hi all, i have a problem with my prop shaft, every time i start the Hobbyking Brushless 3660SL (3180 KV ) the prop shaft comes adrift from the boat hull. it's powered by a 14.7V Poly Lipo battery. is it too powerful for an Aeronault Queen 36"? or is the prop shaft vibrating because of out of balance propellor or the coupling? i have used Heavy Duty Araldite to glue the prop shaft on to the boat. it has come adrift 2 times now.
Traderman - whilst I am not an expert ( I am currently trying to decide what brushless combo to fit to a 34" RAF Crash tender) - clearly your motor is turing your prop shaft way to fast. With your motor spec of 3180 kV and a 14.7 V Lipo - your motor will be trying to turn your shaft at a speed of somewhere in the order of 45,000 RPM !! Firstly your prop shaft may not be rated for anything like this speed and secondly any slight mis alignment will likely be generating significant vibration - enough to cause your problem- have you noticed any? As to motor power - the motor may not be too powerful - but certainly dropping to a lower kV motor say 1100 and reducing the Lipo voltage to a 11 or even 7 volt system might be the right answer......but as I am finding its all a bit suck it and see... Peter
I would also suggest that you look at the coupling and fitment of your prop shaft. It could be that the whole unit is seizing together. You also need to check it is true and free running.
You need a prop and locknut followed by a thrust washer then at the inboard end a thrust washer locknut and coupling. There should be a gap between the thrust washer and bearing of a few thou', we used to use a Rizla paper, Make sure all joint are tight and that the shaft turns freely and smoothly.
The motor need to be securely mounted to a good solid base and 100% aligned with the coupling and prop shaft. Personal experience tells me you don't get a second chance with brushless, you have been fortunate if it is only the prop tube has suffered.
Is your hull wood, plastic, fibreglass? Whilst Araldite is a fine adhesive you may need to use Stabliz Express or UHU Acrylit Plus which provide an exceptionally strong joint. E-bay have sellers of UHU in the UK.
Hi traiderman I am no expert. dont forget, as pmdent highlights, you you multiply the KV by the volts of the supply to get the RPM of the prop. so you can play with the volts supplied or the Kv of the motor or both. regarding the vibration, have you supported the outer end of the shaft? if the shaft leaves the hull and has a good amount of unsupported shaft the end of the shaft effectively will scribe a circle. At the speed the shaft is turning and with the pressure on the prop this may cause your vibration. Richard
Hi traderman I suspect something is bent.Shaft,tube or both. Take them out and roll them on a flat surface to check. You can try to straighten them but better to buy new. When installing roughen the tube a bit and use one of the glues already mentioned or go on Master Bond site and ask them.Or use Gorilla original with the tube well clamped or taped in place. Also check if the mounting is dead straight too or you could end up bending the new assembly too as you press it into place👍
hi Richard, Thanks for the info, i have decided to remove the Prop and check it for straitness, before i start again with rebuilding using a heavy duty coupling and a slower motor, as i think the existing motor is just too fast at 47000 rpm for the propshaft and coupling and if the propellor is slightly out of balance then the prop will come off again! Thank you Richard and all other contributors that have helped! Graham
Hi Traiderman, How long is the propshaft and tube???? The reason for asking is that if the shaft is more than 6 - 8" and of small diameter, 4mm, it is likely that the shaft is whipping inside the tube, a 1000kv, ish, motor with if needed some support bearings inside the tube, what model is being fitted???
Hi Mark, The Prop shaft is 14.5 " long.i don't know the make but it's the normal prop they sell with brass bushes. i have just taken the shaft out of the prop Tube to see how bent it might be but it looks very straight to me and if push it through the tube it buts up to the middle of the motor spindle and seems inline to the motor spindle. i can't see how i could fit an extra bush into the tube. can you recommend a prop with bearings that would do and where to order from? Thanks Graham
With that setup you are trying to make a boat fly :-)
Several members of my local modelboat club is running the same setup as I do with my Classic. And that is a Graupner Compact 260Z 1380KV for the Classic 2S is more than enough and 3S will still make the Queen fly over the water. So a 1100KV on 3S with a 3 blade semi racing prop will do a great job.
You could also cut down on amount of "S" on your existing setup and program the ESC to slow start.
