to consider. as Mark says you can set the direction by altering any two of the three leads so no problem with contra rotating props. I agree with the comment about Imported ESC ratings, and whilst some seem OK many fail and its a long way and wait to get a replacement. There are several on line suppliers in the UK offering suitable motors and ESCs and in my opinion they compare favourably in price with overseas suppliers. Dave

9 years ago by Dave M

Response

VOSPER PERKASA 49 INCH KIT PART 2

Really motoring. The battery can be mounted anyway just make sure the leads are clear of the motor and remote from your radio wires. I suspect you will not be happy with the NiMh batteries. I am assuming they are NiMh as NiCads have not been available for some time. if they are NiCad then they must be nearing the end of their useful Life so another excuse to switch to LiPo. Glad to see you project successfully on the pond. if you invest in a you will be able to tune your motor to the prop and achieve max speed and time on the water. Happy sailing Dave

9 years ago by Dave M

Forum

Maytech ESC has lost reverse function

You need to check the max voltage your ESC supports as if you exceed this magic smoke may appear and the ESC will be unwell! Brushless motors are very power hungry and are capable of passing very high currents so any power supply needs to have a low internal resistance to meet the amperage requirement of the motor. SLA's have the highest internal resistance and LiPo's the lowest with NiMhs not quite as low as the LiPo. Have you checked the current being drawn with the props in the water. it is very Important that you do not exceed the max rating for either the ESC or motor so I suggest you buy or borrow a to check your setup. Brushless motors work best at their designed speed and do not take kindly to being overloaded by increasing current demand at quite alarming levels. I always start with a small prop and work up to a size that suits the setup and model - unlike brushed motors bigger props don't usually result in more speed, just higher current draw and the need for bigger and more expensive batteries and ESCs, plus more water cooling. If the 7.2v NiMh worked well you could try a higher voltage as the packs are now available in all sizes and can be custom made to your requirements but you will need high capacity cells. Several club members have Perkassa models and they use NiMhs and can sail for 20 mins depending on how fast they sail. Do remember that the ballast should not be too far forward as any weigh there will need to be lifted (increased current) when the boat goes on the plane. Good luck and please post details of how you progres as other will benefit from your efforts and experience. 😀

10 years ago by Dave M

Forum

Which speed controller

HI Richard I have just added my Sea Queen to my harbour but here are some pics that may be of interest. Sorry no on water shots. Giant Shark also do s. 😀

10 years ago by Dave M

Forum

Which speed controller

HI Richard Just had a quick look at the J Perkins website and seen the spec on your motor. This is a model plane motor equivalent to a 26cc Ic engine. Electric flight items -> Brushless motors - EnErG 4445830 26cc O/R 390 (C50-30) Brushless Motor Battery - 5-6 cell Li-Poly; Working current - 50-76A : Peak 80A; Shaft diameter - 6mm Speed Controller requirement - 85A. Sorry but in my opinion this is not a suitable motor for your Sea Queen. Its designed for a model plane with air cooling from the prop. The battery required is a 5 cell LiPo (18.5v). Popular size is 3 cell and most chargers will cope up to 4 cell but they are expensive for 5 cells as are the batteries. The motor in water will have a much heavier load than a prop in clean air so the current will be high - possibly above the rated max. You can water cool outrunner motors with a special water cooled mount that the motor fastens to as part of the mounting and this motor will certainly need cooling. A three blade prop will be fine but the ESC will need to be watercooled and at least 100 amp continuous. There is a 90amp version on the Perkins website that is watercooled. There are other brushless motors on the Perkins site that have lower specs and voltage requirements and can use 3 - 4 cell LiPo's. if you could swap this may be a good time to consider this option. If you intend to continue with this setup, buy or borrow a and battery and see what current is needed with the prop fitted and in the water. I found that using a lower voltage battery caused the motor to overheat and the current increased significantly. When you have the current drawn you can decide what ESC you will need. Personally I would double the figure you obtain from the to give you a margin of error. I do hope you can find a satisfactory solution and please ask if you need any further help 😀

