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Post by michaelfive on Feb 28, 2021 9:40:55 GMT
Hi Michael, I don't know if you are planning to loctite the piston threads when you assemble them, this was the original spec and will prevent them coming loose in the future. I agree with your comment re the lubricator appearance, the replacement I have made is a fair bit smaller and has enabled me to make a lid which looks a bit more like the original. I believe there have been successful working versions of Wakefield lubricators in this scale although I haven't seen one, but perhaps if anyone has details or a picture of these, they would be kind enough to share them. Regards Mike Lubricator Jan 21 by Mike Sanderman, on Flickr I indeed used Loctite to fix the piston rods to the pistons before I did the finish cut to the outer diameter of the pistons, with the rods fixed in the chuck. Nice solution with the scale lubricators on the lid!
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Post by michaelfive on Feb 28, 2021 10:36:40 GMT
It's again been a while since my last post. I was busy with other stuff but recently found the time to finish the pistons and the valves. As I mentioned in an earlier post, I found different valve stroke on the two valves of the engine, without finding the source of the difference. Therefore I disassembled the motion, the cylinders and the pistons completely and compared every part before remounting. This is also one of the reasons why it took a bit longer to finish the pistons. Nearly every bit I compered was different. Most of the differences I found had no impact on the functionality but since I knew that there was a difference, I had to correct it. I don’t understand how the two sides of the loco could be that different. If this reflects the manufacturing quality of Modelworks or if the previous owner / builder started to adapt some of the parts?! Some examples: The thickness of the front piston covers were 0.8mm different, the depth of the hole for the piston gland packing 2mm. The gland packing cover had different thread size… and so on… None of the differences I spotted so far was the reason for the difference in valve stroke. Nevertheless, I gives me a good feeling that I know that the two sides of the engine are equal. (Within reasonable tolerances) Since I had to rework most of the bits gently, I also had to repaint a lot. I forgot to make pictures but there is anyway not much to see. Back to the pistons: Inspired by this article I made preloaded (compressed) piston rings out of graphite loaded ptfe. But instead of clupet rings, I decided to go for two simple split rings per groove. During assembly I made sure that the openings of the rings were 180 deg. offset. I don’t think chances are high that the rings are going to rotate and align with the openings overlapping. But only time will tell… I’m happy with the low frictions of the pistons an tested on compressed air, they seem really airtight.
Left: Old Piston, Right: New Pistons (SST Piston Rod, Aluminium Piston, 25% Graphite loaded PTFE Piston Rings)
With the valves in central position (shut) I can push and pull the pistons and the air in the two chambers force the cylinders to go back in their initial position when releasing. But when testing the cylinders I found leaks in the vlaves. The first leak path was obvious: Since I allowed space for expansion between the brass valve body and the ptfe tyres of the piston valve, there was a leak path between the said two parts. I made groves to the brass valve bobbin and added silicone o-rings. The other leak path was between the valve liner and the cylinder casting of one valve something I already tested before but obviously not that good. When disassembly the particular valve liner I worried again the I had the same problem as Mike found on his engine: The oval opening of one of the cylinder inlet bore was offset I taught it might overlap the O-ring of the valve liner.
But turns out that it’s just spot on. Refitting new O-rings cured the problem.
Next step will be reassembly the valve gear. (again) Wish you all a happy and relaxing Sunday!
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Gary L
Elder Statesman
Posts: 1,208
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Post by Gary L on Mar 1, 2021 1:59:05 GMT
[snip] With the valves in central position (shut) I can push and pull the pistons and the air in the two chambers force the cylinders to go back in their initial position when releasing. But when testing the cylinders I found leaks in the vlaves. The first leak path was obvious: Since I allowed space for expansion between the brass valve body and the ptfe tyres of the piston valve, there was a leak path between the said two parts. I made groves to the brass valve bobbin and added silicone o-rings. The other leak path was between the valve liner and the cylinder casting of one valve something I already tested before but obviously not that good. When disassembly the particular valve liner I worried again the I had the same problem as Mike found on his engine: The oval opening of one of the cylinder inlet bore was offset I taught it might overlap the O-ring of the valve liner.
