Need help with a torque related math question

[6500rpm 670]

I made the pictured tool to torque a Seekins Precission barrel nut for a AR. The center of the barrel pass through hole to the center of the square drive for the torque wrench is 2". If I have a torque value of 30ft/lbs on the wrench, how do I figure the actual torque value with the additional 2" the tool adds?  It's an odd deal, Seekins doesn't give a torque value, they have four groups of three holes (center hole aligns with center on upper receiver). They state to hand tighten to the first hole using shims, and then tool tighten to center hole. In doing that I net 30ft/lbs +/- on my torque wrench which seems a bit light to me but I'm weak on AR's.

 

[james lambert 3,059]

I have seen manuals state 28 to 80 ft# That allows alignment  of gas tubes regardless,   and 80 will twist the forging to shit if not properly viced in a VERY good fixture

 

I torque AR barrel nuts to 60# but those are my barrel nuts and are independent of gas tubes.

dont know diddle about seekins stuff

[Heartbreaker 1,085]

Why you bothering with all that crap? All ya need is a breaker bar and 3 foot of pipe. Clicky wrenches are for fancy chumps.

 

(Just kidding )

 

 

By the way, it's pretty much the same with Midwest Industries handguards/barrel nuts. They come with an adapter like yours to tighten the nut. Nothing about the extra length affecting read-out. I tightened to around 30 ft#, about where I didn't think it would rotate to the next hole.

Edited December 30, 2015 by Heartbreaker

[storm6490 2,768]

Calibrate with another torque wrench centered.

[james lambert 3,059]

add about 16 percent to the reading

[Sim_Player 1,939]

The length of the wrench and angle affects your torque result.

 

I'm sure Google would "shower" you with info.

[Boba Debt 350]

If you position the centerline of the wrench 90 degrees off the centerline of the tool the torque will effectively be the same.

 

This applies to crows feet, dog bones, spline extensions, etc.

[vulcan16 971]

The length of the wrench and angle affects your torque result.

I'm sure Google would "shower" you with info.

The length of the torque wrench doesn't affect the torque.

Angle does but not length. We have to torque Boeing 757 main landing gear trunnions to 600++ foot lbs. One guy can do it if another person holds the socket on the nut using a 7 foot long torque wrench.

Edited December 30, 2015 by Jet

[Boba Debt 350]

The length of a torque wrench does not affect the tool if a socket is used because the center point of the torque application is still in line with the center of the socket.

 

If you move that center line away from the original point it does affect torque. Example, if you put a crows foot on a torque wrench and if it is in line with the tool the value will be different.

 

UNLESS you attach the tool at 90 degrees as I already posted, while we are dropping names so to speak I have worked on 6 different Marine Corps aircraft since 1992 and that is the practiced recommended by all aerospace engineers.

 

BTW - I'm a buck80 and I can pull 425 foot pounds on CH-53 Tail Rotor Blades all day long

Edited December 30, 2015 by Boba Debt

[6500rpm 670]

I've seen that some place Boba but I couldn't wrap my head around the fact that by simply rotating the device 90 degrees in effect keeps the torque value correct. That and the fact that my clicky wrench is the $500 Snap On flavor (it beeps, it shakes, reads standard/metric torque and angle) I just wasn't sure if the damn electronics in it didn't effect the way it calculates. Should have mentioned it's on a 9mm blow back so there's no gas tube to index, but it needs to hit the center hole of the three to allow the HG to slip over and bolt in place. To increase the torque, I'd need to add more shims and crank it to the next 1/4 turn.

[Boba Debt 350]

Bing "torque wrench crowfoot 90 degrees" and you will get tons of simple and complicated explanations of why this works.

[Sim_Player 1,939]

What does the length help?

 

I always saw that as torque.

[mancat 2,368]

The overall length of the attached fixture does skew the measured torque value, and there are plenty of online calculators to determine the offset.

 

http://www.cncexpo.com/TorqueAdapter.aspx

[BigChongus 765]

This is pretty simple vector mechanics. Moment about an axis = F*r. Any distance added between the axis of the nut and the portion of the handle you're pulling on will lower the torque value you need to set the wrench to. 

[HB of CJ 1,263]

Remove that handle and replace with a good precise click torque wrench.  The barrel extension goes on at about 80 ft pounds.  The pesky OEM barrel nut goes on DRY at around 40 to 42 pounds.  The barrel gets locked down very tight with alloy vice jaws and carpet padding.  The upper floats free.  Any other way is dead wrong with the danger of cracking the upper.

 

Getting this torque value with the gas tube exactly floating with no contact around the OEM barrel nut and carrier key is a copper plated bitch.  You probably will have to slightly surface the end of the upper on a precise surfacing machine.  The receiver end must be at right angles to the bolt carrier and barrel line.  Have fun!  HB.  Hundreds of AR15 builds.  But who cares. 