10 years ago by Dave M

Forum

Which speed controller

Hi I have a Sea Queen with a brushless motor drawing about 27amps and use water cooling on both motor and ESC rated at 85 amps. I assume you mean the max current for your motor is 85 amps as the actual draw will depend on your prop/battery selection. You should invest in a to measure the actual current used then make sure your ESC is rated at least double this as manufacturer rating are always optimistic and usually relate to instantaneous max ratings rather than continuous ratings. Unless your Sea Queen has been built very heavy I suspect this motor will be somewhat over the top for scale speed. if you are using this sort of power then you will certainly need to install some form of water cooling. Unlike brushed motors brushless need to be able to achieve their optimum speed range and this is best controlled by careful prop selection. I suggest you start with a small prop and work up in size until you get the best result within the motor and ESC ratings. If you exceed either you run the real risk of damage to either or both. Not sure what battery you are using but if LiPo do follow the instructions carefully and make sure your ESC has a min voltage cut off set to the battery manufacturers specs. Hope this is helpful. Please post details of your progress so others may benefit from your experience. A video of the boat on the water would be good. 😀

10 years ago by Dave M

Forum

RAF Crash Tender Motor size

Thanks Dave Have will travel , we have been flying toy aeroplanes for longer than I can remember and have played the lipo game for 6 or 7 years so no problems , even running lipos on electric recumbent trikes . ( 2 x 7s 1p 5ah = 52v ) LIPOs are dangerous unless treated with care , so we do ! 😯 Only thing I really need to know is will it be powerful enough to look right on the water regards emma

10 years ago by twinkle

Forum

RAF Crash Tender Motor size

Should be OK Emma. Will depend on your prop. Make sure you don't overload the battery / ESC or motor ratings. I suggest you invest in or borrow a to make sure your set up is OK. Heat is one of the major causes of LiPo failure and once a LiPo has become swollen it is no longer safe to use and is an accident waiting to happen. There is a very good booklet available at http://www.bmfa.org/Info/Downloads/BMFAHandbookGuidance/tabid/221/Default.aspx. This explains some of the pitfalls associated with LiPo usage/misuse and will help keep you and your models and property safe. Your motor will be high revving and will work best at high revs so don't put too big or coarse pitched prop. I find my Crash Tender works best with a 35mm 3 blade brass prop but it is a different motor. Good luck and please post some pics or a video 👍 😀

10 years ago by Dave M

Forum

ESC problems

Looking at the spec for the MFA 850 Torpedo the max current is quoted at 10.2 amps at 12v. Assuming you are using the two 6v batteries in series giving 12v then the ESC should be OK. Do you know the actual amps being drawn by your motor? Could be the prop is two big for the motor. IC props are usually too coarse a pitch for electric motors. if you can borrow a you can check this at the bank with the prop in the water. I would check that the prop shaft and motor are aligned and that there is no stiffness in the propshaft. This is a common cause of heavy current. Brushed motors are good at generating electrical noise which will play havoc with your electronics. You need to fit suppressor capacitors: One across the motor terminals and another two from the motor case to each terminal. I use 0.1uF ceramic. The placing of the wiring in the boat should be such that the high current (dirty) wiring is as far away as possible from the signal wiring and aerial. The fact that your problem starts at high power throttle suggests sparking interference is causing the problem. The 2.4 Ghz will not be too affected but the ESC will be. Do make sure that your aerial is above the waterline in the model as 2.4Ghz will not pass through water. Hope this helps solve the problem. 😀

10 years ago by Dave M

Forum

Brushless motors -Help!

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 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 😀

10 years ago by Dave M

Response

RAF Crash Tender 46in

What ESC's are you using? Battery capacity? Do you know the max current your Thumbrun and ESC's can take? If possible I suggest you use a (a fellow club member may have one) to see what the position is at the waters edge, this will be a worst case as the model will be stationary and drawing max amps. Brushless motors are power hungry and for max performance work best with LiPo's. ideally the ESC should have a max rating greater (50%) than the max motor current. Unlike brushed ESC's lowering the throttle setting does not reduce the current flow but does increase the heat generated. My experience is brushed motors work best on smaller props. I suggest you check the heat of your setup after a short one circle run when you fit the new props. Look forward to hearing how you fare. Good luck 😀

