You might want to check out McMaster Carr... they have 18-8 bolts (actually cap screws) with drilled heads... go to their site mcmaster.com and put 90121A581 into the search box... it's probably not the right size bolt but it will take you to that catalog page. Unfortunately they don't appear to have them in metric sizes, but once you get past 1/4" you can frequently use SAE sizes in lieu of the metric(as long as you're providing both screw & nut.... thread pitches don't match.) BTW, take a look at 321 stainless for the stuff you're thinking about doing in Inconel... IHTH. <Marv>
shipchief@aol.com wrote:
>
> Lynn,
> I think you are right about bolt material, I looked up grade 8 steel, it's
>only rated to 450 degrees F. 18-8 (304) stainless, although much weaker, has
>incredible temperature range . It's rated for pressure vessel service to
>about 1300F and general use to 1690F.
> So I just broke off a 1/16" drill in the head of an 18-8 stainless bolt,
>trying to make it accept safety wire. I'll keep working on that.
> I'm considering Inconel 600 hardware for the turbo inlet flange, it's rated
>to 2000F, but I'll try the stainless there for now, and watch it a lot.
> I plan to trim large diameter washers to fit tight against the turbo and
>header bodies, then after tightening the bolts, bend the washer edge up to
>act as a lock tab.
>
>
>
> -----Original Message-----
>From: shipchief shipchief@aol.com
> To: Rotary motors in aircraft <flyrotary@lancaironline.net>
> Sent: Mon, Jan 27, 2014 7:22 pm
> Subject: [FlyRotary] Re: Exhaust Leak at Turbo Outlet Flange
>
>
> Dave;
> you pretty well summarized the problem.
> Ross the Subaru guy over on the VANs air force forum had valuable input as
>well.
> After I cleaned up and inspected the mess, installed grade 8 bolts and grade
>C high temp lock nuts on the turbo mount flange. I used the stainless
>embossed shim type gasket.
> I assembled the turbine exhaust - to - exhaust pipe flange W/O gasket, using
>1" grade 5 bolts that I had on hand. I used grade 8 washers, stacked based on
>the hole depth, they are not all the same depth.
> I removed the Kevlar exhaust pipe wrap, cut off an undamaged section, and
>stuffed it into the burned thru hole in the turbo blanket.
> I made exhaust pipe heat shields out of cut offs from galvanized building
>studs, left over from building my hangar.
> N89SE ran like a top, and made the 32 minute flight back to the Home Drome
>with no trouble.
> Today I shopped at the local specialty fastener store and picked up more
>Grade 8 hardware and some 1/16" cobalt drill bits, no one seems to carry
>drilled head grade 8 bolts around here.
> I brought the top cowl home to repair the heat damaged spot over the turbo.
>The repair might be an aluminum inspection door.
> Oh, one last thing; today I post flight inspected the repair, and all eight
>fasteners took 1/12th of a turn to re-tighten. I figure that's just thermal
>setting. Even if safety wired, they would need to be un-wired and re-torqued
>at least once?
> (I posted similar on the VANs forum, so you might see this over there too)
>
>
> -----Original Message-----
>From: Lehanover <Lehanover@aol.com>
> To: Rotary motors in aircraft <flyrotary@lancaironline.net>
> Sent: Mon, Jan 27, 2014 10:59 am
> Subject: [FlyRotary] Re: Exhaust Leak at Turbo Outlet Flange
>
>
>
> If you use locking nuts like Jet nuts that grip the stud, you just back out
>the stud on removal. Use the stock nuts or stainless nuts and safety wire
>them in the tightening direction. They never come loose and can be removed
>without drama. On my NA engines I use no exhaust gasket. Just a bead of GE
>100% silicone tub and tile calk. Keep it well away from the ports. Never had
>a leak, but I had no back pressure from a turbo hot section either. Might be
>worth a try.
>
> Lynn E. Hanover
>
>
>
>
> In a message dated 1/27/2014 9:09:09 A.M. Eastern Standard Time,
>cardmarc@charter.net writes:
>
>
> I believe Mazda uses some Inconel hardware on the 93+ 13Brew
>engines…………found this out the hard and expensive way.
