62 replies to this topic

[cheapracer]

Does one know the (aprox) area/percentage that one can bore/hollow a (solid) bolt before a loss of strength occurs or could one point me to an available chart on the net?

[Lukin]

So you mean the effect of thinning the bolt on the yield and ultimate stress or the effect on the factor of safety?

I might be way off, but assuming there isn't some heat treatment in the actual hollowing process the yield and ultimate stress should be the same there is just less load bearing so a decrease in the factory of safety?

The different kinds of loadings (axial, bending, shear) will give different safety factor reductions though (depends on their proportionality to area/polar moment).

Or am I way off? Or are you looking for a quick way to circumvent the calcs?

[rms]

ANY reduction in cross sectional area will reduce strength !!!!!!!!!!!!

[McGuire]

Originally posted by cheapracer
Does one know the (aprox) area/percentage that one can bore/hollow a (solid) bolt before a loss of strength occurs

None.

[Bill Sherwood]

I'd be interested in finding out about the strength of a bolt that, say, was 50% bigger in diameter but had a hollow shank.

[zac510]

Originally posted by Bill Sherwood
I'd be interested in finding out about the strength of a bolt that, say, was 50% bigger in diameter but had a hollow shank.

Same thread pitch?

[saudoso]

Originally posted by Bill Sherwood
I'd be interested in finding out about the strength of a bolt that, say, was 50% bigger in diameter but had a hollow shank.

A bolt is likelly not to benefit from that.

A bigger diameter/holow part with the same wieght (corss section area) will be stronger to torsion and bending (moments of inertia are the key factor), things bolts are not there to hold.

Traction and shear depend on cross section only, so no benefit and a heavier nut.

Ricardo

[Bill Sherwood]

Originally posted by saudoso


A bolt is likelly not to benefit from that.

A bigger diameter/holow part with the same wieght (corss section area) will be stronger to torsion and bending (moments of inertia are the key factor), things bolts are not there to hold.

Traction and shear depend on cross section only, so no benefit and a heavier nut.

Ricardo

That makes sense, thanks.

[phantom II]

A certain NASCAR team running a restrictor plate race had hollow carburetor mount bolts. This would be the only good/bad reason for having hollow bolts. Cheatracer may have a legitimate/illegitimate reason for asking this seemingly absurd question. Maybe he has a hidden nitrous package.

Originally posted by McGuire



None.

[McGuire]

Originally posted by phantom II
A certain NASCAR team running a restrictor plate race had hollow carburetor mount bolts.

That would never happen in sports car racing, where the participants are all gentlemen.

[Fat Boy]

Originally posted by McGuire


That would never happen in sports car racing, where the participants are all gentlemen.

That's not the reason, it's just that they don't have carburetors.

[shaun979]

There have been connecting rod makers that have gone to larger diameter hollow bolts in order to reduce deformation by spreading out loads a little more instead of having it concentrated around a point.

[gbaker]

Originally posted by shaun979
There have been connecting rod makers that have gone to larger diameter hollow bolts in order to reduce deformation by spreading out loads a little more instead of having it concentrated around a point.

A Ringlock nut will do the same thing.

[shaun979]

What is a ringlock nut? They don't use nuts.

[AndrewD]

Originally posted by McGuire


That would never happen in sports car racing, where the participants are all gentlemen.

You must be taking the piss. If not;

There are no gentlemen in racing. Fair enough everyone says they want to beat fellow competitors on the race track not because of failures etc. But you have to understand that if there is an advantage regardless of whether it 'bends' the rules or not, people are going to take it!

[Fat Boy]

Originally posted by AndrewD


You must be taking the piss. If not;

New member.....doesn't know Mac too well, does he?

[saudoso]

Originally posted by shaun979
There have been connecting rod makers that have gone to larger diameter hollow bolts in order to reduce deformation by spreading out loads a little more instead of having it concentrated around a point.

Longer bolts (pins? sorry, english is not my language) sitting on rubber bushings like suspension parts (or rods?) are subject to bending, and would benefit from that.

[McGuire]

Originally posted by AndrewD


You must be taking the piss. If not;

There are no gentlemen in racing. Fair enough everyone says they want to beat fellow competitors on the race track not because of failures etc. But you have to understand that if there is an advantage regardless of whether it 'bends' the rules or not, people are going to take it!

Thanks for playing! You will receive the home version of our game and a year's supply of Rice-A-Roni.

[AndrewD]

Originally posted by McGuire


Thanks for playing! You will receive the home version of our game and a year's supply of Rice-A-Roni.

