P68C Advice

[phild]

I was talking about the wire that cums from the esc to the receiver the three small wires if you leave both sets connected you will get power from both esc's going to the receiver which is not a good thing, so by removing the red plug from one of the esc cables you only get one power input to the receiver. If your are intending to use a y lead you may wish to remove a red wire on one arm of that which will give the same effect.
You then have to decide if you are going to extend the battery lead from the esc to the battery which I assume you will be keeping in the fuselage, or extend the three main wires that run from the esc to the motor, and keep the esc's in the fuselage rather than in the nasals behind the motors.
There has been allot said about this but I believe that extending the battery leads is a better idea. Before ordering your motors just check that you will have room for them and the esc in the nasals, you may need to do a bit of cutting to get it all in.
Phil

[Gareth]

Mike,

There is lots of information online. I have had a minute to search and found a couple of pages that might be of interest.

http://www.westbourne-model.co.uk/hints-and-tips-for-model-boats-4118-0.html
http://www.rcgroups.com/forums/showthread.php?t=1211763

The way that i worked mine was to add a servo extension lead to each ESC and remove the red wire from one of the extensions, that ensures that the ESC doesn't get damaged in any way and will allow you to use them in other projects. On that model i would also look at getting a Y-lead. What you will have is:

                         Extension with red pin removed - ESC - Motor 1
RX - Y-Lead -<
                         Extension with red pin in place - ESC - Motor 2

Hope this helps, I can probably get a diagram drawn up if that would help.

Gareth

[Tim Marshall]

I have never been able to understand that suggestion though I have seen it offfered several times.  If each ESC outputs 5v and they are wired in parallel the voltage is still 5v ;  surely it is just like having 2 cells 1.2 v, in parallel 1.2v  but put them in series and you get 2.4v??

[Dave]

Unsure why you would tinker with the ESC, please expand.
Simple Y harness and split the input power to the ESCs
Simple Y harness and split the ESC Signal/BEC voltage regulator signal to the RX

IF the total BEC power consumption (servos and other devices requiring  5 VDC) is within the rating of ONE of the two ESCs you will not have to tinker with isolating the 2nd ESC BEC

Your servos are most likely HS55 or something close to it and have min. current draw
The ESC BEC that outputs the highest voltage will be the dominant voltage regulator for your servos; the other ESC BEC will be sitting on its duff doing very little or nothing.
Fly twin combos this way and never had an issue friend

 

[Gareth]

I thought through reading all the other posts that if you have the 2 reds connected it will blow the ESC's up. Both are expecting to deliver power not receive it.

I don't know if you can run 2 ESC's at the same time, that would provide a little security as one would be redundant. I would have a chat with BRC and ask the question, it doesn't hurt to ask.

Gareth

[Dave]

This may help...
 

[Mike S]

Thanks dave that looks good.

Once question I know all this can be found on google but to connect the esu servo plugs to the rx I imagine you use a y cable?

[Dave]

I typically custom make my Y harness, length to fit, I also make a custom power Y harness.
In the PBY the ESCs are located in each of the Engine nacelles just aft of the motor
The ESC connections are all located within the nacelle for ease of maintenance.
I had them in the fuselage at one time but I played hell disconnecting them when the ESCs got wet.


BEC SHARING
If the ESC BEC voltage unbalance makes you nervous, add a couple low resistance value resistors to the circuit to balance/load share between the ESC voltage regulators.
Adding the resistors will get the lower voltage output regulator off its duff and increase I total.
(See detail area in green)


SIDE NOTE
All shield terminations should terminate to ground at a common ground node
All shields are floating (noise suppression)

a schematic of my config.

 

[Mike S]

Right had some time today to take the motors and escs out of the bags for the plane. Escs are 25amps and the motors are 140watts.

Now have I got this right:

Phil suggested a 7x5 prop for best setup and as per the instructions:

6x5.5 APc-E prop suggested amps 10 on a 3s lipo giving 120 watts.

7x5 APC-E prop suggested amps 14 on a 3s lipo giving 170 watts for max power.

Brc said as suggested to use a Y lead and disable one red wires otherwise one of the escs will shut down during use.

[phild]

I would go for the 7X5 you don't have to use it flat out, but you will have the power if you need it. The Y lead will work fine. you pays your money and takes you chance when deciding to pull one of the red wires, this was discussed earlier, but if it was me I would pull one on the y lead, it wont do any harm and may prevent one of the motors stopping prematurely.

Phil

[Mike S]

Thanks Phil...

Phil you suggested using ply to beef up the motor mounts. What width ply for this as i can not remember what you suggested at the HW compo.

[phild]

Try the power set against what you have to see if the motor fits. then beef up accordingly. 1/8in ply will be enough, but see what you need to do to get the motor to fit the cowling.
Phil

[Mike S]

Cheers Phil.

I will have a look at it over the next week as busy will course work etc

[Mike S]

Right u orible lot....

I have given myself today to look at the wings and options for fitting the esc's and motors.

The firewall is thin so I may need to beef it a little and to fit the esc's in to the nacelles is an idea but not sure if the esc's will get hot in there?.

The motors will need a ply box built around the current engine mounts to meet the nacelles

[phild]

As long as you have ventilation holes in the nacelle you shouldn't have a problem with overheating, you shouldn't be over taxing the esc with what you are running off it. One difficulty I found with the DC3 was threading the wire from the esc to the receiver threw the wing. You will probably find that the wing was built around the power lead, and any other wire you have in it. I know that this is not a particularly good solution but if you are having difficulty threading the esc lead consider running it on the underside of the wing. This would be preferable to smashing wing ribs when attempting to pull the wire threw.
Phil