Lyrebird Cycles

[Mark Kelly]

Unfortunately toxicity and performance seem to go hand in hand with PU.

[Mark Kelly]

I'll take a look at that epoxy you recommend though... We're using some furniture specific stuff, but it's open time is only 30 minutes, and it's also VERY sensitive to temperature (22C +- 3 degrees ambient, or it hazes like crazy).

That sounds like it might be amine blush.

Thinking about it, the one I mentioned is probably not ideal for your process, it's a special purpose low viscosity / high crosslinking laminating resin and it sets really slowly unless you get it to 80 degrees C or so, which promotes crosslinking rather than chain extension. It does retain good clarity and doesn't blush at all but it's also slightly yellow. It's also very expensive.

Have you looked at the specialist epoxies they use for casting museum specimens? They are formulated to prioritise optical clarity so they might work well for you.

[Mark Kelly]

A bit of a forced hiatus while I dealt with a stupid mistake and worked on something I've been wanting to do for a while: moving some of the joint reinforcement to the inside surface of the joint.

The reasons are several and complex but it's largely due to the difficulty of making the wood laminae conform to a compound curve. The solution at which I arrived follows:

3D printed moulds for the extra tabs:


Tabs_mould

Not much use until you fill them with carbon


Tabs_demoulded

The carbon bits need to be dressed back


Tabs_dressed

Then bonded to the inside surface of the tube: note that the tabs are on the part of the tube that would normally be a butt join: adhesives are at their weakest with butt joins.


Tabs_bonded

The reinforced joint is then made:


Tabs_joined

And if you do enough of them you get a frame or at least most of one:


Main Triangle

[Colinmclelland]

I'll be patient and just wait to see how you do it, but i'll be fascinated to see how you deal with the joins, as I know there isn't an inch of exposed carbon in the finished product.

Mind you, the whole thing has been fascinating. Thanks for posting the process.

[RichTheRoadie]

There’s a fair bit of exposed carbon on mine.

[Mark Kelly]

There will be exposed carbon but the arrangement will change.

As I mentioned above there are many reasons for this change. One of them is in response to feedback from Rich about his frames, I realised I was over-building the joints and this contributed to some front end harshness.

[Colinmclelland]

There’s a fair bit of exposed carbon on mine.

A fair bit, but not as much as it looks like there will be at this stage! I'll watch and learn. Well, i'll watch anyway.

[Colinmclelland]

To be clear, i'm just curious....

[Mark Kelly]

By calculation, the exposed carbon will be 3% of the surface area of the main triangle, not counting the carbon bottom bracket "lug". Most of the area you can see exposed will be covered by wood tessellae applied between the areas of carbon.

I finish the head tube after the main joints are bonded and wrapped: I'll add another layer of carbon between the joints to bring the surface back to cylindrical before adding the final layers.

[Colinmclelland]

Wood tessellae. I knew it would be something obvious! Now that I've googled it, i'm not so ignorant...

[Mark Kelly]

There have been many times where I've thought I'd bitten off more than I could chew, but the last week and a bit takes the biscuit.

Carbon dropouts with integrated direct mount brakes and Mavic's "Speed Release" through axle system, formed in 3D printed moulds:


Dropouts_1

I was a bit generous cutting the prepreg for the layup in a couple of places but that will trim off and I didn't want to be short.

The stainless axle wear plates were co-moulded into the dropouts. The hex form visible in the lowest clamshell will hold the threaded boss for the through axle. BTW the thread form is M12 x 1 double lead: try buying a tap for that off the shelf.


The green foam and release fabric provide the pressure for the moulding process and enable release from the moulds.

[Mark Kelly]

Tall Tree_2
Pic courtesy Tall Trees Project.

Now I'm willing to bet that I find trees more interesting than you do, but this is special. The tree in the pic has just been confirmed as the only known hardwood tree over 100 metres tall*.

Here's another pic:


Tall Tree

Why is this of relevance: well I can positively identify three of the hardwoods I use as trees in the pic and I think there's a fourth. The tall tree is E. Regnans (Mountain Ash), couldn't be anything else. The conical tree to the left that looks like a pine, isn't, it's A Melanoxylon (Blackwood, a relative of Koa). There's a feathery looking wattle in the understory which is A mearnsii (Black Wattle). I think the foliage in the foreground of one of the pics is Nothofagus cunninghamii (Myrtle Beech).

* An even taller E Regnans was found near Melbourne in the 19th century but they cut it down to re-measure it. I'm not kidding.

[Andrew R Stewart]

Mountain Ash? We had one in the yard when I was a child. It was a slow grower and scattered little orange pea sized berries about. Not what a child wanted when having to mow the lawn. Andy

[Mark Kelly]

Different tree, you are the other side of the Wallace Line, so you will be referring to Sorbus americana.

Many Australian trees were named by Poms who knew nothing about them, so our mountain ash (Eucalytpus regnans) is so called because it has a pale straight grained wood like English ash (Fraxinius spp) and grows in the mountains near Melbourne.

[RichTheRoadie]

Poms

Originally 'PoHM' - or Prison of his Majesty - which got shortened to POM by said convicts who eventually (mostly) became the lazy Aussies who populated this massive country...

Home from home, if you will. Although I personally have no criminal record; and I haven't traced my bloodline to know if any of my relatives (or "relos" in Aussie slang) were on those first fleets.

I jest (aside from the origin of the 'POM' thing; ad my own criminal record) - I bloody love the place.

[Mark Kelly]

Common furphy but not supported by the evidence. According to Chalmer's "Dictionary of Australian Slang", the most likely derivation is rhyming slang: "pomegranate" for immigrant, shortened to "Pom"

[RichTheRoadie]

the most likely derivation is rhyming slang: "pomegranate" for immigrant

No East Londoners can have made the first fleets, based on the quality of that rhyming slang!

[Mark Kelly]

Australian rhyming slang was its own thing. Some of them, as you say, lack a certain poetic quality. Some, however, are pearlers: "septic" for yank, the official explanation is it is from "septic tank" because they're big and full of shit.

[RichTheRoadie]

My favourite Aussie slang vid:

It’s all in good jest, Mark - I love ‘youse’ Aussies! Especially when you build bikes like yours.

...aaaand we’re back on topic...!

[Rich Beaudoin]

I thought I’d heard that the origin of ‘pom’ derived from French word ‘pomme’ (apple) because English red complexion.
But what do I know - I’m just a ‘sepo’