Re: [CR] Drillium


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From: "paccoastcycles" <paccoastcycles@sbcglobal.net>
To: "Mark Bulgier" <bulgiest@gmail.com>, "Eric Keller" <eekeller@psu.edu>
References: <AANLkTikBXrNy+vL11p1Ua_jY3eANQ1ADE=DZ0iz2i0ze@mail.gmail.com> <1386041.42829.1296509921528.JavaMail.root@sz0151a.westchester.pa.mail.comcast.net> <AANLkTimE5ySb=K7UQ90PH48a1QMyQOX46gPTJKTzdr-W@mail.gmail.com> <AANLkTin5apj9FivbdCHeyuWLM4ikCCGs_q7RXB+EumgT@mail.gmail.com>
Date: Mon, 31 Jan 2011 18:46:52 -0800
Cc: CR <classicrendezvous@bikelist.org>
Subject: Re: [CR] Drillium


Yes, Mark. It takes a lot of holes to make a measurable difference in an aluminum part.

Chuck Hoefer
Pacific Coast Cycles
Oceanside, Ca.


----- Original Message -----
From: "Mark Bulgier"
To: "Eric Keller"
Cc: "CR"
Sent: Monday, January 31, 2011 6:35 PM
Subject: Re: [CR] Drillium



> Eric Keller wrote:
>
>> In retrospect, I'm actually a little surprised that there was no drilling
>> of
>> rims back in the heyday of drillium. Or maybe there was and I just
>> didn't
>> know about it.
>
>
> Yeah there might have been more of that going on than than was visible
> from
> the outside. I doubt I'm the only person who's ever done this:
>
> On the race bike I made for my wife around 1990, light weight was a
> priority
> because she's light. 2.4 lb (1.1 kg) lugged steel frame! I used Saavedra
> clincher rims because she rode clinchers and the Saavedra was the lightest
> I
> had heard of, yes even with the rim "washers". I added three more holes
> in
> the inner wall, where the rim tape goes, between each of the big holes at
> each spoke, maybe 10 or 12 mm each? The new holes were the same size as
> the
> existing holes. Made the rims significantly lighter, though I forget how
> much exactly, I just remember being pleased with the number at the time.
>
> And I don't think I weakened them one bit! Unless I'm not thinking this
> through correctly -- but it seems a chain is as strong as its weakest
> link,
> and adding more weak links equal in strength to the existing weakest link
> doesn't make the chain any weaker -- right? I only added more holes the
> same size as the ones that were already there.
>
> We replaced those rims after a pretty respectable number of miles when the
> rear was starting to get little cracks at each nipple -- but that's in the
> outer wall, nowhere near where I drilled 'em. Such a light rim with only
> 28
> spokes (rear) can be expected to crack at the nipples eventually anyway,
> so
> I don't think my holes in the outer wall caused the cracks she got.
>
> In theory this could be done with tubulars also, but probably not a good
> idea since you'd be reducing the surface area for glue.
>
> Hmm let's see, 28 x 3 = 84 "extra" holes. If we assume 10 mm holes and
> the
> wall thickness = 1.0 mm, then the volume of aluminum drilled away is Pi x
> 25
> x 84 = 6597 mm^3. Given a density of 2800 kg/m^3, that gives us a weight
> for the drilling chips I made of 18.5 g per rim. Hmm, I'd hoped it was a
> bigger number than that, for the amount of time it took! Actually I think
> the holes were probably bigger than 10 mm and the wall was probably over
> 1.0
> mm thick, so maybe I got 25 or 30 grams shavings/savings per rim, big
> whoop.
>
> "Normal", visible drillium isn't about the weight of course, it's about
> style and flash. Super Record perforated brake levers being heavier than
> N.Rec. and all that. But if it's hidden inside to where you have to take
> the tires and rim strips off to see it, it'd better be actually reducing
> the

> weight!

>

> Mark Bulgier

> Seattle, WA

> USA