'84 Dodge Rampage Build Thread

[SteveM]

At the upper side of the seat frame, in the headrest area, I used 2 more 1/8" thick steel brackets welded to the cage, and secured with the same type of flat head grade 8 bolts countersunk into stringer washers.





These brackets include an intentional bend.  My intention here is that if there were a hard impact, that the bent brackets would provide an opportunity for the bracket to continue bending, absorbing some of the energy associated with a hard hit.



I hope I never get the opportunity to test this theory.

[Peter Jack]

Nice work Steve and well thought out. 

Pete

[SteveM]

Thank you, Peter.  This website makes it possible for newbies like me to get started in the right direction, and hopefully stay on path.  I've had a nearly lifelong dream of going to Bonneville.  Without the ability to get ideas from other likeminded folks, "borrow" techniques from them, and just generally bounce ideas around, this would remain just a dream.

As it stands now, I have a pretty tight timeline that needs to be adhered to if I am to hit the salt in 2013.  I fully intend to do so, so I need to keep cracking at it.

I think that posting pics and getting feedback on this forum helps keep me moving forward, as well.


Thanks again,

Steve.

[jauguston]

I am not a race car builder but have some experience building ultralight aircraft. Whenever I see someone mention using Grade 8 fasteners I question the choice. Grade 8 fasteners have virtually NO elasticity. They will not bend when stressed they just snap. They are a big no/no in building airplanes for that reason. Grade5 or AN are safer.

Jim

[SteveM]

 Potential trick question - at what stress level do you expect a grade 8 fastener to snap?  How about a grade 5 fastener?

[Captthundarr]

Lets throw some more in the mix. How about in single shear or doudle shear?

[Jon]

Very nice work as always Steve, enjoying your build.

I don't know the math but those bolts will stand up to anything those brackets can throw at them.


Cheers
jon

[Peter Jack]

I almost always use Gr. 5 because they're tougher than the base material in most applications and they are a little more malleable. Much more of a problem are the counterfeit bolts in all grades that don't come close to the required specs. They're even made so they appear to be AN or MIL spec. 

Pete

[SteveM]

I'm just having a little fun with the bolt grades and material properties discussion.  This is an age-old debate (grade 5 vs. grade .  Peter, you are correct regarding the toughness of the bolts.  You are speaking of toughness in the defined metallurgical context (ability to absorb energy when an impact load is applied), not in the "World's Toughest Man" context.

In this application, I chose to use the flat heads so they could be countersunk into the washers.  At the 4 mounting locations on the seat bottom, I wanted to have as smooth a seating surface as possible.  These are "Holo Krome" made in the USA grade 8 bolts.  I trust that they will meet the minimum ultimate tensile requirements of 150,000 psi.  Shear strength is directly related to tensile strength.  Grade 5 hardware requires a minimum UTS of 120,000 psi, so can be expected to have a proportionally lower shear strength.

Toughness is generally a trade-off between ultimate tensile strength (UTS) and %elongation before failure for most steels.  (Disclaimer for materials with ductile-to-brittle transition temperatures that might be encountered).  No such temperatures are expected in Wendover, Utah during the summer or autumn months.

Grade 8 = stronger.  Grade 5 = tougher.

[manta22]

SteveM;

There is "more to the story" that just the fastener grade. "Grade 8" or "Grade 5" is only a general guide to the choice of a bolt. While the SAE grades are specified as to their properties, many--if not most-- manufacturers have little quality control in place so the actual properties of the bolts can vary over a wide range. When you receive a fastener with no threads, but nicely plated & packaged, you have to question if that manufacturer has any quality control at all. 

There are a few manufacturers whose commercial bolts I'd trust-- SPS, Holo-Chrome, and Allen make good stuff.