But turns out that it’s just spot on. Refitting new O-rings cured the problem.
Next step will be reassembly the valve gear. (again) Wish you all a happy and relaxing Sunday! If I understand correctly, you have put silicon O-rings to seal your piston valves. I hate to bear bad news, but you might be wise to change them while it is still easy to do it. Silicon rubber is not good for a sliding seal at the best of times, but when passing over the valve ports you can expect them to be shredded to bits rather quickly. All is not lost though. Turn up some valve rings out of that graphite-loaded PTFE. You might need a slight adaptation to your valve bobbins to get them on, but they will last far longer than silicon rubber. Do remember though, that PTFE expands rather lot, so once run in you won't get a good seal when the engine is cold. This is a trivial inconvenience as they warm up to working temperature (and size) within seconds of opening the regulator. I speak from good experience with ordinary PTFE valve rings; the expansion characteristics of graphite-loaded PTFE might not be the same. Hope this helps Gary EDIT Aplogies if I have misunderstood. I see you refer to"PTFE tyres". Some people do indeed use silicon O-rings to press PTFE rings against the cylinder wall; a different thing entirely, and perfectly satisfactory I believe.
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Post by michaelfive on Mar 27, 2021 17:56:24 GMT
If I understand correctly, you have put silicon O-rings to seal your piston valves. I hate to bear bad news, but you might be wise to change them while it is still easy to do it. Silicon rubber is not good for a sliding seal at the best of times, but when passing over the valve ports you can expect them to be shredded to bits rather quickly. All is not lost though. Turn up some valve rings out of that graphite-loaded PTFE. You might need a slight adaptation to your valve bobbins to get them on, but they will last far longer than silicon rubber. Do remember though, that PTFE expands rather lot, so once run in you won't get a good seal when the engine is cold. This is a trivial inconvenience as they warm up to working temperature (and size) within seconds of opening the regulator. I speak from good experience with ordinary PTFE valve rings; the expansion characteristics of graphite-loaded PTFE might not be the same. Hope this helps Gary EDIT Aplogies if I have misunderstood. I see you refer to"PTFE tyres". Some people do indeed use silicon O-rings to press PTFE rings against the cylinder wall; a different thing entirely, and perfectly satisfactory I believe. Dear Gary
Thanks for your input. My description was probably a bit confusing. The loco has brass valves sleaves push fitted in the cast iron cylinder block. There are silicon rubber O-rings between the sleaves and the cylinder block in a static application. Those O-rings seal the exhaust form the live steam ports. The engine was furthermore designed with brass valve bobbins with brass split piston rings. This setup had a really bad seal and a lot of friction. So I reworked the original brass bobbins to take PTFE "tyres". The “tyres” are in contact with the valve sleaves and make the dynamic seal. But since PTFE expands a lot when heated I had to leave some room for expansion between the bobbins and the tyres. The inner diameter of the tyres is 0.3mm larger than the outer diameter of the brass bobbin. This created a leak path that I had to seal with additional O-rings, again in a "static" application. Unfortunately I forgot to take a picture of the setup. But the tyres and the bobbins can be seen in a picture earlier in this thread. I just added some groves in the seat of the brass bobbins later to take the O-rings.
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Post by michaelfive on Mar 27, 2021 18:24:42 GMT
I little update: After fixing the seal of the valve sleaves i reassembeld the motion and the valve gear and set the cranks by this method: www.jghtech.com/assets/applets/LFLSRM-Setting-Eccentric-Crank-current.pdfI hoped that resetting the eccentric cranks will fix the problem of the different valve travel of the two valves. That was unfortunately not the case. Nevertheless, i couldn’t wait to see if the new valve bobbins and the new main pistons work. So I made an initial setting of the valves and tried it on compressed air. I was surprised how well it worked! The loco runs in forward and in revers gear down to approx. 15psi. I have no experience but, think that this is pretty ok?! Notching back in foreward is possible but the more I notch back the more non harmonic the motion gets.. Notching back in reverse is much worse. I will try to upload a video. I tried to improve the motion by adjusting the valve on the spindle while running but could not make a real improvement. So I once more tried to find the reason for difference in valve travel. I measured the valves in full forward, in mid gear and in reverse in order to compare. But every time I remeasured I got little different results. I think to having found the cause in the play between the radius rod end the links. So next step is to make new die blocks and pins for the radius rod!
