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Post by Roger on Jun 13, 2019 22:12:24 GMT
To my mind, the obvious solution to a 'bouncy' Speedy is to fit proper leaf springs rather than coiled springs. Leaf springs are far superior in their characteristics, and also prototypical. Coiled springs are very difficult to get right and adjust, and easily 'bottom' out, and have a tendency to oscillate on short wheel bases. I have never quite understood why Bill Perrett's 'Speedy' bounced about as it is a heavy loco, and if it had light springs these would have bottomed out. If it had stiff coil springs it would not have bounced about, but would have presumably slipped quite a bit. Cheers, Julian Hi Julian, Although there's no doubt that leaf springs give some degree of damping, it's far from ideal. Hydraulic dampers are likely to be much more effective. I might fit leaf springs one day, but it's an awful lot of work for little benefit in my opinion. The problem with setting up coil springs is not such an issue if you can measure the load on each wheel in real time. I don't know how close Bill Perrett's SPEEDY was to bottoming out, but I'd guess that it was mighty close. It looked most bizarre in it's current form, like a ship rolling on the ocean. I don't see anything fundamentally wrong with really soft springing so long as there is adequate damping.
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Post by Roger on Jun 13, 2019 22:13:26 GMT
With your knowledge of electronics Roger, how about an active suspension? That really would be novel! Now there's a thought... don't get me started...
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,907
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Post by JonL on Jun 14, 2019 8:19:17 GMT
I guess leaf springs have more inherent friction damping due to the leaves rubbing against each other
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Jun 14, 2019 8:24:44 GMT
To my mind, the obvious solution to a 'bouncy' Speedy is to fit proper leaf springs rather than coiled springs. Leaf springs are far superior in their characteristics, and also prototypical. Coiled springs are very difficult to get right and adjust, and easily 'bottom' out, and have a tendency to oscillate on short wheel bases. I have never quite understood why Bill Perrett's 'Speedy' bounced about as it is a heavy loco, and if it had light springs these would have bottomed out. If it had stiff coil springs it would not have bounced about, but would have presumably slipped quite a bit. Cheers, Julian I think the main problem with using coil springs is that the authors of constructional articles in ME and the like rarely give any details about the springs. One knows the exposed length of the spring pins when the axle-box is at the bottom of the horn, so the spring must be at least that long. When the axle-box is at the correct running height, the length of the partly compressed spring is known, and knowing the weight of the loco, the rate of the spring can be calculated. Finally, when the axle-box is at the top of the horn, the closed length of the spring must be less that the exposed length of the spring pins. Knowing these factors, and consulting the catalogues of makers such as Lee Spring, the correct springs can be obtained.
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Post by andyhigham on Jun 14, 2019 9:16:08 GMT
Another thing to look at is progressive wound springs. The coils are wound closer together at one end. On initial movement the whole length of spring is in operation giving light springing, as the spring is compressed the close coils close up effectively shortening and stiffening the spring
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Post by Roger on Jun 14, 2019 9:53:54 GMT
Another thing to look at is progressive wound springs. The coils are wound closer together at one end. On initial movement the whole length of spring is in operation giving light springing, as the spring is compressed the close coils close up effectively shortening and stiffening the spring I suppose concentric springs of different length would have a similar effect.
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uuu
Elder Statesman
your message here...
Posts: 2,809
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Post by uuu on Jun 14, 2019 9:59:04 GMT
With so much effort being put into getting the static appearance of the loco right, to rob it of the characteristic nod and weave when running seems perverse.
Wilf
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Post by Roger on Jun 14, 2019 13:34:14 GMT
With so much effort being put into getting the static appearance of the loco right, to rob it of the characteristic nod and weave when running seems perverse. Wilf In reality, there's little chance of eliminating it, however hard I try. You also have to factor in the over scale undulations on our rough and ready tracks.
