Rewinding the Turnigy Rotomax 150cc BLDC to lower kV

[@garypaisley]

Many Thanks! Top tip - A few drops of acetone on the motor base screws will dissolve the cyano glue locking them in place, avoiding the oven step which could harm the magnets.

[@AcrodesignerLNSNI]

I know. Found out after some time. Also tipping a soldering iron just on the tip of the screw will loosen the CA

[@aserta]

Just a tip, if you stick your armature on a thinner rod (than the axle) which is affixed horizontally to something, then find the end of the wire, loop it over something above the position of the armature and then simply throw the end with something heavy over your balcony, you'll unspool the thing faster than you think. Plus, you get to keep the wire for other things. Works up to one mm wire, after that, it simply doesn't bend anymore and you have to pull it.

[@wagnerpereira8311]

É muito bom

[@Gunzee]

My father told me the UK used to have many rewinding and battery repair shops when he came over, mid 60s. He got his beetle dyno & Datsun 120y rebuilt, the last shop I knew off run by a very tall Irish guy closed about 2003/05. Great work btw, looks very fiddly

[@Marie579]

WOW, that’s impressive I really wouldn’t know where to start apart stripping it, this is where matches comes handy I guess, impressive video.

[@AcrodesignerLNSNI]

Thanks :-)

[@bl00ster]

Very impressive.I don't understand the details and would never try this myself but I hope such devices will be available commercially.This could revolutionize HG as we know it.Thank you for doing this Reidar.Please don't stop, your work is showing the way for many people.

[@AcrodesignerLNSNI]

Well, phg will probably never revolution to the sports. Its expencive and demanding ground handling. However, for the dedicated pilots it is the true and real motorglider for hanggliding. No theory, my flying time last 3 years have been increasing a lot due to electric assisted thermal hunting

[@dongguanfreerchobbyco.limi3655]

any demand for powerful bldc motors, our company can provide more choice and customized service service for you

[@sempertard]

"I don't understand the details...." He electrically/magnetically "geared it down". And did a bang-up job doing it.

[@dulal1267]

@@AcrodesignerLNSNI hi

[@electronicshelpcare]

reat!!, what i was looking for and excellently explained for people like me, newbie in the electronics

[@AcrodesignerLNSNI]

Thanks :-)

[@alishanmao]

what an awesome job done here. Lots of work but good results.

[@3deeguy]

Rewinding for paramotor. This is the channel I'm looking for. Subscribed.

[@AcrodesignerLNSNI]

I have built an E-Help for paraglider with this motor and setup.

[@cripplekid0902]

Thank you for having real music, a lot of the other KZbiners use really annoying music.

[@Migueldeservantes]

Love that tune! Also the cat-Scan was very positive... any video that have a cat make things really great!!

[@Bigwingrider1800]

HERB ALBERT. MY MOM LISTEN TO THIS..BRING BACK MEMORIES

[@DoRC]

You sir have both balls and skills....

[@ahmdabdallah5811]

What Is Islam? Islam is not just another religion. It is the same message preached by Moses, Jesus and Abraham. Islam literally means ‘submission to God’ and it teaches us to have a direct relationship with God. It reminds us that since God created us, no one should be worshipped except God alone. It also teaches that God is nothing like a human being or like anything that we can imagine. The concept of God is summarized in the Quran as: { “Say, He is God, the One. God, the Absolute. He does not give birth, nor was He born, and there is nothing like Him.”} (Quran 112:1-4) Becoming a Muslim is not turning your back to Jesus. Rather it’s going back to the original teachings of Jesus and obeying him

[@cvspvr]

@@ahmdabdallah5811 hail satan!

[@3d-speakers945]

caspar valentine agreed

[@aarondarby6778]

Beautiful mate! Loved the music. Also good to see you gave this thing a cat scan before running it up ;-)

[@henryphillips4683]

HA HA!!

[@SERGEY-KACHAN]

kzbin.info/www/bejne/Z4bZZZeVjNCehcU

[@ehcnjq]

BEST MUSIC EVER!!! not this annoying what-ever power sounds ... BRAVO!

[@kwhp1507]

I am not interested in HG at all but I am into RC. I love the video, it's a great semi-instructional video. I can see me referencing this in the near future just because I have some smaller brushless motors that have to be rewound due to burning out. Thx. I am now subscribing

[@AcrodesignerLNSNI]

Just a comment from author dated august 2017: since the video was made I have increased the number of strands to 12 for the motors intended for flatland start and use of the Menz 34x14 prop. The space in the stator for 12 strands is pretty marginal so it requires skills to compress all that copper. However, then You have probably the most optimal hangglider electric motor on the planet. Relatively small and lightweight compared to the bigger disc motors. And will at 52 volts and 140 amps spin a Menz 34x14 prop producing thrust enough for flatland launch of a 80 kg pilot on a 155 sq feet glider.

[@davegeorge7094]

This what I like to see men do! Cool DIY bro

[@adysdelicias1465]

Do you sell those motors

[@dominikknapik7990]

Correct me if I'm wrong but that's about 40 percent better efficiency?

[@vidmasze]

​@@dominikknapik7990 i think mostly about larger prop at slower rpm to increase propeller efficiency (with help of lower kv to keep Volts higher enough and for Amps to be low enough within consumer ESC range). Maybe there's something how to increase motor electric efficiency at lower rpm too, but dunno, would be interesting to hear (maybe: star vs delta winding?)

[@macsheadroom3209]

I admire his confidence, and the tune makes it look easy...

[@carrcohol]

As a rule, what about the old winding are you attempting to improve? The wire diameter? The turn ratio? What's your sliding scale so to speak, as in "fewer turns, thicker wire=more torque but higher current? If I want more torque, what do I lose as far as P.I.E.R. Great instructional, I am impressed.

