Positioning of tank & frame

[spruce]

Hi @spruce , this post was some time ago but I've been trying to use it to figure out specifics for my van.

Using the diagram and formula I put a diagram together. Have I got things correct? (Diagram at bottom)

If so the weights plate in engine bay is confusing me. Specs are as follows:

Permissible gross vehicle weight: 2430 kg

Permissible gross train weight: 3500 kg

Maximum permissible front axle: 1200 kg

Maximum permissible rear axle: 1450 kg

From manual

Kerb weight: 1370 kg  (includes 68kg for driver, 7kg luggage, all vehicle fluids including fuel tank 90% full)

No matter what figures I subtract from each other I can't get the max front / rear axle loads on plate to make sense.

If you can understand my question I'd be very grateful for any wisdom ??

View attachment 21472

Hi

Using the figures on the plate isn't enough information.

What you also need is the kerb weight of each axle. This is usually a little more difficult to obtain. The source is usually to ask the technical department of manufacturer of the vehicle, ie Fiat/Vauxhall or Mercedes with the van's chassis number. The total weight both front and rear axles take will never correlate to the van's payload.

The purpose of that diagram is to show the formula for how a load's weight is distributed to each axle depending on where the load is positioned. What you have worked out is the distribution of one tonne of weight at the 1.15m line over each axle. What you still have to work out is if the front axle for example will legally take 370kgs.  So if the manufacturer tells you the maximum permissible payload on the front axle is 1200kgs but the kerb weight of the front axle is 900kgs then you have already overloaded the front axle. If you have a helper along side you then his weight will also reduce that 300kgs by a bit more (not by his full weight as he isn't sitting directly above the front axle. If you weigh 100kgs then there is another 25kgs to account for.)

With your van the rear axle is always going to take the major portion of the cargo's weight. IMO the cargo area will start from behind the front seats rather than passenger footwell but that won't make any difference to the formula as the position of the load is between the axles.

The other consideration is the size and the orientation of the tank. It will be much easier to position a 350 liter tank in your van as the weight will be well within your payload. But positioning a 650 liter tank would be more challenging.

 

[con95a]

Hi

Using the figures on the plate isn't enough information.

What you also need is the kerb weight of each axle. This is usually a little more difficult to obtain. The source is usually to ask the technical department of manufacturer of the vehicle, ie Fiat/Vauxhall or Mercedes with the van's chassis number. The total weight both front and rear axles take will never correlate to the van's payload.

The purpose of that diagram is to show the formula for how a load's weight is distributed to each axle depending on where the load is positioned. What you have worked out is the distribution of one tonne of weight at the 1.15m line over each axle. What you still have to work out is if the front axle for example will legally take 370kgs.  So if the manufacturer tells you the maximum permissible payload on the front axle is 1200kgs but the kerb weight of the front axle is 900kgs then you have already overloaded the front axle. If you have a helper along side you then his weight will also reduce that 300kgs by a bit more (not by his full weight as he isn't sitting directly above the front axle. If you weigh 100kgs then there is another 25kgs to account for.)

With your van the rear axle is always going to take the major portion of the cargo's weight. IMO the cargo area will start from behind the front seats rather than passenger footwell but that won't make any difference to the formula as the position of the load is between the axles.

The other consideration is the size and the orientation of the tank. It will be much easier to position a 350 liter tank in your van as the weight will be well within your payload. But positioning a 650 liter tank would be more challenging.

Right now I think I understand much better, thanks! 

I couldn't find the kerb axle weights anywhere, glad to know it wasn't just me, thanks for outlining how to get that info.

I've currently got a 450/500 litre upright (2nd hand so unsure of exact size) starting about 35cm from bulkhead. It was fitted for me by a local window cleaning supplier. I'm wondering if it could have done with being further back. 

I'm contemplating a 600/650 flat/box shape tank, would this likely need to be positioned quite further back so the rear axle is taking more of the weight? 

I've attached another diagram which hopefully helps ?

 

[spruce]

Right now I think I understand much better, thanks! 

I couldn't find the kerb axle weights anywhere, glad to know it wasn't just me, thanks for outlining how to get that info.

I've currently got a 450/500 litre upright (2nd hand so unsure of exact size) starting about 35cm from bulkhead. It was fitted for me by a local window cleaning supplier. I'm wondering if it could have done with being further back. 

I'm contemplating a 600/650 flat/box shape tank, would this likely need to be positioned quite further back so the rear axle is taking more of the weight? 

I've attached another diagram which hopefully helps ?

View attachment 21473

With the 500 liter tank the major weight portion of the tank will be over the rear axle.

But you have to get those unladen axle weights to be sure.

My gut is telling me the 600/650 liter tank is probably too far back. I know this sounds strange but you also do need a reasonable portion of weight on the front axle as well as it helps with steering and grip, especially in the wet and cold weather where roads are more slippery.

 

[Davy G]

I'm not great with technical formulai, but I do have a lot of experience of driving loaded vans. My gut feeling is that the best place for driving stability for the (flat) tank would be close behind the bulkhead. Providing it's within the legal load weight parameters.

 

[Iron Giant]

I only have a 350ltr upright tank fitted in my Combo but it's about an 2" from the bulkhead at the top, if you put the tank more over the rear axle the is going to be on the floor fully loaded.

 

[con95a]

With the 500 liter tank the major weight portion of the tank will be over the rear axle.

But you have to get those unladen axle weights to be sure.

