Mistakes in Aviation

[buzzard]

I worked as a machinist for a company that made equipment for the fishing and food processing industries, so we used a lot of various grades of stainless steel (SS) and aluminum. The various alloys have differing properties, including hardness, malleabilty, toughness, corrosion resistance, etc. The non-magnetic SSs are generally more corrosion-resistant and higher priced.

The most common welding techniques for both metals are known as TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas). Both metals will burn at high heat levels, so an inert gas (usually argon) is sprayed over the welding focus to exclude oxygen. With TIG, the welding rod is hand-held, while MIG guns contain a roll of wire which feeds automatically. TIG is for more delicate work.

Incidentally, I have my great-grandfather's Model '95 (Made in '98 ) Winchester in .35 caliber...and it's stainless nickel steel. 110 years, and no rust yet!

[Graeme]

Hi buzzard,

Been stick welding for years (backyard) and have always been frustrated with burning 'holes' in thin metal despite using low amps and even 1.6mm rods. I have been procrastinating about buying a small a MIG welder for some time now but know next to nothing about them. I can't justify a huge expenditure but my question is when there around 100amps is there much 'quality' in them?

Or is my arc welding technique the problem? (self taught).

Looking at something like this. How many amps do you need to weld aluminium?



(PS, tick the "disable smilies in text" - will solve your problem above)

[kool kitty89]

You might want to think of using Flux-cored arc welding. (also called "innershield welding" Uses a set-up like MIG, but uses flux cored wire without the need for sheilding gas, so the set-up is a bit simpler. You will have to chip away slag, and there's quite a bit of spatter like with stick welding though. It's also cheaper and small 110 V machines are common.

Another thing for stick welding is not only the amparage and size of rod, but also the type of rod and current. A low penetration (fast fill, or dummy rod) rtype rod (generally touched to the surface instead of held just above) will help, and make a cleaner, nicer looking weld. (and is easier to use) Also if you have a DC set-up you could use a low penetration arrangement with the ground as the - lead and the electrode +. (thus the arc will be "eating" into the sitick rather than the plate)

But neither is as good as MIG for thin plate, and MIG is also a lot better than them for stainless or aluminum welding)

MIG vs. Flux-Cored: Which Welding Process Is Right for You? | Lincoln Electric

and some welding rod info http://www.mylincolnelectric.com/Catalog/consumableseries.aspx?browse=104|2030| WELDING ELECTRODES

[buzzard]

I wish I could help you, Graeme, but I was a machinist. I played around with MIG and TIG, but the welders set it up for me, so what I wrote is pretty much the extant of my welding knowledge. It looks like KK89 would be much more help than me...

I have known a few people who bought small Mig/TIG machines, and seemed happy with them, but that was a few years ago, and I don't remember the details. Geez, I'm no help at all

Thanks for the 'disabling' info.

JL

[kool kitty89]

I took an ROP welding class my Jr year in high school (2 years ago), I mostly worked with stick arc welders (we usually just called "arc" welding, opposed to MIG or TIG). That's what I got a cirtificate for. I also got some info from my middle school shop teacher.

Also TIG set-ups tend to be expensive, and require a bit more skill to operate. (uses an arc torch held in one hand and operated with a foot pedal to heat metal, while you feed a welding rod in by hand, somewhat like gas welding, but it produses very high quality welds and can be used on almost any metal well, steels, stainless, high alloy steels, copper, nickel, magnesium, aluminum, bronze/other coper alloys)

But another thing, for welding relatively thin steel you might want to consider a gas welding (oxy-acetylene or oxy-MAPP/Propylene) which small set-ups are reasonably priced and work well on such thin metals, but it is a slower process and again requires more technique than "Arc" or MIG (or innershield). And there's the gas refill costs.



But we've gone way off topic.

[buzzard]

How about mistakes that prevented a great plane from being even better?

Udet said that the aerodynamic and weight penalty incurred by modifying the Ju88 for the dive-bomber role, made it fly like "a barn door". Considering how well it did as a 'barn door', what might it achieved without the weighty burden of the Luftwaffe dive-bomber dogma.

Kinda' ironic, given Udet's influential role in creating that obsession...

JL

[kool kitty89]

Yesit did, in fact the Ju 88 would probably have done well in a Mossie like configuration. (no defensive armament) As that added more performance and eliminated crewman lost if it went down, pluss the Ju 88's defensive armament wasn't that good anyway. (one interesting idea would be to put nose guns on it as it could probably have some opertunity to fight it's way out, being fairly agile like the Mossie, also good for strafing)

In testing the V1 (iirc) with DB 600 engines (~900 hp) managed 360 mph with internal load and guns. Another early prototype managed a sustauned 320 mph with 2000 kg external load with early Jumo 211's . The Jumo 211's of early production models making ~1,100 hp. And lets not get into the BMW 801's or later Jumo 211's.

