baldric
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Post by baldric on Sept 26, 2021 20:41:10 GMT
I would suggest the offset cover is from another engine, one that has cover bolts at 45 degrees, making the oil feed go in the top. Baldric.
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Post by Roger on Sept 26, 2021 21:03:00 GMT
I would suggest the offset cover is from another engine, one that has cover bolts at 45 degrees, making the oil feed go in the top. Baldric. I'm not sure what you mean by the cover bolts at 45 degrees. If you look at the two covers, they look identical to me. It's just that one is fitted upside down with the big flange on the LH cylinder pointing down and unused. On the RH cylinder big flange is on the top and the oil pipe is using it.
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baldric
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Post by baldric on Sept 27, 2021 3:43:38 GMT
On the 4th image down here www.4930hagleyhall.org.uk/news/news.html the flange can be seen with the bolts not horizontal, so the oil feed hole is at the top, I guess at some point in its life, 1501 has had a swap of parts. Baldric.
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Post by Roger on Sept 27, 2021 11:06:21 GMT
On the 4th image down here www.4930hagleyhall.org.uk/news/news.html the flange can be seen with the bolts not horizontal, so the oil feed hole is at the top, I guess at some point in its life, 1501 has had a swap of parts. Baldric. Ah, I didn't read that correctly, I see what you mean now. Yes, I agree that it looks like it's have parts fitted that were borrowed from another locomotive. It's odd that they chose to use the oil hole in the big boss on one side, but not on the other. Maybe the casting on one side didn't have the hole drilled through from the large boss, so they decided to drill one on the opposite side in the right place.
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Post by Roger on Sept 28, 2021 13:20:00 GMT
Having chatted with Ed about his springing issues it's made me refocus on the experimental damping I want to try. This really needed to be designed into the axlebox arrangement from scratch, but as usual I have to start from where I am. The two mounting holes already exist in the frame for this purpose, but I couldn't settle on a sensible arrangement. Ideally I'd like to attach the rod to the top centre of the axlebox, but that's not feasible with the oiling arrangement. There are lots of shocks available for RC cars if you search for them on eBay, however they aren't really suitable because they are much too long and not stiff enough. Here's a YouTube video showing what's inside of them. They're very simple, and they rely on the stiffness of a bladder on top of the cylinder to distort when the volume of oil increases. You can change the bladder for different strengths to get more spring back. Some types have detachable pistons with different hole sizes to change the damping rate. Anyway, here's the sort of setup that I can squeeze in on the middle axle, using the Anti-Roll bar bearings somehow to attach the rod end which I haven't shown here. Hydraulic damper chassis mount by Georgia Montgomery, on Flickr This is what my first attempt looks like inside, the key things to note are as follows... 1) The top bladder is replaced by a piston, like it is on a car type. 2) The spring needs to be pretty strong because all of the upward force has to pass through it. 3) The springs are Belleville washers 4.2mm ID x 8mm OD x 0.2mm thick 4) The total travel of the main piston is 8mm, so the top piston will move 8/9=0.89mm since the shaft is 4mm diameter and the piston is 12mm 5) Each of the 18 springs could potentially move 0.1mm before going flat, so that's plenty. They could be set up as pairs to alter the force if necessary or by adding a spacer. 6) All of the RC Shocks I've seen use two O-rings on the shaft. They look like Silicone to me, they're very soft and either clear or Red. I've added two to the top as well. 7) You can't see it from this view, but there are two holes in the piston which is a pretty close fit in the bore. 8) You can buy a large range of Silicone Shock Oil with different viscosities to give the required rate. 9) The top piston has an M2 hole in it for bleeding the air out so it can be assembled. An M2 cap screw and copper washer seals it and conveniently just fits inside the springs. 10) I'll probably have to add an air hole in the top cap. So to give some idea of proportions, the top cap is 16mm diameter and the rod is 4mm. It needs to be a lot stronger than an RC one because it's moving over a short distance but with a fair amount of force else it's not going to do anything. My gut instinct is that this may well have a kilogram of load going though it to absorb any large undulations in the track. Hydraulic damper assembly by Georgia Montgomery, on Flickr Obvously the arrangement I've shown is only good for side to side waddling, it wouldn't have any effect on Porpoising. However, there's not enough room on the front axle to have the same arrangement due to the position of the lubricator eccentric. That's pegged to the shaft, so I don't want to move it. It would be possible to put a single one in the middle though, acting on a split bearing on the front axle. Come to think of it, there could be two, but they would be pretty close together. Anyway, I think it's interesting, and probably worth a try. It's been suggested that I try the locomotive first before going to all this trouble, but it's going to be a nightmare to do when it's all complete. In reality, it would never happen unless it was being stripped down. It's easy to take it off if it's not needed. My gut feeling is that it ought to make a big difference to how soft the locomotive can be sprung without it rolling around like a ship at sea.
