Bob,

I imagine (but it is your jusdgement) that you can increase pretty much the precision of your
measurements in the following manner:
1. Get a stroboscop from the car guys which is used to see the ignition instance, or use a photo-flash.
2. Drill and place a nipple beside the glow plug and use that pressure to trigger the stroboscope.
3. Then instead of propeller place a heavy wheel like those used for the boar engines. Behind or in front of it
place a disk on which outer surface you mark every 1mm axial line for about one half inch distance.
So the idea is pretty classic one: - when the pressure in the head chamber triggers the flash then you will see
which mark on the disk is seen due to the stroboscopic effect. With different plugs you should be able to see
different mark on the disk and from there you will find which plug is hotter = it should flash the earlier
mark on the disk, isn't it.

Check also my post earlier today. Using that old DDR-idea you can install second plug on the head of your
engine, drill it trough and fill it with transparent material, like melted quartz. Then you will see what is going
on inside of the head-chamber of your engine... It is amazing thing ...

Of course the professional laboratories for engine research have much more precise instruments.

For example, why not visiting the nearest University, I believe that is University of Dallas or Texas A&M
university and ask if they have some lab where the undergrad students will enjoy having a course project
and measure some bunch of glow plugs for you. For sure in those Universities there are many who are
at least interested also in RC flying.

Cheers,
Nick

Quote:

ORIGINAL: Oldbob

The question was; “Is there a hotter glow-plug than the Merlin?� I was looking for a yes or no answer and a brand name if the answer was yes. It appears that no one knows the answer.

Bob,


And it seems it is either that there isn't one, or that if there is such a plug, it is so rare that no-one knows about its existence...

The hottest glow-plug made in large numbers is the OS A3/#6...
A close second is the Enya #3, which has a desirable trait... It 'behaves' colder, when installed in mid-size engines.

The Novarrossi C-5S is also close...

I believe the [link=http://shop.vendio.com/RossiEnginesUSA/item/2019666765/index.html]Rossi R1[/link] may even be hotter than the Merlin, which I have never seen.


Most people have probably not heard of hotter glow-plugs, simply because no-one ever asked, or needed his/her plug to be any hotter...
...Until you came along, that is.[>:]

Which Merlin plug (they have a full range) are we talking about?

I've tried their 1/2a ones but it seemed a little cold to me. The Rossi R1 might well be the hottest, but the OS#8 usually does the job well enough...

Heavy Duty Hot, #HD2003

It 'behaves' colder.....?

Bob, I suggest you ask this question in the Jett Engine forum. Bob Brassel should be able to give you the answer you’re looking for. I buy Merlin Plugs from Dubb Jett.

Oldbob, seems that Merlin has changed their range, I think I have had the 2003 but not the HD2003.
They list the 2003 as being similar to Enya#3 so the HD2003, being hotter, may then correspond to a Rossi R2... (only guessing though)

Quote:

ORIGINAL: Broken Wings

It 'behaves' colder.....?

BW,


Yes.

The OS F plug is hot.
It is intended exclusively for four-stroke engines; to retain the glow over the exhaust period, so it is capable of igniting the mixture, during the engine's next revolution...

Large engines need to use colder glow-plugs and smaller engines need hotter glow-plugs; yet the F plug behaves very nicely in large engines, like the ST 2000-2300 and many others.
It does this, despite being hot and it is not necessary to richen the mixture, beyond the cold plug setting for the same engine...

...Hence; 'acting' colder in some engines...


The Enya #3 is the only plug they specify for four-stroke engines; despite not having the 'protruding snout', Ã* la OS F...

Like the OS F, it also 'behaves' like a cold plug, under certain circumstances.

Dar,

Is it F so hot or it is massive to retain the temperature, or both ? - please specify.

Nick

My oh my, I didn`t know until now how difficult and complex it is to choose a plug for my engines, it is almost rocketscience it seems[sm=lol.gif]

I run OS F in all my fourstrokes, they might cost a $ more than others but so what? they last forever, I think I have never blown one of those.
In my twostrokes I use whatever I have at hand, mostly OS 8, 5, 3,also the F, Towerplug, Sirio`s, Rossi`s, Mc Coy 59, ASP, and propably lots of others. After a needle tuneup I can hardly tell the difference between them in the air or on the ground (car, boat)

I did some peak rpm testing a couple of years ago and in my engines rpm never varied more than max 300 rpm peak no matter what plug I used, so I think for casual sportflying it really doesn`t matter that much

Quote:

ORIGINAL: NikolayTT

Is it F so hot, or it is massive to retain the temperature, or both? - Please specify.

Nick,


A "hot" glow-plug's element, does not necessarily glow any hotter than a 'cold' one's.


What differentiates a hot plug from a cold one, is its heat retention.

This could be achieved by using a heavier gauge platinum wire (which takes longer to cool off) for the glow-element, but it can also be achieved by better 'insulating' the element, against heat-loss.
It is all in the time it takes the glow to cease - a hotter plug glows for a longer period.


Regarding the OS F; I can not sure if its glow element has a heavier gauge than, say, an OS #8.
But with its longer 'nose', the element does not lose its glow quite as quickly.

That should clearly indicate that with the approaching winter most of us have got more on the talking than on the
building and flying side of the life. At least frankly I feel so... and I fully agree that in many cases it is very
hard to tell which plug is used if the fuel and the engine are having some kind of "common sense set-up" proportions,
i.e. if we stay away of the extreems... It might be good to agree with some of the earlier posts about What
each type of enigne wants, i.e. to pay some respect to those who built the engines and wrote the manuals...
I am afraid some of them are looking with pitty at some of the statements at RCU and let us talking endlessly
here without even writing a single word (at least I know one guy like that from a very advanced RC engine
making company; he is even wandering how we can spend so much time & money to re-discover the Universe ...

How is the weather in Norway ? Here we got already the first snow flakes but still is above the freesing
point and ... I keep writing instead of flying ....

Nick

A question: - How Hot are the Non-RC plugs when compared to the RC types ?
Anybody has tried some of them for RC flying, please share your observations.
Thanks,
Nick

Pretty bad around here now, not too cold but lots of wind and rain, snow in the mountains though. I write more than I fly too these days

There aren't any non-RC plugs, actually there aren't any RC plugs either....there's just glow plugs . Choosing a plug for an unthrottled engine is much the same as choosing one for an RC engine, apart from not having to worry about how it idles or transitions. Although come to think of it, I guess you could say they transition from not running to flat out as soon as you give them a flick. Most of the time you can barely detect the time it takes to reach full speed . My favourite plug for engines that I run 4 stroking rich is the Taipan red (hot) plug. There's no discernible rev drop when the glow igniter is removed. This is with zero nitro fuel so it could possibly be too hot for nitro.