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Selecting ESC for 8 Servo Glider


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Hello! I'm concerned about the load (Amps) requirement on a ESC for a glider (The Insside) that has 6 wing servos plus Rudder and Elevator. The 20A ESC recomended by the Hacker motor has a limit for about 2 servos, the model recomends 30 to 40 A ESC. I can only find a recomendation for up to 6 servos even at 45 Amp ESC. Can anyone advise what ESC would be minimum and how this may effect the motor / Lipo selection and performance please.

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I'd run a separate battery for the RX and all servo's, I usually use a 2s lipo either direct for HV servo's or with a separate Ubec/ BEC/ voltage dropper for non HV servo's. I wouldn't use the esc to power 8 servo's.

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Thanks guys, its looking like I need to spec a separate power supply then and find space for more battery's and balance the lot for cofg. Thanks for that. Pete

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PeteMitchell
3 hours ago, petespencer said:

 Can anyone advise what ESC would be minimum and how this may effect the motor / Lipo selection and performance please.

 

 

The size of an esc has no effect on motor or lipo selection unless its maximum Amp rating is lower than what the motor is likely to draw. Any size lipo will work provided it’s ‘C ‘rating is compatible with the max current the motor is likely to draw. Rule of thumb is bigger is better because it will deliver more power if you need it and it will last longer because it is less stressed.

When thermal soaring the total Amp draw is quite low. I have measured 6 servos total draw as below 2Amp and that’s with every stick being moved constantly.  Something like ‘Crow Breaking’ where servos are held at full travel for some length of time can double the draw or maybe even more.

If you are using modern micro servo’s, 8 servo’s will not use much more current but it would be safest to use a quality Esc that can supply 6Amp BEC something like this

https://www.hyperflight.co.uk/products.asp?code=YGE-35LVT&name=yge-35-lvt-esc

Hope that helps.

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Thanks Pete, thats a very expensive ESC though to me, would a Sunrise 45A with 6A Sbec do the job at half the cost do you think. Thanks pete.

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PeteMitchell

No experience of the Sunrise esc, but looking at the spec. it looks like it would do the job for you.

Worth checking that it can be programmed  with motor braking  as that's not clear in the ad.

Also check what room you have in the fus of your model, to make sure it will fit and that you can balance the model.

 

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I recently finished my "Inside F5J".  I had exactly the same problem in sourcing a suitable power supply for it.  It runs on 3S battery, so needs a suitable BEC, the kit manufacturer specifies a 6A BEC.    

Initially, I looked for a small enough (30A) ESC with combined BEC/UBEC that could manage that BEC output but found that they seem to only exist in the high spec brands (Castle etc.)..  IIRC there may have been one in the YEP range.  

In the end I gave up in order to make progress and fitted a separate UBEC.  I am looking at fitting a separate ESC (an OPTO version) to all my F5J gliders and run the Rx and servos on a separate UBEC/SBEC.     The ESC that suits my needs is a BLHELI_32 version. The "32" version is important as this gives a choice of several motor braking strengths.  They are suspiciously small. A tiny 30A is used in my 2M gliders without any problems.   

This then allows for a choice of UBECs. there are a few out there that will do a good job.   My Inside F5J uses a ZTW 6-10A UBEC. It works very well and is more than powerful enough for my setup.    At the moment I still have a regular ESC/BEC  running the motor, I just disconnected the BEC.    When I get to grips with configuring the BLHELI_32, I will pop one of those in.  

The use of digital servos will make the choice of BEC more critical.    Whilst I was playing with my collection of BECs on the bench. I found that many just didn't make their claimed output.   I was alarmed to find that, whilst a linear BEC's output voltage reduced with increasing load (and whilst getting hot), the UBECs that I played with all simply shut down when overloaded...and not always at their specified loading. They will not restart without a power off/on cycle.  Scared me!    

Incidentally, I have just got back from a session flying the Inside.  It went very nicely.       

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Pete, thanks for feedback on sunrise.

Dave thanks for you insight and experience with the Inside.

I thought I was almost there! Now I'm not sure....

So I guess I need a separate s or ubec for receiver and digital servos to run sbus to wings and separate ESC for motor all run by two separate batteries.

Just to make it worse not all parts on the shelf do what they say they will do.

I'm guessing the top models pay out for top range components while those of us doing it on a budget try to spec the less expensive and possibly more dubious components. Its a balancing act on model security too... Mmmm..

Will do some more research and look into the components you mentioned Dave thanks.

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To be fair to the manufacturers of BEC/UBECs,  it's my experience that their ratings are based on the max transient output and not on the continuous output. This makes measurements difficult.    If you were to measure the the static current draw on your BEC, it will be quite low, getting higher as you move the surfaces and higher still when those surfaces are loaded.   The continuous and transient requirements of digital servos tend to be higher than analogue servos, so a little extra may be called for.       

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The 10a Castle creations bec is a good option as it is small, can be powered from a small 2s Lipo and you can even choose what output voltage you want from it. I use them in F5B gliders and especially in some where I have LV servos. 10A is overkill and allows a good margin of safety, which also means you can get away with a lower spec or cheaper esc, If the esc fails you don't then lose the whole plane. 

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There are, as always, many ways to skin a cat so your options are wide. I fly F5J and regularly take part in competitions so my solution is proven over the last 18 months.

I have been using an a separate esc and sbec:- the esc is a 65amp Hollybro Tekko32 running the BLheli32 firmware. These are very small and thin devices that take up hardly any space. I then use a general purpose sbec to run the receiver and servos. I run both from the main battery. My logic is that the esc will shut the motor down when there is more than enough left to operate the servos.

The Tekko32 is a great little unit but it is a fiddly job to get set up in the first instance but once done it’s worthwhile.

There is a thread on here written by Colin Paddon in which he details the whole process of using a BLheli based esc’s. It’s well worth the read. The the thread was titled “UPDATED - THE FUTURE OF ESC’s for F5J ?” In September 2019.

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Dave Kyri, Feefo, Gem. Thanks for all that info and detail. I think I know where I'm heading now. Will also look at the thread mentioned thanks all.

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