>
> Marc
>
>
>
>From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
>Behalf Of David Leonard
> Sent: Saturday, January 25, 2014 8:14 PM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: Exhaust Leak at Turbo Outlet Flange
>
>
>
>
> Bummer! Glad you are safe.
>
>
>
>
>
> I use the stock steel nuts. Locknuts might be an improvement but not if
>there is any non-steel component. I did loose one of those nuts once
>without to-do. Not sure how long it was gone. The other 2 held everything
>together.
>
>
>
>
>
> Be very careful with what gaskets you choose. I found some nice-looking
>aftermarket turbo manifold gaskets for about $20 while the stock versions
>are about $90 each, so I installed one. It lasted about 30 hours until it
>disintegrated. The resulting exhaust leak burned through a coolant line
>and I dead sticked onto a local airport (departing from a formation routine
>at an airshow!.. complete with a cloud of steam).
>
>
>
>
>
> Sigh, the stock ones are nothing but stainless steel layer, not some sort
>of fiber stuff in the after market ones.
>
>
>
>
>
> On another occasion I was using some very nice and expensive exhaust
>clamps that were steel but I didnt notice that part of the block holding
>the nuts was aluminum. About 50 hrs in something caused the alumimum to
>get too hot, which created an exhaust leak, which accelerated the process.
> It burned a hole in the cowl and splatered molten aluminum everywhere -
>some of it is still around.
>
>
>
>
>
> Another time I was using some fancy exhaust wrap. It slowly disintigrated
>over the course of 100+ hours and was generally an annoyance.
>
>
>
>
>
> I tried a flowmaster hushpower muffler but melted most of the stuffing out
>of it on the first flight. Luckily it melted pretty cleanly and didnt clog
>the exhaust.
>
>
>
>
>
> Moral of the story.. as if it didn't take me long enough to beat this
>through my skull.. NOTHING that is not made of steel or better goes into
>any part of the exhaust system. Particularly gaskets and nuts.
>
>
>
>
>
> Guess I should have passed that one along sooner. Glad you got back
>safely. Good job.
>
>
>
>
>
> Dave Leonard
>
>
> On Sat, Jan 25, 2014 at 5:14 PM, <downing.j@sbcglobal.net> wrote:
>
>
>
>
>
>
>
> I had the nuts come loose on my turbo manifold on the block, I'm using
>with out the turbo, so I drilled the nuts and secured them with wire.
> JohnD
>
>
>
>
>
>
> Thanks for keeping us all informed , helps us all to make sure we look
>for often simple overlooked areas.
>
>
>
>
>
> Cheers
>
>
> Christian
>
>
> Renises 13 b rv7
>
> Sent from my iPad
>
>
>
> On 26/01/2014, at 3:17 AM, shipchief@aol.com wrote:
>
>
>
>
> During the 8th flight of my RV8 with 13B Turbo, I experienced an
>exhaust leak at the turbo exhaust flange. I mistakenly used brass
>exhaust nuts which are twice as tall as regular nuts. They work great
>on most engines. I should have know better, as the temperature at the
>turbo outlet, under the insulation is much higher.
>
>
> The brass nuts softened and deformed into a flange face at the washer!
>Once the tension was gone, the heat & vibration did the rest.
>
>
> The exhaust gasket blew where the gap was widest, at the top.
>
>
> The escaping heat burned thru the insulating jacket and the stick on
>reflective aluminum. Then the fiberglass cowl charred, I smelled
> that!
>
>
> I was close to my destination, and high, so I was able to pull off the
>power, put down the nosed and get on the ground without incident.
>
>
> I'm disassembling it now, looks like I need 4 high temperature lock
>nuts and a TO-4 exhaust flange gasket. I should review and improve the
>insulation over the turbine housing. Also I need to repair the charred
>area of the cowl, which might be in the form of an aluminum access
> hatch.
>
>
>
>
>
>
>
>
>