uuu
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Post by uuu on Mar 23, 2013 10:18:15 GMT
In another thread, Julian mentioned that he had felt wipers for distributing axle lubrication. I'm attracted by this idea. It's also been suggested to me that I could put a circular groove in the axle bush to act as a reservoir.
So I'm inviting suggestions. I'm making the axleboxes for Jessie now. The drawings show split boxes of bronze, but I'm not doing mine split. And mine are cast iron, with a bronze bush. There will be an oil well on the top face (as drawn), with holes to take oil down to the side faces and onto the axle. So should I mill a pocket in the bush for a wiper, how big? Or a groove, how wide? Or what else? Bush is 7/8" ID, and 1.125" long.
Wilf
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Post by Deleted on Mar 23, 2013 10:57:04 GMT
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jma1009
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Post by jma1009 on Mar 23, 2013 11:02:18 GMT
hi wilf,
what OD are the bronze bushes?
ive never bothered with oilways for the horncheek/axlebox slots... in miniature they seem to retain a film of oil.
never have the oilway from the reservoir going into the axlebox bore at its top ie 12 o'clock...it should be 10 o'clock or 2 o'clock if that makes sense. in fact in fullsize a better method is to have the felt pad used as a reservoir with oil feed lower down.
my felt is quite thick springy stuff as used in organ building/restoration. i think ive still got some if you want. with a split box and separate keeps it is quite easy to assemble the boxes so the felt doesnt get caught on the axle which might be the case if you try sliding the axles through the bore.
oil grooves need to be quite small and not 'overdone' and can be done with a scraper or something to act as a scraper.
i think the extra work in making split boxes is well worth while. there are some pics of the ones i made for STEPNEY on my BOXHILL thread.
i also think that lots of miniature designs have axlebox oil reservoirs of insufficient size.
i never use motor oil for oiling the motion or axleboxes preferring to use the proper stuff.
if you case harden the axle journals or use a harder grade of steel for the axles than BMS then arguably a better method is to have the journals run direct in the cast iron, so long as the cast iron is a good grade such as meehanite.
cheers,
julian
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JDEng
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Post by JDEng on Mar 23, 2013 11:09:14 GMT
Wilf,
Oil grooves in bushes or brasses are normally put perpendicular to the movement of the journal or shaft, the idea being to avoid creating a ridge on the shaft or journal due to wear. In other words, you would put a straight groove running across an axlebox brass or big end bush (in the same direction as the centreline of the axle); you would put a circular groove around the whole of the inside of gland follower on something such as a piston rod where the motion is "in and out" rather than circular.
John.
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uuu
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Post by uuu on Mar 23, 2013 11:24:55 GMT
Hi, Julian. The bushes are 1" OD, and have a step on the outer end. I considered running direct in the cast iron, but have a notion that I could replace the bush in future and, if I didn't want to take the wheels off, make split-bush replacements. In any event, I'm not expecting to run so much that I get that far. I'm also encouraged that Super Simplex axles feel good even after a hard life.
The axles are old car half shafts, a "very superior material" accoding to Ken Swan. They don't machine as easily as BMS, the chips come off blue, if you run a bit too fast.
The Jessie reservoirs are quite large (U-shaped 1/4" wide and 3/16" deep) and the feeds to the axle are at 10 and 2 o'clock.
Thanks to Julian and Pete for the info so far- I shall read up on the Don Young design.
Wilf
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Post by albert on Mar 23, 2013 15:50:55 GMT
Hello Wilf,
Why are you making cast iron bushes and then fitting bronze working surfaces, when a cast iron to steel axle is a much better working and wearing surface??
Why "o" why do lots of loco builders (and others) use bronze for bushes??
Albert
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Post by ejparrott on Mar 23, 2013 17:00:17 GMT
beats me..iron for all of mine...
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Post by Deleted on Mar 23, 2013 17:05:30 GMT
beats me..iron for all of mine... being relatively new to all this I have wondered this too, I don't mean for this thread in particular but in general, I had assumed that it was because CI axle boxes with Steel axles was old school and things had moved on. I have and will be following Don's instructions to the letter for 4472 which states CI axle boxes/ journals with silver steel axles. It's good to read threads like this though, I'm not saying there's a right or wrong......just that it helps to see how others do things...  Pete |
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Post by ejparrott on Mar 23, 2013 17:35:15 GMT
Cast Iron has a quirk where by running it with a steel shaft, albeit a bit harder than EN1 or 3, makes a beautiful bearing surface, and when well soaked with oil and beautifully polished, it will run just as freely as a roller bearing. I did a lot of research into bearings for my Manning Wardle, before settling back on the iron boxes it was originally intended to have.
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Post by Deleted on Mar 23, 2013 19:00:57 GMT
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Post by Deleted on Mar 23, 2013 19:22:02 GMT
Hello Chaps------------- in general, full-size loco. practice is to have an oil reservoir in the bottom of the axlebox with a worsted pad sprung -loaded onto the bottom of the axle...the oil being drawn around by the axle rotation itself....The bottom half of the assembly doesn't make contact with the axle (unlike the majority of our "minatures" ) ahh.. exactly as is Don's design for the tender axle boxes on Doncaster . I did question this with a fellow ME who was also building Doncaster , long before joining this forum. he explained that all would become clear once the parts were fitted together as to me i thought it would all full apart or that with all of the weight only running on the upper part of the journal ( there is no lower part) it would wear out. Having now built the tender I can see how it all works and how with the oil pad sitting in it's tray will always be well lubricated. I have to say this method has grown on me, more so since it's as to the prototype which is how I want to do things. The loco itself is not to this design having split axle boxes.. again I believe the same as the prototype. Regards Pete |
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Post by cplmickey on Mar 23, 2013 19:40:47 GMT
I'm in the middle of making split boxes for my Dart and these will be the first ones I've made with delt pad oilers. Does it matter what sort of felt you use in the reservoir?
