[WIP] Mack Granite Boom Truck

[JLiu15]

With the gearbox-controlled mechanisms on my MCI D4500CT model proving to be impractical, I did not want to just abandon the gearbox design. Because of this, I decided to incorporate it into a different vehicle. I decided that a boom truck like the following would be god for a four-output distribution gearbox:

I have not seen many boom trucks in this style done in LEGO Technic. I've seen plenty of mobile cranes, knuckle boom cranes, etc, but I figured this would make for a unique build, especially as I see plenty of these here in the US. The turntable for the crane is also mounted higher up (at the same height as the roof of the cab), so that'll provide more space for mechanisms.

As of right now, the chassis consists of essentially everything to the rear of the wheelchair ramp module on my MCI D4500CT model. A difference is that both rear axles are driven, as opposed to one driven axle and one tag axle. The gearbox outputs will control the outriggers, boom rotation, boom elevation, and either boom extension or winch. There can only be two functions routed through a turntable in order to allow for unlimited rotation, so one of the boom functions will have to be manual.

Because the suspension design is identical to that of my MCI D4500CT model, this model will also serve as a test bed for the drivetrain and suspension on my MCI D4500CT model. If everything works well here, I can be pretty confident using this suspension design.

Let me know if you have any suggestions for me!

Photos:

Edited April 28, 2023 by JLiu15

[JLiu15]

UPDATE 3/1/23

I've made some progress on the digital build. I began working on the base of the rotating boom but found that the chassis is too long. In my original post's image, there is approximately an equal amount of bed length to the front and rear of the rear axles. However, my model had significantly more bed length in front of the rear axles. This was because I made the front end of the bed approximately where the front end of the gearbox is.

I've shortened the rear bed by a considerable amount and made modifications to the chassis below to have the base of the boom be moved a few studs back. I was concerned that the resulting design wouldn't be as reinforced, but it seems to be braced pretty well in all directions. The previous bed length would also mean I have to make the boom very long (comparable to the length of the boom on the 42082 Rough Terrain Crane) and I don't know if a boom of that length would be stable on a model like this. The mini linear actuators on the sides are for the outriggers. I'll have to test the outrigger mechanism physically to ensure the necessary movement and strength can be achieved before incorporating it into the digital build. I'll model most of the chassis and have the instructions made for it before beginning the physical build so I won't end up having to rebuild as much.

Let me know if you have any suggestions for me!

Photos:

[Ksen48]

What is already there makes you want to get instructions faster and assemble this model at home. Indeed, this is quite an original set. Once I had an idea to do something similar, but I wanted to use the West Star 6900 as a base, but the idea is still an idea.

Edited March 6, 2023 by Ksen48

[JLiu15]

On 3/6/2023 at 4:25 AM, Ksen48 said:

What is already there makes you want to get instructions faster and assemble this model at home. Indeed, this is quite an original set. Once I had an idea to do something similar, but I wanted to use the West Star 6900 as a base, but the idea is still an idea.

Thanks! Not sure how I will design the cab yet, but my plan is for it to be in the style of an American long-nose truck.

[JLiu15]

UPDATE 3/25/23

I got the front axle attached to the Stud.io model. Right now the model looks a little weird, but it should be better once the cab is modeled. Current piece count is 2167 - I expect the finished model to have 2000-3000 pieces.

Photos:

[JLiu15]

UPDATE 3/27/23

I've modeled the cab of the truck; I decided to do it in dark blue as I feel it complements the yellow boom well. The side fuel tanks are also in place. Below is a rendering of the Stud.io model so far. Current piece count is 2801.

The only thing I have to model now is the boom, which is its own separate module so I will probably begin building the physical model soon. The roof of the cab is connected to the Control+ hub, and can be removed along with it to change batteries. Because the roof and hub are removable, the doors do not open in order to give the cab extra support. Honestly, the model is turning out much better than my expectations. While there's certainly room for improvement with the cab design, I just love the way it turned out. I like the dark blue too, and since I got the 42154 Ford GT set recently, that set will provide a lot of the dark blue pieces I'll need.

