Your comments and suggestions are, as always, cordially appreciated.

Matt,

Exactly what is your goal with all this? What are you trying to accomplish?

Charles

What Paul said.

Does the KR timer let you set the start-up interval?  Are they set to the same thing?  Might they have different software revisions?

The start-up delay is programmable using the programming stick and it is the same in both KR timers.
I can read the content of the hexadecimal code of each of my many KR timers so when the same hex number is in the same place they use the same decimal number.

Do you mean you've checked the code space, and the software is identical in each?

I'd try Paul's suggestion to swap the timers fore & aft; see if that makes the problem switch.

It seems that I have found the solution to the problem.
I will verify the idea in flight and publish the results, if they are satisfactory, on this forum.

Next step: I am looking for everybody who flies stunt with models having two electric motors in any configuration and Keith Renecle, Rogerio Fiorotti or Igor Burger timers.

M

Matt. I do not know where is exactly your problem, except for Keith timer all normally work with several ESCs. Reason is clear and explained by Tim.

I think you know my facebook page where I published how to connect my active timer with Spin ESC with only one switch (so it does not need modiffication of switches to start them together) as those switches handle only 5V for timers. So that ESC switch will nicely handle start - stop of timers.

You can ask some of your polish friends, several of them do or want to use contraprops with my timer and two spins44. Also Pavlo k
K. makes and uses his contraprops in the same configuration. Did not you see it?

Here is his solution:
https://www.facebook.com/permalink.php?story_fbid=1302226776622090&id=363984487112995

and here is how to do it on wires level:
https://www.facebook.com/permalink.php?story_fbid=1346574585520642&id=363984487112995


If the question is why those timer do not work EXACTLY in time (IF programmed with identical values) ... the answer can be that also mine and as far as I know also KR (I do not want speak for Keith) use RC oscillator in PIC chip. So they are not exact like quarz oscillators. Normally they are nicely calibrated, but still, there can be some difference. It does not play role if there is only one timer, because if you fly 2 seconds longer or shorter does not matter. Im portant that it is repeatable. I can manage motor stop on place of circle where I want in respect to wind for example (with help of beeping watches in pocket).

But one note here ... that calibration value is stored to chip by hex programmer, are you sure that you did not delete that value in chip while you played with firmware? It could easily happen. Actually it needs special behavior of programer NOT to delete it (it must read it, store, do wanted operations and on end store it back - if programmer fails during that, calibration is lost).

Friends,

I made a video where it shows the synchronism of the ESCīs in two engine systems.

Two low cost motors were used, 10x5 3 blades Graupner - ESC Castle MultiRotor - power supply set to 4S and my timer v6.4 with differential RMP adjustment between motors.

Matt found problems using ESCīs Cobra on my system but with ESCīs Castle and Jeti they work very well.

Just remembering ... ESC Castle MultiRotor are not recommended for F2B your brake system is momentary.





Rogerio.

The report from the (battle) field:
I have made three 4 minutes flights with eParrot having Himax contra, two Cobra 40+ ESCs, one KR timer and 4S 3000 20C Zippy battery.

I like the way the model flies: it is evident right now that wind (10 km./h with rapid gusts reaching about 20 km/h) affects the model's speed in maneuvers MUCH LESS than in case of flying the same model with one motor, one prop. power plant.

This is exactly what Krystian Borzecki (PL) told me:"...contra will maintain ALMOST steady speed in maneuvers no matter WHICH way the model is flying and the model with contra is LESS sensitive to the wind and wind gusts.."

During flights today, I have confirmed that both motors constituting the Himax contra started at the same time (after 35 seconds start-up delay). The warning on both motors was clearly audible, at the same time and BOTH motors stopped at the same time in the air.

I have also confirmed that the contra power plant uses less battery than a single motor, single propeller configuration in the same model performing the same maneuvers. In eParrot's case it was 15-17% less. This single finding is very valuable as somebody flying a well trimmed electric stunt plane with contra can use the LiPo batteries having smaller capacity, therefore lighter or/and easier to get in many countries.  It is also worthwhile to mention the price: the best Polish contra fliers use 2300-2530 mAh. GenuACE (3S+3S=6S) and Revoletrix (6S) to power full size, competition F2B models and the cost of these batteries is about 60% of the cost of 6S 2800 25C ThunderPower ProLite.

During today's eParrot flights, I have also noticed something else.... Namely, the level flight RPM of Himax motors were not REASONABLY stable. I did not expect perfection but it was clearly audible that RPM were going SLIGHTLY up and down in a periodic fashion. I do not know what was the amplitude of these fluctuations but the period was rather low: around 0.5 -1 second. 

Keith Renecle suspects that "...the rear (Himax) motor has no feedback to the timer so it is simply getting commands from the single timer without any negative feedback control loop.." and this is certainly possible.
How to get rid of these RPM fluctuations while using one KRG and two Cobra 60+ ESCs? I do not know at this moment but I will keep experimenting and flying eParrot. 

I know...I know...The easy solution is to buy two Spin 44 or/and some Castle Creation ESCs and use either Igor's or Rogerio's active timers with contra but, without all these tests I have done, I would not know this what I know now.

Stay Safe and Happy (contra) flying.
M

Your energy savings is similar with boats using stator struts and contra propellers.  It has been years since I read on this so I cannot cite books, but there are many regarding yacht and working boat designs.  Contra rotation effectively removes twist from the fluid flow regaining losses.

