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Hornby R920 has 12 insulated rail joiners for £2.99 or £0.25 each when you buy 12 One benefit to not installing irj is that you save £0.50 on the crossover.   There is a hidden safety issue if you do not install insulated rail joiners.  Consider, unplug the controller from the wall for the inner loop.  Set the points to cross over.  Turn the outer loop controller to maximum voltage, so as to test power to the inner loop at full speed.  QUESTION: what voltage is present at the plug of the unplugged controller? ANSWER: 220 volts.  QUESTION: what amperage is present at the plug of the unplugged controller?  ANSWER: less minimal conversion losses, just about the max amperage the plugged in controller can source.  WHY?  Voltage is converted down from 220 to 14 at the first controller and back up to 220 at the second (unplugged) controller.  In the field, we laughingly called this "Joltage" because that is going to give you a surprising jolt.  But it is no laughing matter, this can pack a punch. ÷÷÷÷ Aside from the safety issue, if irj are not installed, changing the points with mismatched polarity will short the track, independent of locomotive location. This may not be an obvious issue to troubleshoot.  What happened? If irj ARE installed and there is a polarity mismatch, the controllers will only short when the locomotive is actually crossing over.  This will be easy to troubleshoot, as the problem source will be located betwixt the seat and the controller. Bee  

Yes, He passed away November last year but had had serious health problems for a while before that.

I've had a look at his channel JJ.  He appears to be a non-native English speaker.  This will make for difficult communication.  He is very clearly an intelligent fellow, and his experiments on video are thoughtful. He appears to be looking for the minimum voltage the controller produces.  I asked him "Hello Alex.  To clarify, you want the minimum voltage across the terminals, with nothing connected, at half wave?"  Check to see if my question is there please.  youTube has been deleting my comments of late, apparently I talk too much hahahaha Once he responds, I can help you to answer his question, and help you to understand a multi meter. Please take a picture of your multimeter, front and back, and post them here so I can tell you the exact settings. Bee

I will head on over to your channel JJ, so as to understand the individual better Bee

Always so many details to discover.    In the previous post, I didn't include this drawing of Twin Sisters from The Liverpool & Manchester Railway, R.H.G. Thomas, 1980.   It appeared to be from a periodical known as "The Engineer", a non contemporary resource. This attribution was based on the font used, which is quite distinctive.  I am always very leary of non period sources and so skipped inclusion. It turns out that Thomas got the image from Marshall, A Century of Locomotive Building by Robert Stephenson, published in 1923 and again, likely from "The Engineer".  Marshall's image is therefore well out of period, the build to scrap period for Twin Sisters being 1828 to Dec. 1831. The choice morsel offered by Marshall, in 1923, is that the image in his book was "traced from the original undated drawing".  What??  I have investigated Marshall¹, and found other drawings, the most instructive being of Patentee, LMR33.  The drawing is signed by Robert Stephenson, dated June 12, 1840.  Patentee appeared on the railway in 1834.  Thus, these drawings are not precisely contemporary.  They may reflect remembrance by principals and therefore contain errors.  Yet they are directly from the firm of Robert Stephenson and Co. Ltd and thus authoritative.  Reviewed, apparently, by Stephenson himself. The original drawing of Twin Sisters is labeled "Liverpool Engine C" on that drawing, but is clearly Twin Sisters.  It is held in public view by the Science Museum.   https://collection.sciencemuseumgroup.org.uk/documents/aa110001922/liverpool-engine-c-drawing Please zoom the Science Museum's image to see detail.  Title in upper right hand corner. I have examined the drawing online, at high zoom magnification.  It is drawn at a 1:8 scale, as noted on the drawing.   One concern of note is that of the drawing traced in Marshall, the scale added appears inaccurate.  Remember, these are "traced from the undated original". The scale is not drawn on the original, it is merely stated as 1½ inches per foot.   For example, when scaling² the original drawing, I obtain a wheel diameter of 4' 1⅛" +/- ⅜".    When scaling the drawing from Marshall, using that added scale, I obtain 3' 9" wheel diameter.  That is a significant delta of ~4".  Marshall's scale is not to be trusted³. Yet, there are some interesting details revealed in the Stephenson mechanical drawing. In the end elevation, the drawing specifies that the back to back is 4 feet, 5½ inches.  Further, that the back of flange to face of rail is 1⅜ inches.  5½+1⅜+1⅜ = 8¼, consistent with the known gauge 4'8¼".  Not something to reproduce in the model, but something that lends to understanding this early railway. The valve gear is timed to the axle under the pistons, leading to the steam chest.  The valve gear is a detail not visible in Shaw but the steam chest is.   Not only is there a horizontally mounted steam reservoir, there are two other tanks mounted vertically nestled on either side, in between the large boilers.  Perhaps condensation traps or additional resevoirs.  This was made clear by the Stephenson drawing and once clear, became evident in  the Shaw depiction.  I hilariously missed these tanks in the first revision. Not visible anywhere are the openings in the chimney for loading fuel, sadly we still just have the description.  Pity that, such an odd feature. The Stephenson drawing does not show any body work at all.  It is merely a mechanical configuration drawing.  I trust that Shaw draws what he sees, and therefore, the body must be. With the OO squish problem, details such as boiler diameter cannot be directly translated. However, the ratio between boiler diameter to chimney diameter & etc can be measured and installed, leading to a reasonable appearance in OO. Examples: Chimney : Boiler ratio = .239 Horizontal Steam Reservoir : Boiler ratio = .148 Etc. My next task is clear. The CAD will be corrected to more closely match the Stephenson drawing, whilst including design cues from Shaw. Bee ¹ The book covers locomotives right to 1923, for example: Other modelers may wish to consult this book for details.  Who would not wish to model this beauty? 😉 ²Scaling drawings is typically bad engineering practice.  It is fine for making models.  The wheel scales somewhere between 4' ¾" wheel diameter to 4' 1½" wheel diameter.  The imprecision is due to the Museum's resolution of  ~¹/₁₆" per pixel and my ability to precisely pick out which pixel represents the line. ³Note that this 4 foot wheel diameter makes the adults in Shaw terribly short, which leads us back to scaling issues in Shaw as well.