FFR Safety Problem

[Edbo]

Here is a link to a thread on another forum concerning a serious safety problem with front suspension hardware.

IF YOU HAVE AN FFR COBRA OR KNOW SOMEONE WHO DOES PLEASE READ THIS.

http://www.ffcobra.com/ubb/ultimateb...c;f=1;t=027050

Ed

[rdorman]

........ NEVER rely on a nut to stay tight on its own. Forget lock washers. Ever nut on a car that you care about should it fall off (think about how many you don't!) should be a self locking nut (there are half height MAS nuts for the issue with the number of threads left), safety wired and/or locktighted. FFR (and they are not the only ones, in fact I see more critical nuts with nothing more than a lockwasher than those that are properly installed) should get a good wrist slapping for selling pieces with out the proper hardware.

Personally, anything that hold the wheels on the car I don't think should have anything less than NS/MAS fasteners. With that being said, the upper A arm does not have any where near the stress as some of the other fasteners in a car. But then again, the bolts are mounted in double shear, bolt are tension fasteners. At least the are not in shear being used as a bearing surface

It is hard to tell from the picture but are those grade 5 bolts mounted in single shear holding the coil over and the inner lower A arm in place!!!! Those area DO take a lot of force.

On a roll now. Look at the tabs where the upper arms mounts. WRONG. Seems to me that those tabs should be at least half as thick as the bolt diameter. That looks like a lug used on an adjustable sway bar not an suspension A arm.

Now don't tell me that those are fully threaded bolts or that the threads go into the mounting area! I will have to really loose it then! If a bolt of the proper grip length is not available, get the next longest and use washers to properly place the nut.

Is that a cadium plated grade five holding the tie rod to the steering arm! Is that a sperical bearing in the steering arm!

The guy who talked about the grade 5 vs 8 is correct. 8 is so brittle it will usually just fail with no visable signs before hand. Where a grade 5 will often bend first. Depending on the application, that can be a plus!

I am NOT an engineer but it does seem to be some problems here. Or maybe I am just anal!

Maybe I just found a niche for myself here. Bring me a car and I will come up with a proper fastener kits. Available soon!

Rick aka 'never met a fastener I trusted Rick'

[Bob Putnam]

Hasn't anyone ever heard of Stover (prevailing-torque) nuts? They are more secure than nylocks, reuseable and heat resistant. It's what we use for every critical fastener.

[rdorman]

I should have known that Bob uses good fastners. For those of you that don't know the Stover is a ovaled nut that take the circular shape when threads locking on to the bolt. Very similar to the MS21042 grade locking nuts. I don't know the tensile strength of the stover but they say they are good for 400 degrees F. where the MS21042 is for 450 and a tensile strength of 160,000. Now that is one tought nut to crack

You local airport repair shop or a catalog from some one like Aircraft Spruce with fix you up.

Don't forget your washers! A washer under EVERY nut.

Rick

[computerworks]

The upper portion of the tapped nut is compressed to an elliptical form to create a locking zone. The lower zone of the nut maintains its form.
The mating external thread assembles freely in the lower zone of the STOVER locknut. As the mating external thread advances into the nut, it makes contact with the locking zone, expanding it to an almost circular shape. This creates a compressive force on the mating external threads. This compressive force provides the prevailing torque locking action.

[weendoggy]

I have five thousand miles on mine since converting to the newer arms. No problems. I check them every three months or just when I feel like it, just like the other fasteners on suspension. The first problem I saw was the bolts are not the same length for each position so I either moved or bought new ones to make sure the fit was correct. I use nylock now and will most likely go to locknut type when I do some other work. I still think that checking often is a good idea. I do it on my other cars as well.

[cobrashoch]

Excellent thread. (pun intended) This is what this forum is really about. I personally have a "thing" about drilling important bolts and puting in carter pins and then shimming them with washers. Easy thing to do as I have a drill press though.
Bob - I will look at the Stovers and quiz my brother, who happens to be a nuts and bolts salesman for all brands.
Rick- Your not anal, just smart.

[rdorman]

So do we have a nuts and bolts connection? Can he hook us up with good prices on fasteners?

Rick

[Kputz]

Consider this thread the next time you consider an open track event.

[mikiec]

Dave Smith addresses the problem...


http://www.ffcobra.com/ubb/ultimateb...c;f=1;t=027215

Mike

[rdorman]

The Smiths have always impressed me as being good people. Pleased to see that they addressed the issue so quickly!
Rick

[Mike Holt]

For those of us that are of simpler minds what is shear (single or double) in layman's terms? I replaced mine with grade 8 but after reading Dave Smith's response and now this thread, am going to go back to grade 5. I'm just not up on the stresses and this shear term as it applies to this situation.
Thanks

[Richard Hudgins]

Originally posted by Mike Holt


For those of us that are of simpler minds what is shear (single or double) in layman's terms? I replaced mine with grade 8 but after reading Dave Smith's response and now this thread, am going to go back to grade 5. I'm just not up on the stresses and this shear term as it applies to this situation.
Thanks

Mike,

I recommend that you visit Making the Grade A Technical Discussion Grade 5 vs. Grade 8 Fasteners By David M. Potter.

