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Thruster Bob

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  • Aircraft
    Thruster T500
  • Location
    Maitland
  • Country
    Australia

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  1. Hi Kyle, I've been out of touch a bit. I didn't think Malta had enough flat space to have airstrips? Re struts, We don't have a factory as such anymore over here, I think Thruster Australia may be still be operating out of Evans Head?. TOSG has pretty much faded away now, otherwise the guys at Watts Bridge would have helped you out. Are the machined ends of the struts OK? If so then you just need to replace the aluminium tube , it will probably be an inch size. Any aircraft engineer could replace the tube. Although it needs to be anodised , so thats an extra cost. Cheers, BobT
  2. Holbrook: The trampoline of airports! Odd you should mention Holbrook, I'd only done wheelers during training and was pretty hopeless at them , but I normally use three pointers all the time. Then went to a fly-in at Holbrook, thought I'd do a wheeler, and did two huge bounces to the accolades of hundreds of onlookers!!! So embarrassing! Pud has a good point re tail wheels (and damage to them), after landing a three pointer, I'd pick up the tail pretty much straight away and do a tail up taxi all the way back (except with tail-winds) until I was ready to park. I think of the tail wheel as a handbrake, use it only when needed. It would be nice to be able to do a wheeler, and then gradually transition to a tail-high taxi, I've done this with Keith's thruster (with the stiff springs) , but mine has the big soft springs. The other point is , it's my suspicion that most Thruster three-pointers actually happen with the tail wheel about six inches to a foot off the ground when the mains contact, then the tail contacts a fraction of a second later (The angle of incidence suggests it has to happen this way too), you'd need to do a beach landing and use a tape measure to be sure. Yet another thing, you need to keep the wings level with your feet during a three-pointer, my suspicion is those pilots who have trouble flying at high angle of attack where the controls get all mixed up, non-linear and crossed over will have difficulty doing anything but a wheeler. Cheers, BobT
  3. Hi Pud , Looked at them on the weekend, My ends are good, there's a few spots of pitting corrosion (must be pinholes in the clear coating?) Cheers, BobT
  4. More on Strut Attachment & info on intergranular corrosion Hi Pud. I'm speculating the parts are made from 2024 alloy. (Based on your observations and mine of the powdery white corrosion) It's usually known as "machining grade". It has abysmal corrosion performance, even sitting on the metal rack in the shed it gets covered in a white frost. Given the operating conditions, a 606x alloy would have been a much better choice for this part (or even marine grade 5052 alloy). I think the original designers were led astray by the appeal of the higher UTS (60,000psi) of the 2024 vs ~40,000 & 30,000 psi for the other grades. --------------- Ok My machinery handbook says 2024 is prone to intergranular corrosion, so I google it up Intergranular corrosion - Wikipedia, the free encyclopedia and in Paragraph 5 it says aluminium alloys with copper (=2024) are subject to exfoliation corrosion, resulting in leafing or lifting effect , which pretty much describes the photos in the AD. A few more similar links: Intergranular corrosion Different Types of Corrosion: Intergranular Corrosion - Causes and Prevention Different Types of Corrosion: Exfoliation or Layer Corrosion - Causes and Prevention http://canteach.candu.org/library/20053207.pdf Metal Improvement | Exfoliation Corrosion (the above suggests cadmium plated fasteners may be implicated) Exfoliation Corrosion - JAMWiki and a tutorial on aluminium grades: Argentum Solutions Inc. - Sterling Guidance on Corrosion and Materials Degradation -------------------------------- Interestingly enough Austenitic stainless steel is subject intergranular corrosion after welding. This goes part of the way to explaining the failures on the other half of the wing attachment, where the TIG welded parts have the end of the weld (= stress raiser) near the high stress bend. Perhaps the whole thruster wing attachment method might be a good example of "how not to design something" for an engineering class. Cheers, BobT
