Carbon fibre pendulum rod

[duncan webster 1Participant @duncanwebster1]

Posted by SillyOldDuffer on 25/08/2020 18:22:05:

Posted by John Haine on 25/08/2020 17:23:04:

Hmmm…

…

As long as you know about the shift you can allow for it in the timetables. …

Ah, but how many timetables are needed? Passengers departing Paddington need one in London time while anyone meeting the train at Temple Meads either needs another timetable in Bristol time or does maths on the London one. Same problem in reverse, does the Temple Meads timetable show departures in Bristol time, or in London time? Most mid-Victorians weren't well educated and would have found the maths difficult. Even today many struggle to understand timetables.

Worse for anyone carrying on to Fishguard which is nearly 5 degrees West of Greenwich. Much easier to put everyone in the British Isles into the same time zone, and ignore noon being slightly off clock time.

I think pairs of timetables would be needed for all journeys with a significant east-west component, like London to Birmingham or Liverpool to York. Think of the work and the mistakes!

Dave

You only need one set of timetables, you depart London (good idea) on London time and arrive in Bristol in Bristol time. It might mean that the timetable time for going one way is 20 minutes longer than the other way, but it works. The chap doing the timetable needs to concentrate, but the guard is very likely to get confused as his watch will only be 'correct' at one end or the other. What speed you are doing is an interesting philosophical debate. Altogether a better idea to have standard time. However, to make things equitable the UK meridian should have been postioned so that the furthest east point of the UK (Ness point Lowestoft 1.75 E) was the same amount early as the most westerly was late. I'm in danger of getting political here, as Eire was part of the UK in the early 1800s, but if we stick to mainland Britain, the most westerly point is Corrachach Mor 6.13 W . On this basis the meridian should pass along what is now 3.94 W, but the arrogant Londoners used Greenwich (so that they didn't need to change their clocks?). Anyway, Swansea Standard Time doesn't have the same ring does it. Perhaps rolls off the tongue better than Blaenau Ffestiniog. A Scottish version could be Wishaw or Nairn

This really is getting off topic!

[Alan CrawleyParticipant @alancrawley27839]

All of the above explains how my friend who completed a trip back home from Oz on Concorde from Bahrain arrived here before he left there.

Someone mentioned Fisshguard and I frequently stay with friends there and the shift in daylight is very noticeable.

A further aside-I think the carbon fibre rod looks nice with the brass bob and weights etc.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Alan Crawley on 25/08/2020 20:19:27:

[…]

A further aside-I think the carbon fibre rod looks nice with the brass bob and weights etc.

.

In reality … that might be the best bit of the whole adventure

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 25/08/2020 19:49:26:

I have finally found out how a Caesium clock works (hint: you won't find out from Wikipedia).

Neil

.

To be honest, Neil … I don’t much care how it works

The magic of Time, and Timekeeping, disappeared when they adopted it.

MichaelG.

[Mason GreenParticipant @masongreen60104]

I found this 1 meter length, threaded carbon fiber rod:

McMaster Carr

A bit expensive, but might make it easier to attached a weight at the bottom and fixtures at the top.

No adhesive required? I read somewhere that adhesive is the weak link in regard to stability.

–MG

[John HaineParticipant @johnhaine32865]

Interesting! I think that is actually solid carbon? Max temperature is 3630*F which implies there isn't any resin in the mix – also it says "chopped" which if it's referring to fibres would not be very good for a pendulum where you really want full-length longitudinally laid fibres.

[Alan CrawleyParticipant @alancrawley27839]

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Haine on 07/03/2023 22:48:14:

Interesting! I think that is actually solid carbon? Max temperature is 3630*F which implies there isn't any resin in the mix – also it says "chopped" which if it's referring to fibres would not be very good for a pendulum where you really want full-length longitudinally laid fibres.

Chopped AND no resin … hardly credible

Is there a proper description of the product anywhere ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Alan Crawley on 08/03/2023 09:20:01:

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.

.

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

MichaelG.

[John HaineParticipant @johnhaine32865]

Posted by Michael Gilligan on 08/03/2023 09:47:09:

Posted by John Haine on 07/03/2023 22:48:14:

Interesting! I think that is actually solid carbon? Max temperature is 3630*F which implies there isn't any resin in the mix – also it says "chopped" which if it's referring to fibres would not be very good for a pendulum where you really want full-length longitudinally laid fibres.

Chopped AND no resin … hardly credible

Is there a proper description of the product anywhere ?

MichaelG.

CFC Threaded Rods

**LINK**

[SillyOldDufferModerator @sillyoldduffer]

Posted by John Haine on 08/03/2023 09:51:31:

Posted by Michael Gilligan on 08/03/2023 09:47:09:

Posted by John Haine on 07/03/2023 22:48:14:

Interesting! I think that is actually solid carbon? Max temperature is 3630*F which implies there isn't any resin in the mix – also it says "chopped" which if it's referring to fibres would not be very good for a pendulum where you really want full-length longitudinally laid fibres.

Chopped AND no resin … hardly credible

Is there a proper description of the product anywhere ?

MichaelG.

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

[David JuppParticipant @davidjupp51506]

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

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

[Michael GilliganParticipant @michaelgilligan61133]

The day is not wasted … I have learned something new

MichaelG.

[Alan CrawleyParticipant @alancrawley27839]

Posted by Michael Gilligan on 08/03/2023 09:49:36:

Posted by Alan Crawley on 08/03/2023 09:20:01:

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.

I would add that the pendulum is about 4.5 Kilos.

X-ray shows dark area in cat intestine.

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

MichaelG.

[gerry maddenParticipant @gerrymadden53711]

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!

[Michael GilliganParticipant @michaelgilligan61133]

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.

[Alan CrawleyParticipant @alancrawley27839]

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

[duncan webster 1Participant @duncanwebster1]

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

[Michael GilliganParticipant @michaelgilligan61133]

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.

[gerry maddenParticipant @gerrymadden53711]

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

[Michael GilliganParticipant @michaelgilligan61133]

Many thanks, Gerry

MichaelG.

.

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

[duncan webster 1Participant @duncanwebster1]

Posted by duncan webster on 08/03/2023 13:13:22:

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

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by duncan webster on 08/03/2023 13:57:26:

[…]

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

.

I will second that

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

MichaelG.

[John HaineParticipant @johnhaine32865]

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).

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