Hi Boatshed, i have just ordered today, an aligner tool for when i rebuild the prop shaft, i didn't know they exsisted when i installed the prop shaft the first time! But the prop-shaft does seem to be inline to the motor spindle..... and the prop shaft is straight, so i think maybe the propellor was out of balance. but i think i will reduce, the next motor KV size to about 1100kv - 1300kv. Thank everyone for their help, very much appreciated! Graham
Hi Graham, a 14" shaft is definitely going to whip inside, do you have access to a lathe? if so remove the rear bearing and push a plastic bearing into the tube, move it in about 10" then insert a second about 5" then replace the outer bearing, this will help the shaft to stay central in the tube. An alternative, fit a shorter tube and shaft closer to the hull exit, this will also lower the motor so beware that you need the space enough to fit it.
Hi Graham, are you a member of a local club??? or do you have a local machine shop who could make a couple of plastic bearings for you??? alternatively you could make some with a drill and a couple of files. Most shafts are only held at each end, so a possible remedy would be a thicker shaft, 5 - 6mm but would need replacing the tube
What about adding a prop shaft support under the boat I useually add one something like this. I have never had one this strong looking but all ways had one just before the end of the shaft. you could also add one inside the boat or even a shaped wedge under the prop tube inside the boat. This will also help to stop any side whip on the tube.Another thing that I was taught was to do away with the leading edge of the rudder. Only have about one 16th of leading edge as this stops the braking effect when turning the boat at speed. That worked wonders on stopping the boat from digging into the water and doing tight turns as well. I'm not as experienced as a lot of the people on here but these are tip's I have learnt from others. Happy boating.
Very nice but I think our friend's prop tube comes through the keelson .The wedge shaped keel extension piece to which the tube is secured so that support would not suit. However a "U" tube or two could be fabricated and wrapped round tube and secured to keelson with a couple of small screws and a good glue.Ali .copper or brass would do. Brass best to avoid electrolytic corrosion with the brass prop tube. Also brass screws. BTW just looking at shaft is not enough to check if straight. Hold to a known straight edge or rolled on flat surface. This will show up even the slightest curvature by allowing light under the ends when rolling with the fingers in the middle. Or slide a piece of paper (cigarette paper best ) against ends .If it goes under there is a bend in the test piece 👍
Graham - don't tell me you ran the boat at anything like full throttle. If so, it wouldn't just be the prop shaft that you'd have to worry about! If you did it must have been virtually uncontrollable!
I take it you bought the boat with the motor already in it? Whatever, it couldn't really have been a worse choice! With such a high kv and being an inrunner (if I've got the right motor) it's really meant for a lighter, race type boat running on 2S to keep the revs down to a reasonable level.
As you now know, for your type of boat you need a kv around 1000 or even a bit less as torque is what you need and also go for an outrunner. 3S or 4S is fine and if it is too fast limit the amount of throttle.
Without seeing photos it's impossible to say if your existing prop shaft is up to the job but as you've removed it anyway and if you don't mind the expense I'd change it for one of the Raboesch maintenance free ones. I'm using these for my builds and my Fairey Swordsman at 33 inches is a similar size and weight. These are rated for 10k. and 15k. rpm, I've gone for the latter and in 5mm shaft size to be on the safe side.
I doubt that a shorter prop shaft will be feasible as usually the motor is already pretty low in the boat and a shorter shaft will increase the angle and you don't want it too steep. Also you would have to redrill the hole for the different angle. What dia. is the existing prop shaft?
The other thing you need to consider is the prop. What are you running at the moment?
Hi All I am using Hobbyking 3639-1100 and 3648-1450kv motors in that size boats(Sea Commander, Precedent Huntsman and SG&K Gentleman's Runabout). 60 Amp ESC with either 3 or 4S Lipo batteries. Props 2 blade 40mm 1.4 or 1.6 pitch. The motors are a straight change over and the only change to the ESC is the low voltage setting for the 3S and 4S batteries. Canabus
Boatshed - as regards the rudder the part in front of the spindle is to balance part of the force acting on the rudder and take some of the load off the servo or in the case of a full size boat off the wheel.