[@AcrodesignerLNSNI]

Lower KV

[@danb37]

Thank you for posting and not just because it’s Thanksgiving Day. Happy thanksgiving btw. Thank you for posting this inspirational video and extremely informative. So much very good information in the comments!

[@oliver2032]

What are you using to control the speed control?i see something on your harness but not sure what it is or where to get one. Thanks for your time spent helping everyone!

[@AcrodesignerLNSNI]

This days use a wireless from RC cars suystem

[@createthisdotcom]

holy crap this is a ridiculous amount of work

[@AcrodesignerLNSNI]

Hobby Fun :-)

[@SnowWolfJones]

im misunderstanding something from the description, are you using LESS turns per spool on the stator or MORE ? And this allows lower rpm but more torque to drive bigger propellers with more efficiency?

[@AcrodesignerLNSNI]

More turns. The original 150KV has 3 turns per pole. Mine has 5 turns

[@SurfKiteFly]

Hi thanks for sharing your project. I have just purchased a turnigy 150cc equivalent motor and 32 inch prop. I don't intend to rewire it but I do have a question for you if you would be so kind as to answer. Do you think the standard bearing system is safe from the factory. I was considering running the motor inline with secondary high speed bearings in bearing retainers inches of the factory system failing. Would rather not have the extra weight. Just wondering what your thoughts are on the standard factory system. Thanks Darren

[@AcrodesignerLNSNI]

Running a bunch of this motors since 2013 we never have had problems with bearings anytime. Even rough dissasemby and tinkering, propeller strikes and mishandling. My thinking is that as designed for RC model airplane usage, were small crashes, landing mishaps and nose overs are not uncommon, the motor is built quite robust. On my geared version I even put a belt driven sprocket gear direct on it with all the side forces that represented. Ran flawless for many years. I don't think You should be worried about those bearings

[@SurfKiteFly]

@@AcrodesignerLNSNI thanks so much for your reply. Just waiting on a bec and I will be ready to wire it all up. Already built a mini ppg carbon-kevlar frame and installed the motor, esc and made fire proof battery bags. Excited to get it working.

[@peterpeterson4272]

I bow to your genius. Thank you for the great video :)

[@davidaharris2561]

That's the Cutest Cat Scan I've ever seen.

[@AcrodesignerLNSNI]

Sasha is a very nice workshop mate. He is now 8 years old, an russian Siberian allergic free cat. This Siberian cats does not have the enzyms in their spit and fur that triggers allergic reactions. My son is allergic to normal cats but not this one.

[@davidaharris2561]

Well, Sasha IS the BEST Cat in the world to have...You're family is Very Lucky to have Him.

[@AcrodesignerLNSNI]

Sasha is now 7 years old and becoming more and more cozy. Siberian.

[@MrVoice1]

You have so much free time

[@AcrodesignerLNSNI]

Ha ha. Maybe true. Or not.

[@Capnmax]

Did you build your e-help system? How did this motor work out? Still using it?

[@AcrodesignerLNSNI]

Hello, Yes this motor flew for many many hours. Built many more since. Alsoother KV's

[@victoryfirst2878]

How long did this rewind take you Reidar ??? I like this method of rwinding with all your steps. Job well done fella.

[@agussungailiat2996]

Wah kalau untuk dijadikan pesawat terbang kira kira bisa di naikin gak ya Salam sukses selalu Bos ku....

[@George25]

What size are those little hex screws , I want to change the neck support for the propellers and I need to open the part you just placed on your bench ,I appreciate your answer mate 👍

[@thefredFreddy]

très beau travail. vous avez eu de l'aide sympathique sur ce projet ;-))

[@Surferant666]

Great video thanks. Are not two bladed props more efficient than 3 blades.

[@AcrodesignerLNSNI]

Yes, two blade is more efficient mostly due to the better aspect ratio. However, in case supersonic tip speeds are an issue then a 3 blade can be the solution going with a smaller diameter thus smaller tip speeds. Could also be that more blade area is desireable then a 3 blade

[@Surferant666]

Reidar Berntsen paddle blades...

[@AcrodesignerLNSNI]

@@Surferant666 Paddle blades have low aspect ratio and high induced drag

[@Surferant666]

@@AcrodesignerLNSNI where did i mention paddles?

[@marcinjuraszek]

Hi, very qool video, can you explain - how is possible to increaser kV with this same voltage ? more wire / more turns ?

[@eaausang]

Where did you get the 3 bladed foldable prop?

[@AcrodesignerLNSNI]

Rasa

[@ThePdidy10]

Hello, I am curious what ESC, Flight Controller, and props you would use for those motors? Batteries as well please? I am looking to build something with 4-6 of these motors to lift myself off the ground. Also great work on the video, the synchronizing of props was very impressive.

[@AcrodesignerLNSNI]

The ESC is the Turnigy Dlux 250, prop is the Menz 34x14. Copper wiring we use 12 srrands of 0,6mm2 this days to get higher copper filling. For flatland start the E-Help is at 35 kg thust at 52 amperes (14s) and 122 amperes. Actuator is a RC control for cars

[@muntee33]

Reidar Berntsen 14S? You achieve this by LiIon, custom LiPo or what configuration of OTS batteries?

[@vintageseller7700]

@@muntee33 off the shelf 14s lipos

[@leviterande7902]

@@AcrodesignerLNSNI Dear Reidar, Im in Sweden! you have such an amazing configuration in your video. Could you please enlighten me on your last specification at 08:40 : You wrote 6kw, 2.5Amp /kg. Which means: 6000watts / 52volts = 115Amps which means: 115amps/2.5amps = 46kg of thrust!!!!! is this real? you mean you got 46kg from 6kw? could you please clarify Reidar if you achieved 46kg, or what exactly kind of thrust did you achieve with 64kv. Thank you so much!

