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Member postings for Nigel R

Here is a list of all the postings Nigel R has made in our forums. Click on a thread name to jump to the thread.

Thread: Best DV11 plan
09/01/2020 13:08:38

albatross or fokker?

Thread: AR 410 Spektrum reciever
09/01/2020 13:07:10

The DX6i is either DSMX or DSMX/DSM2 depending on how old it is.

Either way, the RX should be perfectly OK.

Thread: battery c rating
09/01/2020 10:14:15
Posted by Keith Miles 2 on 09/01/2020 00:57:20:

point out where at least two of us have misunderstood the theory, at least one of whom is a retired electrician.

If the motor is right on the button with a low C battery, a high C battery can supply slightly more current and slightly higher voltage, perhaps enough to push the motor over the edge.

It's a contrived case, granted, but correct.

Thread: Do you remove your lipo from your transmitter every time?.
09/01/2020 09:44:39
Posted by Robert Welford on 08/01/2020 21:16:42:

Why do you use a lipo in a transmitter?

The current requirement of 2.4 Ghz is so low. Application better suited low to discharge Nimh, or Lithium ion.

My transmitters last days on a single charge.

I use the battery and charger that came with the TX (Spektrum DX). Its a "Li-Ion" of a long life / low C variety.

It seems to last for a good long while on a single charge.

In a DX6i, I have nimh cells.

Thread: ESC overheating.
09/01/2020 09:32:37

"And current x voltage IS watts"

Not when dealing with AC inductive and/or capacitive loads.

09/01/2020 09:31:58

"By the way, hardly any of my esc`s have any cooling airflow whatsoever due to restrictions imposed by the models"

You are asking for trouble, taking that approach.

Thread: Dereck Woodward Bigga Bit
09/01/2020 09:16:39

Thanks for thoughts on the rear fuselage.

I feel unsure the 3mm liteply will crack and bend quite as easily as balsa would. The other thought that occurred is that the rear fuselage probably doesn't need to be a slab of liteply for strength, and it is weight in the wrong place, so I'd probably be looking at cutting big holes in it. The front section probably does need a bit of ply type stuff - it is mopping up any and all reinforcement needed for firewall, U/C, wing bolts/pegs and servo mounts.

Having looked at the Bubbles plan on Outerzone it seems DW used two separate sections, the usual front parallel box, and the rear taper part, simply glued together with some reinforcement around the joint. If I did that I could just use some 3/32 to make the rear sides. Hmm...

08/01/2020 23:17:15

Nice and bright!

I'm half tempted to fit a glow in the front smiley

20200108_224744.jpg

I made some foamboard tips and elevens. Both are edged with 3/16.

They're stiff enough but the foamboard isn't that tidy. I'm not sure I'll use it again. It would have been quicker to cut from sheet balsa.

Thread: Propeller alternative chart
08/01/2020 14:19:14

In the 12" region, the 2" pitch for 1" diameter works out about right.

Might be different for other sizes.

You can easily use a prop power calculator to figure an equivalent load of different diameter. Plug in the original prop and rpm, note power, then play with prop size.

http://godolloairport.hu/calc/strc_eng/index.htm

Thread: ESC overheating.
08/01/2020 14:16:41
Posted by Alan Gorham_ on 08/01/2020 12:55:54:

That is not strictly true for every ESC as there are dedicated BLDC commutation IC's available that allow workload to be taken away from the Microcontroller.

What sort of ESCs are using separate ICs for the commutation?

Just intrigued, as it seems a relatively well solved problem in ESC software.

It would seem tough to avoid having a cheap and cheerful CPU, as it can mop up the other tasks of servo control input decoding and dealing with storing/applying the various settings within the ESC.

08/01/2020 12:51:41

Indeed so. Ensure they receive reasonable airflow, problem solved.

08/01/2020 12:49:52

Theoretically, you could have linear control of a brushless ESC. It would add pointless complexity to the circuit though, probably another stage of FET, and require massive heatsinking, probably to the point of rendering the thing utterly nonviable.

The ability to PWM control power comes only at the cost of additional software complexity in the ESC's CPU, where control of the brushless commutation is already being done.

08/01/2020 12:43:57

" technical explanation"

As said, to the best of my knowledge, its simply that you are switching during periods of high current flow. The resistance of the FETs is why the waste heat comes from the ESC.

The switching at full throttle, if I remember right, happens at points of low current (or it may be at zero voltage across the FET, I may be mixing it up). But, I believe it is done at point where volts x amps = zero, so, no waste heat is produced.

08/01/2020 12:07:09

Zero throttle involve no switching and no power, so lets forget that one.

Full throttle involves switching only to achieve commutation. I cannot be certain but I have this dim recollection that the switching occurs at points where the current flow would naturally be low. I stand ready to be corrected on that point. If I am remembering right, this therefore represents very little wasted heat.

In between involves wasted heat during the extra switching required to achieve the PWM control of power. Current flow is likely to be at its highest at the point of switching. Maximum wasted heat.

Either way, any reasonable install will have sufficient cooling and it won't be a problem.

Thread: SOLDERING TIPS
08/01/2020 11:58:54

On the battery, only ever strip back one wire at a time. Leaves less to chance.

"everything must be tinned first & I would have nodded vigorously in support but having soldered them without any tinning all I would say is try it yourself."

The main issue with not having pre-tinned connectors is that of oxidisation, but, when we are doing electric type soldering, there it is almost always a nice quick job, too quick for this to be a problem.

When doing heavier work like UC or cabane wires (or plumbing!) we would use flux to help us out and keep the joint clean.

As ever, 3 secrets to good soldering - cleanliness, cleanliness, and (wait for it) cleanliness.

Thread: Dereck Woodward Bigga Bit
08/01/2020 11:48:53

Bob, great stuff - didn't realise so many of these had been built!

Piers, I think the chief design tool for the bigger and smaller versions was a photocopier! Is that a queen bee on the front of the fuselage?

Open question to the forum...

I have a problem yet to be solved concerning the fuselage. It has what can only be described as "a bit" of a taper at the back. I'm struggling to see how a slab of liteply could be pursuaded to bend that sharply.

How did all you bit builders handle this part of the design?

07/01/2020 22:32:18

About five hours in to this build now. 

Most of the sheeting is on. A single panel wing progresses quickly.

I did some soft block fill in the centre TE area where wing bolts might threaten to squash things. All hidden at this stage.

I now need to get the servo install sorted before I can finish the underside of the centre section. So that's probably the next task, some liteply plates to fit in the two narrow bays.

Edited By Nigel R on 07/01/2020 22:34:06

07/01/2020 22:26:57

20200107_222034.jpg

07/01/2020 22:25:07

Biggest bit ?

Sounds ace!

Thread: SOLDERING TIPS
07/01/2020 13:33:36

Use something fairly heavy to hold the connector as Martyn K says, I use a short length of 2x2 with a few holes into which I can wedge the connector.

Tin both bits, as per standard practice.

XT30 is fairly small, a 25W iron is plenty. I use a 25W on 60A cabling, no problems.

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