re: [CR]Re Lugless frames/ bilam/performance

(Example: Framebuilders:Jack Taylor)

Date: Fri, 21 May 2004 20:45:29 -0400
From: "HM & SS Sachs" <sachs@erols.com>
To: classicrendezvous@bikelist.org, mountgerald@btopenworld.com
Subject: re: [CR]Re Lugless frames/ bilam/performance


Let us praise Mark Stevens, who brought us an actual frame joint rest report (below). I only wonder if the test done, an effort to cause failure by bending with slow application of increasing force, is the best way to guage suitability for bicycle use. It certainly does not yield a stress-strain (force v. deformation) curve, which I would think would approximate joint "stiffness." It certainly doesn't do megacycles of small bending action, which might test the brass-steel joint itself. But, maybe the National Physical Laboratory was in the Department of Commerce (as is our National INstitute of Standards and Technology, which sometimes does superb work, and I've also seen them overcomplicate what seem to be simple issues).

harvey sachs mcLean VA ++++++++++++++++

Richie, there was a study carried out by National Physical Laboratory, Teddington England on behalf of Gillotts. They were marketing their " L"Atlantique" at the time and reproduced these results in their circa 1950 catalogue. Quote; About the Famous "L'Atlantique" For too long welded frames have had a bad reputation _ and in truth many of those produced deserved the stigma. Too often they were badly made without thought of the particular requirements a lug-less frame needed and frequently the skill of the maker left much to be desired. We knew that this state of affairs was unnecessary and that properly made a welded frame was the equal of the more orthodox lugged frame. In introducing the famous "L'Atlantique" three years ago we demonstrated our faith, which has been amply justified. Today it is firmly established as the finest welded frame made, worthy to stand on its merits equally with its stable companion, the famous connoisseur lugged frame. Not only does the National Physical Laboratory support our opinion, but riders have also proved it in the only practical way they can- by hard riding over along period. All our welders hold A.I.D Certificates and they are specialists in cycle frame construction. This fact, combined with the special 531 tubing we use, is the reason why the "L'Atlantique" is so popular today. Here is the reproduction of the report from the National Physical Laboratory. ________________________________________________________________________ Engineering Division report. On a bend test on a cycle frame joint supplied by Messrs Gillott for |Good Cycles Ltd. 179-181 Southampton Way. London SE5 for whom the test was made. Authority for test; Application form dated 22nd September 1948 N.P.L. eng,. test mark SJA The material submitted for test consisted of a brazed cycle frame joint, made from 2 steel tubes, set at an angle of about 100 degrees to each other. One of the tubes was about 20 inches long by 1 1/8th inch outside diameter by 0.025 " in thickness, while the other was about 5 1/2" long by 15/16ths inch outside diameter by 0.072 inch in thickness. The object of the test was to determine the strength of the joint under a bending load.

Method of Test.

After ends of the short tube had been plugged with steel bar for a length of 1 1/2 ", it was clamped to a sloping member of a testing machine, so that the longer tube was horizontal. A vertical pull was applied to the end of the latter tube , by means of a 1 ton hoist, loading through a calibrated spring balance, in such a manner that the brazed joint was subjected to a gradually applied bending moment.

Result of Test.

At a load of 160lb ., applied at a radius of 21" , the thinner tube buckled at a point 3 inches outwards from the joint. With the object of producing failure in the joint itself a length of the tube containing the buckled area was cut and replaced by a solid steel rod fitting tightly adjacent to the joint terminated about 1/2" from the edge of the joint. On reloading this composite structure a pull of 220lbs applied at a radius of 20" caused fracture of the same tube on the tension side at a point 1/4" from the edge of the joint.

Date: 23rd October 1948 C.G.Darwin. Director Reference: Eng.Div./SJA/PLT/T.33 D.G. Sopwith. Superintendent

_________________________________________________________________________

I dont know of any comparison tests for Bi lam frames but imagine it would yield similar results.
    Mark Stevens Dingwall.