Electrifying a Wot 4

[Tim Mackey]

My latest order from H/C just arrived this morning...ordered on Monday  - pretty good huh !!

Amogst it all is a 60A Turnigy Plush ESC ( which I cant remeber now why I ordered  ) and it states on it ..... "5.6V DC to 26V DC"

A fully charged 6s LiPo without load will be 25.2V..so assuming your ESC is the same version, ( and it may not be  ) then it will handle 6s.

You want suggestions for UBECS, or ESCs with BECS ?? 

 UBEC I use on large packs is here .....and good for 5A constant with up to 42V input ( 10s Lipo )

PS if you want this excellent T urnigy Plush ESC its yours for what I paid, plus p+p to your place. As I say.....cant remeber why I ordered it now - a senior moment I guess

[Danny Fenton]

Its not just me then......................

[Tim Mackey]

Nope !

[Tim Mackey]

Right - the order from Hobby city Hong kong arrived Thursday, not bad as it was only ordered on Monday so I now have all 6 x A123s. have just made up the battery for the wotty to continue the trials as above - more results soon.

[Danny Fenton]

A real battery pack!! now we are cooking I think you will be the first to publicly test more than 4 cells. All the mags were testing just three.  Mind you six is just about our minimum. You need a Sea Fury with 8 or 10cells next

[Tim Mackey]

I got the 2 extra cells from our fav HK supplier - 15 dollars a piece - around 7.50 in our dosh at current X rates.

Not bad I guess for genuine A123s, Puffin price is not bad either though at roughly £10 a cell made up into packs ready to use. I think they need to get a whole lot cheaper before they get mass acceptance, and of course viccky verky!

I know the specs say 25C rated - thats 57.5A....but the headline says 60A capable continuous. Of course, at those sort of currents flight duration will be short to say the least. I always try to stay around 15C maximum for my setups.

[Chris Bott - Moderator]

Timbo, I've had 110A out of them for a short period!  Volts did drop off alarmingly and I don't think I'd do it again. But the good news is that they survived. So propping to impress and then using careful throttle management to extend flight times, is a route available to us. 

I personally like to fly with the taps right open now and again, (Huge loops and verticals) and in between, give myself and the batteries a rest. So I tend to prop for 40-50A, use cell count to get the power I need and then fly with a much lower average current.

Having said that, I let Ian Redshaw fly my 3Demon last year and he was pretty much prop hanging for the whole flight. The batteries didnt seem to care. I did have to warn him just how quick they run out, and just in time too, I think that saved the model...

[Tim Mackey]

Hi Chris...yeh I am sure they will deliver big currents for short bursts - they are pretty meaty cells.... it was more the duration issue. The whole issue of matching up the components for a successful powertrain, incorporating the various parameters such as satisfactory duration, power, thrust, speed etc is, I think, the biggest single challenge facing us when electrifying models - beginners especially so. Trouble is, as you know, there are several ways to approach it, EG start by deciding what revs you want, or whether thrust is more important than top end speed, or what current is manageable, or what weight is allowable, etc etc.

I tried to suggest a method that hopefullly explained one such approach in my "electrickery" article, but no matter how many times I read it, I still dont think I achieved it .

Your brief description above also will not work terribly well for the raw beginner - not meant to be a criticsm incidentally - but logically working along your path, you say

1)I prop for 40-50A

2) Use cell count to get the power

3) And then fly with lower average current".

Trouble is, to choose a prop for the target current in step 1, you will need to know the intended cell count at the same time IYSWIM.

It is a subject which I shall return to one day, and hope to have a simpler to understand method, easily understood by the novice. I know several companies have tried to approach the problem by offering "IC equivalent"  electric motors ( Eflite for example ) but they have not quite cracked it IMO, a look at any such advertisement will still reveal several variations - all on the supposed IC equivalent! Of course, I and others such as yourself who have a bit of experience under our belts realize that options of Kv and Wattage handling factors are partly the reason, but I always try to write for the beginner / non electric minded people.

The quest continues.

I hope the weather is better down the there - winter has returned with rain, wind, and low cloud here

[Danny Fenton]

Hi Timbo, Yes I think once you have a bit of electrickery under your belt a few props and cells and of course the essential watt meter then you can start playing. I think what Chris is trying to show is that you can create a setup for a great deal of power and what appears to be no real duration but in fact if you fly the model using its momentum and don't try to use brute power to perform a loop but inertia it is simply amazing how little energy is required even with a hevyweight ic conversion. I keep coming back to my YT Hurricane because it is fairly heavy at 6.1 kilos, yet I sucessfully flew it around at between 400 and 600 watts. (After the initial 1400 watt takeoff burst) The sea fury was another, yes it used 1kw to take off really easily, but then with it throttled right back and flying with just enough power to execute the intended manouvre, you can relly extend the duration. Just cos you have a killowatt available doesn't mean you have to use it What you are trying to do is always going to be difficult, but the parameters are fairly straightforward, Volts, Amps, Mah.

[Former Member]

[This posting has been removed]

[Tim Mackey]

Danny...why are you not at your show ?? or are you, and being truky geekish and staying online in the middle of a field ! Yes, I understand what Chris is saying and I did study the info you sent before on the hurricane and sea fury.

