CCR Rule (15.20) Ballast

[marshall_mosty]

The CCR's are kinda fuzzy, since they are written around 3/8" bolts for 20lb plates...


If I'm going to mount 135# of ballast (rectangular plates), how many fastener's do I need to run and what size? I'm going to be drilling them and want to make sure they are properly secured. I'm thinking two grade 8 1/2" bolts.


Here are my nerdy engineering thoughts:

A 1/2" grade eight coarse thread bolt has a tensile breaking strength of 21,300. According to the Maximum Distortion Energy Theorem, to convert to shear breaking strength, multiply by .577 This gives 12,290 lbs per bolt, or 24,580 lbs total bolt strength.

A conservative approximation for a "worst case" crash with a concrete barrior at 150mph would be approx 80g (3 ft compression impact in 135 milliseconds from 150mph to zero, assuming linear deceleration), so the 135 lb plate stack will weigh 10,800 lbs during the impact.

Therefore, if I run the two bolts as mentioned above, I will have a factor of safety of approx 2.27.

Should be plenty, right?

[GlennCMC70]

Do the AI rules address ballast mounting at all? As they would overrule the CCR's. And I know the 2011 rules are not out. How about the 2010?

[marshall_mosty]

It just says, "...securely fastened and approved by NASA tech and safety officials..."

Last year I was able to use 2 7/16" bolts for two 45lb plates... but need to stack all three together for my current mounting setup...

So....

[GlennCMC70]

The CCR says.....
15.20 Ballast
Unless superseded by class rules, all ballast shall be solid metal such as steel, lead, or
uranium, and consist of a minimum of five (5) pounds per piece. Each piece should be
bolted in place with through-bolts, fender washers, and a locking-nut / system (e.g. jamnuts,
Nylox, etc.). All bolts should be grade five (5). There should be at least one 3/8”
diameter bolt for every ten (10) pounds of weight (e.g. 20 pound block uses two bolts).

I find it odd that that NASA would require 15 3/8" bolts to hold 150lbs of ballast. They are spec'ing grade 5 though. In fact, they word it to lead you to think only grade 5 is allowed. I was thinking grade 8 would be better and possibly require fewer bolts.
Worth an email to NASA HQ.

[GlennCMC70]

E-mail sent. I'll allow Todd a couple days to respond before I go over his head.

[kbrewmr2]

the CCR version isn't a mistake, changed last year - luckily TT, PT, and ST chose to override it to something reasonable. Many other classes are choosing to do the same so I hope Todd sees the light and helps you guys out

[marshall_mosty]

E-mail sent. I'll allow Todd a couple days to respond before I go over his head.

Oops... Since this was CCR's, I went to the "big guys" at Nationals...

[GlennCMC70]

E-mail sent. I'll allow Todd a couple days to respond before I go over his head.

Oops... Since this was CCR's, I went to the "big guys" at Nationals...

Please use your chain of "command" when and if at all possible. In this case, myself and Rob. I know Todd is not the most available person, but give him a chance.

By all means, post up the responce you get.

[cjlmlml]

http://wiki.answers.com/Q/Why_is_the...nd_in_business





I posted the above so everyone would know why there is a chain of command, you can thank me later Glen.

[marshall_mosty]

E-mail sent. I'll allow Todd a couple days to respond before I go over his head.

Oops... Since this was CCR's, I went to the "big guys" at Nationals...

Please use your chain of "command" when and if at all possible. In this case, myself and Rob. I know Todd is not the most available person, but give him a chance.

By all means, post up the responce you get.

Glenn,
Sorry, you mentioned NASA HQ... that made me believe I needed to talk to the California boys...