By continuing to use this site, you agree to our use of cookies. Find out more

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: Navy carrier landing
23/03/2017 15:40:44

The pilot certainly earned his salary with that one!

--

Pete

Thread: RC equipment reliability
21/03/2017 14:32:07
Posted by MattyB on 21/03/2017 12:37:03:

Correct - the DSM and some first generation DSM2 RXs had brownout voltages in the 4.1-4.2V range. That proved well within the window of vulnerability if using an aging 4.8V pack as the power supply for high power/large numbers of servos.

And that hits the nail squarely on the head!

It never ceases to amaze me that modellers will spend months building a model, spend hundreds of pounds on RC gear, and then power it using a battery and switch that they pulled from the last wreck! angry

I used to have a friend who ran a model shop, sadly no longer with us. He used to sigh with relief when a heli flyer came in! "Why?", I asked him. "Because they think nothing of spending £100 on a servo, if that's what's needed! Fixed wing flyers argue about the cost of the cheapest servo / batteries / switches I stock, despite the effort they've put into building, and the amount they've spent on receivers and engines!"

I have to say that looking around some of the local clubs, I can see where he was coming from......! disgust

--

Pete

20/03/2017 15:45:47

MattyB: An excellent summary! However, as one of those who came to the hobby before proportional control was actually available - analogue or otherwise - I feel duty bound to point out that we *had* to install our equipment carefully!

Reed and relay receivers (some had as many as 12 relays on board!) had to be mounted "just so", and with as many as seven wires going to each servo, heaven help you if your wiring was not tidy!

I suspect the sloppiness to which you refer (and I agree it is out there!), started when equipment began to arrive pre-wired, and ready to use "out-of-the-box".

devil

--

Pete

Thread: Cooling fins
20/03/2017 12:19:06

On a typical model engine, the most important part to cool is actually the cylinder head! This is much more important than the cylinder jacket, though of course that does need some cooling too!

Look at some boat engines, where the water cooling jacket only surrounds the head - not even a fan for the cylinder! Also most heli engines, where either an extra large head, or a clamp-on heat-sink for the head is required.....

--

Pete

Thread: RC equipment reliability
20/03/2017 08:23:02

An interesting question! I've been flying R/C since 1965, and even in those early years, the radio gear was remarkably reliable. The worst issues I had were with sequential escapement skipping, a problem that completely disappeared when I switched to compound escapements!

My first set of "reed" gear (Graupner / Grundig) only let me down twice, and that was due to a faulty receiver DEAC (early NICads) rather than the gear itself. (We didn't have any means of easily checking capacity back then, and didn't know about the "memory" effect!)

I still have it and it still works fine, though I haven't flown it in years.

My first set of proportional gear (a second hand Bonner Digimite) never let me down, though the servos did need regular maintenance! Again, I still have it, and it still works today!

My red-box Sprengbrook only failed once. That was when I was out flying and the temperature dropped below zero! The SCS decoders were well known for being sensitive to low temperatures! I bought a bag full of SCSs, and replaced each one in both receivers, testing them with a freezer spray, and never had an issue after that!

My home-made gear never let me down, nor has any JR equipment. I recently suffered my first receiver failure with 2.4 GHz gear - fortunately during preparations for a week-end flying - when a Spektrum receiver that hadn't been used for a while refused to bind. So far my FrSKy gear has also proven absolutely reliable. (There! That's done it now!) smile o

So, in 50 years of RC flying, I've had two electronic failures, and one of those was 40 years ago, and down to exceeding the tolerances of the components! The other was late last year.

I don't think that's a bad record for any kind of equipment, so I would say yes, RC gear is generally very reliable, and has been even from the early days!

--

Pete

Thread: low amplitude ppm out on Futaba Transmitter
18/03/2017 16:29:46

Excellent! The old FM modules tended to have the pull-up in the module, as it formed part of the modulating circuitry. So do many of the 2.4 GHz plug in modules, so that they can work with 35 MHz transmitters. Looks as if your module didn't do this!

Anyway , good result, and well done to Gonzo too for spotting it!

--

Pete

Thread: Engine Guru's wanted!
18/03/2017 16:24:37

Well done! Glad its sorted!

--

Pete

Thread: low amplitude ppm out on Futaba Transmitter
18/03/2017 09:28:19

Keep us posted as to how you get on!

