Author Topic: Using a weighbridge  (Read 4784 times)

Offline Lt4vette

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Using a weighbridge
« on: August 20, 2015, 07:01:01 AM »
We're about to leave on our first real trip with a new Mk4 Tvan. Nearly finished packing it and the car, and plan to take it to a weighbridge to get the essential mass info - I'm somewhat concerned about all the stuff in the Mk4's front box. I've read a couple of articles on what to measure in what order when I get to the weighbridge, but there seems to be a lot of hitching/unhitching.
So I'd like opinions on whether the following would work:
1. With the Tvan hitched:
    - weigh just the car front axle (FA)
    - drive forward and weigh the whole car (C1)
    - drive forward, and weight the whole car/Tvan combination (W)

2. Unhitch the Tvan:
   - weigh the whole car (C2)

The required measures for when the TVan is attached, are then:
Gross Combined Mass = W
Gross Vehicle Mass = C1
Total Tvan mass = W-C2
Ball weight = C1-C2
Rear Axle Load = C1-FA
Front Axle Load = FA

What I can't get is the front axle load when the Tvan is not hitched, without one more weigh, but unless it turns out to be close to the limit with the Tvan attached, I might not worry about it.
Any observations or corrections would be appreciated.
Thanks,
Russell
Tvan Murranji Mark IV
2014 Jeep Grand Cherokee

Offline thommo19

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Re: Using a weighbridge
« Reply #1 on: August 20, 2015, 09:32:19 AM »
Looks to me that you have got it covered.
I will be interested in the results and the cost of the weighbridge and the location.
Good luck
Jeff
Nissan D40
2015 Tvan Canning

Offline Alien

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Re: Using a weighbridge
« Reply #2 on: August 20, 2015, 04:50:48 PM »
We're about to leave on our first real trip with a new Mk4 Tvan. Nearly finished packing it and the car, and plan to take it to a weighbridge to get the essential mass info - I'm somewhat concerned about all the stuff in the Mk4's front box. I've read a couple of articles on what to measure in what order when I get to the weighbridge, but there seems to be a lot of hitching/unhitching.
So I'd like opinions on whether the following would work:
1. With the Tvan hitched:
    - weigh just the car front axle (FA)
    - drive forward and weigh the whole car (C1)
    - drive forward, and weight the whole car/Tvan combination (W)

2. Unhitch the Tvan:
   - weigh the whole car (C2)

The required measures for when the TVan is attached, are then:
Gross Combined Mass = W
Gross Vehicle Mass = C1
Total Tvan mass = W-C2
Ball weight = C1-C2
Rear Axle Load = C1-FA
Front Axle Load = FA

What I can't get is the front axle load when the Tvan is not hitched, without one more weigh, but unless it turns out to be close to the limit with the Tvan attached, I might not worry about it.
Any observations or corrections would be appreciated.
Thanks,
Russell
G'day Russel,
As has been said you've fairly much got it covered.
The other calculation is Van Axle Load = W-C1.

Ree the front axle with out the van...
My experience is it will gain a little weight with the van off.
I gain @100kg with the van off from memory.
(When towing I compensate by having the 3rd spare on the front of the roof rack, it allows me to use it when day tripping with no van also).
This is caused by the tow point being behind the rear axle so a slight lift of the front axle is expected.
You may be able to try the following calculations(@98% accurate as load transfers from rear axle).
Rear Axle No Van = Rear Axle Load-Ball Weight.
Front Axle No Van = C2-Rear Axle No Van.
« Last Edit: August 20, 2015, 05:40:14 PM by Alien »
Kyle & Coral.
Propulsion unit-  Land Rover Defender.
Accommodation- '06 Canning Tvan.

Offline Lt4vette

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Re: Using a weighbridge
« Reply #3 on: August 20, 2015, 07:11:52 PM »
Thanks Kyle. I hadn't thought of the Tvan axle load. Given that it is that which determines the load the Tvan can carry, it's important. (I think it is rated at 1600kg). That also implies that the van can weigh a bit more than 1600kg (1600 + tow all weight) although that may not be legal! I guess there are also chassis and drawbar issues.
On the axle weights, I assume you mean "rear axle - tow ball weight", which would only be out by the leverage from the towball to the axle, so that's probably pretty close. Your 100kg estimate will do me, so long as the front axle load with the Tvan on is more than that off the max spec.
Thanks,
Russell
Tvan Murranji Mark IV
2014 Jeep Grand Cherokee

Offline The Hueys

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Re: Using a weighbridge
« Reply #4 on: August 21, 2015, 05:34:22 AM »
The Tvan is rated at 1600kg including the ball weight, so the axle weight should be less. Weight the van axle weight hooked up to the vehicle (just run the vehicle off the weigh bridge), then drop the jockey wheel onto the weigh bridge and un-hitch the Tvan but leave the chains attached get the total weight and just drop the van back onto the coupling to drive off.
Craig Hewitson
Former Track Trailer Service & Sales Manager - 2005 to 2011
MkII Tvan behind a Mazda BT-50

Offline Lt4vette

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Re: Using a weighbridge
« Reply #5 on: August 21, 2015, 05:45:30 AM »
Thanks for clarifying that Craig.
Russell
Tvan Murranji Mark IV
2014 Jeep Grand Cherokee