  5. Hmm , Looks like the same part on the T500. I'll check it out next time. Looks like the fault is due to material defect in the aluminium alloy bar used to make the parts. (some kind of inclusion. like a "cold shut" ). "Cold Shut 2 (1) A discontinuity that appears on the surface of cast metal as a result of two streams of liquid meeting and failing to unite. (2) A portion of the surface of a forging that is separated, in part, from the main body of metal by oxide. " I wouldn't think this kind of defect would exist in extruded material though?. Thruster UK needs to trace back through their QC records to identify the batch and supplier of the alloy. Then ensure all the parts made from this batch are recalled and destroyed. The parts in the photo look like they are anodized, so I'm guessing that the acid used during the anodizing process leached into the edge of the defect, so in conjunction with atmospheric moisture this acid would slowly work its way through the length of the defect. Creating a small electrochemical cell between the oxide of the inclusion and the parent metal. Hopefully all the Aussie thrusters won't suffer from this as their parts would be made from a completely different batch made a decade earlier in a completely different factory. BTW (a long time ago) after I cleaned the surface white powder off my wing attachments, I polished them and sprayed them with clear lacquer. The offer of a 15% discount on replacements is a bit cheeky , the parts would have been defective "as supplied" by the manufacturer, and "unfit for purpose" and should be replaced free of charge. Seems the UK laws on trade practices are softer than in Australia. Cheers , Bob T
  6. Hi all, My vote is for three wheelers, It's what I've always done in my Thruster. I can do them on dirt, grass, sand, bitumen in upto 20kts headwind and 15kts sidewind. My worst landings have been my attempts at wheelers! I have the long, soft springs and some say this makes it more prone to bouncing/ballooning. Its helpful to have a quick hand on the throttle, as you will sometimes benefit from a little extra power, especially with Pax and full fuel. To do a dead-stick three-pointer can be quite tricky, as you need to arrange to have the right combination of vertical and horizontal speed (i.e. you need to be fairly fast, if you just waffle in you won't have energy to arrest your descent, and risk ploughing through a compression stall just before you hit the ground) Cheers , Bob T
  7. Thruster Bob

    trailering

    Hi Rocket Driver. I'm someone who has built their own trailer. It tows backwards, the basic frame is like a boat trailer (Mine is registered as a boat trailer, It's 180kg empty) , and the thruster wheels sit on pads behind the mudguards. The wings mount beside the fuselage (with skins still on) they are bolted to the trailer frame using the existing brackets on the wing spars. You need to take the elevators off, and put them in the vehicle. You should ideally take the propellor off , or a low hanging tree will do the job for you. The only problem with my trailer is the bottom of the fuselage scrapes on a trailer cross member when unloading. The trailer has done several thousand kilometres, the only mishap was a lost mudguard courtesy of a kangaroo. I've attached a pdf of the original drawings (these are like 15yrs old now!) If that's of some help. The trailer and airplane are currently in the shed if you need some photos. It takes about two hours to dissassemble/reassemble if you have three skilled people doing it. About half a day if it just yourself and your wife. Cheers, BobT thruster trailer.pdf thruster trailer.pdf thruster trailer.pdf