[@ericylle6597]

@@AcrodesignerLNSNI wow! 6,3kw for a massive 35kg of thrust! MOST impressive! Was that in delta or in star?

[@SagaSeaCraft]

Great cat! We have seven of 'em.... three of which are of immense help in my shop! At least they think so. :)

[@AcrodesignerLNSNI]

+SagaSeaCraft Lots of cat hairs in Your house ?

[@ericylle6597]

HI! congrats and easily the most interesting brushless mod on youtube. You wrote 6kw at 2.5Amp p er kg. I assume its 50v so that means you got 48kg of thrust with the 64kv mod! that is an insane thrust efficiency. would you please say if that is correct? thank you!

[@robertlhote7412]

Magnifique. .travail fait avec grand soin...👍

[@macsheadroom3209]

I don't even know what you said but I know it means awesome...

[@chukchee]

What is the website for the winding diagram calculator? Thanks.

[@AcrodesignerLNSNI]

www.bavaria-direct.co.za/scheme/calculator/

[@rabinpetrobras]

Reidar my friend !!!! Congratulations for this chanel !!!!! Very Good !!!!

[@AcrodesignerLNSNI]

Thankyou Rabi in Brazil :-)

[@y788lhjk1]

2:15 This is the moment when mom decides to come in without knocking.

[@jbbauer0]

At least your pants are on

[@y788lhjk1]

Yeah not the absolute worst occasion

[@AcrodesignerLNSNI]

Ha ha... -could easily be worse stuff on the screen :-)

[@anupr3592]

What is that stator made of. And if i want to build myself a stator what should I prefer

[@yordanvelikov9208]

Can it be used as electric generator? Do you know what it generates if turned mechanically with 65rpm? This is a golden mine if works!

[@AcrodesignerLNSNI]

Yordan Velikov 65 rpm is too slow to produce any useful kilowatts. 4000 then 7 kw about

[@henke2]

Funny unit amp/kg thrust. 34x12 has way less pitch and less rpm, way less efflux. I assume you will be moving at a speed regardless of what this motor is used for so efflux makes a great part of it too.

[@EVO_Engineering]

Holy snail! Awesome! Congrats!

[@PhG1961]

Awesome video, also the music is way better than the stupid/crazy free audio junk from youtube. Great job !

[@paulmartin8051]

Its dead simple. If you have a propeller say a 32 " diameter one for example, and say you have a 130Kv motor and your run it at 70V to get maximum power then the blade will spin at 9100 rpm. That means that the tips are totally supersonic and it's really inefficient. So to bring it to just below Mach 1 you have to run it at 60V which means that the motor is running at about 60/70 or 86% of its peak power. In fact its still quite inefficient and if you said that you wanted the tip speed to not exceed M0.7 to avoid compressibility losses you would have to run it at about 5600 rpm so you are now down to 61% of max power i.e 43 V. If instead you decided to use an 80kV motor then at 70V its running at 5600 rpm so its the sweet point. As Power = Torque x Omega where Omega is the rotational speed. So in the low Kv case you are running max power and in the 130kv you are running 61% of max power. For the same rpm the lower kv gives you a much higher torque. It's not about electrical theory and winding etc it's about matching your motor speed as close as possible to the rotational speed you need to operate whatever you are driving for it to be at its design point. If you geared the higher kv motor so it drove the propeller at the speed you wanted then there would be no difference.

[@AcrodesignerLNSNI]

Excactly.

[@naz95k71]

OMG i would love to have this motor on my electric longboard, imagine the speed it could go and how steep hils it could climb, i bet it could go up a skatepark halfpipe :D

[@AcrodesignerLNSNI]

Naz95K Ha ha. On a longboard instead of D config go Y (star) and it goeas from 105KV and 4800 rpm to 80KV and some 3300 rpm. Probably go direktly on the longboard wheel. 7 kW or almost 10 horsepower on a longboard brobably would be a blast 😂😂😂

[@naz95k71]

@@AcrodesignerLNSNI yeah too bad its expensive to make or buy such highend stuff, having that much torque would be cool, you know before i bought proper motors and belts etc i atached 4 drone propelors to it just to go faster downhill. Scary to ride on but so much fun

[@somaodeunier7586]

Great work and video! Small question. How did you determine the length of the wire and how many times you loop it (5m x 8 loops in your case) as well as the wire AWG? Im working on a 3 phase motor completely from scratch and would like to know if you have formulas to answer my questions or did you figure it out from the original windings?

[@AcrodesignerLNSNI]

I had no formula. Just did by cut&try. The 105KV motors that dominate the E-Help world this days are 12 strands of 0,6mm2. Nice to work with flexible and good copper filling. Just did a 88KV version with 6 turns with 10 strands of 0,6 mm2 wire. Run tests on a series of pitch parameters on 34 inch diameter props. Obvious is way below tip speed transonic issues. Efficency increase. However, top thrust is below flatland start. Looks like we have got the supercruiser, KV88, battery 52 volts, prop 34x16 inch

[@marcinjuraszek]

@@AcrodesignerLNSNI hi, great video. Who can give me advice to speed up motor, need less turn wires on stato, but bigger wires?

[@LukeQuin]

Great Video. How many hours did it take to re wind one motor? I have a rotomax 50cc and would like to lower the KV. Probably wont do it after seeing how much work it took for you to do :)

[@AcrodesignerLNSNI]

Luke Q Total 10 hours if pro and have got all parts available.