If a boat is turning too sharply or experiencing "braking" then the rudder is either turning too much or it's too big.
I always use as smaller rudder as I can get away with. I had been running model boats for many years then one day when on Blackheath pond someone was watching my boat and remarked on how it turned. badly, and I replied that's how it had always turned. The guy had a boat the same as mine it was a MFA Spearfish, He asked if he could swap rudders on my boat and try his on my boat so that's what I done and it performed much better on the water. I then tried it on my Vosper RAF Crash Tender and it just stuck to the water on any turn tight or wide. So I have done this ever since. On my Huntsman I had turned it over several times before trying this so I done the same on this and once again it was a lot better turning and didn't turn over. I don't like using large rudders if I cannot get one small enough for what I wan't I will get one and then cut it down. We used to race 5 or 6 boats on the water at a time and always needed to turn tight turns to get round the pond. Even watching Power Boat racing on the telly in the past they make tight turns to get round. I have a Probaot Miss Geico tunnel hull and straight from the box brand new the rudder on that has no leading edge and I can turn that flat out on the water with no roll at all. I suppose I am a speed freak and it has worked fine for me. Even if it is the wrong thing to do. The small avatar picture on my posts is a boat I have in Norfolk. This has a 1960 Volvo Penta outdrive probably one of the earliest one's made and that doesn't like to turn on 3/4 throttle without the engine revs dropping and digging in on a turn. I have tried this when out on open water up there. Don't try it now as got a warning from the Norfolk River Constabulary. Don't want to loose my river licence.
Hi All, a lot of info, i need a complete change to the power train setup. canabus setup looks good, i think i will follow that. what size in diametre prop shaft did you use, 4 -5 mm? have uploaded some pictures of the boat, complete with offending motor! and 1 of the resulting damage to the 3 blade brass propeller, which i think was out of balance, so, can't take the speed of rpm? probably need a racing propeller? There is room for 2 lipo's in parallel. Thanks Again Graham
HI Graham. Every picture tells a story!!! The motor is definitely wrong, its designed for racing, low torque, mega revs, not for scale boats. What diameter is the shaft tube??? looks thin??? did the prop shear in the water?? would explain the vibration and damage to the shaft mountings, try a Raboesch shaft, with a ballrace at the motor end, great quality, also they do a huge range of props, google the name there site will come up.
Hi Mark, i have a 4mm shaft fitted and the boat was out of the water at the time, it happened when i just touched the throttle! i thinking maybe a 5mm shaft would be good (less whipping)with a racing propeller and a 1100kv motor with a rubber heavy duty coupling, i think that would be a good setup and will be suitable for a 3ft boat. i think the brass propeller is just not built for high revs, or was it a 1 off badly made propeller? anyway would that setup be good? thanks Graham
Hi Graham, all agreed with you post. But. The last photo looks like the blades are soldered or brazed on, that is a week point, but looking closely the blade appears to have sheared of above the hub. Your hull is not really a high speed hull, so a racing prop might cause instability, i would suggest a cast prop, (propshop) and possibly 3 blades 40 - 45mm with your 1100kv motor would give good speed combined with good run time. The 5mm upgrade is also a great idea. A rule of thumb is don't exceed the diameter of the motor. Mark
Hi Mark, all good stuff, as ever from you👍 Just one thing; Prop Shop has ceased production after the fire they had. Probably only still trading until rest stock is sold and the business then wound up. 🤔
So I would go straight to Raboesch http://raboeschmodels.com/index.php/en/ (or Krick here in Germany) for cast props and suitable matched shafts. You can download the whole catalogue from their site to browse at your leisure 😉 This is the announcement on the Prop Shop site Cheers Doug 😎 http://www.prop-shop.co.uk/ "Welcome to the Prop Shop web site.
AS YOU ARE PROBABLY AWARE A FIRE IN APRIL 2017 SERIOUSLY DAMAGED OUR PRODUCTION FACILITIES. SINCE THEN WE HAVE BEEN NEGOTIATING OUR CLAIM WITH OUR INSURANCE COMPANY.
JUST BEFORE CHRISTMAS A SETTLEMENT WAS REACHED. REGRETTABLY THE AMOUNT WE HAVE BEEN PAID IS NOT SUFFICIENT TO ENABLE US TO FULLY RE-ESTABLISH OUR PRODUCTION CAPABILITY.
