Material Recommendation?

Being the cheapskate that I am , I have decided to rework original rather than replace some of the parts on the 1939 H-D I'm rebuilding (not
"restoring" !) . Some of the parts I have decided to rework are the lower rockers on the springer front end (where the wheel mounts ...). More to the point , I need to decide what to make the rocker bushings from . The originals are steel , and just a bit softer than a knife blade . A file will mark it , but not deeply . The rocker studs seem to be mild steel , at least they machined easily . I am considering case hardening the wear surfaces ... bushings are cheaper than studs . The bushings will be about 1" OD X .875" long , with a wall thickness of either .150" or .165" , depending on which location they're in . I have very limited experience with material selection (unless you want to build some cabinets or a receptionist's desk ---) and have no idea what alloy would be best for these bushings . Anybody care to venture an opinion ? I will be making some bearing cups to replace the ball bearings in the steering neck with a tapered roller , and need some suggestions there also . Thanks !
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I'm sorry, but I really don't know much about the names of stuff on old tractors. Is it a wide front end, or narrow? Is this the part the wide front end pivots on, or is it the part teh narrow front end rotates around to turn the tractor????
in any case, brass is a common bushing material. It is soft, and functions well for places that are greased regularly, turn, but are not pounded on. So brass is good for bushings for the steering wheel shaft, but not so good for wheel bearings.
UHMW is used for bushings, but it is not as tough as brass.
Steel is used. Again, you need to grease it. Harder obviously. I'd use mild steel. The goal is the bushing material should be the softest material around so it wears out the fastest, instead of your shaft.
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Doug wrote:

Uhh , I think we missed a connection here . The bushings I'm making are for a motorcycle springer front end at the bottom of the forks . There are 3 holes in the rocker , 2 of them need to rotate a few degrees as the springs compress and extend . The 3rd is the hole the axle goes thru . I'm inclined after talking to a couple of folks to use 4130 steel , I can get it pre-hardened to 28-32 c (I think that's what he said) . With a case hardened pivot pin (or stud as Harley calls it) the bushing should wear and leave the studs intact ... which sounds good to me , cuz the studs are expensive , relatively speaking .
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oops. i was thinking tractor, you were thinking motorcycle!!!!!!!!!!!
hehe
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Bronce (not brass!) is always a good bearing material. But the stud running in it has to be hard. Case hardening is a good solution, because the hard skin doesn't have to be deep at all.

Free machining steel will do the job and help you in machining it.
HTH, Nick
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"Nick Mller" wrote:

The problem with bronze here is that these bushings get a lot of shock loads as the wheel rides over the road . I went to the only supplier in the area that services small accounts and got some 4140 bar stock . As supplied it's at about 28-32 c hardness , which should work OK in my application . Gotta find a local source for case hardening stuff for the studs , or order some from enco or somewhere .

I think I'll ask my buddy the machinist if he's got any of that hidden in his supply ...

I've learned a lot from lurking here , thanks so much for your advice !
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It's not the bushing that has to resist elastic deformation, it's the material _behind_ it. Look how thin crank shaft bearings are.
Nick
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"Nick Mller" wrote:

Sure thing , and you're right . My cue was that the originals were steel alloy . H-D had a reason for that ... so I'm doing it the way they did . BTW , crank bearings are usually at least 2" diameter , and run with an oil film . These are .674 and .699 diameter , and are greased . They also only rotate about 10 degrees max , so the load is very concentrated . I'll be posting some pics at alt.binaries.pictures.motorcycles.harley later today of the old and the new .
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Just to be pedantic: ;-)

There was a reason. Maybe without reason.

My example was only to show, that the bearing material itself doesn't have to be thick-walled.

The same is valid for bronce and steel bushings. :-) Generaly, steel (gliding) on steel without _pressurized_ oiling is deemed to fail. One exception coming to my mind is a CI-bushing.
Nick
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wrote:

