Motorizing 9V switch points

, by  Didier ENJARY, Philippe “Frogleap” LABEL
[English] [français]

A review of various methods to motorize your 9V switch points (4531) : Either with a 9V motor (old type 2838 or new type 71427), or using a pneumatic cylinder (large, 2793 or small, x189).

When looking for information to motorize 9V switch points (4531), we realized that several proposals were available from some AFOL around the world. Some proposals were quite old (<2001) and some quite recent. In addition, some solutions with pneumatic cylinders were not exhaustively tested. To be honest, Philippe saw a solution based on the small pneumatic cylinder x189 more than a year ago, but the URL had disappeared from the web. Finally, this insignificant event pushed us to collect informations about existing methods and review them, describing at least one solution for each “motor” type. We hope this will benefit the community and some will even find it useful. This review was translated from its first french version with the significant help of Didier Enjary.

The 9V switch points, at least those you can buy today, have a locking position quite hard to overcome by hand. This lock is somewhat criticized by many of us. You may even unadvertently unclick the yellow lever (2866) when normally operating the switch point. Anyway, you have to solve this problem if you seriously consider motorizing your 9V switch points. There are two general trends in the “how-to” to tackle this problem : the modifyiers-trend and the conservers-trend. Let’s explain.

Softening the 9V switch point. The modifyiers propose to open the switch point, totally (Christian Haeuplik) or partially after undercover cutting (Dean Husby) to remove the two small locks which normally control the switch point mechanism. Be careful, if you remove them completely, then the switch point, when used without motorization, will change its position freely, most of the time with the vibrations when the train passes on... guess what will happen. The main advice is to control carefully the amount of plastic you remove when cutting-off those locks and try to leave a little bit of it to preserve some functionality. Everything is in a good self-control.

Strengthening the command. The conservers prefer using a command mechanism which delivers more power to overpass the lock without modifying switch point’s inside. Finally, this is the solution Philippe prefers because you can find now simple, efficient and powerful command mechanisms to put in your motorized unit. Besides a lack of natural poor self-control... for at least one of the authors ;-)

Lets analyse each solution and you will make your own decision out of it.

Solutions based on old-type 9V motor (2838).

  1. A proposal by Christian Haeuplik removes the yellow lever by the motorized unit. It turns to be a nice little tool cabinet. The lack of power of 2838 motor forces the use of a modified switch point. This is the reason why we propose both following solutions.
  2. Using a 2838 9V motor adapted by a simple gear reduction to the mechanism of Chris Alano originally proposed for a 71427 motor (see below). This unit works fast without modifying the switch point. A semaphore inspired by Ed McGlynn is added . Here is the Ldraw file and an assembly sheet in four parts (1, 2, 3, 4).
  3. Our top-rated solution is this one. Using the original Chris Alano’s mechanism enhanced by Amaury Jacquot, here is a small unit which delivers enough power to motorized non-modified 9V switch points. It takes such a small footprint, you can place it in-between two tracks in a regular track geometry. There is also a semaphore, following Ed McGlynn’s idea (see below). Fast, small, powerful, simple, nice and complete. Why would you ask for more? Oh yes ! The Ldraw file and the assembly sheets in three pages page1, page2 and page3.
    A mechanism from Chris Alano & Amaury Jacquot adapted to the 2838.

- Advantages : Can use old refurbished 2838-type 9V motors. Relatively faster than solutions based on 71427-type 9V motors. Uses widely available Lego parts.
- Drawbacks : You need old-style 9V motors.

Solutions based on the new type 9V motor (71427). With the help of many friends, here are eleven solutions (two of which are very close). Probably a non exhaustive list.

  1. Christopher Masi has a solution which imposes a modified switch point, otherwise the unit will separate rapidly from the switch point due to the mechanical effort. The absence of a torque-limiter mechanism is also a major problem for its stability.
  2. James Brown proposes a unit quite similar to the former, but a relatively higher stability by a better grip on the switch point studs. This solution uses one part 6180 which is quite difficult to find, at least in Europe.
  3. The following solution from Wessel Burgers, shares that very same drawback of a difficult-to-find 6180 part, but the use of a torque-limiter (60c01) will definitely stabilize the motor unit on the switch point. For this reason, you’ll have to use a modified switch point to operate it.
  4. Jason J Railton posted a Ldraw file on Lugnet describing a solution with torque-limiter thanks to a belt transmission. Therefore it requires a modified switch point as well. Philippe made an assembly sheet from Jason’s file with his agreement.
  5. Jeff Elliot and Ed McGlynn propose separately a complete solution including a semaphore. In addition the mechanism acts directly on the yellow lever which is conserved. We evaluated only Ed’s solution, and it supports a non-modified switch point thanks to the worm gear transmission and the direct-to-yellow-lever action. However, it is a quite slow acting motor unit, but provide a very nice little house close to the railway track.
  6. Mark Riley made a proposal quite equivalent to the former one: direct-to-lever action, non-modified switch point required. The aesthetic could be improved, and the semaphore signal is lacking despite the argument of the yellow lever visibility.
  7. Steve Ringe produced a small power unit with a semaphore and a torque limitation by a belt transmission (this solution was pointed out by Erik Amzallag). We didn’t test it, but it should work on non modified switch points since the power is transmitted to the yellow lever through a gear reduction. An interesting point is also its small size.
  8. Brian Alano proposes a solution with a torque-limiter by belt transmission, movement limitation by excentric axis and a semaphore. Almost perfect, but you need to use a modified switch point to operate this motor unit. Actually, we did not tested this solution because in the same time we saw another mechanism which would turn to be the best solution for us.
  9. This last solution is proposed by Brian’s brother on the same web page. Chris Alano proposes a mechanism with direct transmission (no torque-limiter) but a movement-limiter by an excentric axis and a sliding transmission to the command lever. This motor unit never separated from the switch point even after one hundred of tests. In addition, a semaphore can be installed. Here is the Ldraw file of a complete motorization unit using this mechanism, as well as an assembly sheet in two parts (sheet 1/2 andsheet 2/2). This motor unit uses Chris Alano’s mechanism, Ed McGlynn semaphore idea, all in a small sideway house. Be careful, the Ldraw file requires two unofficial parts (x68 and 32525). For those of you who don’t know what Ldraw is, take it easy, these parts are still official Lego parts. Here are the Ldraw files in “.dat” format for these parts. (x68.dat/axlendis.dat and 32525.dat/larm.dat). You must copy these files into your Ldraw’s “Parts” directory to use them. (By the way, Philippe Hurbain, produced the 32525 file... thanks Philo).
  10. Based on Chris Alano’s mechanism, Amaury Jacquot proposes an evolution by compacting the whole system using a smart parallel lever transmission. The result is as efficient and fast as the original, with a smaller footprint which allows you to place such motorization unit between standard parallel tracks. for us this is the best solution for motorizing non-modified 9V switch points with a 71427 motor. It is compact, fast (although not as fast as the 2838 option, see above), nice and very reliable. There is also an output for a semaphore. A complete semaphorized version with the parts available in Philippe’s stock was build (minor parts modifications from original Amaury’s mechanism), here are the Ldraw file and the assembly sheets in three pages page1, page2 and page3.
    A power unit based on the mechanism of Chris Alano & Amaury Jacquot and powered by a 71427 motor.

