Button Head Bolt / ARP Bolt / Irs Sub Frame

[Bosko]

I went down to ARP today to see what they can do for our FAT TIRE clearance problem. I printed out Hunter's pictures of his button head bolt install and showed it to them. I also went to Ford and bought a factory bolt and gave it to them. The fastener guru I dealed with wanted to know about its application. I asked him if he could make a button head bolt like the one everyone else has used but he didnt like that idea after I told him it needed to be torqued down to about 75ft/lbs. He ran some quick numbers and decided that it wouldnt be strong enogh. He said that he wouldnt just go ahead and make something for this application that wouldnt be strong enough because of Liability but mostly because it would look bad for ARP.....blah...blah...blah. He went out and looked at my car to see where the bolt goes and all of that. He wanted to keep the factory bolt so he can do some stress tests on it. To make it short, He is going to figure out what type of head the bolt will have and how short he can make the height of the bolt head. He will call me Tuesday or Wensday.

I need to find out a couple of things before he calls me back:

1. For thoes of you with the 315's in the back. I need to know the distance between the inside sidewall of the tire and the face of the bracket the bolt goes into. (Please tell me the exact tire size/make/model) I am assuming these are AFS 10.5's if not please state what wheel your using also.

2. IF he can design a bolt that WILL WORK and be stong enough I will let you guys know. I will need to know how many I want him to make. It will probably be a pretty expensive set of bolts but I doubt it will make us all poor men. I will need to know how many people will be interested in a SET(s) OF 2 of these bolts. I will start another thread in the 03 cobra forum and if you all would just count out please. I am just trying to get a "BALL PARK" figure of how many bolts will need to be made. I do NOT know a aproxamate price of a set........but the more the cheaper.
If you guys have concerns or questions or advise let me know.

**DOUBLE CHECK PLEASE
I want to double check that the bolt I got from Ford is the correct bolt.

Part # N802293-s60
12mm x 1.75 x 4.045 UHL
18mm Socket
Could someone please verify the number and or the size/thread.

 

[SVT 03 Cobra]

If he told you they cannot be made strong enough... he is not the bolt guru you think... the stock bolt is grade 10.2 I have found and shipped out about 50 sets of button head bolts grade 10.9... which in fact is stronger than the stock bolt!

Jayson

 

[2F2F]

Bosko said...
I will need to know how many people will be interested in a SET(s) OF 2 of these bolts. I will start another thread in the 03 cobra forum and if you all would just count out please.

So start it already, Bosko. 1. ox03

 

[Bosko]

OKOK.... New thread in the 03 foum... give me a miniute

 

[Fiveohdean]

he is not the bolt guru you think...

J69gordon,

Sorry but Bosko's contact at ARP is most likely correct. Your confusing material tensile strength with bolt strength. You have to consider cross sectional area along with stress concentration factors and fatigue life. The button head bolts that I've seen pictures of on this board appear threaded all the way to the head. This is bad. You now have a stress concentration at the head where the fastener is supporting a shear load and releativly high tensile load due to the high torque value. Add to that the smaller head size giving less area to support the tensile load resulting in much higher stress levels at the bolt head. Given the above these button head bolts will have a fatigue life that is many times less than the factory bolt. IMO as a Metallurgical Engineer these bolts are potentially dangerous to use with out a proper stress study. I would never allow it on an airplane or my car. I'll wait and see what the pro's at ARP come up with.

 

[Bosko]

After I get an apporxamate total of bolts that need to be made. I can then tell him that number and he will get back to me with a quote (price). This does not obligate you to purchase if you participate in the count out thread... It is just a tool to help me/us get a price for the custom bolts. If your not interested dont act like you are.

Here is the link to the thread:

http://www.svtperformance.com/forums/showthread.php?s=&threadid=30317

 

[randy]

The buttonheads I gave Tim at AFS have about a 2 inch shoulder on them, if that is you concern....

 

[Fiveohdean]

randy,

A 2" shoulder is much better than the button head bolt I saw. There must be a couple of versions floating around. You still have to deal with the loss of cross sectional area and potential increase in stress due to the size of the button head. Bosko is taking the right approach. ARP will only provide a fastener that can support the same load as the factory bolt. We will all be much safer with a properly engineered bolt than one that just happens to fit.

BTW, when is the McRat rematch?

