threelink Posted July 4 Share Posted July 4 Tea kettle or not, Sisters clearly worked well. I'm not sure of the extent to which thermal efficiency was foremost in the minds of the pioneers. From a certain perspective, just producing something that worked was a triumph. Link to comment Share on other sites More sharing options...
What About The Bee Posted July 4 Author Share Posted July 4 (edited) Without Twin Sisters, the LMR would have been grossly delayed. I did not mean to diminish it. Heck, I'm building it because I admire it. In mentioning Stanier, the implication was that those early pioneers were the giants, inventing an industry from whole cloth. Stanier could not improve a design that did not exist. The early pioneers were concerned with efficiency and hence the reason why the fuel was weighed both before and after their run at Rainhill. Indeed, why Stephenson and Wood used a Dynamometer (see my yellow avatar Stephenson's Dynamometer) to measure retarding friction. Twin Sisters was inefficient, as was noted by the LMR. It was broken up December 1831, 15 months after Opening, unsuitable for nearly any operation. Bee Edited July 4 by What About The Bee Link to comment Share on other sites More sharing options...
threelink Posted July 4 Share Posted July 4 You are right, as ever, Bee. The operating companies were concerned about efficiency. I intended only to suggest that the very early pioneers such as Newcomen and Trevithick were more likely to be driven by the desire to produce a working machine than by considerations of thermal efficiency. The desire for greater efficiency on the part of the mining companies fuelled Watts improvements to the atmospheric engine. Link to comment Share on other sites More sharing options...
What About The Bee Posted July 4 Author Share Posted July 4 (edited) We are in agreement Three Link. While the forum is a great place to exchange ideas, sometimes communication can be stilted. Its all too easy to be misunderstood or, especially in my case, communicate poorly. Thank you for continuing the conversation. Here is a major update to the CAD model of Twin Sisters. I have been unhappy with the Markits crosshead. Once I made the pistons and cylinders to scale, the Markits part just looks too big I decided to make my own. Firstly, because the interference with the connecting rod and the crosshead bars forced an unnecessary compromise. They were coplanar and they banged into each other. Secondly, because I could make a smaller one. I will use 0.5 mm rod for the crosshead bars and 1.5mm OD tube for the crosshead itself. This will provide a rattle fit of 0.008" on all sides of the crosshead rods. If I attempt 1.0mm OD tube, the buildup of tolerance would likely bind the entire assembly. I've added in the support for the crosshead rods, extending the cylinder support plate to do so. This makes mechanical sense, as the lower rod support would not be mounted on a flimsy fender, but rather held on the same plate to retain crosshead rod integrity. Further, the connecting rod is out of plane from the crosshead, just as Stephenson did, eliminating any compromise in support. I am a much happier camper! Bee Edited July 4 by What About The Bee Correct autocorrect 2 Link to comment Share on other sites More sharing options...
threelink Posted July 5 Share Posted July 5 If anyone communicates poorly Bee, it is I not you. Link to comment Share on other sites More sharing options...
What About The Bee Posted July 7 Author Share Posted July 7 Electricals The next challenge was how to bring power from one rail, through the motor and then back to the other rail. Enough with the art of a chimney door, determine how to power the motor. OO Twin Sisters is just over 49 mm long and roughly 33 mm from front to rear wheel contact points. With such a short locomotive, I want all wheel pickup. A commercial part exists to bring power from the metal tire, across the plastic insulating wheel, to the metal axle, but this demands the live/insulated wheel axle regime. I have but three axles. No matter how I distribute this commercially available part, one side of the locomotive may have two pickups, while the other side of the locomotive will be limited to one. Or simply one on each side, skipping one axle entirely. That is a recipe for stalling on track, as Twin Sisters will lose connection to electrical power. I measured the pickup foil on an existing model and found it to be 0.08mm. Sheets of 0.08 mm beryllium copper foil are readily available in consumer quantities. Beryllium copper has a higher mechanical yield than pure copper, making it more suitable for springs, while retaining the vast bulk of the conductivity of pure copper. There will be two main bus bars down the length of Twin Sisters. Each bus bar has three fingers which contact the back of the metal tire of the wheel at top. As I intend DC¹, a simple wire from each bus bar is brought to the motor. The circuit is complete. While the bus bar is inside the cart, the fingers will go through slots to the outside of the cart. A dimple plier will be used to form a hemispherical bead on each beryllium copper finger. The bead will be held against the tire by spring pressure. As the 1st and 3rd axles shift side to side to accommodate 2nd radius (438mm) curves, the fingers can either follow the wheel out or tuck completely back into pockets formed into the sides of the cart. The fingers will not interfere with the full range of side to side travel of the axles. Will the fingers be noticeable and obvious? Even if you know where to look, and have the benefit of the contrasting colors of a CAD model, the pickup fingers are not obvious when the complete locomotive is presented Once camouflaging paint is applied, the fingers may disappear altogether. With the proposed model now complete, I can proceed to parts ordering. Obviously, some features will need revision due to actual dimensions, instead of estimated dimensions on some parts once they arrive. Artistic rivets and flanges will be definitely added, whilst coving up those flathead screws in the top of the boiler. While the design is far from complete, the proposed model is most definitely feasible. I can get power to a motor. The gearbox is duck soup simple. The mechanical parts are largely purchased Romford / Markits components. The crosshead and crosshead rods are commercially available stock. It all seems to fit together without worry. I think its time to commit! Bee ¹ For the foreseeable future. The boiler that does not have a motor is completely empty. It could readily fit a decoder and small keep alive. Vent heat right on up through the chimney. But for now, DC it is. 1 Link to comment Share on other sites More sharing options...
