help with glow plugs!

what are the different applications where you would need either a cool, medium cool, medium hot, or hot glow plug?
does a long length give any better performance over a medium length?

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The length is determined by the thickness of the head. Generally, engines smaller than .25 use a short plug and larger ones use long plugs.
You generally want to use the coldest plug that gives you reliable running. A hotter plug may be needed when idle is not stable or very low/no nitro fuel is used. A colder plug may be needed when using higher compression, tuned pipes or higher nitro.
--
Paul McIntosh
RC-Bearings.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Much information under sub sections "Carburettors, Tuning & Performance Testing, Glow Plugs." at Alan's Hobby, Model & RC Web Links http://homepages.ihug.co.nz/~atong / especially those under Glow Plugs- Brian Hampton Glow Plugs - Selection Guide - cross reference of most plugs. Glow Plugs - The technology of How to Rebuild Your Nitro Engine - RC Nitro Magazine,***
Alan's Hobby, Model & RC Web Links http://homepages.ihug.co.nz/~atong / .................................................................

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Rather than worrying about the heat range of the plug, you should be reading the plug to determine if the needle valve is adjusted correctly for best performance. For example:
1. A very white or frosty looking filament or element is an example of an engine being run too lean.
2. A brown or dark element is a sign of running too rich.
3. Aluminum particle on the element are a sign of poor manufacturing methods. The engine parts weren't properly cleaned before assembly.
As long as the plug is mechanically correct for the application (short, long, or idle bar), the heat range of most plugs isn't of too great a concern, since they are in a fairly narrow neighborhood.
What is of concern is the high-speed mixture (usually the factory setting on the idle and intermediate mixture is OK). A lean mixture can quickly destroy your engine especailly if you're using a full-synthetic fuel (one of the reasons I prefer some castor oil). A rich mixture is wasting fuel and depriving your engine of potential power!
Finally, I should mention the importance of castor oil in lean engine situations. A lean engine mixture cause high internal engine temperatures. These actually break down the castor oil providing more lubrication for your engine. Probably the wisest thing most modelers could do is use some castor oil, since very few of them know how to tune their engines.
Ciao,
Mr Akimoto
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Several incorrect statements here.
The heat range is much more critical to proper running than is stated. Too hot of plug will cause the engine to be difficult to set at high speed and can cause preignition and detonation. A plug too cold can cause unexplained flameouts and lower power outputs. The key is to find the plug(s) that run properly for your particular engine and fuel.
Castor oil does not break down under heat. It actually forms more complex molecules as heat rises until it forms near solids. This is the gum and varnish you see on ehgines run very hot with castor based lubricants. For this reason, castor is good insurance against lean runs. Also interesting to note is the fact that engines run with castor based lubes tend to be very clean inside if the engine is run at richer mixtures minimising heat.
--
Paul McIntosh
RC-Bearings.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
The oil is there for two purposes: lubrication and heat removal. If you run the engine too lean, you actually start burning oil and the internal heat builds up. One suggestion that I've always followed is to find a good solid high-end position (engine does not lean out or sag when you point the nose vertically during ground running), then back off several clicks. The result is that you will see a slight trail of smoke behind the plane in the air.
What does this have to do with the length and type of glow plugs? Nothing, but the fact that everything is related to everything.
Best recommendation that I can make is RTFM -- read the engine manual and note what the manufacturer's recommendations are for the type of flying that you'll be using for the engine.
Another quick way is to go out to the field and see who is flying a similar plane and engine to yours and ask them which plug they're using. Nothing works like success.
One thing that is missing from your opening remarks is which engine you are looking at. I flew the OS/magnum .45 engines, and used the Fox long with idle bar.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
To all:
As usual McIntosh is full of hot air. He pretends to be an authority on everything and is in general, wrong about most subjects he broaches. You'd think this guy would try to offer some evidence to substantiate his rhetoric.
Here I offer the best bit of evidence about the effect of heat on castor oil and why it protects model plane engines from the heat of a lean run:
http://www.flitelinesolutions.com/castor_vs_synthetic.html
Castor oil does indeed break down or decompose under extreme temperature conditions. Paul should stick to selling ball bearings for engines. It's an occupation that doesn't require much thinking or analytical ability.
Finally, in regard to the heat range of glow plugs, I'll stick with my statement this isn't a terribly critical element of engine performance - at least for model plane engines.
Ciao,
Mr Akimoto
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Paul has forgotten more valid model engine information than you will ever know.
Posting a URL does not make te URL's content fact.
Ed Cregger

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks, Ed. I hope that I haven't forgotten too much yet! I still got a few years left to go.
I am now getting into electrics as the cost/fun factor is getting near equal for me. I like YS91 performance on 40% nitro!
--
Paul McIntosh
RC-Bearings.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Mr Akimoto. Paul McIntosh has more knowledge of this hobby than you can ever hope to have. I keep saying I'm going to put you in my killfile , but Damn...I get such a kick out of seeing you make a complete ass of yourself. Keep up the good work.
Ken Day
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hell, Ken, I hope I can retain as much as you do!
--
Paul McIntosh
RC-Bearings.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I know that very few of you ever graduated from high school and likely aren't very intelligent to boot; therefore, I'll help you read the post.
In good technical writing, you always find a summary paragraph somewhere near the end of the piece. In this case:
"Most synthetics boil on the cylinder at temperatures slightly above their flash point. Synthetics also have another interesting feature - they would like to return to the materials from which they were made. These are usually things like ethylene oxide, complex alcohols, or other less suitable lubricants. This happens very rapidly when a critical temperature is reached. We call this phenomena "unzippering" for obvious reasons. So, you have a choice. Run too lean and the engine gets too hot. The synthetic burns or simply vaporizes. The castor oil decomposes into a soft varnish and a series of ester groups that still have powerful lubricity."
Notice the very last sentence: The castor oil decomposes (or breaks down) into a soft varnish and a series of ester groups that still have powerful lubricity.
I know my audience on this forum, so I write in a simple style as not to confuse any of you, since most of you are already too confused to begin with. As for you Paul, if I ever need any ball bearings for my OS engines, I'll buy them from OS. Now go play with your balls (in your bearings of course)!
Ciao,
Mr Akimoto
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I don't really care who you buy your bearings from because you wouldn't know what you were buying in any case. That wasn't great technical writing because there were no temperatures listed and no empirical results noted. Only vague references to lean runs. I have been involved with model engine DESIGN for many years and I know that by the time castor decomposes into the esters, other parts of your engine are destroying themselves.
That article was also written several years ago and doesn't have the benefit of modern synthetic advances. If you can find it, try some Excalibur fuel. It is all synthetic and easily survives lean runs with pylon and other racing engines.
--
Paul McIntosh
RC-Bearings.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Perhaps you missed this little statement in the link you posted: Castor oil forms huge molecular structures at elevated temperatures - in other words, as the temperature goes up, the oil exposed to these temperatures responds by becoming an even better lubricant!
It will, indeed, begin to break down at extreme temperatures. The kind of temps that destroy engines. But even then, they are breaking down into materials that are also great lubricants, ie: esters!
As for plug choices, I think that anyone who has actually tried different heat range plugs know what the affects are.
--
Paul McIntosh
RC-Bearings.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.