cav551:
Oh dear. In the real world I took a loaded 4X2 unit and 13.6m Tandem for brake test and multi test last week, a couple of days before only the unit’s MOT appointment.The trailer was loaded with a stack of empty pallets each side against the headboard then three pallets each side on end. This done to shift the c of g further towards the rear while loading the unit as heavily as possible within its reduced taxation weight. Behind that were 16 approximately one tonne pallets of bagged ballast on pallets. This reached to just in front of the first trailer axle.
The RBT recorded weights as unit steer 6972, drive 11561 and the trailer as 6416 and 6486. In order to get the best possible readings for the trailer’s PMI RBT a 5t stillage of concrete was added just inside the trailer doors. To the surprise of the forklift driver this altered the trailer axle readings to 8916 and 8986. It did not increase the rearmost trailer axle to over 11t.
Since the unit was clearly slightly overweight for its MOT appointment (the ballast was wet and 16 pallets usually is OK) One pallet of ballast was removed from the front of the trailer. the unit axle weights on test now read 6846 &10650
Edit Add: As it reads I have mistakenly transposed the trailer axle weights, in each case the slightly heavier axle was the front one.
Let’s get this right you think that the 5t of stillage/s behind trailer axle 1 equates to the same effect on trailer axle weight distribution as a 15-20t excavator.Or even placing the equivalent 16t that you’ve described as being placed AHEAD of trailer axle 1.You and Franglais have made a poor attempt to re write the laws of moments, see saws and pivot points and nothing will shift the weight of that rear digger from trailer axles 2 and 3 to trailer axle 1 let alone onto the pin in that regard.
No one has said 5T is the same as 15T.
Taking moments applies in simple rigid systems. It cannot be simply applied when springs (of any kind) are included.
Assuming connected air springs on the trailer, then the same air pressure in all air springs will result in the same force passing through each of them. It really is that simple.
And the beauty of air systems is that (within limits) the load on the axles stays the same in spite of deviation in the road surface> load is not carried by any wheel standing on a hump nor is less on a wheel in a trough. This is why air damages road surfaces less. Brakes are better when all wheels have the same normal reaction too.
Mechanical springs are dependent upon deflection for load bearing. A wheel on a bump will “carry more weight” than the others on the level. There is less variation and less overload with air.
What if the axles are supported by progressive springs where the compression rate is dependent upon the deflection? (go and Google that!)
And that applies to air as well as mechanical systems.
This is, I think, the first mention you have made of weight transfer on/off the pin.
Load behind the trailer bogie will decrease the wt on the pin.
Load between the trailer bogie and the pin will impose wt on the trailer bogie and the pin.
You have, up until now,l been talking about the relative axle loadings within the rear bogie.
And you`ve been wrong.
If you want to argue about the bogie (as a whole unit) and the pin, that is totally different to anything said so far.
Can we agree which axel of a trailer is nearest the unit? Is it 1 (makes sense) or 3 (only in carryfast land)?
I’m clearly referring to the foremost trailer axle as axle 1.So tell us how either air suspension or steel can transfer pay load weight that’s placed behind it back onto it let alone onto the pin ahead of it.
Trailer axle 3 ( rearmost ) is clearly taking more load than trailer axle 1 in this case.Possibly even more than the drive axle.
Can we agree which axel of a trailer is nearest the unit? Is it 1 (makes sense) or 3 (only in carryfast land)?
I’m clearly referring to the foremost trailer axle as axle 1.So tell us how either air suspension or steel can transfer pay load weight that’s placed behind it back onto it let alone onto the pin ahead of it.
Trailer axle 3 ( rearmost ) is clearly taking more load than trailer axle 1 in this case.Possibly even more than the drive axle.
Oh Carryfast, where do we start to unravel your confusion with this one.
Let’s get a couple of things straight…
A tri-axle air suspension set-up compensates for axle weight variations as described by Franglais.