[@bireckable]

in the original config. of the motor what re the caliber of the wire and hhow many turns have? because i want to do this motor with the original configuration but i need to know this spec, so please if you can tell me i would appreciate

[@AcrodesignerLNSNI]

The original 150 KV motor the stator has 3 turns around each of the 24 poles and connection is Delta. As seen when disasemble. The cross section of the stator winding seems to be in the area 5 mm2 on the original motor. Be aware that Hobbyking refer to this motor as something else than "3 turn" windings because they count the pole pairs and add up the windings that belongs together so I think in their world they call it "8 turn".

[@tcoblackflagwhitearmy4615]

hi there im using a 600w brushless motor hub, running with 52v 26a batt . what must i do to make it faster, less hotter and batt consumtion reduced or maintained.. currently it can withstand 5-6 hrs ride at average of 25-30km/h with intermitent trotteling

[@AcrodesignerLNSNI]

Well. To take out more power it produce higher losses, about 2-3% of the output power go to heat. High rpm produce higher iron losses but also better cooling

[@Flyit37075]

I bet you make a mean guitar pick up.. lol but seriously thanks for posting all your e help. I think you are awakening the HG world to new and better ways to expand the sport.

[@davidberglund909]

Great work! What is the maximum thrust you can get out of the folding 3 blade prop?

[@AcrodesignerLNSNI]

My rasa 34x12 three blade foldable is about 28 kg and I only use it for motorgliding form hillstart. Not for flatland start that requires about 34 kg thrust to do it safely with my 85 kg pilot weight

[@temDeTudoOuQuase]

Great video, very interesting and informative. Good job.

[@smorrismlbco]

I was faced with similar problems on my electric hang glider project but instead of rewinding the motor (I lack the skill!) I decided to use 2 motors running at reduced power instead. I run the stock Turnigy 150 motor with Xoar 30x12 props and climb at 5-7KW per motor (51.8V, 100A per motor.) Because there are 2 prop discs the prop efficiency remains high. The only downside is the weight and cost of 2 motors and controllers instead of one.

[@AcrodesignerLNSNI]

Yes, the reduced disc loading from two slow props will give good efficiency. How is the two motors arranged, trike ?

[@AcrodesignerLNSNI]

I saw your electric powered Millenium video. Very impressive !

[@saeedmughal6756]

Reidar Berntsenkkil1pqplq

[@AcrodesignerLNSNI]

If You look at another video on my channel showing the twin engined "Fugly" You can see two of this rewound motors with 34x12 props driving my big tandem glider with big wheels and tailwheel. Almost like a small ultralight. It was an experiment to try to obtain the lowest possible disc loading prop efficiency and see what performance that came out of that. It showed pretty good efficiency for the drive train. Two motors each pulling 70 amperes and producing 22 kg thrust each driven by one common ESC (Turnigy Dlux 250A) worked pretty well. It was a fun aircraft to fool around with at the airfield. However, the air resistance when gliding engine off was awful. It glided like a manholde cover and I soon named it after my instructors dog "Fugly". Which means fucking ugly. My goal is not to make an electrical ultralight, it is to use electrical to reach thermals and then soar away engine off.

[@ishengelia1]

Hello Reidar, do you think the tmotor prop G40x13.1 could be good match for this motor. rewound or not? thank you

[@MaxWox]

Не пойму, в оригинале мотор был мощнее? Или он свой подписал как оригинальный?

[@falcomp1269]

Hi Reidar, is the 2,5 amp/kg thrust calculated or measured? Just because I have seen another video from you there was 3,5 amp/kg thrust with a geared prop. Can be the 34x12 prop better than the bigger diameter geared one? Regards, Roland

[@AcrodesignerLNSNI]

Measured. But efficiency is not linear. At low loads like 10 kg thrust the efficiency can be good at 2,5 A/kg. Increasing the rpm and thrust the maximum disc loading kicks in and efficiency drops off to 3,5 A/kg. Asking a small 24 inch diameter prop to produce 26 kg thrust then efficiency is 6,8 A/kg. Mossie at 52 inch diameter prop produce same thrust at less than half the amperes. All props have their limits how much thrust they can produce - disc loading and blade loading, aspect ratio on blades must be considered

[@falcomp1269]

Hi, thanks for the explanation. So it can happen that for example an 36x10 prop on lower thrust (maybe 20 kg or so) is acceptable efficient and is no necessary a bigger (50-52 inch) prop? I'm asking because I'm building now an "thrust assist" unit for paraglider. First I only want to start from hill and have 0 vario with the motor on. I made a folding prop with 51 inch diameter wich seems to be ok but I find it a bit heavy (not flying yet first test is coming soon). It is worth to make some test with smaller props ( I have 30x12, 32,5x11 and 36x10 here) on low loads (15-20 kg)?

[@AcrodesignerLNSNI]

+Roland Falusi Yes, for only 20 kg thrust a 34 inch prop will be efficent in the 2,5 - 3 amp/Kg range at 50 volts

[@AcrodesignerLNSNI]

+Roland Falusi Yes, for only 20 kg thrust a 34 inch prop will be efficent in the 2,5 - 3 amp/Kg range at 50 volts

[@ericylle6597]

@@AcrodesignerLNSNI Aha now I see! Im reading your old comments here:) so 2.5A applies not up to 6kw but at low disc loading. good! but still 180w/kg--6,3kw, i.e 122A at 52V at 35kg thrust for 34x14 propeller is the most efficient propeller system I have every seen in my entire life and I am a home DIYer. on eCalc it says the thrust is much lower

[@tushar673353]

i also like to work with cats...nice video

[@mreese8764]

I like this, but would it not be easier to add some transistors in parallel to the existing ones of the h-bridge, swap the transistors to bigger ones, or take out the transistors and add a substitute h-bridge board to the ESC? At least if the batteries can supply the current, that should be easier.

