Re: [CR] Simplex "Plastic" Derailleurs - Questions For Material Scientists


Example: Framebuilders:Norman Taylor

Date: Mon, 31 Jan 2011 06:22:22 -0800 (PST)
From: Scott Gabriel <slipangle2@yahoo.com>
To: Classic Rendezvous <classicrendezvous@bikelist.org>, Hugh Thornton <hughwthornton@yahoo.co.uk>
In-Reply-To: <893607.71051.qm@web25904.mail.ukl.yahoo.com>
Subject: Re: [CR] Simplex "Plastic" Derailleurs - Questions For Material Scientists


Hugh,

I recently posted a similar request for info regarding salvaging and/or restoring Simplex "plastic" derailleurs on another bike forum and received responses ranging from Mother's "Back to Black" to lighter fluid, followed by a match, a hammer, a heavy boot, etc. Clearly a contentious issue. One member suggested the white bloom was caused by off-gassing as the Delrin gives up its volatile ingredients to atmospheric aging, but that's strictly a guess I would think. Vaseline petroleum jelly was suggested too, reputedly an old car detailer's trick. I decided I will try the Mother's product on my Criterium derailleurs though I admit the Jimi Hendrix approach was tempting.

Scott Gabriel
Cape Cod
US


--- On Mon, 1/31/11, Hugh Thornton wrote:


> From: Hugh Thornton <hughwthornton@yahoo.co.uk>

\r?\n> Subject: [CR] Simplex "Plastic" Derailleurs - Questions For Material Scientists

\r?\n> To: "Classic Rendezvous" <classicrendezvous@bikelist.org>

\r?\n> Date: Monday, January 31, 2011, 9:02 AM

\r?\n> The plastic in Simplex derailleurs is

\r?\n> often referred to as Delrin (A Dupont acetal copolymer). 

\r?\n> As far as I can remember back in the early 1960s, when they

\r?\n> first appeared, the publicity material referred to Delrin by

\r?\n> name and the name has been associated ever since.  Does

\r?\n> anybody know whether Simplex continued to use Delrin or

\r?\n> whether they changed to another acetal or something else

\r?\n> altogether?

\r?\n>

\r?\n> Another thing I am interested in is the deterioration of

\r?\n> the finish and whether it is reversible.  Occasionally

\r?\n> early models in white resin come on the market but very

\r?\n> yellowed.  I have wondered whether that is through

\r?\n> absorption of oil. grease and dirt into the material such

\r?\n> that it is effectively permanent discoloration, or whether

\r?\n> it is on the surface and can be

\r?\n> removed.

\r?\n>

\r?\n> The common finish deterioration on the black plastic

\r?\n> moldings of later derailleurs is a blooming or whitening of

\r?\n> the finish.  I assume this is caused by atmospheric

\r?\n> pollution or exposure to light.  This does appear only to

\r?\n> be "skin deep" and it can be removed rather laboriously with

\r?\n> a mildly abrasive liquid such as car paint renovator.  Does

\r?\n> anybody know if there is a better way, such as using some

\r?\n> not too noxious chemicals, that would make it easier to

\r?\n> renovate, especially in the nooks and crannies which are

\r?\n> hard to reach any other way? 

\r?\n>

\r?\n> You might well ask why anybody would want to renovate a

\r?\n> Simplex derailleur when it is so much easier to throw it

\r?\n> away, but the better models such as the LJ 4000, referenced

\r?\n> recently by a listmember, are not so plentiful.  The others

\r?\n> seem to be considered so plentiful and so disposable that a

\r?\n> world shortage of them could develop too.

\r?\n>

\r?\n> Hugh Thornton

\r?\n> Cheshire, England