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  #11  
Old 12-04-2018, 02:33 AM
Tommy123 Tommy123 is offline
 
Join Date: Jul 2018
Location: Naples fl
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Wait until you see what they cost. Titanium is total overkill, the only time I used them was on the XB47 prototype project when contracting at Northrop. When I was forced to replace the huck bolts some idiot removed from a Mooney spar I used hi loks with Mooney engineering approval. eBay is your best bet and I prefer to use jap nuts on them. All Douglas aircraft used jap nuts instead of the hi lok collars, they are acceptable and won't snap off early like a hl70 can.
Like I said new they're about $5 each.
I see no need for them on a RV.
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  #12  
Old 12-04-2018, 02:39 AM
Tommy123 Tommy123 is offline
 
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And you better be dead on with your reamer when I was a inspector at voight if you could get a .001 feeler gaug to touch the hand under the head it was rejected. At Northrop inspector would have to buy off every hole for size before when even installed one. They are not for the inexperienced. That job required 25 years metal experience to even be considered.on flush hi locs the limitations were never above flush and .002 below flush.
Every hole was drilled using a drill bushing. XB-47 was all titanium with a carbon skin.
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  #13  
Old 12-04-2018, 05:06 AM
fixnflyguy fixnflyguy is offline
 
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Location: Winston-Salem, N.C.
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Default My reason for using Titanium

As I mentioned in my earlier post, the Titanium only saved me a couple pounds AT BEST, but as used in virtually every commercial airliner construction for the last 20 years, the aluminum coated titanium Hiloks and bolts have superior corrosion resistance..my main reason for going with titanium. Because they are relatively hard to find a vendor or even understand the trade name designations, its much easier to build with and resource "AN" hardware. Some of us have spent years of our life working with these, and they are "normal" in our world.There are cross reference documents available, and engineering data that can enlighten one about the shear/tension KSI ratings,compatibility and all the stuff to make substituting for AN and MS equivalents structurally correct. For me, I have spent many years making my living as a structures specialist and engineer on heavy jets battling stress and corrosion, so it is second nature.
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  #14  
Old 12-04-2018, 05:19 AM
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gmcjetpilot gmcjetpilot is offline
 
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Hi-Loks are very expensive fasteners and have specific collars. They come in titanium, steel and high strength and high temperature nickle alloys. They are again not cheap. If you have the part number you can google it and distributors will come up.

For 6Al-4V Titanium (Alloy Steel) standard Dia. part numbers are
HL 10 (HL18) Protruding Shear
HL 11 (HL19) 100º Reduced Flush Shear
HL 12 (HL20) Protruding Tension
HL 13 (HL21) Flush MS24694 Tension

The part number is for example protruding tension head titanium HL13()()-() 1st () are letters after fastener code is coating, second () diameter in 32nd and thrid () in 16th.
HL13VU6-12 bare no lube, 3/16" dia and 3/4" grip. The charts and specs are on line.

You can have tension on hi-loks if they have tension heads and tension collars...

Why? Steel AN hardware is fine, and the weight savings will be small in a small airplane. A jet that has 100,000's of fasteners, Ti Hi-Loks saves weight. Did I say this stuff is expensive for low volume purchases... 25 years ago Boeing had a surplus store in Kent Washington. They use to have barrels of Hi-loks for penny's on the pound. It is what they swept off the factory floor or mixed up surplus... They stopped selling the fasteners, because people were buying it and selling on the open market as approved hardware. You can't do that. All parts for commercial transports need records, including fasteners. Too bad. I have a box of some Ti bolts and hi-loks. Be aware there are China made bootleg Hi-Loks on the market, with bogus quality.
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Last edited by gmcjetpilot : 12-04-2018 at 05:38 AM.
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  #15  
Old 12-04-2018, 07:25 AM
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Toobuilder Toobuilder is offline
 
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Expensive in small quantities, yes. But I used to do financial proposals for my company and I know what they cost when you buy them by the truckload, and in most cases a Ti Hi-Lok is less expensive to the company than you or me buying the equivalent AN bolt from Spruce.

