Damage to fork crown - replace? With what?

[slowster]

I have replaced the bung sooner or later with a star fangled nut, because of the two options in my opinion the nut is the better permanent solution in a steel steerer. The bungs are not an optimal fit in steel steerers, so may need to be tightened more to prevent slipping, and I think some designs of bung might not suit being left for years like that in the steerer. Also, the bung consists of several separate parts, and in the long term I think it is much more likely to be affected by water ingress than a star fangled nut.

[Brucey]

......You really are inventing problems that don't exist aren't you?!
1) SFNs are about £2-3 if you buy them individually.
2) most people will never have reason to buy one, it's only necessary if you're fitting brand new fork....

largely because of the fitting method, SFNs are not 100% reliable. they can be fitted with/in some systems , but not other systems

[GideonReade]

I know where I've seen bungs, of a kind, before - bar end shifters. TBH those (all Shimano 8 or 9 speed) looked a bit excessive to me, as in, very strong, or perhaps some parts overstrong for their role. I think they were Ultegra spec, too, so lightness would be expected.

Those go inside the end of a drop bar, by default alloy, but at the end presumably minimum wall thickness. Perhaps circumfrential stresses (ie bursting) force the expander to extend over a longer length.

[Plus the rubber lever covers last about 2 months before sliding off.]

I guess bar end brake levers must be similar, and might reasonably be under more stress than gear shifts.

[Brucey]

I know where I've seen bungs, of a kind, before - bar end shifters......

FWIW these can, without undue difficulty, be repurposed as 'bungs for other things', including a-headsets. The pricey gold finish on many of these parts is very often a mere cosmetic embellishment, serving no useful function. There is a fairly obvious problem in that they have just allowed for fairly small diameters and diameter variations. However, this is fairly easily overcome by use of a tubular bush, slotted so that it might expand more easily. Such a bush can be made from metal, plastic, or better yet, wood. In the latter instance it is much the best thing if the finished bush is given a couple of coats of epoxy resin. To those who'd say 'surely epoxy resin is an adhesive, why not use it as such'? I'd say ''ah yes, whilst you can make lighter headset preload adjusters this way, they are unlikely to be removable'.

On the inside, commonly/conveniently they often use a M10x1 thread which means you can make an 'expander bolt' using an old rear axle and a few 'odds and ends'. If this bolt is slotted at the pointy end, it can be retightened even when only this part is accessible via the M10x1 threaded hole, using a flat blade screwdriver. Very conveniently the axle is exactly the right size for an M6x1 tap, allowing the bung to be virtually failsafe in use.

[GideonReade]

Sounds quite sensible. I think you're saying the inside of a standard QR axle is the right size to tap to M6? I didn't know that. Part of me suspects it's a fairly hard steel, but on reflection it doesn't need to be.

I'm a bit doubtful about using wood as a spacer, even epoxied. Keeping it really waterproof is going to be nigh on impossible, so it isn't going to be dimensionally stable. Alright in Burnhamshire perhaps, but if you then rode the bike to say the Thar, it'd dry out and you'd probably lose your top cap and spare spacers under a tuktuk.

Am I the only person here with a box of "useful" discarded old tubes, plastic, etc? One advantage of keeping such junk for decades is that one is sure it's chemically stable. Unlike Abus's "soft touch" D-lock casing I just scraped off cos it'd gone sticky. Anyway, some diameter of old pipe, split, as you say, will do.

Entertaining thread drift, this, while I wait for everything to arrive. The star nut tool came with a star nut, now I have three.

BTW, I possess, but don't use, an interesting lamp bracket that expects one to insert an SFN upwards, into the bottom of the steerer tube. Can't have too much of a good thing, eh?

[rjb]

Shimano axles are very hard. I gave up trying to tap an M6 thread in mine using carbon steel taps and plenty of cutting paste. The tap clearly wasn't up to it and I didn't want to end up with a broken tap stuck inside the axle.

[Brucey]

......I'm a bit doubtful about using wood as a spacer, even epoxied. Keeping it really waterproof is going to be nigh on impossible, so it isn't going to be dimensionally stable.....

I suspect you would get very short shrift on that one from boat builders.

FWIW I would describe tapping an M6 thread into a shimano axle as 'very easy indeed' providing you have a half- decent (ie. not carbon steel) tap.

