Electrifying a Wot 4

[Tim Mackey]

Hey Danny, I am finally getting around to electrifying the missus' Wotty, - not going for ballistic, a modest 500Watt BRC  cheapie is being fitted on some home made stand offs as we speak !

Now here's the thing to get you excited in the morning, a 4 cell  LiFePO4 battery is in postie's bag this morning

For anyone else interested, I can do a few photos and details along the way, but be warned, its not clever and its not pretty - this is an OLD Wot4, which has seen a lot of use and modification in its life. I bought it 3rd hand a few years back to teach the missus to fly on, (  before anyone else says it...broomsticks were more expensive ) and it was well gunged then! I stripped and rebuilt a lot of the front end...

.....dont you love the smell of fuel soaked balsa and ply in the morning  

Wifey sees me flying electric everything these days aprt from the Spifire, and gets a bit fed up having to mess about with fuel and starter motors and glows etc, not to mention the cleaning down after, + I think IC engines are a bit more intimidating for her than clean and quiet electric, so hopefully she will be more inclined to want to fly it and get on with her training. Anyhow....more info to come as progress is made. WARNING...slow builder at work 

[Chris Bott - Moderator]

It excites me Timbo!I think the A123's will excite you Mind you when we did Dannys Wot4 (watt4?) we put 6 A123's in.
This was to keep current down and duration up. Oh and to be balistic

[Tim Mackey]

Hi Chris ! - Yeh I know....but I dont want ballistic, - its a trainer still for the missus so I went for larger slower prop style for good thrust, decent response, and slower flying style - ( gonna use a 12" X 8" or 13" X 6 "probably...not done the bench testing of the rig yet, motor is mid range Kv at 919 - I am aiming for circa 400 - 500 watts and an AUW of just under 5lb....should be fine for her.

It has had a fair few different engines in its life, and the firewall is a bit of a swiss cheese at the moment. I have decided to cut through a slot large enought to pass my 4s LiPo packs ( I already have them for a different model ) so will try those as well as the LiFe's and stick 'em well out front to aid the COG - as everyone knows, Wotties are real short in the nose and I refuse to add dead weight to a model.

I will use 3" long stand offs ( machined up from some old aluminum stock ) and fit a new outer skin to the firewall to tidy things up. The stand offs will be spaced wide enough apart, and long enough, to enable me to fit the 4s LiFe pack between them, and I dont have, or intend to fit a cowl so recharging and connection should be a doddle, as well as coolng !

The standoffs are externally threaded at one end, screwing into blind captive nuts behind the firewall, and will have a seperate ply motor mounting plate at the sharp, which will screw on with nylon bolts into internally threaded 5mm holes - this will hopefully give a little safety margin for when she starts landing practice !

The second motor mounting plate also enables me to easily change motors later on if I want, without having to change / reposition the stand-offs, which wpouild interfere with battery fitment.

A few pictures of where I am up to so far - should give the idea, before and afters - should be self explanatory

.....as usual click for the bigger picture

[Chris Bott - Moderator]

Dont forget A123's are down on voltage compared to lipos.  You will be disappointed with comparative performance if you don't/cant fit a bigger prop.

[Tim Mackey]

Yeh , I know -  I am hoping the M1s ( 2300s)  should hold around 12V though at around 35A for about 420 watts, and I could push the amps a little higher if needed with a slightly bigger prop. If not, then its back to good ol LiPos !!

[Chris Bott - Moderator]

I love the look of the motor mounts - is that a service you will be offering to the rest of us

Think I'd use 4 rather than just the one

[Danny Fenton]

Timbo!!! that motor will make mincemeat of that stick of alloy!! do as Chris says make some more, you really need 4........

Whats wrong with good old thread-all from B and Q I don't know

Seriously glad you are having a play with the wotty, I did find the pack didn't have to go as far forward as you may think, maybe because I was using a fairly large motor.

Also a 14" x 7 (perfect prop for mine) hits the ground on takeoff, so have had to go with a 13 x 6.5 I see you are using the glass U/C that may give better clearance, I am not sure.

