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Old Jul 15, 2011, 03:45 PM
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Oh yeah, Ok, I understand now.
Thanks
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Old Jul 15, 2011, 04:17 PM
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Southern Spain
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Irvine converted their glow 20 to diesel and supplied the same glow muffler, but without the pressure tap, to avoid users running across this problem.[/QUOTE]


Sorry, this is incorrect. Both the Irvine 20 and 40 diesels were purpose designed and not converted glow engines and they came with muffler pressure as standard.
This so called problem is a load of nonsence. It can't occur with alcohol fuels because water is miscible with the fuel and in any case if it were correct with diesels, the fuel pick up clunk is at the bottom of the tank and water could not collect.
I have been using pressure on R/C diesels for something like 15 years and have never seen a trace of water in the fuel tank
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Old Jul 15, 2011, 08:13 PM
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For anyone who didn't already know, the reason that Charlie's engine looks vaguely familiar is because the designer (Ted Martin) also designed the Amco 3.5 BB. BOB
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Old Jul 15, 2011, 10:03 PM
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Quote:
Originally Posted by Twin-Stack View Post
For anyone who didn't already know, the reason that Charlie's engine looks vaguely familiar is because the designer (Ted Martin) also designed the Amco 3.5 BB. BOB
First thing I thought on seeing it was that around the exhaust area it was a bit BB Amco looking..........so now it makes sense including the rear rotary intake and the designer whom I think went to Canada/USA in about 1950 or so.
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Old Jul 15, 2011, 10:13 PM
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Makes me feel less of a cheat when I prime every time
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Old Jul 15, 2011, 10:49 PM
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Canada, ON, Hamilton
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Charlie, that's a great looking diesel. A real work of art. How about a few more pictures?
John
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Old Jul 15, 2011, 11:13 PM
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from John Moore...."Sorry, this is incorrect. Both the Irvine 20 and 40 diesels were purpose designed and not converted glow engines and they came with muffler pressure as standard.
This so called problem is a load of nonsence. It can't occur with alcohol fuels because water is miscible with the fuel and in any case if it were correct with diesels, the fuel pick up clunk is at the bottom of the tank and water could not collect."





The bottom of the tank is where the water will be.

PS I don't care for arguments, but John you are misinformed on the Irvine 20 Diesel. Lacking a scanner, you will just have to trust me that this is a partial quote from "Motor Miscellany", Radio Modeller February 1991 edition, under the heading

"Irvine 20ABC R/C Diesel"

"This is the latest and, perhaps, the most significant example of the dieselization of an existing glowplug engine, in that it was initiated and developed by the engine's manufacturer. Ever since they began producing their own motors in 1977, Irvine Engines have specialized in glow engines (the sole departure being their production of the Mills 75 replica) and the fact that Ron Irvine decided to press ahead with the production of this diesel version of the well-liked and very successful Irvine 20 series, obviously indicates considerable faith in its capabilities.
The Irvine 20 has not been extensively redesigned for diesel operation. It has a new crankshaft; otherwise, dieselization is confined to the cylinder head assembly, plus small modifications to the carburettor and silencer.".

After describing the reduced-choke carburettor, the author continues....

"The reason for having this much reduced choke area is to enable the engine to be operated without the assistance of an exhaust pressurised fuel system, which is the reason why the diesel version of the silencer has the usual pressure nipple replaced by a screw-in plug.
Why no exhaust pressure feed ? Simple! Exhaust gases condense to form a certain amount of H2O when they come into contact with the cool fuel in the tank. A little water in the fuel does not matter in a glow engine; it is miscible with methanol-based fuel and a small amount can be tolerated...Diesel fuel, on the other hand, is petroleum based (usually kerosene, occasionally DERV). Ergo, the water remains separated and, having a higher specific gravity than that of the fuel, settles in the bottom of the tank, where it may be sucked up by the clunk weight. Not even diesels like running on water. Result: malfunction of one kind or another...".

The author was Peter G.F. Chinn.

C
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Old Jul 16, 2011, 02:18 AM
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OK Thanks

Amazing article , something to think about ,

Maybe it fouls up the fuel flow at the spraybar / needle area ?
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Old Jul 16, 2011, 07:08 AM
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I finally found it.......a Webra Record of the particular '1954-59'-version...and it's 'NIB', unrun...

For your info, this is the engine that my dad brought home, I think 1958....
Not my first engine though, but my first 'real' engine......it certainly has a special place in my heart...I have so many memories with this one.....
I have to confess that just re-seeing the box again, slightly raised my heartbeat...

I know this engine isn't among the rarest ones, although strangely, I haven't been able to find one since my 'engine collecting' started...

Yeah, indeed I feel happy with this purchase....full circle...?...time to stop collecting now..?...well.....


Quite difficult to find a Webra Record NIB of course do remember that Germans do mainly collect their own German made engines lovely little engine I'd love to have one myself, lucky find believe me
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Old Jul 16, 2011, 10:33 AM
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Quote:
Originally Posted by Chas View Post
The bottom of the tank is where the water will be.
Just to expand on this as I am considering a blown fuel tank to help draw fuel from 70mm below the spray bar centre line in my application, I went to 'The Shed' to test.

Using 3cc of Model Technics D1000 and 2cc of hot water with a sprinkle of instant coffee to use as a water dye, here is a picture of the test result inside a 5cc syringe. I apologise for the out of focus result, sadly photography amongst other things is not one of my strong suits.

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As you can see, there is nearly 2cc of water at the bottom which readily formed and settled, a smidge of 'froth' (the combination of which looks like a great pint of traditional hand pulled ale) then the diesel fuel on top.

Here is why I am looking at pressure blown fuel tanks. I may be able to raise the tank above the spray bar height but lack of space dictates it is better as is if possible. There is NO possibility of a conventional aeroplane fuel tank layout with this. Just no space!

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Old Jul 16, 2011, 10:37 AM
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Well, I think we need to consider draining and flushing the fuel tank from time to time, if we use muffler pressure. Of course it may or may not be a problem depending on your locale and how much ambient humidity there is or something like that or the muffler design maybe. I haven't seen the problem with water in the fuel tank yet myself.
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Old Jul 16, 2011, 10:59 AM
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As the PAW is kaput due to a rather unique failure, I cannot test just how much water is produced in the exhaust per 100ml of fuel burned.

Shame.

I am in a good enviroment to test as I am close to the sea and relative humidity of the ambient air is always quite high.
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Old Jul 16, 2011, 11:11 AM
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I have often seen water droplets on the fuselage/wings of combat models, mixed in with the traditional black diesel sludge - usually only in typical British combat weather though! Could be from the ambient air, but the same conditions will prevail inside a tinplate tank.

Anyway, why would you want to use muffler pressure on a diesel? Fuel draw is the last of your problems with such small venturis.

Of course, Dave Day goes as far as to question how anyone can pressurise something with a big hole in the back of it
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Old Jul 16, 2011, 12:04 PM
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I flew a Tower 40 with RJL head on muffler pressure with good results. The venturi is the same one I use flying glow. I tried a magnum Pro 40 with the same head and muffler pressure. It did not run well; would burp and miss. The airplane was nose heavy anyway, so I took the muffler off and the engine ran to suit me. The magnum muffler is bigger than the Tower muffler, and I thought that might have contributed to the problem.
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Old Jul 16, 2011, 02:23 PM
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I guess Jim if you're using a glow-sized venturi, you may need exhaust pressure for adequate fuel draw....another reason not to use head-converted alcohol engines.
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