Offline Lt4vette

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Re: Using a weighbridge
« Reply #6 on: August 22, 2015, 03:29:57 PM »
Hi Craig. I have just realized that the Mark 4 has a GVM of only 1500kg. This is in the TT website, and now on my rego papers. Do you know what might have changed on the Tvan to cause this?
Thanks,
Russell
Tvan Murranji Mark IV
2014 Jeep Grand Cherokee

Offline The Hueys

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Re: Using a weighbridge
« Reply #7 on: August 23, 2015, 08:39:15 AM »
I wondered if my recollection was incorrect after I typed it. The ID plate is correct, the ATM is 1500 kg. The axles themselves are rated at 1600 kg which if you take out the ball weight gives a safety margin of a few 100 kg over their rating.
Craig Hewitson
Former Track Trailer Service & Sales Manager - 2005 to 2011
MkII Tvan behind a Mazda BT-50

Offline Alien

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Re: Using a weighbridge
« Reply #8 on: August 23, 2015, 09:36:44 AM »
Looks to me that you have got it covered.
I will be interested in the results and the cost of the weighbridge and the location.
Good luck
Jeff
I have the bonus of being able to weigh at one of our local quarries(I use this bridge 6 times a night for work).
When we did our 3 week trip recently with spare fuel and water etc. I had 50Kg to spare on each of the 3 axles.
I still had lots of room to carry extra gear but had to fight the temptation.
We never fell short of needing anything and still had the ability to stay away for another week without needing to shop.
Kyle & Coral.
Propulsion unit-  Land Rover Defender.
Accommodation- '06 Canning Tvan.

Offline Lt4vette

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Re: Using a weighbridge
« Reply #9 on: September 18, 2015, 06:58:32 AM »
Just returned from our first Tvan trip - down the Darling River, bush camping all the way with the Tvan Murranji being as good or better than expected in every respect!
Before we left, I took the rig to the local tip weighbridge, and for interest, thought I'd present the results here.
The tow car is a 2014 Jeep Grand Cherokee. Full fuel tank, Tvan loaded for travel with front box holding a 47L ARB fridge, Portaloo, BBq grate, portable gas heater, and sundry camping gear. 15kg of wood in a feed bag on the rear shelf. I forgot to fill the water, and estimate it had  about 60L of water in it (only one tank - at the rear. The car has a Thumper auxiliary battery on the back floor, and 40l fridge on the folded down rear seat. Also a chainsaw, spares etc.
So, with reference to the preceding definitions:

Tvan hitched to car:
W (Gross Combined Mass)  4300kg
C1 (Gross Vehicle Mass).    3120kg (spec = 2949)
W-C2 (total Tvan Mass).     1360kg (1500)
C1-C2 (hitch weight).         180kg.   (350)
C1-FA1 (rear axle load).     1640kg (1678)
FA1 (front axle load).         1480kg. (1452)
W-C1 (Tvan axle load).      1180kg  (1600?)

With the Tvan UNhitched:
C2 ((GVM)                        2940kg.  (2949)
FA2. (Front axle).              1520kg.  (1452)
Rear axle                          1420kg.  (1678)


So, I was exceeding the GVM Substantially,and the front axle load by about 30kg when hitched. The front axle about 70kg over when unhitched.
I reduced the total weight by removing stuff, and moved the chainsaw to the Tvan front box. Filling the water tank would also have reduced the GVM. I didn't re-weigh, but "guessed" I wasn't too far off, judging by what I took out and moved around. It is good to have a set of measurements though, and has implications for longer trips - for example, I only carried on spare for the car on this trip, and plan to carry a second under the Tvan for more remote areas.
Also, being aware that we were running pretty heavy meant I was more careful even than usual on rough roads, going through dips etc.
Thanks,
Russell
Tvan Murranji Mark IV
2014 Jeep Grand Cherokee

Offline Flood

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Re: Using a weighbridge
« Reply #10 on: September 18, 2015, 10:59:50 AM »
Thanks for this very relevant and in depth report Russell.
Hope you enjoyed your maiden voyage.

Mark.
« Last Edit: September 18, 2015, 11:01:56 AM by Flood »
Mark & Tracey
2013 Hilux(2" lift on 32" maxis bighorn)
2015 Canning.

Offline Patrol Dude

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Re: Using a weighbridge
« Reply #11 on: September 24, 2015, 08:42:36 PM »
Excellent overview Rus. I suspect a upgrade to a Pootrol would fix your challenges with your GVM
Jeff & Trish
RockVegas
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Offline Lt4vette

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Re: Using a weighbridge
« Reply #12 on: September 24, 2015, 09:04:56 PM »
Another thing I got out of this exercise, is that although I have the new, bigger kitchen, I did not have a storage space problem. With the water tank full, the Tvan would still have been 80-100kg under max weight, so no weight problem there either. Which gave me the flexibility of moving stuff from the Jeep to the Tvan.
I was also impressed by the way in which the load in side the Tvan did not move around on rough roads. I carried the wood on the platform at the end of the bed, with various small items, and they always stayed in place.
Having said all that though, running near max weights on rough roads is probably not a good idea.
Thanks,
Russell
Tvan Murranji Mark IV
2014 Jeep Grand Cherokee