69 AMC Javelin Project

[csangster]

Originally Posted by Jtomas801

Okay, so it sounds like its trying to find a rod that will support the load more than the bolt (5/8 or 3/4)


I am trying to learn a little bit of this, so if you see any thing wrong please let me know.

While searching through google, I found the equation for shear strength:

tensile strength pounds/in2 x cross sectional area.

In the case of a -10 an bolt with a tensile strength of 160,000 psi and a cross-sectional area of 0.306640625 in2 at the full diameter

160000 pounds/in2 x 0.306640625 in2 = 49062.5 pounds

If 49062.5 pounds is single shear, you double it to get 98125 double shear, right? That should be the amount of force to shear the bolt?


Thanks,
Jon

Good evening,

Let me first say that I am extensively impressed with this build thread and all of the modifications. I have been wanting to build a Javelin just like this, and yours is one of inspiration..........very nice.

In a small effort to help make sure you build goes off well, I feel compelled to tell you that the above strength calculation is incorrect (I am a registered Professional Engineer and I perform these types of calculations for a living).

You are mixing your strength numbers when performing this calculation.

If you are trying to determine the load carrying capacity of your fastener in shear, you need to use the shear strength of the material, not the tensile strength. These are two entirely different measurements. The good thing is you can look on a website called MatWeb, find the material in question and it will give you nearly everything you need to know about that material, CTE, yield strength (tensile and shear), ultimate strength (tensile and shear), thermal conductivity......the list goes on.

The next thing you are missing is your factor of safety. You need to carry a factor of safety on your design to cover anything that you may not have thought about or considered. Generally, you can pick a factor of safety from 1.1X all the way up to 16X or more.........it just depends on how much risk you think you can take. For a suspension component, a factor of safety between 2 and 4 is a good place to start......the Carroll Smith's book that was mentioned earlier will have a better guide for selecting the factor of safety for your application.

As far as single shear vs. double shear is concerned, the shear strength of the fastener is what it is, when the fastener is in single shear, you are loading only one shear plane in the fastener, when the fastener is in double shear, you are loading two shear planes, thus doubling your strength of the fastener in shear.

While you are looking at shear strength of the fastener, keep in mind that the fastener is also stressed in bearing, you will need to make sure that the bearing surfaces don't have too much stress in them and causing plastic deformation of the fastener or the suspension components.

Additionally, the above calculations are all static calculations and do not apply to dynamic load cases. Sometimes you can increase your factor of safety if you are unable to properly calculate the dynamic stresses in a joint.

Dynamic stresses are important because they can cause failure by fatigue of the material, not by failure at the ultimate strength.

I'm rambling too much, I just wanted to make sure you taking everything into consideration for your build so something doesn't break on you and give you headaches later.

Again......very impressive and inspirational build.

Cheers,
Chris

[coolwelder62]

Jon,I hope the shock install is going well for you. Scott M.

[Jtomas801]

Originally Posted by coolwelder62

Jon,I hope the shock install is going well for you. Scott M.

Shoot, I haven't touched the car in a few weeks but I have been working making some money. This weekend I am working Saturday and going to the NHRA finals on Sunday. Hopefully after we get a couple of these big jobs done I can get back working on the car in a couple weeks.

I hope Summit racing has some good coupons again like they did last year, I am thinking about getting a t-56, or if I can make up my mind on what front brakes I want to get.



Again Scott, congratulations on your latest build, the car came out great and it sounds like it performed really well for the lack of testing on it. I can't wait to see what the next build looks like.

Thanks,
Jon

[Jtomas801]

Originally Posted by csangster

Good evening,

Let me first say that I am extensively impressed with this build thread and all of the modifications. I have been wanting to build a Javelin just like this, and yours is one of inspiration..........very nice.

In a small effort to help make sure you build goes off well, I feel compelled to tell you that the above strength calculation is incorrect (I am a registered Professional Engineer and I perform these types of calculations for a living).

You are mixing your strength numbers when performing this calculation.

If you are trying to determine the load carrying capacity of your fastener in shear, you need to use the shear strength of the material, not the tensile strength. These are two entirely different measurements. The good thing is you can look on a website called MatWeb, find the material in question and it will give you nearly everything you need to know about that material, CTE, yield strength (tensile and shear), ultimate strength (tensile and shear), thermal conductivity......the list goes on.