WE MUST ADVISE THEREFORE THAT THE DECISION HAS NOW BEEN TAKEN FOR "PROPSHOP" TO CEASE TRADING.
WE WANT TO THANK ALL OUR LOYAL CUSTOMERS FOR THEIR SUPPORT OVER MANY YEARS AND SINCERELY HOPE YOU FIND SUITABLE ALTERNATIVE PRODUCTS THAT MEET YOUR NEED.
PROPS SHOP TEAM
January 2018" 🤔
Young at heart - slightly older in other places 😉 cheers Doug
Hi Graham Now we can see the actual prop shaft and motor it is clear that the shaft is not supported inside the hull close to the coupling. At the high revs your motor achieves I am not surprised you have had problems. I do agree with all the comments and help you have been offered and agree a 5mm shaft would help as well as a different motor. I use 3 blade brass props with brushless and have no problems but do keep the prop size to a diameter no greater than the motor diameter, as Mark advises. It's difficult to see how much space is in the hull to allow the motor coupling and shaft to be closer, but if you are replacing the shaft it may be a good time to reposition the motor and the shaft with the prop attached to a slightly different angle. This will mean opening the slot and perhaps enlarging the outside skeg but you can easily repair any damage with plastic padding to make good. Even if you keep the existing arrangement I suggest you provide support for the prop shaft close to the bearing as I suspect this is where you have experienced the problem with the vibration. A simple 2" block of wood attached to the keel and shaft would suffice. Model looks very good and I look forward to seeing some on water shots.
Hi I use 4mm stainless steel shaft with a brass or roller bearing at the motor end and a Teflon bearing at the bottom. Grease I use Dow Coring Molykote Compound 111. A squirt in each bearing and install the shaft with a finger over the inner bearing( the air escapes via the oiler tube) and cap off the oiler. I the picture is the shaft support on my Huntsman which is a slide fix for the prop shaft tube.
Hi Doug Thanks for the update on PropShop. I can't find a way to order from Raboesch, they seem to have agreed distribution with Jotika who have not yet set up to take orders. The Raboesch web site directs me to the USA for distributors! Cornwall Model Boats do stock so all is not lost.
I get my Rab stuff from Krick, they do the full prop and shaft range. http://www.krickshop.de/Products/Accessories/Accessories-for... Excellent service, I get my order usually the next day, max 3 days. For 'other countries' they say 3 to 7 days for delivery, which ain't so bad😉 Just bought two 30mm M3 props from them to replace the nasty plastic things on my HMS Belfast. Ordered Wednesday - arrived Thursday😊Happy hunting, cheers Doug 😎
Young at heart - slightly older in other places 😉 cheers Doug
I get my Raboesch propellers from Cornwall model boats - and I am in Australia. It would be very interesting if there was a video made at the start of this post. How many Watts of power is that motor producing. That is the question I would have asked at the time.
Thanks Dave, In common car language that is a V12 in a Ford Fiesta, with the Fiesta drive train.
In some ways I believe the brushless motor manufacturers/sellers are responsible for the confusion. Mostly we see the kV, physical size and the number of Lipo cells required. You need to dig deeper to find out the Watts. The kV basically gives the RPM only. No mention of amps and power. We don't buy cars and motorcycles based on the engine RPM do we?
Typically if you look at the reputed Graupner Speed Brushless range, they have low kV specs, but the differences between a 400kV 7.4V, 400kV BB 11.1V and a 400kV ECO 14.8V are 130W, 1100W and 2010W respectively. A huge difference. When viewing the on-line retail sites, including Graupner, they all look the same (maybe the same photo), but they are all very different motors. Without the rated amps and Watts (not published) the buyer is left unclear as to what they should buy. Brushed motors are more clearly defined.
I must thank Doug for helping me out with Graupner brushless specs when I required assistance.
Mon plaisir Haig, that's what we're all here for - ain' it? 😉 Happy sailing, Doug 😎 BTW: that's one thing I really like about the German suppliers, most of them give much more info in their on-line specs. Funny; for years at work here I used to moan that our marketing dept. worried more about dB's and microvolts than about what the customer could actually do with the bl..dy box! 🤔 I used to rewrite the system specs My Way (thanks Frank!!😉) so the Admiral knew why he was spending his hard fought for budget!
