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Member postings for Peter Christy

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

Thread: ESC cutting out on one type of battery?
25/08/2020 12:35:07
Posted by Ian Whittaker on 25/08/2020 12:21:10:

I was monitoring on a make shift lead (Dodge it and Bodge it field improvisation at its finest!) between the battery connection and the ESC. Surely if there was a bad connection on the plane / ESC side (as opposed to the battery) then it’d show up with all three packs though?

Yes, but my point was that if the dodgy connection was on the *battery*, it would only show up on that pack. I was wondering if the pack manufacturer had released some packs with poor connections or soldering, which might have explained the problem.

I thought that in the finest field-bodge way wink you might have been measuring across the balance lead, which wouldn't show up a problem on the esc side of the connector.



25/08/2020 11:30:23

Where were you monitoring the voltage? Before or after the connectors?

If there was a poor joint on the battery-side connector, the battery would still show good voltage, but the drop across the connector might show low voltage on the ESC side and trip the low voltage cut-out.

If you were monitoring across the balance lead (the easy way to do it at the field!), then that is monitoring the battery directly, and not necessarily the voltage at the ESC, the other side of the connectors.



Thread: Help with continuity testing
22/08/2020 11:34:42

As long as there is continuity between the mains earth connection and the chassis / case, you should be safe. If in doubt about whether the low voltage outputs are isolated properly from the mains, use a neon screwdriver to check (its what they are for!).

Computer power supplies are generally very safe, and designed to "fail safely". After all, you don't want a power supply failure to take out your motherboard and all the disk drives! This applies even more so to server power supplies that are regularly mentioned. The data farms do not want lots of expensive data being lost due to a power supply failure! Its bad for business...!



Thread: OS 28H Silencer Stuck On
20/08/2020 15:01:15
Posted by gangster on 20/08/2020 12:16:52:

Not sure about taking you blowlanp to it but a bit of warmth will possibly help

maybe with your heatshrink gun

That would be my advice, too!

I keep a Kilner jar of red diesel (contaminated diesel from a friendly garage works too!) for soaking seized engines. Takes few days to soak through, but frees the engine off enough to turn over. Being oily, it will also lubricate a bit, unlike acetone.

I doubt it will seep into the threads of the silencer, but a heat-shrink gun should do the job. Just mind you don't burn your hands! Those things get HOT!



Thread: RC IC Engines, you've probably never heard of.
17/08/2020 19:07:28

ED: Are you sure you didn't have some extra head gaskets in there? My ST 29 runs like a turbine in my Lark on straight (no nitro)! I did try it on 10% once, and it got all hot and spitty!



17/08/2020 16:57:08

Comos were indeed a range of engines made by Super-Tigre. I believe they were originally made specially for one of the major US hobby chains, but later became generally available.

Good engines - just like the Super-Tigres! Just be aware that STs were designed to run on little or no nitro! You might get away with 5%, but anything more is likely to have them running hot and horrible! If you must use nitro in one, add some extra head gaskets to reduce the compression!



Thread: NiMh Rx pack check report! ( And a warning?)
17/08/2020 16:51:50

The problem with trickle charging NiXXX batteries is that, unless you monitor precisely how much capacity you have used, they are constantly being over-charged.

This leads to gas venting (which eventually leads to "black wire corrosion" ), and also dries out the electrolyte, shortening the life of the cell.

A peak detect charger will give the cell the charge it needs, and no more.

Having said all that, an occasional trickle charge (once or twice a year) - preferably following a discharge to 1V per cell - will balance the pack, helping to ensure that all cells are equally charged.

NiMhs have a very shallow voltage drop after the peak. Many older chargers fail to detect this properly, though most modern chargers should be fine. Charging at 0.5 - 1 C helps, as the higher charge rate leads to an increased drop for the charger to detect.




Edited By Peter Christy on 17/08/2020 16:52:16

17/08/2020 13:00:06

Posted by Keith Miles 2 on 17/08/2020 12:24:36:

During my LiFe search, I also note that Futaba seem to do a LiFe Rx pack for the princely sum of £75!

That’s waaaaay more expensive than alternative equivalents!

