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Build a lever frame for your points

frame

frame construction

At the time of writing Christmas is on the doorstep again, which means for me at least to have plenty of time to play with the tools in the loft. Several years ago I was in the same situation as now, in need of something to set the points on a new piece of layout. With that in mind I already had purchased a kit with 6 levers on one of the famous Chatham shows. But on close inspection of this kit I found the mechanical design not very satisfying and apart from that I needed at least the double number of levers. With that in mind I did some last minute shopping acquiring bits of K&S brass and some spring material that seemed suited. Together with what I had in stock I constructed a lever frame with 16 levers. That amount nicely fitted the 20 cm width of brass sheets that were in my stock. There are still 3 levers available for future extensions.

The kit I had came from Ambis and it is an etched construction. What I didn't like was the fact that once the levers are in, you can never take them out again without dismantling the entire construction. Further the levers consisted of 3 layers soldered together of .5 mm sheet to arrive at 1.5 mm requiring some hefty solder work. Also I was not particularly impressed with the frame itself. 2 sides kept apart with some simple fold up profile can hardly being called a rigid construction. Thus instead of using the kit directly, I made a similar construction but without these drawbacks. The photo and drawing accompanying this piece show the result, but do take care as I do not guarantee all dimensions to be 100% correct, it was produced only for reference purposes.

With 16 levers all exerting force on the frame you need to make it into a rigid construction. Between the end plates there are 3 steel rods, 2 of 6 mm at the base and one in the center of 3 mm cross section. This latter rod is also functioning as main pivot axle. As the 3 mm rod flexes over a length of 20 cm there are 2 brass keepers at 1/3 and 2/3 to maintain the position of the rods. Due to lack of space these are not drawn, but dimensions are similar to the end plates but square 50x50 mm with 6 mm holes for the 2 lower rods. You also need to make some thoughts on how to fix the box onto the layout of course. I used some aluminium angle of 50x25x3 mm and screwed it against the back of the layout. These angles and the 1 mm brass end plates are fixed with screws to the 6 mm rods. The 3 mm rod is 2mm longer than the others and sticks through the end faces. It is thus locked between the aluminium angles but apart from that it cannot move sideways anyway because of clamps on the rod itself to keep the levers in place. The frame also has a top and front. The front is also for show as it is a niece piece of 1 mm thick polished brass but it does help a lot to make the top stiff as it is soldered along the edges to the side plates and top. The levers stick through the slots and the holes are used to lock the lever in its end positions. This is the most difficult part. The two rows of equally spaced holes are not the problem but cutting the slots is quite a task. I used a milling machine but if attacking this with hand tools consider the possibility of first bending and fitting as cutting the slots with a hacksaw and filing will become easier if it is more rigid and curved. An alternative screwed construction can be seen below in the photos of the leverframe of Bill Newton. The top plate is 0.5 mm brass. I found that bending this into a nice curve was difficult and I was not entirely satisfied. I used a heavy rod to roll the sheet into a curve over a slightly giving underground. If you know someone with a tool for rolling boilers you'd better buy him a beer in turn for using his tool for a moment. The back of this top sheet is reinforced with a piece of 3 mm square strip along its length. For soldering all the brass items into a single construction I used a large gas flame such as used for plumbing. The rods are helpful to keep the dimensions and make it rigid. Maybe use a 3 mm thread in the center to keep it square and fix it during the soldering.

If you are still following this while reading then you have now arrived at a 4 sided box with 3 rods ready to fit the levers into. Before you go any further you may consider that the brass looks much nicer if you polish it and that this is much easier to do beforehand than after fitting the levers. No need to say that I did it the other way round of course.


lever construction

The levers itself are basically from 6 x 1.5 mm brass K&S strip. The top is extended with a steel handle. This part is from steel rod turned to a taper and polished in the lathe. It could be changed to non-tapered rod or alternatively try a bit of filing with a mains hand drill to arrive at something similar. These handles are soldered to the strip as the end of the strips have neck and shoulder and the handle a small pothole and slot. To keep the lever removable there is a separation between the part that is driving the point mechanism and the lever itself. Thus the lever has a slot in the bottom that fits the 3 mm rod. Just above this is a 1 mm hole. In this hole a 1 mm pin engages that sits on the round piece drawn up beside the lever. This parts brings the rotation over to a pin that is screwed into it. To keep these parts engaged to the lever the distance between two levers is filled with the distance block. This comes with a slot and locking screw and thus can be taken out. When such a block is taken out the two neighbouring levers can be disengaged and be removed completely. The form of these blocks is not important, only the width makes up for the remaining distance between two levers. The levers itself have a catch handle that is controlled by a spring. I made the catch handles from 0.4 mm NS. To make them more rigid these are curved. These is a bit of blacksmith work by hammering a 6 mm steel rod into a piece of NS on a notch in a wooden block. These catch handles are fixed with a 0.8 mm spring steel wire to a fold up of 0.4 mm NS sheet. In this fold-up another wire of brass is hooked that glides up and down through 2 short pieces of tube. In between the tube is a piece of 3 mm rod that engages into the 3 mm openings in the slots of the top plate. This is rigid enough for not allowing to move the levers without using the catch handle. A weak point in the design turned out to be the original fixing of the steel wire of the catch handle to the fold-up. In the heavier used levers these have been changed to the design in the drawing with the extra lip for a larger soldering surface. These are soldered with 240 degree soft solder containing silver for extra strength. A job easy to do when you can take the lever out but near impossible with the lever mounted as the pins in the fold-up are fixed by rivetting the ends.


