Heavy Duty Vehicles

"so, the increase in number will help to increase the load carrying capacity"

Yes

The most I've seen was a 58-wheeler on the highway from Calgary to Edmonton. [!]

There are other cute tricks as well. You may have seen "bitch and pup" combos in which the secondary trailer has an unusually long tongue. Supposedly this spaces out the load concentrations so that the deflection waves they generate do not reinforce each other.

I'm guessing that you are referring to what we call 'truck and dog'.

The reason they have a long drawbar is so that the front truck can tip it's load without unhooking. If you look at the drawbar construction, you will see that it is made of box section that is in a diamond configuration. This allows the product to run off the drawbar and not shelf.

If somebody told you another fancy story, they have probably read too many comics!

I like their version better than yours, though admittedly I don't totally know. But I haven't seen any such arrangements that would be conducive to dumping the forward load (other than side dumpers).

He's right.

Stu.

Maybe. But if so, please actually explain. Without asking travel, good grief.

Come to Oz......we'll show you how it's done!

"in which the secondary trailer has an unusually long tongue. Supposedly this spaces out the load concentrations so that the deflection waves they generate do not reinforce each other."

I like this idea. It is used by cruise ships to make a smoother trip. Buuuuut, would this only work at a specific speed?

If this were the primary objective could it not be achieved by putting the axles at different centres?

In OZ we have a lot of dirt roads that are almost always seriously corrugated. I think you may be onto something that the experts ( your peers ) should investigate.

actually the number of wheels is relevant to weight displacement, EG a semi can carry a 32 ton container within normal wheel limits yet to carry say a piece of heavy machinery for instance then the wheels have to increase in number, because the weight is not spread over the load deck and the deck itself will suffer hence extra wheels are needed to support the deck. Wheels support the deck nothing more, if the even load weight increases then it is springs and axles that increase in size.

Your not wrong there. I drove the last semi to make it north through 'Saltwater Creek' just south of Tiaro QLD on Friday night about 10.30pm. The road looked like a sceen from Titanic. What I didn't realise was that my truck would have to contend with large lumps of road being washed up besides the tonnage of water.

The thing to remember is that tarmac is an oil product and it floats. Now all our roads have floated away!

The road between Childers and Brisbane is cut in four places and we can only go as far north as Gladstone. As a part time trucky........I'm out of business! Still, there is always the CAD drafting work to do (thank God)!

Perhaps you had better go to one of the mining companies and borrow one of these??????

I spent a couple of years driving one of those.

Calculate the ground pressure on this little 'dinky'.

Someone has had to.

Stu.

Most highways are rated at a maximum Axel load, so in order to increase the carrying capacity of a vehicle you add more Axel's,here in England the norm for a truck trailer with four Axel's is front 8ton rear truck 10ton trailer 1st axle 10ton 2nd axle 10ton giving max load 38tons, so when the government increased the maximum loading to 48 tons (I think ) they actually reduced the road loading by first making the truck with three Axel's one front steering 8ton one rear steering 6 ton & rear 10tons, then three Axel's on the trailer each 8tons, so you have increased the carrying capacity whilst reducing road wear & tear, also over here with special permits you can carry loads of over 150tons or more as long as the Axel loads stay within the limits,hence we see trailers with 10 & 12 Axel's.Hope this helps.

Bazzer

"Axel" is an ice-skating maneuver. If you are talking about rotating wheel shafts, it should be "axle". Bon voyage...

Speaking as a fully paid up member of NAD (Association of Dyslexics Nationale, or what he said) I'm caused to remark both are about rotating about an axis.

Or ironically Axel Paulsen (1856-1938), Norwegian figure skater, invented the skating axle.

Well that just goes to show.............I didn't realise that ice skates had axles!!!!!!

................or, was that axels

No ice skates don't have axles - Axel had an axle

No wonder I couldn't turn those damn skates when I went ice skating...........that's why I kepy going in a strait line.......no axles???

Well I can imagine why you had no success with that. Maybe next time try for a gay lion.

