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RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: croatiablu ORIGINAL: jetrichie I seen some details on the GTBA site once on making a spot welder that might help, also 304 spec stainless is ok 316 would be better. Got the guys in my workshop to make one once for a 14lb turbine, made the inner diameter the same as the NGV with the front flared out, length was just made to suit model. You make the zig zag spacer between the walls with a strip about 10mm wide and fed through a gear mesh, or just fold with pliers.. Spot welder is important and makes the job fairly easy, check out GTBA or google on making one. no doubt someone will correct me and give a more accurate method of calc dia etc. Gap from tailcone to tube is important, 15-20mm seem to be the norm http://www.philpem.me.uk/elec/welder/ I built this welder some time ago to spot weld nickel tabs onto batteries for flight packs and found that this unit has plenty of power to spot weld sheet stainless for exhaust pipes. A different slant on the homemade spot-welders, which are usually made from microwave oven transformers... BJ:) |
RE: How To Build RC Jet Turbine Exhaust Tubes
BJ
I'm in Australia too. Did you find a place to get hold of 316 at a reasonable price? I want to build a bifurcated pipe for a Yellow F4. Tam makes them but it'll cost about $650 by the time it crosses the Pacific, so I thought I'd roll my own. Maybe we could share costs for a sheet of SS if you havent already built your pipe. Gowrie |
RE: How To Build RC Jet Turbine Exhaust Tubes
1 Attachment(s)
ORIGINAL: BJ64 ORIGINAL: croatiablu ORIGINAL: jetrichie I seen some details on the GTBA site once on making a spot welder that might help, also 304 spec stainless is ok 316 would be better. Got the guys in my workshop to make one once for a 14lb turbine, made the inner diameter the same as the NGV with the front flared out, length was just made to suit model. You make the zig zag spacer between the walls with a strip about 10mm wide and fed through a gear mesh, or just fold with pliers.. Spot welder is important and makes the job fairly easy, check out GTBA or google on making one. no doubt someone will correct me and give a more accurate method of calc dia etc. Gap from tailcone to tube is important, 15-20mm seem to be the norm http://www.philpem.me.uk/elec/welder/ I built this welder some time ago to spot weld nickel tabs onto batteries for flight packs and found that this unit has plenty of power to spot weld sheet stainless for exhaust pipes. A different slant on the homemade spot-welders, which are usually made from microwave oven transformers... BJ:) The logical thing to me at first was to place one contact outside and the other on the inside directly below and burnt a hole and laterdiscovered that you could place both contacts on the outside of the tube and press down therefore spotwelding in two places without needing to go inside the pipe.I will post some photos later for anyone interested as soon as I can find the darn usb cable to offload some shots. I read some earlier posts and after seeing that Tam uses .007 somewhere, ordered up .007 stainless shim stock from McMaster. The cost of the sheet for 12" X 52 or so was a whopping 30 bucks. I am not sure what the cost to Australia would be. Iam not sure if you need 316 stainless though as my understanding from the metal guys is that the only reason to use 316 is if you are using the stuff for a medical application. In any event the .007 is thin enough that Iwas able to cut the sheet with a good set of kitchen scissors (Wife would kill me if she knewhttp://www.rcuniverse.com/forum/js/f...ular_smile.gif) I then was able to hold the form of the roll with a piece of masking tape then started to spot weld away. Icreated the spacers from 3/8" strips bent back and forth like a zig zag then spot welded those to the tube. For the outside pipe, I used aluminum flashing then settled on aluminum foil tape to hold the outside pipe. Works great with no discoloring. Heat from outside pipe is warm to touch and overall wieght of pipe is about 8 oz complete. Andy</span></div> |
RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: GRVW BJ I'm in Australia too. Did you find a place to get hold of 316 at a reasonable price? I want to build a bifurcated pipe for a Yellow F4. Tam makes them but it'll cost about $650 by the time it crosses the Pacific, so I thought I'd roll my own. Maybe we could share costs for a sheet of SS if you havent already built your pipe. Gowrie I haven't built any pipes yet - the Boat is on hold, and I'm back on my F-111 project at the moment (albeit a 1:16 ducted fan for now). I searched for quite a while, and managed to track down 2 places that either have or can get 316 SS in the 8-10 thou range. To cut a long story short, I think one sells the standard 300mm width, the other in 600mm (??). I'd have to check my records to let you know the exact sizes and prices I got. From memory, there's a minimum buy quantity, and I think the wider stuff was ex-WA (so there's shipping involved). Let me know if you're still interested and I'll dig up the info I've stuck in a diary somehwere. I'm pretty sure that the narrower sheet/coil was local and they only do 9-5 Mon-Fri. But I recall that they'd leave it by the door for me to pick up on a weekend. Come the New Year, I probably won't have a job, so pick-up would be easier to arrange. BJ:) |
RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: croatiablu ORIGINAL: BJ64 ORIGINAL: croatiablu ORIGINAL: jetrichie I seen some details on the GTBA site once on making a spot welder that might help, also 304 spec stainless is ok 316 would be better. Got the guys in my workshop to make one once for a 14lb turbine, made the inner diameter the same as the NGV with the front flared out, length was just made to suit model. You make the zig zag spacer between the walls with a strip about 10mm wide and fed through a gear mesh, or just fold with pliers.. Spot welder is important and makes the job fairly easy, check out GTBA or google on making one. no doubt someone will correct me and give a more accurate method of calc dia etc. Gap from tailcone to tube is important, 15-20mm seem to be the norm http://www.philpem.me.uk/elec/welder/ I built this welder some time ago to spot weld nickel tabs onto batteries for flight packs and found that this unit has plenty of power to spot weld sheet stainless for exhaust pipes. A different slant on the homemade spot-welders, which are usually made from microwave oven transformers... BJ:) The logical thing to me at first was to place one contact outside and the other on the inside directly below and burnt a hole and later discovered that you could place both contacts on the outside of the tube and press down therefore spotwelding in two places without needing to go inside the pipe. I will post some photos later for anyone interested as soon as I can find the darn usb cable to offload some shots. I read some earlier posts and after seeing that Tam uses .007 somewhere, ordered up .007 stainless shim stock from McMaster. The cost of the sheet for 12'' X 52 or so was a whopping 30 bucks. I am not sure what the cost to Australia would be. I am not sure if you need 316 stainless though as my understanding from the metal guys is that the only reason to use 316 is if you are using the stuff for a medical application. In any event the .007 is thin enough that I was able to cut the sheet with a good set of kitchen scissors (Wife would kill me if she knew[img][/img]) I then was able to hold the form of the roll with a piece of masking tape then started to spot weld away. I created the spacers from 3/8'' strips bent back and forth like a zig zag then spot welded those to the tube. For the outside pipe, I used aluminum flashing then settled on aluminum foil tape to hold the outside pipe. Works great with no discoloring. Heat from outside pipe is warm to touch and overall wieght of pipe is about 8 oz complete. Andy</span></div> Great post again. As far as a Trafo goes, I have a small CigWeld arc welder I could use to source the power. And I also bought one of those one-sided spot-welding guns - never had the chance to try it yet due to 'learning to fly' and other projects getting in the way LoL. Reading what you have described sounds like it should be a fairly easy job to construct your capacitive-discharge style spot-welder for not too many $$$ - and your results sound fantastic. Particularly the 'weld from one side only' bit - making those long elbowed copper contacts for the traditional spot-welder 'pincers' sounds like a right Royal pain in the a'ss. So if your jobbie can do a decent weld from just the outside of the tube it would be a real bonus. As I've just replied to Gowrie above, my Turbine stuff has gone quite of late as I concentrate on a few other things atm. But you've p'ricked my ears up again re making tubes again. For the record, you guys in the States really do get some great deals - 30 bucks of 316 SS down here would be about enough to cover a cigarette packet (no, I'm not kidding you either). Darn stuff is as expensive-as. And while 316 might be considered overkill by some, I've read around the traps that while 304 (??) might do the job, 316 will last forever. As you can probably tell, I'm a bit rusty (pun intended :) ) regarding the research I did on raw materials down here in Oz about 6 months ago - but it really is dear as poison when compared to what you can probably get the same thing for where you live. *If* you can get it. Same goes for the electronics too. Having said all that, it's great to see some fresh discussion and idea-swapping going on in this Thread once again. Look forward to seeing/hearing what everyone has to say... BJ:) |
RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: BJ64 ORIGINAL: croatiablu ORIGINAL: BJ64 ORIGINAL: croatiablu ORIGINAL: jetrichie I seen some details on the GTBA site once on making a spot welder that might help, also 304 spec stainless is ok 316 would be better. Got the guys in my workshop to make one once for a 14lb turbine, made the inner diameter the same as the NGV with the front flared out, length was just made to suit model. You make the zig zag spacer between the walls with a strip about 10mm wide and fed through a gear mesh, or just fold with pliers.. Spot welder is important and makes the job fairly easy, check out GTBA or google on making one. no doubt someone will correct me and give a more accurate method of calc dia etc. Gap from tailcone to tube is important, 15-20mm seem to be the norm http://www.philpem.me.uk/elec/welder/ I built this welder some time ago to spot weld nickel tabs onto batteries for flight packs and found that this unit has plenty of power to spot weld sheet stainless for exhaust pipes. A different slant on the homemade spot-welders, which are usually made from microwave oven transformers... BJ:) The logical thing to me at first was to place one contact outside and the other on the inside directly below and burnt a hole and laterdiscovered that you could place both contacts on the outside of the tube and press down therefore spotwelding in two places without needing to go inside the pipe.I will post some photos later for anyone interested as soon as I can find the darn usb cable to offload some shots. I read some earlier posts and after seeing that Tam uses .007 somewhere, ordered up .007 stainless shim stock from McMaster. The cost of the sheet for 12'' X 52 or so was a whopping 30 bucks. I am not sure what the cost to Australia would be. Iam not sure if you need 316 stainless though as my understanding from the metal guys is that the only reason to use 316 is if you are using the stuff for a medical application. In any event the .007 is thin enough that Iwas able to cut the sheet with a good set of kitchen scissors (Wife would kill me if she knew[img][/img]) I then was able to hold the form of the roll with a piece of masking tape then started to spot weld away. Icreated the spacers from 3/8'' strips bent back and forth like a zig zag then spot welded those to the tube. For the outside pipe, I used aluminum flashing then settled on aluminum foil tape to hold the outside pipe. Works great with no discoloring. Heat from outside pipe is warm to touch and overall wieght of pipe is about 8 oz complete. Andy</span></div> Great post again. As far as a Trafo goes, I have a small CigWeld arc welder I could use to source the power. And I also bought one of those one-sided spot-welding guns - never had the chance to try it yet due to 'learning to fly' and other projects getting in the way LoL. Reading what you have described sounds like it should be a fairly easy job to construct your capacitive-discharge style spot-welder for not too many $$$ - and your results sound fantastic. Particularly the 'weld from one side only' bit - making those long elbowed copper contacts for the traditional spot-welder 'pincers' sounds like a right Royal pain in the a'ss. So if your jobbie can do a decent weld from just the outside of the tube it would be a real bonus. As I've just replied to Gowrie above, my Turbine stuff has gone quite of late as I concentrate on a few other things atm. But you've p'ricked my ears up again re making tubes again. For the record, you guys in the States really do get some great deals - 30 bucks of 316 SS down here would be about enough to cover a cigarette packet (no, I'm not kidding you either). Darn stuff is as expensive-as. And while 316 might be considered overkill by some, I've read around the traps that while 304 (??) might do the job, 316 will last forever. As you can probably tell, I'm a bit rusty (pun intended :) ) regarding the research I did on raw materials down here in Oz about 6 months ago - but it really is dear as poison when compared to what you can probably get the same thing for where you live. *If* you can get it. Same goes for the electronics too. Having said all that, it's great to see some fresh discussion and idea-swapping going on in this Thread once again. Look forward to seeing/hearing what everyone has to say... BJ:) <div style="margin: 0in 0in 0pt"><span style="font-size: 9pt">Thanks.... Let me clarify a couple of things first... I have never rolled my own tube although I have made a lot of other things.I saw the cost of the pipes here from Tamjets and said hmm someone has probably done this before and I certainly can think of a lot of things to do with $300 or so besides buy a pipe, right? Ifound another thread somewhere and figured what the heck do I have to lose?If the thing works, great. If not, buy one from Tamjets.Also Ifigured I would bench test the crap out of it and if it holds its own,I have made outwell. All of that said, I read a number of threads prior to tryign thiswhere people measured the wall thickness of Tamjet pipes. Some said they measured.008 but someone else appeared to have some discrete knowledge of Tam having used .006 then migrating to .007.Between the two posts Ielected to go for .007. Now I used 304 stainless but only after speaking to welders, the metal guys and the fabricators. They all said that the only difference performance wise with the 304 and 316 is that 316 is made specificallyfor