My brain hurts!

RC Japan list the Futaba LiFe Rx pack at 4400 Yen = £31.64! Probably tells you something about UK markups! (Yes, I know about VAT and freight charges, but over 100%?!?)

Turnigy sell a similar pack for £11.90! Component Shop £10-£15 depending on capacity.

Lots of good deals out there...



Thread: Unable to understand OTX configuration for landing gear
15/08/2020 19:24:56

Not if you do it the way I suggested (and probably Steve's way as well - haven't checked it!)

The logic is that the switch is either UP or NOT UP. The middle - logically - is NOT UP.

Ergo, the middle position doesn't actually exist - according to the logic!




15/08/2020 17:55:01

I did it very simply on the Inputs page:

I5:Gear MAX Weight (+100%) Switch (!SA^) [Down]
              MAX Weight (-100%)  Switch (SA^)  [Up]

The mixer line is simply:

CH5:Gear I5:Gear Weight (+100%) [Gear]

Works a treat on my Spitfire...




Edited By Peter Christy on 15/08/2020 17:55:49

Thread: Balance charging HOW?
15/08/2020 09:39:01
Posted by John Wagg on 15/08/2020 09:20:45:

Hope it doesn't sound to daft a question but I presume these resistors are in the charger and not on the battery cells ?

Only asking in case I ever make up my own battery packs. ?


Yes indeed! (There are no daft questions, only daft answers!)

Just to add to some of the above comments: As pointed out by Frank above, most chargers only allow a relatively small by-pass current (compared to the capacity of the pack), which means it can take a long time to balance a pack.

You can get "stand-alone" balancers which will discharge the high voltage cells at a much higher rate. These were quite popular in the days (not that long ago!) when chargers did not incorporate a balance port.

If your battery is a long way out of balance (I have one that I now use to power my starter!), you can reduce the charging time quite a bit by pre-balancing it with one of these balancers.




Edited By Peter Christy on 15/08/2020 09:39:55

Thread: NiMh Rx pack check report! ( And a warning?)
14/08/2020 16:31:52

Hi Barrie,

We're drifting a bit off thread here, so I'll try and make this quick - and maybe we ought to start a new thread on historic radios?

That Skyleader is a couple of generations (at least!) after my Digimite! The first Skyleader proportional was a 3+1 system in a blue anodized case that looked like a re-badged F&M system! (F&M were one of the biggest American manufacturers back in the day). IIRC it used the Bonner Digimite servos.

The first RCS digital proportional also used Bonner servos. Indeed one of the servos I later acquired as a spare has RCS stickers on it! The Digimite used a somewhat different pulse train to modern systems, which makes me think that those early RCS systems were also "clones" of the Digimite!



14/08/2020 15:19:30

Posted by Barrie Lever on 14/08/2020 14:26:43:

The old days was not only cleaning pots but also those Mitsumi motors with the nice little aluminium end can.



This was my first set of proportional radio:

A Bonner Digimite-8 (Circa 1966 - I bought it in 68, 2nd hand)

Inside the servos looked like this:

If you look carefully in this image, you can see the pot track and wiper on the vertical sub-board:

The output rack had 15 or 16 ball bearings down each side, and the case was held together by spring clips! You had to be VERY careful opening them, as otherwise ball bearings would fly everywhere!

The pots needed regular cleaning, so I got quite adept at it!

The transmitter output about 1 watt on 27 MHz (AM). It was powered by a 600mAH 12volt GE Nicad. The receiver ran off a 7-cell 600mAH GE Nicad with several tappings on it! Each servo had seven wires connecting it to the receiver, and it was an 8-channel system. The servos were symmetrical, and reversing was achieved by taking the servo out, turning it around, and replacing it!

It was designed by a couple of guys from the Jet Propulsion Lab in California, and still works today, but I had to replace the original Nicads sometime in the 90s. Black wire corrosion eventually did for them!

The Tx now runs off a 4-cell LiFe (12V), and the receiver off a 7-cell NiMh pack.