10 years ago by Dave M

Forum

34'' GRP/Kitshak Crash tender

HI Zippy, welcome to the site. Just had a look at the Mtroniks site and see their ad says "The Genesis Hydra30 is best suited to small scale RC boats to be used at scale speeds." If this is the combo set, the rating is 1000Kv which at 7.2 volts will give you 7200 revs. This seems a little on the low side if you want a really fast model that planes easily. My 34" Fireboat uses a RC-Smart 3480 outrunner and a EZRun-60A-SL 60A Constant ESC. I use an 11.1v LiPo but it works well with a 7.2 NiMh. Prop is a brass 35mm 3 blade. My model weighs in at 1900gms all up so is fairly light. Weight is the biggest problem and you need to get the heavy bits (battery) towards the rear. You could use a 8.4 or 9.6v Nimh if the speed is too slow but this will come at the cost of extra weight so its a bit of a balancing act. Brushless motors like to run at high revs so avoid using too big or coarse a prop. The fast racing type 2 blade props will place too heavy a load for your purpose. Ideally you should invest in or borrow a to measure the current draw on your chosen set up. This will avoid you running the motor and ESC above their rated value. I have no experience of Mtronik brushless ESC's but use their brushed ESVs in many of my models and find them excellent value. Giant Shark have a large selection of brushless motors and setups and if you search the web you will find many more suppliers both in the UK and abroad. There is a section on this site Photo Gallery with a whole section relating to Fireboats and I suggest you have a browse to see what set up other use so you can have a better idea when searching. Good luck and do please post details and pics of your model. 😀

10 years ago by Dave M

Response

Aerokits 46'' Fireboat twin screw brushless conversion

HI Paul In my experience reducing the prop size with a brushless motor has the opposite effect. I usually use a to ensure I keep within the rated power of the motor by adjusting the prop accordingly. Too small a prop can allow a brushless motor to over rev so its best to try and get this right. One of the main benefits of brushless is you are able to use scale 3 bladed brass props. You mentioned Simon at Prop shop in a previous post - did he produce props to suit your model? Totally agree re rudder control. On a fast craft at speed very small movement will have a large effect. Are your rudders that length to align with the depth of the props? With that sort of speed you could add wings and it would probably take off! Very Impressive. 👍

11 years ago by Dave M

Response

Motors and speed controllers

HI Shaun Glad to hear you have spoken to someone with an actual set up. As regards the ESC you really need one that is capable of handling double the power requirement of the motor. Does the man in the shop race model boats and have personal knowledge of the JP? Manufacturers always seem to give optimistic ratings for their products and whilst the tests may be OK in the real world the performance and output drops off as the max rating is approached. If you are intending to run your model at this sort of level then you will need to water cool all the bits. Not sure if you know the formula but Watts equal volts time amps so say 12v x 40a = 480 watts. I suggest you also purchase a so that you can ensure you do not overload the motor or ESC by fitting too big a prop. As regards forward/reverse running This is usually a bit of a pain as the ESC requires you to stop the motor select reverse return to neutral then select reverse again. in my experience this requires that you keep the stick spring an your tranny as the neutral position is fairly critical. Your knowledge is increasing every day and I am so glad the you are sharing the experience for others to follow. 😀 Smiley's appear on the right of my response screen and I just click on one to add. I suggest you clear your computer cache and see if that clears the problem.

11 years ago by Dave M

Forum

twin brushless motors

HI Dennis Yes you must have a seperate ESC for each brushless motor. Brushless motors regulate their speed by communicating with the ESC so they have to have their own controller. I have always used separate receiver channels foe my brushless set ups but I believe a y lead should work. Many ESCs have built in BEC circuits so you may need to break one of the red ( ve) leads between 1 ESC and the Y lead. I suggest you amend the Y lead by pulling out one of the ve connectors on one of the leads to the ESC. Brushless motors are high current users so separate batteries should give you a longer run. For best results you really need to use a to measure the load so that you can select the correct props for your motor, ESC and model. Too big a prop can and will burn out either the motor or ESC, you may well need to watercool both for fast prolonged running (racing). I am assuming you are using NiMh batteries so will not need to worry about discharging the batteries below their minimum permissable voltage. Should you be using LiPo's then please advise so that I can advise you further. Good luck 😀