medical, period. I guessif you want to maintain a pure sterile environment316 is the only way to go. Labs etc... same thing. Aside from this I was told there are no other differences but again Ihave no working knowledge of this and could have been misled. Here is the thing,a sheet of 304 stainless ranme $30US for 12 X 52 inches. or so.316 is $62 for the same size (McMasters). One sheet of the stuff is plenty for a pipe or more so what do Ihave to lose, ehh? If the pipe burns up prematurely I figured I will make one out of 316 but also not knowing if this would even work as ihave never done it,I figured minimize the loss if it does not work. As I said get out the wife’s scissors to cut the stuff.. it is that easy but watch for your hands as the stuff is really sharp.Aluminum same thing it with a scissors. I twisted this thing together in less than an hour over a cup of coffee literally over the dining room table (guys favorite work place and woman's worst one:) ) I posted a pic of the method of welding I used above.I do not know if this is prescribed welding method 101 or not as Ihappened across this altogether by accident but I will tell you it works. I made a weld point about every 1/2 inch. It is actually a lot of fun to make and my kid kept asking me when can I hit the pedal dad (welding pedal). Andy</span></div> |
RE: How To Build RC Jet Turbine Exhaust Tubes
<div style="margin: 0in 0in 0pt"><span style="font-size: 9pt">I tried using the welder with the points inside and outside the tube as anyone would probably figure on doing. Burnt a hole right on through. Ihad to figure out what to do about the hole later on and put a rivet through it with the blind side faced in. The pic of me with the contacts on the outside worked great.keep in mind, I did not try this once and say whohooo, I popped the thing a hundred times from top to bottom and it worked all the way down the side. If you venture to try this, take some scrap and make a weld. It is not coming apart. The thing is to make sure you are exerting enough pressure to contact the inside of the roll with the topside so as to make contact.Again, I do not know if this is prescribed method 101 but it worked for me and Ihave a pipe in my plane that works fine... Just have to see how well the 304 holds up...
Andy</span></div> |
RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: BJ64 ORIGINAL: croatiablu ORIGINAL: jetrichie I seen some details on the GTBA site once on making a spot welder that might help, also 304 spec stainless is ok 316 would be better. Got the guys in my workshop to make one once for a 14lb turbine, made the inner diameter the same as the NGV with the front flared out, length was just made to suit model. You make the zig zag spacer between the walls with a strip about 10mm wide and fed through a gear mesh, or just fold with pliers.. Spot welder is important and makes the job fairly easy, check out GTBA or google on making one. no doubt someone will correct me and give a more accurate method of calc dia etc. Gap from tailcone to tube is important, 15-20mm seem to be the norm http://www.philpem.me.uk/elec/welder/ I built this welder some time ago to spot weld nickel tabs onto batteries for flight packs and found that this unit has plenty of power to spot weld sheet stainless for exhaust pipes. A different slant on the homemade spot-welders, which are usually made from microwave oven transformers... BJ:) Anyway, there are twoICregulatorsused.One is a L200 ICregulator to charge the cap and the other is an LM7805 which is a 5 volt regulator used to fire the SCR.There area fewsmall signal NPN and PNPtransistors to locate anda relay (5volt low current) a pushbutton, a few resistors and a potentiometer (low current) to regulate the charge. Essentially the top portion of the circuit charges the cap and the bottom portion of the circuit provides a single pulse (no bounce) to trigger the SCR. I used 2 good sized SCRs and ran them in parallel. When the cap discharges through near zero resistance (welding leads, steel plate) current is in the hundreds of amps for a few milliseconds or so while the cap(s) discharge. If you have a bunch of smaller caps, fine, run them all in parallel. The use of heavy wire in my book is paramount. I used something like 00 gauge welding wire. In layman's terms the stuff is about 1/4 diameter with the insulation stripped. I hope this helps.Email me with any questions if help needed. Andy</span></div> |
RE: How To Build RC Jet Turbine Exhaust Tubes
Hi Marc s. Can you please share some detailed plans to make the exhaust pipe. I am planning to make it for the aviation design rafale. I will be using a wren supersport. Please help.
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RE: How To Build RC Jet Turbine Exhaust Tubes
This is an interesting thread. I'm curious if there is any pros/cons to the various bellmouth shapes we see out there. Some appear to be a radiused ring on the end of the pipe (nice for tight spaces) and others appear to be a bowl shape to catch the air, much like the shape of the rear of a full bypass.