A steel spring set-up usually has a balance beam to equalise the weights. (BTW, that’s nothing to do with headlights. )
A point that you may have missed is that the fulcrum of a tri-axle trailer set-up is not at the half way point in the trailer’s length.
Whilst I agree that a weight placed behind the rearmost axle (axle #3) will reduce the weight on the pin, it will not reduce it by an equivalent amount because the fulcrum is nearer to the rear of the trailer.
Whilst I understand the general principle, somebody who is better than me at maths/physics (the average 12yo!) will be able to be quite precise about this.
It hasn’t gone unnoticed by some posters that you brought in the unrelated topic of pin-weight as obfuscation in your usual style during a discussion on axle weight compensation that you’d already lost.
cav551:
The RBT recorded weights as unit steer 6972, drive 11561 and the trailer as 6416 and 6486. In order to get the best possible readings for the trailer’s PMI RBT a 5t stillage of concrete was added just inside the trailer doors. To the surprise of the forklift driver this altered the trailer axle readings to 8916 and 8986. It did not increase the rearmost trailer axle to over 11t.
Did it do anything to the pin? i.e. the steer and drive axles? I note the increase in the trailer tandem was exactly 5000!
cav551:
Oh dear. In the real world I took a loaded 4X2 unit and 13.6m Tandem for brake test and multi test last week, a couple of days before only the unit’s MOT appointment.The trailer was loaded with a stack of empty pallets each side against the headboard then three pallets each side on end. This done to shift the c of g further towards the rear while loading the unit as heavily as possible within its reduced taxation weight. Behind that were 16 approximately one tonne pallets of bagged ballast on pallets. This reached to just in front of the first trailer axle.
The RBT recorded weights as unit steer 6972, drive 11561 and the trailer as 6416 and 6486. In order to get the best possible readings for the trailer’s PMI RBT a 5t stillage of concrete was added just inside the trailer doors. To the surprise of the forklift driver this altered the trailer axle readings to 8916 and 8986. It did not increase the rearmost trailer axle to over 11t.
Since the unit was clearly slightly overweight for its MOT appointment (the ballast was wet and 16 pallets usually is OK) One pallet of ballast was removed from the front of the trailer. the unit axle weights on test now read 6846 &10650
Edit Add: As it reads I have mistakenly transposed the trailer axle weights, in each case the slightly heavier axle was the front one.
Let’s get this right you think that the 5t of stillage/s behind trailer axle 1 equates to the same effect on trailer axle weight distribution as a 15-20t excavator.Or even placing the equivalent 16t that you’ve described as being placed AHEAD of trailer axle 1.You and Franglais have made a poor attempt to re write the laws of moments, see saws and pivot points and nothing will shift the weight of that rear digger from trailer axles 2 and 3 to trailer axle 1 let alone onto the pin in that regard.
No one has said 5T is the same as 15T.
Taking moments applies in simple rigid systems. It cannot be simply applied when springs (of any kind) are included.
Assuming connected air springs on the trailer, then the same air pressure in all air springs will result in the same force passing through each of them. It really is that simple.
And the beauty of air systems is that (within limits) the load on the axles stays the same in spite of deviation in the road surface> load is not carried by any wheel standing on a hump nor is less on a wheel in a trough. This is why air damages road surfaces less. Brakes are better when all wheels have the same normal reaction too.
Mechanical springs are dependent upon deflection for load bearing. A wheel on a bump will “carry more weight” than the others on the level. There is less variation and less overload with air.
What if the axles are supported by progressive springs where the compression rate is dependent upon the deflection? (go and Google that!)
And that applies to air as well as mechanical systems.
Back in the good old days of steel springs, I was turning left with a 40’ tandem spread axle trailer. Luckily for a silly cow in a mini I was empty and looked out of the back window just in time to stop dead. She had, as witnesses said, put two wheels on the footpath as I was into the turn. Her and her car were popped out by the 1st axle which had climbed up the back of her car. I think that’s totally different to air bags. I’ll wait for advice from CF&Co heavy vehicle engineers of distinction.