11 years ago by Dave M

Forum

Brushless Electric Motors

HI Folks Being a toy aeroplane flyer primarily and have a few motors laying around I am going to use a 3530 outrunner 1100 kpv motor and Esc from Giantshark about a tenner for the motor and a 40amp esc a tenner , in my RAF crash tender and a 2200 3s if if is too quick I can always use a 2s pack I will use a computer fan to cool the esc and duct it to the motor prior to running sea trials I will test it in the bath with a just to make sure it is with in specifications regards emma

11 years ago by twinkle

Forum

Motors and voltage

HI Jim If you Google Graupner with the motor model number you should be able to find the spec for your motor, including the max volts. The Important bit is the Power rating (ie Watts which is the product of the voltage and amps). if you exceed this your motor will overheat and could therefore fry. You can buy s (Giant Cod) that allow you to measure watts, amps and volts. Useful when selecting the optimum prop for your motor. The other consideration is the speed controller(s) max voltage rating. They would need to be suitable for greater than 15 volts (LiPo are 14.4v). if you exceed the max voltage rating you run the risk of cooking the ESC. May not happen Immediately but I believe the damage is cumulative and in my experience usually goes at switch on. Good luck and please post your experiences 😀

11 years ago by Dave M

Forum

ESC help

I have used this size motor with 14.4v with no problem but I wouldn't exceed the voltage rating of the esc- you probably wouldn't get away with it for long. My recent experience has shown that Lipo batteries are a great way of saving weight and delivering more amps to the motor. NiMh batteries tend to drop voltage a bit when a lot is asked of them whereas Lipos will give what the motor asks for. That 700 motor would do well on a 3s Lipo and you could make adjustments to the prop size to manage speed and current draw. My Wavemaster in the video section has a 700 motor on parallel 3s cells- but the esc is an Electronize 30amp which can take more than 12v. I do use 3s batteries in another boat with 700 motors with a an Mtroniks 40amp esc which has a 12v limit. There is a lot of info on the web and on here about using Lipo cells and determining current draw. The only sensible way forward is to be able to measure current draw with a with the boat in the bath. This will then tell you what is going on with various props/motor/battery combinations. Buying one saved me a lot in burnt out esc's! Good luck with it all. Ian

11 years ago by ianed57

Response

Veron Huntsman 28

I agree about the - essential piece of kit I'd say and yes, I too haven't burnt out an ESC since having one- a regular occurrence before! The data logger sounds very technical- I'll borrow my daughters Garmin that she uses for running and see if that is any good.

12 years ago by ianed57

Response

Widgeon- a refurbished Wavemaster

HI Graham, Yes I remember your Wavemaster- I think we had a conversation about the photos at Portishead. I have to say I was delighted with the look and performance of this boat and without suggestions from folk on this site it wouldn't have been so successful. I'm using a Graupner 700 on two 3s lipos in parallel with a 37.5mm X type prop. I'm using two lipos because I wanted them in the middle of the boat-one either side, so I made up a parallel connector. The suggestions which have helped me have been to use lipos, buy a and to try ModelBoatBits rubber couplings- all brilliant! I'm just in the process of stripping paint off an old Maycraft Mercury and I must say, I prefer to build from new materials and not having to work round someone elses bodges! Ian

12 years ago by ianed57

Forum

NewBe Help Needed - Noisy Motor Arrangement

Just catching up on this Neil. Good news eh? The only thing I can add to the good advice already given is to pass on advice given to me by Dave- if you think you will carry on with this type of boating it's well worth investing a few quid in a - best thing I ever did! it takes all the guess work out of matching up motors, esc's and props- it'll help with setting up the driveline too. This is assuming you haven't already got one. Good luck with your restoration. Ian

12 years ago by ianed57

Forum

LiPo discharge

HI Dave, Thanks for that. I did buy a couple of 3s 2650mah 33C batteries from my local shop just before I left for a weeks holiday- where I am now- so can't wait to get back and give them a go. I will check out your link as I would like bigger capacity batteries eventually. I found the I bought can also be used as a balancer which is a good double check- in fact after storage charging my batteries they were a bit out of balance. Still lots to learn but all interesting. Liked the Pilot Cutter by the way- heavy boat! All the best...Ian

