Bricklink has piece 3651 as Axle and Pin Connector, while piece 3652 is Engine Piston Square 2x2. You could attach them to each other to form a piston.

Service pack 5260, Connecting Rods and Stop Bushes, has them together in a set.

When were they discontinued?

Why were these useful parts discontinued?

1 Answer 1


3652 Technic Engine Piston Square 2 x 2


This part was included in sets from 1977 until 1995, but it began to be replaced by 2851 starting in 1990:


The main advantage of the newer piston is that it allows more pistons to fit in a smaller area of space. The piston is able to fit into the 2850 2x2 cylinder:


The old piston required a brick-built 4x4 cylinder, so the new part allows for either smaller engines, or engines with more pistons in the same amount of space.

Imagine how much space it would take to build this V8 using the old style of piston:

8070 Super Car with engine visible

3651 Technic Axle and Pin Connector


This part was technically available in sets from 1977 until 2003, but it was generally replaced by 32013 starting in 1997:


This was part of a general overhaul of Technic axle connectors that replaced 4273 with the angled family of connectors (32013, 32034, 32016, 32192, 32015, and 32014).

  • Hmm, the new ones clearly look more "realistic" if that's what you're after, but I personally find the original ones to be more useful in a "sticky piston" kind of way ;) And when you add in the bulk needed for the pegs, you're only saving in one dimension... Commented Feb 26, 2014 at 10:39
  • 1
    Also, the old piston allowed to attach something to the top of it. I once made a space ship go up and down that way. But I really miss the studs on the side of the connector, they were very useful. Those connectors use with a 1x10 plates made for nice barriers, to name just one use.
    – SQB
    Commented Feb 26, 2014 at 10:57

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