in a twin EDF RC PLANE ,what can cause one edf to produce less thrust than the oyher unit even though the units are identical. they have the same motors, the ESC and the same batteries
mma

mayoub
The first question what is the plane?
Have the EDFs always done this or has it developed recently which would suggest something has changed. Is a fan damaged?
Next can you tell if both EDFs are going at the same speed - they should make the same pitch noise or even produce a 'beat' when running together. If they are running at the same speed then it there is likely to be some sort of obstruction in one duct.
If the fans are running at different speeds then it is possible that one of the ESCs is not registering your TX full throttle position correctly. Some EScs have be 'taught' the full throttle position.

the plane is an me 262. the fans, the ESC's are new and the plane has not flown yet. I have ran the motors and just suspect that the thrust is not equal( no measurement is made) I am asking the question in case I CONFIRM SOME DIFFERENCES then I have some ideas where to look to make any corrections. the batteries are placed forward in the fuse and the ESC's are close to the leading edge of the wing( somewhat long wires between them). no obstruction in the ducts. A far as I know the the throttle position was learned but this can be checked again. Thanks for you response.

Mayoub,

If you are using a Y harness for the ESC's, try running them one at a time and see if they run up to the same sound and thrust. This should tell you if you have a problem with one of the fans. If you have them on different channels, make sure the end points are exactly the same. Maybe try a Y-harness plugged into the throttle channel.
Also, Make SURE you have cut one of the red wires on one of the ESC leads to the receiver. I use a short servo extension and cut the red wire out and use this for one of the ESC's. The BEC's may be causing interference on the throttle channel.
As a last resort, re-learn the throttle position with 1 ESC plugged in at a time.

Hope this helps,
Keith

thanks for your response. I will try to run each fan seperately and see if I notice any differences. I should mention that I am not using a BEC. I am using a seperate battery for the RX.
mma

Most ESC's unless they are high voltage ones have an internal BEC. If the ESC's have BEC's you need to disable both BEC's by removing the red wires if you are using a separate battery for the receiver. If your not sure if the ESC's have BEC's, power up one motor and don't plug in your receiver battery. If receiver powers up ESC has a BEC. Sorry to be a PITA but I have witnessed this same issue before and it was cured by eliminating one or both of the red wires.

With your model having motors so well apart, you try to get them to run as evenly as possible to avoid assimetrical thrust. No motor or ESC would be perfectly identical especially cheap stuff from asia, but most like reason for your power difference is in your batteries if all the leads are identical. I fly number of EDFs ranging from twin to triple motors but having the power units pretty close to the centre line it doesn't create any problem beside the difference in sound, mainly when I fly my "Mig-29" which might be also caused by the long term wear and tear after over 250 flights.

Unless the difference is substantial you are probably worrying unnecessarily - especially if you have a rudder. After all the full size could fly (just) on one.
Where you would be in trouble (again just like full size) is if one actually failed just after take off!

My EE Canberra with cheap EDFs and ESCs has no problem.

And its just 'bank and yank' (no rudder)!

Thanks for your comments. As I mentioned in an earlier statement I have not act checked them yet but I am trying to find out all possible causes of uneven thrust. All components in the plane are good quality so I may not have any significant thrust difference but I know that motors may not have identical specs because of manufacturing variations. Thanks again for your thoughts.

The issue of internal BEC's is a very important one as most these days are switchmode, and if you leave them connected in parallel with each other one will kill the other, switching circuits do not like to be run in parallel. As mentioned remove the red wires from each ESC lead, NOT from the Y lead.
Connect each ESC individually to your Rx and do the throttle range setting, IE throttle full, Tx on, plug in battery, ESC will beep, close throttle, ESC should count cells then arm, throttle range end points are now set to your Tx. Do same to other one then reconnect to Y lead, should be close to each other unless something is wrong with motor Kv or one ESC has an issue.

thanks for your comments about the BEC. I am not running a BEC . The RX has its own battery supply independent from the ESC's BET which I do not have with these ESC's.As far as learning the throttle positions for each fan separately, I will do that as soon as I receive the tach bought so I can at the same time check the rpm for each fan to see if there are any significant difference. Thanks again