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 !
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.
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.
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 .
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 !
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 !
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 .
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.
Well shit Snag, if yer really a cheapskate, buy these (scroll down a ways):
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According to my math, that's only $9.00 per for all four. I sure as hell couldn't make 'em for less than that.
And why do ya want to do that? Those old ball bearings last for 100's of thousands of miles. I switched to tapered rollers in my '37 Knuck once and went back to ball bearings after about 30k miles. If yer bound and determined to go with tapered anyway, they're (cups) available from Ted's V-Twin for *way* less than you could make 'em too.
That'll be 2 Coors twice and eight bucks for Snarl . The link itself is worth more than that !! Actually , two feet of 4140 (1" and inch a quarter) and a foot of 1" ampco
18 cost me less than the bushing set . Part of the reason I'm making them is because the studs were worn , and I turned them down just to clean-up , rears at .699" and fronts are .674" now . The other part is the personal satisfaction of saying I did it myself ... Got the set for the sprung leg almost made already , just gotta turn a few thou offa the outside to get a .001" tight press fit . I'll hone them a bit after they're pressed in for final fit . Got the others roughed on the same piece of stock , just a few passes with a boring bar and finish size the outside . Do you know if the studs were originally case-hardened ? These seemed pretty soft , machined easily , but they were worn . Got a new top race coming , I think that'll be everything but the balls - I'm taking your advice on that one . My goal for this winter is to get that chassis rollin' - maybe then I'll be more motivated to get it finished . Been sitting out there since '98 , way too long .
Ok, that I'll buy. Looks like they were pretty hammered. Any sign of grease in/on them when ya disassembled it?
I can't say with 100% accuracy, but I'd bet they were. In any event, you definately want th' studs harder than th' bushings. And they should be hit with a grease gun every 1,000 miles. I check clearances on my rocker studs every winter just to be sure.
A good way to prolong steering neck bearing life is to not always park with th' front end flopped over in th' same position... usually pointed left. Alternate how you angle th' front wheel when parked, there's a lot of static weight and wear if it's always th' same.
Hey, at least yer still playin' with it and having some fun... nothing wrong there.
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.
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 ...
There was some crusty black stuff on the outside that might have been grease once ... The bushings had worn to the grooved shape of the studs , almost thru in one case . Whoever the last guy to run this machine was , I don't like him . Dad got it in '52 , with a broken tranny countershaft . Never got it runnin' , never rode it .
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.
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