Lift axles

UK PROFESSIONAL DRIVERS FORUMS THE UK PROFESSIONAL DRIVERS FORUM (INTERACTIVE)
61

Harry Monk:

Driveroneuk:
Vehicles first used from 1 June 1998 which are fitted with a lift axle must now meet the turning circle requirements both with and without all the wheels in contact with the ground.

Yes. Like I said in the first place. :wink:

You should call yourself Flash Harry :laughing: :wink:

62

newmercman:

bigdennis:
Crazyfast, a 6x4 yank with any trailer would be undriveable in the UK, trust me, I know about these things, you may get away with it in a swb Volvo, but a ‘proper’ yank tank would not be any fun at all :wink:

But according to the regs it would be deemed to meet the turning circle requirements if it’s coupled up to a euro spec semi trailer. :question: :open_mouth: :laughing: :laughing: :laughing: :lol

63

I still maintain that the distance between the hub of the front axle & the pivot point, which is the hub of the drive axle, is shorter on a tagged motor, which therefor should be able to turn in a tighter radius.

64

Driveroneuk:
I still maintain that the distance between the hub of the front axle & the pivot point, which is the hub of the drive axle, is shorter on a tagged motor, which therefor should be able to turn in a tighter radius.

The problem with artics is that the turning circle is dependent on both the combined length/wheelbase of the unit and the distance between the point of articulation and the trailer axles.Which is why a typical yank artic outfit,using a conventional unit even with a euro spec trailer would be (almost) undriveable here on general route work.But is also why a drawbar outfit of around the same overall length would’nt be.

65

newmercman:
You should call yourself Flash Harry :laughing: :wink:

Honestly, I don’t know anything, I am a steering wheel attendant and have never claimed to be anything else.

I know a few knowledgeable people, and when a question pops up on TruckNet that I don’t know the answer to then I phone them up and ask.

If they are wrong, I can’t take responsibility for that! :wink:

66

Just another confusing explanation :confused: :laughing: With a midlift the drive axle is nearer to the front trailer axle so the ‘cut in’ is less than a tag ( it follows you around better ) :cry: :cry: Does this help? :unamused: :laughing:

67

Think I’ve got it: the trailer wheels have to stay OUTSIDE the inner circle when turning sharply.
Maybe a tag can turn too sharply hence taking the trailer wheels inside the inner circle. (anybody had them going backwards?)
Not much help unless you’ve seen the diagram.

This is undoubtably a complex mathematical issue well beyond your average steering wheel attendant.
(now before anybody thinks they recognise themselves there & bites, remember its been said on TN very recently that most of us who have been savvy enough to find our way here are not typically representative of your average knuckle dragging LGV driver)

68

Driveroneuk:
I still maintain that the distance between the hub of the front axle & the pivot point, which is the hub of the drive axle, is shorter on a tagged motor, which therefor should be able to turn in a tighter radius.

This is where we agree, especially if the 5th wheel is mounted behind the drive axle centerline, the overhang, however small, will pull the trailer further forwards before it starts to turn, this would mean it wouldn’t cross the inner line, perhaps it’s the front corner of the trailer poking out of the outer circle, maybe it’s neither and we’re all wrong, except Harry, he’ just a middle man :laughing: :laughing:

69

Driveroneuk:
Maybe a tag can turn too sharply hence taking the trailer wheels inside the inner circle. (anybody had them going backwards?)

No, this isn’t relevant when we are talking about complying with turning circle requirements. Only thing which matters here is if the outfit stays between those concentric circles. To make things easier powers-that-be have introduces definite measures for artic outfits what states that outfit will comply to regulations. I think someone has already mentioned that rule here, let see


Oh, there it was :wink:

Driveroneuk:
Turning Circle
An articulated vehicle is deemed to meet the turning circle requirement if the distance from the kingpin (or front
kingpin) to the centre line of the non-steering bogie does not exceed 8.135 metres for a 2.55 metre wide vehicle.