[XD45 7,124]

If you position the centerline of the wrench 90 degrees off the centerline of the tool the torque will effectively be the same.

 

Exactly what I was going to say.

[6500rpm 670]

This may be an just an exercise for a bit, when the stamps clear it's getting swapped for a short barrel and suppressor which is why I went with the Seekins HG.  Upper is a dedicated 9mm from CMMG with whatever 16" barrel they used at the time.Regardless, for now I can get it up and shooting until the time comes but the 30ft/lbs using the Seekins method seems light.

 

[sccritterkiller 473]

That and the fact that my clicky wrench is the $500 Snap On flavor (it beeps, it shakes, reads standard/metric torque and angle) I just wasn't sure if the damn electronics in it didn't effect the way it calculates.

Some buddies and I got unto this conversation the other day..doesn't anybody still use the old school needle torque wrenches anymore?..I have a needle one that is probably 40 years old and use it way more than my 3 newer clicky ones..still works great! Seems like now a days these new ones will do everthing but jerky you off...I don't like spending 20 min to set up the wrench for 2 bolts...lol

Edited December 30, 2015 by sccritterkiller

[G O B 3,516]

Needle type torque wrenches loose their calibration after only a few hundred uses. It is basically just a spring with a pointer, and just like old truck springs, they loose ridgidity over time, The closer to the max on the readout you use it  the faster they loose calibration.

 

On Fairbanks Morse 303's the rods torque to 1,750FP, and the mains 2,250FP! - we used chain falls to pull them, and a dial type torque wrench that had  a ring on the end of the handle for that!

 

When you put a torque wrench on a fixture or crows foot, the wrench MUST be 90* to the fixture.  That way the length of the lever turning the work is the same as the length of the wrench.(as long as the fixture or tool has no appreciable flex).

When you MUST use the torque wrench in line with the fixture or tool, then you are measuring the torque applied to the tool or fixture at the distance of the centers between the tool and the work. A 2" fixture would be 1/6 of the 'foot' in the foot pounds ( FP) the torque wrench is calibrated for, so you would reduce the torque by 1/6 .

So- to get 30 FP with a fixture of 2" center to center you would get -  1/6X30=5   30-5= 25.(as long as the fixture is ridgid enough to ignore any flex).

For inch pounds or Newton Meters, just use the center to center measurement in the proper scale for that torque wrench.

[6500rpm 670]

sccritterkiller, about the only thing I use the old style beam torque wrench for anymore is an inch lb for checking rotational preloads. I could have shit when I purchased the new style that I have now but I work on new vehicles/fleet and with all the aluminum engine components they've gone to a Torque-to-Yield one time use bolt system that uses thread stretch. Torque specs are something like this-torque in order all or some to 20ft/lbs, followed by another pass at 46 degrees of rotation, followed by a final pass at 60 degrees of rotation. This particular wrench does in/lbs, ft/lbs, Nm, and degrees of rotation. It also remembers how many degrees you turn so if you set it for 42 degrees and can only go 30 degrees due to a tight spot, it remembers you've gone 30 and allows you to ratchet it back and when you pull the final 12 degrees required it has a digital read out, beeps and shakes. Pretty cool stuff but tools are a big investment.

 

Thanks for everyone's input, I'm going to call Seekins and see if I can get a response from them on what they consider torqued and I'll try to edit in their instruction sheet because it really is a trip.

[vulcan16 971]

What does the length help?

 

I always saw that as torque.

Leverage only.

 

Ever try to remove a lug nut with your cars factory lug wrench verses a four way lug wrench?

Same thing.

If you move that center line away from the original point it does affect torque. Example, if you put a crows foot on a torque wrench and if it is in line with the tool the value will be different.

 

UNLESS you attach the tool at 90 degrees as I already posted, while we are dropping names so to speak I have worked on 6 different Marine Corps aircraft since 1992 and that is the practiced recommended by all aerospace engineers.

 

BTW - I'm a buck80 and I can pull 425 foot pounds on CH-53 Tail Rotor Blades all day long

Only since 1992......hell...you would still be on the grave yard shift at any major airline

Edited December 30, 2015 by Jet

[Boba Debt 350]

 

What does the length help?

 

I always saw that as torque.

Leverage only.

 

Ever try to remove a lug nut with your cars factory lug wrench verses a four way lug wrench?

Same thing.

If you move that center line away from the original point it does affect torque. Example, if you put a crows foot on a torque wrench and if it is in line with the tool the value will be different.

 

UNLESS you attach the tool at 90 degrees as I already posted, while we are dropping names so to speak I have worked on 6 different Marine Corps aircraft since 1992 and that is the practiced recommended by all aerospace engineers.