Can we agree which axel of a trailer is nearest the unit? Is it 1 (makes sense) or 3 (only in carryfast land)?
I’m clearly referring to the foremost trailer axle as axle 1.So tell us how either air suspension or steel can transfer pay load weight that’s placed behind it back onto it let alone onto the pin ahead of it.
Trailer axle 3 ( rearmost ) is clearly taking more load than trailer axle 1 in this case.Possibly even more than the drive axle.
Oh Carryfast, where do we start to unravel your confusion with this one.
Let’s get a couple of things straight…
A tri-axle air suspension set-up compensates for axle weight variations as described by Franglais.
A steel spring set-up usually has a balance beam to equalise the weights. (BTW, that’s nothing to do with headlights. )
A point that you may have missed is that the fulcrum of a tri-axle trailer set-up is not at the half way point in the trailer’s length.
Whilst I agree that a weight placed behind the rearmost axle (axle #3) will reduce the weight on the pin, it will not reduce it by an equivalent amount because the fulcrum is nearer to the rear of the trailer.
Whilst I understand the general principle, somebody who is better than me at maths/physics (the average 12yo!) will be able to be quite precise about this.
It hasn’t gone unnoticed by some posters that you brought in the unrelated topic of pin-weight as obfuscation in your usual style during a discussion on axle weight compensation that you’d already lost.
Any supposed axle weight compensation has its limits and there’s no way that it can shift the weight of an excavator that’s all behind axle 1 let alone axle 2 of a tri axle bogie.
So tell us why isn’t axle 1 going to act as a fulcrum taking weigh off the pin and placing it on trailer axles 2 and 3 ?.Bearing in mind your maths and physics looks to be even worse than mine in this case.
Lost indeed.
Ponsonby must be an amateur. Fancy buying a 4 axle trailer and loading it like this: trucknetuk.com/phpBB/downlo … &mode=view
Obviously all the weight, except the boom, is going through trailer axle 1. Probably be able to change the wheels on axle 4 without jacking them up.
Carryfast:
The trailer axle weights would also have been interesting especially 2 and 3.
Don’t you have load sharing axle groups? In this country axles are weighed as a group, eg, a tri can weigh between 20,000 and 22,500kg, depending upon the scheme under which the vehicle it opperating. Multiaxle group axle weights are never considered individually.
I take it, the radio silence from Carryfast is further proof of his utter lack of understanding and knowledge of anything pertaining to trucks and transport.
Obviously you agree with Franglais.Just put more air pressure into trailer axles 2 and 3 while dumping air from trailer axle 1 miraculously then supposedly reduces the weight applied on the road by axles 2 and 3.
Define scheme when most, if not all, of the weight of a bleedin great big heavy excavator is sitting behind trailer axle 1.How are you going to redistribute that weight equally across all 3 axles.
Bearing in mind that there is also much of the weight of a second bleedin great big heavy excavator sitting mostly on trailer axle 1.
Good luck with dumping more air from it to also shift even more of that weight onto trailer axles 2 and 3.
And back to the first CF post here.
Looking at the last line might be the clue to what is being suggested?
Talking about what is going on inside a multi axle bogie, not looking at what is happening with the pin.
As I`ve already pointed out, given similar hardware, if the air pressure is the same in all axles then the “weight” they “carry” is the same.
Looking at CF`s post > if air pressure is made higher in axle 1 then it will carry more weight than the other two axles.
Imagine it purely mechanically
If one axle has a heavy duty steel spring, and the other two axles have springs taken from the inside of a Biro pen, what will happen?
Most of the weight will go through the strong spring, and only a little through the puny little soft springs. No matter where the C of G the weight is on the trailer that is true.
So increasing the air in one axle will make the system unbalanced. Having the same air in all axles will make all axles transmit the same weight.
As Diesel Dave has said there are ways of mechanically or hydraulically equalising the load between axles, but air is normally the simplest, lightest, easiest to maintain, cheapest way to do it.