Those were the days.....! laugh




Edited By Peter Christy on 14/08/2020 15:20:31

Edited By Peter Christy on 14/08/2020 15:21:23

Thread: Your Hacked charger PSU's.
14/08/2020 14:19:14

No pictures, because it is buried under a lot of other stuff on my "charging" bench, but I too am running one of the HP Proliant server supplies.

Initially it sounded like a Harrier Jump Jet at take-off, but then I found the "whisper mode" mod, and now all is peaceful again!

In fairness to commercial products, I have to say that I have a Graupner 12V power supply that I bought many moons ago, which still works well. IIRC it cost the sharp end of £100, but is only 10 A (120 watts) max!

Makes the Proliant seem exceptional value!

And remember that server supplies are designed to run in a hostile environment 24/7 for years, and if they do fail, to do so gracefully, so as not to damage the equipment they are supplying!



Thread: NiMh Rx pack check report! ( And a warning?)
14/08/2020 14:06:40

Barrie: Well, the JR servos have been exceptionally reliable, many of them in service for years without issue! And as you say, a long way from when dismantling servos and cleaning the pots was almost a weekly occurrence! The only downside is that they are strictly 5V devices, and running of 5-cells or equivalent is asking for trouble!

I've had varying experiences with LiPos! I've had Overlanders, Zippy's, ThunderPower, you name it! I think the ThunderPowers (which came highly recommended!) were the worst! Expensive, and puffed up very quickly, despite only ever being charged at 1C. My first set of Zippys were good, but subsequent purchases not so. I've got a couple of Turnigy Graphite packs, which so far are holding up well, but on recent experience, the Overlanders are the best. (There! That's done it! Watch them puff up on the next charge, now!)

I only ever charge LiPos at 1C, rarely discharge them below 25-30%, and over the long winter / lockdown period, made sure they were all on a "storage" charge. Perhaps I need to abuse them more! It certainly seemed to work with NiCads! wink

As far as safety goes, whilst I've heard of - and seen - plenty of LiPo fires and explosions (one took out a whole hotel suite at an international heli contest, and got ALL the competitors banned from the hotel!), I've never heard of a LiFe going up in flames!

The thing is that it doesn't take much - a moments inattention is sufficient - to set off a LiPo. Not so a LiFe, and that's aside from any tendency to spontaneously go off!

For traction motors, LiPos are a necessary evil and should be treated with respect. But I won't use them where there is a practical alternative.

I'm probably being over-fussy, but I do have quite a few very old models. The Cobra I mentioned earlier belonged to John Haytree, and is believed to be one of the first in the UK (around 1970/1). I do try and look after them, as they are like the exhibits at Old Warden, reminders of where we came from! I would hate to lose one due to something avoidable!



14/08/2020 10:27:41
Posted by Keith Miles 2 on 14/08/2020 09:59:55:
Is it my rose-tinted glasses leading me to the view that things were once much more simple?

Entropy always increases! wink



14/08/2020 08:58:22

Barrie: Like yourself, most of my models are i/c powered, but I do have a few electrics - mostly smaller types. However, I do have an early 70's Schluter Cobra helicopter that I have converted to electric, but even on that I use a separate 4-cell NiMh battery pack for the radio gear (3300 mAH, sub-C cells - also helps with the CofG!).

In the absence of NiMhs, my preferred option is a 2-cell LiFe pack. This is a much more stable chemistry. It doesn't have the same reputation for spontaneous combustion that LiPos have, and yet can deliver plenty of current for even the most demanding servos.

One of my problems is that I have an awful lot of JR servos, and these are notorious for not being happy at higher voltages! The cost of high voltage replacements would be excessive, to say the least! However, I do have one (vintage) helicopter fitted with high voltage HiTec servos that runs very happily on 2-cell LiFe cells.

LiFes are stable enough to leave in the model for charging, whereas for LiPos, it is generally a good idea to charge them in a safe place (not surrounded by highly inflammable balsa or foam!).

I also don't like the use of regulators or battery backers! Down the years, I've seen these cause far more problems than they've solved. I know of at least two cases where the use of these devices has caused a dramatic reduction in range, and one where a regulator caused so much glitching that the model became dangerous to fly! It was cured instantly by going back to a 4-cell NiMh!