And BTW, those center section bolts are big and heavy as a set. A set of Ti Hi Loks there will save you well over a pound. Saving weight on an airplane is never a bad idea if the structure is not compromised.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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  #16  
Old 12-04-2018, 09:11 AM
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Toobuilder Toobuilder is offline
 
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This discussion has been joined by several people who have hands on knowledge of the Hi-Lok fastener system through their employment in ?big airplane? companies. I too have decades of ?big airplane? employment and like them, have buckets of surplus Ti fasteners. I also agree with them wholeheartedly that proper hole prep is paramount to a properly engineered shear connection. In an interference fit such as used in the center section bolts, an out of round or oversized hole will destroy the strength of that connection, no matter what material the fastener is made of.

In short, a perfectly round, reamed to correct interference fit hole is required whether you are using an exotic Ti Hi-Lok or an AN bolt from Spruce. The precision of the hole is the key to strength (assuming the pin meets minimum engineering specifications).

That said, I take exception to the cautions in this thread that seem to imply the Hi-Lok pin is somehow less tolerant of perfection than an AN bolt. It is true that Hi-Loks are a specialty fastener and the ?big airplane? companies like mine require training on their installation, but that is true of almost EVERY critical operation found on the shop floor. The Hi Lok system is in many cases a direct replacement for a traditional permanent bolted connection, and it?s not a difficult process to learn. Here?s what the company?s website has to say:

The HI-LOK? Fastening System:
? is basically a threaded fastener which combines the best features of a rivet and a bolt. It consists of two parts, a threaded pin and a collar
? is rapidly and quietly installed by one person from one side using standard power tools or hand tools with less worker fatigue than with either regular rivets or bolts.
? easily adapts itself to large scale production in a variety of pin and collar material combinations for high strength and high temperature performance.

A bolt and nut system is heavier than the HI-LOK? Fastening System. Minimum weight results from elimination of the wrenching surfaces on a bolt and nut system. Wrenching clearances are minimized and great weight savings result from the design of more compact structural joints.

Bolt and nut systems require calibrated torque wrenches and torque inspection. The HI-LOK? Fastening System eliminates these concerns.



So, the bottom line as I see it: When it comes to hole prep for a critical shear connection, ?Perfection? is the standard we should strive for; regardless of the fastener system we are using. If any of our more experienced shop personnel have a reason why a Hi-Lok pin is more intolerant of a properly prepared hole than an AN bolt, I?d sure like to hear it. I?m always ready to learn something new.

As for ?worth it? regarding the cost vs. weight savings, that?s for the individual to decide. As has been discussed, these can be acquired for a huge range of pricing from ?free? to ?eye watering?. And even if you have to pay full price, spending $500 bucks to save a pound on your center section bolts is far better money spent than an exotic, multicolor paint job (IMHO).
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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  #17  
Old 12-04-2018, 09:22 AM
bnt83 bnt83 is offline
 
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I wouldn't substitute a fastener to use something that is even further away from aluminum on the galvanic corrosion chart...
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  #18  
Old 12-04-2018, 09:36 AM
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Steve Melton Steve Melton is offline
 
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Quote:
Originally Posted by bnt83 View Post
I wouldn't substitute a fastener to use something that is even further away from aluminum on the galvanic corrosion chart...
the Galvanic table shows that steel and aluminum are reasonably compatible, but if titanium and aluminum contact, the aluminum will be the anode and corrode.
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Last edited by Steve Melton : 12-04-2018 at 10:01 AM.
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  #19  
Old 12-04-2018, 11:02 AM
fixnflyguy fixnflyguy is offline
 
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Default Al/Ti interface

To throw another technical aspect in the mix..The Titanium Hiloks most often used are aluminum coated from production which is identified in the part number code (K on Boeing hardware), and gives the fastener protection from the Ti being in direct contact to the Al structure. It is way better than what happens when alloy steel rusts in an aluminum structure.
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  #20  
Old 12-04-2018, 11:49 AM
Freemasm Freemasm is online now
 
Join Date: Nov 2017
Location: Orlando
Posts: 195
Default The Confession

I should have probably started with this instead of jumping right to the Hi-Lok topic. I'm making F1/F4 wings from a partially completed RV-4 set. Being "out of order" in assembly (bottom skins on), makes it more difficult. A couple of the holes where AD6s were removed are less than perfect. My brain jumped straight to Hi-Lok option. May be able to draw the rivets all but one of the locations. Others have stated Vans approved (without a paper trail) installation of AN4 bolts in these locations. Any related advice/stories/suggestions are appreciated. Thanks again
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