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Post by chris vine on Sept 28, 2021 19:33:28 GMT
Hi Roger,
I don't understand what the spring and top piston are doing?
I don't think you are trying to make this into a spring to support the loco. Or are you? Or, is it just to take up the displacement of the piston rod entering the damper?
Also, surely there will be a tiny bit of leakage past the o rings on that piston and then the spring will just push the piston downwards until it has unloaded the spring.
Looking at the video you linked, I thought the bladder was just absorbing oil (as the piston rod takes up space, so that it could operate completely filled with oil with no air bubbles etc.
Maybe your O Rings won't leak??!!
Chris.
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Post by andyhigham on Sept 28, 2021 20:21:32 GMT
The top piston is to allow for the volume displaced by the shaft
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Post by Roger on Sept 28, 2021 20:50:09 GMT
Hi Chris, the top piston accommodates the extra volume that's displaced by the piston rod. Here are two YouTube videos that show the effect clearly. This one shows the same idea. You can see that the oil will cavitate unless there's enough positive pressure on it. The spring in my design replaces the gas in the commercial car units. The pressure in the hydraulic oil above the piston is all that can support the load on the piston. If you have no force pressing down on the top piston, the piston will get forced upwards because there's nothing to stop it. So basically, if you want to be able to transfer say 1kgf onto the damper rod, you must be able to transfer 1kgf onto the top piston and so on. You're absolutely right that there will be a force trying to return the piston to the bottom. I realised that I actually require almost 10mm of total travel, not 8mm., so I've had to massage the dimensions to suit. Here it is set at half travel. There's still more to do so knock the rough edges off, but I think this is practical. So the top forked piece pivots in the block above the horn. The bottom yoke transfers its force via the anti-roll bar, so that can actually move from side to side a little. Hopefully that won't be a problem. Hydraulic damper installation by Georgia Montgomery, on Flickr The inside looks like this. Hydraulic damper installation sectioned by Georgia Montgomery, on Flickr Chris may be right that this won't leak, but it will be a pain if it does. There will be some pressure on the seals all of the time.
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Post by Cro on Sept 28, 2021 21:11:49 GMT
Is this not the sort of thing you would try after seeing how it runs? Could be a lot of work for nothing? And if you fit it all now how would you ever know if it’s actually doing anything without taking it all off to make a comparison.
As interesting as it is from an engineering point of view to design and make something such as this I can’t see the purpose of it when it comes to a model?
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Post by Roger on Sept 28, 2021 21:29:51 GMT
Is this not the sort of thing you would try after seeing how it runs? Could be a lot of work for nothing? And if you fit it all now how would you ever know if it’s actually doing anything without taking it all off to make a comparison. As interesting as it is from an engineering point of view to design and make something such as this I can’t see the purpose of it when it comes to a model? Like I mentioned in the text, you can't realistically go back and retro-fiit this sort of thing without a lot of upheaval. It just wouldn't happen. Doing while it's a chassis, and piping etc can be routed around the parts isn't a problem. Taking it off is easy once it's done. The purpose it to allow soft springing without losing stability. It's been robustly argued that leaf springs are definitely superior to coil springs, and if that's true, any benefits are likely to be purely down to the slight damping they add. I saw Bill Perret's SPEEDY at Southampton rolling around like a ship on the ocean, and it was obvious that it would really have benefitted from some sort of damping. So there's evidence already that this can be an issue, and the only other way to resolve it is to increase the spring stiffness. That's all very well, but you sacrifice traction if you take that approach. So I'd argue that this isn't just an interesting techical exercise, it ought to have real practical benefits in terms of stability and adhesion. Experimenting is hugely enjoyable, and everyone gets to learn something valuable. It's never work for nothing when you've enjoyed the journey and pushed the boundaries. If nobody has tried this before, why not? It's such an obvious thing to try.
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dscott
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Post by dscott on Sept 28, 2021 23:41:49 GMT
And the Andover track is the perfect one to try her on before they adjust for track settlement. Our many journeys round the new extension proved that the E-Beast could keep up with the bounces and dips but our 2 trolleys couldn't and dropped off the rails, usually at the same place... After the tunnel by the SLOW sign!!!. Both rely upon a twisting frame for suspension. The smoothest track is the Tiverton one but I may be biased as I helped build it and some of the molds involved.
David and Lily.
