Cycling UK Forum

531colin wrote: ↑17 Aug 2024, 8:33am

Carlton green wrote: ↑17 Aug 2024, 7:54am ………I found some images of the Jackson frame on-line and note that the laterals are held well away from the seat tube by suitable stays, that’s not the case in some other manufacturers’ builds, and no doubt those stays are made of high strength material. To my mind those details would helpfully make the frame a bit stiffer in the appropriate directions. …..

The main determinant of the stiffness of a tube is THE DIAMETER. The twin laterals are about 10 or 12mm diameter? About as stiff as a fishing rod.
Gas pipe steel and fancy steel are not significantly different in density or stiffness .
The “stays” which space the laterals from the seat tube are about 8mm diameter.
They do look pretty, though.

The twin laterals on my Raleigh frame measure roughly 1/2” O/D, I’ve no idea of their thickness but that would matter too to their (individual and absolute) rigidity; the (between laterals) stays are also 1/2” and I believe that they are there to stop the (under compression) laterals from buckling - those stays will likely see very little load. The twin laterals triangulate the frame between the steering tube and seat post and then onwards to between the rear wheel too. The wider the base of that triangle the stiffer it is (in the plane of the tubes). Those are just my observations; you’re the expert on frames and very pleased I am to hear what you have to say too - every day’s a school day .

A recent acquisition showing a different approach, a sort of part twin lateral. Perhaps this was done to be able to use a more conventional head lug.

I would expect that design to be problematic in that there is a step change in stiffness where the tubes meet. I'd expect that to be the point at which fatigue cracks initiate. It would have been a much better idea to continue the ~1" tube to the seat tube, blending the stays into the side forwards of the seat tube.

^^^^^^^^^^^^^ Agreed. The frame is over 40 years old and seems ok. I will certainly not subject it to heavy use, I just needed another project.

Carlton green wrote: ↑17 Aug 2024, 9:09am

531colin wrote: ↑17 Aug 2024, 8:33am

Carlton green wrote: ↑17 Aug 2024, 7:54am ………I found some images of the Jackson frame on-line and note that the laterals are held well away from the seat tube by suitable stays, that’s not the case in some other manufacturers’ builds, and no doubt those stays are made of high strength material. To my mind those details would helpfully make the frame a bit stiffer in the appropriate directions. …..

The main determinant of the stiffness of a tube is THE DIAMETER. The twin laterals are about 10 or 12mm diameter? About as stiff as a fishing rod.
Gas pipe steel and fancy steel are not significantly different in density or stiffness .
The “stays” which space the laterals from the seat tube are about 8mm diameter.
They do look pretty, though.

The twin laterals on my Raleigh frame measure roughly 1/2” O/D, I’ve no idea of their thickness but that would matter too to their (individual and absolute) rigidity; the (between laterals) stays are also 1/2” and I believe that they are there to stop the (under compression) laterals from buckling - those stays will likely see very little load. The twin laterals triangulate the frame between the steering tube and seat post and then onwards to between the rear wheel too. The wider the base of that triangle the stiffer it is (in the plane of the tubes). Those are just my observations; you’re the expert on frames and very pleased I am to hear what you have to say too - every day’s a school day .

Try this;
Stand next to your bike, one hand on the handlebar stem, one hand on the saddle.
Test one; put a toe against the BB axle end and push the BB sideways.
Test two; alternating, push the handlebar stem away from you, pull the saddle towards you, then reverse ( push the saddle away, pull the handlebars towards.)
I won’t pretend these are objective tests which mimic the loads the frame is subjected to in use, but it is a rough and ready way to tell the difference between frames which are reasonably stiff and those which are woefully floppy.
Be interested in what you find.

531colin wrote: ↑17 Aug 2024, 10:55am
Try this;
Stand next to your bike, one hand on the handlebar stem, one hand on the saddle.
Test one; put a toe against the BB axle end and push the BB sideways.
Test two; alternating, push the handlebar stem away from you, pull the saddle towards you, then reverse ( push the saddle away, pull the handlebars towards.)
I won’t pretend these are objective tests which mimic the loads the frame is subjected to in use, but it is a rough and ready way to tell the difference between frames which are reasonably stiff and those which are woefully floppy.
Be interested in what you find.

Certainly, happy to do those tests for you.
For context I’m not the strongest man in the world, but rather likely mid range (for men in general) and a little stronger than most cyclist that I know.
Test one: the frame flexes and springs under a firm but not excessive load.
Test two: the frame is pretty much rock solid, there might be a bit of flex there, but if so then it verges on indiscernible .

Obviously I wasn’t sufficiently clear.
You need at least 2 bikes with different frame construction to compare; say a “man’s frame” and a couple of different types of women’s frames

tatanab wrote: ↑17 Aug 2024, 10:34am...... I just needed another project.

