All you want to know about bolts...Grade 5 or 8 or aircraft or whatever....

[blykins]

Ron, I don't think it's that easy. Each car is somewhat different in loading and even in use....

I don't think there's a set answer to each category....I think it would be best to just follow manufacturer's instructions.....

If someone is building one from scratch or have a specific question about an individual part, a few of us could help out with an FEA and recommend a fastener.

About the only ones that I could comment on for sure would be engine and rearend components....In those cases I would use ARP fasteners....and probably studs in all cases.

It's hard to pass up fasteners with tensile strengths of 190-210ksi in areas where high axial forces are the highest.

Also, studs lack the stress concentrations of a bolt "head".

[computerworks]

Originally posted by blykins


Ron, I don't think it's that easy.

Sure it is...a generalization in each area will explain the concept.

The pure-race guys will do it their way, regardless..

but for the average builder... a shock mount is a shock mount...a u-joint is a u-joint, etc.

[CobraCooter]

Jerry,

As some others have mentioned the fine threads may not perform as well as the coarse for drilled and tapped holes in softer materials (cast iron incl.) but assembly with a nut is perfectly acceptable providing the nut is the same grade as the bolt. I am not aware of any nylock nuts that are grade 8, I am not saying they do not exist but you should confirm the ones you are using. Using a grade five 5 nut with a gr.8 bolt when torqued may impose excessive stress on the nut casing the nut to elongate or risk thread failure while in service.

It also should be noted that gr. 8 washers should be used with gr.8 nut and bolt assemblies as they have a higher yield and will not (should not) deform when torqued.

Nylocks and most lock nuts, and even lock washers are designed as single use and should be treated as such for critical apps. A thread locker such as Locktite red or blue will add plenty of longevity to the fasteners tightness and resist the rigors of excessive vibration and temperature swings. Use the red for the critical jobs that frequent disassemble is not intended and in higher temp. areas. A word of caution with the red, it locks up very tight and often may require the use of heat (600- 800 deg. F) to breakdown the hold. Use it for things you don’t really want to take apart ever or for a very long time. Use blue for the rest. NOTE: threads must be clean and free from oil and grease. I prefer using locktite to locknuts as they damage the treads and if the bolt dia. is a little light for duty it may be the leading cause of failure.

As far as the frame and suspension components checked, great idea… LPI (liquid penetrant inspection) should be sufficient. This is applied to all the welded joints to visibly inspect for cracking is an excellent method for this application.

A word of caution in having suspension parts plated. Many suspension parts are made from higher strength steels and have some degree of heat treating. If a part is heated to or past a specific value for that material, it’s properties can and will be seriously affected.

As far as material selection for the critical suspension pieces, I am assuming you are refering to control arms and spindles. The materials you have listed, forgings (assuming steel), billet alum., and fabricated tubular steel are all viable selections. More importantly is their design, stess levels, and stiffness to do the job. Stiffness is required to keep the geometry in order under heavy load (cornering, braking), their design should provide for as low as possible stress levels to give the greatest fatigue life.

I hope this helps.

Mark

[What'saCobra?]

Mark
"A word of caution in having suspension parts plated."

So, while this is not a bolt issue, with apologies i would more than second that recommendation as a safety point. Current uropean build schedules of serious 'at the limit' race cars for both Historic and Professional suspension bits are more and more divorced from the use of chrome suspension bits. They have been found faulty, mostly due to hiding the horizontal creep of oxidation under the chrome plating and/or its underlying bonding layers. Other degraded surface effects have also been noted, some of which can affect strength.

The currently most popular material surface protection product, also particularly recommended by the FIA, is Kephos; a satin black very thin (0.0005 - 0.0007) phosphate coating that has remarkable capacity to resist horizontal rust creep from a crack or injury to the surface (eg: stone chips). Keco Inc. is located in Indianapolis and also has other helpful products and good engineering support.

http://www.kecocoatings.com/Products/Kephos.html

Kephos also easily allows normal crack testing with penetrant-type detector systems. including easy testing while assembled. It also looks nice.

[Byots]

I just verified from a list of approved general use fasteners for a particular aircraft company that the lowest strength steel bolt listed is 125 ksi FTU, which is about grade 8. Some stainless bolts shown are a bit under that, but stainless is not widely used, for one reason I recall there being a galvanic compatability issue with aluminum (cad plated steel is better).......

A note on shear; in practice it's difficult to have a pure shear bolt loading - the typical failure mode for most bolts loaded in "shear" (usually as single shear) will still be a bending tension failure under the head or at the thread because the bolt cocks in the holes and tries to pry the head and nut off. Very tight bolt to hole clearances with double shear loading are important to experience pure shear conditions. That said, aircraft "shear bolts" are intended where shear is the primary loading and are typified by having shorter heads and smaller under head radii, which would be more critical for pure tension applications.

On studs vs bolts, I don't think I'd say bolt heads fail before the thread, on a well designed bolt I think the failures occur at about the same loading. Studs are mainly beneficial because they minimize the wear in the parent structure from repeated removals and there may be some increase in preload, or less preload scatter, for a given torque. Lower torsional load in the stud as a result of this may also provide slightly greater strength.