What About The Bee Posted August 4 Author Share Posted August 4 OO Twin Sisters has a geared axle. In my initial sketches, I supposed that the bull gear (disk, with gears on edge) had straight teeth. This would permit the geared axle to move side to side, relative to the chassis. I received the Romford 60:1 gear from Scale Link. The bull gear has enveloped teeth, that is, the teeth wrap around the worm gear. The geared axle is the middle of the three axles. My immediate concern was lateral compliance. How would this go around a OO R2 (438 mm) curve. The axle cannot shift relative to the chassis. I solve that here Fixed axle Computation in Round the Bend This alleviated my concern. The nominal gap between the F2F and the Track (Q=.148 mm) is far larger than the lateral compliance (Y = 0.012 mm). I can distribute this as I wish, it will be fine. On to my next poorly reverse engineered object, the crankpins. Bee Link to comment Share on other sites More sharing options...
What About The Bee Posted August 15 Author Share Posted August 15 (edited) The enveloped gear caused a cascade of issues, but I think I found my way back out. I chose Markits Deluxe Crankpins, as the crankpin bushings thread onto the post. Unfortunately, as you can see on the right hand side, the bushing does not bottom out, there is a gap. This necessitated a complete redraw of the crank pin assembly, shown here As this pushed the piston connecting rods outboard, I was finally forced to provide a notch instead of a through hole for the cross head. The side mounted footplates became ridiculously wide and I was forced to accept that the detail shown by Issac Shaw would not be. Shaw has the crosshead going through the footplate. And then the fun began. Can I make OO Twin Sisters go around a second radius curve. The first consideration is the the mid axle is trapped by the enveloped gear. It cannot move laterally. This also means that the chassis cannot shift like OO Experiment. I check the equations for the requirements of the second axle to fit and found that indeed it will fit Since the chassis cannot move, full compliance must be permitted on both sides of the chassis for the 1st and last axles. I ran the equations https://community.hornbyhobbies.com/forums/topic/36321-round-the-bend/?do=findComment&comment=394450 I found that when I injected the result (0.499 mm per side), that the chassis was too wide. I was forced to completely redraw the chassis, not only because of the lateral compliance, but that the dimensions I used for the motor did not account for any real world tolerance. I have added in some false floors in the front and rear. The boilers are now printed in parts and assembled with magnets. The electrical traces are let into the walls of the chassis, hiding them away. Its been a real struggle, but I think it resolved. Bee Edited August 15 by What About The Bee Forgot to ref an image 1 Link to comment Share on other sites More sharing options...
threelink Posted August 15 Share Posted August 15 @ Bee. This project continues to fascinate. I am so impressed by your engineering solutions to the manifold problems that crop up. I think I would have given up long ago. I can't wait to see the finished product. Link to comment Share on other sites More sharing options...
What About The Bee Posted August 15 Author Share Posted August 15 Hi @threelink Never give up! Thomas Edison, famous inventor of the photograph and light bulb, said something in 1932, as published in Harpers Magazine. During the interview, the interviewer asked about Edison's genius. "Genius is one percent inspiration and ninety-nine percent perspiration" What I am doing is certainly not genius. I am not attempting to wear that cloak. But the ethos in Edison's statement is clear. Work hard. Never give up. Problems occur. Work harder. You can do this. Bee 1 Link to comment Share on other sites More sharing options...
What About The Bee Posted August 19 Author Share Posted August 19 The tiny washers have arrived. The crankpins have a shoulder which prevent the crankpin bush from fully seating at the flange. This creates a gap which could bind on the coupling rods. See pink arrow. The washers have a 1.2 mm ID, which fits very closely to the 0.96 mm OD of the crankpin shoulder. These washers were specified as 0.2 mm thick, but are actually 0.18 mm thick. It was 4 washers fill the gap but I may need 5. See blue arrow. I am in the process of making the assembly procedure. This has revealed one shortfall in the design. As designed, it would be nearly impossible to assemble. Relatively easy fix, but requires a few tweaks. Bee Link to comment Share on other sites More sharing options...
