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  1. #201

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    RE: HK Small Bolt Hydro same as HOTR

    ORIGINAL: carakter
    @Yura - you seem to be good at calculating things . . can you be our resident engineer / mathematician and do the calculations forthe proposed setups?
    What do you mean "our resident engineer"?

    Also,outrunners produce more torque compared to inrunners . . which is why it's the motor of choice for planes and helis.
    But inrunners sometime sad to withstand much more power, even than rated...
    Also inrunners have coils on outer side and it's better for watercooling...

  2. #202

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    RE: HK Small Bolt Hydro same as HOTR

    @nickster - I can only guess what happened to your boat.

    1) The motor is trying to attain it's rated RPM - it can't do that if it's having a hard time spinning a bigger diameter prop. And since your motor was burning hot after sometime, it only means that it's struggling to get the RPM spinning to where it's rated at.Heat aslo degrades the windings, these cheap motors are not known to use quality wires, tight windings and good insulation - hey you get what you pay for right? - I call them throw-away types! A Wattmeter - www.hobbyking.com/hobbyking/store/uh_viewItem.asp - would do you a lot of good in determining if the setup is ok. If you can get the Eagle Tree logger, much better!

    Water cooling is important, but it will only delay the inevitable if the setup is a mismatch . . like say a degrade in motor and or battery performace after sometime.

    2) Since you stated that your battery was hot and swelled, then it means it was having a hard time supplying the spike in the ampdraw demand of the motor - probably exceeding it's rated supply capability. What's your lipo rating? 1.8A x25C = 45amps continous . . supposedly . . take out a few because it may be a bit over rated
    Take temp readings of your lipo as well. It's not supposed to get hot, warm at most, not hot! Under amp / voltage supply will also overwork your motor.
    .
    3) Your ESC seems to be fine (or is it? temps ok?) , then you know that it can handle higher ampdraws - more than what the motor is asking for. I don't see your ESC settings but usually, using high Kv motors require High timingand faster PWM (16Khz + ) so as not to be at sync loss. Also try selecting Hard start . . . and no brakes!
    Yes, you should have taken a video so you can compare and see the different combos performance.
    Don't be discouraged . . . taking risks is part of the discovery into getting things just right!

    @ Yura - can you do the math on this?

  3. #203

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    RE: HK Small Bolt Hydro same as HOTR

    Thanks for the answer.
    My ESC temperature is normal. Is it a bit warm, not hot.
    The Lipo is very hot. So I guess it has to work hard to provide enough amps for the high kv motor?
    The 4800kv outrunner was way too hot! I burn my finger. I know that high temps are bad for the magnetic function. This motor won't stay long in the small bolt. I am very happy with the octura x432 and I prefer to adjust my setup to this prop. So I would rather take a motor with less kv (now ordered 3600kv) and stay with the x432 than change to a smaller prop in order to use the high kv motor (wich is also negative for running time and wear of the strut and shaft). With a bigger prop the boat 'moves' more water wich will increase speed too. But I have the feeling that my boat isn't showing his full performance compared to youtube video's. I 've seen the stock engine's performance but it looks like my boat is restricted (by the batteries I use?) But again I know this will only be seen at a video, wich I hope to create today.

    The information about my batteries are as follows:
    2x 2200mah 3s 20C Lipo
    1x 1800mah 3s 25C Lipo

    The outrunner will be removed soon because I don't like the heat. Maybe I will put 4Son it, seeing if it fries :P

  4. #204

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    RE: HK Small Bolt Hydro same as HOTR

    Yes, sometimes too high a Kv is not good for boats. Remember, water is heavy to push and requires torque - which high Kv motors won't have at low rpms's. Also, lower Kv motors require less amps - as Yura stated correctly, you can get the same (if not better) performance with low Kv - 3S or 4S - and bigger props.
    In your test run, just go a few laps and check the temps everytime. Don't wait for it to slow down. This way you'll prrevent any overheating issues and save your components.

    Thanks for the heads up on the 4200Kv outrunner. I'll make sure to be very careful in doing test runs with it.