Was this Axel's axle?..........or close to it?????

Owwww - gota hurt but _{(he said)} that's more like a tail shaft in the tail.

no wonder you dont put your real name

Axel load ( axle??)

Which conveniently by way of gentle physics translates into 'contact patch load'.

Look at a 100tonne "rough terrain" mobile crane suspended over only 4 axles, on giant 'Maxi' tyres, only two per axle. Forget about axle load. It's an outdated method of regulating vehicle interface with the road surface, and now most inapropriate.

Those tyres on the crane will have a contact patch of perhaps 200inches2 each. Or more.

How many 850x22 truck tyres would you need to equal that? (No. You do the math)

And then how many "axles"?

But the crane has only 4.

Interestingly the Americans have lots of '18wheelers'. That's a 'semi' with a tractor having 3axles - 1 steering; 2 wheels, and a driving bogie of 2axles - 4 wheels each. There's 10 wheels. The remainder are on the trailer; 2 axles. That's another 8 wheels.

All that is assuming that the rig is not shod with Maxi's.

Whereas we have almost none left (18 wheelers). The semis have triple axle bogies.

That's 12 wheels. And if it's a 'B Double' there's another trailer behind that with a triple axle bogie. There's another 12.

There's more B Doubles on the roads than semis. So most rigs are riding on 34 wheels minimum.

Next up is the Road Train which could have up to 6 or 7 trailers hitched together behind the tractor.

Now, back that thing up through a gateway.

Getting back to the 'dog'. The method is to tip the dog and then jackknife the dog out of the way and tip the main tray over the hitch pole, as beej says. Alternatively, tip the dog, and then the main tray and simply drag the dog over it. The dog doesn't get unhitched, ever.

Cheers,

Stu.

Hi, over here in the mother country the trend is for three axle tractor unit, the front steering with two wheels, the second steering with two wheels ( which is just in front of the third axle) & the third axle with four wheels, I don't know why but it is called a Chinese six, the trailers have three axles with super singles.

Baz,

Here that's called a 'twin steer'.

Two steerable axles. If it had three steerable axles it would be a 'triple steer'.

But that's just here.

Super singles, or maxis here, are far safer because you do notice an underinflated tyre earlier. All that rubber on the roads mainly is shed off inboard tyres.

I've pulled over many a truck to tell the driver he's got a flat or disintegrating inner tyre. You just can't see them in the mirrors. Most are really thankful.

Cheers,

Stu.

Actually, that's not quite right!

Some trucks (lorries) but mainly passenger coaches had two steer axles at the front with single wheels and one rear axle with double wheels. This is what is/was called a Chinese six because it looked back to front.

Trucks that have a steer axle at the front followed by a second steer axle and a load axle at the rear are still called 'twin steer' in the UK. However, if the second steer axle can lift, it is called a 'tag' axle!

Hi Stu,

Altough this is well off the subject!!

It doesn't look like you are affected by the floods at Woodridge, but, hope any friends and relatives are OK.

It sure is looking bad in Brisbane.......and probably worse to come.

Thanks mate.

No we're OK. On fairly high ground, and well stocked with food staples and fuel for the generator. Boat at the gate. ( Boy Scout)

Bris city is really in the shyte. Even Suncorp stadium half full with water.

This'll take a decade to repair. Finding funds will be the next challenge. Insurance Coy's have already indicated that they will only pay pertinent to the 'fine print'. Means that some who heretofore thought that they were insured, are actually not.

Bastards.

Old Beej50 is not having too good a time. Until a couple of days ago he was having to swim out through the torrent get to work and access supplies. Since bought a small boat.

My thoughts are for the folk who are still in the CBD high rise buildings with no power.

No opening windows, aircon, fridges. And with this humidity.

Why do the emergency power gensets always get put in the basement?

I really appreciate the thought from you.

Ky rang me from the Island too.

Interesting photos and videos on the " Brisbane PM News" site if anyone wants a good look.

Cheers to all,

Stu.

