Fun Cub or Wot 4 foam e?

[Steve W-O]

There are articles on how to do it on another forum, and it means working with SM resistors. I think most people replace them with 1/8W ordinary resistors, or just putting one in parallel with what is already there if possible.

[Simon Chambers]

There are two (or 3 if you do both) ways of fixing them.

 

The first is to replace the voltage divider resistors that measure the cell voltages to 0.1% tolerance components (the clones use 5% tolerance - hence the problems) . It is detailed here: RCGroups - IMAX B6 -- Read this before you buy.

 

Secondly you can put a voltage divider network to put 4.2v across each balance output, and 25.2v on the 4mm battery charge terminals. Then re-run the calibration/service menu routine. However this isn't always possible, as some clones have the calibration disabled. The calibration is disabled after the first run, however some of the clones have literally taken the original firmware from a working device and copied it over - hence the cloned chargers have the incorrect calibration values stored in them. If it is disabled, you will need a Atmega IC programmer to reflash the firmware in it. Detailed here: iMax B6 service menu

 

I did the second step, as I didn't want to pay out to fix it (I'm a cheap skate :D). I built the calibration connector out of a bunch of 1k resistors soldered onto a veroboard with a chunk of DIP socket to jam into the balance port. As I didn't have any 0.1% resistors to hand, I found the closest tolerance parts by sifting through 100 1k resistors I had in my component selection. Now cells 1-4 are accurate (which I verified by my calibrated fluke), but 5-6 aren't (the resistors for 5-6 must have been not close enough). I'm not worried as the largest pack I have is a 4 cell, most are 3.

 

Ideally you would do both steps. However for me, when I need more than 4 cell charger, I'll buy a iCharger.

 

Hope this helps.

 

Si.

[Simon Chambers]

Oh while I was reprogramming the firmware, I also hacked and changed the startup message :D

 

Just in case I ever loose this piece of junk...

 

 

[Bob Moore]

Thanks for your long and detailed reply Simon. I had done a bit more Googling and found the links to access the service menus, and the resistor kits etc. as well. And loads of discussion on the thing and other clones. Plus I found a couple of good YouTube videos explaining how to programme the thing for a normal balanced charge. (I didn't really understand the manual and it's certainly not written for newbies to bigger electrical stuff. I knew about charge rates and balancing etc. but not a lot more. The programming of the thing isn't obvious, though easy once you do know how.

 

This morning I charged the 4s 3300mA LiPo supplied at 3.8v per cell from GC. I got 16.70v total and 4.15v -- 4.21v ---- 4.18v ---- 4.14v per cell.

When the on screen display says finished and shows 16.8 v my DVM shows 16.7v . I'll try and get my dvm checked against a calibrated one and may adjust that .

 

I don't think it's too bad overall though and am more likely to screw it up completely trying to de solder and replace those tiny little resistors!

 

Once my DVM is checked I may try and reset the cell values too. But for for the moment I'm going to leave it alone.

 

I like the new start up message, but I suspect your knowledge of this stuff is a way bit beyond mine!

 

P.S apart from that it's been a better day. I got the mounting kit for the motor and figured how I'm going to mount it. Figured I'd replace the Wot 4 cowl which I'd cut out for the IC engine.  £20?  for a new one. Someones having a laugh. I think it will be a fibreglass botch job instead!

Edited By Bob Moore on 08/02/2012 13:35:57

[Simon Chambers]

Its not too hard to repair it, just a bit of hassle. The surface mount resistors are 0805 size, so large enough to be easily hand repair without optical assistance. You will need a good quality iron, ideally temperature controlled, with a small tip that is capable of soldering lead-free joints (temperature around 360-385C). Also it helps to have a pair of tweezers and desoldering braid to remove and clean up the solder.

 

To reprogram you will need a Atmel programmer, and unless you have one to hand (I borrowed one from a colleague at work) its not worth doing. As to buy one, you'll spend around the same as what you paid for the charger.

 

If you don't repair it, it would make a very good NiCad/NiMh/Lead acid charger - but personally I wouldn't trust it with LiPos. You'll spend far more on the LiPo's than what this charger is worth, and its not worth shortening their life by using it.

 

If you don't have a power supply to charge indoors, consider converting an XBox 360 mains adapter. The best ones are the original old versions (the older ones handled more power - around 200 Watts at 12v). You can pick them up cheap or free (especially if its from an broken original XBox 360 - they failed extremely common - if you have sons/daughters/relatives who game, they may have one) and they are really easy to convert, plus overloaded protected (i.e. won't be damaged, or damage anything else if abused or used incorrectly). See A Simple High Quality 12v 200W Power Supply for a rough guide.

