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Post by jetjeff on Nov 29, 2016 18:15:46 GMT -5
Hi All,
I've decided to build another Schreckling turbine based on the Heineken mini keg case. I've ordered several plates (1" x 7" x 7") of magnesium in an attempt to reduce the overall weight even further. Reason being, I've had the most positive results using the Schreckling design.
Not sure if I've abandoned the carbon fiber compressor, at least I know how it won't work,,,lol.
Not sure if I'll use the magnesium as a compressor diffuser (was thinking of using Delrin), , compressor or the compressor sleeve i made previously out of aluminum.
Machining magnesium will prove interesting as i've never worked with the material before.
Regards
Jeff
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Post by smithy1 on Nov 30, 2016 16:24:48 GMT -5
Hi Jeff, I think you'll find magnesium may not handle the loads too well and will easily suffer from corrosion if not treated correctly, it's good for lightweight gearbox cases etc...but I've not seen a comp wheel made of it..! Although, they did make car wheels with it years ago...Hence the name.."Mag Wheels".
Cheers, Smithy.
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dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
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Post by dieselguy86 on Nov 30, 2016 18:32:02 GMT -5
Have you ran any of your engines?
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Post by jetjeff on Dec 1, 2016 4:52:52 GMT -5
Hi Smithy,
The Fairchild J-44 used a cast diagonal impeller from magnesium. I think the impeller diffusor was magnesium too. But, I do agree about the ability to handle loads. There are several alloys of magnesium with different tempers/strengths, similar to the various grade of aluminum. I ordered the magnesium from Source 1 Metals.
I'd like to machine the impeller diffuser out of black Delrin, for it's ability to absorb vibration and weight saving too. I like to think outside the box, maybe too much so,,,lol.
Diesel Guy,
Yes, I've posted several short videos in my Old + New build thread.
Elektron AZ31B Sheet, Plate & Coil AZ31B is a wrought magnesium base alloy with good room-temperature strength and ductility combined with corrosion resistance and weldability. Increased strength is obtained by strain hardening with a subsequent partial anneal (H24 and H26 tempers). APPLICATIONS Sheet and plate in AZ31B find application in medium strength service at temperatures below 150°C. Diverse uses including aircraft fuselage, concrete tools, cell phone/camera/notebook computer cases, speaker cones and textile machinery can all benefit from light weight AZ31B. AZ31B is non-magnetic and has high electrical and thermal conductivity filling the requirements for RFI and EMI shielding in the electronics and computer industries. Superplastic forming of AZ31B sheet at elevated temperatures allows production of a wide variety of intricate parts for automotive uses. Monocoque construction utilizing formed sheet can be adapted to many commercial applications. SPECIFICATIONS UNS No. M11311 AMS 4375 AMS 4376 AMS 4377 AMS 4382 ASTM B90 CHEMICAL COMPOSITION Aluminum 2.5-3.5% Zinc 0.7-1.3% Manganese 0.20-1.0% Magnesium Balance PHYSICAL PROPERTIES Specific gravity Coefficient of thermal expansion Specific heat Thermal conductivity 76.9 Wm-1K-1 AZ31B-H26 12.7-25mm Electrical resistivity 92 nΩm OTHER PROPERTIES TYPICAL HARDNESS O temper H24 temper WELDABILITY HEAT TREATMENT No thermal treatment is available for increasing the strength of this alloy after fabrication. DESIGN DATA Specification minimum tensile properties. 67 Rockwell E 83 Rockwell E AZ31B-O 0.5-1.5mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-O 1.5-6.3mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-O 6.3-75mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-H24 0.5-6.3mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-H24 6.3-9.5mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-H24 9.5-12.7mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-H24 12.7-25mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-H24 25-50mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A AZ31B-H24 50-75mm 0.2% Proof Stress Tensile Strength Elongation in 5.65√A 125MPa 220MPa 10% 105MPa 220MPa 10% 105MPa 220MPa 8% 200MPa 270MPa 5% 180MPa 260MPa 7% 165MPa 255MPa 7% 150MPa 245MPa 7% 135MPa 235MPa 7% 125MPa 235MPa 7% 180MPa 260MPa 5% 160MPa 255MPa 5% 145MPa 240MPa 5% Excellent weldability with gasshielded arc using AZ61A (preferred) or AZ92A filler rod; post weld stress relief is required to prevent stress corrosion cracking. Resistance welding is excellent. MACHINING AZ31B, like all magnesium alloy sheet and plate, machines faster than any other metal. Providing the geometry of the part allows, the limiting factor is the power and speed of the machine rather than the quality of the tool material. The power required per cubic centimeter of metal removed varies from 9 to 14 watts per minute depending on machining operation. DENT RESISTANCE Weight for weight, AZ31B-H24 has proven to be superior to competitive materials in its resistance to denting at moderate energy levels. Dent Resistance of 1mm Gauge Sheet Dent depth in mm from 25mm spherical radius indentor on 350mm span Impact Energy 0.34 J Impact Energy 0.62 J Impact Energy 1.25 J AZ31B-H24 6061-T6 3003-H14 5052-H34 2024-T6 SAE 1010 Mild Steel 0.66 0.94 2.24 1.55 0.99 1.09 1.42 1.52 3.23 2.41 1.52 1.70 2.34 2.46 4.90 3.35 2.29 2.67 1.78 Modulus of elasticity 45x109 Pa Poissons ratio 0.35 Melting range 566-632°C AZ31B-H26 6.3-12.7mm SURFACE TREATMENT All the normal chromating, anodizing, plating, and finishing treatments are readily applicable. AZ31B also
Jeff
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Dec 1, 2016 5:36:48 GMT -5
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Post by jetjeff on Dec 3, 2016 3:47:21 GMT -5
Hi BFTO, From the book "Turbojet history and development 1930-1960 Volume 2, they say it was cast as one piece, although it does look like Fairchild anodized half of it. Here are some pics of my current build. Regards Jeff
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Adam
Veteran Member
Joined: May 2016
Posts: 101
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Post by Adam on Dec 4, 2016 2:02:44 GMT -5
Hi Jeff,
looking good. How did you cut those curved slots for ngv? did you use a grouned down hacksaw blade?
