Weak bolts

[APenNameAndThatA]

13 hours ago, old man emu said:

I missed that source of vibration. I was thinking of the propeller producing Lift longitudinally. All other things being equal, the amount of Lift is dependent on air density. What happens when a plane flies through an "air pocket"? Air density decreases; Lift decreases and the plane moves away from its steady state path. Then it flies out of the "air pocket", air becomes denser and Lift increases. 

 

Apply that thought to the propeller at the same time. It seems logical that going through the changes in air density would result in changes in the Lift (i.e. Thrust) forces it creates. Surely that must induce fore and aft vibration that expresses itself at the Boss/hub interface as rubbing. And rubbing induces heat.

Turbulence is caused by variation in air velocity, not variation in air density. It might be that that misunderstanding would be decreased if people stopped talking about air pockets.  

 

If aircraft sank when they flew into less dense air, then they would sink when they flew into thermals of rising air. Air in thermals is hotter and therefore less dense than surrounding air. 

Edited September 30, 2022 by APenNameAndThatA

[BrendAn]

2 hours ago, APenNameAndThatA said:

That is an abnormal situation. I’ll take your word for the blackness occurring because of heat, but I would have thought that any blackness would have occurred because of mechanical wear, not due to heat. 

 

The idea that two pieces of metal could be fixed to each other and move about enough against each other to cause heating just amazes me. I have never heard of such a thing. 

How can U not understand friction 

[turboplanner]

6 hours ago, BrendAn said:

How can U not understand friction 

Perhaps you could explain it again for everyone?

[Bruce Tuncks]

Not 2 bits of metal in the old Jab prop...  the prop itself is wooden covered with glass,  I'm pretty sure that it was heat that caused the blackening, there was other damage too including splitting around some of the drive-bushes. Now I wish I had taken a pic at the time.

My new Jabiru 3300 prop is a black-painted scimitar one and this has a metal hub with tight bushes.  I have not yet put a blob or 2 of movement indicator on the hub/driver intersect but I will soon.

[Thruster88]

Friction. Correct amount of friction between propeller and flange results in no movement or heat. Incorrect, low friction results in movement, heat and eventuall departure of the propeller, simples. 

[turboplanner]

25 minutes ago, Thruster88 said:

Friction. Correct amount of friction between propeller and flange results in no movement or heat. Incorrect, low friction results in movement, heat and eventuall departure of the propeller, simples. 

I would call it clamping. With correct clamping there's no movement. 

Have a look at any open semi trailers you see running down the road; the load isn't braced fore and after but the straps run over the top, clamping the load to the deck; it never moves if correctly clamped.

 

I think Bruce's black material may have been from movement with the black being the ground resin being washed out when the prop got wet.

[walrus]

1. You can buy new drive lugs from Bert Flood.

 

2. The lugs are a medium interference fit and aren't pressed in but pulled in when you tighten the extension bolts.

 

The surfaces need to be clean and dry, then apply a little duralac to the lug to prevent corrosion.

 

3. To remove the old drive lugs, use a suitable M8 machine screw and a washer and tube arrangement to pull them out from the rear, its not rocket science, There is no hammering or brute force involved.

[APenNameAndThatA]

12 hours ago, BrendAn said:

How can U not understand friction 

Well, I’m happy to be corrected. From time to time I post about mistakes that I’ve made. My view is that if a propeller hub is functioning correctly, the friction will be such that there will be no movement between the propeller and the hub and therefore no heat generated. 

 

Quick google search… “There are two main types of friction: static and kinetic, according to the journal The Physics Teacher (opens in new tab). Static friction operates between two surfaces that aren't moving relative to each other, while kinetic friction acts between objects in motion.”

 

So, what I’m saying is that with properly designed and functioning prop hubs there is static friction, and certainly not enough kinetic friction to heat up the whole hub. 

 

To loop back to what turbo said, if a prop hub is correctly designed and functioning, it will be clamped sufficiently that there is static friction and not kinetic friction. 

Edited October 1, 2022 by APenNameAndThatA

[BrendAn]

4 hours ago, walrus said:

1. You can buy new drive lugs from Bert Flood.

 

2. The lugs are a medium interference fit and aren't pressed in but pulled in when you tighten the extension bolts.

 

The surfaces need to be clean and dry, then apply a little duralac to the lug to prevent corrosion.