My pleasure,

I look forward to receiving it in the post along with a hefty cheque for all inconveniences encountered

[gbaker]

Originally posted by shaun979
What is a ringlock nut?

http://www.google.co...elf locking nut

They don't use nuts.

But they could, and possibly should.

[saudoso]

Originally posted by gbaker

http://www.google.co...elf locking nut

That's a smart chunk of metal.

[desmo]

Originally posted by gbaker
A Ringlock nut will do the same thing.

"Inventors: Paul B. Hafeli, Gregg S. Baker"

[gbaker]

Pretty fast, desmo.

[shaun979]

Originally posted by gbaker
But they could, and possibly should.

Nice invention Gregg, though I'm not so sure that they should use it. There is lots of money spent trying to find gains in these areas and if they have passed over something that allows equal or better performance at lower cost , weight, or complexity, I'd be surprised. You should approach the rod makers and see what they say.

I wonder how much load you could put on a nut designed like that. It looks like it would bend pretty easy and not allow much load to build until the inner edge bottoms out. Also the loads concentrated in a thin ring on the cap end...galling?

[RDV]

Fat Boy- That's not the reason, it's just that they don't have carburetors.

What is a carburetor? Is it used in racing cars?

[cheapracer]

Originally posted by Lukin
So you mean the effect of thinning the bolt on the yield and ultimate stress or the effect on the factor of safety?

I might be way off, but assuming there isn't some heat treatment in the actual hollowing process the yield and ultimate stress should be the same there is just less load bearing so a decrease in the factory of safety?

The different kinds of loadings (axial, bending, shear) will give different safety factor reductions though (depends on their proportionality to area/polar moment).

Or am I way off? Or are you looking for a quick way to circumvent the calcs?

I actually was refering to bending stress rather than shear, sorry my post wasnt clear enough. I was actually trying to remember some info in the Mechanics textbook supplied in my first year apprenticeship at Frankston (Victoria) Tafe that had this info, but man is that a long time ago!

Searching the web came up with some more information as to what I was chasing, thus...

-- For a given material, and given outer dimensions, the maximum strength is achieved if the rod is solid (not hollow), but this also takes a lot of weight.

For a given material, and given weight, the maximum strength is achieved by a hollow cylinder, that is of larger diameter than the solid rod of that weight.

Most of the strength of a cylinder comes from the outer portions. I think the contribution goes like the cube of the radial position. So, if you took a solid rod and drilled out a half the volume from the center, you do not lose half the strength. You only lose about 10% of the strength, but you've saved on half the weight.

So, strength to weight ratio is better for a hollow pipe than a solid rod.

-- Between a solid pipe and a hollow pipe of the same weight, the hollow pipe will be more resistant to bending. It will also have a much larger radius.

[cheapracer]

Originally posted by phantom II
Cheatracer may have a legitimate/illegitimate reason for asking this seemingly absurd question.

Not happy, reported to moderator.

[rms]

Originally posted by cheapracer


I actually was refering to bending stress rather than shear, sorry my post wasnt clear enough.

[/I]

You want to load a bolt (or tube) in bending ???????????????????????

[gbaker]

Originally posted by shaun979
I wonder how much load you could put on a nut designed like that. It looks like it would bend pretty easy and not allow much load to build until the inner edge bottoms out. Also the loads concentrated in a thin ring on the cap end...galling?

Ringnuts are used in critical applications where galling is a low priority, assuming it occurs. Surgeons have implanted over 20,000 of them, for example. The primary advantage is an increase in the amount of torque required for removal. There are no load limits beyond what one would encounter in a normal fastener design.

Originally posted by shaun979
..if they have passed over something that allows equal or better performance at lower cost , weight, or complexity, I'd be surprised.

Don't count on it. One finds few brain surgeon in racing.

[shaun979]

Originally posted by gbaker
[B]Ringnuts are used in critical applications where galling is a low priority, assuming it occurs. Surgeons have implanted over 20,000 of them, for example. The primary advantage is an increase in the amount of torque required for removal. There are no load limits beyond what one would encounter in a normal fastener design.

The loads are not normal when it comes to high performance rod bolts. I don't see a need to increase amount of torque required for removal since the rod bolt is already stretched and loading threaded areas heavily.

Don't count on it. One finds few brain surgeon in racing.

Nahh, I think I will continue to count on them not having passed something over like this. If ringlock nuts turn up on high performance rods you'll have proved me wrong, but not till then.