I have a very rare Paris (Rensch) 'Dame' frameset (with headset and seat pin fitted) I can't do much with it now, so if you want to refinish it/build it up that would be OK; all I would expect is a slice of the proceeds when it is finally sold.

531colin wrote: ↑17 Aug 2024, 12:06pm Obviously I wasn’t sufficiently clear.
You need at least 2 bikes with different frame construction to compare; say a “man’s frame” and a couple of different types of women’s frames

I have managed to break three steel frames commuting in London.

One was a standard male Trek hybrid: it had a lifetime guarantee and when Evans Cycles said: "Ah, but have you still got the receipt?" they were visibly annoyed when I pulled out an old scrap of paper from the 1990s. So I was given an aluminium hybrid as a replacement, which my younger daughter decided was hers and she still uses.

The other was mixte Claud Butler, given to me from the office car park, that had quite a brief run. In both cases doing curb hops did not help, I suspect.

So I moderated my riding - and I was sorry about the Claude Butler - when I bought the Carlton mixte frame: the most expensive bike I have ever bought, as it cost £27 on eBay but I went up to Conwy to pick it up with the family and we made a long weekend of it.

That, too, broke, when one of its front forks snapped off in Parliament Square. Or, rather, I noticed it was broken clean through there. I actually managed to ride the bike home, with the broken fork still absorbing the road. It only fell out when I put the bike in the stand and released the QR.

By this point, I was no longer rushing about to the same degree or abusing the bikes, so I think it was just metal fatigue. So I got some nice chrome forks as a replacement. I am hoping the Carlton will see me out. The only bike I do hop a curb on nowadays is the steel Marin MTB, which is built for that sort of thing.

However, I do happily overload the Carlton mixte - a half-mile supermarket shop this afternoon with 4 bottles of 2 litre fizzy water and other groceries filling two Ortleib panniers, for eg - but it seems to put up with this OK, although I do notice a bit of swaying and I am gentle with it these days.

Brucey wrote: ↑17 Aug 2024, 12:27pm

tatanab wrote: ↑17 Aug 2024, 10:34am...... I just needed another project.

I have a very rare Paris (Rensch) 'Dame' frameset (with headset and seat pin fitted) I can't do much with it now, so if you want to refinish it/build it up that would be OK; all I would expect is a slice of the proceeds when it is finally sold.

Does it look anything like this? Immensely 'cool' or 'cul' as the French say:

After link to a dropped top tube bicycle, which perhaps indicates that such bikes are not without strength https://theradavist.com/hope-cyclery-bu ... -platypus/

Bice wrote: ↑17 Aug 2024, 7:38pm

Brucey wrote: ↑17 Aug 2024, 12:27pm

tatanab wrote: ↑17 Aug 2024, 10:34am...... I just needed another project.

I have a very rare Paris (Rensch) 'Dame' frameset (with headset and seat pin fitted) I can't do much with it now, so if you want to refinish it/build it up that would be OK; all I would expect is a slice of the proceeds when it is finally sold.

Does it look anything like this?.....

kind of, but it doesn't have curved tubes. FWIW 'cul' is French for something else.

531colin wrote: ↑17 Aug 2024, 12:06pm Obviously I wasn’t sufficiently clear.
You need at least 2 bikes with different frame construction to compare; say a “man’s frame” and a couple of different types of women’s frames

Test one: on a traditional diamond touring type frame. To my surprise, the deflection was either no different or greater than on the Mixte; the particular diamond frame seemed more fragile, but it’s never been anything other than perfectly fine on the roads.
Test two: rock solid (again) as anticipated.

I have 4 step through frames, 2 twin-lats and 2 anglais style with dropped top tubes. One of the twin-lats is a 531 Raleigh Richmond and it rides like a garden gate. The other is a 531 Dawes Lady Galaxy and it handles much better with less flex. This is probably due to the lateral stays terminating on the seat stays above the drop-outs. This would be suitable for day rides but I would not use either for loaded touring. Both frames have now been retired.
The two anglais frames started life as conventional Surly diamond frames which I had to have modified due to a medical problem. The first frame is a Cross Check and although it handles well there is a small amount of flex but this serves me well for day rides and is not a problem. The other is a LHT and with this I had the dropped top tube higher than on the CC. This frame is rock solid and is my go to touring bike. Both bikes have now been fitted with Tongsheng conversion kits which do not affect the handling. Incidentally the LHT frame is lighter than the Raleigh.
From my experience I could not recommend a twin-lat for serious touring, but Anne Mustoe rode a Condor twin-lat on her round the world journey, so there may be some decent frames out there.

Carlton green wrote: ↑ Test two: rock solid (again) as anticipated.

Push harder! Imagine how much force you exert out of the saddle uphill