What difference does a stiffer prop make?

Hi Everyone -

Yesterday I was doing some bench testing with the Multistar Viking 2208 2600 Kv motor, and by mistake made an interesting discovery😏  You can read more about that testing on this blog post.

One of the props I tested was the 6x4 KMP prop which I discovered sometimes have a bit of a quality control issue which I wrote about in this blog post.

Essentially, here are pictures of the two props when I bent them, first the bad prop.

This is the good prop, I had to push on the hub to get it to bend this much, so it is the stiffness it is supposed to be😊 

As I was doing the testing, I saw the "bad" prop laying on my very clean, well organized work bench...NOT!!!😬😳😵, anyway, I assumed it was the good prop and put it on and did a test.  Then as I as changing it out for another prop, I was surprised how flexible it was and realized my error.  I dug the good prop out of my flight box where I had left it after some field testing and put that on and retested that😉  These numbers are using the Turnigy AE-45A ESC with custom settings of 22.5 degrees timing and 24 KHz of PWM (pulse width modulation) frequency on 3S.

"bad" prop results

50% throttle - 17.6A/216W producing 555 gr/19.6 oz of thrust;

100% throttle - 38.4A/434.3W producing 955 gr/33.7 oz of thrust.

"good" prop results

50% throttle - 15.2A/184.4W producing 585 gr/20.6 oz of thrust;

100% throttle - 36.7A/428.1W producing 1065 gr/37.6 oz of thrust.

I had always known that more flexible props were inefficient, but due to my error and having received on bad prop from Banggood, I am now able to see clearly the difference as these props are identical other than their stiffness.  It is fairly easy to see that the flex in the prop not only produces less thrust, but causes the system to work much harder by drawing more amps to produce this thrust.  Then as the throttle setting/RPM get higher, there is an even larger difference in results.

Over time as I have experimented with props, the stiffer the prop normally results in better power and efficiency as well as a prop that runs more quietly, but nice to see numbers that back that up😊

Park Jet noise...the "other" sound of freedom😎

Cheers,

Scott

Multistar Viking 2208 2600 Kv motor bench test session - 24 Feb 2018

Hi Everyone -

I did a bit more experimenting with testing the Multistar Viking 2208 2600 Kv motor today with a couple of different prop and ESC combos.  In bench and field testing, this has proven to be the most powerful quad racing motor under 2700 Kv that I have tested and in fact one of the most powerful overall.  It has reached 1000 or more gr of thrust with six different combos of props and ESCs on 3S, however one of them I probably would not use due to the quite high amp draw at full throttle.  It is one of the few quad racing motors that I have tested to show results that high at full throttle.

You can read the results of the testing on my motor test spreadsheet, by scrolling along the bottom, you will find the tab for this motor to see the results.  I have highlighted in light green the best setup for each ESC I have tested with thus far.  I did not test it with the HobbyWing Platinum PRO 40A with these props below as I have that dedicated right now to another plane and might never run this motor with that ESC.

Today I tested with the Turnigy Plush 40A ESC and Turnigy AE-45 ESCs using the 6x4 KMP and Master Airscrew 6x4x3 props.  You can find links to these ESCs and props on the spreadsheet.  The KMP has produced some very good numbers on the bench, I only have one of them right now, so I haven't done a lot of field comparison just yet.  I tested the Master Airscrew 6x4x3 prop as I had run that a lot on the DYS BE2208/7 2600 Kv motor a lot in the past, so I wanted to see how this motor made out with it.

So I saw some pretty decent results.  With the Plush ESC, the 6x4 KMP produced some good mid range and top end results, better on the bench than the 6x4 APC gas prop.  Although the MA 6x4x3 produced slightly better top end thrust, it's mid range results dropped off considerably compared to the other two props and I know from experience that third blade does cause some drag in the air.  So it would be a matter of field testing the 6x4 KMP and 6x4 APC gas to decide which was the better performer for my flying style.

With the Turnigy AE-45 using the custom settings I found of 22.5 degrees for timing and 24 KHz of PWM frequency, again the 6x4 KMP had very good bench results, significantly more top end thrust 65 gr/2.3 oz than the 6x4 APC gas, but slightly less (15 gr) mid range power.  Mid range efficiency is pretty much the same with both these props pulling the same number of amps.  At full throttle, the extra 65 gr of thrust required 0.8 more amps drawn, so not too bad.