[Tim Mackey]

Yeh the glass underrcarriage does raise it a tad....but I will stick with 13" max. I ran out of threaded rod- but have loads of ali bar...besides gave me an excuse to use the lathe which apart from the back ache, I find very rewarding and satisfying

The tail end on mine is a bit agricultural, been repaired a few times by the other previous owners who were over-generous with the epoxy and fillets -  a quick trial with the 3200ma 4s Lipo ( which is a bit heavier than the LiFe ) showed it all needs to move forward a fair bit....and this 500 watt motor is a bit of a lightweight compared to my Turnigy 1000 watt jobbies

Anyway...finished for the day now..... latest picture shows all 4 x standoffs - a days work - told you I was slow

[Danny Fenton]

Here Chris we know where to go to get lathe work done eh? Very nicely done too slow - but you cannot rush some things

[Tim Mackey]

Cheers....Yeh no problems matey....happy to help you if I can.

The reason for it being so slow is mainly because of the rather tedious way that tools are changed on this particular lathe...bit cumbersome really, still it does get the job done .....eventually

Posty didn't deliver my LiFe pack, so unless it comes tomorrow, I am looking at a test flight BH Monday with the 4s LiPo

[Danny Fenton]

Booo hisssss, don't go near the puffy things....... shame you aren't closer could have tried a set of ours.

The weather up here is pants, really hoping to get Electric Sea Fury airbourne but not looking good for the weekend

[Tim Mackey]

Yeh I know, but then they have been known to be wrong

[FlyingAngel]

I have some good news for the Wot 4 owners who want to electrify their Wot4. You can visit this sitehttp://www.chrisfoss.co.uk/news.htm where there are plans for converting your Wot4 to electric power in pdf format.

[Danny Fenton]

Too complicated using those puffy cells.  Danny's guide to Wot 4 conversion..... 

1.  Remove smelly, noisy vibraty thing and drop in a bucket of degreasant (so you can sell it on EBay)

2. make a 1/4 ply disc of about 3" diameter. Four 50mm bolts from B and Q (with nuts and nylocs naturally).

3. Fit motor to ply disc with long bolts as per picture earlier in the thread.

4. Take oily plastic bottle out of model and bin it.

5. Replace plastic bottle with block of six A123 M1 cells (cannibalised from a de Walt battery pack. Feed power leads through hole were fuel lines were.  Wedge in with foam and anything else you have lying around the workshop.

6. Tie wrap a 60A esc to the bolts and go and fly.

Battery trays???? cooling holes????? thats for the puffy cells

[Tim Mackey]

Oy! - stop hijacking my thread  you Ion-iser

Hi FlyingAngel - Yes I have seen that and did a quick download of it last week - not used it to be honest because my batteries need to further forward than shown on his plan, and this is meant to be a simple and easy way to convert what is an old and rather tatty model. If I was building from scratch, or indeed it was a newer model, then I think his suggested mods are good - especailly as it allows battery access without removing wing.

Of course Mr Fenton will now chime in about how his LiFe packs dont need removing, and how he can charge 'em up at the field in 20 minutes etc

Incidentally danny, where do you source your dewalt packs ? Ebay seems a little devoid of them at present, or maybe its my lousy searching technique? 

[Danny Fenton]

Timbo you are quite right EBay has been quiet of late, fortunately they last forever so my little pile of 40 cells just gets moved around. Our chums in HK are doing them as loose cells $11 each if memory serves me, I needed a couple for the Fury to take it from my standard 6 brick to 8.

Sorry to hijack your thread, I will go and sit down now

PS they only take twenty mins to charge if I completely flatten them, usually an 8 minute flight in Wotty only takes about half so 10 mins and I am airborne again.

right going to lie down now and not interrupt Timbo anymore.......

[Tim Mackey]

Thanks mate...yeh I spotted them in H/C but thouight it was not the cheapest way to get em...but looking at UK retailers, it may well be !! Cheers mate, enjoy your lay down

[Danny Fenton]

Hi Timbo just tomake sure people don't bid on just any De Walt packs here are the models you are looking for:

DE9360 = 36 volts 10 cells

DE9280 = 28 volts 8 cells

DE9180 - 18 volts 5 cells

Just searched E-Bay and there aren't any, wander whats going on, have we let the cat out of the bag

[Tim Mackey]

Thanks Danny...yep looks like you have already got them all in West mids !

[Danny Fenton]

Theres a gang of 4 or 5 of us at Greenacres that use em so you are probably right.

Alan Fry @ Importeknik is I believe selling them for £11 a cell, with a tag welded on.

