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.  

[Armando]

François, you are a Genius! Can't wait to look the finished model but the art is showed in your daily work.  

[François]

With the differential done, I'm slowly progressing back towards the front of the car. I did the rear brakes and started the transmission housing.  It's composed of 3 parts. The tail housing,  the bell housing and the shifter housing. Having restored this car for real,  l have a ton of literature.  One of these books (the tr6 maintenance book) is full of really nice hand made 3d drawings (remember that it dates back to the pre-computer era) and some just as nice cross section views.  There's one of the transmission that I used to 3d model it. Combined with pictures from the net and measurements from my car, I was able to do a decent job of it. It's not finished but not to far either. I still have the complete shifter housing to do.  On the hydra, I made a mecanism activated by the shifter to engage the rear wheels but it didn't work well. For this one, I would like to make the actual friction clutch and engage it using the shifter instead of the clutch pedal. 

Cross section from maintenance manual 

3d model of transmission so far 

the transmission from my car after it was restored

And the rear brakes

[François]

For those of you who work with computers,  you know that eventually something will go wrong.  Well something did go wrong will my bell housing 3d model. After close to 8hrs of work, the file decided to become corrupt and could not be opened anymore. It's a very complex part to do so redoing it wasn't all that fun.  The good side of this is that it went faster the second time around and that I'm more pleased with the result. 

Bell housing V2. You will notice that the gearmotor has been placed where the starter motor normally is. Being a 1/6 scale model, I should have enough space inside the starter housing to hide the gearmotor. 

I also started work on the engine,  I did the pistons.

On a lighter note,  I went to a model show last Saturday and picked up 3 prize. I brought the Hydra Coupe and the bentley blower. Both cars were in different categories which had close to 30 entries each. The bentley won first place in the 1970 and older cars segment while the hydra won first place in a movie vehicle themed segment.  Plus, the Hydra won best of show!! It was a nice day. 

[Bainford]

Congrats on the awards. Very much deserved.

[François]

I did the crankshaft today, it went pretty well.

 I also started on the clutch.  Unlike on the hydra where I had a geared coupling hidden inside the transmission to drive the rear wheels and that didn't work well,  I intend to drive the rear wheels using a dry clutch just like on the real car.

Here's how I see it.  The green part is the flywheel and it is bolted to the crankshaft so when the engine turns,  the flywheel turns.  In red is the clutch plate and it is coupled to the main transmission shaft that drives the wheels, it can slide on the shaft and has a spring pushing it off the green plate. The blue part is the clutch pressure plate that turns freely around the clutch plate (red). The idea will be to push the blue part against the red part that will in turn push against the green thus transmitting the torque from the engine to the wheels.  I still need to figure out how to push the blue part by using the gear shifter. Aside from the 'using the gear shifter' bit, everything else is basically how a real clutch works minus a lot of fancy springs, shouldered rivets and a bunch of other stuff. I will probably make a cut-out of some sort under the bell housing so that all this stuff can be seen.