Designing my first 7mm Kit - Cambrian Boiler Truck

[Quarryscapes]

I am very new to 7mm scale, having spent a lifetime of working in 4mm and more recently 16mm, I'm keen to expand the 32mm gauge empire. Trouble is I'm a bit stuck for a lot of what should be 'standard' dimensions. Not a single 7mm manufacturer tells you up front what the diameters of bearings, buffer shanks or such like, so until I take delivery of a costly set of bits I'm at a bit of a standstill. If anyone can provide such dimensions, please do as I don't know if Slater's are actually posting during the lockdown. 

 

Anyway, the point of this thread whilst I'm paused on designing i to show off the new wagon. It's a Cambrian Railways design, and it's quit unique. Most machinery trucks are nothing more than 1 plank wagons with lots of tie rings. This one however was designed to be low. Incredibly low in fact, the drawing states that the bottom of the axlebox keep bars should be a mere 7 5/8" from rail height - and in reality it was much lower as it wasn't built exactly to drawing, having even Deeper Axleguards!  The floor is a mere 2'9" above rail level, and the 2" thick floor planks have had to be cut away to clear the flanges of the 2'6" wheels. As it's such an interesting design I thought I'd make it my first effort. 

 

It is a mixture of 3D print and etched Nickel Silver (or will be!) and will have independent suspension on guitar string springs, mainly for the novelty factor of seeing how low it can run with a load! 

 

So here are some initial views showing progress so far and my etched insert for the axlebox to test the eyesight and patience of all who try and build the kit...

 

 

 

 

 

[5D_Stoke]

Very nice work, I particularly like the fidelity of that axlebox. And with such an obscure prototype you can be 99.99% certain it won't suddenly be produced ready-to-run!

[Quarryscapes]

6 hours ago, 5D_Stoke said:

Very nice work, I particularly like the fidelity of that axlebox. And with such an obscure prototype you can be 99.99% certain it won't suddenly be produced ready-to-run!

 

Thanks!

 

A bit more recognisable now...

 

[Quarryscapes]

Disappointment today... Now that I have specs of the wheels, the overscale flanges foul the floor. Consequently I've had to make a cutout in the foor, which leaves 0.25mm clearance above the flanges. Looks like the suspension travel is going to have to be severely limited. I've also had to move the diagonal underframe members as they too fouled the overly narrow wheelsets. 

 

 

I have also added buffers, although I still need details of sprung heads to finish them off. 

 

[Quarryscapes]

And the 3D design work is done! Now to order the 3D printed bits and convert the etched bits into artwork to be etched when they get back to work. If all goes to plan, then the brakes will be fully functional too!