My gut is telling me the 600/650 liter tank is probably too far back. I know this sounds strange but you also do need a reasonable portion of weight on the front axle as well as it helps with steering and grip, especially in the wet and cold weather where roads are more slippery.

I'm not great with technical formulai, but I do have a lot of experience of driving loaded vans. My gut feeling is that the best place for driving stability for the (flat) tank would be close behind the bulkhead. Providing it's within the legal load weight parameters.

I only have a 350ltr upright tank fitted in my Combo but it's about an 2" from the bulkhead at the top, if you put the tank more over the rear axle the is going to be on the floor fully loaded.

Thanks for all the input ?? I think I'll have to do as advised if I do make the move for a bigger tank, take it to a local weighbridge and see where it's positioned safest. 

 

[spruce]

Thanks for all the input ?? I think I'll have to do as advised if I do make the move for a bigger tank, take it to a local weighbridge and see where it's positioned safest. 

Its going to be more difficult to find the ideal place to situate the 650 liter tank. It not only has to be positioned correctly to not overload either axle but it needs to be placed where it doesn't waste space.

On my Citroen Relay 04 plate SWB 1100 the fitters usually mounted a 650 liter Wydale upright tank length ways from the front bulkhead back. This distributed the weight well but created dead space in the cargo area behind the drivers seat.

The best place would have been across the front bulkhead but the front axle was way overloaded if positioned there.

If we take a Renault Trafic/Vauxhall Vivaro(before it become a rebadged Citroen Dispatch) 2900 a 650 liter tank could easily be mounted width ways behind the bulkhead due to the position of the front and rear axle and the center of the load.

Axle positioning to load was very apparent many years ago when I was in commercial vehicle sales. At the time there were 2 main contenders in the 7.5t market, Isuzu and Mitsubishi. The Mitsubishi boasted a slightly higher payload than the Isuzu in the lwb chassis cab version with an identical length alloy flat body on the back.

Unfortunately the Mitsubishi had its rear axle slightly further forward than Isuzu did. This is where the scaffolders used to get caught out. If 2 identical loads were put on each vehicle the Isuzu would be road legal where the Mitsubishi wouldn't be as its rear axle would be overloaded. You didn't have to be a rocket scientist to see it. When a Mitsubishi belonging to a scaffold company was seen by a police road patrol they pulled them off the road and sent them to have the axles weighed. 9 out of 10 they got done.

 

[con95a]

Its going to be more difficult to find the ideal place to situate the 650 liter tank. It not only has to be positioned correctly to not overload either axle but it needs to be placed where it doesn't waste space.

I don't know how far I'm going to get with this plan anyway, I called local Vauxhall dealership to speak to technical department. When I asked about individual kerb weights for the axles he said he doesn't know where to get that info... ??‍ after looking on the system he couldn't provide anything. (Took my reg + VIN) he said it's usually in owners manual (It's definitely not, only provides vehicle kerb weight) but suggested I call a tow bar specialist "who might be privy to that information"... shame Vauxhall aren't privy to their own specs ?

 

[spruce]

I don't know how far I'm going to get with this plan anyway, I called local Vauxhall dealership to speak to technical department. When I asked about individual kerb weights for the axles he said he doesn't know where to get that info... ??‍ after looking on the system he couldn't provide anything. (Took my reg + VIN) he said it's usually in owners manual (It's definitely not, only provides vehicle kerb weight) but suggested I call a tow bar specialist "who might be privy to that information"... shame Vauxhall aren't privy to their own specs ?

Forget the local dealerships - they are generally hopeless.

Vauxhall's head office was in Luton. You want to obtain the telephone number for their technical department.

This is the number for Customer Care Enquiries: 0800 026 0034. If they can't redirect you then at least they should be able to provide you with their telephone number.

Citroen used to have 2 technical departments, one for dealership workshops queries and support  and the other for queries by the public/owners.

 

[con95a]

Forget the local dealerships - they are generally hopeless.

Vauxhall's head office was in Luton. You want to obtain the telephone number for their technical department.

This is the number for Customer Care Enquiries: 0800 026 0034. If they can redirect you then at least they should be able to provide you with their telephone number.

I originally called Customer Care, explained what I was looking for and they just provided numbers for the local dealerships ? I'll try again, see if I can find the direct number online perhaps. Thanks again

 

[spruce]

I originally called Customer Care, explained what I was looking for and they just provided numbers for the local dealerships ? I'll try again, see if I can find the direct number online perhaps. Thanks again

I suppose another way would be to work backwards. You do need someone with a weigh bridge who can weigh axles separately.

If you have a 500 liter tank fitted already then you could empty it and all the other stuff and get the each axle weight measured with a full tank of diesel and you inside. You could get a tank weight plus frame from the supplier and work out how much of that weight is on each axle. What I'm getting at is if the measured front axle weight is 700kg and you've work out with the formula that 25kg of the tank and frame is being borne by the front axle then 700 - 25 = 675. If the maximum front axle weight on the plate is 1000kgs then the difference is 325kgs you can load the axle with. Obviously you won't want to max out the load on each axle.

 

[Iron Giant]

Not sure if @Part Timer has a 650ltr upright wyedale tank in his spare van which is a Vivaro if so he may be able to offer some help

 

[Part Timer]

Wont let me upload a photo I've uploaded before. Any way the tank is only 10" or so from the bulkhead and width ways. Leaves plenty of room for extra equipment. 

Apologies for not seeing this earlier but I try and keep out of the technical stuff as I'm bloody hopeless at it.

 

[Part Timer]

[No message]