[@paulmartin8051]

what method do you use to lock the propeller so it doesnt windmill when the power is off in flight?

[@devilsoffspring5519]

Holy smokes man you're a glutton for punishment! Nice work though! Musta been one heckuva relief when the phases all had the same back EMF and the thing finally ran! I, for one, probably would just 'cheat' and build a gearbox for it instead :)

[@AcrodesignerLNSNI]

I have built many many motors after this and all but one ran nicely. The one that did not run well was because I had shorted a wire against the stator iron sharp corner. Had to redo the whole job. Beer while making the motor was a factor there... :-)

[@devilsoffspring5519]

@@AcrodesignerLNSNI Beer is frequently a significant factor. At least you were dealing with electric motors and not firearms :)

[@jon4x4]

Well, loved the content as well as the music

[@stocklitv1371]

were comes the noise from the brush-less motors?

[@AcrodesignerLNSNI]

From the PWM switching frequency

[@ronvansommeren]

Beware of oven temperature overshoot, may kill the magnets. Best to wait say half an hour or so for temperature to stabilise.

[@AcrodesignerLNSNI]

Today I just blow the old windings with a heat gun for loosening the resing for just the reason U mention

[@GodCoastQLD]

How many turns per feet and diameter should I build a propeller? I have purchased a 150cc and I am just getting a custom made propeller. Thank you and is there more information on your builds?

[@AcrodesignerLNSNI]

Look at my channel. E-Help, how it is made. The 150cc Turnigy Rotormax original motor ?

[@GodCoastQLD]

@@AcrodesignerLNSNI That is correct. Can you please share what diameter and turns per feet should I make the propeller? And what angle?

[@AcrodesignerLNSNI]

@@GodCoastQLD Depend on battery choice. Are You running 12s (2x6s) or 14s (2x7s)? Because that will determin Your rpm and thus also tip speed. At 150KV the rpm will be quite high and You need to calculate the tip speed. Tip speeds above 250 m/s will create excessive losses and huge noise. Our first flights were with the original 150KV motor and efficency was not the best. 168 amperes for 26 kg thrust compared to todays 100 amperes for 32 kg thrust on the 80KV version.

[@GodCoastQLD]

@@AcrodesignerLNSNI I am using 14. What brand is the 80KV is it? I want to get it because the 150 fell through. Also what is the best propeller? You are using a carbon one which folds.. I am a good pilot but the tech side is an area that I want to grow in. Also I have to have a folding smaller propeller as I will thermal once up. Thanks hey

[@matthiasBdot]

seems a lot of effort. did you try the alienpowersystem 12090 brushless motor 50kv?

[@AcrodesignerLNSNI]

Hobby is to make stuff. Not the easiest. But much more fun

[@winfriedrijssenbeek1]

Dear Reidar, the perfect work! Congrats. what is the best eff, for the 34x12 in delta or star? Does the 2.5 amp bring ca 7 kg/kW? with 34x12? Best Winfried! PS we are considering the Rotomax again for commuting craft with wings!

[@AcrodesignerLNSNI]

Hi Win, I this days only use it in Delta. The star coupled HT (High Torque) version of E-Help was sure pretty efficient but the 3300 rpm swinging a 120 cm diameter prop proved a bit unpractical for hangglider. Affected the handling a bit and doesent fit into my Toyota Prius Plugin. The efficiency was good. However, cooling the motor was a bit demanding at that low rpm high torque. Think it was pushing the motor physical dimensioning a bit too far. The HT achieved some amazing low 2,5 amperes at 52 volts to produce 30 kg thrust. But only for limited time as the motor became very hot. Cooling is from rotation working as centrifugal pump. So HT was only for cruisefrom hill launch, not flatland start. Even thoug I once did flatland start with it. Did not like it. Same motor in Delta with some 5000 rpm plus on a Menz 34x14 prop proved way more practical and nice for hangglider. At some 120-130 amps it produce 35 kg thrust for flatland takeoff seen on another R&D video at my channel. That is efficency in the 3,7 amperes per kilo thrust. When throttling back for cruise the efficiency was better as the disc loading decreased. And no cooling problem, can stay on takeoff power all day long it seems with copper size total 7,2mm2 as it was wound of 12 strands 0,6mm2 wire.

[@Nhinguyen-nl3gf]

Rotomax 150cc có gửi về việt nam không

[@SagaSeaCraft]

Excellent! Looks like that was not your first rodeo on rewiring. Questions... is pre-twisting the individual wires really required, or is it for ease of rewinding? Would the motor run at a lower temp and more efficiency without twisting, or does it even matter? Now, are you thinking of rewinding a motor for a direct drive 54" Bolly folding or similar prop? Probably would require a larger stator diameter and more stator teeth for higher torque / lower RPM, right? And....what max temps does the epoxy have to endure, and do you cycle-heat the cured epoxy / stator to increase the Tg (glass transition temp) of the epoxy? Thanks! -Doug

[@AcrodesignerLNSNI]

Twisting the wires makes them essier to work with. No impact on performance

[@AcrodesignerLNSNI]

Later versions to be able to pack more copper I almost do no twist. The 12 strand version the strands are prepared not twisted I just ziptie them prelimanery for easier handling and remove the zipties as the copper go into the motor. With parallell strands the density is better and I have a 7,2mm2 (AWG 9) up and flying now

[@henryphillips4683]

That is fascinating! Are there any motors out there with 12 flat winds on the stator? Has the machine been made with the intricacy it takes to do this yet? We need a commercial motor like this. Thanks to your help I am getting closer to wiring the batteries in the tray for the stock motor basic setup.... I have another question about the four on / off switches at the bottom. Would there be any need (or purpose) for you to have to reach back and turn them off in flight in any type of emergency?