With the AE-45 ESC, the MA 6x4x3 has good top end thrust, again over 1000 gr (1035), but comes at a big amp penalty, drawing 40.7A or 11% more amps than the KMP prop and produces less thrust, so I don't think I would use this prop with this ESC.  Hobby King rates this as a 39.1A motor, I personally think it could handle more than that, but if I have another prop that produces more thrust for less amps, I'll go with that all day.  As well, with a significant loss of mid range power (45 gr less than the 6x4 KMP), it makes that decision even easier😊

So I am thinking about using this motor on a project I am currently pondering for the near future, so good to know I have a couple of options of props to try out, I will probably at this point go with the Turnigy AE-45 and evaluate the 6x4 KMP or 6x4 APC gas.😀

Park Jet noise...the "other" sound of freedom😎

Cheers,

Scott

6x4 KMP prop from Banggood quality control issue

Hi Everyone -

This post isn't to whine about getting a dud product, it just happens sometimes, especially when trying to save $$$$😉  I just wanted to pass along something I discovered today when balancing one of the two 6x4 KMP props I recently received from Banggood.

I have been doing quite a bit of motor bench testing the last few days and have had some good results with this prop on a couple different motors, so I thought I would balance the second one to put in a plane to do some field testing.

As I started to balance it, the blade seemed to be quite flexible as I was handling the prop😲  So I gave it a bit of a flex and here is how flexible the one prop is...YIKES!!!

This is the prop I have been using for bench testing, I had to push on the hub with my finger to get it to bend this much and even then it was tough to bend😐 

So needless to say, I won't be using "Mr. flexy prop" in my plane😀  I have ordered some more from Banggood, just wanted to pass this along, before even bothering to balance them, just have a quick check you didn't get a bad prop like I did in this situation😒

Park Jet noise...the "other" sound of freedom😎

Cheers,

Scott

Thrust stand test session - EMAX RS2306 2750 Kv motor - 07 Feb 2018

Hi Everyone -

I had my thrust stand out today doing another round of testing, this time with the EMAX RS2306 2750 Kv motor which is by a narrow margin the most powerful quad racing motor I have tested thus far😊  It is the motor I have been running in my RC Powers T50 V5 for the last couple weeks.

Today, I tested this motor with the 6x4 APC gas prop, the Hobby King 6x4 APC style electric prop, and the 6x4 KMP prop from Banggood.  I tested each prop using the Turnigy Plush 40A ESC and then the HobbyWing Platinum PRO 40A ESC.  Some very interesting and also somewhat puzzling😕 results, but the numbers are what the numbers are.😉

All tests were done using the Gens Ace 2200 3S 45C battery.  The timing on the Turnigy Plush is at low (factory default), the HobbyWing ESC is set at 26.25 degrees and PWM (pulse width modulation frequency) is set at 8KHz.  These are not factory defaults, you can read more about my previous experimentation with the HobbyWing ESC in this blog post.

This motor definitely likes the HobbyWing ESC with the settings I have set, it has marked improvement at 50% and full throttle with all three props compared to their performance with the Turnigy Plush.😀

The overall best combination proved to be the 6x4 KMP prop with the HobbyWing ESC.  Numbers are below (you can also read the full details on my motor spreadsheet).

50% throttle - 18.3A/219.4W producing 635 gr/22.4 oz of thrust; and

100% throttle - 41.6A/482.7W producing 1120 gr/39.5 oz of thrust.

This is where it becomes a bit puzzling, as the numbers with the 6x4 APC electric knock off from Hobby King are nearly identical, same top end thrust, just 5 gr less at 50% throttle.  The 6x4 APC gas prop with the HobbyWing ESC produced 1075 gr/37.9 oz of thrust😕  Still decent numbers, but the 6x4 APC gas prop pulls 42.6A to produce less thrust in this situation, so a bit puzzling after the 6x4 APC gas prop performing so well for me to date.

