Cycling UK Forum

531colin wrote: ↑18 Aug 2024, 5:01pm

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

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

to do this kind of test properly, I suggest the following;

1) start with whichever frame you expect to be stiffer. Push hard enough to cause ~1/2" deflection.
2) push with the same force on the other frame, and compare the deflection.
3) revert to the first frame and do the test again, just to be certain that you are not fooling yourself.

IMG_5858 by 531colin, on Flickr

Thats my "stiffest" bike, due to the enormous downtube which contains the battery.
But it isn't "rock solid"....pushing and pulling the saddle/handlebar stem, the frame flexes.

IMG_5662 by 531colin, on Flickr

This bike with oversize and ovalised titanium tubes is less stiff than the e bike, but stiffer than a bike with the old standard inch and inch and eighth steel frame tubes.

I have just tried the stiffness test with my two anglais framed Surly's compared to a Spa Ti Tourer. The LHT was about the same as the Spa with the Cross Check less stiff. This is what I would expect as the CC has a lighter tube set than the LHT and a smaller o/d than the Spa, I cannot test either of my twin-lat frames as they are not built up, but I can almost guarantee that they would show even more flex.
Way back we had an Orbit tandem with a single pair of twin laterals running from the head tube to the rear drop-outs. Pushing hard uphill we could feel the frame flexing from side to side. Eventually a chain stay cracked and the frame was a write-off

Remind me again what "Anglais" means?
Its a very long time since I measured up a few LHTs, but I was amazed to find they used exactly the same tube sizes on all the different sizes of frame; and that was a big size range. (I always used bigger top/down tubes on the bigger Spa bikes; never got round to bigger seat tubes, but that would have been at least as sensible as the tubes I did.)
Somewhere Brucey is speculating that if the difference in frame size makes the tubes on the big bikes 20% longer, then the smallest frame will be TWICE as stiff as the biggest.
(I didn't have Brucey's assistance with the Spa frames; a great shame, in retrospect.)

I recruited somebody about six and a half feet tall and over 20 stone as my "big bike tester". He had an LHT at the time, and he complained that when he put the power down he could make the chain rub on both sides of the F. mech. cage. He could put the power down, mind.

'Anglais', as in English style step-through with a lowered top tube. Below is a picture of my modified Surly LHT. All my frames are 54cm and the LHT is a pretty robust frame weighing 3.8 kg. Down tube is circa 32.5 mm o/d. I cannot comment on the gauge of the tubing but as it is a smaller size I am not surprised that even with a lowered top tube it compares well with the Spa for stiffness.

531colin wrote: ↑19 Aug 2024, 4:30pm Remind me again what "Anglais" means?

Basically a lowered top tube and now’t else. See: https://www.biketinker.com/2014/bike-ar ... gh-frames/ .

I think it (Anglais) a bit of a loose description and, all else being equal, the stiffest frames will have the least lowered top tube. The traditional form of that frame had a very lowered upper tube, some were straight and some curved.

Try Google Images for: Raleigh Ladies Traveler and Rudge Ladies Bike

This old BSA catalogue shows vintage frames too: https://oldbike.wordpress.com/1955-bsa-catalogue/

531colin wrote: ↑19 Aug 2024, 4:30pm..................(I didn't have Brucey's assistance with the Spa frames; a great shame, in retrospect.).....

I would have been flattered for sure but I doubt that I would have done much that was actually useful!

velorog wrote: ↑19 Aug 2024, 4:12pm I have just tried the stiffness test with my two anglais framed Surly's compared to a Spa Ti Tourer. The LHT was about the same as the Spa with the Cross Check less stiff. This is what I would expect as the CC has a lighter tube set than the LHT and a smaller o/d than the Spa, I cannot test either of my twin-lat frames as they are not built up, but I can almost guarantee that they would show even more flex.
Way back we had an Orbit tandem with a single pair of twin laterals running from the head tube to the rear drop-outs. Pushing hard uphill we could feel the frame flexing from side to side. Eventually a chain stay cracked and the frame was a write-off

Another confounding factor here is that titanium is about one third less stiff than steel, as well as about one third less dense than steel; there is no "free lunch" in making titanium frames!

https://catalogue.bnf.fr/ark:/12148/cb361443407 discussed by the late Hirose San here:

subtitles available

Several lower top tube designs:
https://www.youtube.com/@HiroseMuseum/videos

Mr Hirose knows what he is talking about !
Anyone considering "twin lats" should view the video and take his advice.

Sport NOT Mixte.

Brucey wrote: ↑19 Aug 2024, 9:50pm

531colin wrote: ↑19 Aug 2024, 4:30pm..................(I didn't have Brucey's assistance with the Spa frames; a great shame, in retrospect.).....

I would have been flattered for sure but I doubt that I would have done much that was actually useful!

If nobody minds indulging me, there is something which has been nagging me for a while.........

1...My titanium bike shown above (Elan) feels different to all my other purely leg powered bikes, in that it appears to accelerate as soon as I push the pedal a bit harder just once....its also the stiffest of my purely leg powered bikes. Is the stiffness shown by the "foot on BB axle end and push" test any sort of reflection of how quickly a bike accelerates with that first harder push on the pedal?

2...If a seat tube is going to fail due to fatigue, it will (usually?) fail a bit above the bottom bracket shell; even on bikes made of plain (un-butted) tubing. I think I remember Brucey posting something like "displacement of the BB due to pedalling forces is reacted almost exclusively in the seat tube".

Observations 1 and 2 appear to me to be contradictory; the seat tube isn't really fixed to anything except the riders backside and the road, but its fixed to the road via the tyres, wheels, and the rest of the frame.
....so the "rest of the frame" also reacts pedalling forces?

Can anybody help me with an explanation which would make sense to a simple biologist?

There's a lot of interesting stuff in this thread, even for someone who has never owned a bike with a lowered (or absent) top tube, of any pattern.

LucyEliz wrote: ↑14 Aug 2024, 3:40pm

Carlton green wrote: ↑4 Aug 2024, 7:00pm There’s a good list of reputable ‘women’s’ frames here: https://www.cyclingabout.com/a-complete ... ugh-mixte/

That's a great list. It's worth pointing out the perhaps obvious fact that in the EU frames that are considered 'ladies' frames here in the UK are just regarded as unisex bikes, and as far as I can tell, the majority of utility and touring riders use them.

Indeed. I was thinking as soon as I began reading this thread, the question of whether or not a rider wants a "lady's frame" should not be whether they're a woman but whether they will ever ride in a skirt, kilt, priestly robe or one of the many varieties of wrap-around clothing worn in parts of Asia, Africa and the Pacific by both men and women. Or, of course, whether they need a lowered top tube due to eg arthritic hips or damaged knees.

Bice wrote: ↑17 Aug 2024, 6:09pm

Ouch! You're brave riding that!

On the Paris frame, does the loop of tube joining the down tube to the laterals add much/any stiffness?

Some vintage ads list an Eclesiastic Model,which has a 'dropped' top tube ( commonly referred to as a 'ladies frame' )( Yes I have read the various descriptions above )

stevegreen wrote: ↑20 Aug 2024, 9:44pm On the Paris frame, does the loop of tube joining the down tube to the laterals add much/any stiffness?

I think the question before that would be “ Do the laterals add much stiffness?”
I’m guessing they are even thinner than some other laterals, maybe closer to 10mm than 12mm? Tubus carriers are 10mm steel tube, for comparison.
“Paris” by the way was a London frame builder with “form” for some odd designs; Paris Galibier for one, and they were also responsible for “Harry Rensch” tandem frames with 2 sets of twin laterals. ..OK with a child stoker….