That doesn’t say anything about axle configuration of the unit. It only says that once distance from trailers non-steering axles to kingpin is enough outfit will comply with turning circle regulations despite the axle configuration of tractor unit. Of course the combined length of the outfit must not be more than 16.5 metres.

If someone is having difficulties understanding why tractor axle configuration doesn’t matter, try thinking it so that once laden (i.e. lift axles are on the ground) pivot points are practically same on non-steering tag and mid-axle outfits. They are also same on a similar wheelbase 6x4 unit. All of these will comply the turning circle regulations. In fact, you can think all of these as a 4x2 units where drive axle is somewhere in a middle of the rear bogie. When axles are lifted up you can think tag axle unit as a short wheelbase 4x2 and mid-lift unit as a long wheelbase 4x2. It should be clear that with short wheelbase 4x2 you don’t have to drive so close to the outer circle then you have to with long wheelbase 4x2 for trailer wheels to still stay inside the inner circle. This leaves more room for trailer headboard to “peep” behind the cab hence making it too to stay inside the outer circle.

The diagram about the turning circles so you don’t have to look for it.

Wheel Nut:

© The Transport Manager’s and Operator’s Handbook
By David Lowe

70

That’s the one Kyrbo, concentric radii.

I see now the inner radius is also a minimum, so my theory in my last post above is incorrect. :blush:

71

newmercman:

Driveroneuk:
I still maintain that the distance between the hub of the front axle & the pivot point, which is the hub of the drive axle, is shorter on a tagged motor, which therefor should be able to turn in a tighter radius.

This is where we agree, especially if the 5th wheel is mounted behind the drive axle centerline, the overhang, however small, will pull the trailer further forwards before it starts to turn, this would mean it wouldn’t cross the inner line, perhaps it’s the front corner of the trailer poking out of the outer circle, maybe it’s neither and we’re all wrong, except Harry, he’ just a middle man :laughing: :laughing:

You’ve forgotten that the turning test has to be passed with the axles all in use and not just lifted.So the arguable difference,if any (doubtful), which having a tag lifted makes,would’nt be relevant anyway and considering that the purpose of a truck is’nt to run very far empty the idea of 6x2 is just plain stupid anyway as the yanks would agree.A six wheeler unit is a six wheeler unit and the only relevance as to it’s turning capabilities are it’s length/wheelbase and the spec of the semi trailer that it’s pulling.In which case a 6x4 cab over yank tractor unit won’t turn much differently,coupled up to a 45 foot euro semi,than a 6x2 euro type unit would.However that would all change in the case of a yank conventional pulling that same trailer let alone a 53 foot yank trailer. :open_mouth: .But the lift axle issue is just a red herring in the context of a loaded truck which needs it’s axles all in contact with the road surface at all times,both in regards to turning ability and especially traction.Which is why there’s that brilliant thread on here which I posted Kenworths in the uk. :wink:

72

I bet Beef is glad he asked this question shall we wake him and find out.

73

What is the weight saving between Alloy and Steel Rims? Add to this the weight of 2 extra wheels and a differential, propshaft and possibly larger brake drums. In the UK and Europe it is more critical to carry more payload.

Fuel is cheaper, the roads are generally longer and straighter and the gross weights are less in the US of A

I believe the preference for tag, mid lift, pushers, twin steers or castor steer axles is purely personal and for me tag axles reminds me of the chavs who drive noisy Nova and Corsa around our towns. They prefer them because they turn on a tanner, not a huge requisite for a lorry is it?

Unless you are on and off landfill sites or on recovery I see no need for double drive, or even twin wheels on both rear axles, remember payload :exclamation:

I used to drive a double drive Foden with a 400 Cat that could catch pigeons, it was totally useless to get in and out of most MFI store car parks.

74

Wheel Nut:
What is the weight saving between Alloy and Steel Rims? Add to this the weight of 2 extra wheels and a differential, propshaft and possibly larger brake drums. In the UK and Europe it is more critical to carry more payload.