Eric....not sure I remember now, but think it was RS - or maybe farnell...or maybe Maplin..... LOL

EDIT: just googled the model number, and few came up....including this one here ( identical to mine ) at a bargain £3.75 on fleabay.  soldering cleaner

[Danny Fenton]

Its an IC fun fly all my stuff is oil free these days. So not quite as involved, I have however just come back from visiting the lads. The layout is great this year, and since we bought our own ride on mower the grass is suburb. I was helping Chris with the on site IT setup, he is having a few teething problems with getting the live feed to the web site. I think it is to do with the incredible heat and sunshine at the field

[Chris Bott - Moderator]

Timbo

Good luck in your quest. It would be great to see such an explaination for beginners.
Although part of me says if it was that accessible, most of the fun would go out of it..

I totally agree my method does not cater for beginners at all.
I think its actually more of an observation, that all the models I have on this particular battery type has ended up, after experimentation with motors/props/cell counts:-
1 - Well overpowered, but if that power was used all the time the duration would be low.
2 - Working at 40-50A flat out.
3 - Eagle tree has really surprised me at how low the "averarge" power is that I end up using.
4 - An obvious one - The duration depends on the average power and not the max power.

So am I kidding people who watch a flight and see both awesome performance and a long flight??

my  next setup will probly go as follows:-
How heavy will the plane be?
How many watts for 100W/lb (depending on model type)?
How many cells do I need for that power at 45A?
About what prop size do I want?
What KV motor do I need to drive that prop at the pitch speed I want.  This is where I start to rely heavily on previous model data and a wet finger.
What motor of that KV is available that will handle the power I want?
How much will the setup weigh?
Will that weight bring the model to the desired weight? (The lower the better)
Purchase motor
Try the chosen battery/prop with it, measuring current, revs and power.
With a little luck I may only need to change to a slightly different prop size to get the readings I'm after.
Try it in the model, and adjust prop again if necessary.
Be prepared to buy another motor or add a cell to get it right.

And this is a simple one because I'm restricted by my chosen battery only being available in one mAh size. Add the ability to use many different sized batteries and the number of variables just multiply.

As I said, good luck with the beginners explaination...

[Danny Fenton]

I think this thread and other just goes to show that there are no real wrong ways to do things its just some are more efficient LOL as long as you use a watt meter and throttle your test rig up slowly, take the manufacturers recomended max voltage and current seriously, no harm should be done. (put something heavy on your test rig though, don't want your workmate taking of   )

It is much easier for us making our own packs to just add or drop cells, we also have a small arsenal of props from 4" up to 20" so we can play. It is easy to forget that when we were just starting out wiring a pack with a balancer lead was new ground.

But it is fun and very sattisfying when a model flies well........ okay flies LOL

[Tim Mackey]

Well said both - and Chris, your approach in that post above is pretty well smack on how I do things too. All I need now is to write it all up in manner which beginners and non sparky peeps can understand .

I will doubtless incorporate some of your wordings , and credit you duly EG: a sticky bun or two !

I have done some initial bench tests with the new "6 pack" and will post them a little later

Hope the fly-in went OK - weather was a bit naff, and today its blowing real strong !

[Danny Fenton]

yes even i cannot claim that it isn't a little blowey. If anybody is close to Greenacres and wants to pop down and say hello then the gang would be happy to see you. I am sure the traders would too. Our hobby is very weather dependant and it hasn't been very kind this year. still as I heard recently, the models don't know its windy.......

[Chris Bott - Moderator]

The tally of sticky buns is adding up nicely -

Well, we had a funfly, which is a little lucker than some other events that have not gone ahead at all this weekend.

Friday evening was gorgeous, we had a great fly off the peg and barbeque.
Saturday was cold and swung between rain and drizzle untill after lunch.
The rain stopped and we had a good afternoons flying and a good number of enquiries about membership which is always good, topped off with a barbie in the evening as the wind picked up.
Overnight saw gazeebo frames (without fabric) blowing away, and campers hanging on to tents from the inside...
Sun morning and it was clear that we needed to cancel the day because of the wind.
At least all canvas was dry and we spent the morning "rescuing" tents and marquees etc that were all threatening to make their own way home..

Oh well, we can all start again in a month.. maybe the weather gods will be a little kinder?
Oh and I'm trying to organise a mobile sticky bun van for the next event

[Tim Mackey]

Hope its at least a 6 wheeler

[Bruce Richards]

6 wheeler? I would have thought an 18 wheeler would be more appropriate!

[Tim Mackey]

Didnt want to push my luck

[Danny Fenton]

Mmmmmm Donuts

[Tim Mackey]

thats a good un !

[Chris Bott - Moderator]

is this thread about wot 4's or wot buns?

Lol - we could have done with a bun warmer this weekend..

[Tim Mackey]

Careful with that spelling there Chris - a sticky bun goes to the first person who can name the group who did a similar sounding song - extra jam if you can name the album too !

This is a time limited competition, and all entries must be received before 1705 hours today

PS Wot4s, modelling in general and sticky buns are inseperable - especially if the jam oozes out.

PPS I have just finished a nicely warmed up Jam doughnut - Thanks Mrs T

PPPS as its "my thread", and PS1 ( not the playstation ) applies.....this is not off topic

[Chris Bott - Moderator]

Thats OK then, if you say so

No idea about the song.

So, when can we see the first electric wot 4 sticky bun dropping flight at a funfly??
Actually, that might be a bit of a waste of good buns??