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Post by Roger on Jun 14, 2019 21:38:41 GMT
The pivot pin looks like it's a headed one with a washer and split pin to hold it all together. That's not easy to make because the pin is only 1.2mm diameter and it's 9.5mm long. That means it's very flexible and drilling the hole can't realistically be done when it's been turned to size. Worse than that, you can't turn that length with that much overhang unless you do it in one big cut to the exact size. So here I've turned it to 3mm and set it up dead centre and to the end so I can drill the 0.6mm hole for the split pin 20190614_204012 by Anne Froud, on Flickr 20190614_204713 by Anne Froud, on Flickr Then it was turned from 3mm to 1.2mm in one cut and after a couple of goes I made this one... 20190614_222709 by Anne Froud, on Flickr ... which looks like this. 20190614_222757 by Anne Froud, on Flickr The second one is a bit under size, so I'll have to make another one of those. I might grind that one to the finished size, but it's hard to measure it without bending it, it's so flexible even though it's Phosphor Bronze
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Post by terrier060 on Jun 14, 2019 22:24:24 GMT
Another thing to look at is progressive wound springs. The coils are wound closer together at one end. On initial movement the whole length of spring is in operation giving light springing, as the spring is compressed the close coils close up effectively shortening and stiffening the spring I suppose concentric springs of different length would have a similar effect. On the Terriers I intend to try two coils, a heavier one on the outside with a lighter on in the centre of it. I only have a single spring and guide per axle, hidden under the false leaf springs. I disagree with Julian about leaf springs being easier to adjust - quite the opposite. Also it is essential to have a little end play on the axles to stop the axleboxes binding.
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jma1009
Elder Statesman
Posts: 5,901
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Post by jma1009 on Jun 14, 2019 22:55:30 GMT
Hi Ed,
You misquote me. I never made any comment that leaf springs were "easier to adjust". I just think that proper leaf springs are superior to coil springs.
Your own 7.25"g Terriers would, IMHO, benefit from you having made the individual 'fake' spring leaves of spring steel instead of ordinary steel strip, and not resorting to using coil springs. Instead, you are using Greenly's 'a spring within a spring' going back to the RHDR in the early 1920s, instead of doing a proper job of it.
Cheers,
Julian
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Post by delaplume on Jun 14, 2019 23:21:23 GMT
Hello all--------didn't the 57xx have leaf on the first 2 wheelsets and coil on the third inside the cab ???
I believe the Kings had square section coil on the front axle ( after the Midgham incident ) ??
I have progressive coil on my Enfield Bullet forks...........If you opt for "Coil within a coil" then the one coil must be wound in the opposite direction to the other or they will become "Coil bound" and lock up..
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Post by Roger on Jun 15, 2019 6:45:14 GMT
Hi Ed, You misquote me. I never made any comment that leaf springs were "easier to adjust". I just think that proper leaf springs are superior to coil springs. Your own 7.25"g Terriers would, IMHO, benefit from you having made the individual 'fake' spring leaves of spring steel instead of ordinary steel strip, and not resorting to using coil springs. Instead, you are using Greenly's 'a spring within a spring' going back to the RHDR in the early 1920s, instead of doing a proper job of it. Cheers, Julian Hi Julian, I thought that your comment 'Coiled springs are very difficult to get right and adjust" was pretty clear? Either way, I would have thought that getting the right spring loading on leaf springs would take a lot of experiment and be more difficult to get right, not the other way round? If leaf springs were superior, they would still be using them on locomotives and carriages today. A steam locomotive doesn't easily accommodate coil springs in full size, so the use of them does makes sense there. If there is no damping, they are probably a better choice, but if you have damping, coil springs, without the inherent friction of leaf springs, are preferable. Friction is not a very effective form of damping. Friction dampers were used on early cars and motorcycles, but were quickly replaced by hydraulic types which provided a better ride and avoid 'stiction'. The fact that early cars still required additional damping even when they used leaf springs is interesting. Presumably this is because roads introduce much larger body movements than happens on locomotives. Our situation is similar, we get much more movement through over scale deviations in the track, so we shouldn't be surprised when we end up with excessive body roll when we adopt soft springing. I'm sure that leaf springs help to some extent, but it's not enough in my opinion. You end up with two choices, either to have strong springs and lose adhesion, or have soft springs and have a lot of body roll. Neither of these are ideal, hence the wish to add some additional damping to allow for softer springing with less body roll. It's a fascinating topic.
