swing arm pin corrosion

Gidday all. Hope all is good.
I am seeking some advice on the swing arm pin please.

having experienced corrosion and subsequent difficulties in removing the swing arm pin, and reading the same tales here, I am thinking about making a stainless pin.

however, the corrision resistance usually depends on having oxygen circulating around it to form the protective chromium oxide barrier. without this barrier stainless will rust.

in the cradle mounting part, there wont be much air at all, especially if there is a close fit between pin and bore..

So my question is
due to the lack of air in this situation, will there be a tendency for even a stainless pin to corrode in this application.
I really dont know.
or are my concerns baseless.

I dont want to use stainless if the application will still corrode.

the intended grade I would use would be 431 to condition T ( around 50/60 ton tensile roughly).
another option is to use a nitrided 4140 pin. how would that go for corrsion resistance.

Any thoughts greatly appreciated.
best wishes to all bradley

Bradley, I recently assembled mine , fitting a +.005" pin (hardchromed) while I was at it I welded on the cradle 2 x 5/16" nuts tapped thru with grubscrews with
goop (3 Bond) on them and also on the threaded end of the long thin tierod bolt, new O'rings and filled to the brim with oil. I'm confident there will be no corrosion .

At least someone else recognized the main reason for lube here is rust/corrosion not friction of dissimilar metals sintered bronze on very hardened but rust flake prone spindle. Keep in min SS is worse for shear loads though likely beefy enough and the stronger structural fastener types are slightly magnetic so ferric enough to slightly dark stain but not really rusting away flaking even if oxygen exposed. Galling is the issue of SS in rubbing sliding applications so lube for friction may become main reason to keep ahead of it. Hard chrome on good tempered steel would be my first choose but good grade SS should do the trick too. Shoot might work up a batch of Titanium which might work and last as lubed spindle.

Gidday all.
Don, thanks for your comments. my problem was indeed caused by neglect. O rings and cradle faces were worn so no lube. so I have wear issues as well, but I can deal with that.

what I have noticed is bell mouthing of the bore. so i will fix that.

A question please.
when welding the nuts to the tube, was there any distortion to require reaming or did the pin still fit straight in. how parrallel was your bore.
So what I will do is cut the damn tube out and replace with one of decent thickness. that should let me use grub screws as per your suggestion.
I may as well do the best I can and not a half job. I am going to try and make my swing arm idiot proof. Thats why i was enquiring about stainless. Don, as you know I am retired and just like to play a bit now, so thats what prompted the stainless query.

Steve, thanks as always for your comments.

there are 2 problem areas as I see it.corrosion of the pin in the bore, and the wear issue.

Corrosion.
galling is not a issue here mate. galling is more for the softer austenetic grades not capable of heat treatment. 431SS as supplied (condition T) is about 35 Rockwell and about the same tensile as 4340 (over 60 tons) but with appropriate ductility. So no chance of shearing off.

431 has the best corrosion resistance of all the hardenable stainless steels as well as good strength and toughness. it is not brittle but will not bend like chewing gum either.
But I would like to see the surface hardness up to 60 Rockwell at the bearing area.( ball bearing hardness).
I have a idea on how to get this but more research is needed yet.

Regarding titanium, boy that is expensive here in Aussie. A better alternative if going that way would be Monel 400 or Monel K.

But both are overkills. way over engineered.

a hardenable SS is very much appropriate and economical for this application. that is what prompted my query as to the lack of oxygen if used in the swing arm application. but as Don pointed out, keep the seals in good condition and no troubles.
My justification for using stainless was purely corrosion protection.
Thanks again fellas for your comments..

best wishes Bradley

even though the tube is fairly thin wall I didnt have any problems with distortion etc. I guess my tube was worn a fair bit , I didnt have to ream the tube for the +5 thou bigger spindle. it was quite a firm (perfect) fit ,I probably didnt need the 2 grub screws. I bored the old bushings to suit the new spindle.
The amount of miles I'll be doing on this bike I'll be dead and gone before this wears out.

Bradley,

Can't speak for this product but it is stainless.

http://www.eurojamb.com/norton-swingarm ... -2780.html

The stock Norton swingarm pivots are case hardened. Hard to say how anything less would hold up.

George

madass140 said:

Bradley, I recently assembled mine , fitting a +.005" pin (hardchromed) while I was at it I welded on the cradle 2 x 5/16" nuts tapped thru with grubscrews with
goop (3 Bond) on them and also on the threaded end of the long thin tierod bolt, new O'rings and filled to the brim with oil. I'm confident there will be no corrosion .

Click to expand...

I went the sheave clamp route, and couldn't be happier. I also was apprehensive about both the frame's integrity and my ability to perform a proper weld. Add to the fact that the clamp doesn't pull the cradle tube away from the pin as the welded nuts do; rather, it compresses the tube down around the pin, then adds grub screws for positive anchoring in the frame tube. Granted, either way is so much more than what comes stock.

Stainless clamps bought from McMaster-Carr http://www.mcmaster.com/#6436k34/=x50zn4 You'll need to drill and tap one side each for the grub screw. An easy job in a drill press. Now, while you can buy clamps from them that already have the hole threaded in the side, they're over $43 USD each!

Add a couple of these http://www.mcmaster.com/#90669a353/=x511m7 and you're all set.

I don't have any pictures of my installation, but here's a link of the very thing done on Dave's ride from back in '10: not-another-spindle-thread-t5978.html. I deviated in two places from Dave; previously-mentioned brass-tipped grub screws, and no flats on the shaft (allowed by the use of the brass-tipped screws).

(Thanks to Dave for the picture)

Nathan

Gidday All. hope all is good.

George and Nathan
Thank you very much for your comments. it is greatly appreciated. gee, this is a good place, the spirit of co-operation is unbeliveable.

George, I had a look at the link you gave. it does not give what grade is used.

it is my belief, and I may be wrong, that most stainless offerings use a 3xx series stainless. These grades are less costly and also more machinable than the 4xx grades. These are austenetic grades not capable of responding to heat treatment and possess too much ductility therefore lack of hardness for this application. Though they may work harden in use, I dont know to what extent.

I reckon the martensitic grades, ( 4xx type steels and are capable of responding to heat treatment), have higher strength and hardness are more appropriate.

You can get up to 40 Rockwell with some grades. When properly lubricated, this will be enough hardness. also 4xx has higher tensile strength and toughness.

My last pin I made from 4140 nitrided to 60 Rockwell. but not well lubricated and was neglected. When removed, it showed not much wear but evidence of fretting .
I made the bushes from leaded bronze (LB1) and they showed too much wear. I thought they would have performed better, the material recommended for performing better under scanty lubrication conditions.

Nathan, my tube is stuffed mate. worn and bell mouthed. I will cut it out and replace with something more robust

i am retired and have too much time too think about things like this. So I muck around with things. This being for myself only, time is not an issue, it is very easy to over engineer a product. i am trying to idiot proof my swing arm as sometimes things dont get the attention they deserve from me.
Anyway thanks for your comments fellas, it is appreciated. best wishes bradley