PARKJET MOTOR BENCH TESTING

Discussion in 'Electronics' started by e3_Scott, Jul 6, 2013.

  1. bimoadiprakoso

    bimoadiprakoso Top Gun

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  2. Very strange, I even charged up the battery again to do it all over. Still the same results, at 50% throttle about 4 oz less and at 100% about the same 4 oz less.
     
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  3. e3_Scott

    e3_Scott Top Gun

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    Hi Jeff -

    One of the reasons it is interesting to test different props on the bench and the field, unfortunately the logic of increasing pitch and/or diameter don't always apply to increasing thrust and performance.

    Certain props just seem to have optimum RPM ranges and when they do not operate in those ranges, the expected performance is not there.

    In my experience for example, the 6x4 EMP/TGS prop was a very inefficient prop for 2200/2700 Kv motors on 3S, high amp draw and watts, yet often equal or less thrust on the bench and certainly no improvement in performance in the air over the 6x3 EMP/TGS prop.

    Similarly, the Master Airscrew 6x4x3 prop seems to have a specific RPM range on the smaller motors where it is happiest, take it beyond that and thrust and flight performance no longer increase, but the motor/ESC/battery combo have to work much harder.

    I know efficiency is not what you are looking for, but when I look at the watt numbers you are seeing in your 6S testing with the NTM 2200 motor compared to the thrust numbers, there is an incredible amount of power (watts) being produced without a comparative huge increase in thrust.

    When I tested the NTM 2700 on 4S with a 6x4 prop, I saw 68A/804W and 68.4 oz of thrust, so about 11.7W per oz of thrust. Theoretically, the no load RPM would be 39960 (14.8V times 2700 Kv).

    In your test above with the 2200 motor on 6S with the battery at 24V, you saw 70A/70 oz of thrust and 1700 W, 24.2W per oz of thrust with a theoretical no load RPM of 52800 (24v times 2200 Kv). So you are drawing the same amount of amps, the motor is producing an incredible amount of power based on the watts, but not a whole lot more thrust even with theoretically far higher RPM.

    So looking at the numbers HK shows from their testing and specs on the Propdrive V2 2836 2200 Kv motor, your amps is 40% higher than what they rate the motor and watts is 2.5 times higher than they have ever tested. Will the motor last very long pushing it that far beyond it's limits? Perhaps, but careful throttle management would need to be applied I think.

    So the 6S battery seems to be producing incredible amounts of power at the motor based on the watts numbers you are seeing, but where it matters in the air, the thrust numbers are not following suit I would suspect and without adding a ton of weight to your plane, you would have to fly with a low Mah 6S battery which will shorten your flight times considerably.

    Interesting test numbers though, I notice that HK has the 2700 Kv motor back in their Propdrive lineup to replace the old NTM 2700 motor:)

    Good luck!

    Cheers,

    Scott
     
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  4. Great info Scott as always much appreciated, this was sort of play time just to see what would happen. Lars's flying style there are very few times he gives it 100% throttle so even when he is running it on 5S with a 6X4X3 prop which more then likely if you did a real good wot run you would burn it out but short burst huge instant thrust. I just found that the amp draw seemed really low compared the amount of watts.

    The 5X3 versus the 5X5 prop though, low rpm to high rpm and it didn't matter where but the 5X3 produced better results all around.

    Battery is being discharged back down to storage level . ;) I have nothing to use it in anyways, weighs more then all my planes put together. :D :D

    Cheers
    Jeff
     
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  5. e3_Scott

    e3_Scott Top Gun

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    Always interesting to experiment, occasionally I have stumbled upon the right combo just by playing around, nothing too scientific, just putting together motors, props, ESCs and batteries I had laying around.:)

    Cheers,

    Scott
     
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  6. I did pick up a Propdrive 3000KV just to compare it to the NTM 3000kv motor, it is different and shaft is even smaller but not bad numbers out of it. I tested in a 70mm edf agains't the NTM 3000kv plus the Paidiss 3000kv motors . I haven't thrown a prop on it yet to see those numbers but here is the link to my post on this test.

    https://rcpowers.com/community/thre...-edf-parkjet-design.21857/page-28#post-290704
     
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  7. e3_Scott

    e3_Scott Top Gun

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    Hi Jeff -

    Browsing through the new Propdrive series, specifically the 2836 2700 Kv motor which I have tested and flown with quite a bit in the past, it appears like the specs are identical to when they were called "NTM" series, but for the same amount of money, they throw in the bolt on prop adapter which is a nice touch:)

    It will be interesting to see as folks test and fly with more of the Propdrive series if there is a difference in quality control. I remember testing NTM 2700 motors that would never pull more than 48A or produce more than 480W/38 oz of thrust no matter what I did and others that safely outperformed HK's specs pulling 60A and producing close to 700W/42 oz of thrust on 3S.

