David,
I sent an off-list reply directly to John with respect to his earlier post regarding my "editorial" on Scott / Mathauser curved and finned brake shoes having "permanently" bonded pads. The basic gist of that communication was that I have never personally experienced any delamination problems where the pads somehow broke loose from their holders (...and I abused the living daylights out of a set of these for a good number of years). Whereas I may have seen pictorial evidence of such delamination as well as read the accounts of others who have supposedly encountered it personally, I have still to this day never yet heard nor read a detailed explanation as to how and/or why this may have occurred (...age related fatigue of the bonding agent ... brittlization of same due to durable exposure to temperatures of extreme? ... exposure to significant contrasts in actual temperature whether it be ambient or friction based usage induced? ... a manufacturing "flaw" resulting from improper use or application of the bonding agent? ... the unfortunate result of someone actively trying to pry loose the pad from its holder thinking that it was of the "replaceable" type? ... a combination of any one or more of these factors? ... something else altogether? ... if anyone out can knowledgably speak to this question, please do chime in here as inquiring minds want to know).
Moreover, I do not know for a fact what was used as the original bonding agent although I have read what I believe to be only the conjecture of others that it was some form of "Permabond", "Crazy Glue", or other cyanoacrylate adhesive. If, indeed, that is true, it would be well worth noting that there are several variations of this type of glue (...and I am not referring to brand names here) which are intended for use on very specific substrates. That is why I made the particular recommendation in my original "For Sale" posting with regard to the use of Loctite Prism 406 - because it is specifically engineered to adhere the materials involved. To quote from Loctite's own sales literature, this agent "...is a low viscosity adhesive ideal for difficult-to-bond rubber components and pre-assembled parts. Designed to penetrate by capillary action between components." Should you wish to review the technical data sheet on this particular product, you may do so using the following link:
http://tds.loctite.com/
Robert "occasionally accused of being stuck in the '70's" Broderick ...the "Frozen Flatlands" of South Dakota
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>From: "dddd" <dddd@pacbell.net>
>To: "Classic Rendezvous" <classicrendezvous@bikelist.org>
>Subject: Re: [CR]A Few More Vintage Parts For Sale
>Date: Sat, 2 Sep 2006 18:14:12 -0700
>
>What was the original adhesive used to bond the pink urethane pads to the
>aluminum "holders"? Urethane adhesive? Crazy glue?
>I've got one here that's starting to peel, I was hoping to sand the
>surfaces and re-bond it, using appropriate care of course.
>
>David Snyder
>
>
>----- Original Message ----- From: "John Thompson"
><JohnThompson@new.rr.com>
>Subject: Re: [CR]A Few More Vintage Parts For Sale
>
>
>>R.S. Broderick wrote:
>>
>>>CAUTION: as with all original Scott / Mathauser finned and
>>>curved brake shoes and pads of this vintage, the brake pads themselves
>>>have been permanently bonded to the aluminum shoes - how "permanent"
>>>this bond may be after thirty years is a matter for speculation
>>
>>FWIW, I've had several sets of these in regular use for ~25 years with
>>no signs of delamination, and very little thinning of the pad material
>>either for that matter.
>>
>>--
>>John (john@os2.dhs.org)
>>Appleton WI USA