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oldnorton
Statesman
5" gauge LMS enthusiast
Posts: 710
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Post by oldnorton on Mar 27, 2021 19:34:54 GMT
Back to the pistons: Inspired by this article I made preloaded (compressed) piston rings out of graphite loaded ptfe. But instead of clupet rings, I decided to go for two simple split rings per groove. During assembly I made sure that the openings of the rings were 180 deg. offset. I don’t think chances are high that the rings are going to rotate and align with the openings overlapping. But only time will tell… I’m happy with the low frictions of the pistons an tested on compressed air, they seem really airtight. Hello Michael Following your progress with interest so I do hesitate to offer the following thoughts: The 'probably best' way of using PTFE rings on a piston is to fit o-rings underneath. These exert just enough pressure to keep the ring face in contact with the bore. The author of the link you give called 'Artisan' seems to be relying on the limited elastic nature of filled PTFE to maintain a pressure on the cylinder wall. Yes it will do that for air tests, and possibly a few times for steaming, but after a few thermal cycles will it still keep all of the ring pressed against the wall? I cannot see that filled PTFE can be considered a perfectly elastic (spring) material like cast iron. Certainly, you can test the rings and see how they perform, or modify the pistons now to simply fit o-rings under if it is all still unassembled perhaps? Norm
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Post by michaelfive on Mar 28, 2021 6:28:03 GMT
Back to the pistons: Inspired by this article I made preloaded (compressed) piston rings out of graphite loaded ptfe. But instead of clupet rings, I decided to go for two simple split rings per groove. During assembly I made sure that the openings of the rings were 180 deg. offset. I don’t think chances are high that the rings are going to rotate and align with the openings overlapping. But only time will tell… I’m happy with the low frictions of the pistons an tested on compressed air, they seem really airtight. Hello Michael Following your progress with interest so I do hesitate to offer the following thoughts: The 'probably best' way of using PTFE rings on a piston is to fit o-rings underneath. These exert just enough pressure to keep the ring face in contact with the bore. The author of the link you give called 'Artisan' seems to be relying on the limited elastic nature of filled PTFE to maintain a pressure on the cylinder wall. Yes it will do that for air tests, and possibly a few times for steaming, but after a few thermal cycles will it still keep all of the ring pressed against the wall? I cannot see that filled PTFE can be considered a perfectly elastic (spring) material like cast iron. Certainly, you can test the rings and see how they perform, or modify the pistons now to simply fit o-rings under if it is all still unassembled perhaps? Norm Hi Norm You may have a point here: The filled PTFE is not so elastic, the spring pressure on the cylinder walls is just sufficient to give an initial sealing for the air or steam pressure to do its job. But i don't now if that is still the case after a couple of heating and recooling cycles. But as you suggest I could just deepen the cylinder grooves and add O-rings underneath the piston rings. The only drawback is that it will increase the friction between the rings and the cylinder walls. Since the cylinders are already assembled, i will reconsider this after i steamed the engine for the first time. I hope to come to this point soon! But with every bolt i remove, i find another hidden secret that needs attention. Thanks for your advice, Michael
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Post by michaelfive on Jan 2, 2022 7:59:11 GMT
It's been a while since my last post. I didn't spend a lot of time in the workshop during the last summer, but restarted the work this fall. Since my last post, I finished the pistons and the valves and made some fixes here and there. I try to show you the progress with the help of some pictures: One safety valve was missing, thus I had to find replacement valves. Since the boiler bushes were not soldered in at a right angle, I made decided to make some adapters to compensate the angle. Thus, I had to find some valves with a smaller thread than the one of the bushes. I found some suitable valves at a local supplier (Holzapfel Winterthur).
