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Post by Roger on Oct 15, 2022 10:35:01 GMT
Roger, More turns for the same length, smaller wire gauge or larger diameter coil will all result in a softer spring. You will need the springs to be longer and have some pre-load on them (break-off force) otherwise when the load is at the bottom, there will be no force actually pushing it there. Cheers,Mike Hi Mike, Thanks for that, I'll make some longer ones and experiment with the wire gauge too. I've got something set up on the Weighbridge, so I can perform a few experiments.
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Oct 15, 2022 11:21:37 GMT
When I purchased the springs for my Pansys, I worked out the length of the spring when the axlebox was at the bottom of the horn, to give the minimum overall length of the spring. I then worked out the length when in the running position - and then by dividing the overall weight (taken from weighings at IMLEC) by 12, I calculated the spring rate. And then worked out the length of the spring when the axlebox was at the top of the horn (maximum bound length).
With these figures, plus the internal diameter of the spring pins, I looked up the Lees Springs catalogue to find appropriate springs. The engines are not finished yet, so I can't be sure if I got it right, but the chassis, with cylinders and valve gear and un-soldered boiler, seem to sit somewhere about right. Time will tell.
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Post by Roger on Oct 15, 2022 16:06:10 GMT
When I purchased the springs for my Pansys, I worked out the length of the spring when the axlebox was at the bottom of the horn, to give the minimum overall length of the spring. I then worked out the length when in the running position - and then by dividing the overall weight (taken from weighings at IMLEC) by 12, I calculated the spring rate. And then worked out the length of the spring when the axlebox was at the top of the horn (maximum bound length). With these figures, plus the internal diameter of the spring pins, I looked up the Lees Springs catalogue to find appropriate springs. The engines are not finished yet, so I can't be sure if I got it right, but the chassis, with cylinders and valve gear and un-soldered boiler, seem to sit somewhere about right. Time will tell. That's the way I was looking at it, but at Mike points out, that would give zero force on the axle when it's fully in the down position. My worry would be that a wheel might lift off the track if the axle couldn't follow the undulations of the rail because there was insufficient forct to move it down.
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Post by chris vine on Oct 15, 2022 20:46:09 GMT
Yes, a little bit of force at the bottom of the travel is what is needed. Even if is not much more than enough to overcome the friction of the axle box in the horns… C
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Post by Roger on Oct 15, 2022 21:04:22 GMT
I found that the pins on the Turning Frame fouled the clearance in the legs when I put the Chassis down onto the Weighbridge which was a pain. So today I stripped the legs down and sawed the clearances both wider and taller to make using it easier. I can't stand struggling when it's supposed to be easy. This clears nicely now. PXL_20221015_203159659 by Timothy Froud, on Flickr I've dropped the Boiler in place to get this up to somewhere near the finished weight. PXL_20221015_202045302 by Timothy Froud, on Flickr In case you missed the Weighbridge build, it uses six cheap strain gauges which allows the loads on all of the wheels to be seen together. The control box uses a dedicated interface chip which is interrogated by a PIC Microcontroller. The serial output is sent to a cheap bluetooth module that the Smartphone can interface with using the excellent free 'Bluetooth Electronics' App that Pete (Doubletop) put me on to. The middle axle has a shoe that stops the Locomotive rolling off the bars. Each bar floats on a pin and ball arrangement in an attempt to stop it wedging and affecting the readings. PXL_20221015_202104912 by Timothy Froud, on Flickr Anyway, these are the readings I've got from the first tentative experiment. I'm expecting the total weight to be maybe another 5-10Kg max on top of the 46.75Kg with the Pannier Tanks, Cab & Bunker. The rear axle is on the left, and it has four of the 1.2mm wire springs that are 23mm long with the nuts at the bottom position. The axle is sitting too low, partly because the springs are probably too strong and also because the other two axle springs are too weak. The middle and front axle have 1mm wire springs that are 20mm long, but they are compressed by the nuts by about 4mm. So I've ordered some 1.1mm wire which I'll probably make 25mm long to start with. The available space for the uncompressed springs is 20mm. Screenshot_20221015-213718 by Timothy Froud, on Flickr One thing that's very obvious when moving the locomotive on the Weighbridge is that stiction plays a huge part in what the readings show. Hopefully this will become less pronounced when it's loosened up with running. However, there will always be a significant effect with Locomotives that have Leaf Springs since these introduce a fair bit of friction. It's very difficult to get meaningful readings in these situations if you have to measure one axle at a time because the loadings on the axle you've just measured won't be the same when you measure the next one. The error can be significant. When I've finally got the correct weight springs, I'll have to push the Locomotive from side to side and front to back to get a good idea as to what the true loadings are without friction by taking the averages of multiple readings.
