Belleville Washers

"What we have here is a failure to communicate" Cool-hand Luke

huh?????

I believe "saving torque" is a misnomer. How can you "save" torque?

There are many advantages to using Belleville washers but I just can't wrap my mind around the savings thing.

It sounds like a salesman pitch. 2nd Class

maybe 'saving torque' means that:

without Belleville: 100 Nm required

suing Belleville: 40 Nm required.

maybe!

You have to ask him...... save 60% in torque,

• in what way?
• and how does that save me?

Thats a good start, but have the salesman give you specifics, not just statistics.

maybe 'saving torque' means that:

without Belleville: 100 Nm required

suing Belleville: 40 Nm required.

Yes, Maybe, but a good question to ask in return is how does that help me.

A review of DIN 2092 would reveal if the statement "using Belleville washers, you will save 60% in torque" is true.

For a smaller information bite, a pretty good reference for them is available from SPIROL.

I agree with the others; 'saving torque' is meaningless salesman speak.

Heck just use two and you'll save 120% and the machine will run itself
Baaaad kitty
Del

Belleville washers will not save you from torquing down the bolt to the rated torque specs.

Belleville washers have their own load spec. They need to be tighten to the load spec to bind and lock the bolt properly.

Why would one use a Belleville washer at all, if the fastener will be torqued to the point that the washer is squeezed flat?

Optimally you want to pick the Belleville washer with spring load that will match the torque specs for the bolt application. So when the washer lays flat the torque specs are met. The spring force and contact area friction keeps the bolt from backing out. The washer laying flat provides the maximum contact area.

OK,

But, I take exception to the concept of a Belleville washer being used as a locking washer.

I'll buy their ability to MAINTAIN tension on a threaded fastener, to a point.

I admit that you probably know a lot more about these than I do. Just askin'.

Belleville washers are also used to apply pressure to clutch packs in torque-transmission devices. If installing one where none was before, or installing a higher-pressure one, you will see an increase of output torque vs input torque due to less slippage. "Savings" is not the right word to use here.

Agreed.

If we are discussing rotating shafts some torque reduction may be realized by using these, instead of other means of alignment.

Using Belleville Washers is what allowed the Millennium Falcon to make the Kessel Run in less than 12 parsecs.

............?

.

A question no one has asked yet. What will you use Belleville washers for?

What do you use now?

Hi Lyn, We bent the 3 inch shaft of a net winch and using Belleville spring washers, 5 on each end of each of the the six coupling bolts kept us going until we got a new shaft. The only problem we had was keeping an eye on the nuts as there was not enough space for locking. We had the new shaft made and it was months before we changed it because the jury rig was doing the job well. So that is one useful application. i don't know how they could save torque but there are a lot of things I don't know. To quote Russell, "only fools and fanatics are always sure". Gerry D.

"To quote Russell, "only fools and fanatics are always sure"."

It is such a pleasure to make the acquaintance of another Nipsey Russell fan.

^{Oh, prolly the other Russell.}

A little wobble won't hurt.

Yeah, usbport's comment could be sort of confusing.

It happened a long time ago in a galaxy far, far away....

The washers were made from transparent Aluminum, as I recall. That may be why they didn't get much visibility then.

Now you're mixing franchises.

Gentlemen,

The salesman is RIGHT! I cannot say it is 60% but some torque reduction can be noticed.

What was not understood is that it will be the case ONLY if the the turning piece bolt or nut is in contact with the small spring diameter.

For a given preload the torque depends on the mean thread diameter, on the thread pitch AND on the contact diameter between head or nut and the not turning part.

T= F*(016*P+0.5/cos30°*µth*d2+0.5*Dm*µh)

P= thread pitch

d2= mean thread diam

µth= friction coef for the thread in the body

Dm= mean contact diam of head

µh= friction coef for head

If Dm is smaller torque will be less!

But there is an important BUT: those springs are designed with high stress levels and have a trend to relaxation which will reduce the preload in time.

Their usage should be very well checked: under the preload the deformation should be such that no relaxation occurs. This means that the spring must be designed for a much bigger load than the bolt preload .

I don't think you can say that when we haven't established the context yet. Several posters have assumed he's referring to bolts, but he hasn't clarified, or said what is meant by "saving" torque, despite a number of prompts.

Every opinion is based on an assumption. I made the assumption that the question was related to the use of those washers in bolting between bolt head/nut and clamped parts.

Why can I not say what I think ?

If the OP thought about an other application field this does not contradict what I wrote which is valid in the bolting field.

I have to add that this practice leads to 2 negative results:

- in fact the preload is not more stable over time than in a right tightened assembly (this was demonstrated by specific measurements).

- the introduction of this compliance increases the part of load which is for the bolt and decreases its fatigue life expectancy.

Now to estimate the torque possible decrease. It will affect ONLY the term F*0.5*Dm*µh.

If we consider an M10 bolt the washer has usually 11 mm pass hole and the head a contact diam 17 mm. Dm≈0.5*(11+17)=14mm. µh≈0.12...0.14

If the contact is on a Belleville washer the contact surface will be between 10 and 13.6 if the washer is eccentric Dm≈11.8mm. The friction cof. will be higher since the contact is on an edge and we can assume it will be 0.18...0.2. If we compare the 2 products Dm*µh we have without washer 1.96 and with washer in the worse case 2.36. If we consider the washer with a di= 10.2 (see Spirol data sheets) and assume the same friction the value with washer will be 1.84 (µh=0.18). and 1.43 if µh=0.14. This means that in the BEST possible configuration the gain can be only 27% of the head friction. This friction represents about half ot total so that with respect to tightening torque the best possible gain will be 13%. A bit far from the 60% mentioned by the salesman.

OK OK, you can say what you think, no offence intended!

Yes, but only if you buy 10 or more.

I am confused so its back to me just welding everything together again from now on.

I think what the salesman is trying to say is: You can reduce the amount of torque you place on the fastener and still prevent the fastener from becoming loose. When you use the normal torque figure, without a belleville washer, you approach the point where the threads distort and lock. This distortion prevents the fastener from loosening. Using a belleville washer eliminates the thread distortion. This is what torque controlled fasteners are about. Fasteners that are used in high rise steel construction, bridge and railroad construction rely on distorted threads for security. Once these fasteners are undone, they have to be replaced with new fasteners.

And this was demonstrated to be wrong! A threaded fastener gets loose under the effect of TRANSVERSAL loads. Axial loads are not the reason as far as they do not go over the compression limit of clamped parts. Transvers microsliding is the reason for preload losses. A fastener stays in place if the friction in the thread is not function of preload this is the reason why some threads are deformed from the beginning in order to generate friction by tightening high enough to maintain the relative position of threads but not as function of preload. If one tightens the threads up to a plastic deformation the preload is maintained over time due to the thread relaxation.

Or use a serrated Belleville washer.

The positive effect depends on the geometry of serrations. Not all types bring a +

This reminds me of the lock nut conversation, we each had an assumption about the situation in which it was used.

We used these and similar designs to take up long term concrete creep/relaxation and maintain tension in drilled in expansion or epoxy anchors.

It is always same problem why preload disappears and how can it be maintained.