  5. #205

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    RE: HK Small Bolt Hydro same as HOTR

    @nickster - check Pekka's setup with the 4200 - http://www.rcuniverse.com/forum/m_97..._5/key_/tm.htm#

    I hope the others will update us on how their Bolt's are performing.

  6. #206

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    RE: HK Small Bolt Hydro same as HOTR

    Sure in this case motor give very much rpm, and with the prop used it must have very big speed, that can't be reached.
    So big part of energy transfer to heat. It's bad...
    Battery definitely must NOT become hot. It usually becomes hot at the end of the charge. Usually you must stop using it at this time to prevent puffing.
    I'll try to write down some calculation later.

  7. #207

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    RE: HK Small Bolt Hydro same as HOTR

    I agree on you that it's better not to transfer energy to heat. So I guess the 5750 is an overkill in combination with the octura x432. I think it did damage my battery when trying to get enough amps to move the water.
    I just ordered a 4200kv outrunner, just as Pekka L, to try if this will 'fly' as he said. (is there a video of Pekka L's boat?)
    I want to find out where the middle is between torque and rpm (using the x432 prop), so I have the best of two worlds.
    As said in one of my first posts, I have this small bolt for fun and DURATION. I don't want the strut and shaft to wear too fast, so I don't have to change them every month. A less kv motor combined with a 3S or maybe 4S will do as well I guess.
    On the shore the high kv motor screams out loud, but in the water there is too much resistance so it can't reach the rpms and it is dragging amps out of the battery (this will explain the extreme heat).

    @carakter:I tested a 4800kv outrunner, not 4200kv. The 4200 I ordered just a minute ago.


  8. #208

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    RE: HK Small Bolt Hydro same as HOTR

    OK.

    If we need to increase speed, first that we can do is to increase prop size (or pitch?).
    It's good idea and we all know about it, and most tested it.
    We get increased speed and increased current. We have to carry about current not to exceed limit for the ESC and for the motor.
    (We can measure it with Wattmeter or at least check that ESC&motor not hot).
    MOSFETs in stock ESC can withstand continuous current up to 85A (but with very good cooling). So rate 30-40A with watercooling seems to be normal. ESC will withstand more current but also can burn even at rated currents and stock setup (as mine).

    We should measure speed and compare it to calculated speed. Voltage*kv=rpm (~12*~2600=~30,000rpm), pitch=1.4" it must give about 30mph speed. (http://www.props4u.com/prop_chart.htm) It's very interesting that nothing said there about propeller diameter. Don't know if this matter on not.

    If speed differ very much, than we have more propeller slippage. (Don't know still on how to decrease it - to change pitch or diameter).

    If we need to increase rpm best way to do it is to increase voltage (change 3S to 4S). But first we should check if the motor and the ESC can withstand this voltage. Don't know about the stock setup & 4S, but I wouldn't check it.
    So if we can't change 3S to 4S and not satisfied with stock setup and different props, we can change motor to another with different kv.
    This motor must withstand Max current of at least 20-30A I think. Because we need to increase speed, we need to get more Watts at least.

    Now we can calculate new data on RPM and find out new speed. But nothing said on how to reach this "ideal" speed.

    What I wanted to say: we have talked about 5750kv motor, that in our setup must give more than 50mph while sinking probably much more than 50A. But with 10A max current it must burn very fast. In reality it can't deliver so much power and not burned because of watercooling and other things.

    Let's try inrunner motor with a bit higher kv (say no more than 3500) with max current rating of more 30-40A while watercooled. Or it must be at least same diameter motor and not shorter by lenght.

  9. #209

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    RE: HK Small Bolt Hydro same as HOTR

    @Yura - my head is still spinning from your explanations!hahahaha . . .

    Looking at the Props Chart, I put in the variables we have - 30,000rpm, 1.4 pitch, 20% slip . . .it calculated that 60MPH is theretically possible.
    Hmmmm . . . now tofind out what prop that is? 2 blade, 3 blade, detounged, cleaver? Too many variables!
    Most BL motors have a rating of 50,000 RPM (so they claim). So if we use 4S (14.8V nominal x 4200Kv = 62,160RPM . . . yikes! I smell something burning!