Fuel is cheaper, the roads are generally longer and straighter and the gross weights are less in the US of A

I believe the preference for tag, mid lift, pushers, twin steers or castor steer axles is purely personal and for me tag axles reminds me of the chavs who drive noisy Nova and Corsa around our towns. They prefer them because they turn on a tanner, not a huge requisite for a lorry is it?

Unless you are on and off landfill sites or on recovery I see no need for double drive, or even twin wheels on both rear axles, remember payload :exclamation:

I used to drive a double drive Foden with a 400 Cat that could catch pigeons, it was totally useless to get in and out of most MFI store car parks.

I think that you’ve contradicted yourself there.Gross weights are still less there than even our old 38 t limit and payload is critical whatever side of the Atlantic you’re on :bulb: .They’ve also got plenty of places that they need to load and tip in which would make the average MFI car park seem spacious that’s when they do have to get off of those always arrow straight multi lane interstates,which they supposedly always use never having to use single carriageway roads very similar to any where that you’ll find here :unamused: .But with all that against them they still found that it’s possible to build a decent 6x4 unit with a decent living space and still often with better tare weights than the average Brit plastic pig 4x2 (let alone 6x2 lift axle) day cab Foden of the 1970/80’s. :open_mouth: :laughing: Which is probably why that Kenworths in the UK thread is here in all it’s reality,showing that the things had a viable payload potential,even at 32 tonnes gross,and that there’s plenty of Brit drivers from those good old days who’d agree with me. :wink: :smiley:

75

Carryfast:
and that there’s plenty of Brit drivers from those good old days who’d agree with me. :wink: :smiley:

Yes, maybe, but they are not on Truck Net are they■■?

76

Wheel Nut:

Carryfast:
and that there’s plenty of Brit drivers from those good old days who’d agree with me. :wink: :smiley:

Yes, maybe, but they are not on Truck Net are they■■?

No probably because unlike me they just can’t be bothered with trying to put across the idea that the benefits of a 6x4 truck outweigh any so called drawbacks.They’ve probaby also got bored by the continous references concerning the idea of going to all the trouble of fitting a truck with lifting gear together with 6x2 axle configurations,which they’d understand as being a pointless way to add complication to a truck,just to end up with a relatively inferior,compromised configuration at the end of it anyway in regards to doing the job of combining axle weight capacity with traction,which has probably just been forced on designers more as a reaction to our stupid fuel pricing issues,than good engineering practice.Broken record maybe but the argument is a good one.

77

Carryfast:

Wheel Nut:

Carryfast:
and that there’s plenty of Brit drivers from those good old days who’d agree with me. :wink: :smiley:

Yes, maybe, but they are not on Truck Net are they■■?

No probably because unlike me they just can’t be bothered with trying to put across the idea that the benefits of a 6x4 truck outweigh any so called drawbacks.They’ve probaby also got bored by the continous references concerning the idea of going to all the trouble of fitting a truck with lifting gear together with 6x2 axle configurations,which they’d understand as being a pointless way to add complication to a truck,just to end up with a relatively inferior,compromised configuration at the end of it anyway in regards to doing the job of combining axle weight capacity with traction,which has probably just been forced on designers more as a reaction to our stupid fuel pricing issues,than good engineering practice.Broken record maybe but the argument is a good one.

I drive a 6x4 MAN artic and we have an identical truck that is a 6x2 midlift I do landfill work and the other driver runs woodchip scrap metal plastics etc in to recyling centres etc. When work dictates i help out with moving some of this stuff . We ran together for two days last week he can carry half a ton more a load gets around half a mile more to the gallon and in one place we were which is tight can get on the weighbridge in one go where any of the 6x4s going in have to take a shunt so who in there right mind would want a 6x4 for general haulage. And our scandinavian friends do pretty well with 6x2 trucks at 60 tons and in some tricky weather

78

kr79:

Carryfast:

Wheel Nut:

Carryfast:
and that there’s plenty of Brit drivers from those good old days who’d agree with me. :wink: :smiley:

Yes, maybe, but they are not on Truck Net are they■■?

