On Tue, 21 May 2019 10:26:46 -0700, sms
wrote:

On 5/21/2019 10:00 AM, Jeff Liebermann wrote:

snip

$12 for two straps? That seems rather expensive.

It is. But a kluge of cable ties and associated bits and pieces is not
going to work as well and by the time you buy all the parts you'll spend
more time cobbling it together.

There are also the Zefal Gizmo clamps
https://www.amazon.com/dp/B01MSM1O1H and the Topeak Versa Mount
https://www.amazon.com/dp/B077S5G4SL.

Above all, don't use hose clamps! And don't drill holes in the frame for
Rivnuts.

Why ever not? Can you supply us with any evidence that installing a
rivnut, or two, significantly weakens a frame?

But lets figure it out.
Frank tells us that he is a PE which means that he has both the "book
learning" and the hands on experience to be an engineer so I'll leave
the actual calculations up to him.

Material
Columbus double butted Niobium alloy seamless tube (The most famous
Columbus round set)

SL Seat Tube
O.D. 31.7mm
Wall thickness - 0.5mm
Wall thickness at butt - 0.8mm
(Note: Butted end for installation in Bottom Bracket)

Material - Niobium is a special steel with Manganese, Chrome, Nickel,
Molybdenum and Niobium.
Mechanical Properties:
UTS: 1050÷1150 MPa, Ys = 750MPa, Ap5 14%.

Project:
Two holes in tube to support bottle cage
Holes on 7 cm. centers
Fastener:
M4 x 0.70 Rivet Nut, Large Flange, Smooth Body
Recommended hole size - 6mm +0.1 - 0.0

Questions: (a) actual loss in strength in actual PSI/MPa and % of tube
strength lost, and (b) is this considered a significant loss in frame
strength?
--
cheers,

John B.