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Post by fostergp6nhp on Mar 23, 2013 20:32:01 GMT
Hello Chaps------------- in general, full-size loco. practice is to have an oil reservoir in the bottom of the axlebox with a worsted pad sprung -loaded onto the bottom of the axle...the oil being drawn around by the axle rotation itself....The bottom half of the assembly doesn't make contact with the axle (unlike the majority of our "minatures" )... The crown generally has a white metal lining within a bronze pad, itself pressed into the box top...Personally I would have a split box on my model....it'll save a whole lot of grief later when you want to renew the crown area / box as a whole.......and you won't have to part your wheel assy either !!  Look at pictures 7 & 8 |
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Post by lennard1200 on Mar 23, 2013 21:13:52 GMT
Can you use a Stainless shaft with cast iron ?
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uuu
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Post by uuu on Mar 23, 2013 21:55:56 GMT
I'm pleased with the variety of responses this question has generated - thank you all. Keep them coming.
I was very tempted to go for straight cast iron, and I have no doubt it would work very well. But I'm also happy that bronze will work - Jessie is drawn with bronze, and it's an established design. Even though I've changed it a bit!
I like the idea of a pocket with a sprung felt in it, and am drawing up an option with a drilled hole up from the bottom, with a screwed plug. This would be linked with small driilings from the reservior on the top. This gets round Julian's concern that the felt would get snagged with the axle on assembly, as the felt and spring would be inserted after the primary assembly. Does this sound feasible?
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jma1009
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Post by jma1009 on Mar 23, 2013 22:17:18 GMT
hi cplmickey,
ordinary felt (as used in hats and and used for making soft toys etc) is too thin and compressed. ask your church organist who repairs the organ and see if you can get some thick coarse stuff. ive never heard of anyone using worsted pads being used in miniature but by all means give it a go too!
lennard1200,
stainless can do strange things as a rotating journal material. ive no knowledge or experience of using it as such with cast iron, but i was told many years ago by an experienced marine engineer not to use it with hard drawn phosphur bronze. ive used it ok for rear axles on 2 locos as wilf knows (he gave me the stainless!) with gunmetal axleboxes, though it was pretty tough stainless...not the softer freecutting non magnetic stuff.
the main problem with ordinary cast iron is the variable quality and the wear on tools and the need for sturdy machines. when making split axleboxes in gunmetal or phosphur bronze milling and boring and drilling and reaming for the pins is relatively easy compared to cast iron. it is well worth obtaining meehanite cast iron if making cast iron axle boxes . i was lucky enough to be given some very useful offcuts of meehanite from a friend who was restoring a fullsize Burrell Roller and was replacing all the bearings.
the standard Churchward axlebox had the oil fed into the crown with a worsted pad in the keep. i understand that later most of these axleboxes were modified to have the oil fed to the keeps. if you have a look at GWR KING 6023 you can see one of these keep oiler pipes and where it broke off.
for tenders i make a plain blind bush and shove some graphite grease in before adding the wheelsets. i havent touched any tender axlebox bearings on my own locos for 10 years.
cheers,
julian
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Post by Deleted on Mar 24, 2013 19:22:20 GMT
Hello Chaps------------- in general, full-size loco. practice is to have an oil reservoir in the bottom of the axlebox with a worsted pad sprung -loaded onto the bottom of the axle...the oil being drawn around by the axle rotation itself....The bottom half of the assembly doesn't make contact with the axle (unlike the majority of our "minatures" )... The crown generally has a white metal lining within a bronze pad, itself pressed into the box top...Personally I would have a split box on my model....it'll save a whole lot of grief later when you want to renew the crown area / box as a whole.......and you won't have to part your wheel assy either !! Look at pictures 7 & 8 ----------------------------------------------------------------------- Thanks for posting these EXCELLENT photos..They do indeed show just what I was referring to... The small hole in the top of the crown is actually threaded and takes an eye-bolt for lifting purposes....As well as a volunteer on the SVR for over 25 years I also became a Self-Employed contractor and have indeed re-metalled and machined those very type of boxes.....In this current snowy climate it's hard to remember HOT----- but it was just that !! ie HOT WORK !!!!!!  |
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Post by Deleted on Mar 24, 2013 22:01:18 GMT
Notice the slot in the top of the underkeep - that takes the felt wiper pad. The earlier Churchward underkeep was open-topped and carried a large rectangular worsted pad (an Armstrong oiler in other words).
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Post by lennard1200 on Mar 24, 2013 22:12:57 GMT
Thanks Julian,
I have 1 1/8" Stainless that I get for a good price & it machines very well, so was pondering on wether to use it for axles for a 7 1/4" Chaloner type loco I'm building which will have CI or steel axle boxes.
Leonard
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Post by lennard1200 on Mar 24, 2013 22:16:10 GMT
further.....ex boat prop shafts so was meant to go round......
Leonard
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