You can't claim from a distance that you have a solution or advantage without ever having competed in that specific arena. If you had a definite solution or advantage, you could convince a company very quickly to use it. But either you do not have one, or you do not want to even try to apply it in that area, although you like to talk about it. Reality is though... applications differ widely, and talk is cheap.

[imaginesix]

Originally posted by cheapracer
Not happy, reported to moderator.

That's as close as PII has ever come to being politically correct. Love the irony.

[FrankB]

Originally posted by rms


You want to load a bolt (or tube) in bending ???????????????????????

What is unusual about someone who wants "to want to load a tube in bending"?

http://www.prosiectm...gbritbridge.jpg

http://www.gutenberg.../bridges_17.png

http://www.britannic...ebirt001p4.html

http://www.excelsail...s_and_Flags.jpg

[rms]

Originally posted by FrankB


What is unusual about someone who wants "to want to load a tube in bending"?

[/url]

Just because it is not unusual in 'low tech' applications doesn't mean it is the correct way structurally.

[FrankB]

Originally posted by rms

Just because it is not unusual in 'low tech' applications doesn't mean it is the correct way structurally.

I am not sure what you mean by "doesn't mean it is the correct way structurally." If the use of a tube solves a structural problem economically and safely how can it be incorrect? If a tubular framework for a roller coaster is "wrong", why do so many use them? What would you say was the "correct" way to solve the problems of roller coaster construction?


Is this "high tech" enough for you?

http://images.google...2006-39,GGLJ:en

edit: Isn't the monocoque construction of a Formula One car essentially a tube with various openings (for the cockpit, pipework, etc) and mounting points (for suspension, engine etc)? Is this also an incorrect or low tech structural use of a tube?

[rms]

Talk to any university engineering department and you will find that to subject an object to bending loads is bad practice and to be avoided if possible.

I thought we were talking engineering, not economics and building something at the lowest price.

With a monocoque tub the bending/beaming loads are resolved in tension/compression in the extreme fibres.

Shouldn't engineering be about the pursuit of excellence and not what we can get away with or how cheap we can make it ?

[FrankB]

Originally posted by rms
Talk to any university engineering department and you will find that to subject an object to bending loads is bad practice and to be avoided if possible.

Imposing bending moments on members that are not designed to carry them is bad practise, but total avoidance of bending stresses on all members is not always possible. Why is the use of a tube (with localised stiffening to avoid buckling if necessary) any worse than using an I section (possibly also with web stiffeners) as a structural component that is subject to bending?

Originally posted by rms
I thought we were talking engineering, not economics and building something at the lowest price.

Surely good engineering must take into account the economics of the problem? I would never argue that the cheapest design is the best for any particular project, but by the same token the most expensive design is not necessarily the best either.

Originally posted by rms
With a monocoque tub the bending/beaming loads are resolved in tension/compression in the extreme fibres.

Agreed, but isn't the same true of an I section or a space frame / truss arrangement... the traditional solutions where a member is to be subjected to bending loads? This doesn't move us on from the fact that a monocoque is still in essence a tube which you dismissed as an incorrect structural usage.

Originally posted by rms

Shouldn't engineering be about the pursuit of excellence and not what we can get away with or how cheap we can make it ?

In an ideal world engineers would always pursue excellence and have no consideration for how cheap something can be made. In reality - are Ford or GM or Nissan etc going to incorporate a masterpiece of engineering design that costs them $50 a unit when they can buy in something that performs exactly the same function but costs 50 cents per unit?

[McGuire]

Originally posted by FrankB


What is unusual about someone who wants "to want to load a tube in bending"?

http://www.prosiectm...gbritbridge.jpg

http://www.gutenberg.../bridges_17.png

http://www.britannic...ebirt001p4.html

http://www.excelsail...s_and_Flags.jpg

But here we are concerned with bolts and screws, not bridges or flagpoles. Bolts and screws are for shear and tensile loads. We do not want a bending load on a bolt or screw. Bolts are often used in bridge construction. However, if we place the bolts in the bridge under a bending load, the bridge will soon fall down.

[McGuire]

Originally posted by gbaker
Ringnuts are used in critical applications where galling is a low priority, assuming it occurs. Surgeons have implanted over 20,000 of them, for example. The primary advantage is an increase in the amount of torque required for removal. There are no load limits beyond what one would encounter in a normal fastener design.

Don't count on it. One finds few brain surgeon in racing.

Go look at a quality connecting rod. See any nuts anywhere?

[gbaker]

Originally posted by shaun979
...you do not want to even try to apply it in that area...