  8. Bob...I just saw a photo of your beautiful blue Thruster...I am in love Bob.
  9. Trailering : Best way to get your new plane home Oops, Thanks Tony for pointing out my omission. One of the most obvious reasons for trailering it is on aircraft acquisition. Having a new pilot fly an unfamiliar (and most likely dodgy) aircraft long distance is a recipe for disaster. You should assume if you buy an aircraft from anyone but Tony, that it almost certainly has one or two minor irregularities, which can be hazardous in all but the most competent pilots hands. Most aircraft accidents are not caused by a single factor, but a combination of individual factors, each of which is manageable individually. An unfamiliar aircraft in an unfamiliar location already has two factors stacked up, toss in some equipment failures, a bit of illness, failing light, low cloud, fuel, a missing map... suddenly all the holes line up on your pieces of swiss cheese. The moral here, as is Tony's war story is always to have a backup, other options, a spare, redundancy, an alternative, plan B, an alternate strip, he was lucky enough to have a spare pilot! I bought my aircraft as a complete aircraft, but with "some assembly required" from the Thruster "Factory", I modified an 8x5 trailer to pick it up. I hadn't finished my license by this stage. But the reason I built the trailer was to take the Thruster up to my family in Mackay over Christmas. I actually passed my license and passenger endorsement about 2 weeks before the first trip to Mackay, I didn't have a X-country endorsement at that stage anyway. So I based myself just north of Mackay and flew around for a couple of weeks from there just honing my "aviating" skills. You really need to build up a lot of experience before undertaking any kind of epic adventure. A year later I went up again by trailer, and with considerably more experience under my belt, this time we went as far as Hamilton Island (including a 5 mile overwater leg) This time we were mixing it with 767's into Proserpine, and the really windy Whitsunday strip, and finally flying into the Control Zone on Hamilton, with an interesting landing and takeoff on a 3km bitumen strip in 15 gusting 20kts, with some really interesting orographic wind flows. (On takeoff we were at 2000' before the end of the runway). So in summary, I had some 6000km of trailer miles, before I went on my epic adventure (7000km Red Nose round trip) and even then I did it in company. (But I think I'm crossing over to the other topic!) As far as trailer balance goes I think mine is about 5% on the towbar, and a bit more with full jerrycans, RTA recommend around 10%, and I'd agree with that. It's easy enough to push it around with a jockey wheel (But always remember to completely remove the jockey wheel and carry it in the boot!). My previous experience with towing trailers is that having a low c.g. and wide track yields good stability, and that's what I built into the trailer. Soft springs tend to destabilise the trailer. Standard leaf springs with rear shackles add stability, novel suspension types should generally be avoided. Cheers, bobT
  10. Trailer with assembled wings Hi Guys, I scratchbuilt a trailer to carry my Thruster, and it carried the wings fully assembled. Each wing bolts to an approx 4ft square rectangular frame of 1" RHS, using the standard wing attachment points. Each of these rectangular frames is pivoted where it attaches to the trailer, so the wing can go from horizontal for attachment to aircraft, to just past vertical for stowage on the trailer. The horizontal position has the wings at the same height as the aircraft so in theory one can just wheel up the fuselage and attach a wing,( in practice it is nearly impossible). In the stowed position there are shaped wooden blocks with padding to support the wing ends. I added a small jib which could swing out and support the weight of the wing during assembly, but it never worked properly and I removed it later. The wings are stowed leading edge down, bottom face to the outside. The fuselage is towed tail first, with the rudder and tailplane attached, and the rudder locked with padded clamps. The towball is 200mm horizontally in front of the back of the rudder, the trailer main frame is two 50mm RHS at 1800mm apart, and the rest of the skeletal frame is 25mm RHS and triangulated everywhere (i.e. a space frame) as a result the entire frame is rigid, so there is no twisting or bending which would cause rubbing of the wings, the Thruster is securely bolted to the frame at the tops of the springs, so everything is one big stiff structure. The propellor boss overhangs the trailing ends of the wings by ~ 200mm The lights and number plate are mounted on a duckboard, which attaches to the wing ends at the rear, so technically there is no overhang. It was registered in NSW as a "boat trailer" in about 1994, they had no issue except wanting longer mudflaps. The springs were really long and soft automotive leaf springs. It's nearly 8'wide (2250mm), with a hollow axle. It could be made narrower, but I have the wide wheelbase (2200mm) Thruster anyway. I screwed tarpaulin studs (like they use on utes) to the frame, and fitted a shaped tarpaulin front end. You can't tow it with a tarpaulin over the whole thing as it flaps a lot. I've never had issues with crosswind towing or speed wobbles upto 110km/hr. I've used it to drag the Thruster upto Mackay from Newcastle on two occasions, so that's 6,400 kilometers total on long trips, plus several local trips. Only issues were (a) bent mudguard due kangaroo (b) cracked welding around mudguard- added braces © fuel consumption (d) finding big enough parking spaces (e) nowhere to put the elevator, propellor, toolboxes and other paraphenalia Given the extra effort required in handling the assembled wings, and the careful choreography to get the fuselage onto the trailer I don't think there is much benefit compared to racking the wings on the "universal trailer" (I still have to remove ~ 10 battens anyway to accommodate the cockpit width). If you were to make a sufficiently large fully enclosed trailer, then you could carry the wings fully assembled. But the trailer would be the size of a large caravan, this may be a viable option where you are using the trailer instead of a hangar for storage. The wings & fuselage would fit together better (i.e. narrower trailer) if the wings are carried leading edge up, but it would be difficult to support the weight on the flap edge, and the prospect of damaging the flaps through handling is always an issue. From my experience the only reasons you would use a trailer are (a) as a cheaper alternative to hangarage (b) to recover a damaged aircraft. In my opinion, for long distance travel the best approach is with two aircraft and one large ground vehicle, and do it as a two family holiday. Cheers, BobT
  11. its all greek to me! Ah.. a common mistake translating the ancient Greek text to English : ο βρυχηθμός του θριάμβου του. has been mistranslated from το κουδούνισμα του θριάμβου του it should have read "The rattle of his Triumph could be heard through the streets of Jeruselem" Now we're talking legendry British workmanship!