I did a talk at Clent RC model club on A123 Nano Phosphate Technology and they have dried up since then..... maybe I shouldn't have said anything LOL

I have just heard worrying reports on the potential of a sticky bun shortage at Weston, did you eat all the buns at Orme by any chance????  

[Tim Mackey]

Of course I didnt, that is just a filthy rumour put about by that scoundrel and bounder Ianski Kev!

What cell capacity are the Importeknik ones ?

[Danny Fenton]

they are the same 2300 I haven't seen any of the smaller ones though the "Killowatt Club" Greenacres A123 gang lol, have some to play with. They don't appeal to me, I would be happier to have larger capacity not smaller. There is talk that they (A123) are producing a LiPo shaped cell but with Nanophosphate technology, in several capacities but I haven't managed to get my hands on any yet.

[Tim Mackey]

I have got one of the 2000 m/a capacity packs from BRC, ( I actually ordered the 2300 version but something went wrong ) so have ordered a second 2000m/a and will be using 2 x packs in parallel....but thats £80

I must say that the reasons I really went for Ion were

• fast charge rate ( although the jury is out whether 3 or 4C is do-able...I will live with 3C me thinks
• experimental...I havent been weaned off my polymers yet
• durability and crash resistance - its a trainer ship for the wife
• life cycle - which is calimed to be almost into 4 figures whereas LiPo can be as low as 50

The lower cell voltage I can live with, in this, and many other applications I guess, but the price is still V HIgh, and until they tumble like LiPO has due to volume of sales then I am not going to buying many more

[Danny Fenton]

Ahh sorry Timbo you are ahead of us. we haven't played with these. I cannot tell you whether they are the same in behaviour to our canned cells. If the chemistry is in fact the same then they should behave the same. Certainly the canned ones we charge at around 10A and have seen no ill affects. That limit is simply because of the limits of our charging equipment A123 quote 20A as being okay. We have recharged several hundred times I guess and the packs are virtually as good now as they were 2 years ago, hope these are the same.

We need to find out what other applications these are being used for so that we have a chance of getting them at a realistic price. What are the dimensions and weights of your packs, I suppose I should go and wander around Mr Collins web site

[Tim Mackey]

Hi Danny.

This version ( so called square although its rectangular actually ) is 260 grams and 110 x 38 x 30mm

The one I actually ordered was 2300 mahr and 70 x 54 x 54 weighing in at 315 grams. These I guess are the original and genuine as it were, A123 manufactured cells....in the metal can cylinder shape.The chargeability info is a little confusing, stating that " Can fast charge up to 3C (9.9A) in just 20 minutes"

Well of course 3C on a 2300 cell is only 6.9A so either their sums are wrong, or the instructions are referring to a different cell. I have pointed this out to them, so we will see if they correct it.

My new packs will not have quite the crash-ability of those but I fancy trying them anyway - will double up 2 x packs for the extra capacity. I am unsure where the 2000m/a version I got is from, possibly the new "LiPo shaped version" that you mentioned earlier ? - they are just packaged and branded as BRC, but quite probably A123 manufactured. No charge instructions on website, but the leaflet with them suggests 4C maximum, recommended 3C, yet it also states "recommended charge current 3A ( which would equate to 1.5C ) and a maximum of 8A which of course is the 4C. So in all they suggest 3 x different charge rates 1.5 / 3 / 4C.

I will stick to 1.5C at home, 3C in the field, thats still only 20 minutes - just right for coffee and stickys

Cell voltages are also very confusing - recommended 3.6V, rec maximum 3.8V , maximum allowable 4.2V

As my charger on default is set for 3.6V then that is what they shall get !

Interesting that you say you charge your 2.3A M1s at 10A - thats almost 4.5C - and supposedly alright up to a whacking 20A ( 9C ).  Have you ever done any at 20A ? ( I know you said your charger was the limit )

My charger is limited to 150 Watts, so theoretically on a 4s I should be able to crank it up to 10A, but it is also limited to 7A max, which would be close to the max allowed rate anyway for the 2000s. I've just done an initial balance charge at 4A and got the following... seems about right I guess, but very little put in ( 25ma ) suggesting they are shipped pretty well fully charged which is unusual.

IMO these parameters desperately need clarification if people are to buy into this chemistry in big numbers.

You can see why so many peeps shy away from "Electrickery huh "