I think the best thing would leave it as is, but probably remove the gunners and flexible mounts, imptove streamlining thusly, further improveing performance. Maybe clip the wings for added speed and better roll. (and less wingloading would still likely be allot better in this config. than it ended up with) Then there's the nose armament possibilities. (in that config it may be a more capable fighter than the Bf 110) The guns could be under the foreward fusalage as to not alter the nose and bombadier station.

The added "pet projects" also lengthened the development time of the Ju 88 and delayed production.

an overview from wikipedia:

The aircraft's first flight was made by the prototype Ju 88 V1, which bore the civil registration D-AQEN, on 21 December 1936. When it first flew, it managed about 580 km/h (360 mph) and Hermann Göring, head of the Luftwaffe was ecstatic. It was an aircraft that could finally fulfill the promise of the Schnellbomber, a high-speed bomber. The streamlined fuselage was modeled after its contemporary, the Dornier Do 17, but with fewer defensive guns because the belief still held that it could outrun late 1930s-era fighters. The fifth prototype set a 1,000 km (620 mile) closed-circuit record in March 1939, carrying a 2,000 kg (4,100 lb) payload at a speed of 517 km/h (320 mph).[3] However, by the time Luftwaffe planners had had their own "pet" features added (including dive-bombing), the Ju 88's top speed had dropped to around 450 km/h (280 mph).

But for the biggest mistake that could have advanced the jet designs and made great designs greater the cancellation of the HeS-30 (-006) engine has to be on top.


Again for an overview: Heinkel HeS 30 - Wikipedia, the free encyclopedia

The best class I engine and possibly most advanced engine to run durring the war and quite practical as well.

Realative lack for support of Heinkel's jet projects in general didn't help either, and the RLM's whole political conundrum on support for advanced designs. With some supporting it, Udet for one was very interested in Heinkels jets (though he adamently opposed the He 176 due to the dangers of rockets, well founded in light of the Me 163) In fact Udet made a deal with Heinkel that if the He 280 flew under its own power by early 1941 (april iirc) he would allow Heinkel to aquire Hirth engine company somthing other members of the RLM in combination with Messersmitt actively hindered. And the HeS 8 shouldn't have been cancelled either, and would have been further along as well without the political problems. IMO the emphesis should have been on class I desing untill they were working well in production conditions, with maybe some work on class II designs, but not more, plus many of the class I's were developing into the performance range of the Class II design. (the 004D 930 kp normal 1050 overrev; 004E 1000 kp normal 1,200 AB, and 003D 1,200 kp with much higher efficiency in this case of the 003D due to use of reaction bladed compressor like the HeS-30 used)

Hirth itsself seemed content with merging with Heinkel, and Ohain received some good help with his development there.

One good way to sum it up is

Although the RLM seemed indifferent to the He-178, the ministry was nonetheless actively pushing German industry to develop turbojets. In hindsight, it seems that the left and right hands of the RLM were not in agreement, which summarizes most of the Third Reich's attempts to develop advanced weapons.

Messerschmitt Me-262 Schwalbe / Sturmvogel

[kool kitty89]

And as said before there were similar political situations in Britain limiting development. Whittle's Power-Jets Ltd. horrible team-up with Rover delayed development (including the Metoer's) by 2-years. It also postponed the flight and subsequent testing of the E.28/39.

So much so that the Halford H.1 design (inspired by Whittle's 1930 patent, which had long since lapsed) at De Havilland which had been initiated later and at lower prioorety as a private design began to overtake the Rover developments and with 2x early prototype Halford H.1's downrated to 1,500 lbf for safety were the first engines to power the Meteor. Several months later Rover jets finally flew on a meteor. Development was so lagging that only weeks after the Rover jets flew the De havilland Spider Crab (Vampire), also originally a private lower priorety project flew with a full powered Halford H.1 engine. (capable of 2,700 lbf, a more robust but heavier redesigned H.1A, the dimentions stayed the same, and progressively the H.1B produced 3,000 lbf at 10,500 rpm on the bench)

Once Rolls Royce got with Power Jets things really took-off though.




