Answers.Body: <h1>3652 Technic Engine Piston Square 2 x 2</h1>
  
  <p><img src="https://i.sstatic.net/c6P0k.png" alt="3652"></p>
  
  <p>This part was included in sets from 1977 until 1995, but it began to be replaced by 2851 starting in 1990:</p>
  
  <p><img src="https://i.sstatic.net/cx6y6.jpg" alt="2851"></p>
  
  <p>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:</p>
  
  <p><img src="https://i.sstatic.net/qFS7U.jpg" alt="2850"></p>
  
  <p>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.</p>
  
  <p>Imagine how much space it would take to build this V8 using the old style of piston:</p>
  
  <p><img src="https://i.sstatic.net/psOvD.jpg" alt="8070 Super Car with engine visible"></p>
  
  <h1>3651 Technic Axle and Pin Connector</h1>
  
  <p><img src="https://i.sstatic.net/rdItx.png" alt="3651"></p>
  
  <p>This part was technically available in sets from 1977 until 2003, but it was generally replaced by 32013 starting in 1997:</p>
  
  <p><img src="https://i.sstatic.net/ZY4l8.jpg" alt="32013"></p>
  
  <p>This was part of a general overhaul of Technic axle connectors that replaced <a href="http://www.bricklink.com/catalogItem.asp?P=4273" rel="noreferrer">4273</a> with the angled family of connectors (32013, 32034, 32016, 32192, 32015, and 32014).</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-02-26T10:39:12.177Z
Answers.Text: 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...
Answers.UserDisplayName: Zhaph - Ben Duguid
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-02-26T10:57:16.727Z
Answers.Text: 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.
Answers.UserDisplayName: SQB
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2014-02-24T15:59:59.907Z
Answers.LastActivityDate: 2014-02-24T17:26:29.270Z
Answers.LastEditDate: 2014-02-24T17:26:29.270Z
Answers.UserDisplayName: jncraton
Body: <p>Bricklink has <a href="https://www.bricklink.com/catalogItem.asp?P=3651" rel="nofollow noreferrer">piece 3651</a> as <em>Axle and Pin Connector</em>, while <a href="https://www.bricklink.com/catalogItem.asp?P=3652" rel="nofollow noreferrer">piece 3652</a> is <em>Engine Piston Square 2x2</em>. You could attach them to each other to form a piston.</p>
  
  <p>Service pack 5260, <a href="https://www.bricklink.com/catalogItem.asp?S=5260-1" rel="nofollow noreferrer"><em>Connecting Rods and Stop Bushes</em></a>, has them together in a set.</p>
  
  <p>When were they discontinued?</p>
  
  <p>Why were these useful parts discontinued?</p>
  
Tags: <technic><piece-information><history><discontinued>
Title: When and why were pieces 3651 and 3652 discontinued?
UserDisplayName: SQB
ThreadText: # When and why were pieces 3651 and 3652 discontinued?
  
  (Asked by: username_0 on 2014-02-24)
  
  Bricklink has [piece 3651](https://www.bricklink.com/catalogItem.asp?P=3651) as *Axle and Pin Connector*, while [piece 3652](https://www.bricklink.com/catalogItem.asp?P=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*](https://www.bricklink.com/catalogItem.asp?S=5260-1), has them together in a set.
  
  When were they discontinued?
  
  Why were these useful parts discontinued?
  
  **Tags:** technic, piece-information, history, discontinued
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2014-02-24. Score: 6 | Accepted answer
  
  # 3652 Technic Engine Piston Square 2 x 2
  
  ![3652](https://i.sstatic.net/c6P0k.png)
  
  This part was included in sets from 1977 until 1995, but it began to be replaced by 2851 starting in 1990:
  
  ![2851](https://i.sstatic.net/cx6y6.jpg)
  
  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:
  
  ![2850](https://i.sstatic.net/qFS7U.jpg)
  
  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](https://i.sstatic.net/psOvD.jpg)
  
  # 3651 Technic Axle and Pin Connector
  
  ![3651](https://i.sstatic.net/rdItx.png)
  
  This part was technically available in sets from 1977 until 2003, but it was generally replaced by 32013 starting in 1997:
  
  ![32013](https://i.sstatic.net/ZY4l8.jpg)
  
  This was part of a general overhaul of Technic axle connectors that replaced [4273](http://www.bricklink.com/catalogItem.asp?P=4273) with the angled family of connectors (32013, 32034, 32016, 32192, 32015, and 32014).
  
  > **Comments:**
  > **username_2**: 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...  
  > **username_0**: 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.  
  
  ---
  
  