Converted bus GVM.

2-Smiths · Veteran Member

Converted bus GVM.

Bagmaker · Senior Member

What model bus?
A quick search should show GVM, certainly would think more than 8 tonne

2-Smiths · Veteran Member

Bagmaker wrote:
What model bus?
A quick search should show GVM, certainly would think more than 8 tonne

Thanks for the response. I included the relevant figures in the original post, including stated GVM (12.5t)

The question revolves around how a motorhome conversion could "chew up" effectively 4 tonnes of payload (between the stated 7760kg Tare and 12500kg GVM).

Jaahn · Guru

2-Smiths wrote:

The question revolves around how a motorhome conversion could "chew up" effectively 4 tonnes of payload (between the stated 7760kg Tare and 12500kg GVM).

Hi smile

from my limited experience and also some looking at conversions in past times, I would not be surprised. Weight is the killer in converting busses.

Some places to look perhaps : the new engine/gearbox conversion, bigger more power, more gears, more weight ! Bigger tires and more spares. Batteries ! fuel and water and waste tanks themselves, and also the fluids in them. The chipboard cupboards, shower, beds etc. The floor. The solar panels and stuff. The bull bar, the rear rack/towbar/ box.

Check out those things and see what you get. In addition the weight figures in the "good 'ol days" were always hit and miss. Who worried about the GVM on school busses.

Good luck Jaahn

-- Edited by Jaahn on Friday 15th of June 2018 12:37:05 PM

2-Smiths · Veteran Member

Jaahn wrote:
2-Smiths wrote:

The question revolves around how a motorhome conversion could "chew up" effectively 4 tonnes of payload (between the stated 7760kg Tare and 12500kg GVM).
Hi
from my limited experience and also some looking at conversions in past times, I would not be surprised. Weight is the killer in converting busses.
Some places to look perhaps : the new engine/gearbox conversion, bigger more power, more gears, more weight ! Bigger tires and more spares. Batteries ! fuel and water and waste tanks themselves, and also the fluids in them. The chipboard cupboards, shower, beds etc. The floor. The solar panels and stuff. The bull bar, the rear rack/towbar/ box.
Check out those things and see what you get. In addition the weight figures in the "good 'ol days" were always hit and miss. Who worried about the GVM on school busses.
Good luck Jaahn

-- Edited by Jaahn on Friday 15th of June 2018 12:37:05 PM

Thanks for the response.

I hear you on the gained weight, but as per my first post, I struggle to see where 4 tonnes or so "went".

I just got off the 'phone to another bloke who has a large rig (admittedly, on another level, being a large tag-axle coach). He's taken that thing across the weighbridge numerous times since it was (properly) converted some years back. Completely full of fuel (500lt) Water (fresh 1000lt, grey 400lt), spares, tools, food and so on, it went across ~3 tonne below it's stated GVM...and that included a car-laden trailer!

If we take the original vehicle's tare at 7760. Remove the seats (At a guess around 450kg or so), we're down at ~7310kg.

Add 600lt water (so 600kg)

Add solar panels and framing (250kg?)

Add the weight of fitout (No idea...1 tonne? Maybe?)

Add a metric for the extra weight of new engine/trans. (We're talking about what would have been a 6.5lt N/A diesel plus 5-speed manual box, to a 6.5lt turbo-diesel engine and 6-speed auto), so maybe a further 250kg (being generous).

Plus fuel at 300lt/300kg

And 250kg for miscellaneous stuff (Gen Set, batteries and so on).

I'm still only at ~10t max.

Which arguably should be 2.5t shy of GVM.

Have I underestimated the weight of what goes in to a fitout?

Bagmaker · Senior Member

Mine has a GVM of 22.5 and goes about 15.8 dry. So 6+ tonne spare after the conversion.
Most dual axles have a 12+ tonne rating, DEPENDS ON THE VEHICLE!
Your relevance is basing your own veiw of the numbers, I asked for the details.
With them you can find out specifics, not with your numbers.

There are new regs coming in for 2 axle rigs this July too, check NHVR websites

Jaahn · Guru

2-Smiths wrote:

The question revolves around how a motorhome conversion could "chew up" effectively 4 tonnes of payload (between the stated 7760kg Tare and 12500kg GVM).
Have I underestimated the weight of what goes in to a fitout?

YES !!

It all depends on the details and we have none. Also we have little knowlege of the type of bus, motor etc etc.

If you look at the details of a caravan and the construction, you can appreciate the materials and the details to get that big box as light as it is.

Sorry that is all I can guess at now.

Jaahn

T1 Terry · Guru

The most common mistake in bus conversion is building the interior like a house. 4 x chipboard walls for every cupboard and they butt up to each other and now there is a double thickness for no added advantage but heaps of added weight. Cupboards with back walls rather than using the bus interior wall that is already there. Then house type walls rather than stick construction braced by the outer skin. Bathroom appliances like basin and vanity it would require two people carry in where the same thing or better can be built that requires one hand to lift. A big lead acid battery bank, 32kg per 100Ah @ 12v soon adds up.
I doubt the 38ft bus was ever 7.6 tonnes to start with, this is more the weight of a 30ft bus and that is probably where the weight came from but the chassis has been added to in the middle to blow it out to 38ft. 38ft is close to the max length you can go without requiring a tag axle to both carry the weight and to stop it bending in the middle. A full steel body with steel sheet lining inside and out is heavy, if it has a full chassis then I would expect the extension section is double chassis an additional 1/3rd the added bit in each direction and that is heavy. If the chassis hasn't been doubled in this way forget it, it will break in half as soon as it leaves the 4 lane super smooth highways.
This is the reason I limited the chassis extension on our big bus project to 36ft and all the interior is built from multipanel, a product made in Victoria and incredibly light as well as virtually combustion proof. The wall structure is 3 layers of 6mm multiplanel laminated together to make 10mm x 25mm framework and the internal walls that make the bathroom have 6mm multipanel skins while the inside bus walls are lined with Allusions coated 3ply panelling, all to minimise the weight.
We needed to stay below 10 tonne fully loaded to avoid the full shaker/brake roller/over the pit inspection every yr that heavy vehicles over 10 tonne are required to pass every yr in NSW.
Even the factory built A class big rigs have weight issues and they aren't 38ft long.

