Material choice?

[Cato]

I need to make up two replacement top hats for the swing arm swap, smaller ID and thicker rim. Nothing too challenging, and it's been done many times by others for similar projects. There does seem to be a range of materials used though from "that'll do" to some exotic stuff hewn from a meteorite. The most common at present seems to be stainless, but I don't know (neither do they I suspect) what grade is used.

So I thought I'd ask on here as there are plenty with knowledge of metallurgy and engineering applications. What would the most suitable material be? The top hat rotates through no more than thirty degrees maximum, and at a guess less than fifteen for 75% of the time. It sits inside a greased needle roller bearing.

 

[bricol]

"inside a greased needle roller bearing" ?

The rollers run on your top hat?
Or the top hat sits inside the inner race of the bearing?
Welded to something? Fixed in some other way?

 

[Cato]

"inside a greased needle roller bearing" ?

The rollers run on your top hat?
Or the top hat sits inside the inner race of the bearing?
Welded to something? Fixed in some other way?

Sorry, the picture I meant to post would've helped.

 

[PhillipM]

I'd think anything short of some hardened chrome containing steel is gonna suffer from false brinelling in short order.
That original one looks like it's a turned top hat insert pressed into at 52100 bearing sleeve? 2 separate pieces?

 

[Cato]

I'd think anything short of some hardened chrome containing steel is gonna suffer from false brinelling in short order.
That original one looks like it's a turned top hat insert pressed into at 52100 bearing sleeve? 2 separate pieces?

It's a single turned piece, that one's been in for 26,000 miles.

 

[Kram]

Your pic does look like two peices with eccentric wear on the inner, which implies the bearing was siezed.

Id choose EN19t, EN24T.

 

[Cato]

Your pic does look like two peices with eccentric wear on the inner, which implies the bearing was siezed.

Id choose EN19t, EN24T.

Thanks.

It's a single piece, the line is just a grease mark, the bearing is free and the ID is round without wear.

 

[Cato]

Your pic does look like two peices with eccentric wear on the inner, which implies the bearing was siezed.

Id choose EN19t, EN24T.

I haven't been taking loads of notice, but have steel prices dropped again? EN24t seems widely available (even in small amounts) and for less than I was expecting.

Reading the specs and common uses for it that would seem to be a good choice to have a reasonable amount of in bar form as stock for the bits and bobs I'd be most likely to have to make.

 

[addjunkie]

Id go en16t as thats more than likley what the spindle is made off too. EN8 would probably out last the bike too

 

[Cato]

Id go en16t as thats more than likley what the spindle is made off too. EN8 would probably out last the bike too

You saying that reminds me I'm sure I read somewhere about EN16 being recommended for spindles.

There seems to be a few places that will sell short (300 mm) lengths of various grades and sizes so I will probably pick up a few bits at the same time.

 

[PhillipM]

I haven't been taking loads of notice, but have steel prices dropped again? EN24t seems widely available (even in small amounts) and for less than I was expecting.

Reading the specs and common uses for it that would seem to be a good choice to have a reasonable amount of in bar form as stock for the bits and bobs I'd be most likely to have to make.

It's down about 60% since april/may

 

[Cato]

It's down about 60% since april/may

That's a hell of a drop then.

 

[Kram]

Id go en16t as thats more than likley what the spindle is made off too. EN8 would probably out last the bike too

En8 is questionable, it may or may not be mild steel that is rolled for extra strength, or plain medium carbon steel that is hardenable. Very different materials! Hardened carbon steel should be more than adequate. I avoid mild, can be horrible stuff to turn and I doubt it would last long for this.

Next is plain cabon steel, 40-50% is common and good for most parts. Turns nicely. Common for hardened chinese parts.

en16 is a manganese/moly alloy steel, a step up from plain carbon steels. 605M36 is the current UK name for it.

Another version, en16M/ 606M36 / usacut55 has sulphur to make it excellent for machining, one of the best steels I have tried, without loosing strength. Supplied soft, and after hardening machines similar to normal 605m36. Weldability is questionable, fine for low risk items, I had no problems, but not for anything important or safety critical.

En19 has chrome to make it harder. Requires a decent cut & rigid machine. Exceptional finish.

En24 even more so, but potentially brittle for shock loading.

Note I avoid leaded steel/En1 mild free cutting. I dont see the point in it, as you may aswell use aluminium!

 

[Agroshield]

The material for the needle rollers to run on does not matter so much as its hardness and surface finish.

See:

https://medias-at.schaeffler.com/en/needle-roller-bearings-aligning#20895975435 (Raceway for bearings without an inner ring (direct bearing arrangement))

Run a file over the part you show in the photo, see how hard it is and note how it is ground, not turned.

 

[bricol]

I'm still not fully clear - are you swapping the bearing to one with a smaller ID, or putting a smaller ID shaft through the top hats?

If the latter, I think I'd be sleeving the shaft to suit the top hat, or drilling out the mounts to use a larger shaft through the existing top hats.

As has been mentioned - needs grinding, and hardening, then possibly finish grinding to be sure of diameter to be properly correct.

I can't imagine anyone has got away with stainless with an open needle roller running directly on it for long.

 

[8ob]

You can buy needle roller thin wall inner rings/sleeves, use those and the top hats could be made from anything.

Example https://simplybearings.co.uk/shop/p...MI3ru05uqw-wIVwp7tCh22UAX7EAQYBCABEgLLcPD_BwE

Bob

 

[Kram]

True however a free machining en16m or en19t will tend to give much better finishes than other steels so material is relevant.
Turned slightly oversize and smoothed to size with emery while on the lathe should give an acceptable finish. I cant claim expereince but I wouldnt hesistate to turn up the same part for my cbr600 if it were needed.
( Absolute roundness be damned, lathe turned should be adequate )

Cant really tell in a photo of a grubby part (as noted above!) but I suspect it will have been turned with the OD oversize and only the OD bearing surface ground the finish. Grinding is much slower!

 

[addjunkie]

Id happily machine that part and fit it, its only a swing arm bearing, not like its runing * at 15000rpm.

 

[Cato]

I could turn an inner sleeve for it and leave the existing top hat in contact with the bearing I suppose. I'd need to check, but I believe the Bandit was a 20 mm spindle and the GSX 15 or 16 mm. So a 2 or 2.5 mm sleeve and a pair of 3 mm spacers would cover it.

That's a lot of faff though, especially when you consider what the movement involved actually is. As @addjunkie says, very limited movement and I imagine the only reason it's a bearing and not a bush is because a sealed bearing will go longer without maintenance.

 

[bricol]

Limited movement is harder on the bearing than continuous - the same rollers roller back and forth on the same bit, possibly not even fully rotating themselves, the lube doesn't distributed, the rollers hammer themselves into the shaft (as mentioned up above rather more poshly already - the brinelling), rapid oscillation causes the rollers to "skid", wrong finish and hardness on the new parts sets the rollers up to fail early too.

Been some correct engineering advice on materials, treatment and finish above for long life . . . and other that gets it running and probably okay for an undermined time.

The needle roller sleeve is a good idea - still needs a good fit on the top hat/spindle to not set up early wear though.

If I was making it myself, I'd do the sleeve (either into the existing top hat, or the inner race). If it was a work job - do drawing and issue it, accept finished, checked component from supplier in a month or so.