Swing arm bearings

[bbelk]

A short mechanical surgery procedure and both outer races are 'outa there'
Welding them out really is a quick job. That would otherwise be another special tool requirement because the steering head bearing puller probably wouldn't fit.
Interestingly the outer race has a different number 539816 to the inner race 540619.

The swing arm bearing outer race width is 13mm compared to a 30203 dimension of 10.5 ~ 11mm so that is where a spacer will be needed to make up the difference.
I don't want to wait for the bearings to come from the UK, and I don't want to pay $100 a piece in Aus.

Time to put the thinking cap on.

Nice pictures, but how does one weld out a baring and how does the prosess work?

[ME 109]

Nice pictures, but how does one weld out a baring and how does the prosess work?

Rule no1. Be careful, as one could create a shitload of trouble by welding the race to the bike.

The swing arm was easy because it was removed from the bike and able to be placed in an ideal position.
Head stem bearings are a different story and more care and preparation is needed. For head stem bearings I drape wet towels as close as possible to the weld site. This reduces the chance of damage from welding sparks.
The fuel tank comes off as well!
The bottom head stem race almost falls out after welding.

The principle behind welding the races is that the races shrink as the intense heat from the weld cools. The races don't need to shrink very much at all, and mostly can be pulled out with fingers after a few minutes.

I usually weld two runs about an inch or so long, one opposite the other.
I prefer an electrode of 2mm diameter, larger @ 2.5mm is ok as well, but 3.25mm is starting to get a bit fat for this op.
If 3.25 mm was all I had, I would use them, but things become more difficult to control. Also more heat than necessary is needed to run a larger electrode.
I also like to use a short electrode, perhaps 1/2 full length. This allows me to be more precise with where I place the run.
I set the welder amps to run at near the lower end required for a particular size electrode. This also allows for more control, and keeps the weld run narrower.

I need to do my head stem bearings again in the not too distant future so maybe a series of photos would help explain the process.

[bbelk]

Thanks for the great answer. It makes sense to me now. I can also see you are a much better welder than me.
Brad

[Major Softie]

Actually, you don't have to be a great welder at all to do this, but you definitely have to have a precise and steady hand.

Great welders are great at joining pieces of metal, building perfect beads in all sorts of different positions, and understanding the different heating and cooling needs of all sorts of different metals. All that matters here is getting something hot, not penetrating too deep, and not wandering over onto the frame. True, any great welder would be good at this, but you could be good at this and still be a fairly crappy welder.

Trust me. I know that of which I speak.

Signed,
One Crappy Welder

[ME 109]

Well yes and no, Major.

The results of a poorly placed weld or stray arc are not to be underestimated. If either of these occur, we move from general surgery, to brain surgery.
Firstly, the outer race will be impossible to remove without using a dremel to remove the weld/stray arc that is on the frame.
If there is weld metal right next to the outer race, good luck removing it without making a mess of the frame.

What makes a crappy welder needs to be understood.
A welder (person who welds) as opposed to a welder (electronic machine used for welding) needs to possess some basic things that are often overlooked.
Firstly, a person wishing to weld really must have a welding shield that they can see with. Perfectly clear vision is a necessity. If a person wears corrective glasses, they need to wear them while welding. Or have a corrective lens fitted in the helmet.
If yer cant see, yer can't weld.
Secondly, throw away those old electrodes that dad's mate bought back from WW2.
Dry, quality electrodes are also a necessity.
Thirdly, one must be able to confidently strike an arc without the tip of the electrode repeatedly sticking to the job.
If one can see the metal rod of the electrode protruding past the flux, the electrode will stick just about every time.
Striking the arc on a piece of scrap immediately before attempting to weld will have the electrode ideally prepared to weld with.
If the arc length (distance from electrode tip to job) becomes too great, molten metal can be sprayed (spatter) to places where it is not wanted.
These are precise welds.

And it goes on.

[ME 109]

Use the 30203 with a heavy spacer/washer between
the trunnion pin and the bearing. Leaves a very small
amount of space around it to let any water and excess
grease out.
The FAG 32203 is difficult to obtain ( only made by FAG for BMW)
and about four times the price.

Thanks Kutter,
Am I correct in assuming that the washer is to make up for the difference in width between the two bearings?
And I assume the washer's i.d. would need to be very close to that of the pin so as to be able to support the pin and not damage the pin?

[kutter]

That is correct Jeff.
I just went to my local bolt shop and got two
washers that was 3-4mm thick and that the shoulder
of the trunnion pin would push on and that pushes on the inner
race.
How does the pre 1981 trunnion pins differ ?.
You also may be able to reuse the seal if you need
to ?. Just some thoughts I had at the time.

[ME 109]

.
How does the pre 1981 trunnion pins differ ?.
You also may be able to reuse the seal if you need

Interesting question re the earlier pins. Perhaps they were just longer??

I noticed today that there is very little shoulder on my bike's trunnion pin where it contacts the bearing. I 'spose it doesn't need much considering the bearing id is 17mm and the pin perhaps 16.99

A washer/spacer with an id of say 17.5mm would be a poor fit. I'll need to be fussy.

Not fussy enough tho' to buy the proper thing mind you.

[Roy Gavin]

The pins are not a particularly tight fit in the bearings, and on monos and paralevers the bearing can turn on the pin, which quickly wears it, and you cant adjust that wear out.

Moteren Israel make pins which are a tighter fit in the bearing, which they claim improve handling too, and they are also cheaper than OEM too.

[Major Softie]

ME109, continuing on my defense of a crappy welder being able to do this weld.

I certainly couldn't agree more about the vision issue, but a quality hood does not prevent one from being a crappy welder. It definitely allows even a crappy welder to see what the hell he's doing - which is a good thing.

I'm not sure that you, being a good welder, understand the crappy welder. I am not talking about someone who knows nothing or can't control where he welds, but someone who has welded enough to know he can weld, and to really understand the difference between himself and someone who is a really good welder.

A wire feed welder is the tool of choice for the crappy welder, and this solves the arc striking issue. Since the owner of a wire feed welder has anti-spatter goop for his nozzle, he can mask the locations he intends to weld, spray on the anti-spatter, pull the masking, and then merely have to keep his bead on the race.

I am not arguing that it is not easier for the great, or even good, welder to do this well, only that it is definitely within the skill set of the crappy welder.


One Crappy Welder