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Oct 16, 2022 8:42:33 GMT
When I purchased the springs for my Pansys, I worked out the length of the spring when the axlebox was at the bottom of the horn, to give the minimum overall length of the spring. I then worked out the length when in the running position - and then by dividing the overall weight (taken from weighings at IMLEC) by 12, I calculated the spring rate. And then worked out the length of the spring when the axlebox was at the top of the horn (maximum bound length). With these figures, plus the internal diameter of the spring pins, I looked up the Lees Springs catalogue to find appropriate springs. The engines are not finished yet, so I can't be sure if I got it right, but the chassis, with cylinders and valve gear and un-soldered boiler, seem to sit somewhere about right. Time will tell. That's the way I was looking at it, but at Mike points out, that would give zero force on the axle when it's fully in the down position. My worry would be that a wheel might lift off the track if the axle couldn't follow the undulations of the rail because there was insufficient forct to move it down. I've highlighted a word in my original post. The chosen spring will be slightly longer than the minimum, and will exert a small force when the axlebox is at the bottom, based on the amount of compression. However, I wonder if we don't overthink this somewhat. When you see the definitions of the springs given by the designers, they are very hit-and-miss. Whilst I am sure that a properly balanced loco will be more sure-footed, and will bounce less that one where the springing is 'out', there have been thousands of engines built using the crude methods described, and they all seem to work.
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Post by Roger on Oct 16, 2022 10:49:37 GMT
That's the way I was looking at it, but at Mike points out, that would give zero force on the axle when it's fully in the down position. My worry would be that a wheel might lift off the track if the axle couldn't follow the undulations of the rail because there was insufficient forct to move it down. I've highlighted a word in my original post. The chosen spring will be slightly longer than the minimum, and will exert a small force when the axlebox is at the bottom, based on the amount of compression. However, I wonder if we don't overthink this somewhat. When you see the definitions of the springs given by the designers, they are very hit-and-miss. Whilst I am sure that a properly balanced loco will be more sure-footed, and will bounce less that one where the springing is 'out', there have been thousands of engines built using the crude methods described, and they all seem to work. All fair points, like you say they all seem to work. Crude methods are used because most people don't care as long as it works, and it's a lot of effort to measure things. Also, there's only so much you can vary before you run into trouble with suspension being too soft or too stiff. With all that being said, I think it's worth going the extra mile to measure the weight on each wheel, you might as well get as much grip as you can with what you have. I measured the Club locomotives, and they were miles out. Most locomotives can't realistically use soft springing because it's just too unstable without damping. I've seen a SPEEDY rolling like a ship on the Ocean, and it's a wonder it stayed on the tracks. Leaf springs don't cut it for damping in my opinion because they just add friction, and not much of that. Hydrostatic damping gives a lot more flexibility, and that's what I want to explore. The intention is to use the Locomotive for some of our ground level fete activity, and that can be really challenging when it comes to getting enough grip with the heavy loads we pull.
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dscott
Elder Statesman
Posts: 2,438
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Post by dscott on Oct 17, 2022 5:45:01 GMT
A friend in The Reading Club built a Paddington for someone years ago and filled the tanks with bits of lead and worn out tungsten cutters. Yes water is still put in the tanks and she sits solidly on the track and pulls anything put behind her.
Another friend ran his Twin Sisters with the weight of the full tanks represented by 2 steel bars each side and then she worked.
Then there is me making running boards out of solid with a slight reduction towards the cylinders on the Nigel Gresley 01. I just have to do the double bend next.
David and Lily.
In full size on Sunday the Hall lost her feet out of East Grinstead does The Buckimghamshire Steam Center have weighing facilities like they have at Didcot?