 

3. To remove the old drive lugs, use a suitable M8 machine screw and a washer and tube arrangement to pull them out from the rear, its not rocket science, There is no hammering or brute force involved.

So you are pressing them in and out with bolts instead of a press. No different

 

[BrendAn]

6 hours ago, turboplanner said:

Perhaps you could explain it again for everyone?

I was talking about friction between 2 materials rubbing against one another as in a prop moving against the hub flange. If there is any movement you can get friction. 

Edited October 1, 2022 by BrendAn

[old man emu]

15 hours ago, APenNameAndThatA said:

Turbulence is caused by variation in air velocity, not variation in air density. It might be that that misunderstanding would be decreased if people stopped talking about air pockets.  

 

If aircraft sank when they flew into less dense air, then they would sink when they flew into thermals of rising air. Air in thermals is hotter and therefore less dense than surrounding air. 

Well, that's got me gob-smacked. I don't even know how to reply.

[BrendAn]

6 hours ago, turboplanner said:

I would call it clamping. With correct clamping there's no movement. 

Have a look at any open semi trailers you see running down the road; the load isn't braced fore and after but the straps run over the top, clamping the load to the deck; it never moves if correctly clamped.

 

I think Bruce's black material may have been from movement with the black being the ground resin being washed out when the prop got wet.

When you transport Steel the correct procedure is to have timber dunnage to increase friction in a sudden stop. 

[turboplanner]

1 minute ago, BrendAn said:

When you transport Steel the correct procedure is to have timber dunnage to increase friction in a sudden stop. 

The timber blocks are to provide space to get the fork truck tynes under them.

Just those blocks are enough to pevent slippage when clamoed down.

If you sat the full length of steel on the timber deck,and claped it down you would have exponentially more resistance to slippage, but we don't need that much.

[BrendAn]

15 minutes ago, turboplanner said:

The timber blocks are to provide space to get the fork truck tynes under them.

Just those blocks are enough to pevent slippage when clamoed down.

If you sat the full length of steel on the timber deck,and claped it down you would have exponentially more resistance to slippage, but we don't need that much.

Nothing to with fork lifts  . I have 3 trucks that tip bar and mesh and I run lengthwise timbers to satisfy the load restraint requirements of the company they cart for.  When I cart steel bar it has to be belly wrapped and on timber.  My crane truck carts timber and that goes straight on the steel deck.   As far as timber decks go it's 2022 ,no one I know has them except maybe stock trucks.

 

 

Edited October 1, 2022 by BrendAn

[turboplanner]

53 minutes ago, BrendAn said:

Nothing to with fork lifts  . I have 3 trucks that tip bar and mesh and I run lengthwise timbers to satisfy the load restraint requirements of the company they cart for.  When I cart steel bar it has to be belly wrapped and on timber.  My crane truck carts timber and that goes straight on the steel deck.   As far as timber decks go it's 2022 ,no one I know has them except maybe stock trucks.

 

 

What's going on the truck on the right with the 4 lengths of timber?

Timber on steel deck provides the dissimilar surfaces.

[Blueadventures]

7 hours ago, walrus said:

1. You can buy new drive lugs from Bert Flood.

 

2. The lugs are a medium interference fit and aren't pressed in but pulled in when you tighten the extension bolts.

 

The surfaces need to be clean and dry, then apply a little duralac to the lug to prevent corrosion.

 

3. To remove the old drive lugs, use a suitable M8 machine screw and a washer and tube arrangement to pull them out from the rear, its not rocket science, There is no hammering or brute force involved.

The lugs are there to increase the sheer strength of the prop attachment; saves putting larger diameter (heavier bolts).  The torque tensions the prop hub to the flange and prevent sheer friction (movement) occurring.    The earlier reference to static friction in my understanding is about something that can be moved and the static friction needed to overcome it to work.  Eg Crankshaft in bearing and a specified oil and the relative ambient temp.

[BrendAn]

10 minutes ago, turboplanner said:

What's going on the truck on the right with the 4 lengths of timber?