[jerryweichers]

Cobracooter,I buy all my '' elastic stop nuts '' and''all metal stop nuts'' from Aircraft Spruce in Corona California. all of which are AN . They are an excellant source for fasteners and list the specs on all their products I also use only their flat washers in AN grade.their catalog is well worth the price. Again let me state of course there are applications in a car for coarse bolts but in my oponion they should be limited to use in castings ,engines ,etc . i prefer studs however due to their superior clamping ability
my experiance is in vintage race and hi perf. cars I realize their are always advancements in technology that should be considered.
As to plating suspension componets..... chrome plating is for show cars in my opinion. One, due to the fact that the part needs to be baked immediatley after plating to avoid hydrogen embrittlement ( by someone who knows what they are doing) and you cannot crack check a chrome plated part . if you want to plate i would use electroless nickle as you can crack check it. I once had to throw away every suspension componet of a lola T70 I was restoring as it had all been chomed by a previous owner and I wasn't willing to take the chance.
Now as to stainless . most stainless is built for commercial application so i would do some serious investigation before you spend your money on it . Stainless is to my understanding alloyed with chromium and nickle to achieve its corrosion resistance while stainless may be harder it may not be better in a racing application if not welded properly you have a time bomb waiting to go off ,add that to the fact that fabricated/ welded stainless parts may not hold up in high stress applications subject to lots of vibration or shock over extended periods. I , myself have never seen a major sports/ road race constructor such as Ferrari,Lola,or Mcclaren, or aircraft manufacturer build a platform on welded stainless tubing .
As to machined billit vrs. forging vrs. welded tubing by an experienced fabricator ,my choice would first be a forging partly due to the fact that the grain of the metal in the forging process lines up with the shape of the part (where billit features straight grain) which is in my opinion not only stronger but also not as prone to cracking at the inside of a radius.I personly prefer proper tube fabrication over billit aluminum. my opinion of billit is it is much cheaper to make however pretty and easy to polish i don't think it makes for a stronger part.
someone asked about flat washers . i suggest AN flat washers due to the fact the hole is radiused to fit the head of the bolt hardware washers are not and are softer which causes them to crush and also yield under high stress applications again i feel it worth the effort to fit the bolt for grip ,leaving no moving parts exposed to threads, an AN washer under the head and AN grade locking nut and one last aside deburr everything ,regards, jerry

[CobraCooter]

Jerry,

I respect the choices you have made with regards to hardware, although for the most part in my professional opinion is overkill and not required. If it gives you that little more comfort factor, than great. But I believe you are doing the community a disservice stating that only gr.8 or higher will do. It is simply un true.

For the most part this forum is comprised of people trying their best to build and enjoy the best Cobra they can afford, and are very proud of their accomplishments. There are very few that are trying to build a car to win the 24 hours of Leman. Until you sit down and calculate the dynamic loads and clamping force required for each bolted connection, apply a service factor, and evaluate all the other factors to that specific application I don’t think you or anyone else can say it must be gr. 8. or AN or even gr.5 for that matter.

The main point of caution that I am trying to address with regards to plating is that there is a major difference in having something like a roll bar or side pipes chrome plated to parts that have been engineered with higher strength alloys and parts that have achieved strength through processes such as work hardening or tempering. This engineered strength can be easily destroyed by having it hot dip plated. A very good example of this that most may be familiar with… Tractor Trailers (ie. 18 wheelers) many if not all tractors on the frame connecting the cab to the fifth wheel is a sign “DO NOT WELD”. This sign is there because this frame component is constructed of a high strength steel and was engineered and manufactured to have a higher yield strength than A36. This is strength was achieved by both the initial material selection and heat treating. Any welding on this component would induce heat into the material and affect its carbon content and alter its grain structure, effectively weakening the material which would lead to fatigue cracking, to name one. It is very dangerous to heat components of this type beyond 800 deg. F be it localized through welding or heating something red hot with a torch to loosen a rusty bolt, or the entire part without first knowing exactly what material and strength has been worked into it.

Stainless steels are great alloys, but with anything structural these parts are engineered. You cannot say that stainless steels have no place on a car because so and so doesn’t use it. And as any weldment goes, stainless, carbon steel, alum, and others, if it is not done right… it may fail. The applications and companies you have listed would not consider stainless steel for one simple reason, weight. Aluminum is approx. one third the weight of stainless steel and various grades of alum. have similar yield strengths.

As far as your preferences for materials, it is misleading to say that one is better than the other with out a specific design.

The bottom line is that you cannot state that one material is better than another with out evaluating both the engineering and economic requirements of a given part.

I am sure you all your gr.8 UNF and AN grade hardware is not bolted to a tubular titanium frame and control arms, with a gold wiring harness. But why not, isn’t that better?