[2ndgen]

I really really like where this is going, I have been trying to find inspiration to tear down 42108, and turn it into a boom truck, this is a perfect base idea. Love it 

[JLiu15]

UPDATE 4/8/23

The physical build is underway. I've got the heart of the chassis built, which contains most of the mechanisms. Those of you who have followed my progress on my MCI D4500CT model might see some resemblance, with the biggest difference being the frame supports for the boom above the gearbox. I was concerned that the boom base isn't reinforced as much since the frames sit slightly above the chassis to allow the worm gear mechanism for the boom rotation to sit below the frames, but the structure turned out to be pretty robust.

The outriggers are also in place. I was concerned that the outriggers would have too much sideways movement when extended, but they also turned out alright. They do move upwards slightly when extended and under load, but my plan is to just have the outriggers stabilize the truck rather than lift it off the ground. The actual legs of the outriggers (which I haven't modeled in Stud.io yet as I want to wait for the wheels to be put on first) will probably just be a locking linkage mechanism (like on the 8258 Crane Truck).

Let me know if you have any suggestions for me!

Photos:

[JLiu15]

UPDATE 4/9/23

A little more progress on the physical build. The front portion of the chassis is complete, with an opening for the front axle which will feature live axle suspension. The two liftarms protruding upwards where the cab will be located is to secure the Control+ hub which can be removed along with the roof for battery replacement.

The chassis directly above where the front axle will sit is very rigid - it was a lot more reinforced than I thought it would be. I haven't built the front axle yet, but I'm pretty confident at this point that there won't be any rigidity issues when the suspension compresses.

Let me know if you have any suggestions for me!

Photos:

[JLiu15]

UPDATE 4/17/23

I've finished the boom base including all mechanisms within it and have begun working on the cab. I'm liking this dark blue and yellow scheme and it makes for a nice contrast. Unfortunately I realized I'm still missing some parts for the cab (mostly dark blue System pieces) so I'm currently waiting for a BrickLink order to come in. I'll also have to find a few more metallic silver grille pieces as the seller I purchased from didn't have the amount I needed.

I've also cut down the chassis by about 5 studs in the rear. The previous design looked way too long, and it would also mean making a longer boom. I've made the drivetrain more efficient by placing the CV joints closer to the drive motor instead of routing them behind the rear axles. That design was simply carried over from my MCI D4500CT model as that one will also have a fake engine behind the rear wheels. Since there's no fake engine in this model, I was able to reroute the drivetrain and make it more efficient. I will probably start building the rear of the chassis once the cab is complete.

Let me know if you have any suggestions for me!

Photos:

[Jundis]

Really nice color choice!

Also the real model looks way better than the cad file ;-)

[JLiu15]

4 hours ago, Jundis said:

Really nice color choice!

Also the real model looks way better than the cad file ;-)

Thanks! Obviously the real model is still unfinished but I’m looking forward to the end result once I get the pieces I need.

[JLiu15]

UPDATE 4/19/23

I have a preliminary design for the boom modeled in Stud.io. The boom is made using the new 3x19 frames with tiles on the outside to hide the pin holes. Not sure if the boom will be too heavy, but the number of pin holes on the 3x19 frames definitely makes them much better suited for the boom than Technic panels. I was initially planning to include a second gearbox above the turntable to allow the winch to be motorized, but space was limited so I ultimately went with a manual winch. I still need to add the support frame for the boom in the back and the outrigger legs to the Stud.io model, but right now the Stud.io model is more or less what the final model will look like.

Current piece count: 3356

Photos:

[JLiu15]

UPDATE 4/20/22

I've added the outrigger legs and the boom support to the Stud.io model. Now it should have everything that the finished model will have. Current piece count is 3436. I've made another rendering of the Stud.io model - the finished model will more or less look like this:

[JLiu15]

UPDATE 4/28/23

I've completed everything except for the boom. The rear axles, rear bed, and outriggers are all in place.

