1:16 Pulling sled

[Grainfarmer]

The gears on the right side are needed to adjust the full-pull distance at about 5 meters...

They let the weight box chain turn slower as the axles...

[Grainfarmer]

Some small steps ahead:
the gound palte for the weight box is fixed...I guess in this "unloaded" condition I will already have to fill the tires...

[WhiteWolf McBride]

Grainy:

Why not seal the tires to the rims (CA usually is the method) and then see if you can get a very fine needle and reasonable capacity syringe, and 'inflate' the tires to a set pressure.

I've been saving my TPN bags, syringes, and a few sets of tubing (well-flushed) and the boat guys were happy to accept various bits, as they make gread variable-weight 'ballast bags' for boats, and even water reservoirs for water cannons and such.

I'd offer a few 27 guage needles, and some 10ml syringes, (new in sterile packages) but I'd bet that Customs would pinch 'em. Ask at the pharmacy, these days they are pretty good with small quantities... (if ya can get smaller than 27 guage, even better, think 32 is about the smallest)

Alternately, you'll wanna use foam-fill... easily sourced at your average R/C shop.

WhiteWolf