No probably because unlike me they just can’t be bothered with trying to put across the idea that the benefits of a 6x4 truck outweigh any so called drawbacks.They’ve probaby also got bored by the continous references concerning the idea of going to all the trouble of fitting a truck with lifting gear together with 6x2 axle configurations,which they’d understand as being a pointless way to add complication to a truck,just to end up with a relatively inferior,compromised configuration at the end of it anyway in regards to doing the job of combining axle weight capacity with traction,which has probably just been forced on designers more as a reaction to our stupid fuel pricing issues,than good engineering practice.Broken record maybe but the argument is a good one.

I drive a 6x4 MAN artic and we have an identical truck that is a 6x2 midlift I do landfill work and the other driver runs woodchip scrap metal plastics etc in to recyling centres etc. When work dictates i help out with moving some of this stuff . We ran together for two days last week he can carry half a ton more a load gets around half a mile more to the gallon and in one place we were which is tight can get on the weighbridge in one go where any of the 6x4s going in have to take a shunt so who in there right mind would want a 6x4 for general haulage. And our scandinavian friends do pretty well with 6x2 trucks at 60 tons and in some tricky weather

I reckon that the half a mile per gallon would be worth the advantages which you’d find that yours has in many types of conditions of the type which would have a 6x2 driver dumping the lift axle as those Scandinavian drivers would admit.We’ve had the same discussion about a year ago and their answer,like the Brit 6x2 fans,just ended up having to rely on the argument of running a 60 tonner or a 44 tonner as a 4x2 when the inevitable loss of traction happened.But having driven 6x4 and 4x2 rigids on local urban roads and in relatively small council yards and 6x2 rigids pulling drawbar trailers on trunking I never found any real differences between them in manouvreability and 6x4 and 8x4 tippers seem to be able to manage in very tight urban situations,so I can’t see why everyone seems to have so many issues with getting around with a 6x4 tractor unit versus a 6x2 :question: .But you’re right the scandinavians do manage ok in bad conditions with 6x2 at 60 tonnes but that’s mostly because they’re usually using drawbar outfits not artics at that weight and drawbar outfits are inherently better in bad conditions anyway and can probably perform as good as a 6x4 artic outfit in most conditions.But that does’nt mean that a 6x4 drawbar outfit would’nt be even better in many cases where the only way that you’d get enough traction on a 6x2 is by lifting the tag or mid lift axle which is illegal if the thing is loaded because it will put the single drive axle overweight.But on the comparison of tare weights and payloads I reckon that you’d get a surprise if you were to compare those cab over 6X4 Kenworths with either the 6x4 or the 6x2 MAN.

79

Oh my, not this again
 :smiley: Who’s the person responsible allowing Carryfast to get enough momentum this time? :laughing: :laughing: :laughing:

Carryfast:

 I can’t see why everyone seems to have so many issues with getting around with a 6x4 tractor unit versus a 6x2 :question:

:bulb: Maybe it’s because we are brainwashed? Must be some sort of government secret operation (just like this government ■■■■■■■■ also called as global warming, you remember? :wink:).

Seriously, maybe it’s because there isn’t any silver bullet when you take also economics, local regulations etc. into consideration. If you want 6x4 for a road going vehicle why not think about 6x2 tag unit with hydraulic, detachable front wheel drive? At least MAN does these and experiences I’ve heard of have been positive. This would give you four wheel drive when you need it and allows you to lift tag axle to help maneuvering and to get even more grip. It would be even better if tag axle would be steering.

Carryfast:
But that does’nt mean that a 6x4 drawbar outfit would’nt be even better in many cases where the only way that you’d get enough traction on a 6x2 is by lifting the tag or mid lift axle which is illegal if the thing is loaded because it will put the single drive axle overweight.

But if you are given a 6x2 tag axle outfit what would you do, stand still, wait for the summer and stay under legal axle weights or dump air/lift tag axle, be a criminal for some metres and get going again?

