I have considered getting one even though I don't road race like some of you guys. I mostly wanted it because I have been known to slide my truck around when no one is looking. I figure with all the power slides it has to be out of alignment at least somewhat?

 

FYI, Carroll Smith, Mr. Racing Engineer, states in no uncertain terms that single shear must be avoided at all costs.

I don't care either way, but Carroll is pretty well respected.

 

Google search turned it up immediately. Check out the second link for a huge GIF (too big to link here).

 

Did you read his books with engineering judgment or are you just passing on information you read on the internet. Were any sentences before or after his statement? Was context not a consideration?

Hmmm. Avoided at all costs? Would you trust your life with only single sheer connections? Before you say no, go look at your brake calipers and the brackets. Single shear connections. Go look at every car at the next open track event you go to and check their brake caliper connections. Check every GT1 race car, every stock car, whether Cup, Busch, CT, weekly series. I bet 99.9% are single shear. How about connecting the throttle to the carburetor. It's a two lb load (about). Is double shear required? Yes, according to the above statement. How about body panel connections? What about rivets when connecting sheet metal. Single shear when loaded in the correct plane. Bellhousing to engine connection? It handles a shear load, among others and is single shear (even on high HP dragsters). Steering arms to spindle connection? Single shear. Better redesign the steering connections because single shear must be avoided at all costs. How about the upper control arm connections at the frame on many race cars. There's shear on those connections (and tension and compression) and they're single shear connections. I could go on and on, but

How about a few items on street vehicles...
The receiver where it's bolted to your frame? Single shear (better not tow ANYTHING 'cause it's shingle shear). I guess you better think twice about towing 8000 lbs (or more) if you have an F250, because it's single shear. How about the ball bolted to the hitch? Single shear + a bending moment. Bad news, I guess. How about the Lightning's rear sway bar end link? It's a single shear connection where it bolts to the frame. I could go on but it's getting boring.

Been in a high rise building lately? Would you be shocked to learn that most every steel beam connection's shear connections are single shear? Yep. I design thousands myself (very boring to be honest). So, if you don't like single shear, you better stay out of most every new steel structure in Los Angeles.

So, I guess I've been wrong all along, even though I've read Carroll Smith's books because I thought I understood, with Engineering judgment, when single shear is best to avoid. I guess they should be avoided at all costs.

Tim, you're smart. I'll give you a Mulligan and this quote (maybe not exactly correct): Get wisdom. With all thy getting, get understanding.
(The quote from Psalms even applies to Engineering.)

 

Haven't been keeping up with this one ...

Jerry, I have noticed a huge difference in how the rear
acts when I have my slapper bars on, so I now take them off
for the twisties. On the panhard, I think it really helps
at extreme cornering conditions (not street level) and
I would like to see about changing to the left side mount,
because most of the courses we run are biased that way
(Clockwise).

I, too, am thinking about abandoning my truck and the
"teach a pig to fly" quest, and just go buy a Cobra or a Vette.
I love the thrill of keeping up with the track guys though, and
I probably will spend a lot more dough trying to clip a few
seconds off the lap times before I quit ...

Very interesting discussion gentlemen ...

Cliff

 

Excellent discussion

Especially in the Lightning forum

 

An over simplistic look at single vs double shear. Work within the limits of the joint. If your calculated maximum load is 1000 psi and in single shear the joint will handle 2500 psi you will be more than safe. Granted that same joint in double shear would be significantly stronger but not necessarily better. As stated above if properly planned a single shear joint is fine. In a perfect design world where space, accessibility, and weight are not issues everything can have a double shear joint. In the real world that doesn't work so well.

 

Carroll Smith's Nuts, Bolts, Fasteners, and Plumbing Handbook (MBI Publishing 1990), which I understand many race car fabricators regard as a Bible:

p. 72: "In fact, the single shear mount is a crime against nature and a perversion of the bad engineer."

p. 79: "I have only three words of advice when it comes to single shear applications: Don't do it."

These statements are not taken out of context, nor limited in scope or application. They are in the basic section on "Nuts and bolted joints."

I don't know why you attacked me, George. I said that I didn't care and was only repeating what Carroll Smith said. I said that I am completely comfortable with the Ruslow single shear mount. But for some reason you go on for paragraphs insulting my intelligence.

Completely uncalled for. With the above quotes, I have proven my statement 101% true -- the quotes were even stronger than I recalled. If you have a beef, it is with Mr. Smith, not me.

Because you have been kind, helpful, and gentlemanly to me on repeated instances in the past, I will give you a Mulligan on this post.

 

I laughed out loud at this quote: p. 72: "In fact, the single shear mount is a crime against nature and a perversion of the bad engineer."

I have to give my thanks to all the members for making this another informative post - Im really glad I found this site last summer.

