[TC27] Truck-Mounted Forklift

[2GodBDGlory]

Well, I'm definitely late to the party on this one, but I don't like to let Eurobricks contests go by without an entry, so I might as well throw my hat in now! I've had an extremely busy summer, mostly away from my Lego, so now that I'm getting into a time where I'm only very busy, we'll see if I can churn out an entry for this contest!

As I mentioned in the discussion topic somewhere, I'm interested in building a truck-mounted forklift, similar to one of these: https://www.hiab.com/en-us/products/truck-mounted-forklifts

Unfortunately for me, these typically use three wheels, which is too few for legality in this contest, but I think I can make it work with two rear ones mounted side-by-side. Maybe I'll build both compliant and non-compliant variants, too!

Anyways, these forklifts have a couple interesting features in real life. For one, while they usually steer with a single rear tire, they can also steer the front two tires to a 90 degree angle, allowing the whole forklift to drive sideways, parallel to a truck it'd be unloading! Additionally, they have a sort of scissor-link in the fork mechanism that can extend the fork forward and backwards, to reach loads on the far side of the truck, I assume. So, the plan for functionality is:

• Steering, with both normal and parallel modes
• Fork tilt
• Fork lift
• Fork extension

I'd like to include some sort of drive, but in real life, I think these things are driven by hydraulic motors in each wheel, because their layout is extremely inconvenient for mechanical connections. At small-scale, I think this would become prohibitive, so I probably won't be going that route. Motorization would also be nice, but I don't expect to have a lot of internal space, so I'll have to see what it looks like once I've made more progress.

Anyways, I started with the fork mechanism, and made a two-stage lift system using framed racks (Arocs racks, in my mind), and a chain pulley system. I also figured out a scissor-type linkage that looks realistic, but figuring out a way to control it within the given space proved very challenging. Racks, linear actuators, and linkages all didn't seem like they'd work out well, so in the end I fell back on string. To me, string seems like a magical substance that can do virtually any function in virtually any space, but one that you usually ignore because it's so annoying to work with. Anyways, it did end up working quite nicely, so I've got a weird little winch reel with two outputs, one going up to pull a link down, and another going out to pull a link in (one for each direction of travel). It's a bit unorthodox, but it works and fits well. This is driven by a drivetrain from a worm gear, which can slide on a 32L axle, giving me hope of controlling this function from within the forklift's body.

Forks down

 

Forks up

 

Scissor linkage (String can be cleaned up later. Just one fork installed as a mock-up)

 

Scissor linkage extended

 

I suppose my next job is to try building some sort of frame. I'm not familiar with the proper order of operations for forklift models, so we'll see what works out! I'm also still busy, so I'm not sure when the next update will be

 

[2GodBDGlory]

Well, I guess it's time for an update! I've made a lot of progress since last time, and gotten most of the mechanical things figured out.

One thing I hadn't realized before is that the entire mast of the forklift slides forward and backward, in addition to having the forks move forward and backward on the mast. This was accomplished using two more framed racks with worm gears.

I also used a small linear actuator to tilt the mast.

Now, none of this is inherently super complicated, but the challenge is just how much relative motion there is in the model! The mast is sliding forward and backward, tilting, and extending, so to route drive through joints and sliding components to knobs at the back was very challenging. Those red 8T gears that can slide on shafts ended up being invaluable, but it was still a challenge!

The other feature I want the forklift to have is the 90 degree steering mode, so I now have some basic linkages set up to rotate the front two wheels 90 degrees inward, so with the rear wheel steered to 90 degrees, the forklift can drive sideways. Getting this hooked up to some reasonable control is probably the main mechanical thing I still need to do.

Other than that, I pretty much just need to build some bodywork and a cab, but that's honestly more intimidating to me than the mechanical stuff...

^Mast slid forwards

^Mast lifted

^90 degree steering mode

 

 

[2GodBDGlory]

[WIP discussion]

Well, it's done! I had a couple uninterrupted days home alone, which were very productive! Really the only challenging thing since the last update was building the mechanism to steer the front wheels. I knew I needed some linear motion on both sides, but it was surprisingly hard to get both sides to move equally without a bending mechanism, in my limited space. In the end, I found a mechanism using a 7L gear rack in the middle of the model, moving a transverse beam forwards and backwards, with a couple rubber bands pulling into the sideways drive mode to improve reliability. Once that was done, it became a very satisfying function to operate! Building bodywork was a little intimidating at first, because I really didn't have any idea where to start for a vehicle like this, but once I got going it fell together pretty easily.