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Post by Roger on Oct 18, 2022 20:47:43 GMT
This is how the Whistle Valves look on 1501... 20180110_111622 by Timothy Froud, on Flickr ... and this is my interpretation of that. I've actually got the Works Drawing for this, but I had to make it very slightly over scale to make it practical. Even then, it's very small. Originally I showed a design with a PTFE cone for the valve seat, but it's just too small to make it that way. The valve shaft is only 1.2mm diameter. Instead I've opted for another of those Silicon Nitride balls, this time 2.5mm diameter. Sectioned whistle valve assembly by Timothy Froud, on Flickr Once the bodies were parted off (I made them months ago) they needed to be held the other way around so the inside details could be machined. There's only a short parallel section that's 3.9mm diameter to get hold of, so the 3 jaw isn't really suitable. Again I've made a supporting bung to fit the back of the appropriate ER32 collet so that I can get a good grip on it without the back collapsing. As usual, I've added an 'O' ring to stop it falling out. PXL_20221018_202114786 by Timothy Froud, on Flickr The inside has a 1.9mm seat diameter for the ball, and a 3mm clearance. I've added the clearance using a 3mm Carbide End Mill like a flat bottomed drill. You can only get away with this when you're not removing too much material. If you try to do that, the cutter doesn't self centre, and instead moves away from the centre and makes a mess. PXL_20221018_195741943 by Timothy Froud, on Flickr Anyway, here are the parts for both of them, with one of the pairs of arms being held the right distance apart by a short spacer made from Brass. PXL_20221018_202441137 by Timothy Froud, on Flickr It's pretty tiny, and what makes it more difficult to assemble is the fact that the nut is captive. The nut needs to be in place while the rear union fitting is Silver Soldered in place. Plenty of scope for cockups there! Anyway, here's a sanity check to make sure it will fit on the branch pipe. PXL_20221018_202908790 by Timothy Froud, on Flickr
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Post by chris vine on Oct 19, 2022 9:13:06 GMT
Looks fab to me. I am sure that with the jewellers technique of a sliver of silver solder pre-placed, it will work out fine. C
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Post by 92220 on Oct 19, 2022 22:26:13 GMT
Lovely job Roger!!!
Bob.
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Post by Roger on Oct 20, 2022 11:41:35 GMT
So far so good. Obviously they need sprucing up, but the main things are that the nut is still free to move, the joint looks solid and the thread will still take a nut for the outlet pipe. PXL_20221020_104942696 by Timothy Froud, on Flickr Next I need to Silver Solder the brackets, and that's going to be fiddly. Fortunately the arms are a good fit in the slots, and I can mount it on its side to use the base nut for some support. I may need to clamp something against the body in case the whole thing moves when it gets hot. I've looked at several options for applying the Silver Solder, but didn't like any of them. Wire or Strip is going to be hard to attach to both arms so that it melts into the joint. Applying it by hand is asking for it to move and get way too much on there. So I've opted to use Silver Solder Paste which is eye wateringly expensive, but I think will give me the best chance of success. PXL_20221020_111306458 by Timothy Froud, on Flickr In case you're wondering about the colour of these parts, it's all made from Phosphor Bronze. Brass isn't very strong when you get to small pieces like this, and it's also very easy to melt when you're Silver Soldering. I want this to be robust even though it's tiny because it's a functional item that's going to get some real forces applied to the arm to operate the valve.
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Post by Roger on Oct 22, 2022 21:48:48 GMT
While I'm waiting for the Silver Solder Paste to arrive, I thought I'd try to get the Valve Gear complete so I can time it and run it on air again. Here are a few shots of 1501 and my interpretation of the reverser. Reverser16 by Timothy Froud, on Flickr I'd made this years ago, but I hadn't sorted out the tiny pins, washers and split pins. The pins are 1.6mm diameter with a 0.55mm hole for the split pin. PXL_20221022_154327820 by Timothy Froud, on Flickr PXL_20221022_154351744 by Timothy Froud, on Flickr Putting it all together for the first time showed that I hadn't made the exit hole in the Spectacle Plate big enough, so here's the jaunty arrangement for holding that so I could file it. PXL_20221022_163504976 by Timothy Froud, on Flickr PXL_20221022_163519348 by Timothy Froud, on Flickr The back bolt holding the Reverser together is also a foot rest so you can get some real force on the lever. It's very stiff at the moment, so that's to scale too. Reverser10 by Timothy Froud, on Flickr PXL_20221022_205128971 by Timothy Froud, on Flickr The Pole Reverser goes through the floor and engages with a pin the comes through the back of the folded bracket with the gussets. I've copied this arrangement so that the pigot can be disconnected and the Pole Reverser withdrawn from the top. IMG_1428 by Timothy Froud, on Flickr I've cross drilled the pivot for a Split pin, but that's not fitted yet, and neither is the washer. PXL_20221022_212348510 by Timothy Froud, on Flickr The Reach Rod can be removed without too much pain, I can just get to the top bolt of the retaining bracket and swing it round to get the pin out. PXL_20221022_212356336 by Timothy Froud, on Flickr Reverser by Timothy Froud, on Flickr PXL_20221022_212433452 by Timothy Froud, on Flickr PXL_20221022_212457678 by Timothy Froud, on Flickr PXL_20221022_212530793 by Timothy Froud, on Flickr There's a bracket between the Reverser Frame and the side of the Cab. I may fit that, but I haven't decided yet. The lever obviously needs a fair bit of force to move it.
