Triumph Tr6, 3d printed large scale

[François]

I started this project stating that I wanted a running engine and drive train as I did on the Hydra. I would also like it to be a better design. The hydra motor broke, yes because the weak point was the crank but also because there was a lot of friction from the different rotating components.  So I'm trying to reduce this friction by using ball bearings wherever possible. I'll have then at the rear hubs, inside the differentiel, the transmission and, if possible,  the engine.  I bought a bunch of 3mm id x 7mm od x 3mm thk bearings.  With this in mind, I  3d modeled the rear drive train and differentiel today. It's not 100% finished but it's close.  Inside the differentiel,  I'll probably use the same setup as I used on the hydra which means it's not a real differentiel but rather a 90 deg gearbox.  I also finished the trailing arms,  I got them looking a lot more like the real ones now. 

Almost finished differentiel 

Trailing arm with drum and half shaft 

cross section of rear drive train with bearings in place (not final yet)

[François]

Yesterday I said that I would not be making a real differential,  well I lied. I decided to try and see if it could work. So today,  I designed the internal components that makes a differential do what it does which is to drive both wheels while permitting the wheels to rotate at different speeds.  It's a beautiful feat of engineering invented back in 1827 by a French guy named Pecqueur. 

I also redid the half shafts with more accurate universal joints along with the drive shaft. I incorporated the small bearing (which I received today and boy, are they tiny) in the front hubs.  I had to find slightly larger bearings for the differential,  I went with 4mm id instead of the 3mm id used in the hubs.

Redesigned half shafts 

Differential internal bits

Working differential (in cad at least)

 

[meechum68]

Following this, I loved your Hydra build, and this is gonna be another show stopper! 

 

[Bainford]

This is some pretty severe model building. A working rack & pinion is super cool, a front suspension on which it looks like you could actually change the brake pads is epic, but a working differential...!? That's mind blowing stuff. Very impressive Francois.

[François]

Thank you Bainford.

A miniature working differential is actually quite common in the rc world (which I am not into). The difficulty here is to keep it to scale an to not oversize everything. It's relatively easy to do since, contrary to rc cars, my models are for show only so not subject to impacts and rough handling.