Gym weights - ballast

[cobra132]

It would be easier to weld mounting tabs on the weight. FMR

[Suck fumes]

You better take the extra time to drill holes in the weight otherwise if you hit something hard enough the weight will become a flying saucer and someone or something is getting hurt.

[GlennCMC70]

Here is what the CCR says about 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Unless superseded by class rules, all ballast shall be solid metal such as steel, lead, or uranium, and consist of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. jam-nuts, Nylock, etc.). All bolts should be grade five (5). There
should be at least one 3/8” diameter, or larger bolt for every ten (10) pounds of weight (e.g. 20 pound block
uses two bolts). Nylock nuts or metal crimping lock nuts should not be reused.

I'm not sure if one 3/4" bolt equals five 3/8" bolts. Just an FYI in case they are strict for your annual.

Marshall Mosty addressed this issue w/ NASA HQ #2 in charge. This rule will not be enforced as written. 1 3/4" bolt will be OK. I have never seen a failure given for ballast mounting.
The CCR really needs to be corrected.

[marshall_mosty]

Here was what I proposed to NASA. I have a copy in my logbook...



From: marshall mosty [mailto:[email protected]]
Sent: Wednesday, December 29, 2010 6:01 AM
To: [email protected]; [email protected]
Subject: CCR Rule (15.20) Ballast

Jerry, John,
I'm not sure who to address this to and wanted an official ruling. 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" dia bolts.

Here are my nerdy engineering thoughts:

A 1/2" grade eight coarse thread bolt has a tensile breaking strength of 21,300 lbs. 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 if two are used.

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? The AI series rules say, "...securely fastened and approved by NASA tech and safety officials..."

Last year I was able to use 2 7/16" dia bolts for two 45lb plates (90lbs total)... but need to stack all three together for my current mounting setup...

I will be finalizing my ballast setup this coming weekend and would like to be able to not have any issues at the first event.

-Marshall Mosty
AI #67
NASA TX


and then Jerry K's response:


From: [email protected]
To: [email protected]; [email protected]
Subject: RE: CCR Rule (15.20) Ballast
Date: Wed, 29 Dec 2010 12:05:46 -0800

Marshall,

Your thinking is sound and the setup you are asking for is acceptable.
Please print this email, in case a local inspector needs to see it.

Jerry Kunzman
Executive Director

[Fbody383]

Marshall, well done.

So the bolts won't break/shear but will the floor pan?. I know Glenn is cautious about ballast to the floor, but the cages are attached there, with support in multiple dimensions and rockers/plinths etc.

What are you using to spread load across the floor plan at the ballast location?

Glenn/Al - can a CMC car add a reinforcement between the OEM seat rails for the purpose of mounting ballast?

[marshall_mosty]

I have a 2" steel strap (1/8" thick) between the two mounting bolts which also extends several inches on either side to spread the load. There is a subframe connector between my ballast and the tranny tunnel. The geometry change of the floor at the tranny tunnel in conjunction with the subframe connectors (welded thru the floor on my car) make that area stiff as hell.

Regarding caution, you can't think of ballast in the same way that you would consider a bolt-in rollcage unsafe. On a rollcage, the small pad is being hammered thru the floor in a roll over accident (very dangerous), but in a forward impact, the bolts will be in shear and will try to "peel" the floorpan like a tin can. Unless you already have cracks in the floor pan or other holes nearby to serve as a point of crack propagation, I'd say the weight we use is pretty safe. The backing plate under the car is the key to being able to transmit the load in an accident.

[Fbody383]

Regarding caution, you can't think of ballast in the same way that you would consider a bolt-in rollcage unsafe. On a rollcage, the small pad is being hammered thru the floor in a roll over accident (very dangerous), but in a forward impact, the bolts will be in shear and will try to "peel" the floorpan like a tin can.

I tend to agree, just looking for "reasonable;" I don't want ballast bouncing around loose either.

[Pranav]

FYI, I never was able to pin down any good used sources, but Walmart had what I needed (1" hole dumbbells) at about $0.75/lb. Academy was right about there in price too.

[kbrewmr2]

garage sales and any of the second hand sporting goods places like Play it Again Sports could help you?

[Pranav]

Meh, didnt have much time to bother trying...