The US had political problems too but a bit different, in the 1930's the NACA did a study on jet and rocket propulsion but by the late 1930's it was dying and they'd concluded that the most promising uses would be for assisted take-off and rockets would be preferred in that case anyway. By 1940 the study was dead. Back in the late 30's lockheed had proposed their almost insanely advanced L-133 project and L-1000 engine, but that went nowhere. (lack of intrest and we now know the basic design was impractical with the engine complex by modern standards) The engine did idle along on a low priority contract in 1942 as the XJ-37 and was built and moved around through several companies into the early 50's, but never bared any fruit. (it was a 16-stage axial flow unit wih 4 turbines)

When the US got the Whittle design in 1941 the NACA basickly got caught with it's pants down and began a new stude with a group of manufactures to work with the design, ironically the NACA own pet project for the study was a troubled and doomed ducted-fan/motorjet design known as "Jakes Jeep," the only company in the study to get anywhere was Westinghouse which resulted in the 10-stage axial-flow 19 in diameter 1,600 lbf ~660 lb J30 tested in 1944, and the post war J34.

Simultaneously GE was working on the Whittle design, and were gaining ground over the troubled Rover arragement, and 1,250 lbf I-A (development of W.1) engines were flown on the XP-59A in october of 1942 ~2.5 months after the Me 262's first sucessful jet powered flight and 5 months before the Meteor's with Halford engines. The I-A gave way to the I-14 used on later XP-59A's and then the I-16 which became the J31 producing 1,600-2,000 lbf. A further development of the Whittle design of course resulting in the 4,000 lbf I-40 becoming J33 being moved to Allison for production. And GE was working on it's own original designs, notably the TG-100 turboprop developed into the TG-180 turbojet becoming the J-35 produced again mainly by Allison.



And while the XP-59 program didn't suffer the same kind of political problems as the British or German a/c it nevertheless was lrestricted by outside limitations. While Gen. "Hap" Arnold was generally a huge boost to the US jet program and the procurment of the Whittle engine he made some decisions that were some of the main reasons for the P-59's poor performance. In order to maintan secrecy he forbit any cooperation with or advice form the NACA or use of wind tunnels. Eventually allowing limited use of low speed tunnel (at Wright field iirc). This resulted in poor streamlining ad particularly problems with the intakes and nacelle-wing interaction. Little data on the engine was availableto Bell either resulting in a very conservative and overengeneered design. With oversized (45.5 ft span 386 ft^2 area) fairly thick as well with 14% at root 12 at tip, in production versions which had clipped wingtips the 14% was constant. (compared to 12.5 at root and 10% at tip for the Meteor I with a 376 ft^2~43' span wing at 13,780 lbs loaded) albeit it was a laminar flow wing. And for a fairly light aircraft at 10,800 lbs loaded the wing loading was ~28 lbs/ft^2, that's comparable to the Hurricane IIB!

But one thing's for sure the P-59A was not underpowered compared to its contemporaries, at ~10,800 with 2x 2,000 lbf J31-GE-5 engines giving it a thrust/weight of .37. (higher than the He 162 with overrev, or the He 280 with 004 engines)

The prototypes powered by the 1,250 lbf I-A's would have been underpowered, less so with the 1,400 lbf I-14's and similar to contemporaries with 1,650 lbf.

[Graeme]

Originally Posted by buzzard

I have known a few people who bought small Mig/TIG machines, and seemed happy with them

Originally Posted by kool kitty89

you might want to consider a gas welding (oxy-acetylene or oxy-MAPP/Propylene) which small set-ups are reasonably priced and work well on such thin metals

Thanks for your advice gentlemen.

[kool kitty89]

And I'm pretty sure the large wings of the P-59, in addition to the conservative and unrefined design, was to allow a high ceiling. It was aimed at (and invisioned by Whittle's original concept) to cruise at 500 mph at 50,000 ft. Ironically the wing proved to have too low of a mach limit to allow this, with a very narrow margin between shock stall and normal stall above 46,000 ft. It did manage to set an unofficial altitude record of 47600 ft.

[Waynos]

I think one major mistake in WW2 was Heinkel NOT following Avro's example and replacing the coupled engines of the He 177 with 4 individual engines as in the Manchester - Lancaster.

This would have yielded a strategic bomber that actually worked for the Luftwaffe. Also, who's idea was it to make the He 177 a dive bomber anyway?

[DerAdlerIstGelandet]

Heinkel did not have a choice. They were told to develop the aircraft as a dive bomber by the RLM.

If they had developed the aircraft with 4 single engines it would not have been capable of divebombing.

[Waynos]

Interesting. How did the coupled engines affect this?

The He 177 and the Avro Manchester are quite similar in philosophy (there was a requirement for the Manchester to be capable of dive bombing too but this was 'relaxed' quite early on). When you look at how this evolved into the Lancaster it has to be said that Heinkel (ok then, the RLM really, Heinkel were no fools) missed a trick.

[DerAdlerIstGelandet]

My understanding is that oil and grease build up would catch fire easier in these configurations.

[Waynos]

Never heard that before, but I'm no engineer. Thank you, something new for me to look into