 

[Dana]

Fiveoh,
You are probably correct in your assesment of the bolt, but did you include this specific application in your comments? I would have preferred a bolt with a shoulder on it too, instead of completely threaded, but since I don't have any, I think this will do.
Application can have a dramatic effect on whether or not the bolt will perform as intended. The function of this bolt in this application is to clamp a metal tube (poly bushing insert) between two flat pieces of metal (torque box). Don't forget the poly bushing in there too absorbing some of the stress. Because of this, I see the tensile strength being a more significant factor than anything else. I think that these bolts meet that requirement.
Worst case scenario? The bolt breaks and you get mushy suspension and wheel hop again...

Any structural engineers out there?

As for me, mine finally arrived Friday and I plan on using them. If the heads don't snap off when I torque them, they'll be fine.
I'm no engineer, but I've been around a lots of nuts and bolts. HA! HA!

The above is just my opinion and I am in no way qualified to make these statements other than 40 years of experience.

Jayson, the check will be in the mail today.
Thanks,
Dana

 

[Hunter]

Originally posted by Dana
The function of this bolt in this application is to clamp a metal tube (poly bushing insert) between two flat pieces of metal (torque box). Don't forget the poly bushing in there too absorbing some of the stress. Because of this, I see the tensile strength being a more significant factor than anything else. I think that these bolts meet that requirement.
Dana

I agree with you Dana. However, I am still interested in the ARP bolts, just for their reputation.

 

[Black2003Cobra]

Couple of questions and comments for the engineers here. First, I wonder if Ford would actually go out of their way to design a bolt, just for this purpose. Wouldn't they just use an existing bolt that is available that meets the requirements of the application, as that would be way more cost effective? (Compared to a new design.) That said, perhaps the stock bolt that is being used is actually quite a bit stronger than it really needs to be. Certainly if ARP makes a new bolt that meets all the strength characteristics or specs of the stock bolt, it should work just fine, but obviously the price they charge for the new one is going to reflect the cost of all this design work (NRE). Seems to me the bolts to test would be the ones Jayson and Randy found to see if they are up to the task. Maybe then the ME guys here could determine if they'ld be ok for this application. Does this make sense?

 

[Fiveohdean]

Because of this, I see the tensile strength being a more significant factor than anything else. I think that these bolts meet that requirement

You have to consider that Stress = load/area. By decreasing the cross sectional area available to support the torque load the stress at the fastener head has increased. ARP will properly evaluate this and only provide a bolt that is adequate.

If the heads don't snap off when I torque them, they'll be fine

Not necessarily. The increased stress will decrease the fatigue life of the fastener. And if it fails going into turn 9 at Willow Springs you'll wish you waited for the ARP fasteners!

Certainly if ARP makes a new bolt that meets all the strength characteristics or specs of the stock bolt, it should work just fine,

Black2003Cobra,

Your comments are correct. My point is anything that can affect the safety of the car has to be taken seriously. There's a significant difference between these two bolts. I wouldn't use anything that wasn't evaluated properly. A profesional buisness such as ARP has this capability and will give us the correct anwser one way or another. In 13 years of road racing I've had 4 mechanical failures. Three of which were quite expensive. All of these failures could of been prevented If I would have spent another 100 dollars on the car. The piece of mind will be worth a few extra bucks.

 

[s281cobra]

I'll take 1 set

 

[Dana]

fiveoh,
As I said earlier, I am sure you are quite right in your evaluation of the replacement bolts, but

You have to consider that Stress = load/area. By decreasing the cross sectional area available to support the torque load the stress at the fastener head has increased.

Yes but the question still remains: what level does the application require? As stated previously, the factory bolts may be far and above the required level of stress, and these bolts are of sufficient strength and capacity as is.

Practically speaking, and from a layman's point of view, where will the bolts fail at? The junction between the shaft and the head, right? Acknowledging the fact that the diameter has been decreased by about .060 or .070 at this point (I couldn't find my micrometer), is that a significant reduction (approx 10%) and area (approx 20%)? You also have to add back in the higher grade rating factor. Is that enough to cause a failure? Depends on the application.
Further, the threads do not extend fully to the underside of the head, stopping about 1/8 inch below it, and in that respect, equal the design of the original bolt at that point. Granted, the factory bolt's shoulder extends further, but that is not the area we are concerned about, correct?