I made kind of caps to make the valves look like express type safety valves. Unfortunately, the diameter of the valve body is a bit too small, so the proportions do not look right. I will make a sleeve and press the valve body in later on.
At least the valves are now aligned with the chimney.
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Post by michaelfive on Jan 2, 2022 8:07:37 GMT
I removed all the copper pipes, that were strangely routed and kinked at many places, then I remade the whole pipework of the loco and cleaned and fixed all the valves (boiler clack, blowdown, check vales)
Also, the injectors were descaled and repainted.
In the picture above the pipework in the cab can be seen. I also repainted the interiour of the cab, and installed a wooden floor. Windows are still missing. Below a picture of the cab before the rework:
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Post by michaelfive on Jan 2, 2022 8:23:53 GMT
When I had the loco upside down to fix the axle pump and to remove the wheels for repainting, i decided to change the automatic drain cocks for Bowden operated ones:
The bowden cable is routed in in a copper pipe to a lever in the cab. Pulling the bowden works fine, but for pushing it back i had to install an spring. Unfortunatly i forgot to takea picture of the bowden mechanism.
The axle pump was not working properly, the pump was sealed with kind of yarn packing on the cylinder and leaking a lot. I made a grove to the piston insted and installed o-rings suited for dynamic operation instead.
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Post by michaelfive on Jan 2, 2022 16:01:14 GMT
I didn't like the look of the original Modelworks expansion link brackets, since they were just cut out of a steel sheet and completely flat. So i used my small hobbyist CNC mill to make new brackets with a more realistic "3D" appearance, that is closer to the prototype. The brackets were made out of two pieces and soldered together due to the size restrictions of the hobby mill.
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Post by michaelfive on Jan 2, 2022 16:11:49 GMT
As i mentioned earlier in this thread i was not happy with the bulky mechnical lubricator. I could not find scale wakefield lubricators. But i found two "over stock" 1" lubricator for a good price so i decied to take the occasion and buy those. It's much closer to the prototype and i'm happy with the compromise.
The lucbricaters a fixed to a mounting bracked, and not to the running boards. this allows me to remove the running boards without the need to disconnect and remove the lubricators.
I also remade the pipes to the steam chest. (BTW: The pipe in the background is not kinked, its just a reflection in the picture)
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Post by michaelfive on Jan 3, 2022 16:02:01 GMT
The blower tube needed attention since it was was not properly fixed and leaking. As I had to remove it, I decided to give the "elbow" piece at the smoke box a more authentic look. The Modelworks "elbow" was just a block with two holes drilled in 90°. Since I had no suitable elbow piece at hand I grabbed the existing block with the chuck and turned one side round. The the other side to form an "elbow".
To fiix it t the smoke box i then silver soldered a flange to it.
Before:
After
I furthermore filed two additional flanges for the other side of the pipe, and adapted the block that connects to the steam pipe from the cab. Not really close to the prototype but still more detailed than the Modelworks original pieces. Well, most of the time i'm satisfied when I compare my rework with the state the engine came to me. As long as, I don't it compare it with the high standard of work that is often displayed on this forum! Otherwise, the satisfactions turns quickly into disappointment
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Post by michaelfive on Jan 4, 2022 12:37:06 GMT
After all the small modifcation and fixes, I set the excentric cranks using the method described in the linked document.
www.jghtech.com/assets/applets/LFLSRM-Setting-Eccentric-Crank-current.pdfI then adjusted the valves on the valves spindles by listening to the air blown out at the drain cocks, when rotating the wheels by hand with the valves connected to compressed air source with low pressure (0.1 Bar) The valves are just temporarly fixed to the spindle since i'm not yet sure if i got the timing right. Once I'm sure I will use Loctide to secure the valve bobbin on the spindle. Here is a video of the engine running on compressed air at 1 Bar. (14 PSI). As you can see, it runns in foreward and in reverese gear and notches back a little bit at that pressure. With more pressure i can notch it back a bit more. In full reverse and full foreward it runs below 10 PSI. youtu.be/3x1WcIy4Jo0Do you think that this looks ok so far?