Good luck!

--

Pete

18/03/2017 08:58:20

Good find, Gonzo! A "pull-up" resistor from the PPM output to Vcc may well be needed for this module. I'm still puzzled by the "differentiated" appearance of the pulses, according to the OP. Without a pull-up resistor, you usually see very tiny, but correctly shaped pulses, whereas he is describing spikes where the edges should be.

Also some modules (early FrSky hack modules, for example) could be damaged by having a pull-up, and actually required the opposite - a diode in the line to prevent the voltage rising above the internal (regulated) voltage of the module.

Bob's point about the pins suffering from weak soldering is also very true - especially if a lot of module-swapping has taken place.

But opening up a transmitter can be quite fraught - lots of wires between the front and rear case, switches holding things together, etc - which is why I don't recommend it unless you are *really* convinced that that is where the fault lies!

Check everything else first!

--

Pete

17/03/2017 21:22:46

David, you are missing my point somewhat! On the face of it - and assuming you are connecting your 'scope straight across the transmitter pins - this looks like a fault in the transmitter. However, that is fairly unlikely, and before ripping the transmitter open, you really want to be sure you are not being misled by a poor connection between the 'scope and Tx.

A faulty connection between the 'scope probe ground and the transmitter would also give the symptoms you describe, and would not be shown by the 'scopes test / calibration point. Hence my question, does the trace change when you remove the ground? (Switchable X1 X10 'scope probes are notorious for this!) If there is no change, then the 'scope connection is faulty.

The final check is does the Tx work OK with its own module? If so, then the Tx is not at fault.

Some modules are very fussy about what you feed them. The Taranis is switchable between +ve and -ve going PPM. I have a feeling it defaults to negative, but its been a while since I changed mine! I think Futaba is positive going (I rarely see Futaba transmitters, and don't have one to check.) Some modules are also fussy about the width of the pulses supplied, but these are very much in a minority. They do still work, but the neutrals shift a bit!

Before you start trying to fix the transmitter, make *really* sure that's where the fault lies!

--

Pete

Thread: Durafly Spitfire
17/03/2017 21:06:16

Enjoy!

laugh

--

Pete

Thread: Engine Guru's wanted!
17/03/2017 18:02:31

The copper gasket in the head should have provided a good enough compression seal. The screw being exposed like that shouldn't make any difference, as it is outside the gasket.

Might be worth a call to Dave Wilshere for a replacement gasket. Also make sure that both sides of the gasket and their mating surfaces are spotless before re-assembling, and that all the screws nip up tight.

I can't see a small compression leak causing your problem though. I used to have a Webra 61 that spat raw fuel out of the head / cylinder join if over-primed, because of a leak, but it ran just fine!

--

Pete

Thread: low amplitude ppm out on Futaba Transmitter
17/03/2017 17:45:08

David - have you checked the ground connection? What you are describing would also be cause by no or a poor ground between the 'scope and Tx.

--

Pete

Thread: BMFA NEWS
17/03/2017 16:03:59

Referring back to comments I made earlier about having edited a newsletter, and comments others have made about going on-line....

After I retired, my successor decided that the newsletter would be distributed electronically, by making it downloadable from the website, thus saving money. Now it may have been coincidental, but shortly afterwards, membership numbers began to fall, and the usual chorus of "What do I get for my money?" and "Why wasn't I told about that?" began.

When it was pointed out that all the information requested was available in the downloadable newsletter, the responses came back: "Oh, that! I couldn't be bothered to download that!"

The basic rule of life, "You can't win!", proven again!

--

Pete

Thread: low amplitude ppm out on Futaba Transmitter
17/03/2017 15:29:40

OK, but what about the ground pin? Does what you see on the 'scope change if you remove the ground connection?

--

Pete

17/03/2017 14:46:17

"Highly differentiated" - sounds like a poor connection somewhere, and you are just getting capacitive coupling.

I'm not familiar with the Futaba pinouts - are you sure you have the pins correctly identified?

--

Pete

Thread: Engine Guru's wanted!
17/03/2017 14:42:09

One question: What fuel are you running it on? From the size of the motor, I'm guessing its low nitro, but STs don't like nitro. Straight is best (no nitro) but certainly no more than 5%.