[@louischarland8552]

Hello Reidar, Louis from Montréal, I am at the rewinding stage of my E-help project and I can't figure out the size of AWG wire to roll, I read that you have rewinder a motor with 5 turns of 12 strands of AWG 9 wire ! please help me on this, thank you very much.

[@CaptainAhmadi]

Can you not achieve a similar result by simply using a bigger/smaller prop instead of modifying the engine?

[@AcrodesignerLNSNI]

CaptainAhmadi No. In the original config the rpm is too high and the torque too small. At 7700 rpm the prop tips gets close to supersonic speed and biggest prop diameter is then 24 inch which is high disc loading and low efficiency

[@CaptainAhmadi]

Thanks mate. What does high disc loading mean?

[@AcrodesignerLNSNI]

CaptainAhmadi The amount of kilos thrust divided by the circular area that the proppeller describe is the disc loading. Pulling same amount of thrust is more efficient when distributing over a bigger disc. Just think of a helicopter rotor, huge diameter slow rotating prop that produce a lot of thrust. Same engine when fitted in an aircraft without gearbox will produce way less thrust. WW2 fighters all had gearboxes and the biggest diameter prop the design was able to handle. Was all about disc loading

[@CaptainAhmadi]

Thank you very much I appreciate the detailed response. If you don't mind me asking, do you have a background in aerospace engineering or did you just learn these things on your own?

[@AcrodesignerLNSNI]

CaptainAhmadi Yes, it is related to my daytime job as electrical engineer. Electrical propulsion systems for ships and especially hybrid ships and battery energy storage is what I do. The physics and math is quite similar for an aircraft electrical system so it it is related. Legally it poses some restrictions then when it comes to an commercial available E-Help. It is ok as long as hobby. But an commercial exploit is not ok. Technically it is so close to what I do in my job that according to laws in my country - my employer is the owner of E-Help concept. Not that I think they are interested tough. Only into big scale systems

[@julipegasus]

Hey Reidar, thank you allot for the very informative videos. So when you rewind from 3 to 5 turns did you end up with 64 or 106 kv? I have to rewind my rotomax 100 and want to reduce the kv by 1/3 Thanks a alot. Greeting Julian

[@AcrodesignerLNSNI]

In Delta it will be 106KV and in star 64KV. I flew it with 64 two years ago I think there are videos of Pink flying with the huge propeller behind. There were 2 mayor issues with the 64KV. First of all the propeller is huge about 120 centimeter in diameter. Very good efficiency. However, the low rpm and huge torque did not produce enough cooling air trough the motor stator windings. The outrunner bell is supposed to work as an centrifugal pump for cooling air and those lumbering low rpm's did not do a god job there. So motor temps were too high when take off power at 64KV.

[@Frifler888]

could you please tell me where you got the skema for the motor winding ? I can't find anything like yours

[@AcrodesignerLNSNI]

There is calculators for motor windings on internet. This is the one I use www.bavaria-direct.co.za/scheme/calculator/

[@SagaSeaCraft]

Can you suggest a good website that describes the rewinding theory and procedures?Thanks!

[@AcrodesignerLNSNI]

Just google on the topic and many sites will provide bits and pieces of information an the deeper understanding. Not one source that got it all

[@CryptoTopTrend]

Can this motor be used to make an electric motorcycle?

[@AcrodesignerLNSNI]

max slat Yes, probably

[@scottwilliams895]

@0:48 Can the "shaft extender"(part you grab with your left hand) be removed from the outrunner case/face on this motor? I see what looks like 6 bolt holes on the inside...

[@steveewen5438]

Hi Reidar, So what application are you planning for the 64KV rewired motor? What do think of the Alien 50KV 25000W 100V motor and a direct drive foldable mossie prop? Battery setup/ESC??

[@AcrodesignerLNSNI]

The 64KV has flown with the twin engined Fugly and the E-Help longe range cruiser. Both very nice flying, see my other videos. Next application is with "Pink", a Bautec Astir optimized for flatland thermal hunting. The 25 kW Alien motor is a totally different animal in weight and performance and will for sure turn Your nimble hangglider into an ultralight - not a thermal hunter. I try to keep things as small and nimble as possible ecause thermal hunting is my only goal. Not interested in making an electrical ultralight. That is easy but not as fun as hunting and mastering thermals in motorglider mode

[@steveewen5438]

+Reidar Berntsen I also am only interested in thermal hunting not an ultralight.Why I asked your opinion about the 25 kW Alien was the fact that it is only 50 KV and no need to rewire like you have with the Rotomax. I was thinking that its application as a direct drive motor is more practical than the Rotomax @ 7700 rpm.Alien also have a 80 KV 18 kW motor 70 Volts suggested power supply 18s. That still comes in around 5300 rpm.This would possibly still need a reduction drive to slow prop down??You are the man to go to with all the r&d you have already completed.What is the optimum rpm for the best thrust?Does swinging a prop of around 36" reduce rated rpm of the motor at all?