T1 Terry

PeterInSa · Guru

Re (The most common mistake in bus conversion is building the interior like a house. 4 x chipboard walls for every cupboard and they butt up to each other and now there is a double thickness for no added advantage but heaps of added weight. Cupboards with back walls rather than using the bus interior wall that is already there)

Agree, have seen Bus conversions carried out in this manner.

2-Smiths · Veteran Member

Thanks for the responses.

Peter_n_Margaret · Guru

Don't buy it.
There is insufficient load capacity to stay legal.

Anyone who EVER contemplates buying a caravan or motorhome is well advised to weigh it accurately first. Reducing the weight of a vehicle is almost impossibly expensive.

Cheers,
Peter

2-Smiths · Veteran Member

I've taken my concerns to the owner ( a week or so back), and let him know I believe the load carrying capacity is marginal (whether it is truly insufficient is debatable, but I'd rather have more than less).

He's of the view that the GVM can be increased reasonably easily, by around 10%.

I mentioned that this would likely involve engineering and a mod plate. That was about a week ago. I'm yet to hear how that went.

Not really an issue, as it's not really my problem.

If he can get it increased (by 10%, which was the figure he mentioned), we'll likely buy it, as everything else seems to stack up (including the mechanicals, which we had professionally assessed).

If not...we'll move on.

Peter_n_Margaret · Guru

That GVM increase, if done, would be by Blue Plate modification and while it would be legal for the State it was done in and for use Australia wide, it may not be legally recognised if registration were ever transferred to another State.

Cheers,
Peter

T1 Terry · Guru

Think of it this way, yes you could get it legal by increasing the GVM but it would then hang heavily on weight distribution because the front axle weight can still carry another 2 tonne as long as the tyres, brakes and axle comply, but the rear axle can only carry another 1.2 tonne even with the required tyres, brakes and axles. That is a lot of weight on a total of 6 tyres on the ground and could be a real issue on anything but the best laid black top.

T1 Terry

2-Smiths · Veteran Member

Firstly "we" won't be getting anything "legal". That is the seller's issue. If he makes it so, we "may" purchase it. If he does not, there is no issue...for us, anyway.

Secondly, the "suggested" GVM increase was 10% (of the original 12500kg). That is - unless my maths is flawed - some 1250kg. Assuming equal (or close to) weight distribution, I wouldn't imagine that there would be issues as regards individual axle ladings. That said, we would be looking closely at what - and where - we carried it. I doubt we'd go close to the (amended) GVM, nor exceed individual axle ladings.

@Peter: It would be an interesting situation if a blue mod plate was not recognised in another State. Goes to my question - asked on another forum - about the recognition of engineering testing/reports amongst different States. Something - as I understand it - may be "being worked on" as we speak. (I hope). In saying that, my default position would be to keep it registered where it is, and "perpetually travel" in it.

Can you cite an example of a situation where a vehicle was mod-plated for a re-rated GVM in one State, and that mod-plate was not recognised (and hence the vehicle could not be registered) in a second State?

Jaahn · Guru

Hi smile

Just a comment for consideration. Vehicles of that sort of weight usually get very poor fuel consumption. This may not be the biggest consideration, depending on what you intend to do. But you may be amazed at how much fuel it will use 'cruising' at reasonable speeds. You may tire of pulling in for hundreds of dollars of fuel.

People who have replied here may give some indication of their fuel consumption perhaps.

Jaahn

-- Edited by Jaahn on Wednesday 27th of June 2018 12:05:13 PM

2-Smiths · Veteran Member

Jaahn wrote:
Hi
Just a comment for consideration. Vehicles of that sort of weight usually get very poor fuel consumption. This may not be the biggest consideration, depending on what you intend to do. But you may be amazed at how much fuel it will use 'cruising' at reasonable speeds. You may tire of pulling in for hundreds of dollars of fuel.
People who have replied here may give some indication of their fuel consumption perhaps.
Jaahn

-- Edited by Jaahn on Wednesday 27th of June 2018 12:05:13 PM

As with all things in life, there are compromises to be made.

Either have a tiny rig which gets remarkable fuel economy, and which will be the envy of all and sundry ("How CAN you travel so cheaply?"), but have little to no space, little carrying capacity, and basically zero ability to free camp for extended periods.

OR

Have a larger rig, which allows more space inside, has less (or in some cases very little) of an issue in carrying whatever you wish, and can support you off-grid for reasonable periods...but pay for it in a healthy appetite for fuel.

...and of course, there are differences in the consumption of otherwise comparable (size-wise) rigs, from GM 2-strokes (thirsty), through to modern computer-controlled 4-stroke diesels (less so, and in some case not a whole lot worse than a large 4WD towing a large Van). For the record, I'm not suggesting a large bus will get fuel economy similar to an LC200 towing a 22' Van...What I am saying is that it is possible to achieve fuel economy that is not orders of magnitude worse in larger vehicles*

Perhaps the cost of fuel - much like the depreciation in the vehicle's value - could be viewed as "part of the cost of travel"? We may recover some of that extra cost, by not being tethered to higher-cost vehicle parking (such as in caravan parks).

*(Naturally, we'll only ever travel with a significant tail-wind - and down-hill - which should aid our fuel economy! ;) )