FF: Forks Cracked FF3 Lower Link?

[Elanman39]

Hi, I have just been round my recently bought 1950 Comet with a grease gun and have found what seems to be quite a few additional grease nipples above those mentioned in the literature. One is on the underside of the FF3 lower link and is clearly intended to feed the front pivots. When I applied the grease gun however I noticed a thin curtain of grease being ejected from the leading edge of the FF3 link, not from a single point like a drilled hole

but in a line runnning about half the width of the link, located centrally. See the attached pictures, the first of which uses a mirror to try and show the source of the "curtain". I cannot get a direct line of sight to the front of the link, but am worried that I may have a crack there. Is this a known issue, is there a machined slot there, are the front forks about to fall off, any other thoughts?
Many thanks, Nick

 

[timetraveller]

That does not look good Nick. If you are new to Vincents some of what I will write might not make sense but I provide a modified geometry for the front end which improves both the comfort and safety. Part of the modification involves opening the rear eyes of the lower link in order to fit ball race instead of the Oilite bushes. Do over the past few years about fifty of the lower links have passed through my hands and some are in very poor condition. They are bent, twisted or otherwise deformed and have to be straightened before being modified. Several have had cracks where the arms join onto the front part which looks to be split on your bike. I have not seen one like yours and I would urge you not to use the bike until you have a new one. They are about £360 from the Spares Company.. who were out of stock several months ago. At the time I did offer to draw some up on the computer with a view to getting them machined from solid. This was not of interest to the SC at the time but you might be disappointed with the ones they supply as they are as cast and unpainted.

 

[Chris Launders]

I assume they are cast steel not cast iron, if that is the case could it be safely welded ?

 

[bmetcalf]

Good point on welding. A crack like that in a casting is pretty unexpected, at least to this non-expert.

 

[timetraveller]

The story is that they are steel forgings but when one buys new ones they look to be cast. I do not know whether the forging process would remove those marks or not. When one removes all the paint from an original one they are smooth to the point of being polished. Certainly the new ones are supplied with only the necessary surfaces machine and the rest as rough as the proverbial badger's botty.

 

[Chris Launders]

I think at a minimum it needs stripping and all the paint removing just to see what's actually happened, a forging or casting shouldn't crack like that normally, that's not a high stress area of it.

Could it have been cracked by someone using a high pressure grease gun, if the fork blades were tight up against the bushes there would be nowhere for the grease to go.
Someone out there should have a spare if they can be persuaded to part with it.

 

[b'knighted]

Not entirely related to this problem but, if you are going over the bike with your greasegun, do not pump an excessive amount into the nipples on the brake cams. You do not want any coming out of the bush into the drum.

 

[Elanman39]

Thanks for all your thoughts guys, greatly appreciated. As you suggest she's grounded until I know what's going on, hopefully I'll find time to at least have a closer look with the fork bridge removed later on today. As Timetraveller says I've read they are forged steel somewhere, so a weld repair should be feasible and safe if the kink isn't too far gone in the first place. I wondered the same as Chris, whether it was a high pressure grease gun that burst a weak point (maybe a cold shut equivalent) in the forging. I was only using a small handheld gun so hope it wasn't me, but it's hard to see how else a crack could have formed there between the two bearing bosses; normally I would expect the crack to start at one end or the other where the normal use stresses are highest. I'll post pictures as soon as I have some. If anyone out there has an FF3 they would part with please let me know!
Grease nipples on the brake cams? Didn't see those..... Good advice regardless, I'll have a look! Thanks.

 

[Peter Holmes]

I used to work in the printing trade many years ago, left it in 1975, but the German machines I used to operate came with large Tecalemit grease gun that fitted over domed nipples on the machine, and they are great for use on a Vincent using standard Vincent nipples, not the snap on high pressure ones. With regard to greasing the forks, eccentrics etc. the gun will either baulk when the cavity is full of grease, or a small amount of grease will start to show squeezing out of the mating surfaces. I had never before considered the forces involved with a high pressure grease gun, but this sounds like a very good reason not to use one.

 

[chankly bore]

Just a thought from a Colonial ignoramus; I've seen automotive steering components manufactured in two parts with a heavy spline fit. Could the FF3 be more cheaply made in the small batch quantities now required by having a central machined section carrying the blade spindle and damper attachment and the two arms splined? As usual, hoots of derision and ridicule most welcome.