Homebrew PCBs

----- Original Message ----- 
From: "Stefan Trethan" <stefan_trethan@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, March 12, 2005 3:03 PM
Subject: Re: [Homebrew_PCBs] titanium grades


>
> On Sat, 12 Mar 2005 13:57:27 -0000, Leon Heller
> <leon.heller@...> wrote:
>
>>
>> Titanium is *very* stiff, more like steel than Al. It's difficult to
>> machine. Why not use a plastic shaft, something like Delrin should be OK?
>> Leon
>> --
>> Leon Heller, G1HSM
>> http://www.geocities.com/leon_heller
>
>
> Oh well, that would need a larger diameter.
> I guess it would be ok if i go with the bigger diameter pipe.
>
> But then, i don't need to machine it at all (maybe saw to length and
> polish as well as smooth the bottom end that rides in the bearing, so i
> might as well use titanium if i get it surplus.
>
>
> Which diameter would a delrin shaft need to be if we say the tube is 50mm
> dia and 20cm long? the shaft is supportint the tube via the two endplates.
> How would i make the bearing with a delrin shaft? Does it run well in 
> ptfe?

I just checked Delrin's properties, it's no good in acid or alkaline 
solutions:

http://www.upchurch.com/TechInfo/matDelrin.asp

It's a pity, as it's otherwise a very good material.

>
>
> I also would have a carbon fiber tube from model building with 8mm dia for
> a shaft that could easily take the load, but i don't know how i would make
> the bearing if i use that. It is carbon fiber in some resin, probably
> epoxy, wall thickness is about a mm.

Carbon fibre uses a similar epoxy resin to fibre-glass.

Leon