Young at heart - slightly older in other places 😉 cheers Doug
Graham, I have attached the same table that Doug sent me. This has the relevant information you seek.
According to the table attached the Graupner 500 kV ECO has a specified output of 1440 watts and 80Amps. Strangely the 400 kV ECO has a specified output of 2010 Watts. So the 1440Watt output is questionable and may be a typo based on the other entries in the table. more likely to be 2440Watts
In any case you need a 5mm diameter propeller shaft.
For shaft alignment i use a brass tube that slides snugly on the propeller shaft and then on the motor shaft. When the tube rotates/slides well on both then the shafts are aligned. I then fit the motor mounts, check and tweak the alignment if necessary, remove the tube and replace with a universal coupling. If the motor or propeller shafts are a different diameter then I insert the relevant size smaller tube inside the larger of the tubes. This method is simple and has served me well, including for larger IC engine powered boats belonging to friends.
Hi I found this PDF on Graupner motors. Also the Hobbyking site shows the specs on a large number of their brushless motors. I am looking at replacements for two Graupner speed 600 7.2 volts for a mate. I found a D3530/8 1700kv on Banggood with the same 5mm shaft and more grunt, less weight(74 grams against 192 grams)and about a third the price!!! I am going to install one in a Sea Commander(34") with a smaller 2 blade 32mm CNC prop on 3S Lipo 3300mah to test it out. Canabus
Hi Graham and Haig The max current is the Max Watts divided by the Battery Voltage. Most motors reach their max efficiency at much lower value, typically about 77%.
You need to take care when interpreting the data especially when the description has been translated from a foreign language. The Eco range of motors were developed for model boats and in general were high tork, low revving and low current. They were also designed to work at lower voltages so that would explain the lower Wattage. I would only use the nominal voltage, Kv and max Watts figures. The amps appears to be the stall current but I am guessing. Also we don't know the voltage at which the stall current was measured.
Providing you don't exceed the rated voltage and wattage your motor should be OK. I suspect running much above half the rated wattage may require some water cooling.
There are many Wattmeters available that will measure the wattage, amps etc at reasonable prices and if you connect in line with your battery and ESC whilst holding the model in the water you will have a good indication of the max current / watts at full bore. This should be ideally about half the max rating (watts & amps) for both the motor and ESC. https://www.componentshop.co.uk/150a-watt-meter-and-power-an... Reducing the prop size will reduce the load.
Hi Canabus, I think that's the same pdf I found👍 Snag is - you can't upload pdf's here🤔 You have to do what I did; Snip-It into jpeg pics and upload them.
BTW: attached are the dimension drawings to go with the spec. table. Graham: table shows that the ECOs all have 6mm output shafts!
RE apparent discrepancy between powers of the 400 and 600; same applies to the 200 and 300 so I don't think they are typos! I assumed it has something to do with the construction/magnets (type and strength) or even timing? Hope this helps untangle things a little😉 Happy Non-brushing all, cheers Doug😎 PS Dave: it is normal engineering practice to publish data measured at the quoted Nominal supply voltage - unless otherwise specified with the respective data.
Attached Files - Click To View Large
Young at heart - slightly older in other places 😉 cheers Doug
Thank's RNinMunich, Dave M, canabus, reilly4. for the information you have added in your post's. That will be very helpful for me with a couple of boats I am hoping to get set up in the future with brushless motors. An Aeorokits Sea Commander, Sea Queen and an MFA Spearfish.
"The max current is the Max Watts divided by the Battery Voltage."
