Anti-blowback device

While putting together my blown altered, I totally missed this in the rule book. I have hunted examples and can't seem to find anything on the 'net. I'm nearly ready to roll and am not sure what to do with this. I have the flex plate shield and the trans blanket already. I will be in the AA/AM altered class. Any one have a picture I can use for an example? Any help would be appreciated

2.1 ANTI-BLOWBACK DEVICE

If mandated by Class Requirements a brace or device must be installed that will prevent the bellhousing or adapter shield from being blown rearward in the event of flywheel and/or clutch explosion. Material required is 4130 chrome moly (or Reynolds 531), minimum size is .875-inch (22.2 mm) O.D. x .083-inch (2.1 mm) wall tubing with 3/8-inch (9.53 mm) fasteners. Ball-lock pins prohibited.

 

Dave if you have no clutch you don't need these.

 

I think that's why I missed it the first time through the rules. But then reading it again, I saw that it said "in the event of flywheel and/or clutch explosion." I wasn't sure if they meant "flywheel" to also include the flexplate.

 

Flex plates don't blow up, but to be sure call NHRA tec.

 

Tubes

How are you planning to control the movement of the engine. If you run a iron block, you can use the factory motor mounts, and tubes back to a tab welded to the chassis. Don

 

Automatic cars have to have them to, my altered uses a solid trans mount on the tailhousing of the powerglide case. I have seen some flexplates let go, and it wasn't pretty, why else would auto trans cars have to have a flexplate shield, I got a JW ultrabell in my altered.

 

NHRA lists rules pertaining too "flywheel" and "flexplate" seperate.

But you certainly will need some type of travel limiter to hold the engine in place.

Blessings.........Ron Clevenger.

 

Material required is 4130 chrome moly (or Reynolds 531), minimum size is .875-inch (22.2 mm) O.D. x .083-inch (2.1 mm) wall tubing with 3/8-inch (9.53 mm) fasteners. Ball-lock pins prohibited.

Is that out of a current rule book?

I have not heard of Reynolds 531 tubing since I was racing road bikes 30 years ago ( the ones with pedals ) does it need to be double butted or can I use straight wall, and should I use lugs to braze the tubes to the frame thats really scary Reynolds is very strong but very brittle (it used to snap when overstressed in a road bike frame) I doubt it is normalized tubing.


Richard Gavle

 

I have blow back tubes on my Lencodrive. They mount to the studs holding the bellhousing and run to brackets on the top frame rail.

 

Richard,

You are absolutely correct. When I pulled up this rule on Google so that I could "copy and paste" in my reply, The one I pulled up had the added description of the reynolds 531 tubing. The rest of the description was correct with the 2009 rule book.
My bad!

 

Ok, Ok!

I am truly not being a smart ass, every one here has been a huge help to me as a newcomer over the last year! I truly don't know about this and that is why I asked the initial question. Is the Anti-blowback device to be built to limit the "engine" travel, or is it to limit the "transmission" travel, or should I be asking, "what the hell am I trying to accomplish here to satisfy this rule!

Does everyone, or should I say "anyone" on this site have one of these? Post a picture and I can take it from there. If this is "secret squirrel shit", just say so and I will figure out what to do from there!

 

dave I have auto and u gotta have them! Very simple to do and all hardware about 100$. I can give you a pic of how simple, just how do I post them though?

 

Dave, what your trying to accomplish is over come the G forces of the launch. The car moves forward but the weight of the engine/transmission wants to move rearward. We are talking 3 to 4 G's of force, more on nitro cars.
That's why you need to tie that engine/transmission into the car to keep it from smashing everything behind it.
Trust me..it's violent and then when you get tire shake along with it strange things happen.

Make them strong.

Blessings...........Ron Clevenger.

 

Dave, here's a picture of mine connected to the back of the PG bell housing.



Hope this helps.

 

Ok!!!!!!!!!!!!!!!

So it will limit movement if clutch, flywheel or in my case the flexplate should explode (which satisfies the rule). Also supports (assists) engine plates on launch!

Thanks everyone for their patience, ......... my signature says it all