Snapped u-bolt

Colthebrummie said:

Sorry, it wasn't meant as a trick question. It would seem to me that there are two types of mechanic, those like me that learnt spannering skills donkey's years ago that feel able to tighten a nut or bolt by feel and those that follow guidance in manuals to the enth degree. I haven't got a problem with using torque wrenches, I own a few but I couldn't swear they are accurate. I wonder how many of us trust torque wrenches that are several years old that have never been recalibrate or even wound back to zero after each use. On the rare occasion when I have used a torque wrench, I've often felt that whatever I was doing up was either too tight or not tight enough. I would like to mention that in almost 50 years of doing stuff up, I've never had anything come loose, unlike several so called skilled garage mechanics. I have had the odd bolt snap but that was more the fault of a crappy bolt than my ham fistedness.

Col

Click to expand...

Col,

I completely agree with you when you say there is nothing like experience. People who have been doing it for a long time (on the whole) have a much much better idea of how things feel "right" or not.

The torque wrench calibration situation is indeed a potential problem. Torque wrenches need to be looked after and treated with care (which is why I wouldn't be using them for general spannering - hence my reference to the trick question).

In addition to the calibration issue there is also a user issue. As an aircraft mechanic the procedure of checking the set torque on a wrench with a (very expensive) calibration tester was often part of my daily routine. It is surprisingly easy to make things too tight with user error...

...even though there is an element of user error and calibration error when using a torque wrench I would certainly encourage people to use them.

The extra bit of attention - the awareness of what you are doing and the importance of what you are doing - has to be worth the extra effort.

#####

I wouldn't be at all surprised if many professional garages have torque wrenches that are not calibrated. I wouldn't be surprised if a lot of professional mechanics don't use them. But hey - what can ya do?

One thing I have seen on some of those "traffic cop" programs on the telly is rozzer crash investigation teams checking simple things like the torque of wheel bolts. If "they" are able to show that things have not been done correctly there is an element of trouble ahead. Some people have a problem with DIY mechanics - there was a campaign for the right to repair a few years back in the UK to counteract this...

...so the main message from me is to respect the parts that need extra attention like brakes, steering and suspension

#####

If any one here is reading this and wants to check the comparable performance of their torque wrench (making a comparable calibration is often done in industry though not usually in the way described =>) a spring balance and a T-bar on a socket can be used to calculate the applied torque => Torque = Force (convert kg to Newtons!) multiplied by the distance of applied force.

So torque a bolt with your torque wrench and then mess about with your T bar and spring balance.

I am sure this method - when done carefully - will get you very close to the performance of a gucci "NASA calibrated" tester

(Calibration of the spring balance can be done by measuring with a known weight - water is actually quite useful for this - or bags of sugar etc)

Stretch said:

Col,

I completely agree with you when you say there is nothing like experience. People who have been doing it for a long time (on the whole) have a much much better idea of how things feel "right" or not.

The torque wrench calibration situation is indeed a potential problem. Torque wrenches need to be looked after and treated with care (which is why I wouldn't be using them for general spannering - hence my reference to the trick question).

In addition to the calibration issue there is also a user issue. As an aircraft mechanic the procedure of checking the set torque on a wrench with a (very expensive) calibration tester was often part of my daily routine. It is surprisingly easy to make things too tight with user error...

...even though there is an element of user error and calibration error when using a torque wrench I would certainly encourage people to use them.

The extra bit of attention - the awareness of what you are doing and the importance of what you are doing - has to be worth the extra effort.

#####

I wouldn't be at all surprised if many professional garages have torque wrenches that are not calibrated. I wouldn't be surprised if a lot of professional mechanics don't use them. But hey - what can ya do?

One thing I have seen on some of those "traffic cop" programs on the telly is rozzer crash investigation teams checking simple things like the torque of wheel bolts. If "they" are able to show that things have not been done correctly there is an element of trouble ahead. Some people have a problem with DIY mechanics - there was a campaign for the right to repair a few years back in the UK to counteract this...

...so the main message from me is to respect the parts that need extra attention like brakes, steering and suspension

#####

If any one here is reading this and wants to check the comparable performance of their torque wrench (making a comparable calibration is often done in industry though not usually in the way described =>) a spring balance and a T-bar on a socket can be used to calculate the applied torque => Torque = Force (convert kg to Newtons!) multiplied by the distance of applied force.

So torque a bolt with your torque wrench and then mess about with your T bar and spring balance.

I am sure this method - when done carefully - will get you very close to the performance of a gucci "NASA calibrated" tester

Click to expand...

Ah, but has the spring balance been calibrated.

Col

Colthebrummie said:

Ah, but has the spring balance been calibrated.

Col

Click to expand...

Sorry I must have made the edit whilst you were replying - see above

(I'm a pain in the arse eh?)

Stretch said:

Oh dear - some of you scare me!