Well said Stuey

Except that towns out west have lost lives! Some are saying that there will be 30 confirmed deaths in Grantham alone.

The irony of this (for me) is that my home town in the UK was Grantham (Lincolnshire).

Since the big wet started, we have been marooned on our farm for 23 days straight. If I needed to get out, I rigged safety lines and floated myself across some 200meters of raging water in my divers dry bag. Unfortunately, the seals on the dry bag have perished in the heat in QLD so I ended up as wet as if I had skinny dipped it. So, the next evolution was skinny dipping, as the water is quite warm........until I was attacked mid stream by what I thought at the time was a snake but was probably an eel. The next evolution was to wait until the water level got down far enough for our 4wd artic dumper to ford the creek. The wife sat in the skip and I did the driving. This was alright until again, about mid stream the front of the dumper started to float and I had little choice but to partially tip the skip. This saved the dumper but nearly ended in divorce!

The Rubber Ducky was next but it burst a tube on a sharp branch on the maiden voyage!

As you say, we have now acquired a tinny which is a Rolls Royce means of transport.

This only solves a part of the problem though. 200meters of our drive has vanished and, of all the vehicles we have, only the quad bike can travel across our land to the gate. On the other side of the creek is about 5kms of dirt mud road!!!!!!

When you finally get to tarmac, it too has virtually vanished but, if you make it that far then you get to Childers which now has no food or fuel!

This is due to the Bruce Hwy being cut many times north and south. Wonder Woman has just got to flood proof this Hwy if Eastern Australia is to survive. It also provides a part time income for my truck driving!

Please send out for more Sham Wows!!!!

Sorry!

Should have posted the address: www.brisbanetimes.com.au

Cheers.

The old adage:"Form follows function" applies here.

More axles and wheels=less load per axle=longer life of truck and highway.

More axles,however, mean more road friction,and hence more engine power,less efficiency, however the extra load carrying capacity over the life of the vehicle more than justifies this down side.More axles also mean less concentrated load on the highways,which reduces highway maintenance.

Engineers do not add anything simply for looks.A drilled and tapped hole in an engine head,that is apparently not used, is there for a reason.Perhaps for an accessory or a lifting hook.It would be foolish from an engineering standpoint to expend labor and tooling if it was not necessary.Modern engineering has become more precise than it was many years ago,and all unnecessary dead weight has been virtually eliminated(except possibly for a few engineers).

The rule of form vs function can be applied across all fields, including nature studies,so keep this in mind as you try to figure out how things work.Look around, you will see it everywhere.

A handle on a cup,a handle on a door,a light bulb, a window,a tree. DNA...Everything must justify it's existence with a purpose specific to it's form.

Hope this helps as you exercise your curiosity in the world around you.

HTRN

The dead weight engineers are there per design. They function as counterweight for balance and provide an oppertunity for 'bit$ching'!!!!!!!

...Everything must justify it's existence with a purpose specific to it's form.

I am still looking for the reason for my sister in law.

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In Ontario and Manitoba, and most states, the simple axle load rating determines GVW. 12,000 pounds for the skinny front tire axle, and 20,000 pounds for a rear 4 tire axle or a fat tire front axle. Rear axles have to be spaced nearly 2m apart, for this full rating to apply. There are jurisdictions like MI and IN where axles can be more closely spaced. There, one finds many 4-tire axles on a simple 46 ton tractor trailer, perhaps twice as many as needed to carry the load. The dynamics of flexible roads and sub-bases has led to a variety of rules regarding the axle layout for high loading. The US Interstate standard is well reinforced concrete slabs connected in a string by rebar stubs to prevent them from rocking unduly as the load moves by. This sits on over a foot of well drained gravel. Much better at reducing flex than tar-and-chip roadways like macadam. Our city streets that are not concrete flow, leaving deep 2 foot wide trenches where tires pass, and rounded high ridges on both sides of that. Flood waters still remove concrete from roads, even though it does not float. After the 1980 Port Hope ON flood, concrete pavement piled up in parks and at the end of streets. Quite a sight.

David