Some of these amp number exceed 40, but this ESC has a 60A burst rating and normally, in the air the rule of thumb is that there will be about a 25% drop in amp draw, so 42.6A would become about 32A.  I will check the ESC regularly for heat build up.  According to the HobbyKing website, the EMAX RS2306 2750 Kv motor should be able to handle up to 58A if you click on the "Product Specifications" tab when you open the link to the motor.

The best prop with the Turnigy Plush ESC turned out again to be the 6x4 KMP prop, then the 6x4 APC electric, then the 6x4 APC gas.  So comparing my results with rcplanepirate's, the main difference is my stand tests in a "puller" configuration, perhaps in the air with a "pusher", the 6x4 APC electric won't perform as well or differently?  I certainly know from testing it with several other motors with the Plush ESC at the field, the 6x4 APC gas has proven to be a very good performer in the air.  Only one way to find out, so time to put the motor back in my T50, put the HobbyWing ESC in there and get it out to the field with all three props and see what is what😀  The 6x4 APC electric and 6x4 KMP are certainly louder than the 6x4 APC gas prop, so time for a "fly off"😉

Park Jet noise...the "other" sound of freedom😎

Cheers,

Scott

Thrust stand test session 2212/5T 2700 Kv motor - 05 Feb 2018

Hi Everyone -

I was busy with the thrust stand again today, testing a very inexpensive motor that I have run in many of my planes in the last couple years, the 2212/5T 2700 Kv, I got mine from Gear Best.

This type of motor is readily available all over the internet, I have seen several vendors on EBay and even purchased a couple from Banggood.  Unfortunately, the ones I got from Banggood ran extremely hot and pulled well in excess of 40A, so I don't know what happened there😒  It is quite a bit heavier than most of the quad racing motors I have been testing at 66 gr/2.3 oz and you must provide your own connectors and prop mounting adapter/collet, so that adds a bit to the price.  I buy my 3.17 mm adapters from RC Timer as they are inexpensive and pretty decent quality.

Rcplanepirate has done considerable testing with this motor and shot a couple of videos, you can find his YouTube channel here.

You can read the full details on my motor spreadsheet, I have created a new page just for this motor, along the bottom you can find the tab to click to take you to the page.

Today I tested three different props I have run on this motor in the past on 3S

• 6x4 APC gas;
• 6x4 APC style electric (Hobby King knock off); and
• 6x4 KMP (Banggood)

 I also experimented with two different ESCs that I have been comparing recently.

• Turnigy Plush 40A ESC (timing set to low (factory default) as this seems to work best);
• HobbyWing Platinum PRO 40A ESC (timing set at 26.25 degrees and running at 8HKz PWM frequency as this seems to be the best for higher Kv motors).  You can read more about how I found this out through experimentation at this blog post

This test session once again proved that I can never take anything for granted until I do the testing and see the numbers😐  I have been raving about the 6x4 APC gas prop for several months now being so much better than the 6x4 APC electric knock off from Hobby King and it has been both on the bench and in the air.  Well, the numbers were so much better at full throttle with the 6x4 APC style electric with the HobbyWing ESC, I had to do the test a second time to make sure I didn't do anything wrong😕

This motor produced significantly more thrust at full throttle with all three props using the HobbyWing ESC with the settings above.  The 6x4 KMP produced the most thrust at 1060 gr/37.4 oz of thrust, but drew 39.1A to do so, a bit high I think for this motor.  Where I really had to scratch my head is that the 6x4 APC gas prop produced 999 gr/35.2 oz of thrust drawing 35.6A, then the 6x4 APC style electric produced 1045 gr/36.9 oz of thrust and only drew 35.7A to do so!😲  This prop also produced the most mid range thrust with this ESC as you can see on the spreadsheet.

Using the Turnigy Plush ESC, the definite thrust winner is the 6x4 KMP at 1020 gr/36 oz drawing 35.7A which I think is in the ball park for this motor from my many flights even in warm weather.

I was actually surprised now that I tested them on an actual proper thrust stand that the 6x4 APC gas and 6x4 APC style electric were pretty much dead even in mid range and top end thrust.  Again, a real head scratcher, but some very good numbers for such an inexpensive motor.  Of course the HobbyWing ESC is not a cheap ESC, but I think it will be worth putting this motor in a plane with this ESC and the 6x4 APC style electric prop and see what happens since I have a couple😊

Park Jet noise...the "other" sound of freedom😎