Hmmm! Dave, I=P/V works fine for DC and static resistances but it gets much more complex in a dynamic system like an AC motor, which is all a Brushless is. Don't want to get into rms and power factor and co here so I agree the wattmeter is the way to go to find out what's really happening. Normally (at least here, not so sure with China!!) the max power output is quoted at nominal voltage and max efficiency. If you (can!) trace the motors back to the original manufacturer they publish performance graphs showing efficiency, power vs current and volts. But who does that? Except nuts like me😉 According to the DC formula the ECO 600 would draw 131A at 11 Volts or 97A at nominal 14.8V. The real 'Black art' is then to work out what power you want/need for how much thrust, acceleration and top speed for a given boat and hull type🤔 Best way is to ask those who've 'Been there, done that'. That's why I appreciated very much Canabus' advice when I was looking for a brushless for my Sea Scout upgrade👍 Happy sailing all - Whatever pushes your boat! Doug
Young at heart - slightly older in other places 😉 cheers Doug
Thanks Dave, Eventually we will have put together a body of knowledge that model boat builders can use with some certainty. At present the information is sketchy, hard to find and sometimes ambiguous.
The motor designers and manufacturers have not been very helpful.
For my La Combattante iii missile boat I used two Hobbyking Keda 720kV motors rated at 215 Watts and 19.3amps max. They were the first brushless motors I tried. I was not sure how many amps they would draw, so I connected an ammeter and fitted my video camera so it read the amps whilst operating. At full speed they used only 8 amps each. Each of the batteries is from 12V made from 9 x NiMH 9Ah D Cells. I easily get over an hour run time at good speed. The boat is 1605mm long so not small. This information may help someone.
Personally I wouldn't say you were nut's. It's people like me that are probably the nutty ones. Without your help some of us would be left in the dark with some of these small motor's. I do not understand how to work out the electrics. So your help that you give is a great thing for numpties like me. To buy a IC engine and stick in a boat was an easy task. But Brushless i'm lost. So many places have banned IC's we have to now rethink. Keep you help coming PLEASE.
sorry to bore everyone with repeated info, as a similar question was posed recently. I agree with the fact that shaft is too thin, it very much looks llike a fibreglass very light racing boat set up, now this doesnt mean you cant go fast with your boat, but you need components that are up to lugging a big heavy lump of wood around the pond, not a lightweight feather😊
I have 5mm shafts, less whipping. and I have oilers so they are lubricated with oil rather than grease, just my preference. You can get these shafts from shg marine, they will supply with push in aceteal (probably spelt wrong!) water lubricated bearings, real cheap, so you can change then every season if you want. The shaft has to be supported, where it exits the hull, just put it through another piece of ply, and fill the void with epoxy, and double up the former thingy it goes through in the same way. (pic) The prop you used is the wrong blade type, thats probaly why it fell apart, plus the soldered on blades are a weak design for higher speed, simon higging is one piece, but at this stage, still testing, you can get plastic "x" blade ("s" blade are less speed)_ props again from shg marine for a few quid each, then you can test a few different sizes. If you jump in for an expensive brass one, and its wrong, its wasted money. As a starting point, 35mm, 40mm and 45mm, if you dont have any way of testing with data logging etc, you are doing short runs, with the smallest first, and seeing if the motor gets hot etc, and what sort of speed you are doing. My brushless motors are generally 800 to 900kv, and achieve 25mph in four foot heavy hulls, you want lower kv for torque, not high kv high rev motors. I got into thsi 10 years ago, thwere was NO advice around then as it was new tech in boats so I learnt the hard way😭 When (if) you go to a brass prop, the "cleaver" blade design (pic) works well, I did extensive testing with my Huntsman and fireboat and was lucky enough to have Simon Higgins testing props with me on my boats, again because what I was doing, large scale boats, but going very fast, was unique, and the cleaver design was the best at the time. Forget the fear of lipo, and brushless, they go as slow as your throttle stick is pushed, 👍
Great bit of information , Many thanks pmdevlin. I have only ever used 5mm shaft's and gone out with a variation of small to medium nylon prop's and played on the pond bank with them until I got one suitable. Then I would go for a cast alloy or bronze to that size. But this has been on IC engines, up until about 3 years ago. I have used the same way on brushless since. I have seen others using thinner 4 mm shafts and having problems. I have also always used a prop shaft support under the boat and if I have any type of gap between the coupling and where the shaft goes through the hull I would always add a wedge of wood epoxied in. Once again no backlash on the shaft to make it come loose. The only time I have damaged shafts has been through sheer stupidity racing round a pond with others and misjudging the distance and the bank jumps out and collides with the boat. Whoops broadsides with a nice hard concrete bank and, Yep new shaft needed. But as you say the throttle stick will take you from as slow as you want to flat out. Except when it's IC slow isn't always possible if you do not have a clutch fitted.