While attaching the rear axles the chassis above it was bending severely. I had to go back and add reinforcement to that section. My initial chassis design in Stud.io only had one stud thickness above the rear axles to ensure the rear suspension isn't obstructed. I've increased the thickness of that section, and while there's still a negligible amount of bending, it is not too noticeable especially with the rear bed in place.

I've also tested all motorized functions and made a simple control profile that can shift the gearbox 90 degrees in both directions. All functions seem to work well and the drivetrain has a good balance of speed and torque. The outriggers extend very fast though, and in retrospect I should've used a worm gear mechanism or something but incorporating it now would mean completely stripping the chassis and rebuilding as the gearbox is buried in the heart of the model. I will probably just run the motor at 50% power for this function. Same for the boom rotation - it's not that fast but still could be slowed down slightly to look more realistic. It'll be interesting to see how all motorized functions perform once the boom is installed.

Current piece count: 3543

Photos:

[TexasEngineer454]

This is one of the coolest MOC builds I've seen!

How long/wide is the finished truck? Looks loooooooong from the side. 

[JLiu15]

Someone said that the model looked like a Mack Granite, and it is indeed pretty close so I made some modifications to the cab to actually make it a Mack Granite. It's not perfect, but it's much closer to the Mack Granite than the original design.

[2ndgen]

On 4/28/2023 at 5:06 PM, JLiu15 said:

Someone said that the model looked like a Mack Granite, and it is indeed pretty close so I made some modifications to the cab to actually make it a Mack Granite. It's not perfect, but it's much closer to the Mack Granite than the original design.

It's looking great, can't wait to see the finished design. 

[2ndgen]

On 4/29/2023 at 1:06 AM, JLiu15 said:

Someone said that the model looked like a Mack Granite, and it is indeed pretty close so I made some modifications to the cab to actually make it a Mack Granite. It's not perfect, but it's much closer to the Mack Granite than the original design.

It's looking great, can't wait to see the finished design. 

This is just the best truck ever lol. 

Edited May 1, 2023 by Milan
Removed double quoted image.

[Paul B Technic]

That looks really cool, well done.

[JLiu15]

UPDATE 5/1/23

Finished upgrading the truck to a Mack Granite. The original design was already pretty close to the Mack Granite, so all I had to do was modify some areas and order a few new parts. Since the original design was already so close to a real truck I didn't want the opportunity to go to waste.

The only part I'm not really happy with is the front fenders - they are much more rounded on the real Mack Granite. However, based on the photos I saw the fenders tended to vary between generations. I wish LEGO had a greater variety of curved System pieces.

The model is still missing the most important piece that will distinctly make it a Mack truck - the Mack bulldog emblem. I ordered the Mack bulldog piece from the 42078 Mack Anthem set, but it is part of a different order as they are pretty hard to come by now that the set is retired. For some reason this piece is not available in Stud.io.

Photos:

[JLiu15]

UPDATE 5/9/23

The model is 99.9% complete. The only things missing now are the Mack bulldog hood ornament from the 42078 set and the winch.

I tested all the functions and they work fine. I was initially concerned about the weight of the boom, and while raising the boom does cause it to lean slightly at the turntable, the model maintains its structural integrity regardless of the height the boom is raised to. In fact, even with the boom fully raised and extended, everything remains structurally sound.

While there are certainly parts I think can be improved, I'm overall satisfied with how this MOC turned out. The final piece count will be around 3529.

Photos:

[Maaboo the Witch]

Looks amazing!

[JLiu15]

15 minutes ago, Maaboo35 said:

Looks amazing!

Thanks! Not sure if I'll be going yet, but if I go to Brickworld Chicago this summer I plan to bring this MOC!

[TexasEngineer454]

Looks great! Amazing work!

How does it perform? How does the dual rear drive axle do moving the entire unit around?