Regards Adam
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Post by jetjeff on Dec 4, 2016 2:59:25 GMT -5
Hi Adam,
Yep, used the ground down hacksaw blade (use a fine blade 32 teeth per inch). Grind the 1/2" width blade down to about 1/4" (grind the blade so it cuts on the pull stroke not push). I used 13 blades for this NGV.
I use my rotary turntable to mark the exact spots the blades should be and mark the inner ring with with a red paint marker installed in a 1/2" collet on my Bridgeport. The inner ring is painted with Dykem blue layout fluid and I use an aluminum template to scribe the curved slot. Using this method produces the entry angle of 65 degrees and exit angle of 30 degrees pretty much spot on (per the Kamps plans).
The entry cut is made with a normal hacksaw, then I switch to the modified one. With the inner ring clamped in a vise stand directly over the piece, keep your hands close to your body and pull up. The first few pull cuts will be difficult as you're "transitioning" between a slanted saw kerf to a straight one. I'm not going to lie, making the inner ring is a bitch. Use WD-40 as a cutting lubricant.
A hacksaw blade kerf is .025"-.030", I use old cloth belt sander belts cut into 1/4" wide strips to enlarge the slots slightly to .035" slots.
I've made NGV's using .050" blades and was able to machine the blades to fit into the outer ring with no problem, using 035" thick blades, you'll find you'll bend the blades trying to machine them. I've heard of folks using Bondo to temporarily support the blades for machining. The other option is to use a tool post grinder to face the blades to fit the outer ring
Hope this helps.
Regards
Jeff
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Post by jetjeff on Dec 4, 2016 4:23:39 GMT -5
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Post by jetjeff on Dec 4, 2016 4:40:45 GMT -5
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Post by jetjeff on Dec 4, 2016 6:19:02 GMT -5
Hi Adam, Stand like this when you cut the slots. Not trying to be overly simplistic, just sharing what worked for me. You'll have to apply constant "torque" to the hacksaw to get it to follow the curve. Remember to number each slot and blade, as you have to bend each blade to match each slot. Regards Jeff
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Post by jetjeff on Dec 4, 2016 14:16:09 GMT -5
Hi All I cobbled together a short how to video on installing the blades on a Kamps style NGV. youtu.be/i5oXyNCgaowRegards Jeff
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Adam
Veteran Member
Joined: May 2016
Posts: 101
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Post by Adam on Dec 4, 2016 16:49:56 GMT -5
Hi Jeff,
Thanks very much for such a detailed explanation. The pictures and video are really helpful. The inner ring I was planning to use is about 1 mm dia smaller than the diameter at the base of the blades on Smithy's turbine wheel, so I'll have to make a ring from some sheet first.
Regards Adam
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Post by jetjeff on Dec 4, 2016 17:37:37 GMT -5
Hi Adam, No problem, I'm here to help. For such a simple design on paper, with only a handful of components, turbines are VERY difficult to build with the accuracy required to get them to run properly.
I'm not sure if somebody offering laser cutting services, could cut the curved slots, just a thought.
Regards
Jeff
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lofi
Member
Joined: October 2014
Posts: 47
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Post by lofi on Dec 4, 2016 19:04:35 GMT -5
Lovely work! I'd be tempted to try getting it cut in flat by a laser service, but leave a couple of mm on what would normally be the open ends of the slots uncut, roll it, weld the join and dress, then slit out the end few mm of the slots with a mini slitting disk. Would probably need a slanted join in the middle of two blades, but shouldn't be difficult to design. I'm waiting for OnShape to release their sheet metal functionality so I can design in 3D and unwrap to how the flat sheet needs to be cut. Solidworks does this already, but I can't afford it. OnShape is free I have seen tubular laser cutting done, but never looked into whether it's something available to the hobbyist. Flat sheet seems quite easy and reasonably priced to get cut. Love the old school craftsmanship, though! Cheers Ian
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