The next thing you are missing is your factor of safety. You need to carry a factor of safety on your design to cover anything that you may not have thought about or considered. Generally, you can pick a factor of safety from 1.1X all the way up to 16X or more.........it just depends on how much risk you think you can take. For a suspension component, a factor of safety between 2 and 4 is a good place to start......the Carroll Smith's book that was mentioned earlier will have a better guide for selecting the factor of safety for your application.

As far as single shear vs. double shear is concerned, the shear strength of the fastener is what it is, when the fastener is in single shear, you are loading only one shear plane in the fastener, when the fastener is in double shear, you are loading two shear planes, thus doubling your strength of the fastener in shear.

While you are looking at shear strength of the fastener, keep in mind that the fastener is also stressed in bearing, you will need to make sure that the bearing surfaces don't have too much stress in them and causing plastic deformation of the fastener or the suspension components.

Additionally, the above calculations are all static calculations and do not apply to dynamic load cases. Sometimes you can increase your factor of safety if you are unable to properly calculate the dynamic stresses in a joint.

Dynamic stresses are important because they can cause failure by fatigue of the material, not by failure at the ultimate strength.

I'm rambling too much, I just wanted to make sure you taking everything into consideration for your build so something doesn't break on you and give you headaches later.

Again......very impressive and inspirational build.

Cheers,
Chris

Thank you very much for the information and the nice words. I am going to have to research this a bit more. I believe that the Lateral Dynamics 3 link uses 5/8" bolts with 5/8" hole and 3/4" shank, so at least I know that set up is tested and works.

Thanks again,
Jon

[csangster]

Originally Posted by Jtomas801

Thank you very much for the information and the nice words. I am going to have to research this a bit more. I believe that the Lateral Dynamics 3 link uses 5/8" bolts with 5/8" hole and 3/4" shank, so at least I know that set up is tested and works.

Thanks again,
Jon

Jon,

Sounds like you have it all under control. I apologize if I was spewing out too much information there.

I will watch your build with great admiration as it follows......I may use some of your ideas, if you don't mind.

Cheers,
Chris

[Jtomas801]

Originally Posted by csangster

Jon,

Sounds like you have it all under control. I apologize if I was spewing out too much information there.

I will watch your build with great admiration as it follows......I may use some of your ideas, if you don't mind.

Cheers,
Chris

No need to apologize, if I post something wrong or build some thing that might not be strong enough, I'd rather some one let me know now, before the car ever gets driven or some thing bad happens. So I really appreciate your advice.

And of coarse, you can use any of my ideas, because at some point I got them from some one else, lol.

Thanks,
Jon

[coolwelder62]

Thank's Jon,Albert car turned out good,and worked well.My son Brandon is wanting a car so maybe will help him with something.I think I will put the Javelin on hold for now.Need to sell the orange camaro first.

[Jtomas801]

Well yeah, you got to save up for the 9000 rpm supercharged, drysumped, ls engine for the Javelin first, lol. What ever the car is, it will be a awesome build.

Thanks,
Jon

[Bryce]

Originally Posted by Jtomas801

Thank you very much for the information and the nice words. I am going to have to research this a bit more. I believe that the Lateral Dynamics 3 link uses 5/8" bolts with 5/8" hole and 3/4" shank, so at least I know that set up is tested and works.

Thanks again,
Jon

FYI

Example 4130
Tensile Strength, Ultimate 841 MPa 122000 psi
Tensile Strength, Yield 655 MPa 95000 psi

[Jtomas801]

Well, I broke down. I am now an LS engine owner.

I just picked up this LS2 with less than 30k on it, came with a truck intake (not gonna use that), a LS7 cam with springs (stock ls2 cam is still in engine) and I believe ls7 injectors for $1500 off craigslist.



Seemed like a good deal, now I got to figure out what to do with it. Get a intake and throw my Dad's old 750 Demon on it or go efi. Hell maybe some ls3 heads.

But first, I got to get a T-56, an oil pan and a quicktime bellhousing. So I can position it in the car to make the engine and transmission mounts.


Now I have to sell all my AMC engine stuff, Who needs a all standard 390?

Thanks,
Jon