ausjet
Veteran Member
Joined: May 2013
Posts: 133
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Post by ausjet on Jun 1, 2021 4:42:12 GMT -5
I made my flame tube out of a 7” fire extinguisher cut in half. It was a perfect size for my build. Plus they’re stainless, 1.6mm thick I think and are built with a domed end cap. All that’s needed is to drill your holes and fabricate a cone on the bottom section to funnel the gasses into the turbine housing.
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Post by turbojet atv on Jun 1, 2021 6:43:57 GMT -5
Hi John, that’s interesting to hear that I’d only need a single injector for my size engine. I’d assume it’d be a 20ish gph injector? also check out this gem I picked up for my puzzle ibb.co/HN9ncM4ibb.co/SBKc7CTibb.co/VSyPHxhstill learning how to post full size pics but this is a Honeywell air turbine starter off of a JT8D engine. It came with its shut off valve so that’s a plus for me. construction on the combustion chamber has begun as I got every piece I need to build the engine now. -Cullen This will be a interesting build I'm sure you will machine up a output shaft support to take up side loads I did on my cartridge starter, some photos here not finish yet but may give you a idea. Cheers, Mark. That looks nice mark, I’m thinking of doing something close to that to keep the starter from flexing under a load. I’m going to draw up how I want it to look under my subframe once I get my engine completed. Did you use an aluminum block and mill it to fit your starter? I was going to weld a “cage” around mine to hold it up and keep it from flexing. -Cullen
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Post by pitciblackscotland on Jun 1, 2021 8:32:03 GMT -5
Hi Cullen, Yeah it was a block of aluminum i got from the scrap guy, need to machine a grove to take a V band clamp to hold that block of aluminum and extend the output shaft and press a bearing in the center hole. If you have room you could use a pillow bearing set up like Dave has done with the JFS 100 www.youtube.com/watch?v=hWNnjIWkhk8&t=23sCheers, Mark.
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Post by turbojet atv on Jun 5, 2021 18:27:12 GMT -5
Hi everyone, I just wanted to post an update on the progress of my engine. I just got done plasma cutting my end caps & got my bolt ring done. ibb.co/XtKR9K2I’ve got: a 18mm turbo end cap, a 12mm injector end cap & a bolt ring with 16x 3/8” bolts. Trying to get all that cleaned up so I can weld it all together and then weld on the 8-3.5” exhaust to the turbo. ive also been reading up on this turbine starter. Gathering all the info I can about it and planning how it will work. The bleed valve is what’s throwing me a curve ball because I can’t find what connects to it. I can post a pic of the starter and valve to see if y’all can help a little bit. -Cullen
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Post by racket on Jun 5, 2021 20:07:29 GMT -5
Hi Cullen
Yep , post some pics and we'll see if we can help .
Cheers John
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Post by turbojet atv on Jun 7, 2021 7:48:33 GMT -5
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Post by pitciblackscotland on Jun 7, 2021 8:24:21 GMT -5
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Post by racket on Jun 7, 2021 16:59:55 GMT -5
Hi Cullen
Take Marks advice and remove all that "complication" , keep it for a latter date when you have everything sorted and you want to add "sophistication??", but at this stage , keep it simple , theres no way of knowing if all that complication is in working order .
Cheers John
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Post by turbojet atv on Jun 8, 2021 2:32:55 GMT -5
Thanks John & Mark. I’ll take it off and put it in a box for a later date.
I’m going to get one of those manual cut off pieces to vent P2 air from the engine to keep it from surging the comp.
Going to start welding the end cap, forming the exhaust funnel & weld the bolt ring. It’s slowly but surely coming together. This is very fun, I’ll admit that!
-Cullen
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Post by pitciblackscotland on Jun 8, 2021 3:53:25 GMT -5
Thanks John & Mark. I’ll take it off and put it in a box for a later date. I’m going to get one of those manual cut off pieces to vent P2 air from the engine to keep it from surging the comp. Going to start welding the end cap, forming the exhaust funnel & weld the bolt ring. It’s slowly but surely coming together. This is very fun, I’ll admit that! -Cullen No worries, a couple of vids to give you a bit more info on the starter. Some of them may use a start cart or the APU to get the comp air from. Cheers, Mark. www.youtube.com/watch?v=xQVLoI5_t-swww.youtube.com/watch?v=WcwnZYXMaho
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Post by turbojet atv on Jun 10, 2021 8:15:03 GMT -5
Hi Mark,
That’s some awesome information in those YouTube videos. It opened up a little bit more about these starters. I just didn’t catch if they have a rpm limit or if the clutch inside the gear box disengages after a certain rpm. I heard what I think was they can go up to 7k on big engines? I’m not sure, I’m going to research that question.
Also, I’m starting work on my flame tube. The math to make the holes are maybe different than the ones y’all use with diesel turbos? I understand I’m breaking new grounds with a performance turbo so I’m assuming the math for the ft holes will be slightly different.
Did y’all also; while I’m thinking about this question, weld the FT to the end cap with the injectors only or did y’all make it where it can be bolted on and off. I don’t plan to run a evap system at this time to make it a little simple as I work all the kinks out of it in the beginning and then add in more complex parts to improve on the design.
-Cullen
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ausjet
Veteran Member
Joined: May 2013
Posts: 133
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Post by ausjet on Jun 10, 2021 10:02:36 GMT -5
From what I gather those air turbine starters run off about 40psi and a bucket load of flow from the start kart to get the main engine up to speed. If you’re going to use a domed end cap on your flame tube then it’s best to make it bolt onto the combustion chamber and have the injector screw/bolt into an adaptor. The other end needs to have a slip joint into the turbine flange to allow for thermal expansion. For an idea this is the top of a flame tube off a GTCP85 apu which is used in 737’s and a heap of other aircraft. You can see the 3x threads in the flame tube. The bolts go through the combustion chamber, injector and screw into the flame tube holding it all together.
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Post by turbojet atv on Jun 10, 2021 12:49:25 GMT -5
For the amount of space I have on my build, I’m going with a flat end cap. Not a domed one. My space is very limited to what I’m able to use and work with.
That info on the starters helps, thank you.
-Cullen
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on Jun 10, 2021 13:34:00 GMT -5
Hi Cullen, I have a bolt on cap like you, with a central boss that the injector screws into. The top of my flame tube is welded to this, that section has the primary and secondary holes in. That makes the red assembly in the picture below. As mentioned you will need a slip joint for the thermal expansion, my slip joint is between the secondary and tertiary holes (My tertiary holes are part of the transition to the turbine, in green). imgbb.com/jwbBRQXimgbb.com/RhtF56Zimgbb.com/4sL95pPThere are many ways of doing it, but that's just the one I chose! Cheers Scott
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Post by turbojet atv on Jun 10, 2021 14:06:44 GMT -5
That’s awesome, thanks Scott!
I’ve got a area near my 90 degree elbow is going to my turbo that will allow the ft to expand and contract as it wishes to. I read that on here somewhere talking about that.
That’s sweet, I’ll weld my ft to my injector cap once I get all the holes drilled. Should save myself a headache later on.
-Cullen
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