    Hopefully, I can test the 4200Kv outrunner this weekend - on 2S and 3S . . . with the stock prop.
    If I do, I'll fill you in on the Watts and ampdraw using the Wattmeter.
    I wonder how we will be able to get the motor's rpm while running in water. That will make things easier.
    Let's continue posting all ourtest resultsso we can learn from each others success . . . andfailures.

  10. #210

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    RE: HK Small Bolt Hydro same as HOTR

    @ Yura:
    Nice piece of math It makes sense.
    I am for about 90% sure that the stock ESC will burn with 4s. the stock engine may stand a bit longer, depending on throttle usage. The max amp of the motor may not be exceeded. If we play with the throttle (half throttle / full throttle) than it may survive.
    My esc can handle up to 6 cells so my ESC won't be a problem. If I can find time I will try 4S on the stock motor. If it fries than it is too bad. I do have 2 spare motors (4800 outrunner and 5750 inrunner) and two motors ordered (4200 outrunner and 3600inrunner) where I expect the best results with the 3600kv inrunner. I like to keep my watercooling also.
    The 5750kv was bad for my battery so I guess I won't use that anymore because the motor needs too much amps for reaching his rpms.
    I think the stock motor 2604kv will give good results with 4S Lipo if the stock motor will survive this. I have seen a video on youtube with 4S on stock motor but the comment says he fried the engine after 1 run.

  11. #211

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    RE: HK Small Bolt Hydro same as HOTR

    Hello guys,
    Yesterday evening I have been a lot of testing and I got some major developments
    First of all I want to mention the solution for more speed and power: 4S LiPo on the stock 2604kv motor.
    The first thing I did was a run with the already placed 4800kv outrunner, after a minute or 3 the boat stopped and I went home. When I opened the hull there was smoke! conclusion: I fried the 4800kv outrunner, I measured the temperature: 106+ degrees Celcius (223Fahrenheit) and the coil was burned black
    <P ALIGN="CENTER"></p>

    here is the temperature

    <P ALIGN="CENTER"></p>

    So I decided to replace the stock motor because the 5750 inrunner was heating up battery really bad.

    I than decided to try place two 2s 1200mah packs in serial so end up on 4s. That was a major difference.
    I had lots of power (more than enough) so I had to run on half throttle and playing with full throttle. The boat gets decreased handling and one time it ended up flipped over on its roof (no water leaking )

    I could place the two 2s packs in both sides of the hull but later I decided to tape them together and place it in the middle of the hull.

    Here you can see the both packs hided in the 'arms'

    <P ALIGN="CENTER"></p>

    Here the two 2S packs

    <P ALIGN="CENTER"></p>

    And here are my two 1200mah 2S packs taped together in the center-front of the hull

    <P ALIGN="CENTER"></p>

     I also tried a 3000mah 4S pack wich I recently had ordered for my other boat (wich is more providing spare parts for my small bolt)

    This pack is a bit heavier but the Small Bolt could handle it, it planes as well but a bit less smooth than the two (very small) combined 2S packs.
    I am just started trying to sell all of my 3S batteries and went looking for a couple of 4S batteries.

    <P ALIGN="CENTER"></p>


    I have to warn other who'll trying to run on 4S:
    1. I replaced my stock ESC for a 60A esc wich can handle up to 6 cells Lipo
    2. I didn't run the stock motor 2604kv full throttle for longer than 5 seconds (wich looks a bit short but the Small Bolt travelled a lot of distance than) because I don't want to burn the stock motor too.

    So 4S is the best bet for me/.

  12. #212

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    RE: HK Small Bolt Hydro same as HOTR

    ORIGINAL: carakter
    Hopefully, I can test the 4200Kv outrunner this weekend - on 2S and 3S . . . with the stock prop.
    I think no reason to test 4200kv motor on 2S (7.4x4200=~30,000rpm) so it seems to work same like the stock motor.
    Only thing you get is increased current (You want to get at least same as stock or more power from battery, but with less voltage battery it must draw more current).
    Increased current will increase voltage drop (and power loss) on connectors, wires, ESC etc.
    So increasing kv and reducing voltage to 2S is worst case I think.

