review Review: GBC 25 Sweeper (42049 C model) by PV Productions

[mostlytechnic]

GBC 25 Sweeper

This is a slightly different review than normal. This is not a set review; it's an instructions review. PV Productions publishes a line of GBC instructions, made from existing Lego sets. This makes it very simple for new GBC builders, since you don't have to hunt down an array of parts via Bricklink. If you have one of the Technic sets, you have everything you need. 

Name: GBC 25 Sweeper

Set Number: uses parts from 42049, Technic Mine Loader (originally retailed for $50; currently used sets are available for $30-40 on Bricklink)

Pieces: n/a

Price: €9.95 for the instructions

Minifigs: 0

Theme: Technic, GBC

I (and my sons) love watching GBC setups. The mechanisms used are fantastic and just fun to watch. I've seen the massive discussion threads in the Technic forum here recreating Akiyuki and other GBC designs. One drawback is the need to assemble an array of pieces, and there's often the need for rare pieces (like the chrome silver reflector dish that's beloved in GBC setups and so sells for multiple dollars EACH). PV Productions publishes a line of GBC instructions, where each design is a "C model" of an existing Technic set. As long as you have that set, you have all the pieces you need to build the GBC (except for the balls, which PV Productions also sells compatible, non-Lego balls). 

I bought a couple instruction sets to convert Technic sets I own into GBC modules. I did not buy the PV Productions balls - I didn't want to pay international shipping. After some googling for alternatives, I saw recommendations for 9/16" Delrin bearings. I ordered a bag of 100 of them on Amazon for $11.25 shipped.

The Instructions

PV Productions provides their instructions as downloadable PDF files. They are designed to be printable, but that would be costly, since they have the solid light blue backgrounds like many Lego sets do. Instead, you can easily use a computer or tablet to view it electronically. The files are password protected and have your account information (email, purchase date) across the bottom of each page to prevent piracy. Given that, I don't know why they restrict you to 3 downloads of each file. It seems like an unnecessary complication to the process and would cause extra customer support issues to arise. 

The instructions are reasonably easy to follow. The image quality is slightly less than Lego and occasionally the steps are difficult. It's obvious that they're generated by computer rather than hand-curated. Some steps aren't turned the best way to view the connections being made, and some steps would be easier to do in a different order. None are TOO difficult, so it's not too much of an issue. It is definitely a significant step up in difficulty though - not for small kids or someone who hasn't done much Technic building. Personally, I liked it. I'm a fan of the older instructions that added more pieces at once and were more complex. The current instruction style feels over-simplified to me. 

The GBC

This GBC is designed to look like a trailer. There are wheels and a tow point at the front. However, it's not really usable as a trailer. The wheels are attached to pins, not axles, so they don't roll easily. That could be modified if you wanted; there's axles left over. And when you are operating it, there's a tool to lock the wheel in place (it's the assembly with the dark grey axle connector just above and to the right of the tire in this photo. The light grey axle goes through the pinhole in the wheel and into the frame of the GBC to keep it from rolling) There's also a few spots that feel like part usage just to use up pieces - such as the "light" made of a stack of clear studs on the upper edge. 

PV Productions also followed the Technic standard of including a piston engine in the set. In this case it's a tiny single cylinder design, but it works. It is pretty fragile and fiddly during the build process though. 

 

At the front, there is this axle with a pair of light grey 3L perpendicular connectors on it. It can rotate, flipping the connectors up. The only purpose I see is that adjusts the angle of the GBC by the tiniest of amounts. 

The feed tray for the balls is connected by this single point. That does make it wobble around, but that also is part of how it works. I have a feeling that if it was more rigidly attached, you'd have more ball feeding issues. 

The right-side tire is held out from the machine by this red bush. That is because it'd rub on he yellow liftarm if it wasn't out so far. That does make it feel a little unstable though. Since you can't really roll the unit around anyway, I removed that red bush on my setup to make it a bit more compact and stable. 

The Video

This GBC runs very smoothly most of the time. If you don't put enough balls in, it does sometimes mis-feed and the ball not drop under the "antenna" piece. With 5 or so balls, it runs great. The manual does walk you though how to get the timing right of the lifting mechanism, but I found that if you just position them as shown in each step of assembly, it comes out working right. If you weren't paying that much attention to detail, you just need to remove the black gears, rotate each tan gear correctly, and put the black gears back on. The video also demonstrates the other party trick of the set. If you rotate the exhaust piece at the top of the path, the balls fall straight ahead, making it able to feed into a different GBC instead of returning them. 

The Conclusion

This is a great introductory GBC set. It's easy to get the parts for, since it's all from one set. It runs well, and is a nice level of challenge to assemble. I think it makes a nice display on its own, but there's also room to modify it if you want. You could make it longer, improve the return ramp, etc, and that's part of the fun of GBC. The price seems reasonable on it's own, but when I look at the other, much larger, GBC designs that they sell, in comparison it feels a touch overpriced. This small set was ten euros, but instructions for much larger models are 13 to 25 euros. Given how much work must go into designing and then digitally modeling each set, none of it seems unreasonable. 

Now time for me to go work on the GBC 14 Strandbeest, built from the 42054 Tractor set... 

[Johnny1360]

I think that making GBC sets from existing sets is a great idea, especially for a beginner like me and seeing this review makes me want to try it out. Thanks for this insightful review, one question though, are the balls the same ones that usually come with a LEGO ball shooter, I did see that you mentioned using bearing balls, just wondering if I can use what I already have. 

I do want to try some of these out I am just afraid I will like them too much. 

[mostlytechnic]

24 minutes ago, Johnny1360 said:

I think that making GBC sets from existing sets is a great idea, especially for a beginner like me and seeing this review makes me want to try it out. Thanks for this insightful review, one question though, are the balls the same ones that usually come with a LEGO ball shooter, I did see that you mentioned using bearing balls, just wondering if I can use what I already have. 

I do want to try some of these out I am just afraid I will like them too much. 

No, the shooter balls are a different size. GBC is designed to use the soccer or basketballs, which are slightly smaller than the shooter balls. Some of the Friends sets have started including the balls again, but for the most part, the genuine balls have to be bought from Bricklink or ebay. 

[Great Ball Pit]

Thanks for the review, I'm Matt the original designer of this MoC. I'm glad you enjoyed it!  Please visit my website and YouTube channel for more Lego GBC information and free instructions.

[mostlytechnic]

Thanks Matt - it's a pretty solid design! The more I play with it, the more it's a great intro GBC model. It's not perfect, but mostly in "B-model" type ways (aka due to part limitations). Those make good opportunities to improve it and learn how to build a reliable GBC for long-running use. And the timing aspects of this one are simple to tweak if you didn't get it all lined up when you built it.