[Mike Sales]

Carvel built boats have planks butted edge to edge, with a crevice between stuffed with caulking, and are commonly put into the water for the swelling of the wood to "take up" and staunch the leaks. I remember Dad sinking our dinghy in the shallows to become tight. Even clinker built, which have, like the Viking boats, overlapping planks, often need a soaking to become watertight.
Boar builders know and use the properties of wood.

[GideonReade]

Yes, it's combining materials with different expansion properties that tends to be an issue (some earlier input was about carbon forks with bonded in aluminium and bonded steel steerers). Wood swells when wet. The other generally with temperature, all at different rates.

My elderly neighbour has asked me if I can fix her gatepost, whose timber post, in summer, is loose in its concrete base. Builders endlessly use this system, I think I once did myself. And what I don't understand is why the concrete doesn't split open in winter when the wood soaks. As an undergraduate engineer I'm sure I was told concrete is rated as zero tensile strength, so it'd burst. But rarely does it.

I could fend her off by sneakily pouring water on it, I suppose.

If Brucey suggests spin grinding the post I think I'll eat it

[Brucey]

in case you hadn't noticed, many modern boats are built using wood and epoxy resin. A few coats of epoxy resin is all that is required to do two things;

1) turn the surface of the wood into a composite material.

2) create an impervious (ie. waterproof) layer.

Thus even wooden items can have a constant moisture content internally and are more dimensionally stable as a consequence .

[GideonReade]

Hi Brucey,

Yes, I understand that. But I don't trust that system to remain impervious long term. Jointed wood systems typically flex, typically more at joints. Even strong coatings like epoxy usually end up cracking along joint lines. In a boat application it is/should be subject to regular inspection and repainting as required.

Laying a thin layer of reinforcement (glass/nylon/aramid/carbon) can prevent such cracking, but the resulting strong oversheet then frequently delaminates from the wood in much the same place.

But a spacer might never flex, perhaps?

More practically, speaking personally, I've never been able to either paint thick glop, nor lay up sheet/tissue, with anything like the dimensional consistency required to make a circumference-adjusting spacer.

Wait! Get a dowel a bit smaller than desired inner. Then, long soak in water so it's oversize. Then, SG, wet, to exact size. While wet, wrap with one layer clingfilm then wind epoxy impregnated tape* around until above outer diameter. Keep damp during curing. Then, SG the epoxy outer to size. Finally dry out and withdraw the now shrunken dowel. SG both ends flat.

Bingo - a composite spacer! Quite a lot of effort though.

*Glass or carbon for stiffness, nylon or aramid for flexible hanging togetherness.

[Brucey]

small items such as spacers are readily sealed, and don't suffer from flexing in the same way.

[GideonReade]

Well, thank you folks. Rebuild completed, short test today feels very nice. Especially grateful for the replacement donated fork.

2000 Pinnarelo Angliru rebuild with Chorus 12, Alpina fork.

That's M's donated Alpina fork - left a bit long as I'm aging.

Campagnolo Chorus 12 Mechanical (TotalCycling in NI, thanks for helpful advice). 48-32 and 11-29. Would prefer 12-29 ( and 50-34) but no longer available. Obviously it's a very pricey upgrade to a fairly basic, and obsolete, frame.

I had to buy basic training tyres to get pretty coloured ones, they've gone right out of fashion. Aerothan tubes haul back the weight. Original wheels.

Spa supplied some incidental parts, along with repair parts and advice for two unrelated bikes.

The objective was to get lower hill climbjng gears, and 32-29 is a bunch lower than 39-23. To my surprise, it all weighs almost exactly a kilo less (With the 9sp Mirage/Veloce it was 10.4Kg, now 9.4Kg).

Brakes were not a problem, but are greatly nicer to use. That's probably replacing the 7 year old blocks and 26 year old cables, rather than "progress".

[Brucey]

.....Brucey, that's very kind! But I fear optimistic, especially as I don't have a lathe... about 40, no 45 years ago, no less than Rolls Royce tried to teach me how to use on, not altogether unsuccessfully... My town could really do with a "men's shed"...

you don't really need a lathe; a drill and an angle grinder will suffice, if not be a useful improvement in some cases.

[GideonReade]

Yes, but if Rolls-Royce* couldn't teach me to use a lathe nicely, what hope would I have with cruder tools? Skilled craftsman, alas, I'm not.

*Culturally, it was probably more still Bristol Aeroplane Company back then. Technically, those lathes had probably turned bits of Beaufighters, they were pretty shagged.