Carbon fibre pendulum rod

My clock has been running for close to three years with a glued and pinned CF rod now in an area where the temperature changes a lot throughout the year. I never adjust it between the necessary change for daylight saving(!) and it is always within 30 seconds of correct time at that point

How can you save daylight? We tried capturing some in a lightproof box.

Chopped AND no resin … hardly credible

Is there a proper description of the product anywhere ?

MichaelG.

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1. well done, Andy
2. the Cat probably ate it

MichaelG.

https://www.graphiteinsulation.com/product/carbon-carbon-composites/cfc-threaded-rods/

**LINK**

Fascinating, though a bit pricey for me. Must have a matrix, I wonder what it is? Obviously not the usual plastic resin because the rods are OK up to 3000°C!

Dave

Dave, the matrix is amorphous carbon - hence the term 'carbon-carbon composite'.

Edited By David Jupp on 08/03/2023 10:09:13

The day is not wasted … I have learned something new

MichaelG.

I'm surprised (unless I've missed it !) that no one has suggested the use of elliptical CF pultrusions. Much more aerodynamic and stiffer in the more important plane

I bought a couple about 4 years ago for a project that is taking a little while to get going.

Yes they were expensive too!

Funnily enough, Gerry … I haven’t seen that profile on sale for a few years now

Otherwise I would probably have bought some !!

… Do you know of a current source ?

MichaelG.

I bought my round stuff from Macs Models, they have it for £13.46 a metre length.

I used 6mm OD tube with steel end bits glued in with araldite. Look up the shear strength of araldite, you'll be surprised. I ran a tap up the inside of the tube just to scratch the surface, and turned some shallow grooves in the steel bits, just to give a key

No offence intended, Alan & Duncan …

and it may be that you were not responding to my post anyway

… I was specifically interested in availability of the oval material.

MichaelG.

Hi Michael,

Mine came from this place...

**LINK**

...and a cursory glance suggests they might be significantly cheaper now !

Gerry

..sorry the link isnt right. The company was Rock West Composites in the USA.

Edited By gerry madden on 08/03/2023 13:27:27

Many thanks, Gerry

MichaelG.

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Edit: __ but unfortunately, your link appears to be to this thread 

[ you beat me to it … Thanks again ]

https://www.rockwestcomposites.com/shop/rods-shapes/carbon-fiber-elliptical-pultruded-solid-rod

although I suspect the cost of shipping might be prohibitive 

Edited By Michael Gilligan on 08/03/2023 13:28:45

Edited By Michael Gilligan on 08/03/2023 13:29:35

Edited By Michael Gilligan on 08/03/2023 13:36:50

If the spike up the tube is 4mm diameter, and 20mm long, the joint area is 251 mm^2. The lowest figure I can fine for joint strength is 2N/mm^2, and that is for PVC, I reckon that sticking to the resin in CF tube will be a lot better, but even with this very low figure that's 500N, or 50 kg.

I'm not sure cross pin is a good idea, it will put a stress raiser in both tube and spike, and it' not clear that the pin would share the load with the glue

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I will second that

… they don’t use any nails when they put Carbon Fibre repair patches on aircraft wings.

MichaelG.

Well I've put pins in all mine, mainly to share the load with the slug which is glued to the tube. The oldest one has run for 3 years now without failing. That's an 8mm ali slug in a 10mm tube. More recently I have 3.4mm slugs in 6mm tube with more weight on them again without failure (but early days).