    Unfortunately I can't do the same things now.
    It's getting a bit cold and windy. And I'm able to run the boat at quite big lake and only at the weekends. So I always wait for wind to calm down.
    Want to buy 40x30 prop. Than maybe 40x32. Don't want to change motor.

    About shaft: I disassemble it again to clean and grease it well. But I could NOT solder shaft end (from the motor side).
    I tried to do it at different temperature setting at the 60W iron 350-450C. I have soldered a lot of things, but soldering steel is always very hard task. Shaft don't want to tin.
    I tried to clean it from old grease, but it can't be down completely. Have used very good flux and good solder. The only thing I think of is to use soldering acid, but actually worry about it because it will cause rusting.
    Have you done it when the shaft was still ungreased at all? Are you sure it has soldered well or just covered with solder?

  13. #213
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    RE: HK Small Bolt Hydro same as HOTR

    I am thinking of getting the bolt but I have a question. What size servo does it take (micro, mini or std.).
    I am ordering now and would like to get a metal servo too.
    KM baja...Dynamite...HPI Firestorm...Small Bolt...Easy Star...Wild Hawk

  14. #214

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    RE: HK Small Bolt Hydro same as HOTR

    @Yura - yes, I agree that the 4200 will be slow on 2S, I just wanted to find out what results Pekka got from his run.

    About your flexshaft . . . I guess I was wrong about your using a 60W iron . . . I used a 100W iron.
    You could either getahotter iron or . . try melting solder in a container and dunking the flexcable into it.

    @nickster - I'd be very cautious about using 4S . . . most, if not all of these small motors are designed for up to 12V only.


  15. #215

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    RE: HK Small Bolt Hydro same as HOTR


    ORIGINAL: madmax93

    I am thinking of getting the bolt but I have a question. What size servo does it take (micro, mini or std.).
    I am ordering now and would like to get a metal servo too.
    It uses a micro servo but you can shoe in a Mini servo as well.

  16. #216

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    RE: HK Small Bolt Hydro same as HOTR

    I am very cautions with the throttle
    But tonight I did 4 runs on 4S and still the motor is about 25-30 degrees celcius. So no problem with the heat.

  17. #217
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    RE: HK Small Bolt Hydro same as HOTR

    I just bought one with a couple of batt. and a new servo. Yipee!!
    KM baja...Dynamite...HPI Firestorm...Small Bolt...Easy Star...Wild Hawk

  18. #218

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    RE: HK Small Bolt Hydro same as HOTR


    ORIGINAL: nickster46

    I am very cautions with the throttle
    But tonight I did 4 runs on 4S and still the motor is about 25-30 degrees celcius. So no problem with the heat.
    Really? Did you do full throttle passes? Did you mean you went through 4 battery packs? or just 4 passes?
    Because if you went through 4 battery packs then that is unbelievably COLD!

    I just re-installed back the stock motor in preparation for tomorrow afternoon's run.
    I wanted to be able to test itwith the Octura props but that will have to wait . . it's in the mail though.
    I do have a larger plastic prop . . just don't know it's dimensions.
    Hope everything turnsout well!



  19. #219

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    RE: HK Small Bolt Hydro same as HOTR


    ORIGINAL: madmax93

    I just bought one with a couple of batt. and a new servo. Yipee!!
    Good for you! Update us on your runs.

  20. #220

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    RE: HK Small Bolt Hydro same as HOTR

    I did 4 runs (since yesterday a couple of 8) total on 4S.
    The temperature that I measured was after I run the battery totally empty so it couldn't reach his rpms anymore. the measurement was after I emptied two batteries after each other.
    I guess when I measure the themperature after I got high rpms the temperature will be a lot higher, but not too hot.
    I am running on 4s for about 4 days (8 runs) but I don't expect problems to come up. Maybe I will try the 5750kv motor on 4s this week, but right now the weather is best for taking the boat to the water and not to be hobbying in my shed.