Any thoughts on the subject and shape of these? Or does it really matter as long as adequate air is pulled in from the outside and still catch the hot exhaust out of the turbine? |
RE: How To Build RC Jet Turbine Exhaust Tubes
Sean, I don't think the shape is that critical.
I asked the Jetcat distributor in Oz (who has a load of turbine experience) & he said the bellmouth does two jobs. One was to direct the air into the pipe, the other is to support the front edge of the pipe which tries to collapse inward due to the suction which is drawing the cooling air in. The reason I asked him the question is I'm running a BVM dual walled pipe in a Sabre without the full bypass around the engine. The front of the pipe has no bellmouth at all. I was going to buy or make a bellmouth but in the end tried just flaring the end of the pipe out about 3mm wtih pliers. No problems at all although the BVM pipe is made from quite thick stainless so it's probably stronger (and heavier [:o]) than the other pipes I've seen. - John. |
RE: How To Build RC Jet Turbine Exhaust Tubes
Hi Guys,
Great to see some discussion in this thread again. It's been a while - 14 months actually - since anything has been posted. I'm embarassed to say that I haven't done a single thing with my Turbines in that time. Haven't even started them. Been way busy with work and flying electrics. This fresh talk has got me itching to get back into the smell of burning kerosene :D BJ:) |
RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: Boomerang1 Sean, I don't think the shape is that critical. I asked the Jetcat distributor in Oz (who has a load of turbine experience) & he said the bellmouth does two jobs. One was to direct the air into the pipe, the other is to support the front edge of the pipe which tries to collapse inward due to the suction which is drawing the cooling air in. The reason I asked him the question is I'm running a BVM dual walled pipe in a Sabre without the full bypass around the engine. The front of the pipe has no bellmouth at all. I was going to buy or make a bellmouth but in the end tried just flaring the end of the pipe out about 3mm wtih pliers. No problems at all although the BVM pipe is made from quite thick stainless so it's probably stronger (and heavier [:o]) than the other pipes I've seen. - John. |
RE: How To Build RC Jet Turbine Exhaust Tubes
I've often wondered about that myself - you tend to see all sorts of 'bellmouth' shapes as well as some variance in the distance between the tube and the Turbine.
By the sounds of it, the actual bellmouth shape isn't all that important - so long as it directs the exhaust gases into the tube and the fire and brimstone doesn't start wandering around inside the airframe :eek: BJ:) |
RE: How To Build RC Jet Turbine Exhaust Tubes
ORIGINAL: DelGatoGrande on 2010 jetcat katalog on page 40 there are some info about engine size=dimentions http://www.jetcat.de/downloads/jetca...g-2010_web.pdf Do you have a copy of the catalog page that you can post? the link is no longer valid. Thanks, Mike |
RE: How To Build RC Jet Turbine Exhaust Tubes
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RE: How To Build RC Jet Turbine Exhaust Tubes
Hi George,
Is there an English version of this catalogue? Thanks Reuben |
RE: How To Build RC Jet Turbine Exhaust Tubes
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RE: How To Build RC Jet Turbine Exhaust Tubes
Hello ,
Could someone tell me where to get the john wright publication on RCJ ( pipe design ) or a copy .? Regards Ger56 |
If your still looking for stainless shim in Aus go to http://www.precisionshims.com.au/?stg=66 .005" x 300mm wide 304 stainless is $38 per meter best price I could find by far
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That's a great price, Terry.
They have a good assortment of stock. And Croydon is only a 20 min drive from here too. Thanks for posting ;) BJ:) |
Your welcome BJ I have been searching for a few days and no one in the US would post to Aus , I submitted a quote and half and hour later they rang .
Sure it may be 304 but can always make a spare at that price |
Originally Posted by Terryoc
(Post 11670839)
Your welcome BJ I have been searching for a few days and no one in the US would post to Aus , I submitted a quote and half and hour later they rang .
Sure it may be 304 but can always make a spare at that price |
Hey guys
looking to make a thrust tube myself, but none of the links to the jetcat catalogue's seem to work anymore... Need to to make one for a wren 54 thanks dave |
I'm sure that someone in here will chip in with some info, Ticket.
Been AWOL for quite a while now, so thanks Terry and Scoer for your info/offer. I'll have to get off my bum now and do some more Turbine stuff - it's just that there's so many RC things going on lately... :D BJ:) |
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