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Post by 92220 on Jun 15, 2019 8:32:58 GMT
Hi Roger.
I've had quite a few tiny steel pins to turn, with 1/32" holes in the ends for split pins, and even smaller cross holes for 0.5mm taper pins. I always make up a drill jig with a smallpiece of BMS square/flat bar, with the hole for the pin to be drilled, about 1/16" below the top surface of the jig. By using a jig, pin holes in multiple pins are all in exactly the same position and can be anything down to within 10 thou of the end of the pin. The jig also helps to support the tiny drills and prevent breakages (hopefully!). I tap the outer end of the hole for the pin, so that I can fit a small screw to adjust the position of the cross hole from the end of the pin. As far as turning a long length of small diameter goes, I've turned a 1" long x 0.06" dia steel pin. I did it by using 1/8" dia BMS rod and just turning down a length of about 1/8" to 0.060" dia, and then turning the next 1/8" length, and so on until I had the full length of 1". As long as the tool is ultra sharp, there should be no see-able join between each bit of turning.
I like your idea of using titanium welding rod for soldering supports as solder doesn't stick to it. Until I read it in your thread I hadn't heard of that. I must get some!
Bob.
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Post by ettingtonliam on Jun 15, 2019 9:36:07 GMT
I seem to recall that LNWR used coil springs quite a lot (the Coal Tanks, Prince of Wales, possibly the Claughtons) allegedly because they were cheap!
Wm Pickersgill used coil springs on the front coupled axle and crank axle of his infamous 956 Class 4-6-0 'express' locos for the Caledonian Railway c 1920, and volute springs on the bogie. They had a 'lively' ride to put it politely, and it was probably fortuitous that the many other problems of the class prevented them from getting much over 60mph.
Do the coils of volute springs touch each other, to give some degree of damping?
Going back to tiny pins, thats a good idea to drill the cross holes before reducing the shank size. Have you given any thought to using a boxing tool for reducing the shank size in one go. Much used on capstan lathes I seem to recall.
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Post by Roger on Jun 15, 2019 11:29:10 GMT
Hi Roger. I've had quite a few tiny steel pins to turn, with 1/32" holes in the ends for split pins, and even smaller cross holes for 0.5mm taper pins. I always make up a drill jig with a smallpiece of BMS square/flat bar, with the hole for the pin to be drilled, about 1/16" below the top surface of the jig. By using a jig, pin holes in multiple pins are all in exactly the same position and can be anything down to within 10 thou of the end of the pin. The jig also helps to support the tiny drills and prevent breakages (hopefully!). I tap the outer end of the hole for the pin, so that I can fit a small screw to adjust the position of the cross hole from the end of the pin. As far as turning a long length of small diameter goes, I've turned a 1" long x 0.06" dia steel pin. I did it by using 1/8" dia BMS rod and just turning down a length of about 1/8" to 0.060" dia, and then turning the next 1/8" length, and so on until I had the full length of 1". As long as the tool is ultra sharp, there should be no see-able join between each bit of turning. I like your idea of using titanium welding rod for soldering supports as solder doesn't stick to it. Until I read it in your thread I hadn't heard of that. I must get some! Bob. Hi Bob, If I had a lot to drill, I might make a jig, but it's not really necessary for one or two. One advantage of drilling on a larger diameter is that there's less of a problem with drill wander on the initial entry because the curve is much less. I'll bring you some Titanium welding wire when I next see you,, I've got loads of it. It's useful for scratching implements when soldering.