12 years ago by ianed57

Response

veron fast patrol boat

Brian, Ouch! Sounds a bit expensive.On the advice of Dave M on this forum I bought myself a and it certainly takes the guesswork out. I went through three esc's on my Lesro Sportsman before I got it right- hopefully! Also spent a good deal of time anxiously waiting for my Rapier to drift back to shore after it popped a fuse- twice. Now I know what the limits are and I just didn't have a big enough fuse in. I'm having just what you describe with batteries being too far astern- I'm going out Monday to try them in the middle of the boat. Also hoping to get some LiPos when I have decided on a make. Hope the new motors and fans work out and that you get some good shots on the water eventually. All the best...Ian

12 years ago by ianed57

Response

Lesro Rapier

Dave, I found that the Nimh batteries were dropping off to around 9v at full power when measured with the and this is why I want to go for Lipos, one on each motor. At the moment I'm taking everything from one pack and I think this is the limiting factor. When I get my Lipos I will stick them in the middle and try larger props, probably 40mmS types to begin with, having measured what's going on with the first. it may be that the existing props will do better if the batteries are delivering up what the motors want. You're right, there is still plenty of headroom with this setup. Just got to rake up the cash for two largish capacity Lipos! The is a splendid purchase- I'd say essential for this type of thing. Anyway, glad you liked the video- she still looks quite good toodling around at that speed. All the best...Ian

12 years ago by ianed57

Response

Lesro Rapier

HI Ian See you are making good use of the 😀 Like the video and agree the balance could benefit with a bit more weight amidships. Listening to the video sound suggests your motors are not developing full power so I suspect the NiMh's are not capable of delivering the amps required. You could try smaller props with the NiMh's to see if the performance Improves, could be your motors are working just below the optimum.

12 years ago by Dave M

Response

Lesro Rapier

I got my yesterday and had an initial play with it with boats on the bench. Very easy to use and understand. it also serves as a battery balancer and servo checker, so all in all a useful piece of kit. it will be good for checking batteries at the pondside too. Ian

12 years ago by ianed57

Response

Lesro Rapier

HI Dave, Today I have measured the current drawn with both my Lesro boats, Sportsman and Rapier, held stationary in the bath with the equipment I have, namely an Electronize ammeter reading up to twenty amps. Each 700 9.6v motor on the Rapier read in excess of 20 amps with a 37.5mm X prop on 12v- the esc's are rated at 40 amps. The Sportsman read 17.5 amps with a 40mm prop on 12v and in excess of 20 amps with 14.4v.The esc in that is an Electronize 30 amp. This is all a bit rough and ready but is all I can do until I get a - but it looks as though I may have a bit of headroom with both boats. I have just come down from my workshop having fitted fuse holders to all my battery packs in the positive lead next to the battery. So I'm getting there. Thanks for clearing up the business of current delivered by Nimh batteries and for your interest and help in all this. I may have enough information to purchase some LiPo batteries now - or I may wait until I have done some tests with a . I was also looking at low voltage alarms on Giant Shark but they seem to get mixed reviews- as do some of the s. Regards...Ian

12 years ago by ianed57

Response

Lesro Rapier

Very helpful Dave, I was interested to hear of the existence of a device to protect the LiPo's from over discharge- I will talk to my local chap about that too. I understand that the will work with all batteries, just concerned that in trying to ascertain the requirements for a LiPo, the Nimh wouldn't give me a true indication of the potential amount drawn by the motors if the Nimh can't deliver it. I think,in reality,there will a large amount of headroom in terms of a LiPo's C rating. For example, a 4ah battery at 20 C could deliver 80 amps (right?)- I can't Imagine drawing that much current but I'll let you folk know how I get on! Regards...Ian

12 years ago by ianed57

Response

Lesro Rapier

HI Ian Just to clarify - the works with all types of battery and gives the actual watts used based on the current drawn and volts present. (watts = amps x volts) Voltage cut off is present on most brushless ESC's and the latest Mtronic offerings have this built in. Your local model shop should be able to advise on a suitable add on device to use between the battery and your ESC. You will only need this to protect LiPo batteries. Totally agree we need to support the local shop.