[@AcrodesignerLNSNI]

+steve ewen Rotormax 150 KV with 50 volt is 7500 rpm and the Alien 50 kV with 100 volt is 5000 rpm. Prop tip speed at 5000 rpm can drive a propeller diameter up to about 35 inches before getting into serious efficiency loss. I think the Alien motor is used by motorized paragliders and an alternative could be to get the vital parts from there and fit it into a powered hg harness. Because all the rest of stuff needed to build a E-Help kind of system with chargers and all can be a toll build. Yes, the Alien would for sure launch a hg with direct driven at 5000 rpm. However, battery burn, amperes per kg thrust, will be better for geared. A 35 inch diameter prop can handle maybe 8 kW before disc loading inefficiency takes its tolls. With better prop efficiency the size and weight of the battery is reduced. And battery weight is the essential place to save weight. I have seen copies of E-Help with lightening holes in the aluminum frame. Which is almost pointless given that the battery for a decent flight time is huge when the Rotormax 150 at 7500 rpm is very inefficient at 6,8 amperes @ 50 volts for each kg thrust. Anything above 3 amperes per kg thrust then the system is very short legged compared to its weight. Direct driven for hg then Toni Roth E-Lift system is about the best motor solution on the marked. toniroth.com/e-lift/

[@Flyit37075]

Would you comment on this 100kv motor. $289 USD www.getfpv.com/tiger-motor-u8-16-100kv-u-power-professional-motor.html? Its a pancake style , brushless out runner . The mfg claims it runs on 12s, 40amp esc and handles a 29" prop , I have questioned this and they were basically offended and gave me the " we are engineers and experts " talk. They claim the thicker copper windings increase efficiency and reduce heat so maybe they are onto something ?

[@henryphillips4683]

I went through my ultralight phase. It is quiet thermal hunting I am after too.

[@paulmartin8051]

isn't the ratio between star and delta a function of sqrt3? So I don't quite understand why the ration 64 to 109kV isnt exactly this? Would you be able to describe how you reconfigured the star delta element?

[@kewintaylor7056]

I didnt know much,but did he reduce kv cuz he need it to work with lower rpm? And what about another adventage of doing all that?

[@AcrodesignerLNSNI]

Main advantage is like gear box to be able to obtain higher propeller efficiency. With the original 150KV the maximum prop diameter was 25 inchrs to stay at tipspeed below critical 250 m/s. With lower 105KV the prop can be 34 inch diameter without going supersonic tip. Lower disc loading an significant higher efficiency. Compare numbers, the 25 inch needed 168 amp to produce 26 kg thrust. The 34 inch need 122 amp to produce 35 kg thrust. That is down from 6,5 amp per kg thrust to 3,5 amp per kg thrust. Viola - double range on same battery.

[@bisholim5377]

Could you please tell us where you downloaded the rewinding schema ? I have one and have wanted to rewind it but I can not find nothing on how to rewind it. It would be a Great help if you could help. Thank you....:)

[@AcrodesignerLNSNI]

www.bavaria-direct.co.za/scheme/calculator/

[@hotliner2872]

What in gods name do you put a 34x22 3 bladed foldable on? If it's a glider... Can I see it? Where do I get one :-)?

[@AcrodesignerLNSNI]

Small and lightweight for motorgliding. I flew a 60 km cross country flight with it. See my video "Captain Slow VS the Stig"

[@onedoodadyoung]

More great work from the master!! Thanks Reidar for all your ReD. Am working on the gear drive e-help system and would like to know your new LiP battery source. Thanking you. I amDanny

[@AcrodesignerLNSNI]

Hello Danny. My source for 7s 6000mAh 60C LiPo batteries is norwegian model airplane vendor www.rc-batteri.no. However, main reason for selecting this vendor is logistics. Shipping LiPo from China to Norway has become more strict and this company do all that stuff for me. Any LiPo at this big size and spec will do the job. The old direct driven E-Help was brutal to the batteries pulling some 160 amperes for tiny 25 kg thrust. The gesred Mossie is kinder to the batteries producing 35 kg thrust at 120 amperes. What I see with the rewinded motor that in delta and with a cheap wooden prop 34x12 it produce 25 kg thrust at 90 amperes. This means that endurance is close to doubled for the direct driven E-Help.

[@onedoodadyoung]

+Reidar Berntsen ,Thanks for the info. I had one other question about the gear drive. You show T10 size on the picture of the XC version. Do you think the T5 size of cog pulley with a 25mm wide belt is big enough if using the soft start on the ESC? I was going with 18t x 60t for 3.43/1 ratio with 50x28 folding prop. Thank you Danny

[@AcrodesignerLNSNI]

+Danny Young T5 sounds a bit small. Once calvulating the Mossie even the T10 was marginal

[@onedoodadyoung]

+Reidar Berntsen I was thinking the same thing so I went with the T10. Thanks again Danny

[@henryphillips4683]

+Reidar Berntsen ..Thanks VERY much for your generous rewind video of the Rotomax 150! Danny and I are flying buddies and we both have been waiting for the Rotomax 150 on backorder for a month now. (we are both 66 and knees are bad) We are not sure when they will come, there must be a LOT of people wanting one? Danny wants to build a reduction drive but I am not sure I can do it. I was wondering if I could pay you to rewind one that you have or sell me one that you already have rewound? Hank

[@andreasspecht3903]

Do you choose the star or the delta connection to the esc?

[@AcrodesignerLNSNI]

Delta

[@pierrolalune59]

Very nice work! What about the power? Is the max power also reduced? Thanks

[@AcrodesignerLNSNI]

Yes, the power is reduced from 9,8 kW to about 7 kW when You look at only the electrical side of it. Voltage is same but current draw is lower and P=VxI. However, this lower 7 kW actually produce way more useful thrust to the hangglider than the screaming 9,8 kW. The "new" 7 kW produce 35 kg thust as the old 9,8 kW due to low propeller efficiency only produced 26 kg thrust. The energy must be taken from a relatively heavy battery. So what You want is that the energy carried in that heavy battery is spent as efficient as possible. Converting heavy battery power into noise and losses is useless engineering. Converting battery power into silent and high efficiency thrust is what You want. Viola - then You can reduce the size of the battery to half the weight for the same performance as before. We cut 5 kg on the total rig just by optimizing the motor and propeller efficiency. Everybody talks about super batteries. Well, there is only small 10% improvements in that end. However - it is way better to tweak the other end - the consumer end - and get the job done at half the battery consumption.

