@MCLegoboy:
It looks very complicated (and expensive) to make, and it’s probably a bit fragile.

Who knew LEGO made gears.

Somehow I have one 2x4 Technic brick. I have to check the sets with that part.

Never had any of those gears, but a friend of mine did...also funny how TLG recycled other parts into Technics (had a grey..."drive train"? "Steering Connector"?...the red part upper-center)...miss those wheels too..:|

@brick_r said:
"Never had any of those gears, but a friend of mine did...also funny how TLG recycled other parts into Technics (had a grey..."drive train"? "Steering Connector"?...the red part upper-center)...miss those wheels too..:|"

Universal joint.

That's the second time VSOTW has featured a set I've just ordered. Also so far I own (or soon will own) six of the sets featured (okay in the case of Mobile Crane I own the Europe/UK/Aust version).

Very cool stuff, those gears! I was just a little too late to the party to have those myself, but always loved to use them when visiting an older cousin who had lots of those.

Somehow I do have a couple of the studded track pieces to be used with these gears....

@PurpleDave said:
"It looks very complicated (and expensive) to make, and it’s probably a bit fragile."
Although these 2x4 bricks are made from two seperate parts they are fairly robust.
Aaannd: they came preassembled.

@NotProfessorWhymzi said:
"Anybody willing to sacrifice a few for science?"
What kind of experiment do you suggest? These gears are - also - very robust.
Plus: All of them can be used at 90° angle.

So shortly after the article on technic pins, we get this set!
Don't mind this set, just Lego being ahead of its time...

Those axles are a bit thicker than the later Technic ones by the way. They're a bit more tight than others.

I remember getting this set back in 1974. I think my grandparents bought it for me.
The gears themselves were pretty tough, I don’t recall them ever breaking.

I have some blue and yellow gears from sets like these. Never knew how to use them as a kid because we never saw directions. We inherited a suitcase of Lego from our older cousins, which is how our pre-minifig lego journey began.

@MCLegoboy:
I’m sure it was common. Did they have any other equivalent parts, either bricks for horizontal, or plates for vertical, or was this the only part you could feed and axle through? I wasn’t referring to aftermarket price, though (and it’s worth noting that a _lot_ of the Used parts note bites, scratches, discoloration, and/or dented corners). I meant cost to manufacture. How many sections did they need for a mold that produces _one_ of these? I can identify top, bottom, and 3-4 sides (depending on whether one insert reaches across to the opposite side), for a minimum of 5-6 separate pieces of tooling. Now figure out how to make that work with a 4-cavity mold. And the inside is molded separately, so it uses twice as much time on the injection molding machines, plus you have to assemble it before shipping (something they have redesigned a lot of molds to avoid).

Not every common part is easy to produce:

https://www.bricklink.com/catalogList.asp?catType=P&catString=991

Former community liaison Steve Witt said that 30104, the 21-link chain, was the most complex mold he’d ever seen in person. Think about what it takes to mold 21 connected links all at the same time, at such a tiny size no less, and you wonder why they even bothered to look at the possibility of making such a part. And they’ve now made four different parts using that same design. The long and short versions are fairly common in some colors, not too expensive on the aftermarket, but probably rank pretty high in terms of price by weight for TLG to actually produce. Why do they make them? Sometimes you need a chain, and nothing else will do.

Technic needs three things to work, which are gears, axles, and something to provide structure to hood the gears and axles. Modern Technic bricks can be produced with a 4-section mold. Beams and liftarms only need two sections. None of these require any pre-assembly, or multiple components.

I answered an add for 'Various LEGO for sale - 10$', and ended up with a few sets, still in boxes, including this one. 100% complet!

@PurpleDave said:
"*snip*"
I did mention the cost probably being high in the 70s, but as I went on, clearly it doesn't affect the thought process of the aftermarket sellers. All that matters is rarity, the cost of the set certain parts come in, and what people are willing to pay. And it seems that @chefkaspa knows what it took to make this part, just two molds, which is pretty simple.