Carryfast:
I’m clearly referring to the foremost trailer axle as axle 1.So tell us how either air suspension or steel can transfer pay load weight that’s placed behind it back onto it let alone onto the pin ahead of it.
Trailer axle 3 ( rearmost ) is clearly taking more load than trailer axle 1 in this case.Possibly even more than the drive axle.
Oh Carryfast, where do we start to unravel your confusion with this one.
Let’s get a couple of things straight…
A tri-axle air suspension set-up compensates for axle weight variations as described by Franglais.
A steel spring set-up usually has a balance beam to equalise the weights. (BTW, that’s nothing to do with headlights. )
A point that you may have missed is that the fulcrum of a tri-axle trailer set-up is not at the half way point in the trailer’s length.
Whilst I agree that a weight placed behind the rearmost axle (axle #3) will reduce the weight on the pin, it will not reduce it by an equivalent amount because the fulcrum is nearer to the rear of the trailer.
Whilst I understand the general principle, somebody who is better than me at maths/physics (the average 12yo!) will be able to be quite precise about this.
It hasn’t gone unnoticed by some posters that you brought in the unrelated topic of pin-weight as obfuscation in your usual style during a discussion on axle weight compensation that you’d already lost.
Any supposed axle weight compensation has its limits and there’s no way that it can shift the weight of an excavator that’s all behind axle 1 let alone axle 2 of a tri axle bogie.
So tell us why isn’t axle 1 going to act as a fulcrum taking weigh off the pin and placing it on trailer axles 2 and 3 ?.Bearing in mind your maths and physics looks to be even worse than mine in this case.
Lost indeed.
Clearly you have no idea how air suspension works. The more you argue, the more proof you offer.
Star down under.:
Carryfast, stop moving the goalposts and admit you’re clueless.
He’s already rubbished Albert Einstein earlier in this thread Clearly he suffers from a terminal case of the Dunning-Kruger effect, which is where the least capable people believe they are in fact the most capable (ie too dense to realise they are dense).
So in the CF parallel dimension he is the opposite of clueless
Just by the by and to get away from the usual BS that the “Leatherhead One” spouts reminds me of back in the 80’s when trailers were mainly on steel suspension and Air was a lot more expensive and was not very popular with Hauliers !
Well we used to often reload out of Davidson’s Muggiemoss mill at Aberdeen and they were sticklers on axle weights even though the gross was always spot on at 37/38 ton. Well one particular day they started f -----g about running one of our Task single leaf tri axles over their axle weigher backwards and forwards backwards and forwards !!! Each time they got different readings 7 ton/8ton/9ton
The bogie was always spot on at just under 24 ton but Oh! dear me the single weights sent them up the f—g wall and in desperation they just had to admit defeat and let the outfit go ! I kid you not this is a true story ! Cheers Bewick.
dieseldave:
Oh Carryfast, where do we start to unravel your confusion with this one.
Let’s get a couple of things straight…
A tri-axle air suspension set-up compensates for axle weight variations as described by Franglais.
A steel spring set-up usually has a balance beam to equalise the weights. (BTW, that’s nothing to do with headlights. )
A point that you may have missed is that the fulcrum of a tri-axle trailer set-up is not at the half way point in the trailer’s length.
Whilst I agree that a weight placed behind the rearmost axle (axle #3) will reduce the weight on the pin, it will not reduce it by an equivalent amount because the fulcrum is nearer to the rear of the trailer.
Whilst I understand the general principle, somebody who is better than me at maths/physics (the average 12yo!) will be able to be quite precise about this.
It hasn’t gone unnoticed by some posters that you brought in the unrelated topic of pin-weight as obfuscation in your usual style during a discussion on axle weight compensation that you’d already lost.
Any supposed axle weight compensation has its limits and there’s no way that it can shift the weight of an excavator that’s all behind axle 1 let alone axle 2 of a tri axle bogie.