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Post by Roger on Jun 15, 2019 11:34:05 GMT
I seem to recall that LNWR used coil springs quite a lot (the Coal Tanks, Prince of Wales, possibly the Claughtons) allegedly because they were cheap! Wm Pickersgill used coil springs on the front coupled axle and crank axle of his infamous 956 Class 4-6-0 'express' locos for the Caledonian Railway c 1920, and volute springs on the bogie. They had a 'lively' ride to put it politely, and it was probably fortuitous that the many other problems of the class prevented them from getting much over 60mph. Do the coils of volute springs touch each other, to give some degree of damping? Going back to tiny pins, thats a good idea to drill the cross holes before reducing the shank size. Have you given any thought to using a boxing tool for reducing the shank size in one go. Much used on capstan lathes I seem to recall. It would be interesting to know how many derailments were caused by the lack of damping. I don't usually do enough turning in one pass to need a boxing tool, but it could come in handy for big jobs. Mind you, I tend to switch to using the mill as a CNC lathe when I get into ten pieces or more, mainly because you can do other operations at the same time.
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Post by Deleted on Jun 15, 2019 14:01:35 GMT
[/quote]It would be interesting to know how many derailments were caused by the lack of damping. I don't usually do enough turning in one pass to need a boxing tool, but it could come in handy for big jobs. Mind you, I tend to switch to using the mill as a CNC lathe when I get into ten pieces or more, mainly because you can do other operations at the same time.[/quote]
I doubt if derailments are due to damping per se. Badly set/broken springs, worn flanges and damaged permanent way yes. I also wonder how long a damper would last with hammerblow etc. Regarding coil vs leaf springs, I think it's evident by how locomotive designers changed from coil to leaf which is better. Interestingly, Gresley's first A1 'Great Northern' was designed to have coil springs for the crank axle and leaf springs for the leading and trailing axles. This is how she entered service although this idea was ditched very soon after with all other A1,3,4 pacifics being fitted entirely with leaf springs. I do recall reading the reason why the change but can't remember the details now...I'll try to find where this was written but don't hold your breath waiting..it may take a while...
Pete
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Post by 92220 on Jun 15, 2019 22:01:12 GMT
Hi Bob, If I had a lot to drill, I might make a jig, but it's not really necessary for one or two. One advantage of drilling on a larger diameter is that there's less of a problem with drill wander on the initial entry because the curve is much less. I'll bring you some Titanium sledding wire when I next see you,, I've got loads of it. It's useful for scratching implements when soldering. Hi Roger. Thank you. That's very kind. Bob.
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Post by terrier060 on Jun 15, 2019 23:46:45 GMT
Hi Ed, You misquote me. I never made any comment that leaf springs were "easier to adjust". I just think that proper leaf springs are superior to coil springs. Your own 7.25"g Terriers would, IMHO, benefit from you having made the individual 'fake' spring leaves of spring steel instead of ordinary steel strip, and not resorting to using coil springs. Instead, you are using Greenly's 'a spring within a spring' going back to the RHDR in the early 1920s, instead of doing a proper job of it. Cheers, Julian You are quite right Julian - I apologise. You actually said coil springs are more difficult to adjust, which I still disagree with! I shall experiment when the time comes and may come to the same conclusion as you, as you have probably had a lot of experience with leaf springs. You are also correct that proper leaf springs may be preferred, but then there is the complication of keeping them scale thickness without using Tufnel or cutting relief spaces along the centre of them. I adopted the coil spring approach as I have to make twelve of them, the four centre springs being longer than the eight leading and trailing ones. I hope to persuade Roger to allow me to use his excellent wheel scales - some time ahead I fear at the rate of progress I am making. I very much admire the speed as well as the perfection that you achieve Roger, even though you get sidetracked into many other projects like your roller stand, overhead crane, the weighbridge to name a few! Ed
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