What About The Bee Posted September 4 Author Share Posted September 4 The following is my 9th cut at an assembly procedure. Normally, there would be an engineering review prior to release. I've done a self assessment of the design and procedure. This is the reason for 9 assembly procedures. The deficiencies noted and corrected during my self review are (1) The electrical components could not be assembled as designed. The model revised. (2) The interior 'false floors' wwre merely floating in the design. They needed a mechanical attachment. The model revised. (3) This is the most hilarious. I did not install any coupling to the locomotive. It would not haul marl or indeed anything. I've fixed that, obviously, permitting either the Accurascale magnetic chain OR the Hornby finescale peg. If you have the time, take a read through it. I am quite interested to hear any thoughts. Why? I may have missed something. Self review is so very hard because one must discard any pre-conceived notions, held internally. So please, feel free to toss out any ideas. No guarantees about what I will do with them, but ... Bee ----------------- Twin Sisters Assembly 1 Preparation 1.1 Make Beryllium Copper pickups Etch or cut? Sheet material 0.2 mm thick (0.008”) will cut with razor. Will this curl or deform the sheet? Some experimentation is in order Dimple pliers to create dimples on tabs. Electrical contact via rounded dimples not sheet (and edges) of beryllium copper sheet. 1.2 Coupling Rods & Connecting Rods To be manufactured from Alan Gibson “universal coupling rod” AG part number 4M92. 1.3 Solder Leads The wires to the motor and to the pickups must be attached, prior to any assembly. Tin all flying leads 1.4 Paint All components to be painted prior to assembly. Note: Colors in this assembly document do not necessarily denote a separate part. 1.5 Magnet Installation Various components will be attached by magnets. Epoxy all magnets into place, mindful of polarity. Boiler cosmetic caps are held to boiler bases by magnets. Front and read boilers are symmetric so either cosmetic cap can be on either boiler. Of interest, the chimney door on one cosmetic cap is open, the other closed. The curved stem into the horizontal member is held to each boiler cosmetic cap by a magnet. All 8 magnets shown in the following transparency. 2 Install Pickups Tab for each wheel bent to slide thru gap. 3 dabs of glue under large side, correlated to each wheel. Affix to inside of cart. 3 Axle Bushings Install axle bushings into cart with a dab of glue 4 Wheels and Axles 4.1 Crank Pin Installation Install crankpins into plastic wheels, 6 times. Install washers onto each crank pin. Install crankpin bush to each crankpin. Cut crankpins to proper length. Back out crankpin bush to re-establish thread. Re-tighten. 4.2 Axles Dress square axle boss, all three axles, both ends. Install Axle into THREE wheels. Install axle retaining nuts (locktite?). Leave 3 wheels free. Slide first and last wheel / axle assembly thru bushings, keeping dimpled pickup tab from fouling. Bring free wheel to axle on opposite side. Mind the quartering. Install Wheel onto axle, keep dimpled tab from fouling. Install axle retaining nuts (locktite?) Center axle will hold Romford bull gear. Use diamond burr to create a flat for grub screw. Mark location for later reference. Hold bull gear in place, slide wheel axle assembly thru bushing and gear, keep dimpled tab from fouling. Slide all the way thru. Bring free wheel to axle on opposite side. Mind the quartering. Install Wheel onto axle, keep dimpled tab from fouling. Install axle retaining nuts (locktite?) DO NOT TIGHTEN GRUB SCREW FOR GEAR. CONFIRM ALL QUARTERING IS CORRECT AT EACH WHEEL INSTALLATION. Drop of oil, each bushing / axle interface. 4.2.1 TEST The time to fix things is now, before other stuff interferes. 4.2.1.1 Electrical continuity Test each wheel against the appropriate wire lead. 4.2.1.2 Free wheel Place on track, insure it can roll without dragging pickups to foul. 5 Motor Installation Romford Worm Gear is held on shaft with grub screw. Use Diamond burr to make small flat on shaft. Install worm gear. 5.1 Into Boiler Slide N20 motor up into lower boiler body. Align mounting screw holes. Install motor screws M1.4 (lockte?) 5.2 Boiler Onto Cart Attach rear False Floor into cart using M1 screw from below Slide Boiler Motor Gear assembly down into cart. Insure that the worm gear engages properly with the bull gear. The bull gear, being loose on the axle, can slide side to side and rotate around axle. Attach lower boiler body to cart using hardware. 5.2.1 TEST Gears mesh properly, do not bind. Twist top motor shaft to observe that the bull gear is turning. 5.3 Bull Gear Rotate Bull Gear such that grub screw is visible. Align flat on shaft to grub screw, using previously installed mark. Tighten Grub Screw (locktite?) alligator clip motor lead to pickup lead, (2 times) in region of opposite boiler. 