12 years ago by Dave M

Response

Lesro Rapier

Thanks Gregg and Dave, I have learned a tremendous amount in a short time about all this and was in conversation with my model shop owner who is a flyer and uses thee batteries all the time. He uses a fireproof bag all the time and always charges on 'balance charge'. My first purchase will be a so I can ascertain more about what's going on with my boats. I'm still not sure if what I measure with Nimh batteries will pertain to LiPo's as the Nimh is likely to give up less current- thoughts? Do I need to buy a LiPo to measure performance to see what LIPo I need? I'm also unsure about how to ensure that LiPo's are not discharged too much during use- I understand some esc's have a minimum voltage cutoff. I have spent a good deal of time perusing Giant Shark's site but will probably buy my battery from the local shop just to support him- and to benefit from his experience. I know I will pay a bit more but when he's gone he's gone! Thanks again for the help and interest in all this. All the best, Ian

12 years ago by ianed57

Response

Lesro Rapier

Ian I use the fireproof bag when charging and never leave the battery and charger alone until the charge is finished. Each battery has the charge rate marked and you exceed this at your peril. Damaged cells are not always obvious but the following events can cause problems: Dropped batteries; Discharging below minimum voltage; Overcharging above the max voltage. if your LiPo has a "puffed up" appearance it is likely it has been discharged below the minimum voltage. I dispose of any I find as I would not trust using them in my model. if there is a problem then the bag contains the hot bits of metal that eject from the battery. LiPo's can disintegrate very quickly (chain reaction) and it is best to be safe. Giant Shark are selling bags for £2.50 so they are not expensive. Regarding C rating this is the maximum current a battery is designed to deliver. For example a 2200 milliamp battery rated at 20C should be able to provide 44 amps (2.2 x 20). I suggest you look on the Giant Cod site and read some test results on different batteries. Not all batteries can deliver the stated rating and this may explain the price differentials seen. Using a allow you to ensure you are not overloading the battery. LiPo's are (in my opinion) the best form of power source for high power models but like a high performance car they need to be treated with care and operated within their ratings. 😀

12 years ago by Dave M

Response

Lesro Rapier

Gregg, I have no doubt about the benefits of Lipo's, I was just worried about safety, but having spent a good deal of time researching LiPo's today and also looking at the different types on Giant Shark I feel much more knowledgeable now- I think I would still want a fireproof bag though! I was reading a site today where the chap said he always uses balance charge and it seems to make sense. I've been wondering about the C rate needed- presumably the only reason not to go too high being cost? Thanks all for the encouragement in this area- I feel it must be done. I'll try a 2s for my Wavemaster before progressing to bigger things I think.A seems a sensible purchase too. Ian

12 years ago by ianed57

Response

Lesro Rapier

Thanks Graham and Dave, I think I will explore all possibilities using Nimh on this boat before trying anything new- the old braincells can only cope with so much. I have only run my Rapier once and there are various things I can tweak. During that session I swapped the leads on each motor and reversed the function controlling the esc's and there was a marked Improvement in performance- no idea why. Having said that I have been doing some fairly constant research into LiPos and feel a little less fearful. I have a Sigma intelligent charger, but it's not the intelligence of the charger I'm worried about! I expect I will get there eventually- I have found out more about balancing and the risks involved. I intend to use a brushless setup in my Waverider for the first time- so small steps. I will certainly explore the idea of a to find out more about what's going on. All the best...Ian

12 years ago by ianed57

Response

Lesro Rapier

HI Ian and Graham Glad to see you are using LiPos. The 3v minimum is very Important and many newer high capacity cells advocate 3.2volts. Mtronics have redeveloped their ESC's to allow for a cut off voltage to be set, but it is possible to buy an add on that will perform the same function. The model Aero flyers have used them for some years. Totally agree about water and LiPos, they don't mix. same goes for a balance charger. I suggest you borrow or buy a and see exactly how much power your model is using. Both the motor and battery have a max rating and will work best when they are operated below this max. if you are exceeding the motor rating then you either need to change the prop or increase the motor size. Your battery can then be chosen to meet the demand. Good luck with your models 😀

12 years ago by Dave M