Figuring torque using an offset

NCWayne · Aug 24, 2014

I know I can probably Google it and visit a dozen sites to get an answer to this, but I'm hoping that someone here has a good site to try, or an actual answer to my question.

Here goes. I've got to replace the head gaskets on an old D9G. Four of the fasteners have obstructions over the top that prevents getting a torque wrench directly on them. The problem is to get rid of the obstructions would take a good bit more time, and disassembly of the engine than I really want to get into, not to mention the added cost to the customer.

To that end I made an offset tool with a socket on one end for the fastener, and then a square drive hole on the other for the torque wrench.

So what I need to know now is this. How do I determine the torque reading I need to set the torque wrench at when I've got an additional 1 3/4 inch long 'lever' off of the center line of the torque wrench drive? I know it will have to be a percentage lower than the spec in the book, but how do I calculate that percentage?

Any links to the info, or the info itself would be greatly appreciated.

Anonymous-0 · Aug 24, 2014

Seems to me the easy solution would be to couple it to another dial type torque wrench and observe the reading and adjust accordingly.Should work.

JMS/.MN · Aug 24, 2014

If you"re reading in ft lbs....1.75 is what percentage of 12....? I think that"s the idea.

Allan in NE · Aug 24, 2014

Just tighten the goofy things down. The torque cops won't come get ya.

Allan

bison · Aug 24, 2014

I had the same problem with head bolts on an engine once.

i welded 2 sockets together side by side to get the offset of about 1" i needed.
Torque values are usually given in min to max.i used the middle # between max and min values from the manual
I would use the min value and torque all the bolts with your slightly longer adapter.
That should come close enough me thinks

Bob · Aug 24, 2014

.
A calculator I have used

Ron Muhlenkamp · Aug 24, 2014

Feet (or inches) times pounds of force equal foot-lbs. ( or inch pounds) A longer lever needs proportionately less force. I once rebuilt an engine using a nine inch ratchet and a bathroom scale.

Jason S. · Aug 24, 2014

(quoted from post at 00:47:39 08/25/14) I know I can probably Google it and visit a dozen sites to get an answer to this, but I'm hoping that someone here has a good site to try, or an actual answer to my question.

Here goes. I've got to replace the head gaskets on an old D9G. Four of the fasteners have obstructions over the top that prevents getting a torque wrench directly on them. The problem is to get rid of the obstructions would take a good bit more time, and disassembly of the engine than I really want to get into, not to mention the added cost to the customer.

To that end I made an offset tool with a socket on one end for the fastener, and then a square drive hole on the other for the torque wrench.

So what I need to know now is this. How do I determine the torque reading I need to set the torque wrench at when I've got an additional 1 3/4 inch long 'lever' off of the center line of the torque wrench drive? I know it will have to be a percentage lower than the spec in the book, but how do I calculate that percentage?

Any links to the info, or the info itself would be greatly appreciated.

I had that same problem and I looked into it and I found several articles that say to turn the extension your using to a 90 degree from the torque wrench that way it doesn't add to the length of the torque wrench.

NCWayne · Aug 24, 2014

As far as it is into this thing just to get the two heads off, and given that three of the four are on one head, I need to be at least close when I get done.

Being a mechanic by trade, I am going to do it right, or not at all. That's mainly a matter of pride in my work, but also due to the fact that if I don't do it right, it falls on me to do it again on my own dime. When your talking a few hundred dollars in parts, several hundred more in fuel, and a few hundred more in expenses because the machine is over two hours away from home, it makes insuring that the job is done right even more important than it already is.

Not to mention that when your talking a fastener that tightens to somewhere around 350 ft lbs already, too much more could easily be enough to strip threads, or twist off the fastener. That takes me right back to square one with then having to foot the bill for parts, etc messed up because of something I did wrong.

I like to turn a profit on my jobs, so no thanks to the idea, I think I will do it right.

Sean Feeney · Aug 24, 2014

Use that set up your going to use on a bolt that not obstructed and get your readings to use on them.

JD Seller · Aug 24, 2014

NC Wayne: It is just a ratio problem. You need to know the length of the original torque wrench. This is usually measured from the center of the square drive to the middle of the handle you pull on.

So Lets say that is 10 inches.

So using your adaptor the length would be 10+1.5= 11.5

You need to know what percentage the old lever/torque wrench is compared to the "new" length of the combined tool.

So divide 10 by 11.5 = 87%

So the original wrench is 87% as long as the combined wrench.

If you wanted a final torque of 350 foot lbs. you would set the wrench at 87% of that or 304.5 foot lbs.