 

Essentially, the 3 big bottom pins on the connector are ground, the 3 big middle pins are 12v and you short the top two small pins together to switch it on (one pin is 5v, the other is power enable). Chop the connector off, solder up or use a terminal block to tie each of the three pins together, put a toggle switch (optional) on the two small pin wires and done!

 

If others are interested, I can write a short how-to-guide with pictures post on how to do it.

Edited By Simon Chambers on 08/02/2012 14:45:22

Edited By Simon Chambers on 08/02/2012 14:46:38

[Pete B]

Wouldn't it be sensible to post this discussion on a new thread with an appropriate header so that it is searchable in the future? It's got very little to do with either a Fun Cub or a WOT4!

Pete

[MMG]

Have two WOT4 foam`s in my small collection. Why two, well the first one suffered a rather nasty, heavy collision with a patch of ground that suddenly and inexplicably rose up into the air! Nothing to do with the plane, just good old fashioned pilot error; my son will now remember to carry out all of the pre-flight checks properly (no, I was not present for the maiden flight). The wing had cracked almost right across the chord, the rudder became a waving appendage to the fin and the tailwheel had parted from the rudder, the prop was reduced to one and a half blades,the motor mount bent, the u/c was just hanging on by the proverbial thread. So, I ordered another WOT4 foamE before contemplating the repairs to the original (I was out of the country when the collision occurred), which duly arrived at the same time as I did. Carried out the repairs, on the original model; very easy in the end, and with the exception of the u/c mounting (yes this is a weakness with the design), it flew without any problem at all, not even needing a change to its original trim. The replacement WOT4 was duly assembled and flown, and both have now been flying now for many hours without problems (apart from the poor u/c mounting - just use lashings of epoxy to re attach it each time). Well, nearly without problems.

The replacement WOT4 did suffer its own nasty, and yes, pilot error again (still my son) when it `landed` in a vertical attitude, nose first full bore upon exiting from some form of aerial manoeuvre carried at at a height of three metres (max). Result; prop of course, u/c of course and a `new` break! (not sure what marks/tariff is applicable for this part of an aerobatic routine, can some one let us know?). This new break was the fuz which had snapped at its mid length point on three of its four sides. More epoxy required, but again it flew without any sign of a problem. So, all the problems with both models have been carefully induced with lashings of great aplomb by the pilot and not the plane(s).

 

Moral: plane good, very good in fact apart from the u/c mounting method; pilot - ah well.

 

Yes I (we) can recommend the foam WOT4.

 

[MMG]

p.s. just in case you think I have been a bit harsh concerning my son, this all happened about nine months ago, and he is now a far, far better pilot than I.

Edited By MMG on 08/02/2012 16:41:13

[Stephen Grigg]

And you know you will never catch up with him now MMG

[Simon Chambers]

Posted by Pete B on 08/02/2012 14:55:32:

Wouldn't it be sensible to post this discussion on a new thread with an appropriate header so that it is searchable in the future? It's got very little to do with either a Fun Cub or a WOT4!

Pete

Sorry I tend to get a bit carried away.

To bring my posts back onto topic...

 

My experience with the Wot4 Foam-e has generally been good. The problems I've had, tend to be user caused. The first was damaged after, like MMG's son, an aerial manoeuvre too close to the ground. The second was written off after I, basically, over-cooked it by fitting a 4S pack, and not securing the tail fin correctly. Straight nose after the elevator failed in dive at full throttle. Of course I can't blame Ripmax for this, as its not sold on the basis for a 4S pack (even though one fits).

 

Its the plane I finally got the hang of flying with and took my A-test with, so I guess that also makes me like it. The first one I crashed I stored and with a new motor mount on order (I have no idea what shape the old motor mount should be re-bent into), will hopefully be in the air again soon.

 

I love Multiplex stuff for their durability and good design. I like the idea that you can choose exactly what power-train you want with the FunCub (which is good, as Multiplex recommended kit is frightfully expensive). However that's also another reason I don't like it! The problem with choice, is that there is too much darn enough of it. Many different setup's recommended by different people for different purposes.

 

With the Foam-E, you don't need to worry about power train setup. Just buy it, screw it, stick it and fly it.

Edited By Simon Chambers on 08/02/2012 18:00:21

[Steven Buckingham]

Can I put in a good word for the Wot 4 Foam-E. I might have been lucky in getting a good one but mine flew every weekend in all sorts of weather (except actual rain) right through the winter, with no change to the original components, that was until the wing fell off mid air (wing bolt pulled through the wing! Hmm maybe this isn't such a good word.) Amazingly very little damage and quickly had it flying again (with a whopping great washer on top of the wing). I have just written it off today (let a learner have a go and he put it nose in) but it had got to the stage where I was almost wishing it would die so that I could get something else.

Oh and I will be replacing it with.... a FunCub, can't argue with the reviews!