Phil

Hello,
After testing and testing and more testing, I have found the following:
1. Keith Renecle timers (KRG) do not work CORRECTLY with two Cobra ESCs and two motors in any configuration. "Two motors" mean either two separate motors or Himax 3516-1030 motors.
    By correctly I mean:
                       a. reasonably stable RPM of BOTH motors during the flight time
                       b. Both motors start and stop at the same time
                       c. The warning at the end of the test/flight is present.
For those who never used KRG: warning is a sequence of RPM at the end of the flight. First, the RPM drops slightly for about 2 seconds, and then RPM increase for about 3-4 seconds and the motor stops.
                       d. The hard brakes applied by the programming of the Cobra ESCs is REPEATEDLY active in each test
                       e. It is possible to use the programming stick that comes with the KRG to change RPM, flight time, start-up delay and gain.

It is possible, though, that KRG will work CORRECTLY in two motors configuration with the ESCs having the governor function, modes etc. I have still only one such ESC (Spin 66 F2B) and could not test KRG with them.

By the way: during my yesterday's conversation with Igor Burger, I suggested using SpinXX F2B instead of SpinXX "old style" for the family of the Jeti Spins with fast reaction time, used almost exclusively in the EU for F2B. We will see if the new name sticks.

Fiorotti's active timer works a little better with two Cobra ESCs hooked up to this timer channel1 in parallel and two motors but the RPM, current, power, and voltage are slowly dropping during one-minute tests. Again, Cobra ESCs do not have the governor function, needed to stabilize the test/flight parameters. I will test the Fiorotti's timer with Spin44 PRO very soon.

By the way: Spin44PRO has the reaction time (for the accelerometer input) longer than Spin44 F2B. Igor tested Spin44PRO some time ago and this time is six times longer than for Spin44 F2B.
It probably does not matter too much for the intermediate stunt flyers but the top competitors must perform very sharp corners with almost instantaneous power boost and then the ESC reaction time matters.

Igor's active timer does not work with two Cobra ESCs at all.

Final conclusion: Cobra ESCs work reasonably well in the single KRG, single ESC, and single motor configuration. I am currently flying three stunt models having such configuration and everything works correctly.

Your comments and questions are appreciated,
Stay Safe, Fly Safely and Down with The Virus,
M
 

1. Keith Renecle timers (KRG) do not work CORRECTLY with two Cobra ESCs and two motors in any configuration. "Two motors" mean either two separate motors or Himax 3516-1030 motors.

I cannot speak for Keith, but I know how that timer works and I am not sure what you exactly tested. I do not see reason why TWO his timers on TWO simple ESCs on TWO motors shout not work. Are you speaking about such combination? Or one timer and two escs?

Hello again.
The time has come to fine-tune the Fiorotti's active timer with two Jeti Spin 44 PRO and Himax 3516-1030 contra.
Rogerio, in his C/L TIMER V.6.X manual, gave some numerical examples that allow for the initial setup. Specifically, he is showing the sequence of consecutive images of the JetiBox displays.

What I am looking for at this moment are four parameters in the case when two Jeti Spin 44 PRO are used:

1.  (RPM ESC1) Engine RPM - For Jeti Spin ESC RPM=230 is recommended - confirmation required.
2.  (RPM Max) Maximum RPM - numbers needed
3.  (RPM Min) Minimum RPM - numbers needed
4.  (RPM ESC2) 2nd Engine RPM - numbers needed

The limiting current for Himax 3516-1030 is 36 Amps. I was and will be using 11x5x3 Igor carbon F2B propeller and 12x6 Polprop or 11x5.5 APC E or/ and two 11x5.5 APC (left and right). The battery is 4S.
For the purpose of the initial testing, I may also use smaller counter-rotating propellers, like 9x6 APC E.

The last thing I need is to set one of the above-listed parameters in a wrong way and burn something while testing on the rig. 

Hi again, Igor,
In your response dated June 19, 2020, you have stated: " I do not see reason why TWO his timers on TWO simple ESCs on TWO motors shout not work ".

I have tested this configuration many times and even made several flights with eParrot equipped with two KRGs, two Cobra 40+ESCs, Himax 3516-1030 and 11x5x3 and 12x6 carbon composite propellers.
The maximum flight time was set to be 3 minutes and 40 seconds, mostly level flight, two or three lazy and very large loops and some inverted. At that time (May 21 and 22), I have used 3S 4000 mAh 25C battery. The plane was flying too slowly and was lethargic. The start-up, flight, and landing sequence looked as follows:
1. Battery connected and both motors beeped
2. One common sliding switch was moved into the ON position and both props. flipped simultaneously
3. I walked to the handle
4. ONLY one motor started after the start-up delay expired (35 seconds in BOTH KRGs) - the plane began rolling
5. In 2-3 seconds, the second motor started
6. The plane took off
7. After the flight time programmed into BOTH KRGs (3 minutes and 40 seconds), ONLY one motor gave the warning and stopped with hard brake
8. The other motor kept running with low RPM (unknown but allowing for slow level flight) and stopped after the measured flight time was approaching 5 minutes (!!!)

After this experience, I have decided to test only on the ground and this is what I was doing for the next month.

My conclusion (again and after many, eLogger documented, tests): there must be something in a way two Cobra 40+/60+ Amps. ESCs work with two or one KRG that makes this circuit inherently unstable.
                                                                                                           I will limit the use of KRG to a single motor and single ESC configuration in which KRG works well.
                                                                                                           
Like I wrote on June 19, 2020: it is possible, though, that KRG will work CORRECTLY in the two motors configuration with the ESCs having the governor function, modes, etc.

Thank you,
M