RAF david brown tug, litlle questions

[Eli-DK]

Hi, I'm a scale modeler, I really like to build airplanes and airfields.
Right now I'm building on a lancaster dammbuster.
Of course I want to build an airfield for this beautiful airplane.
I was thinking of making an David brown tug that is pulling my lanc to his lift-of place.
Poorly enough there isn't a kit (a pre-molded model), so i have to build it all by my self.
So i was looking for the sizes etc... on the internet. Poorly enough i couldn't find them. Or a vector drawing of one.
Maybe you guys can help my with my problem? Or even just the size of the wheels?

Ps. I'm from Belguim and just 16 years old, so i hope my English isn't to bad.

Thanks, Eli