Joe

 

Tim,

I was being blunt for a reason. You're smart and I wanted to provide some solid background to help educate you on the subject. I apologize that you took it as an attack - It wasn't intend to be one. I'm sure you would be forceful on a subject regarding law if I was talking about a legal subject I read about in one book and on discussion boards on the internet, a legal topic that was widely spread and misunderstood primarily because the majority of folks spreading the word didn't have the education to know better. Please keep this in mind.

I have the book (and others) you mentioned. And, with education and practice, I am probably more qualified than you to question or understand the intent of his comments. Furthermore, I don't have a beef with his statements because I understand engineering well enough to understand his intent. On the other hand, if someone, who is respected for the knowledge they share (you) provides a undebatable oversimplification of a subject, I'll point it out. There are many times I ignore the statements people make because I don't care what they don't know or don't understand. They're not worth the time. You, on the other hand, are worth it. You're providing a wealth of knowledge for others to learn from. In a way, it's your signature. From my point of view, it's important that I get your attention and help you understand the subject better. Obviously, I got your attention. Yet, I apologize that you took it as an attack. Maybe I should have worded it differently....
(nah.. you're a tough guy and I know of one time in the past that we disagreed on an item and the ensuing dialog was worthwhile, so I'll leave it as is)

Back to the subject :

Carrol Smith made the statements:
p. 72: "In fact, the single shear mount is a crime against nature and a perversion of the bad engineer." & p. 79: "I have only three words of advice when it comes to single shear applications: Don't do it."

Yet, it doesn't mean that EVERY connection should NOT be single shear and if it is, it was designed by a bad engineer. IMO, having a lack of understand is a sign of a bad engineer.

If single shear connections are "a crime against nature and a perversion of the bad engineer", then why didn't he illustrate all the better connection types to use on the commonly used single shear connections: brake calipers, tie rods, harness mounts, flywheel to crank, wheel to wheel hub? If these single shear connections fail, serious injury or death could occur.

For a mental exercise, is there a reason why these important connections are single shear?

(again, sorry I was harsh)

 

Z06's are going cheap now



As for the panhard bar, I pulled mine and sold it off. Driving normally on the street I noticed nothing different. Auto-x, driving on the street how I shouldn't be driving on the street, thats a different story.

 

Oh ... bite your tongue ... I said Cobra First ... Four friends of mine
have traded in their Lightnings for Cobra's .... ain't that a hoot?

 

well fork it over, i'm interested.

At a guess, the load doesn't go any other direction so there's lack of need.

 

Well, George, I accept your apology (despite the fact that I'm not sure how your post could be taken as anything other than an attack). Just like you, my skin is thick, but I still don't back down from a challenge (at least if the adverary is worthy of engaging).

You have more than enough goodwill capital in the Skelton bank to make up for a single post. You continue to be the person on these boards whose chassis engineering knowledge I respect the most -- and one of a handful of road racers whose posts on track events got me bitten with the road racing/suspension mod track in the first place. I am forever indebted to you for both your posts here and your help offline. At this point, I'm not sure you could get on my sh*t list with anything short of physical battery.

Back to the topic:

Smith was using hyperbole to make a point -- a common Smith (and Skelton) tactic. Are single shear applications all bad? Of course not. The photos in Smith's book in the single- v. double-shear discussion almost all show suspension or chassis parts. But, of course, that is exactly what we were talking about -- a suspension component.

Later on p. 82, Smith states that "We chassis and suspension people are so used to double shear bolt applications that we lose sight that, in the real world, most bolts are installed in tension." It is a matter of common sense that a bolt not subjected to shear loads does not need to be in double shear. So that exempts a whole class of application (many of the applications you cite below) from Smith's strong anti-single shear sentiments.

And even a non-engineer like myself understands that using an "oversized" bolt in single shear or a multitude of parallel bolts could be an acceptable substitute for a "normal sized" bolt in double shear.

So, in the interest of not misleading anyone, and in an attempt to reach clarity and consensus, I will amend my previous statement that "Engineers hate SS" to read:

"In applications where a bolt is subjected to shear forces, and assuming a given bolt size and no overriding packaging considerations rendering double sheer impracticable, engineers are reluctant to use a bolt in a single sheer configuration."



BTW, at one point I installed about a 2-3" bolt and had an inch or more of spacers and washers between the Heim and the PHB mount on the Ruslow PHB. And still no breakage.

 

Woohoo, Tim made a typo and I found it!

:P

On the subject of getting rid of the truck for something else, I find myself telling myself the same things (to get a Viper), but then I open the garage and its just beautiful sitting there staring at me. I take it for a drive and I can't part with it.

I'll just need to adjust and figure out how to own 3 vehicles... lol.