Carryfast:
But on the comparison of tare weights and payloads I reckon that you’d get a surprise if you were to compare those cab over 6X4 Kenworths with either the 6x4 or the 6x2 MAN.

We want numbers! Give us some :wink:

Just to tease you I’ll link this picture of 8x4 Trakker I saw yesterday

Why is this happening with a 8x4?

Please check also axle configuration of snowplough on last picture of this post :wink:

Sorry, I couldn’t resist throwing more fuel to the flames :unamused: :laughing: :laughing:

80

Kyrbo:
Oh my, not this again
 :smiley: Who’s the person responsible allowing Carryfast to get enough momentum this time? :laughing: :laughing: :laughing:

Carryfast:

 I can’t see why everyone seems to have so many issues with getting around with a 6x4 tractor unit versus a 6x2 :question:

:bulb: Maybe it’s because we are brainwashed? Must be some sort of government secret operation (just like this government [zb] also called as global warming, you remember? :wink:).

Seriously, maybe it’s because there isn’t any silver bullet when you take also economics, local regulations etc. into consideration. If you want 6x4 for a road going vehicle why not think about 6x2 tag unit with hydraulic, detachable front wheel drive? At least MAN does these and experiences I’ve heard of have been positive. This would give you four wheel drive when you need it and allows you to lift tag axle to help maneuvering and to get even more grip. It would be even better if tag axle would be steering.

Carryfast:
But that does’nt mean that a 6x4 drawbar outfit would’nt be even better in many cases where the only way that you’d get enough traction on a 6x2 is by lifting the tag or mid lift axle which is illegal if the thing is loaded because it will put the single drive axle overweight.

But if you are given a 6x2 tag axle outfit what would you do, stand still, wait for the summer and stay under legal axle weights or dump air/lift tag axle, be a criminal for some metres and get going again?

Carryfast:
But on the comparison of tare weights and payloads I reckon that you’d get a surprise if you were to compare those cab over 6X4 Kenworths with either the 6x4 or the 6x2 MAN.

We want numbers! Give us some :wink:

Just to tease you I’ll link this picture of 8x4 Trakker I saw yesterday

Why is this happening with a 8x4?

Please check also axle configuration of snowplough on last picture of this post :wink:

Sorry, I couldn’t resist throwing more fuel to the flames :unamused: :laughing: :laughing:

Thanks Kyrbo.As a yank truck fan and having driven plenty of 6x4 rigids,it’s just that even a year later since the previous discussion I still can’t understand the thinking behind using a lifting axle 6x2 let alone a lift axle double drive set up.Why bother with all the aggro if you’re loaded most of the time and even empty a fixed double drive should get the job done between loads. :question: But I also reckon that mixing their good old fashioned engineering with the better scandinavian ideas of big drawbars not artics would be the best of all worlds. :smiley: But if you’re given a 6x2 and it’s just a case of dumping the tag just to get it moving that’s not going to be too much of a problem.But keeping a 6x2,or even sometimes a 4x2,artic moving is another matter when conditions are’nt good enough for them and it’s in that scenario on the road,with a loaded truck,in which they won’t let you run a loaded 6x2 as a 4x2,the answer to that question would be the same as in any other case where you’re at serious risk of a big overloading offence.But in the wrong type of conditions a 4x2 will just dig itself in deeper because of the extra axle weight anyway.But regardless of conditions the 6x4 idea just seems a lot simpler in relation to the axle loadings and traction issues and engineering anyway and there does’nt seem like there’s many reasons as to why you’d need to lift one of the drive axles as the yanks have proved over the years. :question:On the subject of getting those tare weight figures for those old KW’s,the trucks in question were in use around 30 years ago so it’s a tall order but maybe there’s a way.But yank trucks were always known for their seeming impossibly low tare weights relative to their specs.Which was probably,like the regs were here at the time,a result of the relatively low gross combination weight limits and axle weight limits which they had to run at in their home market.