  12. Yea therily It also mentions something about anointing with oil , so they were definately Trumpys!
  13. another Mustang I was hanging out for Beaver, but I'm another Mustang! You are a P-51 MUSTANG. You enjoy classic things. You like the beauty of old machinery, and the way that it awed the world. You love adventure, and you like being top dawg. You are powerful, and you are determined. You see qualities in things that most people do not. So buckle your seat belt and tear up the skies, it's your turn to have some fun!! BobT
  14. Thruster flight to Cape York for red nose day Hi Guys, In 1995 I did a fund raising trip to Cape York for Red Nose day (in my little blue Thruster with a red nose painted on). I should scan in the photos and upload them. We started in Newcastle and flew to Boonah to join up with the other 5 ultralights. We officially started the flight from Amberley AFB , then we went up to Cooktown inland then onto Weipa, then just two aircraft went up to the tip. ( I planned on going to the tip of Cape York, but lost an exhaust spring, and punctured a tyre on departure from Coen, so stopped at Weipa for a pit stop). We came back along the coast, and intended to drop in at Watts Bridge on the way back, but got socked in at Noosa (we had some marginal VFR on the coastal segments). Some very long days in there! I fitted a C172 bladder tank into the wing, for a total fuel capacity of 90litres, or 4 hrs + reserve. I've flown longer safaris in C172 and C182's but the Thruster trip was the most fun. Lots of fun times, plus we raised $20,000+ for a worthy cause. Cheers BobT
  15. Thruster Bob

    wheel base

    Mine measures 2200mm (no wings, on trailer) Hi Fly, Just ran down the shed and measured mine, it's a T500 (25-0294) . I have the long floppy springs. Wheelbase outer edge to outer edge of tyre is 2200mm, when on the trailer , this is with 6" wide tyres (Kenda 15x600-6) on aluminium rims . (I think I got my wheels from Airborne here in Newcastle, they are fairly standard aircraft tyres). The measurement would be slightly wider sitting on the ground, with wings attached, and fuel in the tank, (after pushing the aircraft forward a bit), probably close to your 2300mm then. I'm guessing we have the same springs. I originally welded some squares of angle onto a 5x8 tandem trailer to pick up the aircraft when first purchased. Then I built a custom trailer to carry it. Went to take the Thruster home a couple of years ago (after Cooranbong airport closed:crying:), and forgotten I had put wheel pants on ! Had to take them off before getting it onto the trailer again aargh !!! Originally my springs had sagged, and I took them to Dumbrells springworks, and they annealed them, re-bent them, and hardened them. As Tony says, there's nothing special about the springs, and the springmakers can make you a custom set to suit your preferences (and to a better standard than most of the Thruster OEM springs.) The axle bolts used by the "factory":clown: can be dodgy too, and the hole in the spring they attach through can be malformed, you may need to file the faces flat and deburr the edges of the hole (need to anneal the springs first). Check where the springs bolt onto the rectangular through beam too, if this connection is not rigid (ie the springs rock back and forth) then you may get fatigue failure on these bolts. Cheers, BobT PS I've uploaded some pictures, so you can see if yours looks the same front on, just click on "Thruster Bob" on the left side, select "view profile" and click on "album" , I've also uploaded a picture to the Thruster section of the gallery.
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