The only caution is only use the extension/crows foot straight out the end. This makes it a straight level problem. If you go to angles it gets to be a very complicated math problem to figure the actual torque.

NCWayne · Aug 24, 2014

I hadn"t thought about that, but it sounds reasonable. Still I don"t know if I"ll have room to swing a 3/4 drive torque wrench and insure that I remain at 90 degrees, and get to where I can stand and pull close to 350 ft lbs all at the same time.

jimg.allentown · Aug 24, 2014

As far as I know, the only engines that would require that kind of torque would be ship's engines or locomotive engines - or perhaps a Waukeshaw that was set up to provide power for a whole community. 350 ft-lbs is a very lot of torque. Any fasteners that require that much torque are not likely to break if the torque is off by 10%.
However, I would suggest that you use the adapter with a breaker bar, and use the length of the moment arm (in feet) times the force applied (in pounds) to reach the desired torque. Using a pull scale, it would be as accurate as a torque wrench that has not recently been calibrated. Using the same tooling on every head bolt would result in the torque being evenly applied.
I have been rebuilding engines and transmissions for over 40 years, and while torque is important, it is more important that it be evenly applied and in the proper pattern.
I'm sure that there is a formula for figuring the use of an offset, but how to figure it escapes me. Using a pull scale is actually more accurate than the average breakaway torque wrench anyways.

JD Seller · Aug 24, 2014

NCwayne and Jason: Those articles are WRONG!!!! Even at a 90 degree angle the force is higher because of the length of the additional lever/adaptor/crows foot. The additional force is greatly reduced but it is still greater.

The reason is that the force is being applied of center. So it makes it a very complicated geometry problem verse a straight lever/ratio.

moresmoke · Aug 24, 2014

At 90 deg the torque will be 1.0007 times the wrench, close enough to the same for me. This is with a 48" wrench.

Indiana Ken · Aug 24, 2014

The link Bob posted is correct. If the adaptor is at a 90 degree angle the length of the torque wrench does not change and the reading on the wrench is the actual torque applied. If the adaptor is at an angle, use the change in length as measured parallel to the beam of the torque wrench. For example: with the adaptor at 45 degrees the change in length would = Sin 45 degrees (.707) x 1.5 = 1.06. Therefore, you use 1.06 as the lenght of the adaptor.

Respectfully, Ken

Jason S. · Aug 24, 2014

I'm not gonna get in the middle of an argument on here,all I know is using it at a 90 degree to the torque wrench worked for me torquing a head and it has held up for three years now. I read that and it made sense to me so that's what I went with.

JD Seller · Aug 24, 2014

Jason for everyday usage your correct in that the difference would normally not make much difference. It is a higher torque at 90 degrees. It is very little more but it is more.

BarryfromIA · Aug 24, 2014

We used 90 degrees on offsets at a hydraulic factory I worked at per one of the engineers. Some of the center rods had wires from sensors in the end.

Dick L · Aug 25, 2014

In 1949 a neighbor was doing auto repair in his garage as a side along with farming and hauling milk. When I was putting the head back on my Chevy I thought I needed a tourqe wrench and ask Dad if he would buy one. He sent me to the neighbor to see if he would loan me his. The neighbor took me out to his garage and showed me an old ratchet and a pair of channel locks. He said that those had always been his torque wrench. When he had all the head bolts drawn down as tight as he could with the ratchet by hand he would pull on the ratchet with the channel locks until they lost its grip and slipped off. Said he had never lost a head gasket in all his years of auto repair.
From that I got the idea that exact torque readings was not that important except in rare cases. Of course the auto and tractor engines of the time were lower compression engines.
Drop your rocks folks as this is just a memory about torque wrenches from an old mans past Not Advise.

dr sportster · Aug 25, 2014

I know how to do it but I always wondered if the spec for the length of wrench from center of socket drive to center of handle was for before or after the calculation. Once you do the math the handle always gets adjusted shorter. So is it the shorter readjusted number or the original before adapter number.It doesn't throw you off by much but it does change it .

Bspauld · Aug 25, 2014

Thats what I was thinking, or torque one down and check it with the adapter to see what it was

Ozlander · Aug 25, 2014

(quoted from post at 18:30:22 08/24/14) At 90 deg the torque will be 1.0007 times the wrench, close enough to the same for me. This is with a 48" wrench.

And if you have a 48" wrench and you add 1.75" to it you have a 49.75" wrench. Not enough to worry about, just pull to 338 and you be good.

Figuring torque using an offset

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Well-known Member

Member

Well-known Member

Similar threads