I know some ESCs have built-in regulators for the radio, but some of them have worryingly low current capacity.

To my mind, the best solution is the simplest, and that means using a good quality battery of sufficient capacity, the right voltage and low internal resistance. It also means having as little as possible between the battery and the receiver. My Cobra doesn't even have a switch for the radio! I just plug the NiMh in before the LiPo flight pack!

Keith: You're right! I hadn't realised that 2000mAH AA Eneloops were suddenly in short supply! I've certainly been unimpressed by the higher capacity versions! Just as well I have a couple of spares! To my mind, adding an extra cell is applying a sticking plaster rather than tackling the root cause of the problem!

Back in the NiCad days (shortly before they were withdrawn) I used to use a lot of 1900 mAH sub-C packs. These days I use the 3300mAH NiMhs for the same purposes (helicopters with lots of servos, larger models, etc).

Unfortunately, our hobby is a small consumer of batteries in the grand scheme of things. Most of the bigger manufacturers (Sanyo, Panasonic, etc) seem to be in a numbers race to attract the camera (and other domestic appliance) brigade. This is not necessarily to our advantage!

"Back in the day" we used to fly quite large models on 500mAH DEAC button cells! OK, the servos didn't draw as much current back then, but for all but the most serious flyers, 2000 mAh is more than enough for a day's flying! When I come to top mine up, I find that they rarely take more than 500 mAH.

Planned obsolescence is unfortunately something with which we now have to live. However, I'm an eternal optimist, and I'm sure something will be along soon to fill the gap in the market...!




13/08/2020 18:52:11

Keith, try the process I suggested. Discharge at 1 amp down to 1V per cell. Don't worry about reducing the current. Once the pack is "flat", trickle charge at 0.1C (200mA or so) for 10 to 12 hours. Then repeat the 1 amp discharge test.

You might be surprised by the result!

Of course, its always possible you *do* have some duff cells - I have some Vapextech ones like that, but I keep those for bench tests!




13/08/2020 16:39:05

I have to say that I've never had a problem with genuine Eneloops, and all my packs are clearly labelled as genuine Eneloops (never come across a genuine one with a white case!). However, I always get the basic 2000mAH ones (or 800 mAH, in the case of the AAA cells) as the higher capacity ones definitely have a higher internal resistance.

Having said that, they are all used in what I would describe as relatively lightly loaded environments. The AAAs are used in my smallest single channel models, and the biggest I fly with the 2000s is a 60 powered KingPin (60s aerobatic model), though that does have four Futaba digital servos on board.

Never had an issue with them, though after the end of the lockdown - which followed a horrible winter - I did make sure to cycle them before use.

First of all, I discharged the 2000s at 1 Amp. Every pack still had between 60-70% of its rated capacity, despite having been left like that for over 6 months!. Following that, I trickled charged them at 1/10C overnight. The result? Full capacity restored!

It is not normally good practice to trickle charge NiMhs because of the danger of overcharging and venting. However, doing it *occasionally* will balance the cells, and NiMhs packs need balancing once in a while to maximise their capacity.

For larger models (some of my big helis), I use 3300mAH sub-C NiMh packs. These have no problems in even the most demanding environments, and can actually help with CofG issues in some models! wink

Oh, and ALL my packs are simple 4-cells. Never found the need for higher voltages. (And yes, I do have some DSM-2 receivers - some very old!)

I do have one helicopter that I fly with a 2-cell LiFe pack for the radio gear, but that has high voltage servos fitted.

I don't like the idea of using LiPos for flight radios. There are much better (and safer!) technologies around! I can tolerate them for the flight power, because such packs usually have quick access to remove / disconnect when things go wrong. Also, there isn't really much alternative!

But for normal small to medium size models, don't be too quick to write off NiMhs. They are very safe, and if looked after properly will give years of good service.



Thread: Is it possible to rotate the throttle arm on the SC52 four stroke?
10/08/2020 22:28:22

I've done it on an ASP30FS, and I would imagine the SC is similar. Forget what I had to do now, but I know it wasn't difficult.



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