How much torque would a crowfoot torque if a crowfoot could wrench torque?
February 28, 2012 6:56 AM Subscribe
If I have a click-type torque wrench (the sort that has a clutch so it clicks over when I get to the requisite torque) connected up to a straight socket, I can set the wrench for the desired level of torque and that's what gets delivered to the bolt when the clutch clicks over. What if I've got my torque wrench connected up to an offset crowfoot socket that's on my bolt? The offset presumably creates some leverage, so I'm delivering a slightly different torque force to the actual bolt than with a straight socket. How can I calculate this difference and figure out what the actual torque is on the bolt?
A lot of web pages out there claim that the length of the torque wrench handle matters, but I can't see how that can matter if I've got a click-type torque wrench, since the clutch will do it's thing and click over at the specified torque level whether I'm holding the wrench next to the head or I'm using a 3' long cheater bar on it to give myself more leverage. I assume that the distance from the socket connection to the center of the bolt matters, though.
A lot of web pages out there claim that the length of the torque wrench handle matters, but I can't see how that can matter if I've got a click-type torque wrench, since the clutch will do it's thing and click over at the specified torque level whether I'm holding the wrench next to the head or I'm using a 3' long cheater bar on it to give myself more leverage. I assume that the distance from the socket connection to the center of the bolt matters, though.
Neat question, but I can't answer it. It seems likely that the position of the offset socket relative to the torque wrench handle might have a significant impact on the torque delivered to the bolt.
posted by jon1270 at 7:33 AM on February 28, 2012
posted by jon1270 at 7:33 AM on February 28, 2012
You're correct. Adding a cheater pipe, for instance, to the handle of the torque wrench will not affect the torque applied, a crowfoot socket that extends the center of the wrench's drive axis from the center of fastener absolutely will.
There are a ton of calculators online that will calculate this quickly, here is one. You could also probably find an app for your mobile device that will do it also.
posted by Capa at 7:41 AM on February 28, 2012 [2 favorites]
There are a ton of calculators online that will calculate this quickly, here is one. You could also probably find an app for your mobile device that will do it also.
posted by Capa at 7:41 AM on February 28, 2012 [2 favorites]
web pages out there claim that the length of the torque wrench handle matters, but I can't see how that can matter if I've got a click-type torque wrench, since the clutch will do it's thing and click over at the specified torque level whether I'm holding the wrench next to the head or I'm using a 3' long cheater bar
I think the effective length of the handle starts to matter when you have an offset (crows-foot type) extension (not a "regular" vertical socket extension). In other words, when using an offset extension, the wrench will click over at different torques if you grab the handle in different spots. The explanation here makes sense to me.
posted by exogenous at 7:49 AM on February 28, 2012
I think the effective length of the handle starts to matter when you have an offset (crows-foot type) extension (not a "regular" vertical socket extension). In other words, when using an offset extension, the wrench will click over at different torques if you grab the handle in different spots. The explanation here makes sense to me.
posted by exogenous at 7:49 AM on February 28, 2012
What are you trying to torque? I really don't worry about the difference in torque unless it is some sensitive application, such as cylinder head bolts. A lot of the time you can't even use a torque wrench because the head of the wrench is big, and won't fit where you need it.
posted by narcoleptic at 10:18 AM on February 28, 2012
posted by narcoleptic at 10:18 AM on February 28, 2012
Focus on the 90deg case in the ADVrider link, it is nice and simple.
http://www.motofab.com/images/repair/tools/torque/torque_90deg_offset.png
You want your extension at 90deg to your torque wrench. See the end of this page of note about torque wrenches for what this looks like. If you set the extension at 90 deg, the extension applies the same torque as the wrench. This is what you want to remember when working in the shop.
With an extension, angle and wrench length matter if you are not using 90deg and then you have to use a formula. Here is a place with the formula: http://www.trialsnuts.com/TORQUED.pdf
The clutch and settings on your wrench are calibrated for the length between the center of the ratchet shank and the pivot of the clutch. If you change that length some how your settings are no longer correct. If you have your extension at a non-90 deg angle, that length changes. If you have your extension at 90deg, that length doesn't change.
I like to use a torque wrench on anything that is important. (suspension, engine, frame, brakes)
posted by bdc34 at 10:49 AM on February 28, 2012
http://www.motofab.com/images/repair/tools/torque/torque_90deg_offset.png
You want your extension at 90deg to your torque wrench. See the end of this page of note about torque wrenches for what this looks like. If you set the extension at 90 deg, the extension applies the same torque as the wrench. This is what you want to remember when working in the shop.
With an extension, angle and wrench length matter if you are not using 90deg and then you have to use a formula. Here is a place with the formula: http://www.trialsnuts.com/TORQUED.pdf
The clutch and settings on your wrench are calibrated for the length between the center of the ratchet shank and the pivot of the clutch. If you change that length some how your settings are no longer correct. If you have your extension at a non-90 deg angle, that length changes. If you have your extension at 90deg, that length doesn't change.
I like to use a torque wrench on anything that is important. (suspension, engine, frame, brakes)
posted by bdc34 at 10:49 AM on February 28, 2012
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posted by spikeleemajortomdickandharryconnickjrmints at 7:28 AM on February 28, 2012