So tell us why isn’t axle 1 going to act as a fulcrum taking weigh off the pin and placing it on trailer axles 2 and 3 ?.Bearing in mind your maths and physics looks to be even worse than mine in this case.
Lost indeed.
Now then Carryfast, I avoid maths wherever and whenever possible, so we’ll continue to leave it out.
At no point did I say that the weight would be shifted, what I said was that it would be compensated.
Carryfast action point #1… look up dictionary definition of “compensate,” which in this case means the weight is equalised across the axles. On a tri-axle set-up, the fulcrum is the middle axle [axle #2]
As I agreed with you earlier, a weight placed behind axle #3 will have the effect of lightening the load on the pin. Separately to this, the weight will still be compensated (= equalised) across the tri-axle set up. The amount of lightening of the pin weight will NOT be equal to the weight placed behind axle #3 because the fulcrum of a tri-axle set-up is the centre axle (axle #2.)
I think that when YOU raised the unconnected issue of pin weight, this discussion then spiraled out of your understanding by your own efforts.
Carryfast action point #2… realise that since YOU introduced an unconnected idea, there are now two things going on which you have demonstrated (above) that you don’t fully understand.
I bet you never had this trouble with your bin-wagon!!
Franglais:
Ponsonby must be an amateur. Fancy buying a 4 axle trailer and loading it like this: trucknetuk.com/phpBB/downlo … &mode=view
Obviously all the weight, except the boom, is going through trailer axle 1. Probably be able to change the wheels on axle 4 without jacking them up.
Ironically it actually reinforces my point.
But they obviously could have saved a lot of length by putting most of the payload behind trailer axle 1 by your idea of truck design and weight distribution.
Air suspension can fix anything, right.
Franglais:
Ponsonby must be an amateur. Fancy buying a 4 axle trailer and loading it like this: trucknetuk.com/phpBB/downlo … &mode=view
Obviously all the weight, except the boom, is going through trailer axle 1. Probably be able to change the wheels on axle 4 without jacking them up.
Ponsonby is obviously not an amatuer, as he has used the boom as counterweight.
Franglais:
Ponsonby must be an amateur. Fancy buying a 4 axle trailer and loading it like this: trucknetuk.com/phpBB/downlo … &mode=view
Obviously all the weight, except the boom, is going through trailer axle 1. Probably be able to change the wheels on axle 4 without jacking them up.
crikey look at that CF is right that must be overweight on axle 3 of the unit and axle 1 of the trailer surely
Franglais:
Ponsonby must be an amateur. Fancy buying a 4 axle trailer and loading it like this: trucknetuk.com/phpBB/downlo … &mode=view
Obviously all the weight, except the boom, is going through trailer axle 1. Probably be able to change the wheels on axle 4 without jacking them up.
Perhaps some axles are there for redundancy in case of a failure…
Carryfast:
compensation has its limits and there’s no way that it can shift the weight of an excavator that’s all behind axle 1 let alone axle 2 of a tri axle bogie.
So tell us why isn’t axle 1 going to act as a fulcrum taking weigh off the pin and placing it on trailer axles 2 and 3 ?.Bearing in mind your maths and physics looks to be even worse than mine in this case.
Lost indeed.
The limits of compensation are when an axle bottoms out, or when it tops out. That’s it.
The pressure is the same in all the airbags, you can’t add pressure to 1 axle, again there is a rod that goes up from the middle axle to the ride height valve, if the middle axle too close to the trailer, then the valve will flow more air into the system, if the middle axle is at the correct distance from the trailer, do it’s at the correct ride height, then no air will flow as the valve is closed, if the axle is too far away from the trailer because the trailer is higher than its ride height, then the ride height valve will vent the air out of the system until lowering the trailer until it reaches the correct ride height.
)
A point that you may have missed is that the fulcrum of a tri-axle trailer set-up is not at the half way point in the trailer’s length.
Clearly he suffers from a terminal case of the Dunning-Kruger effect, which is where the least capable people believe they are in fact the most capable (ie too dense to realise they are dense).