Torquing head bolts

[R. Phillips]

I plan on doing a top end this winter, but wondered how in the heck I was going to torque those recessed nuts on the bottom of the cylinder head. I've got a torque wrench and didn't want to buy a "specialty" one, just for this job.

So, I remembered I had this formula in an old training manual.

If you add an "extension" to your torque wrench (90 deg off the handle) it has no effect on the reading.
BUT if you add an adapter i.e. open end or boxed end, which in effect extends the length of the torque wrench, you will be exerting more torque on the bolt/nut than what the torque wrench is reading. This is not good when torquing into aluminum.
Also, you have to keep the adapter in line (parallel) with the torque wrench handle. If not the torque changes.

Here is the formula for using an adapter you can get at the parts store, and use on your old torque wrench:

Tw = Ta x L
........ (L+A)

Tw = Torque wrench scale reading (what to set torque wrench to)
Ta = Torque exerted at end of adapter (torque needed on nut)
L = Lever length of torque wrench (middle of handle to head)
A = Length of adapter (hole to hole)

You guys may know all this already, I haven't seen it posted.
Hope it helps someone.

Robert

 

[srhill]

I'm glad I know you and your such a good pal, that way I don't have to remember all of this scipheren. I can just get you to come over and help me. Hee Hee

 

[IrishEKU]

Two words to add that you missed in your post, "Star Pattern".

 

[canyncarvr]

I'm not sure how this matters. Yes..it's true, but what are you going to attach to your torque wrench to get on the shrouded cylinder nuts?

Buy the tool, keep it at 90º to your torque wrench and you're done.

I guess if you're of the mind, 'I don't need to put a new bearing in this piston..the old one is fine!' then you'd argue the worth of being able to correctly torque your cylinder...and the worth of having the tool to do it.

As I read it, at least TWO of you could share the expense of the proper tool. At less than $10/ea..that's pretty cheap insurance.

They're hanging on a rack 1/2 mile down the road at the local yamaha shop.....

Cheers!

 

[R. Phillips]

Thanks cc, I didn't realize there was an attachment out there made just for this job. I thought I might have to but a special torque wrench or something.

Sorry for the insignificant thread.

Robert

 

[canyncarvr]

It's not insignificant.

It posted a question, got an answer, cleared up an 'issue'.

PRWOBWUM SAWVED!!!

.......which is kinda the whole point, 'eh??? ;)

 

[R. Phillips]

That's ok cc, I know you didn't mean to call me cheap ?? ;)

I just knew that if any bolt/nut on the bike needed to be torqued, it was probably these.

I'll have to take a look at this tool you mentioned, to understand how it works. All I know is that if the head of a torque wrench is not directly over the nut you're tightening, the torque is changed. I don't see how a tool can go on these nuts, and allow the head of the torque wrench to be directly over the nuts. But those Japanese are pretty smart.

The adapter I mentioned in my original post is simply an open (or boxed) end wrench with a square hole on one end that clips on the torque wrench head. We use em at work all the time, but have to use the formula to convert the torque.

Maybe some of the readers can use the formula on different applications. That was my original intent.

Thanks again for your response. I hold you reply's with high regard, and (believe it or not) have actually used some of your advise to fix my bike. ;)

Robert

 

[canyncarvr]

Oh-oh...sorry about that last sentence. Hope after it was 'fixed' with my advice, you got it repaired!!

Now then...my one brain cell is confused.

I don't see a reference in your first post regarding a 'tool'. You're referring to something other than the top of this thread...right?

And IN your first post (well, this thread)...

If you add an "extension" to your torque wrench (90 deg off the handle) it has no effect on the reading.

This is indeed true.


Then:

All I know is that if the head of a torque wrench is not directly over the nut you're tightening, the torque is changed.

That is NOT so..and in conflict with the 90º statement.

It's the length of the torque lever that is the issue. That's why 90º gets you no change.

So...if you have such a tool already (what you describe is exactly what the motion-pro 'special tool' is..boxed ends with a square hole in the middle that accepts a ratchet drive), you're good to go. You will need NO mathematic conversion if you keep the adapter @ 90º to the torque wrench. By the way, that's easy to do in this situation.