The fact that its slowing and stopping when idling says its rich at the bottom end, to me. That won't help the pick-up, as rich mixture will need to be blown clear before the engine will pick up properly. Indeed, it may well flood the engine when the throttle is opened, causing it to stop! It should drop back to a steady idle. If you overdo it and lean it too far at the bottom, it will drop back, and then pick up slightly.

Perry carbs are great once you get them set up, but can be pigs to get correctly set in the first place!

On the original ST carb, the two needles are for high and low speed running (obviously!), but rotating the spraybar slightly improves the fuel draw in the mid range, helping the transition. The inlet nipple should point to the front mounting hole, as that picture of Brokenenglish's beautifully illustrates!

Best of luck!

--

Pete

Thread: BMFA NEWS
17/03/2017 09:36:55

As someone who edited a specialist body newsletter for a number of years, I can assure you that getting copy from members is like trying to get blood from a stone!

Any editor of a specialist publication like this will snatch the arms off potential contributors! If there appear to be more free-flight and control-line articles, its because members of those disciplines can actually be bothered to write about their activities!

The BMFA does not have a staff of journalists working on this magazine. Even commercial operations like RCM&E have few full-time editorial staff. The BMFA mags depends heavily on contributions from members. No contributions from a certain discipline, no coverage! Simples!

I had this argument a couple of years back with a vociferous group on a heli forum. One of the members took me at my word and wrote an article. It was immediately published!

Q.E.D.

wink

--

Pete

Thread: Sharkface
16/03/2017 08:42:38

Andy, you may well find that full chat is essential to get it airborne! I've been building Sharkies on and off since the original plan was published, back in the mid 60s, and on a calm day they need a javelin like hurl plus a wiggle of the rudder to get them away!

The plus side is that you can fly them without problems in the kind of winds that would ground all other models of similar vintage!

Mine have always had Cox .049s up front. I did build one (still have it!) for a TeeDee .049 with rudder and elevator. Even with a TeeDee screaming its head off, it required a fair bit of up elevator to get it away on a calm day!

Once its built up flying speed, there's no problem. But then again, it was designed to fly in the teeth (Ha!) of a howling gale! devil

--

Pete

Thread: Durafly Spitfire
16/03/2017 08:31:19

The Spit in the video is a dream to fly, and it looks a million dollars in the air, but the landings are tricky. Its nothing to do with the handling of the aircraft, which is excellent, but the wheels are tiny and very close to the CofG. To achieve a decent landing, you need a patch like a bowling green. Very few in the UK are like that at this time of year!

On the recommended 4S, performance is ballistic! It will leap off the ground like a scalded cat, with virtually no take-off run! Not very scale-like, but handy on rough strips! On the plus side, because most of the time it flies at half throttle (or less!) you do get a good duration. The book says it will fly on 3S, but duration will be decreased, and you will need to add some nose-weight to compensate for the lighter battery.

The retracts and flaps work well, and certainly make it look more realistic on approach. However, the undercarriage is very rigid, with no "spring" in it whatsoever, and this exacerbates the landing issues. No matter how gently it is landed, I usually have to bend the legs forward again to get them to retract properly on the next flight. This takes quite a bit of force. I've removed the undercarriage doors from the legs to reduce the tendency to trip up on grass, and assist with straightening the legs afterwards.

I've had it a few months now, but only two or three times have I managed to land it without it tripping up. Very rewarding when you DO manage a perfect 3-pointer without ending up on your nose - or worse, on your back! In the video, I was slightly caught out by the rising ground, the prevailing wind being in the other direction, but being honest, it wasn't one of my better landings, and the results are plain to see.

But for all that, it is a joy to fly, and when you *do* get the landings right, it will bring a big smile to your face!

--

Pete

Email News - Join our newsletter

Love Model Aircraft? Sign up to our emails for the latest news and special offers!

Latest Forum Posts
Support Our Partners
TJD Models
SHREK
Gliders Distribution
CML
Overlander
Advertise With Us
Latest "For Sale" Ads
What's the main radio brand you use? (2017)
Q: What's the main radio brand you use?

 FrSky
 Turnigy
 Multiplex
 Hitec
 Futaba
 JR
 Spektrum
 Graupner
 Jeti
 Other

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us