Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

[FTG-05]

I built a steel target stand over the weekend for our family Memorial Day BBQ and cookout. The basic targets are steel plates, 6" round, 1/4" thick (cutouts from a wood stove place). I welded the bases to 1" tubing, 1/8" thick i.e. 3/4" inside dimension for a tube or rod or pipe. I made a stand out of 1/2" rebar and more of the 1" tube and that part works OK.

What doesn't work is the 1/2" that goes through the stand legs and then holds the five 6" target plates. The 1/2" rebar sags in the middle, not allowing the plates to freely move when hit with a bullet- minimizing the whole purpose of using steel targets in the first place: instant feedback on a hit.

I used 1/2" rebar since I didn't have any 5/8" or 3/4" rebar or rod (at least long enough to use) and I didn't have any 1/2 black iron pipe on hand. I'll be going to Lowe's tomorrow, so I want to pick up the best thing for the purpose at hand.

So, everything else being equal: which will bend or sag less, 3/4" rebar or 3/8" black iron pipe?

Thanks,

 

[4570Man]

Did you mean 3/4 black pipe? 3/4 rebar will be stronger than 3/8 pipe.

 

[FTG-05]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

Did you mean 3/4 black pipe? 3/4 rebar will be stronger than 3/8 pipe.

Whatever I use has to be less than 3/4" in diameter. 1/2" black iron pipe is 0.84" OD so that won't work. 3/4" rebar may be even to tight. I may have to redo the 1" square tubing

 

[SPYDERLK]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

Stiffness is a cube function. Twice the dia will be 8 times as stiff.

 

[RedNeckRacin]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

Look up the moment of inertia for the shapes . Bigger number means a stiffer member.

 

[chim]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

My first thought is that rounds that are powerful enough to make a 6" diameter plate spin are probably going to do damage to the supporting pieces unless they're heavier. I wouldn't have a lot of faith in small diameter pipe.

We have some mechanical (turning) targets at our range and it was necessary to have angle iron in front of the rods to shed stray bullets. This range is even limited to non-jacketed bullets.

 

[FTG-05]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

My first thought is that rounds that are powerful enough to make a 6" diameter plate spin are probably going to do damage to the supporting pieces unless they're heavier. I wouldn't have a lot of faith in small diameter pipe.

We have some mechanical (turning) targets at our range and it was necessary to have angle iron in front of the rods to shed stray bullets. This range is even limited to non-jacketed bullets.

Here are some pics of the plates and it's current structure. I was surprised with the timing when designing and building these, I thought I had one more day but our guests decided to come earlier. Since it was a Sunday over a 3 day holiday, I was limited to what I had on hand, which in this case, was 1" sq. tubing and 1/2" rebar.

Since the plates are only 1/4" thick, I'm limiting them to .22LR only. I don't need the plates to spin per se, but at least move a little and make a "clank" noise when hit. Right now, due to the bending of the 1/2" rebar, they are binding up against each other and not moving easily. I'll probably add angle to the front of the plates where they attach to the the 1" sq tubing.

Thanks!

 

[Sodo]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

Hang each plate on two short chain sections (of 2 or 3 links) to the pipe sections. Plates hanging on chain links will probably ring better. Toss it onto a cement floor, see what rings the loudest. I think that heavy angle etc damps the ringing cut it all off so the plate is just a disc with chain links welded onto it.



And move your sight to the left a little

 

[RobertC]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

Try putting a couple of washers between the targets. That should reduce the binding and it's quick and cheap to try.

 

[SPIKER]

Re: Which will bend less or be more rigid: 3/4" rebar or 3/8" black iron pipe?

I made one a while back using 3/8" rebar and 1/2"pipe which works WELL. 22 will spin most of the 2" dia one and the 4" will set it well back and swing it if hit 2 times while moving backwards on 2nd hit.

Thread in in either projects or build it yourself.

seeing your pics the sq tube will catch on the plate next to it, slip some flat washers on big enough to act as a bearing surface between the two plates.

be sure when welding these on that the plate is angled to deflect round down and to rear.

here are a couple pics of mine made with 1/4 to 1/2" plates rebar and pipe with 1/2" pipe w rebar welded to pipe on front side so target leans back deflecting rounds down and as spins away.






now has better backstop as well pics are older 1 or 2 years on this now.


Mark