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,912
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Post by JonL on Oct 23, 2022 12:35:17 GMT
The levers don't typically need that much force, although some locomotives can snatch it out of the hands of the unwary if you are not holding it properly when notching up!
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Post by Roger on Oct 24, 2022 10:39:07 GMT
The levers don't typically need that much force, although some locomotives can snatch it out of the hands of the unwary if you are not holding it properly when notching up! Isn't this why you should close the regulator while you notch up?
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Midland
Elder Statesman
Posts: 1,871
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Post by Midland on Oct 24, 2022 10:50:35 GMT
The levers don't typically need that much force, although some locomotives can snatch it out of the hands of the unwary if you are not holding it properly when notching up! Isn't this why you should close the regulator while you notch up? You might want to look at the Blue Peter incident when the reverser got out of control. Driver had both arms broken. www.national-preservation.com/fo ... 79&start=0 Peppercorn A2 60532 Blue Peter 1994 Durham Wheelslip ...www.youtube.com › watch or just google Blue Peter incident David
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Post by ettingtonliam on Oct 24, 2022 12:19:04 GMT
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Post by Roger on Oct 24, 2022 12:25:20 GMT
Isn't this why you should close the regulator while you notch up? You might want to look at the Blue Peter incident when the reverser got out of control. Driver had both arms broken. www.national-preservation.com/fo ... 79&start=0 Peppercorn A2 60532 Blue Peter 1994 Durham Wheelslip ...www.youtube.com › watch or just google Blue Peter incident David Hi David, That was a pretty shocking incident. I imagine they tried to arrest the motion by getting the gear into the middle. There's surely a screw reverser, not a pole type, so I'm not sure what happened. Maybe it all sheared off? I wouldn't have thought the screw could be driven in reverse, regardless of the amount of force applied to it.
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Post by Roger on Oct 24, 2022 15:08:39 GMT
The last time I set the Valve Timing, I printed out a protractor on paper, laminated it and cut it out. That was stuck to the wheel with masking tape and worked tolerably well. However, I couldn't find it, and I also wasn't that happy with how floppy it was. I initially thought I'd print one out and then machine a ring on the Mill from backing board, but then realised that a far better solution would be to 3D print that. So here's the first iteration of that idea, with a rounded dovetail at each end to join them together when they're on the locomotive. PXL_20221023_140137309 by Timothy Froud, on Flickr That worked pretty well, but the alignment still wasn't easy to get right. I could see that the chamfer on the edge of the wheel offered a shallow register potential, so that's what's on this iteration. I also made a couple of clamping elements to see if that would hold it better. PXL_20221023_174735473 by Timothy Froud, on Flickr Neither of those worked out well, so I improved the design and increased the resolution of the 3D print to get a better rim. It then dawned on me that if I added the degree marks as grooves, they could be printed face down if I carefully chose the line widths and depths so that they would still stand out when the print was pulled off the build platform. That's all well and good, but the lines aren't that visible. I tried using white nail varnish, but that didn't work. However, Tippex worked a treat. PXL_20221024_130448499 by Timothy Froud, on Flickr Then I realised that I could embed magnets into the ring so it would keep itself on and also allow for it to be adjusted. So finally, this works exactly how I want, although you can see there's a cockup in the length of the lines on the two halves! I'll probably make a final version with that tidied up. PXL_20221024_144949031 by Timothy Froud, on Flickr Ok, it's not pretty, but it's functional. The Rolling Road has a sharp pointer that can be inserted in the edge of the angle, exactly in the middle of the two rollers. PXL_20221024_144959517 by Timothy Froud, on Flickr Now I'm sure that someone is going to say that they do something really simple that takes two minutes and works just fine, but that misses the point. I've really enjoyed beating my head against this problem and figuring out what I consider to be an ideal solution that will enable me to not only set the valves but measure the cutoff distances at each notch. Did I need to do any of this, probably not, but you know what I'm like.
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,912
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Post by JonL on Oct 24, 2022 15:59:03 GMT
The levers don't typically need that much force, although some locomotives can snatch it out of the hands of the unwary if you are not holding it properly when notching up! Isn't this why you should close the regulator while you notch up? Exactly that. But a screw reverser has made me complacent sometimes.
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