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don9f
Statesman
Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 960
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Post by don9f on Jan 4, 2022 17:50:42 GMT
Looks and sounds pretty good to me....well done!
Regards Don
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oldnorton
Statesman
5" gauge LMS enthusiast
Posts: 710
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Post by oldnorton on Jan 4, 2022 18:19:11 GMT
Yes Michael, the fact that it is running like that on 10psi and picking up in forward and reverse all looks pretty good. You have done a nice job.
The precise mechanical balance of the valve events can be judged from the balance of the exhaust beat sounds, using your ear and listening to the blast from the chimney. You want to hear a nice smooth one-two-three-four with all the numbers at equal emphasis. If you hear something like one-ooopffh-three-four that tells you that one of the events is weaker or out of time. You can hear the same thing on full size engines that are struggling.
Also when you are in mid gear, stopped but with 10psi on, you ideally want to hear nothing comings from the exhaust.
Norm
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Post by michaelfive on Jan 5, 2022 19:30:00 GMT
Dear Don and Norm
Thanks for your positive feedback.
I have to admit, that i'm totally unable to hear if the engine has equal beats.
I'm actually the guy, who claps loudly off beat, when everyone else claps along a simple song; The guy who dances without any sense for rhythm in a dark corner of the danceflor...
I'm thinking of putting a microphone into the chimney to record the puff puffs... This would allow me to precisely analyze the sountrack on my computer.
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Post by michaelfive on Jan 22, 2022 16:04:06 GMT
I'll leave it as it is for the moment. Next the rusty tender needs some attention: I would like to use the tender hand pump for a hydraulic test of the boiler. Before i can use it, i need to seal the leaky tender tank and sort out the strange pipework.
Unfortunately, I forgot to take a picture of the tank itself. The tender just holds together with nuts and bolts and is not soldered. It was sealed by the previous owner with some rubber like thing, that was smeared into the corners. It hasn't only leaked but also looked awful. Fortunately, it didn't stick well to the brass so I could easily remove it:
I already reworked the handpump: Reamed the cylinder and changed the o-rings on the piston. Changed the brass bolts on the handle linkage that were too small, to SST bolts and nuts of proper size. The handle is now free of play. It feels much better when pumping.
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Post by michaelfive on Dec 17, 2022 5:57:52 GMT
Dear Gentleman
After a summer with a lot of other projects i returned to the workshop lately. I'm more or less done with the tender and would line to perform a hydraulic test of the boiler. I have a question regarding the water in the boiler. Can i leave it in the boiler for a while, or do i have to drain it right away to prevent from scale and oxidation? I wonder how that is normaly handled? Do you blow down the boiler after each run? Do you add any additives to prevent from scale?
Thanks for your inputs,
Michael
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Post by steamer5 on Dec 17, 2022 7:32:17 GMT
Hi Michael, Without going back on your thread….. copper or steel boiler? How long between steaming? Scaling is due to heat & concentration of dissolved solids in the water, principally calcium & magnesium salts….. the salts are left behind when you boil water, check your jug at home. Oxidation is due to dissolved oxygen in the water feed to the boiler, leaving the water in the boiler for an extended time in my opinion isn’t a good idea. Yes it’s possible to add chemicals to help with scaling & oxidation, bound to be able to find it online….. getting it delivered might be a bit of a challenge! My preference, my boiler is copper (would do the same on steel) is after running allow the boiler pressure to drop (having dropped the fire) away to say 30 psi….. not a hard & fast pressure…. & blow the boiler down after each days running….. if you use area has hard water then blowing down during a days running should be considered.
Seeing your location there is a model engineering club in your area, & having visited the club in Zurich the guys there would be able to give you first hand help
Cheers Kerrin
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