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Discussion Starter #1
I am not a Mech Engr, I am just an Elec Engr (my career - retired now for 19 years). Just to,let you know I am not Mech Qualified. :-( I have some basic knowledge of issues with Torqued Nuts (thread stress, cleanliness, etc. and that is it.

I have been in E Mail Conversation with a MC Buddy that is a retired Mech Engr (Was involved with big cranes mostly). We discussed the Torque Issues on the Shaft Nut for the Variator End of the CVT Pulley on Burgman 400, and the fact there have been issues of the nut coming lose.,

I don't understand the tech of all this (links he sent are Technical and complicated). However, it becomes critical to do it right (guess we luck out by doing it half right). :confused:

By The Way, the washer on my Burgman 400 (2011) appeared pretty much like a flat washer to me (I guess I expected to see more of a curve or bend giving a spring load effect). Anyway, I made sure it went back on with the side of he washer oriented as they were when I took it off. (Paint was OUT BOARD). Plus, I tightened the Nut snug with regular wrench and then worked my way up from 50FTLB to 75FTLB (partly to check or get a feel for the Torque Wrench - a Harbor Freight that I have not calibrated and to test my Fin Fan Hold Tool)

Including pictures of my "TOOL". Crude, but worked. Would use stiffer board and design so could switch to other side for Nut Removal (as it is - interfered with the center kickstand if on the other side). I made it work here by using the 2x4 and kneeling on the 2x4 when removing the nut. It worked in the position with out the board for tightening the nut (as tighten CW).

OK - Here is what friend sent.


If shaft nut backing off is an issue at 75 ft-lb tightening torque, I doubt if Plumbers Goop would help.

I agree that on ANYTHING on the threads would throw off the proper tensioning of the nut/shaft. The goal is to deflect (tension) the shaft by the action of the nut. Torque is not the best way to assure the proper amount of stretch is achieved. On cranes, for critical fasteners, we would use turn-of-the-nut method over torque wrenches. Tests by the AISC has shown proper turn-of-the-nut method is more accurate than using torque wrenches, particularly wrenches that have not been routinely certified. I'm a little surprised that if the nut connection is critical that it is not being used. Torque is directly proportional to the coefficient of friction between the nut and the thread of the bolt (or the shaft, in your situation). Torque charts are based on certain conditions, most commonly being that the threads of the fasteners are clean and only have the lubrication from the manufacturing process. Some charts are based on other factors like use of anti-colloidal suspension products, like Never-Seize.

See: http://www.appliedbolting.com/turn-of-nut-bolting-method.html

For structural connections, Alcoa structural engineers use load-indicating washers. That method is even more accurate.

See: http://www.portlandbolt.com/products/washers/load_indicating_washer.html
 

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I have removed and reinstalled the variator and clutch assembly on my '03 400 at least 20 times (playing with sliders/ramp plates/springs/etc.) in the nearly four years I have had the scoot.and never had either nut come loose. In fact I do not believe they would ever on any 400, IF they are properly torqued to begin with.

Those that have come loose have often been linked to improper installation, with not making certain the belt is free in the variator being perhaps the most common theme.

The washer is a Belleville spring, it should be mounted with the concave "cup" facing inward--placing the washer on a flat surface will readily identify the convex and concave sides.

Hopefully without sounding like a broken record I will once again advocate for the use of torque sticks and an impact wrench for tightening these nuts. No holding tool is needed and the resulting torque will be easily within +/- 3%, as good as any "clicker" type torque wrench.

Torque sticks (happen to be on sale at HF now $55:



65 lb·ft torque stick in use:



I have always used the sticks on the variator (75 lb·ft) and clutch (65 lb·ft) on my 400 (and on many other vehicles for lug nuts and other critical fasteners). Like a beam torque wrench they will always be accurate, as long as they are not cracked or otherwise broken. I have many "name-brand" sticks accumulated over the years, the HF set is as good as any as reasonable too...

"Turn-of-nut" is often used for automotive fasteners, however that is generally accomplished via a sequence of an initial torque with an torque indicating tool, then often backing the nut off and retorquing to a specified value, and in the last adding x degrees of additional rotation.

That said, my experience has been that for these nuts on the 400 if properly torqued there is nothing to worry about.

One last neat tool, a digital torque adapter, also from HF:



Read more about it here, I checked its accuracy using dead-weights and now use it only as a standard for calibrating my "real" torque wrenches--it's pretty cool...
 

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"I am just an Elec Engr"
JUST!?!? I am a civil and would have been a mechanical but for the life of me, I couldn't understand electricity. The weirdest most nebulous chapters in any Physics book. Weird. :rolleyes:
 

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/\ I bought the HF torque wrenches 1/2 inch and 3/8 inch for $9.99 each. :)

I had never heard of Torque Sticks. What a cool tool, I just might have to make some room on my shelf for those!
 