If you want a fastener whose properties are very well specified and produced unded rigid quality control, look to the aerospace industry. Those fasteners are really expensive but they are strong and reliable. If your life depended on a fastener, you wouldn't want to buy it from just any hardware store. If you are careful and well-informed you can find some excellent hardware on the surplus market at decent prices. I'd suggest having a look at Carol Smith's book on fasteners. There are very good reasons that an F-16 or a 787 isn't held together with Ace Hardware bolts. For non-critical applications, AH's stuff is just fine, though.

One final thought-- even the finest fasteners can be ruined by being mis-applied.

Regards, Neil  Tucson, AZ

[Rex Schimmer]

Steve,
I am with you regarding bolts specifically socket head capscrews. You are specifying Holo Khrome as the manufacture so they are USA made and although they do meet the strength requirements to be "Grade 8" but because of the material and the processes that they go through they far exceed any "standard" Grade 8 hex bolt in toughness and fatigue. I am a big user of SHCS and have been since I was designing machine tools at Pratt and Whitney 45 years ago.

Looking at your cage build I have come to the conclusion, and you may have stated earlier in your build thread, that you have made a CAD or Solid Works drawing of your cage as I am impressed that you can pretty much manufacture your cage parts more or less "off site" at your place of employment and then bring them to your shop and assemble into such a nice looking fabrication. I, regretfully, am a relic of the cut and fit age, shop engineering, and if I had made one of my "pencil CAD" drawings of the cage I am working on I still could not have been able to as accurately detail the individual tubes as I assume you have. I have to say I am impressed .

Rex

[SteveM]

No CAD drawings here or solid modeling programs, just some graph paper, pencil, and an HP-15C calculator.  I'm a metallurgical engineer by profession - not sure if that helps or hurts, but I like to think that I have a decent understanding of how metals behave.  Holo-Krome bolts are probably not as good as some aero-space stuff, but I have ready access to these, and don't have ready access to aero stuff.  I feel pretty good about this "build", and hearing that other racers think the cage looks good instills more confidence.

The eight grade 8 fasteners holding the seat in place should do a fine job - that's my personal opinion, and would be my professional opinion as well.

Thank you very much for the kind words, Rex.  Don't be fooled by the pics, plenty of parts get modified or finalized in my garage.  I spend a lot of time sweeping up grinding grit and making sure that no metal shavings get tracked into the house.  As they say - if Mama ain't happy, nobody's happy.

My wife is very supportive of my hobby - I'm a lucky man.

Steve.

[Rex Schimmer]

Steve,
Glade to hear you are wearing out some 1/2 round files too!!

Rex

[gkabbt]

At the upper side of the seat frame, in the headrest area, I used 2 more 1/8" thick steel brackets welded to the cage, and secured with the same type of flat head grade 8 bolts countersunk into stringer washers.





These brackets include an intentional bend.  My intention here is that if there were a hard impact, that the bent brackets would provide an opportunity for the bracket to continue bending, absorbing some of the energy associated with a hard hit.



I hope I never get the opportunity to test this theory.

Steve,

I really like the way you attached the top of the seat and it looks to be safe in the event of an incident (good thinking).
I was waiting to see how you were going to do your mounts before I did mine.
Since we have been share ideas, I am going to do something similar to my seat mount so I can get rid of the 1/4" plates that are there now.

As usual, good job and keep up the good work,
Gregg

P.S.
Many Thanks P.J.

[SteveM]

I dropped the cage back into the Rampage for what I hope is the second-to-last time on Monday evening.  Here's a pic from the "Professional Idiot, Closed Garage, Do Not Attempt" category.



I made an extension for the lifting arm of my cherry-picker hoist to allow the cage to be set in place.  Without the arm extension, the legs hit the center support of the rotisserie before the cage gets into position.

My short-term plan is to tack the rear feet onto the cage, contour the base plates to match the floorpan, then pull the whole cage out one last time for painting.   I plan to paint the cage on Saturday.  If I have enough time allocated, I'll also paint the inside of the passenger's compartment before setting the cage back in for final welding.

Steve.