[TC31] Stubby Monster Truck (Temporary Name)

[2GodBDGlory]

TC31 has been disappointingly quiet, with only four WIPs so far!

Anyways, I've finally finished up some other projects, and am ready to start posting stuff for my entry, though I haven't made a ton of progress so far.

So, my initial plan was very ambitious, including a remote controlled peristaltic pump running a Lego hydraulic system to run steering in a realistic way for this type of vehicle, and a three-speed gearbox using planetary gearing to simulate the real-life automatic-style transmission. However, my ambition appears to have been too great. I spent a while trying to get a pure Lego peristaltic pump working, but in the end the only design that worked for me at all was this very bulky one from Yoshihito Isogawa, and even it didn't give me acceptable pressure:

This was rather disappointing, since I had had great success with 3D printed parts back in this topic:

Anyways, I gave up on that idea and moved to the transmission. I built a working three-speed gearbox using two sets of planetary gears inside the 56T turntables, but the friction involved ended up being very high, and adding any significant load on the output would jam up the whole gearbox, so that idea was also ruled out!

In the end, the plan is for the model to have more basic features, but in order to keep the difficulty level up, I'll be challenging myself to build everything as small as possible.

The four motors are planned to be used for:

1. 4WD with a V8 piston engine (XL motor)

2. Shifting a traditional 3-speed transmission (Servo motor)

3. Steering the four wheels through linear actuators on the axles, and with a manual DNR gearbox to engage, disengage, or reverse steering the rear wheels for different steering modes (M motor)

4. Brakes with discs mounted in a realistic position between the universal joint and the input to the differential, using small pneumatic cylinders and an autovalve (M motor)

On top of this there will be four-link suspension

So, this is as far as I've gotten so far, with one axle about done, the DNR transmission for the steering, a partially built 3-speed, and the V8

 

The DNR transmission is based on a design I came up with years ago, I believe for my 1:7 Bugatti Chiron MOC. You slide the black 12T gear through three positions, where it either engages with the tan 20T gear, nothing, or the blue 20T gear (which is rotating backwards compared to the tan one, thanks to the tan 12T gears). This will be controlling rear axle steering, and thanks to the linear actuators on the axles, the steering position will remained locked even when the transmission is in neutral.

The transmission is very rudimentary so far, and the final build will probably depend on the space I have available:

 

The front axle is fairly densely built, and is as skinny as you can build a steered axle using these wheels, planetary hubs, and an O-framed differential.

The brake just has this pneumatic cylinder pulling that curved liftarm against the disc, with a rubber track insert pressing directly against the disc. It's not going to be a particularly strong brake, I don't think, but it does have the advantage of being before the gear reduction in the planetary hubs, multiplying its effectiveness.

I'm not really sure what the bodywork will look like at this point, but once the chassis is done I should at least have a better idea what proportions I'll be dealing with.

Thanks for reading!

[Lipko]

Nice progress so far! I'm not worried about the number of WIPs so far, it's holiday season, and maybe many builders are still in prototype phase. I was busy prototyping, and so far the concept seems to be feasible, I will make a WIP thread if I have time.

Edited 16 hours ago by Lipko