  21. #221

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    RE: HK Small Bolt Hydro same as HOTR



    The hottest temp your motor will get is right after each run.
    So if you're getting cool temps then you just hit the sweet spot for the stock motor!
    Must be the water temp . . . how cold is it there?
    What prop are you using - X432?


  22. #222

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    RE: HK Small Bolt Hydro same as HOTR

    Yes, I use the X432.
    The average temperature in the Netherlands is 16 degrees Celcius, I don't know the water temperature.
    But as I mentioned a few post earlier, I am very cautions with the (full) throttle. I am not running full throttle for a long period. max. 5 seconds.
    And I am running half throttle sometimes to pick up cooling water and to let the motor a bit cooling down.
    So it is not just put 4s on it and go!

    Another point of interest is maybe the water pickup in the rudder. The water pickup is on the left side (from behind)so on right turns it isn't picking up water. And most of my turns are to the right as I am running clockwise.

  23. #223

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    RE: HK Small Bolt Hydro same as HOTR

    I think we can't talk about motor+ESC temperature after run...
    Because of watercooling. It is quite effective. But motor or ESC can be burn in deep during run, even when surface (watercooled)  seems just warm after run.
    So we must make measurements.

    Yesterday I was able to run my boat for 4 packs
    I also have bought 1.4x30 and 1.4x32 props.
    It was cool. I tested standart 1.4x27 prop, then 1.4x30, then 1.4x32.
    I wanted to put Turnigy Wattmeter into the boat and make measurements during run, but unfortunately I haven't been able to do it, because it is too big and tight

    What can I say:
    First run with stock prop.
    Next pack with increased size prop.
    It's running better with 1.4x30. I can't say, I saw, speed definitely increased much, but it seems to be so.
    Next pack tested with 32 prop. It also seems like speed increased, but just a bit.
    After 1.4x32 I tested stock 1.4x27 and it's interesting that I haven't seen much difference.
    With 30 and 32 props boat begin to plane very fast. Seems like immediately, while with stock prop it can be easily seen that it needs time for speed up and only then it begins to plane with interesting "sound". I like this sound, but can't hear this transition from run to plane with 30 and 32 diameter prop
    Also 1.4x32 propeller, I have bought (same type as stock) is too long. I mean that with it I'm not able to screw-on the nut fully. Only about half the screw.

    So I will choose stock or 1.4x30 (I think same as Octura 430).

    It will be very good to make measurements of speed with help of radar and Power measurements with Wattmeter inside the boat.

    What I think of: how much amps draw the stock motor with 430 prop when running at full speed?
    We can put 1800-2200mAh 3S battery inside. Usually it is rated to 20C. Some 25C-30C.
    But even with 20C current (36A-44A) we will get less then 3min runtime. (I run almost all the time at full throttle).
    3min is quite few for me. (Assuming time it takes to wipe out and retape the hull).

    So it seems to me that there is NO REASON to make a setup that will draw more than 35A. Or at least 45A.

    If stock setup with 430 or 432 prop consumes about 20A it is possible to increase power some way. (By changing motor for example).
    If it consumes about 30A it's no way to modify anything, because we will reach limit by battery or acceptable runtime.

  24. #224

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    RE: HK Small Bolt Hydro same as HOTR

    ORIGINAL: nickster46
    Maybe I will try the 5750kv motor on 4s this week
    And don't forget to put a piece of meat nearby Think it will be able to fry well


  25. #225

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    RE: HK Small Bolt Hydro same as HOTR

    @Yura - In my experience with the SV27, I took Wattmeter readings, both whilst the boat is being held back by someone and, whilst running.
     I didn't see any difference in reading, so I guess it's saffe to assume that you can do readings in the bathtub.
    I think peak ampdraws occur whilst the boat is trying to take off / plane. I may be wrong.
    In any case, I think it would be impossible to run the boat with the wattmeter inside, no space.


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