Hi Doug Brushless motors may be similar to AC motors in construction but they are powered by pulsed sequential DC so there is no AC involved.
I do agree Watt metres are the best way to make sure the motor, battery and ESC max values are never exceeded.
I agree the spec sheets are very useful but are specific to the type of motor and original supplier, and many are for companies no longer trading.
I do sometimes have difficulty in interpreting some of the info supplied but the nominal working voltage, max power are usually OK. The stall current is useful to decide on the wire and fuse size as well as choosing a suitable ESC.
At the end of the day if the set up is getting too hot you are probably working over the specs and if water cooling doesn't help you need to adjust the prop and / or battery voltage.
you could use a dremel and grind some away. I have used the brute force and Tapped the shaft inwards if a few taps aren't enough then a couple of harder whacks should do the trick to loosen it. then pull it out from under the boat. It has always worked for me.
Hi Graham I usually use the dremel to remove as much of the epoxy around the shaft, then get a big lump hammer and hit the end of the shaft to break the seal. Depending on how well you fitted the shaft it normally comes loose after a couple of taps and can then be tapped out from inside.
regarding the rudder, I use standard profile rudders, and cut them this way. The rudders are like brakes, and I was having issues on fast gradual turns the bow was coming down, almost digging in. Thinking it was weight displacement I spent ages messing around, until a friend suggested cutting down the front edge, gradually, and seeing how it went, this cured the problem, turns are nice and flat
I was also told about cutting away the front edge for the same reason, digging in on turn's. I have found on hulls like the Vosper RAF Crash Tenders and MTB hulls they sit on the water on a turn as if they are stuck on the water no roll at all. Also on the Huntsman style hull they also turn a lot better with minimal roll. It was told to me on her the other day that the rudders were meant to be the way they are and there was no need to cut away the leading edge. I have done this for many years now, since the mid 70's and had great results I even put a 10cc engine in a hull rated for 5 to 7.5cc and it was an amazing boat to run. I turned a couple of boats upside down until the rudders were trimmed and then good to turn. I'm glad I have found someone that thinks it's alright to do. 👍😊
Hi all, what do we all think of the Graupner 500 ECO? it only does 7500 rpm but high torque, about 1500 watts, 14.8 volts. The say it is especially built for boats. I would like to know your thoughts on the small outrunner motor? Regards Graham
Hi Graham, There have probably not been any answers so far because we are most possibly speechless. If you go back and read through the comments above you will see that most of the problem has been the large overpowering of your boat (1690 Watts - according to info provided by DaveM), coupled with an inadequate drive train. So with all this knowledge available you have asked our opinion of the Graupner 500ECO - one of the largest motors in that range. This is quoted at 1440 Watts. This may not rip the drive train out as quickly as the other motor did but has enough torque to do so. In my opinion I think you could try a motor producing under 500 Watts and see how that goes - with a 5mm shaft.
Hi Graham If we are talking about the Graupner Brushless Speed 500 ECO no 7295 https://www.graupner.de/Brushless-Speed-500-ECO/7295/ then yes the Kv is 500 which equates to 7500 at 14.8v. It's 50mm x 80mm with a 6mm shaft so really a heavy duty motor and in a Aeronaut Queen 36" still much too big and powerful. You really need to resolve the drive train and shaft problems and this will be easier if you choose a motor of smaller diameter and power. A 36xx or very similar size motor at about 1000Kv or less (500Kv with 14.7v) will be ample. The prop should be less diameter than the motor. There are many examples of 36" model boats on this site and I do believe the majority of our members have used similar set ups, to those we have suggested, in their models with a large degree of success. It could be we are talking about a different motor as you refer to " the small outrunner motor". If so please post a link to a pic of the motor.