@McLegoboy, I have to agree with @PurpleDave on this one. I’ve never been involved in hard tooling, but I have done some soft tooling in my time. The bottom part is probably straight forward to produce, but that top part with all the holes on the sides, would require multiple inserts, as noted, so that it could be ejected from the tool. So yeah, probably a complicated tool. @PurpleDave, I’d love to see the tooling for any of the chain pieces.

I live these gears! Inside the red hub of each gear is a springy but of metal that helps the gear grip the axles. Near the ends of each axle there is a hardly-noticeable indentation. This allows the spring metal bits to grip the axle just a little more firmly at the ends. It helps stop your contraptions taking themselves apart when they're in motion. Beautiful engineering by Lego!

@chefkaspa said:
" @PurpleDave said:
"It looks very complicated (and expensive) to make, and it’s probably a bit fragile."
Although these 2x4 bricks are made from two seperate parts they are fairly robust.
Aaannd: they came preassembled.

@NotProfessorWhymzi said:
"Anybody willing to sacrifice a few for science?"
What kind of experiment do you suggest? These gears are - also - very robust.
Plus: All of them can be used at 90° angle."

I am old enough to have had these sets as a child. My recollection is that the gears were very strong and I have no broken gears in my collection. The early axles were the weak point and would twist under any sort of torque. Many of my early axles have twists in them.

@MCLegoboy said:
"That 2x4 Brick wouldn't be so bad to have every now and then."
K'Nex actually made a similar brick back when they briefly introduced Lego compatible parts.

The photo of the child on the box proves that Mako from Kill la Kill is real and was alive in the 1970s.

@MCLegoboy:
Nah, @merf71 has it. You can make any shape you want in a one-piece mold, but the only way to get the part out is to destroy the mold. They do this for some jewelry, carving it out of wax before encapsulating it in a solid mold. Pour molten gold in, which melts the wax and forces it out of the mold, and then you crack the mold off of the piece of jewelry after it’s cooled down.

That’s a pretty inefficient way to do injection molding, so everything starts with two-piece molds that have top and bottom halves. Part of the mold has to fit inside the element to form cavities, and part of the element has to fit inside the mold to form protrusions. A 2x4 brick is simple because you have bumps on top and pits below, so one half forms the interior and the other forms the top and sides.

A 1x4 Technic brick is more complex. It also has cavities from below, and studs on top (this time with their own cavities). This time, however, you also need to mold pin holes through the sides. Because of the recessed lip for pin flanges, you have to have two more sections that insert from both sides. One has to form the main tube, so that one will have to be retractable prior to opening the top and bottom halves of the mold. The other side only needs to form the inner lip, so that could be accomplished with a hinged section that moves out of the way as the part is ejected, and then pops back into place automatically. If I was designing this mold, rather than using a single hinge design so the section pivots out like a door, I’d use a pair of arms that are hinged at both ends, so the mold section pulls straight out of the element as the element is ejected.

The outer shell of this part has a bottom cavity and studs on top, but it now has holes on all four sides. Besides the two main sections, you can add double-hinged retractable mold inserts, but you could also use a single insert to form the holes on two opposite sides. The other two sides will still need one insert each, since the first insert would block their path through the center. So, that’s one mold with five or six sections just to mold the exterior shell. I can’t see what the inside section looks like, so I don’t know if that can use just a simple two-section mold, or if it would also need hinged sections or removable plugs.

One instance where a 3-piece mold did make production easier than a 2-piece mold is the Technic pin joiner. The original version was molded in two pieces that had to be glued together. Each section could be molded with a basic 2-piece mold. The current version switched to a single 3-piece mold that used an insert from one side to form the wider space in the center for the pin flanges to hook into.

@merf71:
You and me both. He said it was the most complicated, but never explained how it worked.

Milky white axles, just learned that these existed last week