Timber on steel deck provides the dissimilar surfaces.

Those timbers are bolted down to satisfy OneSteel load restraint rules.

Length ways because the steel is tipped off on building sites. 

[turboplanner]

56 minutes ago, BrendAn said:

Those timbers are bolted down to satisfy OneSteel load restraint rules.

Length ways because the steel is tipped off on building sites. 

Have you caught up with the new NHVR Load Restraint Guide yet? It replaces the one which has been around for about 40 years. Haven't had a good look at it.

[old man emu]

Not having done any tests myself, but referring to some published figures, the Coefficient of Friction of steel on steel ranges from 0.5 to 0.8. The CofF between wood and metal was given as 0.2 to 0.6.

 

Basically that says that there is likely to be more sliding of steel on wood that simply steel on steel.

 

Just to clear things up, the Coefficient of Friction is the ratio of the downward force generated by an object due to the acceleration due to gravity and the force required to move that object in a direction other than down.

 

Initially when you start to move one object over the surface of the other the microscopic lumps and bumps on both surfaces interlock, making it necessary to use more force to move the object you want to move. That friction is called static friction, and is the highest value you will get in your test results. Once the object you want to move gets going, the force required to keep it going is less. That's kinetic friction (kinetic = moving). I'll use this graph simply to illustrate the shape you get if you graph the instantaneous CofF  over time. Only look at the red and black lines and think of the label on the  bottom being Time.

Initially the CofF is high (static friction), then it decreases. In the example of the steel, once the steel gets moving it's easier to move it. Remember pushing a car? Similar thing.

 

 

[BrendAn]

1 hour ago, turboplanner said:

Have you caught up with the new NHVR Load Restraint Guide yet? It replaces the one which has been around for about 40 years. Haven't had a good look at it.

 arc and infrabuild/OneSteel  have their own load restraint manual and inductions which would be a higher standard than nhvr.   For example a semi trailer loaded with 28 ton of 12 mt rebar has to be able to hang vertically off a crane with no slippage of the load at all.  2500kg ratchet straps are classes as 990 kg. They are not stupid. These companies have been in the industry a long time.

 

[turboplanner]

1 hour ago, old man emu said:

Not having done any tests myself, but referring to some published figures, the Coefficient of Friction of steel on steel ranges from 0.5 to 0.8. The CofF between wood and metal was given as 0.2 to 0.6.

 

Basically that says that there is likely to be more sliding of steel on wood that simply steel on steel.

 

Just to clear things up, the Coefficient of Friction is the ratio of the downward force generated by an object due to the acceleration due to gravity and the force required to move that object in a direction other than down.

 

Initially when you start to move one object over the surface of the other the microscopic lumps and bumps on both surfaces interlock, making it necessary to use more force to move the object you want to move. That friction is called static friction, and is the highest value you will get in your test results. Once the object you want to move gets going, the force required to keep it going is less. That's kinetic friction (kinetic = moving). I'll use this graph simply to illustrate the shape you get if you graph the instantaneous CofF  over time. Only look at the red and black lines and think of the label on the  bottom being Time.

Initially the CofF is high (static friction), then it decreases. In the example of the steel, once the steel gets moving it's easier to move it. Remember pushing a car? Similar thing.

 

 

That's at 1 g, then when it's loaded, you tension (clamp) it down, and you get another set of figures preferably 0.

[Thruster88]

Should we start a new thread,  how to load a truck correctly, just asking as a former part time (harvest only) road train driver.

Edited October 1, 2022 by Thruster88

[BrendAn]

13 minutes ago, Thruster88 said:

Should we start a new thread,  how to load a truck correctly, just asking as a former part time (harvest only) road train driver.

Looks like it.

[BrendAn]

15 minutes ago, Thruster88 said:

Should we start a new thread,  how to load a truck correctly, just asking as a former part time (harvest only) road train driver.

All these threads seem to get sidetracked but does it really matter.  

[BrendAn]

20 minutes ago, Thruster88 said:

Should we start a new thread,  how to load a truck correctly, just asking as a former part time (harvest only) road train driver.

What did you drive. Doubles,. triples ,. Quads, C trains