[@edisonphoenix3303]

@@AcrodesignerLNSNI Well Said!

[@LuyandaMzuvukil]

I love that motor

[@sidla6989]

what mm diameeter is the copper?

[@AcrodesignerLNSNI]

0,6 mm

[@amjedfadhel6463]

Can you help me please I need to buy a blades for my project and I don’t know where to get it from?

[@busbaru7501]

hobby king

[@FredoCorleone]

What a beast

[@pedrojuarezherrera]

Hay algún programa, software, para cálculo de diámetro de alambre, vueltas y podían de bobinado? Gracias.

[@dariodalcin5177]

Did u balanceeeee it?

[@AcrodesignerLNSNI]

Nope. It is balanced pretty well from Turnigy

[@moamoa3303]

i love the music,,,, old british tv

[@programamones1230]

Olle con que circuito lo estas controlando ? Como lo haces girar ? Saludos me vi todo el vídeo y me agrado

[@dageide6008]

Er du norsk Reidar? Peiling på controller og flere motorer tilkobla?

[@AcrodesignerLNSNI]

Dag Eide Norsk og fra Tønsberg 😊. Ja, to motorer på en ESC har jeg erfaring med. Så lenge motorene har samme egenskaper går det helt fint med de fleste ESC. Jeg fløy med et slikt oppsett, se videoene om "Twin E-Help, Fugly"

[@behnamameri233]

it was a great job.perfect

[@mtmytech6187]

Nice video

[@michaelhansen1232]

just asking,,,,, Why...??????? lower rpm, lower HP. lower amp´s......????? wouldent it have done the same reducing the volts. or almost. looks to me like alot of work for a small change ind specs...?????

[@AcrodesignerLNSNI]

Well, power (kilowatts) is voltage multiplied with amperes. This motor, both original(150KV/7700rpm@14s) and rewound(105KV/4400rpm@14s) has a max amper limited to about 150 amperes. More than that it fries the stator windings. So, keeping the amperes constant at 150 amp reducing the volts, what will happen? At 14s and 52 volts the electrical power is 52x150=7,8kW. Difference in original and rewound KV is ratio 105/150=0,7. To keep same rpm, tip speed and disc loading on a propeller of 34 inch diameter then voltage must be reduced from 52 volts to 36 volts. Electrical power will then be reduced same ratio. Means 36x150=5,4kW. In practical the pitch of the propeller must be reduced from 14 to 12 or 11. Thrust reduced from 34kg to 26kg. So that is the answer, -reducing voltage basicly just means throttling back, loosing power. If the motor had been able to absorb 200 amperes without overheating You could keep the power up. However, supporting 200 amperes requires bigger gage wires and more heavy copper in the rig. We try to keep weight down and increasing copper weight with more than 30% is not way to go. The about 7kW at 135 amperes that the todays 2019 E-Help rig consume from battery produce 35kg thrust. In 2013 I first flew with a rig that consumed 168amps for 26kg thrust

[@AcrodesignerLNSNI]

...continue: this increase in thrust and decrease in amperes are basically result of optimalization of propeller efficiency. Effectively it is an improvement in transformation of electrical battery power into usable physical thrust more than 50%. In practical more. Because the lower load on the battery keeps the battery from overheating and dropping voltage during climbout. The new setup also keeps the battery inside the butter zone for best performance. Many of the E-Help homebuilders tend to stress the batteries hard on the C rating and performance (voltage) drops off pretty fast. Low stamina on this rigs. My modern batteries are 65C but I don't want to stress them more than 10-15C. Because the aircooling on my rig can not support utilizing the maximum C rating. Many of the low cost LiPo batteries from China (Zippy and similar) claims a C rating of 25C. Been there done that. Keping them cool 22 deg C at even 15C is a huge problem. What happen if You "cook" them at let's say 40 deg C? Well, they will never be the same again. Maybe puffing up and internal resistance will increase dramatically. Run them on the computer charger testbench and You will find they are unservicable for flying. Very expencive lesson learned.

[@JaxLabs123]

very impressive

[@rostravelventure]

So adding lower gauge wind can consume more amps? I want to rewind my motor for High KV and can take up to 400 continuous amps on a 6 pole motor. What is your input on this? Thanks!

[@mackattack8627]

Just buy a Plettenburg or Lehner Huge Outrunner in any custom Kv you want they are definitely high amp hungry monster's above 400-500 amps no problem the epoxy staters and high temp wire + liquid and air cooled German quality much better than any Turnigy can💪

[@danb37]

Thank you. So much info here in the comments to this single video

[@johnconrad5487]

wire area 0.6 mm^2. you gave area and not diameter. that's 19 AWG and diameter would be #23 AWG which is what u used. thanks for the great lesson in winding a 3 phase motor.

[@mikelemon5109]

how do you know how to calculate every thing? can you lead us to some tutorial on how to do that? I'm also interested in rewinding a 5065 motor to a lower KV but don't know how to. Also what are the disadvantages in lowering KV on BLDC motors?

[@AcrodesignerLNSNI]

Michael Tutorial then actually googling and reading articles online is best. Many people have put online very good stuff. Disadvantage with lowering KV on outrunners is mostly that the cooling is reduced because the lower rpm reduce the centrifugal pump effect that the bell creates. Basicly pumping less air trough the motor. Then the capability to cool stator windings an iron is less and total power need to be reduced. The original Rotormax is 9,8 kW but the rewound is 6-7 kW

[@AcrodesignerLNSNI]

www.bavaria-direct.co.za/scheme/calculator/