[TC17] WIP 4x4 Bulldoder Bridge

[Bluehose]

Hello, I'm a french who do lego technic since 2012 but I never completed and presented a MOC on Internet.
This contest is for me the occasion to work with a deadline and I hope to finally present something.

In the universe of Mad Max my project is a vehicule made by monting a bulldozer on a 4x4.
The model will have 4x4 driving for fast driving and removable tracks for crossing.

Such vehicule existe but I can't find a picture.

The model will have 4 PF motors including a servomotor.
The front side will have a bucket operated by two LA, and the back side will feature an removable bridge simplified from this MOC :

 

This is the first time I use a gearbox, so feel free to post recommendations.

In the previous picture, I need to engage :
in the first gear the two blue left driving rings in the same time,
in the second gear the two grey left driving rings in the same time,
in the 3th gear the two blue right driving rings in the same time,
and in the 4th gear the two grey right driving rings in the same time.

But I can't find a simple mechanism operated by a motor, for exemple in Sheepo's gearboxes the mechanism seem too complicate because its specifics specifications. 

 

Edited December 29, 2019 by Bluehose
fixing pictures

[Bluehose]

So I thank about a way to make a simple mechanism in the night, and I realised the orange selector can mesh 2 driving ring in the same time since I wanted power the gearbox with two motors.

Happily I did order some of them on Bricklink in the past, and this morning I found a solution to make a gearbox with 8 functions with only 2 orange selectors, if you power it with two motors :

I needed only 7 functions, but I planned to deploy the tracks and select the gears with the same motor which would be difficult, so I will use the 8th function to deploy the tracks.

I am a bit focused on the rigidity of the gearboxes, so after some building and rebuilding and some try with trianguled beams I included this frame into it :

Finaly there is the gearboxe, with 6 outputs in the way of the motor and two on the side.

Edited December 29, 2019 by Bluehose
fixing pictures

[Bluehose]

Yesterday I found a way to make a stepper with a servo :

Unfortunaly I thunk that if I want to make it work properly, I will be late for the contest so I looked for and made the Sariel's stepper :

apart from the LegoTechnicMastery's one, I don't know another.

[Bluehose]

Result of the evening, an half-axle which is not as weak as it seems :

[Bluehose]

Happy new year everyone !

Today I made it drive with a proper front drive, direction and suspension :

The drive is done by two PFL motor geared 1:1, so it's fast but it have not plenty of torque.

If with the final weight I have to gear it down because of the puissance lose in the gearboxe, it will be an important modification.

I uncountered many issues with my V1 receptor,  and with all motors of my 9398 from 2012 which have the inside of wires exposed which cause electrical hazard, so the test drive was not easy with each movement making the wires touch itself.

Edited January 1, 2020 by Bluehose

[Jim]

Happy new year!

Looking forward to your build!

[Didumos69]

Interesting build. Good luck with the contest!

[Bluehose]

So there is some progress :

I strungled a bit with the drive of the tracks which must bet foldable and powerfull, but now it's reliable even if it seem out of equilibre because the bridge is not here yet.

I've just got an XL so the folding will be faster by the removing of a worm gear.

 

Edited February 24, 2020 by Bluehose