5.3.1 TEST Will the center wheels turn when power is applied to track? Is the polarity correct? Pistons are in front per Shaw. Hornby standard is ‘forward from cab view, right rail is positive’. 5.4 Solder Leads With all checked, solder tinned leads together. Leads go into front boiler cavity. Insure proper length. Insulate with shrink sleeve tube. 6 Install Front Boiler Attach front false floor with M1 screw. Slide boiler base into cart. Attach with hardware, as before. 7 Pistons 7.1 Crosshead Assembly Epoxy short tubes to each crosshead. Allow to cure. Install crank pin into cross head. Trim base to length (diamond burr?) Thread cross head rods from bottom, thru crosshead tube and into top holes. Epoxy in top holes to hold rods. Rear axle rotated and shifted to accommodate access. 7.2 Coupling Rod Assembly Remove crank pin bushings one side, keep crankpins up to keep washers in place. Install coupling rod onto crankpins. Re-install crankpin bushings. Flip to crank pins down. Insure that each bushing is thru coupling rod holes. Tighten crank pin bushings, insuring coupling rod is not pinched. 7.2.1 TEST Rotate exposed motor shaft by hand. Insure coupling rod functions as intended. That there is no binding. REPEAT ASSEMBLY AND TEST FOR OTHER SIDE. 7.3 Connecting Rod Assembly Install washers onto crosshead, one side. Install Connecting Rod loosely into position. Install crank pin bushings at crosshead and at wheel. 7.3.1 TEST Free to move, no binding. REPEAT ASSEMBLY AND TEST FOR OTHER SIDE. 7.4 LUBRICATION A drop of oil at each crankpin bushing 8 FULL FUNCTIONAL TEST ON TRACK Twin Sisters is now capable of being run on track, with all mechanical assemblies in place. Both directions, various speeds. 9 Cosmetics 9.1 Boiler Chimney Cap Assemblies Place manually, aligning chimney doors per design. The attaching magnets will grab to orient and keep in place. 9.2 Horizontal Steam Reservoir Place manually, magnet retention. 9.3 Chimney Stays Bend and install 4 times chimney stays. The only thing to install are the diagonal wires 10 Install Coupling Install brass rod into NEM coupling and then coupling into false floor 10.1 Test Model uses finescale chain Attach to Hornby Era 1 Utility Waggon, shown here in grey and to scale Insure the wagon remains coupled at various speeds and both directions Enjoy the model! 1 Link to comment Share on other sites More sharing options...
LTSR_NSE Posted September 4 Share Posted September 4 Bravo @What About The Bee Very clearly & beautifully written - almost detailed enough to be instructions for a purchaser building a kit model. 👍 The only section I would want extra detail for is: • how do the stay wires attach to/detach from the chimneys & boiler caps? (I imagine they need to be detachable? since the boiler caps themselves are.) Link to comment Share on other sites More sharing options...
What About The Bee Posted September 4 Author Share Posted September 4 Point taken @LTSR_NSE. I will clarify in the Assembly Procedure. If you zoom into the ends of the chimney stays, you will see a lug with a through hole (4 places). The wire is bent at the appropriate angle and slipped into the hole. I do not know it they will stay in place without a tiny dab of glue. Thank you for pointing out this weakness in the procedure. The model accommodates the stays already, its just the procedure. Bee 2 Link to comment Share on other sites More sharing options...
What About The Bee Posted September 6 Author Share Posted September 6 (edited) @LTSR_NSE Here is the revised paragraph 9.3, dealing with chimney stays. When I posted the manual for review, it was precisely to find this sort of weakness. I supposed the notional sketch showed my intention for the stays. If it was unclear to you, it would be unclear to others. Further, it is now clear to me that no dab of glue will be required, as the stay shape cannot fall out. If you wouldn't mind letting me know, is this a little better? Bee --------- 9.3 Chimney Stays Bend and install 4 times chimney stays. 9.3.1 Before 9.3.2 After 9.3.3 Chimney Stay Shape Install four stays. It is unclear from the Shaw drawing how the four stays clear each other. For the model, they will simply criss cross each other without finesse Edited September 6 by What About The Bee White space at bottom 2 Link to comment Share on other sites More sharing options...
LTSR_NSE Posted September 6 Share Posted September 6 That’s perfect @What About The Bee 👍 The extra pics of: all the stay parts in different colours; magnification of collar & boiler attachment points; & wires isolated (therefore showing bends;) really explain exactly what is required. That brings this area up to parity with the rest of your extremely clear instruction manual. Bravo 👏 1 1 Link to comment Share on other sites More sharing options...
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