Hi, i have searched for a 500 watt 500kv motor and just can't find any, what company do you use for motors? at last i think i found a suitable Motor, i hope, it's a keda 36-42m 500 watt 950 kv, with a 5mm shaft and fits my new 5mm to 5mm coupling, so don't need any other parts for the power train! will need to change the hole to hole distance to fit the 16mm spacing of the new motor.Then gluing the new 5mm Shaft in, i think thats a good setup. The new 500 watt motor should have a long running time i guess on 10000 mah Lipo's? Anyway thanks again for helping me, very much appreciated! Graham
I think you've missed the point. Everyone has said you need less wattage . Ie under 500 watts and you've picked one at 500.Something about 440/50 watts tops is what you need.Even 350 would move your boat at a more scale speed with the right prop and a 5mm shaft. Have a look on Mantua models site ,Also Marine Model Supplies ,and Sussex Models. Oh yes also Wheelspin Models. If no luck ask Uncle Google.
That sound better with a 5 mm shaft. But still be sure to support the shaft under the boat and if possible also under the shaft inside the boat. This way you shouldn't have any trouble with vibration though the shaft to loosen it.
Graham That sounds much better and will move your boat at a very fast speed. I must reiterate my previous advice repeated by BOATSHED regarding the extra support for the prop shaft at each end and adjacent to the bearing. Unlike brushed motors, brushless accelerate to their KV rating at a very fast rate and if your installation is not solid (as concrete) you will experience all kinds of problems, all costly, and often terminal (personal experience confirms this). Finally do get a wattmeter and check the amps and wattage whist holding the boat in the water. If either are above the rating for the motor, ESC or battery you need to reduce the prop size. I can't emphasize this enough as the consequence can be an explosion on the water and total loss of the boat and all its equipment. Asw you have mentioned 10000 mA I assume you will be using two 5000Ma batteries in parallel. This is OK providing you use and electronic coupler between the batteries to disconnect a discharged battery to ensure no one battery discharges below the recommended value. These are not cheap and personally I would use one battery and change to a new battery when the first was depleted. I accept that if you are in a racing situation this may not be possible, but I suspect as a newbie you are using for pleasure purposes. I hope you will now be able to proceed to install the new motor and prop shaft and supports as suggested. Please keep us posted and I look forward to seeing your model on the water
hi Dave M, well that was good info on the Lipo's i was going to put them in Parallel But certainly won't now! i will use one and then swap over when necessary as you suggest,Thanks! As far as the 500 watt motor is concerned, i have not purchased it as yet but as a previous post stated that i need a smaller wattage than 500 , i will carry on looking for a smaller wattage and low KV size motor, although all i seem to find are are very powerful ones! even on the web sites named in the post but i will phone them in the morning and ask.
the Boat does have a keelson, a piece of angled wood below the hull and also one inside the boat and this shows about 1 1/2" of tube either end of the shaft to fit the supports. Thanks graham
With respect Graham, A 'Keelson' is always inside the boat / ship. It is a reinforcing beam laid across the top of the keel. Nothing outside the hull. Good luck with your fitting out and much fun sailing, Cheers Doug😎
Young at heart - slightly older in other places 😉 cheers Doug
I think you might need pointing in a direction, so I had a quick look on Hobbyking, and this motor is the sort of thing you can use, although this particular one would need you to swop the shaft around, this is just a guide, other s will no doubt add comment, its the right size, 5mm shaft, right kv and watts.
you don't need the high amp capability, but its reversing, programmable, water cooled, and has an sbec, so the main battery power this
5 mm shaft, move your motor to the centre section meaning weight distribution is more central, and you can now use a shorter shaft, and get a couple off plastic "x" props, I would say 40 to 45mm will be the one. This will give a good speed, and you can power on 3 cells or 4 cells lipo, get higher c rating (40c or more) and higher mah so you have fuel in the tank available
This is just a guide, a starting point, as I feel you are unsure where to start, others with more knowledge will come in regarding this, having experience with lipo, brushless, 3 foot ply boats, and esc's, depending on budget, this would be the sort of thing I would be getting.
Hi Graham You do have to support the prop shaft close to the bearings at each end. This is vital if you are to avoid a slight imbalance developing into an uncontrolled whipping and as you have experienced, damage to the shaft assembly. The support needs to be firmly attached to the hull and shaft close to the bearing to provide both vertical and horizontal support. The supports should ideally be within 1/8" of the bearings. If you are reinstalling the prop shaft then, as others have suggested, it may be an opportunity to move the motor towards the stern and use a shorter shaft, but still providing support near the bearings.