Please tell me this all makes sense??

 

[xr400forever]

Is it maybe a Crowsfoot adapter we are thinking of here. I thought it would work on my bike too so went and bought one but even that did not fit on all of the lower cylinder bolts. I liked the fishing scale and wrench idea, I should get the proper tool for next time though!

 

[R. Phillips]

OK, I admit I was using my (cell depleted) brain which slept through a torquing class 15 years ago to try and explain this torquing thing..........
so, I called my old instructor to clear me up on this.

Yes, if you use a "crowsfoot" or the "motion-pro" tool, and keep it 90 degrees or perpendicular to the torque wrench, it will not change the torque.

Now, lets get back to more important threads.

P.S. To canyncarver: In response to your "fix" vs "repair" gramology lesson.
Down here in Sweet Home Alabama, we "fix" things (usually with
duct tape and bailing wire). "Repairing" stuff is usually
too complicated and too expensive for us. ;)
.
.

 

[Jackpiner57]

Very good post R. Phillips, I have been wondering the same thing about how a crows foot will change torque leverage.

Well now you guys have confused me!

The way I see it is that when you add a crows foot, it effectively increases the overall length and thus increases leverage.

I think your original post is correct in theory, and I have no reason to doubt the formula you provided.

 

[canyncarvr]

What's the confusion?

Or...what's the question?

 

[BRush]

What's wrong with a little math?

The formula:
Required Torque * Extension Factor

Where:
Extension Factor = Wrench length / (Extension length + Wrench length)

Example:

You need to torque a nut to 18 ft-lb. The distance from the center of the grip to the center of the square drive of the torque wrench is 13 7/8 in. The extension length is 3 in.

The torque value you set the wrench to (assuming the extension sticks straight out and is *not* at 90 degrees):

Extension factor = 13.875 / (3 + 13.875) = 0.822

Torque setting = 18 * 0.822 = 14.8 ft-lbs

 

[canyncarvr]

Nothing wrong with a little math.

What you wind up with in this case, though, is an ever changing length as the ratchet operates.

...unless you move the adapter..and do NOT operate the ratchet. In which case, why not just set it up @ 90º and forget about it?

Or you can run a different set of numbers everytime your ratchet 'clicks'.

Sounds like WAY too much of a good time! ;)

 

[R. Phillips]

Some torque wrenches (TW) have needles and do not ratchet. In this case you just remove the socket/adapter from the nut and reposition, just as you would a common wrench. You would do the same on a ratcheting type TW if an adapter is used.

The ratchet on the TW is for tightening or snugging the nut prior to torquing. Once you get to the actual torque point, it clicks, and you shouldn't need to ratchet. (P.S. One click is enough)

If you turn the adapter to 90 deg off the torque wrench head and "set it and forget it", how do you "ratchet" without it moving off the 90 deg angle ? Sounds like you would have to reposition something ?

Anyway I'm sorry for the confusion you readers might have experienced in this thread. My original intent was to give a formula to calculate torque when using an adapter. Please let me try to un-confuse this.

A. If you clip an "extention" on to a torque wrench that goes "down" from
the TW head, like to get at a nut down in a hole, it does not change the
torque value on the nut from what the reading on the TW is.

B. If you clip an "adapter" (i.e. crow foot or motion-pro tool) on to a torque
wrench that goes "out" axially from the TW handle, like to get in a
recessed area that the TW head will fit in, it does change the
torque value on the nut from what the reading on the TW is.
In this case, you need to use the conversion formula.

C. If you clip an "adapter" (i.e. crow foot or motion-pro tool) on to a torque
wrench that goes "out" axially from the TW handle, like to get in a
recessed area that the TW head will fit in, and turn the adapter 90 deg to
the TW handle and operate the TW, it does not change the torque value on
the nut from what the reading on the TW is.

Thank you Jackpiner57 and BRush for the positive responses. ;)

Robert
.
.

 

[BRush]

With KDX cylinder base nuts I find that having the extension straight out works best. You can't really allow the wrench to ratchet when using an extension for obvious reasons, but it's really not much of a limitation since you're only using the torque wrench for the last few turns to achieve proper torque.