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"I am just an Elec Engr"
JUST!?!? I am a civil and would have been a mechanical but for the life of me, I couldn't understand electricity. The weirdest most nebulous chapters in any Physics book. Weird. :rolleyes:
I was going to comment on that as well, there is no such thing as "just" an engineer. Both my grandfathers were engineers (one a civil and the other, my maternal grandfather, a stationary steam engineer), and my father is a mechanical engineer--so as you can see I ha little choice in life.

Torque sticks are great tools. They work the same as trying to bang in a nail at the end of and unsupported board--at some point it does not matter how big a hammer you use, or how hard you hit the nail, it just will not go in any further because the "springiness" of the board is absorbing all the force.

They are torsion springs, manufactured to absorb all torque (within reason) except that for which they are designed to transmit. It doesn't matter how hard the impact wrench "bangs" the input end, only so much torque will be delivered to the fastener. You do not want to "lean on" one with the impact wrench though, just watch the socket and when it stops turning give it just a few more blows and you're done...

---------------------------------
Engineering is the art of making what you need, from what you can get.
 

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Discussion Starter #6
Thanks for the feedback.

Had information on Torque Sticks (I think from other psots on here - maybe yours).

Probably the way to go VS DIY Holding Tool that might break fins. :(

I thought they were more expensive than the $55 for a set.

Then still need an Impact Wrench that will go past 75 ft lbs.

THat digital adapter might be even better (Cheaper and they say +/- 2%). Plus it is ELECTRICAL - maybe that is not a plus. GROAN
 

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This has been discussed before- I would NOT use an impact tool to INSTALL nuts, especially on the crankshaft. Hence, the need for a variator holder.

Same for my old Harley- Take off the crank sprocket with impact, but install with torque wrench. Too many delicate bits inside there.
 

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This has been discussed before- I would NOT use an impact tool to INSTALL nuts, especially on the crankshaft. Hence, the need for a variator holder.

Same for my old Harley- Take off the crank sprocket with impact, but install with torque wrench. Too many delicate bits inside there.
If you make certain the tool is supported and held "floating", and centered on the shaft, so that the ball bearings are not subjected to the impact blows, there is no problem. Also do not just sit there and let the impact wrench pound away--using torque sticks when the socket stops turning, stop the wrench.

it is only when ham-handed fools bang away on a anti-friction bearing supported shaft like it was a lug nut on a Kenworth that the races can become indented from the impacts. I have used impact wrenches and torque sticks on crank and other a/f bearing shafts for years and years wtih no problems...
 

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Gotta say that torque sticks do work, but are mostly used for working in inaccessible areas, where a standard torque wrench is not easy or practical to use. Other than that, there is no reason to limit yourself to buying torque sticks when a torque wrench is so much more versatile and can work out less money to buy. You can dial in any torque setting you wish instead of needing to buy loads of 'torque sticks'.
 

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I agree; I have at least a dozen torque wrenches i have accumulated over the years and would not part with any of them.

However very seldom are torque specifications so precise that 5% one way or the other makes any difference; also, most torque wrenches have at best +/- 3% accuracy--IF properly calibrated.

Fact is that contemporary vehicle torque specifications, when expressed in lb·ft, are mathematical conversions from the engineer's original metric specs--often rounded to some more readable, easier to deal with, value (or as I have seen sometimes incorrectly converted).

For example:

The metric spec for the clutch shaft nut (2003) is 85 Nm (62.7 lb·ft), but is presented in the manual as 61.5 lb·ft (2.0% less than the Nm spec);

Simlarly the crank nut metric spec is 105 Nm (77.4 lb·ft), but stated as 76 lb·ft (1.8% less);

Use a torque wrench (or stick) on the crank nut that is operating at the negative end of its +/- 3% accuracy, and the stated lb·ft specification, and the fastener would be actually torqued to 73.7 lb·ft, or 4.8% less than the recommended 105 Nm. My point is that very few consumer level vehicles have torque specifications that are "all that" critical; those that are are usually stated at X amount of additional rotation after first setting a base point.

The procedure for the crank bolt on my Mustang is:

Torque to 65 lb·ft;
Loosen bolt 1 turn;
Torque to 105 lb·ft;
Tighten an additional 90°;

In the last; calibrate your torque wrenches, and know their accuracy at various ranges. If you are obsessive about that sort of thing (like me) this will allow you to get it right every time.

The digital torque adapter I mentioned earlier is a great instrument to check the calibration of your torque tools. Wrenches can be checked directly, sticks can be used to tighten a fastener, then use the digital instrument to check how much torque it takes to tighten the fastener "just a bit more". The digital indicator can easily be dead weight calibrated...
 
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