Author Topic: DIY: Make your own tunnel brace (Read 67199 times)

baconbits · « **Reply #100 on:** March 02, 2009, 06:11:55 PM »

From what I remember of my Millwright trade apprenticeship the rule of thumb is 3 threads min from the top of the nut to end of bolt..
Bacon

DeepBlueGXP · « **Reply #101 on:** March 02, 2009, 06:13:35 PM »

Aviation specs are two threads extended beyond the end of the nut. The problem is they are sealed and you can't see the other side.

SolNut · « **Reply #102 on:** March 02, 2009, 06:21:32 PM »

Quote from: DeepBlueGXP on March 02, 2009, 06:13:35 PM

Aviation specs are two threads extended beyond the end of the nut. The problem is they are sealed and you can't see the other side.

This can be measured!!

Not that I want to make folks intense!!!!, but what about HOLE size and shank length on the fastener? This subject could be a bit deeper than even this?

I am not in this hunt YET, but if I get my Coupe and it needs a Brace, I want to do it the correct way.

Take care-

Steve

DeepBlueGXP · « **Reply #103 on:** March 02, 2009, 09:14:15 PM »

Sorry Steve, but I'm not taking mine apart to measure the thread depth

SolNut · « **Reply #104 on:** March 02, 2009, 09:46:10 PM »

Quote from: DeepBlueGXP on March 02, 2009, 09:14:15 PM

Sorry Steve, but I'm not taking mine apart to measure the thread depth

Never asked you or anyone else to do that.

Assume, not.

BTW, I can measure thread thickness on my 2006 NA. Would anyone be interested? I doubt it. But then, the big question is there a difference between the first units (2006 MY) and the latest ones?

This thread/subject has been overworked. I will do mine when necessary and you will not do yours.

Modern Shop Practice is an old tome, though it has everyday help for DA like me.

Take Care

Steve

Sol Asylum · « **Reply #105 on:** March 02, 2009, 11:04:12 PM »

Quote from: 2091351 on March 02, 2009, 03:01:04 PM

I am not a ME, before going Digital in ’67, I was civil. My dad was an A&E Licensee after #2 who retired from an Aircraft Manufacturer. My early learning curve was punctuated with the fact that his Reed & Prince had a tan handle and the Phillips did not.

My question about bolt length for the Backbone was because my dad always said ‘that all fasteners have specifications’ (inees and outees). His legacy about this has provided me with drawers of fasteners that he sorted from the 5 gal buckets of sweepings that the surplus store sold. The cardinal rule of the assembly line being ‘if you drop something, do not pick it up, it could be the wrong fastener’.

Steve

Steve

I too am an A&"P" there are a lot of different aircraft bolts and each seems to have its own set of rules for how they are used. The most common aircraft bolts are "AN" and the general rule on bolt length is that the shoulder or unthreaded part should be at least as long as the depth of the hole you will be placing the bolt into. if the bolt is longer then you use a washer to shim the distance of the bolt so that the nut won't bottom out.

However what I suspect that GM did with the bolts for the brace is that they technically are not bolts but cap screws. Meaning that there is no shoulder to the bolt but that it is threaded to the head. Anyone care to correct me on this one?

You are also right to wonder how much thread engagement is taking place when you substitute a thicker plate of aluminum in for the original brace. Unfortunately I can't answer that but if you were to replace the bolts with ones that were longer by the amount of thickness of your new brace you couldn't go wrong.

As far as hole diameter if you stay with the same size hole that is in the original brace you should have no issue. The proper torque was also listed on this thread so as long as your new bolts are the same grade and thread as the originals you should use the same torque.

I am guessing that the GM bolts are metric in which case you will have a problem trying to figure out which of those surplus AN bolt to use as they are all standard. Its really kind of odd when you work on an American car and have to use a metric wrench but a German, Swiss, or for that mater most all other country aircraft you use standard wrenches (except for those F'n French made planes, there metric, and those British warbirds, they used BS or British Standard). P-51 Mustangs are another story as they used an American made version of a Rolls Royce engine, standard and BS.

BLK GXP · « **Reply #106 on:** March 02, 2009, 11:23:51 PM »

When I took mine off all of the bolts were the same length, at approximately 1.25 inches. When I took a friends off of his Sky they were all the same except for one which was approximately .5 inch. I presume this was just a case of someone at the factory simply grabbing a wrong bolt out of large bin that was not supposed to be there. The shorter bolt held the stock brace just fine, but would not work with the thicker brace. I think the length of the others is quite sufficient but I need to find one to replace the short one.