A sketch of my lever frame, dimensions in millimeters

Connecting the points to the levers can be of any construction. I used a simple 0.8 mm nylon wire construction. The nylon wire is guided through eyelets screwed in the baseboard. At the TOU end the wire is attached by a spring and a length adjuster in the form of a M3 screw. The spring takes the excess length. The length adjuster is only used at installation. The TOU mechanism itself contains its own spring in the form of a microswitch to move it back to its own stable position. I did not produce any nice number plates as the weekend was too short for that. As the photo shows I put some numbers with a filt scriber instead to assist guest operators. Neither did I built any interlocking mechanism.

Reflections

Visiting the last Scaleforum I was in the occasion of inspecting the leverframe of Bill Newton, which did show a very nice mechanical interlocking. His frame is a much closer representation of a 1:1 lever frame. The accompanying photos that he kindly allowed me to make show his frame and details of the interlocking.
As I installed the first points on a my layout Waimes earlier this year I have to give thoughts on how to control these. This new layout is much more complex thus there is more need for an interlocking mechanism. This would also add more operational fun at playing trains as well as more fun at modelling time. The major difference is that the new layout exists of several modules and not a single one. Thus there are base boards to cross if using a single frame. Alternatively a frame that operates switches for electrical operation of the point is more realistic as this is closer to prototype and solves the base boards problem. On the other hand it introduces a new one: a reliable electrically operated point motor not costing large sums, not making operational noise, not asking for continuous power, moving slowly etc. To make things more complex the main signalbox of my prototype had an AEG lever frame of German origin, which is of much more complex construction. In such a box the lever rotates over an angle of 180 degrees driving a wire running over a disc. The catch handle is connected to the interlocking part. Fiddling around with a prototype indicates possibilities but also a lot of work, maybe too much altogether. Old photos of the station of Waimes show rodding in the background which indicates that the minor box probably still had a leverframe of Saxby origin such as still can be found in Raeren. In Waimes this box was reconstructed in the fifties when the decline really set-in by simplyfying the layout. Thus all in all I still have to come up with an answer of how to control the new layout.

Photos of Bill Newtons frame on display at Scaleforum 2002


UK leverframe

Lever frame as built and displayed by Bill Newton at Scaleforum. photo Henk Oversloot

UK leverframe

The mechanical interlocking on the frame of Bill Newton. photo Henk Oversloot.
The contact angle of the oblong holes is such that the horizontal rulers can be driven by the contact forces between pin and slider.

Photos of the leverframe in Calw


This photo shows the inside of a signalbox at Calw in Germany with levers having a throw of 180 degrees. The handles are on one side of the disc only. A steel cable runs over the disc.

The interlocking box

Leverframes in Belgium


Two different leverframes in signalbox IV in St. Ghislain, Belgium.This box controls (the remains of) a yard. These levers are based on the Siemens design, the high frame in front has a throw of 120 degrees using a much larger disc with a chain running over it.. The handle spans both sides of the disc. The small frame for the yard points has a throw of only 60 degrees. Note that the catch handles are in front here.

Study of AEG leverframe for Waimes


AEG leverframe

A series of 8 levers scale 1:7 built to available scarce information photo Henk Oversloot

These levers were part hand built with a fretting saw and other parts were milled on the milling machine. The wheels are cast in PU from a master made on the milling machine. The interlocking was tested with a servo motor. In principle this works but I regard this design as not robust enough to withstand ignorant use on Fremo meetings.

interlockinglevers

A view of the locking mechanism

Parts for leverframe

A drawing of the mechanism (image not to scale)


copyright: Henk Oversloot
date: 11 december 2002
extended: 11 may 2003