There are certain parts of the vehicle - in particular U-bolts - imagine them coming off at any speed - that deserve a bit of respect

"Counting white knuckles" isn't always appropriate!

Click to expand...

Never let a plant fitter work on trucks
Never let a truck fitter work on cars
Never let any of the above near an aircraft!

lynall said:

Never let a plant fitter work on trucks
Never let a truck fitter work on cars
Never let any of the above near an aircraft!

Click to expand...

Nice - I could add to the list (!)

There are, for example, some plumbers (could also be taken as RAF slang) who do some questionable things that are very amusing =>

https://www.youtube.com/channel/UCp68_FLety0O-n9QU6phsgw

^^^^^^^

I had a mate who was an aircraft technician for 10 years he then went on to manage a garage, I wouldn't let him near my car.

Col

Untill recently I used to audit offshore rigs. One of my pet hates was torque wrench calibration. The older rigs with workshops would have a calibation set up with a test cert and the mech tech (usually a permament employee) would periodically calibrate the wrenches, great, The new rigs would often just keep buying new torque wrenches and rely on the manufacturers cert which they (usually a short term contractor) would then loose. The issue on rigs is that the torques can be very high and without a calibrated wrench its easy to stop short. But my real concern was the accululator charging rig and home made adaptors. I found one with no gages and no regulator - 300 bar controlled with a bottle key! I'd already investigated an incident where a guy used a home made adaptor to put an HP bottle on an LP accumulator and blew off one arm along with the side of his face.

Stretch said:

Oh dear - some of you scare me!

There are certain parts of the vehicle - in particular U-bolts - imagine them coming off at any speed - that deserve a bit of respect

"Counting white knuckles" isn't always appropriate!

Click to expand...

tightening u bolts is best done a little on each till all tight ,exact torque isnt as important as that ,knowing what yout tightening andwhy is something people should learn,u bolt where either unf or metric both would require different torques

jamesmartin said:

tightening u bolts is best done a little on each till all tight ,exact torque isnt as important as that ,knowing what yout tightening andwhy is something people should learn,u bolt where either unf or metric both would require different torques

Click to expand...

I agree entirely.

Col

Agreed, mine look to be the originals. My Series seems to have been in use most of its life and leaking all of it so most of the underside is quite orignal (but clapped out). I prefer to check the u bolts regulary rather than do them up really hard. Most times they are fine, every now and them one will take 1/4 turn.

rob1miles said:

Untill recently I used to audit offshore rigs. One of my pet hates was torque wrench calibration. The older rigs with workshops would have a calibation set up with a test cert and the mech tech (usually a permament employee) would periodically calibrate the wrenches, great, The new rigs would often just keep buying new torque wrenches and rely on the manufacturers cert which they (usually a short term contractor) would then loose. The issue on rigs is that the torques can be very high and without a calibrated wrench its easy to stop short. But my real concern was the accululator charging rig and home made adaptors. I found one with no gages and no regulator - 300 bar controlled with a bottle key! I'd already investigated an incident where a guy used a home made adaptor to put an HP bottle on an LP accumulator and blew off one arm along with the side of his face.

Click to expand...

Eeek

That's not nice - that's one seriously harsh lesson from the school of hard knocks (and I bet the insurance situation was a nightmare)

jamesmartin said:

tightening u bolts is best done a little on each till all tight ,exact torque isnt as important as that ,knowing what yout tightening andwhy is something people should learn,u bolt where either unf or metric both would require different torques

Click to expand...

rob1miles said:

Agreed, mine look to be the originals. My Series seems to have been in use most of its life and leaking all of it so most of the underside is quite orignal (but clapped out). I prefer to check the u bolts regulary rather than do them up really hard. Most times they are fine, every now and them one will take 1/4 turn.

Click to expand...

I completely agree that care should be taken when fitting U bolts.

The use of U bolts to strap an axle to crude cart horse leaf springs seems simple enough but as you infer there is a subtle relationship between the tightness of nuts you are winding on either end of a threaded bar...

...the added complication of the bar being bent in a U shape means it can get snagged on the axle during the tightening process.

I imagine I am not the only one to have experienced rusty old rounded nuts on the underside of U bolts meaning you need to cut the old U bolt free from the axle:- Cut through them and they don't have make you jump when they snap through during the last bit of the cut!

These U bolts are under a lot of tension - applying that tension when tightening the nuts is important. Sure you should not disregard any misfitment of the U bolt around the axle - you should realise that if you pull one side the other side might move (!) - but if you tighten the final fraction of a turn with a torque wrench you are most likely to not overtighten the U bolt and end up in the plastic range (described previously in the thread)

Checking torques after a rebuild and after the first few miles is of course important as is periodic checking of your vehicle (especially when many of the Series Land Rovers do not necessarily need to have an MOT any more)