Mark

[CSX 4027]

In this discussion of bolts it has been stated that race cars use only
grade 8 or better. It is important to remember that REAL race cars and
street cars are very different. The biggest difference between them is
REAL race cars are constantly being taken apart and checked
(magnafluxed, zyglowed, etc). Street cars on the other hand are mostly
drive and forget. When is the last time you saw a Can Am car drive over
a pot hole? With strict maintenance, parts (read bolts) can be made
lighter and smaller on race cars. With lighter and smaller bolts and
known loading (because they are on race tracks) bolts can be safely
stressed higher. Making blanket statements saying “grade 5 bolts will
kill you” shows complete ignorance of even the most basic engineering
principles. Typical race cars use 3/8 or smaller diameter bolts for
suspension pick up bolts. The original Cobra uses 5/8 bolts. If you do
the math, you will see that a 3/8 grade 8 bolt is much weaker than a 5/8
grade 5 bolt. Hint, the 5/8 bolt has 2.78 times the area as the 3/8 bolt.

The 289 Cobra are loaded in single shear. Did you not know that the lower control arm bolts of the
427 Cobras are loaded in double shear? Yet the bolts are the same size.
Not only are the bolts on original Cobras NOT grade 8 they are Witworth.
These non grade 8 bolts won LeMans, the Targa Florio, etc …
in single shear.

FYI as for stainless. Rocker arms and knock-offs have been stainless for a while with Shelby. Also, NASCAR & Sonny Bryant
has been using Billet Cranks as opossed to forged for a long time as well. Why?

[CSX 4027]

How many of the original Cobra's raced on the 1/4" bolts that held the seats in the car? All?

How many of you now still use the same 1/4" bolts to hold the seats to the car or the seat tracks to the car? Do you think grade 8 would benefit there? I doubt it. That seat will leave regardless.

[Jamo]

Hmmm...wondering if that depends on the size of one's a$$.

[CSX 4027]

If you leave the car in an event(oops..)
...I will make sure to testify that you were not a suicide bomber.


....you are huggable..

[mikiec]

Steve,

You have thrown in other terms I am not familiar with..

The terms are double shear and single shear.

Please explain.

thanks,
Mike

[CSX 4027]

Single Shear = Bolt cantelevered out and supported on one side only.
Double Shear = Bolt supported on both ends.

[rdorman]

Good 'nuts and bolts' type discussion

Personally, I just read Smiths recomendations and go with it.

With out a picture, try and visualize shear versus tension this way:
- Tension, grab a bolt on with each end with your hands, try and pull the bolt apart (stress along its length)
- Shear, grab a bolt in both hands, hands touching and try and tear the bolt apart by moving one hand forward and the other to the rear (stress along its width)
- Double shear, Hold the bolt in one hand, on the ends, between two fingers. Grap the bolt in the middle of its length with the other hand, try to pull the bolt apart moving the hands like in single shear.

Typically, a head bolt would be in tension, a wheel stud in single shear and a bolt holding a spherical end to the chassis in double shear.

Rick

[What'saCobra?]

CSX
"When is the last time you saw a Can Am car drive over a pot hole?"

You might like to look at the alligator teeth along both sides of the double chicane at the end of Monza's high-speed straight. There are things worse than pot-holes...

See the yellow car here:

http://www.clubcobra.com/forums/t63585-15&pagenumber=4

The following high-speed right turn, Curva Grande, is taken at about 135 to 145 mph, so nice double-sheared suspension bolts do have their place, no?
----------------

Pst:
No Shelby Team Cobra ever won the Targa. They only ran there as a Shelby team once, in 1964. 2nd in class was the Guerney-Grant car and that was good for 8th overall.

Oh, yes, and the other 4 Cobras DNF'd, that is...they broke. The Targa was/is notorious for potholes, rough sections and ten laps of a very long 45 mile street course every Italian schoolboy memorized by heart; but few Americans had experienced, let alone memorized.

A nicely driven GTO took first in GT (the Cobra's legal FIA class at the time. And they regained the championship leadership, at least temporarily, with another GTO taking 5th.

This was a serious upset, as the prior month Cobras swept the Sebring 12-hour with 1,2,3,5,6,7 and 12th in GT.

In the end, the 289 GT lost the 1964 FIA GT Championship to Ferrari and the Shelby Team never returned to the targa Florio.

Maybe they could'a used better bolts?

[CSX 4027]

If you are referring to rumble strips, they have rounded corners as to not upset a suspension. I am referring to actual pot holes that would cause a tire to compress and blow. The ones on the east coast sometimes require the payment of a toll upon exit.

[What'saCobra?]

Please look at the picture again. They don't just rumble. They are large and sharp, particularly at the top. They smash the blooming' hades out of the rims, tires, bolts, rod ends, radius rods, chassis, radiator boxes, air flow control 'devices', brake ducting and anything else they get near...

The energy and vibration is enormous at speed, but there are speed/time advantages in going as high as you dare and reduce the turn radius of the corner, inside the apex. Inches, man, inches.

It is the same at Brno, the Nurburgring and many other tracks in urope.

Some 'rumble' strips...

[CSX 4027]

..so your saying if you stay on the track, you'll be OK and if you go off, then the shear factor will have little consequence as compared to the shreaded wheat tires and oval shaped wheels.
I knew I heard something about about the pluses of staying on course.
Can you imagine how this guy felt?

[computerworks]

...stay on topic, boys.

[What'saCobra?]

OK