    Another reason why it is helpful to have a watt meter and thrust testing setup when you are truly trying to optimize speed and performance, sometimes just a different motor of the same brand or different ESC and the performance increase can be significant.:cool:

    Cheers,

    Scott
     
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  8. Nightswatch

    Nightswatch Top Gun

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  9. Nightswatch

    Nightswatch Top Gun

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    ok weight unknown 160 percent scaled mig fulcrum on 4s with thrust vectoring rear prop pusher 4 pound plane ???
     
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  10. e3_Scott

    e3_Scott Top Gun

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    Theoretically, two motors producing a total of 2 Kg/4.4 lbs of thrust should power a 4 pound plane, but it won't fly fast and it won't fly well. You will probably need to fly with very high throttle setting resulting in shorter flights and much more wear and tear on all your power system components and very limited reserve power to get yourself out of trouble.

    The specs at the link you shared show spinning 5" props, so I would assume a large plane in front of those props is going to block a lot of your air flow, meaning you will probably not be getting full rated power from your motor/prop combo right off the bat.

    If your plan is to build a plane that is up scaled to 160% over original, I would suggest perhaps you might want to match your plane with a power system that produces 160% of what the designer recommends as a starting point which then might throw off your 4 lbs estimate somewhat.

    Cheers,

    Scott
     
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  11. Nightswatch

    Nightswatch Top Gun

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    Thanks so for instance your plane you just built 160 percent scaled up what would be a good choice for twin set up what about bigger props ??
     
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  12. Nightswatch

    Nightswatch Top Gun

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    guessing with bigger props would mean more amp draw so instead of 2200 kv drop it to 1125 or 1000 kv motors ?? just trying to figure out what one would need
     
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  13. e3_Scott

    e3_Scott Top Gun

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    You might be better off asking the designer of the plane you are planning on building in all honesty. You are asking me for advice that is out of my league for what I have tested and normally use.

    Jeff has been doing a lot of testing and has a lot of experience with bigger power setups like the NTM/Prop Drive 2200/2700/3000Kv motors. Flybyknight22 has contributed a lot to this thread with motor setups spinning 7" props which might be close to the size props you might be needing or wanting to spin, if increasing the design that much allows you to spin 7" props. I would touch base with those gentlemen directly. Jeff also has experience setting up and powering a twin setup with his original PI Su-37 G1.

    Sorry I can't be of much more help than that, good luck:)

    Cheers,

    Scott
     
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  14. I was going to add the HK link for a motor that I use on ShoeString, considerably larger then these normal little guys we use but HK's website is doing some maintenance . This is the link to the specs on my thread. I am running a 8X8 prop on it right now and it has tons of thrust, the amp and watts are very reasonable so if I really needed to I could go larger. Each motor pulls about 3lbs or more with the setup I have in it now.

    https://rcpowers.com/community/threads/pi-shoestring-build.20955/
     
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  15. Nakul

    Nakul Ace Pilot

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    Hey Jeff, my ntm 3000 makes strange vibration at 30% throttle, with any prop on 3s & 4s. however Pre and post 30% its just fine and no vibrations at all. Love this motor. Going to try tgs 6x3 prop with it on funjet when i'll be home next.
     
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  16. XDmToter

    XDmToter Ace Pilot

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    My guess would be a bad or failing bearing.
     
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  17. Nightswatch

    Nightswatch Top Gun

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    Could be number of things cross thread prop un balanced bent motor shaft a nick in shaft and like you said bearing
     
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  18. Nakul

    Nakul Ace Pilot

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    was wondering the same, the motor is only 15 flights old. It performs perfectly fine get pass the 30% throttle. or even at 25%. Was also wondering could there be any esc timing related issue.
     
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  19. e3_Scott

    e3_Scott Top Gun

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    What ESC timing are you running with this motor? My experience has shown that low timing is the best setting for all the motors I have tested and use. You may get more power from medium or high setting, but the motor will have a tendency to "skip" where it will be running fine, then either lose power momentarily and then start running again.

    I've even had situations when experimenting with medium or high timing where the motor would seem like it was running at low voltage cutoff on a fresh battery, often if I chopped the throttle to zero for a split second then advanced it, the problem would correct itself.

    Other than the suggestions already made about your motor vibration, are the throttle points set correctly? Perhaps there is some sort of mix or throttle curve that got set up in your transmitter that might be causing some issue at that specific throttle setting?

    Good luck with it:)

    Cheers,

    Scott
     
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