I am building an F-14 with two fans and I have a small problem.

I have connected the two fans into the receiver with an Y-cable. When I started them up for the first time one of them is starting a bit after the first one.
I read the instructions in the ESC manual and completed the throttle range settings as described in the manual.

The first start after this range setting both the fans seemed to start at the same time. I throttled down again but then when I for the second time put some throttle it was back to how it was the first time; one is starting before the other, and of course then one is stopping before the other when I throttle all the way back.

I have not yet put the bottom cover on the F-14 and not test flown it but i guess the unsyncrohnized fans would cause a bit yaw tendency even that it is just the difference of one small step on the thottle (Futaba 7C).

Any ideas?

Thank you in advance!

Best regards Knut

You sound like you want perfection.

You will probably not get perfection.

If they sound close at 1/2 thru full throttle ,, be very happy.

Everything would have to be perfect & identical for what you want. Not going to happen at low throttles & idle. We have no trims in models.

Enjoy.

You need to pull the red wire from one of the ESC connectors into the Y harness. Right now they will create a feedback loop and cause difference in throttles that change all the time. I actually recommend that you plug each ESC into a different receiver channel and use a mix. You still will need to disconnect one of the red wires. You can unclip the lead in the plastic plug and push it out and then I usually shring wrap it back to the cable so if I want I can replace it if I use that ESC in a single motor configuration in the future.

I have twin EDF's on 1 BEC & still get the slight difference at start & stop. I tried different ESC's ......You name it swapping. It does not synchronize at the low throttle setting.

Not important, as there is 0 thrust there. You are gliding or on the ground.

With a BEC both ESC's red wires should be disconnected so you don't get feedback.

I have several multi engined planes, brush & brushless. All are in tune from 1/8 of throttle up to WOT.
None start & stop together at very low speeds. Look at all the stuff twin gas guys are using to try and synch the engines. We have, 0, to adjust each idle speed independantly.

I don't have twin synch on any of my glow or gas planes..... I have 3 at this time...

You have out done me. I have no wet planes.

Thank you all for your answers!

I got two ExtremeRC Lightning 40A ESC UBEC linear ( ESC and UBEC together, not seperate) but I guess it will be the same procedure for this ESC as well (pull one red wire out of one ESC). (It is the first time I am building an electric twin so excuse me for possible stupid questions...)

Thank you!

Best regards Knut

I would buy a short servo extension cable, about 6" maximun. CUT THE RED WIRE IN IT. Now you have no risk to the other ESC's pins or UBEC's cable or pins. This is a standard way to deal with the 2 electronics units fighting each other. 1 UBEC SHOULD be more than enough for most normal sport planes and their servos.

You do mention they are LINEAR ? They MAY not handle a bunch of servos. Could you post the data sheets of the ESC & UBEC ratings ? Then we could tell you more accuratly how many of the actual servos in your plane it can handle...........Some BEC's are VERY limited.

Post back. Get the BEC too small and crashs do occur from that.

Rich

The 40A ESC now has a switching BEC but this is the spec from the 30A linear BEC....

This model features an advanced LINEAR BEC circuit able to provide 2A/5V to power your servos while running up to 4 cell Lipo packs.
2A is not mich.....

Also this note is on their web page....

NOTE: When connecting 2 or more LIGHTNING ESC’s with switch mode BEC’s together you MUST disable the BEC on one of the ESC’s. To disable the BEC you simply pull the red wire out of one of the servo leads then insulate it. Once you have done this, you may then connect the ESC’s together using a Y harness.

Failure to isolate all but one Switch mode BEC will damage one or both of the ESC’s. EXTREME RC is not responsible for damaged ESC’s that are wired incorrectly.

The spesification on the ExtremeRC Lightning ESC 40A (Linear BEC mode) UBEC, 5V/3A, 2-5 cell Lipos (I will use 4 cell). I will have 4 servos on the plane (2 x aileron, 2 x elevator).

If you have the 5v/3a version you are PROBABLY good. Make very sure all the servos linkages, can rotate freely into all the stops in the servo. If they can not and you do a long stick command at the end of travel, it will overload the switching BEC and shut down till it cools off enough. I noticed where they stated the throttle trim was available. Send them a E-Mail about yours not holding your adjustment after programming it with a PG card.

You are now a qualified multi engine builder.

Great news about the seperate engine starts!!!!!!

Real planes ONLY start 1 at a time !!

Start 1 engine. Wait 10 seconds. Start the next one. Enjoy

Viper ... I have got that problem before. Its not about perfection. Sometimes cheaper ESCs cause this. One will start quite a bit later, not about 1-2 clicks only. The power and RPM is also not the same. We had this problem with some El Cheapo China ESCs and I was going nuts trying to figure it out for my pal. Later, we changed to branded ESCs and it was a matter of 1 click only. Power was pretty equal.

Thanks tIANci.

I only use GWS & BP Hobbies ESC's & never have had more than 1 or 2 clicks on the trim lever to start both. I like the delay now. A-10 sounds a lot better with a delay. By 1/8 throttle they are synched.

Thank you all for your answers!! I have now set the throttle range once again and then removed the red wire from one ESC before i connected it again in a y cable.

It seems to work fine now!

I got another "problem" though... I have glued it all together and when i move the elevators sometimes the servos are shaking.. and you have to move the stick to make it stop...


I have attatched a picture of the Tomcat.

Do you have these on a Y also? You may need to plug them into seperate channels and use a mix. What servos?

I have these in seperate channels and mixed them. The servos are Vigor VTS-05B.

It may be that you need better servos. $4 servos.

Operating Voltage: 4.8-6.0V
Stall Torque: 0.6 kg.com (8.4 oz/in) at 4.8V
Operating Speed: 4.8V: 0.09 sec/ 60?
Weight: 8.0g (0.28 oz)
Size 22.5 x 12.8 x 23.7 mm

Very low stall torque, your full flying stab (elevators) will need a higher torque servo. I would recommend somewhere around 1kg minimum.

These have worked well for me in this price range. I use them for small foamies.

http://www.unitedhobbies.com/UNITEDH...ec_Micro_Servo

What kit F14 is this?

Thanks!

It is the EPF kit. www.epf.com.tw

Though they say >1kg torque servos this thing is big 48" / 1223mm span... I think even bigger servos would be a good idea...

I to am doing my first "flying stabilizers". I have found the below charts to be very reliable.

1 kg should do very well. These surfaces SHOULD be balanced pretty close to a neutral load condition. Mine are. I checked them out with a LARGE high speed exhaust fan at a factory with a wind guage. I am using HS-55's . No joke. I did my own support system.

Do MILD dives at steeper & steeper angles to prove out your servos can do the job. Do not get carried away with the steep dives. Plane was not designed for them.

The jiggling servo or is it servos ? If only the 1. It may be a tight spot in the stabilizers travel. If it is ALWAYS in the same angle, it is a bind. Remove it somehow. You can have SEVERAL binds on ANY moving surface. Your hinges should allow the surface to move easily with a gentile puff of your breath.
I hope you DO NOT have ANY metal to metal linkages. Like a metal adjustable clevis to a metal control horn. OR loose bolts & nuts. They can cause small to very wild servo movements. DO NOT test the controls of any plane indoors. Metal beams, roofing, or siding will sometimes cause erattic servo & or motor operation. I have had ESC's go from stopped to any amount of speed the reflections inside the building could create. 1 plane almost got me in the belly......Outside only.

Sorry if you know all this already. Tell me so I do not keep going on. I do not know your abilites.