an
There are tribology tables available that will show you which journal materials work with which bearings, at which loads and which speeds; wear ratios; performance with and without lubrication, etc.
From my diminishing memory, what I learned when I was reporting on this subject is this: Mild steel on mild steel is one of the worst bearings imaginable, at all but the lowest loads and speeds. OTOH, hardened steel on hardened steel is one of the best. Before rolling bearings were available for reasonable prices, hardened steel on hardened steel was used for the most demanding instrument and machinery applications, including ultra-precision grinders, at the highest speeds (then around 10,000 rpm for an internal grinder, for example).
The bronzes are next, and work-hardening bronzes that get really hard from work are the best of the bronzes. Aluminum bronzes and phosphor bronzes are tops; phosphor bronzes being the older ones. Manganese bronze is next.
Aluminum and brass are actually quite good at low loads. Cast iron is an excellent general-purpose bearing (bushing) material, handling quite high loads, but all bearing manuals I remember reading say that it requires twice the clearance of bronze. In applications where lubrication may fail, it is the preferred material.
Where dirt is a problem or where the bearing may have to comply with a less-that-rigid shaft, babbitt is the traditional favorite. It embeds dirt and, given a thick film of lubrication, it has little tendency to gall (it smears, but rather smoothly). Its specific wear ratio is poor, but that's the tradeoff.
Galling is what kills mild steel and yellow brass. Hardened steel journals running in mild steel bushings actually aren't bad if the loads are light and the lubrication is good. The best hardened steel on hardened steel bearings used no lubrication -- or, more accurately, they ran with dynamic air bearings, with about a 0.001" clearance or less, down to 0.0002", and had to run at high speeds because they dragged with air film around with them ("dynamic" and "static" lubrication mean the opposite of what we usually think).
Big breakthroughs occurred in bearings with, first, the Thinwall automotive bearings introduced by a British company in the early '50s; then with tri-layer bearings in the late '50s, and then with Honda's refinement of tri-layer tribology, which they introduced on their 4-cyl. 750. It actually had less friction than their earlier roller bearings.
It ain't sexy, but tribology can be really interesting. A lot of the information about plain bearings that was gained at great expense, empirically, is lost in the general literature and has to be dug up from old engineering texts. But automotive bearing technology is very refined and makes a good jumping-off point for understanding these bearings, and it is the subject of continuing research and reporting.
-- Ed Huntress
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Ed Huntress wrote:

And that , sir , is *just* what I needed to know . Ya gotta remember , we're talking 30's technology here . Which means that the ones I pressed in today gotta come back out for heat-treat . What a great excuse to build a small gas fired forge ! Been doing some research , and there are some very simple and relatively cheap designs out there . Already got the wife convinced ...
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<snip>

we're
today
It probably will help.

We're all very creative at coming up with such excuses. It seems to be one of our greater collective talents.
'Sounds good to me, but my wife recognizes transparent ploys at 50 paces...
-- Ed Huntress
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OK. Hard steel on hard steel works. But, as you said, with little load and high rpm. Not what you find in the fork described. I still would not do it _now_, even if H.D. did it _then_. It was in the 40's when bearing bronces made a big evolutionary step. So, it was _past_ H.D.'s decision for steel on steel.
Nick
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wrote:

bad
because
I have no idea what the "fork described" is, nor who made a steel-on-steel decision. I just saw that thread drawn out much longer than it should have taken, with no apparent resolution, so I dumped a load of bushing-material data the way you might dump powdered lime on a magnesium fire. <g>
Yes about the '40s. Implementation mostly in the '50s.
-- Ed Huntress
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Ed Huntress wrote:

It was about the springer forks on my '39 Harley WL . I'm reworking the rocker links at the bottom , they were bushed with steel , and use steel pivot studs . Hey , even aftermarket replacements are steel ...
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<snip>

Aha. Well, without looking it over, I dunno. They're probably steel because steel is cheap. Whether steel is the right material for the job is another question.
It sounds like strength, and the ability to handle high specific loads, is more important than actual bearing properties. Steel may be the right material but I wouldn't venture a guess without looking at it up close and getting a sense of the loads involved. I haven't seen a suspension like that for a lot of years. <g>
-- Ed Huntress
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Some people get confused about the difference of a HD and JD.
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wrote:
snip

snip
You can't just use any bronze for making a bushing, right? I thought it had to be Aluminum-Nickel-Bronze or similar. I thought some types of bronze were too soft for bushings. I made a bushing for a friend once for his tractor and the stock he brought me was used to machine knuckle bushings for Boeing landing gear. Very hard stuff and was Aluminum-Nickel-Bronze. I also made some bushings out of brass for another friend for the hinge pins on the driver's side door on an old Camaro. He said they didn't last a year before they wore through. So you're right that Brass is no good.
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I'm glad your rebuilding not restoring. While restorations are beautiful it's better to ride them. Karl

rather
the
will
least
...
of
opinion
.
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Karl Vorwerk wrote:

Too much of the original is gone , the AMCA calls my bike "a collection of parts , not a motorcycle" . Fine with me , I can have every bit as much fun on a collection of parts as I could on a "motorcycle" . My main problem has been that many parts , especially for the tranny , are no longer available . I bought my lathe to make them ... as I'm doing with the springer bushings . And it's so much fun , to boot !
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