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Post by smithy1 on Feb 17, 2021 23:52:29 GMT -5
That Jet Joe starter clutch is tiny....and used on microjets....I have a few of them at home. They use an O-ring internally to "grab" the compressor nut. Smithy..
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Post by smithy1 on Sept 17, 2020 0:07:05 GMT -5
Hi All, Is there a reason other than simplicity that all DIY/Hobby-scale turbines have separate battery powered accessories rather than driven accessories? I understand that at small scale and high rpm radial power take off shafts would not be practical, but surely concentric/epicyclic gearing could be used to distribute power from the rotor to a gear driven oil/fuel pump and a starter/generator? Something similar to as found in APU's. I have a vague idea to build something 'self contained' if you like.. Thanks Will I think the main reason they don't is simplicity and cost.....the cost of doing so would outweigh the possible benefits. Plus....some of these little RC engines are capable of ~1/4 million rpm, so a little gear train hanging off anything spinning that fast would have to be engineered to perfection and have a lube supply to go with it. Not easy to do. A separate starter and electric fuel pump is relatively easy. Smithy.
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Post by smithy1 on Sept 9, 2020 19:11:52 GMT -5
Wave washers...(which are basically just another form of spring), are a common way to do it in the RC turbines...works really well too. They're able to keep a nice constant load over a wide range of temps whilst still allowing for expansion.
Smithy.
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Post by smithy1 on Sept 2, 2020 0:01:26 GMT -5
I tried a diesel glow plug a few years back, unfortunately I think the air flow over the glow plug where I had it was sufficient to cause it to cool down somewhat, it did light off more often than not but was quite unpredictable and made for some "exciting" starts...I now use a proper aircraft igniter and propane to light off....it's idiot proof and works every time.
You may have more success if you dribble liquid fuel over the glow plug during start like they do in smaller RC turbines, they're very reliable these days and always start "soft". I'm actually playing with the idea myself as I'm now a bit tired of carting an LPG bottle around with me.
Smithy.
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Post by smithy1 on Jul 12, 2020 1:29:14 GMT -5
Thanks chaps. Seperate pump now ordered..! Just ordering the bits now for the brackets to support the weight of the A/B. Am I missing a trick with the spark plug - IE do I really have to run a second coil and all the electronics or can I Tee off the existing one some how.... I kind of left some provision for this in the build but not enough.. doh. Yep, definitely a second pump...my engine actually has 4 fuel pumps.. one high pressure pump, (1000psi+), for the engine injector itself, two Bosch 044's for the A/B feed and a separate pump for the hot streak to light the A/B...l found spark ignition for the A/B was too unreliable, the hot streak works every time. Smithy.
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Post by smithy1 on Mar 17, 2020 20:44:01 GMT -5
Looking to produce thrust more than 10kgf With a tiny 40mm inducer you'll struggle to get 10kgf of thrust....also, there's not much difference between LPG and kerosene with regards thrust. Smithy.
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Post by smithy1 on Feb 3, 2020 18:36:38 GMT -5
Smithy, would it be possible to buy a 3rd stage? Ive been watching Ebay but have only been able to find recon'd ones. The ones I get probably aren't any better to be honest...they're usually "Time or Cycle Expired" but are fine for our purposes. I don't know what reconditioned really means, they aren't allowed to "re-life" them as they have an absolute life limit. All going well I should have some in the not too distant future. Smithy.
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Post by smithy1 on Jan 22, 2020 21:39:25 GMT -5
John....I may have a couple of time expired C30/C47 3rd & 4th wheels in the next month or so...we've got a couple going through the shop as we speak....if I can get hold of them....would you like them..??
Smithy.
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Post by smithy1 on Dec 18, 2019 18:58:00 GMT -5
How do I find psi from the compressor map? I apologize as I am new to this.. Thanks John I think you need to go back to basics before actually starting to build anything.....knowledge is the answer....John (Rackets) gave you all the info required and links to that info... but you chose not to use it. If you follow his advice you'll not go wrong. Smithy.
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Post by smithy1 on Oct 25, 2019 16:10:01 GMT -5
Hi John, I had a fumble around in my shed, l have 3 x 3rd stage C20 wheels and 2 x 4th stage C20 wheels on hand....no series 4 wheels at the moment, but that could change soon as we get quite a lot of C30/C40/C47 engines coming through the shop. Many of the customers ask for their time x wheels back, the rest are destroyed and disposed of. I need to get hold of the ones that will be disposed of before they're destroyed.
Smithy.
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Post by smithy1 on Oct 22, 2019 0:36:01 GMT -5
Curious, if your running your jet turbine in demo or exhibition (fire, smoke, noise), do any of you carry some sort of insurance for liability should something go wrong or some idiot does something he/she shouldn't be doing around, associated to the turbine? These days, everyone want to sue for something and even though we all know we practice safety, something could inadvertently happen.... thoughts on this? I am here in the USA. Sorry for the late reply... Yes, I have a turbine powered afterburning 1/4 scale Jet Dragster and turbine-A/B Go-Kart and do a lot of static engine runs at car shows, air shows and similar here in Australia, John and I did a small demonstration together at a Go-kart track a year or two back where he also ran his beast of an engine, was a good day. I have 20mill public liability insurance in case something silly happens. Have been doing this sort of thing for quite a few years now. I find it difficult to explain to people that our turbines are inherently safer with basically a single moving/rotating part than reciprocating piston engines with their many rotating/reciprocating bits...! It's pretty much mandatory to have P/L insurance these days if you plan on doing this sort of thing. A lot of shows where the public/spectators pay to enter will ask for a P/L certificate, but I essentially have it for peace of mind. Smithy.
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Post by smithy1 on Oct 22, 2019 0:19:42 GMT -5
Hi Mark Yep , she cracked roughly half the blades , no spare , so thinking of fitting a "common" 4th stage C20 wheel , just a case of sleeving the shroud to fit the smaller diameter wheel . Cheers John I have a 4th stage C20 wheel too if that is preferred..?? Also a 3rd stage C20 wheel IIRC... I'll have a fumble around in my "new shed". Smithy.
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Post by smithy1 on Oct 21, 2019 22:25:07 GMT -5
John, I may have a 4th stage C30/C47 wheel floating around.
Smithy.
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Post by smithy1 on Oct 21, 2019 18:42:14 GMT -5
She's certainly looking rather heavy, what's the intended top speed..?? Smithy. The current weight, as it sits in the picture, dry and with 95% of components fitted is 95 kg, so not too bad. Remember with it running on rails we have a contact patch of metal to metal about the size of a dime and pretty much nil friction. If you push it with your finger it will roll the length of the workshop. Top speed TBC.... Well that's a lot lighter than I expected....well done Sir..! Smithy.
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Post by smithy1 on Oct 6, 2019 21:25:07 GMT -5
She's certainly looking rather heavy, what's the intended top speed..??
Smithy.
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