Determination of Axle Weights for Load-Sharing Axle Combinations

[Jelly_Sheffield]

This is linked to my IVA post referencing a theoretical future 6x6 build... But it's a rabbit hole in its own right.

I am struggling to find any agreed calculation basis for the axle weights of "load sharing" axle pairs.

I'm specifically interested in class N1 (Light Goods) vehicles, where the IVA manual does set out a calculation method, but only for two-axle vehicles.

There's also the following wording in "The Road Vehicles (Authorised Weight) Regulations 1998" which isn't relevant to class N1, but provides the only statutory guidance I have been able to find on the matter.

"axle weight” means the sum of the weights transmitted to the road surface by all the wheels of an axle, and for the purpose of calculating axle weight the 2 axles comprised in a tandem axle and all the axles comprised in a triaxle shall be treated as one axle;

"tandem axle” means a group of 2 axles not more than 2.5m apart so linked together that the load applied to one axle is applied to the other; references to a “driving tandem axle” include a tandem axle where either or both the axles comprising the tandem axle are driven and references to a “non-driving tandem axle” are to a tandem axle where neither of the axles comprising it is driven;

How exactly one "treats two axles as one" is entirely unclear however...

• Do you give a single axle weight for the pair, referencing the attachment point of the axle bogie as the centerline?

• Do you calculate the imposed load on each axle and give the greater of the two for both?

• Do you calculate the imposed load on each axle as if the other wasn't there, and then give the greater of the two?


Even digging into the regulations for type approval, there's never any reference to standard calculation methods that I can find.

The best I can find is this document from Scania which seems to support the idea of calculating a shared axle weight based on the centerline of the shared axles.

Any ideas?

 

[E T]

• Do you give a single axle weight for the pair, referencing the attachment point of the axle bogie as the centerline?

This.

I've been in abnormal loads and heavy haulage for most of my working live and the above is how it's done.

 

[Jelly_Sheffield]

This.

I've been in abnormal loads and heavy haulage for most of my working live and the above is how it's done.

Thanks, that's lovely and simple...

It does beg the question why no one thought to write it down in any of the dozens of government guidance documents about the subject, rather than assuming that you know this though.

Follow up question, on the weight plate and plating certificate, is the tandem axle marked as just "axle 2" or "axle 2/3", or is half the calculated figure allocated to axle 2 & half to axle 3?

 

[E T]

The tandem is marked as two axles with half the weight of the bogie on each axle.
On the certificate the axle spacings are there for each axle. So not one to the centre line of the bogie.