I am always willing to learn from someone who has expertise in a field and I respect your views. If you find fault in my logic, please tell me.
As a practical exercise, and if you have access to a lab, you might want to conduct some tests to determine the differences between the two designs.

Anyway, you're concern is appreciated, and if these bolts are shown to be deficient, I will replace them.
Thanks,
Dana

 

[Bosko]

**DOUBLE CHECK PLEASE
I want to double check that the bolt I got from Ford is the correct bolt.

Part # N802293-s60
12mm x 1.75 x 4.045 UHL
18mm Socket
Could someone please verify the number and or the size/thread.

****2-25-03

This IS the right bolt it fits. I put in my MM IRS bushings and I put in one of the NEW ford bolts while the irs unit was hanging out and it is correct.

 

[Hunter]

Originally posted by Bosko
**DOUBLE CHECK PLEASE
I want to double check that the bolt I got from Ford is the correct bolt.

Part # N802293-s60
12mm x 1.75 x 4.045 UHL
18mm Socket
Could someone please verify the number and or the size/thread.

Here's what I can tell you about the factory bolt. I have it in my hand. It takes an 18mm socket. The overall length of the bolt is 4.850". The head is .510" tall. The thread length on the bolt is 2.200". The thread O.D. is .467". It has stamped on the top of the hex head ,10.9, and an F inside a circle.

 

[Hunter]

The O.D. of the shoulder on the head of the bolt is .990-.997". It varies. All measurements were taken with Brown & Sharpe 6" dial calipers.

 

[Fiveohdean]

I'm goin to put in another 0.02 cents. This is from a Metallurgical engineering stand point. A stress engineer could give us a more detailed explanation. I'll simply this to two loads on the fastener as follows:

First there is a tension load that runs along the axis of the bolt from torqueing the fastener. The stock fastener, when over loaded, will fail first at the minor dia of the threads. The shank is stronger yet and the head even more robust. The head is much smaller on the buttonhead fastener. ARP is concerned that it may not be strong enough for the specified torque.

Second. ALL the fasteners that Ford uses to attach A-arms, trailing arms, and our IRS assembly have a shank that extends beyond the shear plane of the assembly at least on one side. In this case I'm talking about the plane between the chassis mount and the IRS assy. I roughly scaled the shank diameters from a picture and it appears the cross sectional area of the buttonhead shank is 27% smaller than the factory bolt. To make things worse it also appears that the threads on the button head are now in this plane. So now the shear loads are carried by the threads on both sides of the bolt. Now the shear load is carried by the minor dia of the threads and not the O.D. of the shank. I don't have a bolt to measure but I'll estimate the cross sectional area of the minor dia of the buttonhead is no more than 50% of the cross sectional area of the factory shank. And it gets worse. There is stress intensity factor at the root of the threads that doesn't exist with a shank. This is very bad for the fatique life of the fastener.

Third problem. Since the dia of the button head has been reported as 0.070" less than the factory shank there will be additional movement of the IRS assembly. This will cause greater loads and lower the fasteners fatique life even more. Can't be good for handling either.

My recommendation is not to be so quick to discount ARP's evaluation. Their recommendation will based on sound engineering. When it comes to our safety saving a few bucks isn't worth it.

 

[Bosko]

(Quote: Hunter)
Here's what I can tell you about the factory bolt. I have it in my hand. It takes an 18mm socket. The overall length of the bolt is 4.850". The head is .510" tall. The thread length on the bolt is 2.200". The thread O.D. is .467". It has stamped on the top of the hex head ,10.9, and an F inside a circle.

The O.D. of the shoulder on the head of the bolt is .990-.997". It varies. All measurements were taken with Brown & Sharpe 6" dial calipers.

-----

Cant find my good camera. So please forgive the crappy picture.

My bolt is a little diffrent. Its basicaly a little shorter OAL (4.535").
Head height is the same (~.505"). Thread length (1.70"). Top of the thread to the bottem of the bolt is (1.90") Thread OD (.465"). I have the same stamps on top. The shoulder on the head is the same (.990 +/-.005). 6" Starret calipers.


I think this is the right bolt because it is very similar to yours. But I wouldnt trust the crack head behind the parts counter to tie his shoes right. So if this isnt the right bolt im gonna stab him with it.
The main diffrence is in the "tip" of the bolt. Yours is longer.

 

[Bosko]

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