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uuu
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Post by uuu on Sept 29, 2021 6:40:20 GMT
Is there room for it to be upside down, which might contain the oil better if it leaks?
Wilf
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Post by Roger on Sept 29, 2021 7:09:21 GMT
Is there room for it to be upside down, which might contain the oil better if it leaks? Wilf I think it could be fitted either way. It's under pressure all of the time, so if it leaks, it's going to spread out everywhere. It might be easier to mount the other way round though, it's certainly worth a look.
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Post by Cro on Sept 29, 2021 7:21:30 GMT
I saw Bill Perret's SPEEDY at Southampton rolling around like a ship on the ocean, and it was obvious that it would really have benefitted from some sort of damping. So there's evidence already that this can be an issue, and the only other way to resolve it is to increase the spring stiffness. That's all very well, but you sacrifice traction if you take that approach. But isn't that rocking part of the springing that's required to gain the adhesion? I have to admit I think most locos I know that put their power down better all rock to a certain degree leaf springs or not.
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Post by Roger on Sept 29, 2021 7:48:19 GMT
I saw Bill Perret's SPEEDY at Southampton rolling around like a ship on the ocean, and it was obvious that it would really have benefitted from some sort of damping. So there's evidence already that this can be an issue, and the only other way to resolve it is to increase the spring stiffness. That's all very well, but you sacrifice traction if you take that approach. But isn't that rocking part of the springing that's required to gain the adhesion? I have to admit I think most locos I know that put their power down better all rock to a certain degree leaf springs or not. I don't think the rocking helps, it's just a symptom of soft springing. The softer the springing, the more evenly the weight can be distributed over each wheel. I'll bring over my weighbridge one day, and you can see just how different the weights on each wheel can be. I think you'll be surprised. I've seen a factor of two on some of the locomotives I've checked, and that's got to hurt adhesion. It's bad enough on a level track, but stiff springing on anything but a flat track is going to have a big impact.
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Post by Cro on Sept 29, 2021 8:11:43 GMT
I've no doubt my B1 is awful when it comes to its distribution - actually I know it is as It sits down on the front axle and not the others, needs work.
I'm not convinced its an 'issue' that needs fixing necessarily but will be interested to see if there is any noticeable difference with the end result.
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Post by Roger on Sept 29, 2021 9:21:42 GMT
I've no doubt my B1 is awful when it comes to its distribution - actually I know it is as It sits down on the front axle and not the others, needs work. I'm not convinced its an 'issue' that needs fixing necessarily but will be interested to see if there is any noticeable difference with the end result. It's not necessarily an issue, but it's surely desirable to acheive the greatest amount of adhesion, especially since we seem to have ever more slippery Aluminium tracks. Slipping happens all the time in my limited experience, so anything that reduces that makes sense to me. I can fully understand why some people would find non-prototypical things like this offensive though. However, our track isn't prototypical either, it's way more uneven, and you have to address its effect, usually by stiffening up the springs.
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Post by Roger on Sept 29, 2021 9:37:14 GMT
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Post by Cro on Sept 29, 2021 9:42:17 GMT
I guess I don't see Ally as such a problem as other considering the work we do at Beech Hurst and loads we pull but then the track is extremely well maintained so clearly soft springing is all that is necessary in our case. You'll have to get it finished quick so we can see it working!
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Post by Roger on Sept 29, 2021 21:43:15 GMT
I've decided to make a prototype of this to see how it works out. Inverted damper installation by Georgia Montgomery, on Flickr This is the end cap, shown in red above. I've made it from PB102 because I don't have any SAE660. I think Brass would wear out too fast since this is going to handle a lot of load all the time, and the length of the bearing surface is pretty short. The thread is M11 x 0.75 (fine) which is a bit of an oddball, but one I've already got. The one at the other end is M14 x 0.75 (fine) which I've ordered at tap for. I've got M14 x 1 (fine) but it's not fine enough for the thin cylinder walls. Here I'm adding the spanner flats. 20210929_183717 by Georgia Montgomery, on Flickr The piston is a piece of Silver Steel parted off over size and over length after tapping the centre M4 for the piston rod. I'm using 4mm Silver Steel for the rod because it's strong and precision ground. I'll polish the part where the O-rings seal. The parted off disc is being held up against my standard M4 mandrel with a thread just protruding through the front. 20210929_214537 by Georgia Montgomery, on Flickr The piston will have a 0.5mm countersink in the thread so the piston rod can be made long and peened into it. I'll probably use Loctite too. I'll turn the OD when it's attached to the piston rod. 20210929_214835 by Georgia Montgomery, on Flickr
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