Specifications:

length 34 cm  width 12 cm height 15.5 cm  tare weight: a smidgen over 1 kg, rear axle osculates, front axle fixed. The wheels are cotton reels and the tyres are cut from bicycle hand grips.
                             There is a bit of history with the design of this truck.

In the early 1970's I made some very similar for my kids, then in the 1990's I made some for my grand kids now in 2018 one of my daughters thought it would be a good idea if I made one for her grandson, my great grandson so I am back in the truck making business. When the kids have finished with it dad can use its 190 pieces for a source of nuts bolts screws firewood etc.
In the 1980's I dismantled 3 Bedford's, a TK, a A5 and a J6, reassembled them into one unit with a York trailing axle, thereby ending up with a 3 axle truck with a unladen weight of  5ooo kg and was classified as having a gross laden weight of 15.000 kgs. Therefore in the real world each kg of tare weight was certified to carry 3 kg of payload.
In the other photo you can see my great grandson Ryker trucking himself across the kitchen who  my grand-daughter tells me at the time weighed 14.9 kgs and the trucks wheels are still going around. You probably think this is useless information but using the same thinking because Ryker's truck has a unladen weight of 1 kilogram and he has had a average weight of say 14 kgs in the 6 weeks he's been riding it, each kg of tare weight has carried 14 kgs of payload. Using the same ratio of tare weight and laden weight my 3 axled Bedford would certainly had been struggling with 70 tonnes on her back.