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larry cottrill
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Re: heat

Post by larry cottrill » Mon Jul 19, 2004 6:57 pm

Al Belli wrote:Hi Larry,
Stainless steel has a much lower heat conductivity factor than carbon steel. That's why the more expensive stainless steel pots and pans have a laminated structure with stainless on the inside and outside, and an inner core of carbon steel. Cheap stainless steel pots and pans will burn the food at the flame contact area.
Your stainless parts take longer to cool because of the poor thermal conductivity.

Al Belli
Al -

Yes, I was aware of the basic cause of the difference. It's what makes SS welding difficult sometimes because of buckling, for example. My question is really how that plays out in terms of cooling. I'm kind of asking whether the plain steel will deliver heat more effectively to the cooling airflow, or is that more of an issue of radiation effectiveness alone? I don't have any education in heat transfer, but I assume that the pickup of heat by air flowing over the surface must be be largely by contact, and only a little by radiation -- but I'm not really sure how that sorts itself out.

L Cottrill

Al Belli
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Heat conductivity

Post by Al Belli » Mon Jul 19, 2004 7:32 pm

Yes plain steel will conduct the heat to the cooling air more efficiently. Radiation is more a function of emissivity of the surface.

Al Belli

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Post by Mike Everman » Mon Jul 19, 2004 8:17 pm

I recently did my first bit of SS welding, and it heats up much faster than mild steel, even though the melting temp is higher. Another consequence of poor conduction, the heat builds and stays where you're putting it. Got to be on your toes.
Mike
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Sune Posselt
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More on heat transfer

Post by Sune Posselt » Mon Jul 19, 2004 8:28 pm

Hi Larry

I previously linked to this in the tools an construction forum, but just in case you didn't see it, here it is again. I haven't read it myself, so I can't really tell you if it's any good, but if you want to learn more about heat transfer, it might be worth a look.

Sune[/url]

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Post by larry cottrill » Mon Jul 19, 2004 8:37 pm

Mike Everman wrote:I recently did my first bit of SS welding, and it heats up much faster than mild steel, even though the melting temp is higher. Another consequence of poor conduction, the heat builds and stays where you're putting it. Got to be on your toes.
Mike -

With oxyacetylene, I found this especially tricky on butt welding, where one side will buckle up farther than the other. You have to really watch for this as you move the weld along and shift your heat slightly to the 'low' side. My dad told me the same thing can happen with heliarc, though I imagine to a lesser extent. He felt that the only really good solution was starting out with a string of closely spaced tack welds.

What I found with the gas torch was that [as suggested in a book I have] it works well to use a significantly smaller flame than your mild steel experience would seem to indicate, adjusted to be a slightly carburizing flame. Then, once your puddle is developed, move it along a little faster than you might expect, and avoid overworking the puddle in any one spot. Of course, I assume you're using TIG technology, so much of the above may not apply.

L Cottrill
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Cyclodyne_tail_parts_crop1.jpg
Tail cone parts for the Cyclodyne(TM) prototype engine, showing oxyacetylene welds. The dark grey areas are burned flux, which is very difficult to remove. Also shown are the TFE gasket and clamp. Photo Copyright 2004 Larry Cottrill
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Post by Mike Everman » Mon Jul 19, 2004 9:00 pm

I was using gas, FYI; the Henrob 2000. Nice torch, it came with some really fine tips for small work.
Mike
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Al Belli
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Welding

Post by Al Belli » Mon Jul 19, 2004 11:03 pm

Hi Larry,

The sanitary tubing reducing cones and flanges that You show, are routinely welded by dairy milking machine and piping installers. You might contact a local supplier and inquire about having some parts welded, or about the welding process used.

Al Belli

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Post by larry cottrill » Tue Jul 20, 2004 2:27 am

Mike -

Good choice, I think. The Henrob looks like a fine outfit, and their site is even quite informative, far better than most. Never had one in my hand, of course.

Al -

I had a local contractor working on a few pieces at one time; but he goofed on one part [made it right to my satisfaction] and I goofed on the dimensioning of another critical subassembly and didn't recognize my error until I saw the fabricated part. Just didn't have the heart or the money to keep going. And of course, the more 'ordinary' work I wanted to do myself anyway, and I was OK with the results -- it just had to be solid, not pretty. Note: The TFE gaskets aren't really practical for such an engine; I was going to substitute fibreglas mat, cut to fit.

L Cottrill
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Parts is parts. Photo Copyright 2003 Larry Cottrill
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steve
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Post by steve » Fri Jul 23, 2004 4:39 pm

I see there is someone else on this forum who flies CL!
are those kits or scratch built?
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my babies
(F4F wildcat and unfinished P-47)
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larry cottrill
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Post by larry cottrill » Fri Jul 23, 2004 7:27 pm

steve wrote:I see there is someone else on this forum who flies CL!
are those kits or scratch built?
Steve -

Those are all kit built, I'm afraid, although I ALWAYS modifiy them somewhat. What you see hanging up there are the tail ends of a Junior Ringmaster [McCoy 19], a Half Fast III tailless [Fox 35] and an unfinished Berkeley kit version of the Black Tiger, a semi-scale P-40 [will have a Fox 35 if I live long enough to ever finish it]. The Tiger has extensive re-design for greater realism, such as getting rid of the silly fuselage-mounted landing gear in favor of gear in the wings, properly shaped cowl, external gunsight [almost never used in the full-scale ship, but always present], etc. The original was an Open Stunt winner in the Internationals back in 1950, '51 or some such.

Yours are nice looking ships. I especially like the profile stunt jobs [much easier to repair!]. Thanks for posting that.

L Cottrill

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Post by yipster » Fri Jul 23, 2004 10:03 pm

Larry your too modest, on your site i saw plans for a modern piloted pulse jet.
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dont think many flew since these V1's
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Post by yipster » Fri Jul 23, 2004 10:12 pm

Image
only thing flying here now is the old 5 channel RC chopper

larry cottrill
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Post by larry cottrill » Sat Jul 24, 2004 2:46 am

yipster wrote:Larry your too modest, on your site i saw plans for a modern piloted pulse jet.
yipster -

I guess you must mean the Cottrill Dagger ...

L Cottrill

(I think this thread is getting away from us)
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The Cottrill Dagger - Drawing Copyright 2002 Larry Cottrill
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mk
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Post by mk » Sat Jul 24, 2004 1:20 pm

Hello!
yipster wrote:Larry your too modest, on your site i saw plans for a modern piloted pulse jet.
If I'm right these V-1 one man missile was only used for a film showing someone test flying this thing (made in a studio of course). I doubt anybody has ever "ridden the bomb". I saw this film (at least 20 years old, german production) by chance one evening on TV.
Last edited by mk on Sun Jul 25, 2004 12:50 pm, edited 1 time in total.
mk

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Post by Bruno Ogorelec » Sat Jul 24, 2004 2:03 pm

mk wrote:If I'm right these V-1 one man missile was only used for a film showing someone test flying this thing (made per in a studio of course). I doubt anybody has ever "ridden the bomb". I saw this film (at least 20 years old, german production) by chance one evening on TV.
No, it is quite well documented that the 'Reichenberg' has indeed flown. Hanna Reitsch, one of the most famous women-pilots in history did it. Hated its handling, but her suggestions improved the machine greatly.

In fact, poor air performance of the prototypes gave the Air Ministry the idea to have a pilot test-fly the thing to see what was wrong with it. It was a good idea, if kind of dangerous.

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