The sheet I used for mine is supposedly 7475-0 aluminum which is supposedly very corrosion resistant. I expect it will hold up very well, as I never plan on driving it on any salty roads, and all of the other surfaces it touches are painted

Critterman · « **Reply #107 on:** March 03, 2009, 10:35:37 AM »

These bolts appear to be longer than needed to do the job, maybe it is an issue of using available parts from the GM parts bin. the 1/2 or .5 inch bolt being the exception. All my bolts were over an inch long

Sky 5 · « **Reply #108 on:** March 29, 2009, 10:37:00 PM »

Pulled the OEM tunnel brace and found it not exactly just a .06" thin piece of tin. First observation, it has about a 1/2" curled rim which goes all the way around the perimeter. Second, it has 6 of these 1/2" ridges which extend from side to side every 10" or so for reinforcement. Third, on the wide aft end there is a 1" X 1/4" steel bar welded to the brace which ties in the two rear mounting bolts. Went online and found another brace from an '06 Solstice which is, of course, identical to the Sky tunnel cover panel (GM#15237456). Placed 8, 1/2" spacers on the middle holes and thinner spacers on both pairs of end mounting holes. Used a tiny bit of adhesive to keep the spacers temporarily in place and rubber banded the two tunnel braces together. Got back under the car, used a prybar to pull the exhaust back out of the way, and bolted the new twins into place. The oversized OEM bolts were plenty long enough and was not at all concerned about that; as had noticed when pulling them initially that they all had threadlock reside on less than half the length of the bolts. The other halves appeared dusty and seemed to have been sitting in an open space on the other side of the mounting bracket.

Took it out for a spin

and

happy Kappa!

Sly Bob · « **Reply #109 on:** March 29, 2009, 11:06:45 PM »

Cool idea and I'm glad it worked out for you as you described. If anyone wants my old tunnel brace you can have it for the cost of shipping.

So you made a sandwich from the two tin tunnel braces with spacers (washers?) in between. I suppose the old

is rather pointless at this point eh?

Sky 5 · « **Reply #110 on:** March 29, 2009, 11:16:44 PM »

Quote from: Sly Bob on March 29, 2009, 11:06:45 PM

So you made a sandwich from the two tin tunnel braces with spacers (washers?) in between.

Yes on the stainless washers for the four end holes and something like 7/16" nuts for the eight center mounting holes. Ix-nay on the photos at this time, as am not sure how to post pics yet. Plan to remove the "sandwich" in a few weeks while installing an PRi exhaust and see how everything is holding up...

DeepBlueGXP · « **Reply #111 on:** March 30, 2009, 06:11:03 AM »

Hope it doesn't become an issue with your sevice department. You'll have to make sure they re-install both pieces after they service your car.

Sly Bob · « **Reply #112 on:** March 30, 2009, 08:33:00 AM »

They shouldn't have any spare parts?

DeepBlueGXP · « **Reply #113 on:** March 30, 2009, 09:51:22 AM »

He may come back with only one installed.

Sky 5 · « **Reply #114 on:** March 30, 2009, 10:10:31 AM »

The Saturn dealer here is notoriously incompetent. Knock on wood... this Kappa will never see the inside of their service department. Y'all are right, if they saw this mod they would take 3 weeks going through their repair manuals trying to figure out what to do. Wouldn't trust them, even if they offered free oil changes. Only about 14 months left on the 3-year warranty so don't expect the sandwich brace to become a dealership issue.

Deep-GXP · « **Reply #115 on:** March 30, 2009, 02:32:39 PM »

What happened to the good old days of making a new piece and replacing the old with the new. Simple out, simple in.

Jasontamu · « **Reply #116 on:** May 12, 2009, 02:14:55 PM »

Would someone be so kind as to make me a tracing or mylar copy of the size needed please......??

I have access to aerospace aluminum and plasma cutters to make one....but would like the template if anyone is still offering their old or can make a copy on paper and mail it to me?

-J

Deep-GXP · « **Reply #117 on:** May 12, 2009, 02:58:37 PM »

Just take out the stock one and place it over the aluminum piece and trace it out.

Jasontamu · « **Reply #118 on:** May 12, 2009, 03:25:37 PM »

^ ya, that would mean some down time........wondering if anyone had a copy already traced out?

-J

Critterman · « **Reply #119 on:** May 12, 2009, 03:27:27 PM »

You can have it out, trace it and back in place in an hour.

Deep-GXP · « **Reply #120 on:** May 12, 2009, 04:27:22 PM »

Down time??? You can trace the whole thing in less than a minute and you have to take the stock one out anyway.

DeepBlueGXP · « **Reply #121 on:** May 12, 2009, 05:06:58 PM »

On page 1, http://kappaperformance.com/forum/index.php?topic=189.msg1258#msg1258, it says what size to get so you can cut out the shape when you remove it.

lil goat · « **Reply #122 on:** May 13, 2009, 08:57:27 AM »

I have to ask a question? While I am sure the DIY brace is better than the stock one, it would seem to me 1/8" is still to thin, the DDM Brace is 1/4" twice as thick or 3/8" 3 times as thick. I know they did a lot of testing to come up with these numbers, Dave told me about it. I have the 3/8" and I can put a jack under the right jacking point and bring both front tires off the ground easily it has stiffened my car so much. Can you even make one as cheap as DDM sells them anymore?

salstice · « **Reply #123 on:** May 13, 2009, 01:08:12 PM »

I can make one cheaper! Ask Hal9000!

DeepBlueGXP · « **Reply #124 on:** May 13, 2009, 02:00:00 PM »

I think mine was acutally 1/4, I updated the first post. Originally it said 3/16.

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Author Topic: DIY: Make your own tunnel brace (Read 67199 times)

lil goat