Hector's bench

[HectorMB]

Hello everyone!

I have decided to creat a post to place all my MOCs and WIPs. I will keep the first post updated by editing it for adding MOCs (not the WIPs). I hope that you guys like it and, of course, all feedback will be more than welcome! :). 

Heavy trial truck:

Rebrickable: https://rebrickable.com/mocs/MOC-100386/HectorMB/heavy-trial-truck/#parts (the instructions are now for free; I will reimburse the cost for those that bothg them )

 

https://bricksafe.com/files/HectorMB/public/heavy-trial-truck/Heavy Trial Truck 01.mp4

https://bricksafe.com/files/HectorMB/public/heavy-trial-truck/Heavy Trial Truck 02.mp4

https://bricksafe.com/files/HectorMB/public/heavy-trial-truck/Heavy Trial truck Features.mp4

 

Dynamic automatic gearbox: It was the starting point of this MOC. Since I found them, I was very interested in the potential of the differential-based automatic gearboxes. I found that for heavy models, it was not very easy to use. In this case, I opted for doubling the gearbox to avoid any cracking when stepping up obstacles as well as increasing the resistance of the “high torque/low speed” pathway. After the two gearboxes, all the power is driven through a common central axle. After several testing, I found that the resistance should be proportional to the difference between the max and the low gearing; the bigger the difference, the bigger the resistance. The problem is that increasing the resistance, obviously, decreases the efficiency of the system… but, by now, I did not find any other solution. With this gearing, and the vehicle geometry, the truck can climb up to 42º steps.

Suspension: Although not motor-driven, this was an aspect that gave me several headaches. The starting idea was to have a suspension on which when a wheel is elevated because and obstacle, it benefits from the suspension of the opposite wheel, increasing the ground adherence. In practical terms, this means that you can rise one wheel up to 10 studs keeping all other three wheels still touching the ground. An issue with this system (and having only 2 axles) is that the body of the vehicle tends to stay tilted after overcoming obstacles. To solve that, I included an extra pair of shock absorbers that, instead of being supported in the opposite wheel, they are attached to the body of the truck.

Differential lock: Because of the geometry of the vehicle, front and rear differential locks were not indeed and option but obligatory. Indeed, the turning radius turns from 90 cm (diff lock closed) to 47cm (diff lock open). Although it is driven by a single motor, thanks to two clunch 24 gears, it is ensured that, despite a significant different backlash, both locks perform perfectly fine.

Steering: About this feature, the major challenge was to minimize as much as possible the backlash of the steering rack. I even considered including an actuator-based steering system. Unfortunately, for this model, I could not manage to make it happen. In exchange, the steering rack is designed to reduce the backlash in any direction. In addition, the truck includes a working steering wheel. 

Openable doors: In total, the model has 6 openable doors. 2 that access the pilot and co-pilot positions, 2 laterals that allow to see part of the gearboxes (and how they work in flat and step terrain), 1 rear door that access the rear differential lock and 1 last roof door that, besides the appearance, it allows an easy access to the On/Off switch.

 

And more to come!!!

 

Edited April 14, 2022 by HectorMB

[2GodBDGlory]

Congratulations on putting an automatic gearbox in there! It's such an interesting concept, and this design is actually pretty practical, but so seldom used! The rest of it looks thoughtfully engineered as well.

[HectorMB]

And this is my current WIP. For some time, I wondered how to build a mini dumper, so I decided to jump into it. The pictures above are of the second iteration (I remodelled the whole rear section). I have verified that the dumper runs fine and all the functions do whatever they should do :). I will limit the steering, the rotation of the vat (is this the correct word? Please, tell me otherwise ;)) and its tilt. 

 

 

 

 

Any feedback will be more than welcome!!! :)

15 minutes ago, 2GodBDGlory said:

Congratulations on putting an automatic gearbox in there! It's such an interesting concept, and this design is actually pretty practical, but so seldom used! The rest of it looks thoughtfully engineered as well.

Thanks! I agree that is not that frequently seen. It is also true that, with heavy models, is not easy to incorporate. 

[2GodBDGlory]

52 minutes ago, HectorMB said:

Thanks! I agree that is not that frequently seen. It is also true that, with heavy models, is not easy to incorporate. 

Yeah, it definitely is hard.

That dumper looks pretty nice too! I really like the way you integrated the portal axle housings with the bevel gear brackets, and the rotation of the bed is really neat too. Is that what you mean by the "vat"? I wouldn't call it that myself; I'd probably just call it a bed, or a dump bed, but maybe vat is a technical term I'm unaware of.

[HectorMB]

The front portal axle housing was the solution I found to be able to put in place the angular motor without increasing the height of the turntable or losing significant ground clearance. They also allow to have the same gearing than the rear axle housing, despite having a very different setup. 

 

And yes, probably "bed" is the most extended term for this kind of stuff. Thanks for the note! :).