- General advantages : Fast operation for most solutions. Some solutions allow the use of non-modified switch points.
- General drawbacks : High cost per motorized switch point. Some solutions require the use of modified switch points :-).

Solution based on small pneumatic cylinder (x189). Philippe met only one proposal described in a text by Ben Fleskes on Lugnet. From Ben’s description of the mechanism, he rebuilt a pneumatic unit available in a (Ldraw file). It hardly works on non modified switch points, maybe not with a brand new one having a strong lock system. we recommend to use it on modified switch points. Here is the assembly sheet. Be careful, the Ldraw file of the yellow lever 2866 is not in the official distribution. Here it is, 2866.dat. The ldraw files for the x189 pneumatic cylinder was proposed by Marc Klein since the publication of the first version (in French) of this review. Now these files are available (thanks to Marc Klein) x189a.dat, x189b.dat, x189c.dat, x189c01.dat, x189c02.dat. Copy these files into your Ldraw’s “Parts” directory and this will enable the complete Ldraw file of this unit to be correctly visualized.

A power unit based on the small pneumatic cylinder.

- Advantages : Small size solution. Low cost.
- Drawbacks : This small pneumatic cylinder is quite difficult to find as a spare part. The lack of power will impose a modified switch point. No semaphore (waiting for a proposal...).

Solution based on the large pneumatic cylinder (2793). Philippe could not find any existing proposal but the one mentioned in the introduction and which disappeared from the web. Here is a Ldraw file of a pneumatic unit Philippe uses on his train layout. And here is the assembly sheet.

The 2793 large pneumatic cylinder in this power unit.

- Advantages : Works fine on non-modified switch points. Quite cheap compared to 9V motorized units. Pneumatic cylinder easy to find as spare parts.
- Drawbacks : Slow to operate. No semaphore, but waits for your proposals :-) .

Summarizing Table :

Author Motor Type Modifiy Switch Point Remove Yellow Lever Semaphore Usable
Christian Haeuplik 2838 yes yes no
Philippe Label 2838 no yes yes
Amaury Jacquot 2838 no yes yes
Christopher Masi 71427 yes yes no
James Brown 71427 yes yes no
Wessel Burgers 71427 yes yes no
Jason J Railton 71427 yes yes no
Jeff Elliot 71427 no no yes
Ed McGlynn 71427 no no yes
Mark Riley 71427 no no no
Steve Ringe 71427 no no yes
Brian Alano 71427 yes yes yes
Chris Alano 71427 no yes yes
Philippe Label 71427 no yes yes
Amaury Jacquot 71427 no yes yes
Philippe Label x189 yes no no
Philippe Label 2793 no yes no

The last minute advice. To motorize a switch point placed on a fast traffic switch point, use a 9V motor solution. Prefer solutions avoiding the internal modification of your switch points (you already knew our preference). Look at the solution proposed by Amaury Jacquot, an enhanced version of Chris Alano’s mechanism. Fast and reliable. The fastest being the 2838 motorization.
To equip an industrial railway track, you can go for a solution with the large pneumatic cylinder 2793, especially if you plan to put many switch points close from each other. You will benefit from the proximity for pneumatic connections and you’ll get an overall relatively low budget. But don’t ask for speed of operation.
The lowest cost is the small pneumatic cylinder (x189) solution. Placed in a small cabinet requiring few bricks, but you need to modify your switch point for this bargain.

Merry Christmas and happy train games to all of you,

Philippe “Frogleap” LABEL

Please forgive mistakes and drop a line if you find some, for the benefit of everyone. We will update when necessary.
- Special thanks to Marc Klein, Erik Amzallag and Denis Huot for providing additional informations.


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