[Finished model presentation]

 

This model was built after seeing these unusual forklifts at work around the job site. They're designed to ride on the back of trucks dropping off loads, so that there's guaranteed to be a forklift handy for unloading when you get there. Their unusual features include a mast that can slide forwards and backwards, their forks mounted on a scissor-linkage to slide forwards and backwards (for unloading both sides of a truck from just one side), and front wheels that can rotate in 90 degrees to allow the forklift to drive parallel to the truck it's unloading.

Because all the wheels are rotating so far, and because of their inconvenient locations, I decided it wasn't worth trying to include any kind of drivetrain, which drove me to build the model fully manual, which I expect was the right decision, given the small scale imposed by TC27 rules.

Functions:

• HOG rear-wheel steering
• Knob-operated front wheel 90 degree turning (Sideways drive mode)
• Knob-operated mast sliding (Forward and backward)
• Knob-operated mast lift
• Knob-operated mast tilt
• Knob-operated scissor-fork-extend mechanism
• Manual fork side-to-side sliding

Aesthetics:

I'm pretty happy with how the model turned out! I don't think it's as good as other builders could do, but I do feel like I'm improving. The colour combination seems to work nicely, and there's enough detail to keep it looking interesting. I added a license plate on the back, not because forklifts need them (at least in Canada), but because these forklifts typically have the rear plate of their host truck, because they'd obscure any license plate on the back of the truck during loading!

Here's a picture of one in its typical mounting:

Spoiler

 

Rear-wheel steering:

This steering was about as simple as could be, with a knob placed directly above the tire. It felt too easy, but I didn't feel any need to complicate it. It would have been nice to have a working wheel in the cab, but I felt I was out of space and could only do it by seriously compromising the shape of the interior.

Sideways Drive Mode:

This was a fun feature to implement! I had the two front wheels on linkages allowing them to steer inwards, pulled by two red 16L links. These were then connected to a sort of beam in the chassis, which was moved forwards and backwards by a 7L rack gear controlled by a knob. It ended up working very nicely, allowing the whole model to be driven sideways, provided that the rear wheel was steered at 90 degrees as well

Mast Sliding:

The whole mast of the forklift can be slid forwards and backwards, to allow it to compact itself for transport. To accomplish this, it was mounted on two "Arocs" racks, which were extended using worm gears connected to a knob. This function itself wasn't very complicated to make, but it caused a lot of other complications in making all the other mast functions have to be driven by extendable driveshafts using 8T sliding gears!

 

Mast Lift:

The mast was also lifted using two worm-driven "Arocs" racks, but it also included a chain pulley mechanism to make for a higher-lifting 2-stage mechanism. I realized after building it that because this style of build requires gravity to lower the forks, it would be completely unable to lift the forklift onto a truck! Thankfully, building a truck was never in the plans, so it's pretty irrelevant. (Except when gravity has a hard time overcoming friction to lower the forks, but generally it works alright)

 

Mast Tilt:

The whole mast was tilted using a small linear actuator. It was a little tricky to fit, but after that it worked smoothly! Apparently I didn't get any pictures of it tilted, but the above picture is good for showing the LA, and tilting can be seen in the video below

Scissor-Fork Extension:

The function that initially drew me to these forklifts (before discovering the mast sliding and sideways driving) was the distinctive scissor mechanism to slide the forks outward to reach loads further away! My scissor mechanism was slightly more complicated than some, and closely followed the linkage setup on real ones. After trying lots of strategies to operate it, I settled on using a small winch-type mechanism to pull the forks in, or pull the top of the linkage down to slide them out. I don't love using string, but it worked quite nicely here, and didn't require much space at all! The drive for this function was really complicated, though, going through a sliding shaft in the chassis, around a joint for the mast tilt, and then up a 32L axle up the mast, on which a worm gear could slide that ran a couple gears to finally run that string reel!

 

Manual Fork Adjustment:

The forks were mounted on axles, which allowed for the manual repositioning of the forks to lift different loads:

Anyways, I was quite pleased with how the model turned out! There was a lot of craziness with all the parts moving relative to each other, but it actually turned out to be reliable in the end! Cranking knobs for long periods of time wasn't fun, but I don't think there was any other way to do it

More images available at: https://bricksafe.com/pages/2GodBDGlory/tc27-forklift

Edited August 24, 2024 by 2GodBDGlory

[Paul B Technic]

Wow, that has come together really well.

[1gor]

That could be an ofgicial set; such flawless model...the only problem that fitting truck should be huge 

[grum64]

Excellent build and I can say that because it's just like the one that delivered 6 pallets of bricks this morning.

Edited August 13, 2024 by grum64

[dantheman12]

great model love the presentation and the realistic mechanical parts, reminds me of the things we use at work that we call walkie stackers, pretty much the same thing with all the same mechanical parts except its controlled like a pallet jack rather than driven around.