Right. I could not care less. Seriously, I have zero interest.

Connecting rod bolts are only loaded beyond preload 25% of the time and never see a combustion load. It ain't rocket surgery.

[gbaker]

Originally posted by McGuire


Go look at a quality connecting rod. See any nuts anywhere?

No. And I never saw wheels on a quality horse, either.

[FrankB]

Originally posted by McGuire


But here we are concerned with bolts and screws, not bridges or flagpoles. Bolts and screws are for shear and tensile loads. We do not want a bending load on a bolt or screw. Bolts are often used in bridge construction. However, if we place the bolts in the bridge under a bending load, the bridge will soon fall down.

Agreed. I recognise that this thread is about hollowed bolts, and that my discussion with rms has gone OT. I haven't advocated imposing bending loads on bolts or screws. I picked up on rms's apparent surprise that anyone would consider using a tube to carry bending moments.

You want to load a bolt (or tube) in bending ???????????????????????

[McGuire]

Originally posted by gbaker
No. And I never saw wheels on a quality horse, either.

Oh, I get it. I am sorta slow (not being a brain surgeon and all) but to you the current orthodoxy in connecting rod fasteners is backward technology. The wheel vs. the horse, etc. and so on. Please explain how your nuts are superior or even equal to current practice for this application. Personally, I don't see it but I can keep an open mind.

[McGuire]

Originally posted by gbaker
Right. I could not care less. Seriously, I have zero interest.

Connecting rod bolts are only loaded beyond preload 25% of the time and never see a combustion load. It ain't rocket surgery.

Connecting rods are among the most critical applications of threaded fasteners in an automotive engine, if not the entire vehicle. But since all that is beneath you I doubt if you would be interested. Sorry to bother you.

[rms]

You do not advocate placing bolts under bending loads, yet for a hollowed bolt that is essentially a tube it is OK!

[FrankB]

Originally posted by rms
You do not advocate placing bolts under bending loads, yet for a hollowed bolt that is essentially a tube it is OK!

Which of my posts have referred to a hollowed bolt under a bending load being OK?

Your earlier post - which I may have misunderstood - seemed to be expressing surprise that someone was contemplating putting bending loads onto a bolt - I share your reservations on this.

You also seemed to be expressing surprise that a tube could be considered as suitable for carrying bending loads, and I tried to show examples of where engineers have chosen to do just that and achieved a functional, economic design. If in fact your post where you said "You want to load a bolt (or tube) in bending ??????????????????????? " was referring to tubular (ie hollow) bolts and not tubes in general then I apologise for taking this thread so far OT.

[Bill Sherwood]

I prefer conrods with bolts and no nuts where possible, if only to reduce the number of things that an go wrong and to reduce the mass.

But apart from that, that's a rather clever nut you've come up with, Gregg.

[phantom II]

Quite a few around here. I was happy to report them to the moderator.

Originally posted by McGuire


See any nuts anywhere?

[LMP900]

There are many instances on a race car where bolts are loaded in bending, to a greater or lesser degree. Take a rod end joint in a clevis - the joint may well have spacers either side of the ball. Either way, there will be a degree of bending in the bolt - with long spacers there will more bending than with short spacers. In fact the only bolted junction case with zero bending under non-axial load is if both components are infinitely rigid and the fit of the bolt is perfect. There are also many cases where a component subject to significant is mounted in single-shear to the structure, with consequent bending moment - e.g. suspension rockers: OK, they are not generally held with a single bolt, but if they were, a large-diameter hollow bolt would be more efficient than a standard bolt. I don't think we should be too prissy about this.

[gbaker]

Originally posted by Bill Sherwood
I prefer conrods with bolts and no nuts where possible, if only to reduce the number of things that an go wrong and to reduce the mass.

But apart from that, that's a rather clever nut you've come up with, Gregg.

Thanks Bill, but most of the credit goes to Paul.

Whether it would help in a conrod application depends on what problems people are seeing. Increased removal torque would be beneficial if things were getting loose. That's well known. There has been some speculation that it may help if stress concentrations in the threads are causing fractures as the cantilever nature would tend to make the assembly less rigid. Would it be enough to make a difference? I have no idea.

[rms]

While subjecting bolts to bending loads, and drilling them for lightness may not be brain surgery, and may be accepted practice for some, the end result of an error can have the same fatal consequences.

It is a bit late to say 'sorry, I thought it was usual practice', after the race driver has crashed or the aircraft crashed or the bridge fell down.