 

BTW - I'm a buck80 and I can pull 425 foot pounds on CH-53 Tail Rotor Blades all day long

Only since 1992......hell...you would still be on the grave yard shift at any major airline

 

 

Plus I would be making less money and be in constant fear of getting laid off and I am sure I wouldn't get 208 hours of vacation plus 104 hours of sick leave every year.

 

 

Fed jobs have their perks

 

 

BTW - I'm a night hawk and only work 1st shift if I have to

 

 

PS - I'm 48,  so if you have been working on planes longer them me it just means your that much closer to death so I wouldn't be all braggy about it.

[Hawk451 2,230]

Second shift was always my favorite.

 

In answer to the OP, I've pretty much always used the 90 degree method.

 

We had 3 guys who could torque the prop nut on an F-27 (God, I'm dating myself), 'bout 1000-1050 '# IIRC, solo. One was nicknamed 'Mongo'. 1" drive TQ wrench about 6' long with no torque multiplier. I tried, could barely pull 750...

Edited December 31, 2015 by Hawk451

[Capt Nemo 882]

I could make 600lbs before my boots would slip.  Jesus nuts were 375 on the OH-58 if I remember correctly.

[Hawk451 2,230]

Everyone I wrenched with that worked rotor-wing previously were good to damn good mechanics. 

[sccritterkiller 473]

Very familiar with torque to yield. Been stacking steel for 15 years.We pre-tention with the turn of the nut method then set final torque...Anybody can torque a bolt when you feet are on the ground...Try to set torque on a 3/4" a490 hanging in a harness from 300'...it only needs 435 ft lbs...lol

Edited December 31, 2015 by sccritterkiller

[vulcan16 971]

 

 

 

.

 

Ever try to remove a lug nut with your cars factory lug wrench verses a four way lug wrench?

Same thing.

 

 

 

Plus I would be making less money and be in constant fear of getting laid off and I am sure I wouldn't get 208 hours of vacation plus 104 hours of sick leave every year.

 

 

Fed jobs have their perks

 

 

BTW - I'm a night hawk and only work 1st shift if I have to

 

 

PS - I'm 48,  so if you have been working on planes longer them me it just means your that much closer to death so I wouldn't be all braggy about it.

 

  You never know how close to death you are....regardless of age

  I currently get 240 hrs of vacation (+ 40 more in 2017) 4 floating holidays.....8 hours sick leave per month.....12 hours per month once your sick bank dips below 240 hrs.... can accumulate up to 1700 hours.....+700 hours of fully paid OJI time...and we fly for  FREE.....FIRST Class Included   

  We also do almost unlimited one way trades with fellow coworkers. Don't feel like coming in because your 401K is making tons of money, or you want to extend your vacation because you're  traveling  the world.......give the days away(straight time) to someone on a different shift.  A couple of guys haven't shown up in weeks without burning vacation.....they have called in someone else to work for them.

 

  And with your 92 seniority.....lay offs ain't going to happen. Hell...Hillary will cut the defense budget if elected and might close down your base (Kelly AFB & other base closures come to mind.) 

 

  The family spent the days after Thanksgiving in Hawaii...flew first class(step daughter got stuck in coach)....going back in a couple of weeks(surf trip).  If FC isn't  available...Costa Rica or Mexico are the next 2 choices.    Spending New Years weekend in San Diego or Vegas(coach more then likely .)

 

  BTW we will be in your neck of the woods late January (NC).

 

  And you have no idea how much the topped out airline mechanic makes. We are currently offered $46.12 per hr and told the company to shove it up their ass.    

  Civil service workers make old time union members look productive. ( military veteran-raised in a military city- 5 bases / 2 base annexes.) I know how the civil servant section doesn't work.

 

  Do you even have an A&P license?

  Keep your head down so that damn fling wing doesn't whack it off.

Edited January 1, 2016 by Jet

[Dad2142Dad 6,559]

No wonder flying is so expensive

[G O B 3,516]

I used to LOVE torque to yield!  As a father of 5 I had a LOT of cars to put on the road for my kids when they were teenagers. Chrysler K cars had the nifty 2.2L engine with those 10 MM torque to yield head bolts. People would drive the with a bad belt or a leaky water pump, and warp the heads at the #1 cylinder. You could get one for about $200. I would use a big assed mill file to flatten the head, and tap the block to 11MM and use the bolts for a turbo engine that I could torque to 90FP.  My oldest daughter ran one up to 230,000 miles!

[6500rpm 670]

Good to see you guys work with your hands too, having a skilled trade is a good thing and I've always enjoyed it. Here's a picture of the most dumb ass barrel nut design I've seen- my thought was just to torque it down to good AR barrel nut spec, slide the handguard on and just drill and tap new mounting holes. In their infinite wisdom, even though it can only index off four center holes as designed, they drilled the other 8 useless holes all the way through the nut limiting sweet spots to hit.