You will find this article is quite easy to understand and dispels the myth of grade 8 bolts being "Brittle". It also shows a bolt in shear and tension loads.

Dave Smith's engineering guys have probably found that the stresses implied for their application do not require a grade 8 bolt. Therefore a grade 5 is adequate.

(If I were you, I would stick with the grade 8 units.)

[rdorman]

Good link Richard! I try to 'over bolt'. If I think grade 5 will do, I use 8. If I think grade 8 will do, I use AN/MAS stuff. Like mentioned in the article, there can be reasons why this isn't 100% the best approach. If a bolt is made for a specifc application by some one like ARP, I use it with out question. They certainly know more than I ever even care to.

I am not sure what nut he is talking about when he mentions "mechanical locking toothed nut". I am assuming that is the type of nut where the bottom of the nut is 'knurled' in order to 'bite' into the material that it is being torqued into. A 'flange lock nut'. If that is the case, I would not use them. First a washer should be present. If there is one then it is only biting into the washer. Which does no good. Plus, should it become loose, there is nothing to stop it from falling off. Now if he is refering to the flexloc type, a type of 'prevailing torque fastener, they stay put.

Carrol Smith's 'Nut's Bolts, Fasteners and Plumbing' is an excellent book. If you have followed any of my posts you know I am a Carrol Smith fan! Following his advise has yet to lead me astray.

Rick

[Mike Holt]

OK thanks Richard. I'll have to look at it when I get home. Our network Nazis have it blocked off here.
Thanks again.

[coyled]

I agree with Richard, use grade 8 if you can. Before I went to road america a month ago, I checked about every nut and chassis bolt on my hi-tech cobra. Almost all are grade 8 on the hi-tech. In checking the cobra over last night, there are a few bolts and or nuts that are no longer tight, that I know I checked last month. So, the moral of the story is to check all of your brake/chassis/steering/suspension components often weather you drive on the street or track, they can loosen. None of us are driving a factory assembled vehicle. Scott

[rdorman]

Many may have already heard this one.

We used to keep bottles of red nail polish around and paint a stripe on the nut to the mounting surface. Quick visual check to see if the nut has come loose. I do the same with the distributor, etc.

That is usually only until I get around to getting all the fastners changed to the correct ones or those I am just to darn lazy to replace!

Rick

[CSX 4027]

I like your photo's
Hey Guys, I've said this over and over...I don't car who's Cobra you have, you have to check and re-check all the time. Only a wrench can tell you if something is backing off. Never take anything for granted. A Lot of horsepower causes all kinds of things shaking loose. It is critical to staying alive in a Cobra or any race car that you check anything bolted on.
I have personally had many things back off after just a few hot laps. You have to learn your car inside and out period.

[Richard Hudgins]

Originally posted by CSX 4027


I like your photo's
Hey Guys, I've said this over and over...I don't car who's Cobra you have, you have to check and re-check all the time. Only a wrench can tell you if something is backing off. Never take anything for granted. A Lot of horsepower causes all kinds of things shaking loose. It is critical to staying alive in a Cobra or any race car that you check anything bolted on.
I have personally had many things back off after just a few hot laps. You have to learn your car inside and out period.

Steve,

I have to agree. There is a page on the JBL site Chassis Maintenance which gives some basic recommendations for the chassis.

You would not believe how many people when speaking to me about the JBL chassis, have said that after reading this section they thought the car would be too much trouble to maintain.

And then they have gone on to tell me that no other chassis requires this maintainance therefore there must be something wrong with the design..

At that point in the conversation I agree with them that the chassis is poorly designed and is certainly not meant for them.

[CRZN427]

I have been away from my computer for a couple days so I just noticed the unanswered question in this thread, that is "what is single and double shear?".

Single shear connections are made when two pieces are connected with a fastiner (bolt, pin, or rivet) and there is only one plane of resistance to keep the parts fastend.

Take a two pieces of flat bar and make a longer piece out of them by bolting them together. To do this you lap one end of one over one end of the other. There are certain rules as to how much "edge distance" you need to have the maximum strength for the connection. Edge distance is the measurement from the edge of the material to the center of the hole that the fastier goes through. (You wouldn't want to use a 7/8" bolt for a 1" flat bar.)

When this connection is made, whether you have one bolt or more, you have a single shear connection between the two pieces of flat bar.

Now, if you take another piece of flat bar and double up one of the existing pieces so that the odd piece is between the other two (one piece of flat bar going one direction from the joint, and two pieces goint the other way, like a clevis connection) then you will have a double shear connection, again the number of bolts does not affect the description.

When the joint depends on the shear value of the fastiner, rather than the tensil strength of the fastiner, a softer bolt works better because it will deform slightly before fracturing through the shear plane.

If the joint depends on the clamping strength of the fastiner then you want a high tensil strength fastiner to achieve the clamping force necessary to carry the loads imposed on the joint. These kinds of joints are commenly found in structural connections in steel structures, especially where a "moment" is present in the joint. (A moment connection will resist twisting of the joint as well as the shear loads. Not twisting around the axis of the member but twisting in the plane of the joint.)