Author Topic: What do you call a frame without a top tube?  (Read 919 times)

Andre Jute

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What do you call a frame without a top tube?
« on: December 06, 2021, 02:47:58 PM »
Suggested by a phrase in a post elsewhere from Martin, to whom thanks:

"ladies" frame twin-lateral bike

I like parallelogram because it doesn't imply that twin-laterals are parallel to the ground. Mind you, if we're about to split hairs (or frames), trapezoidal frame would be even better because it includes twin rails that aren't parallel and also the fact that the head tube and the seat tube are differentially angled where they close the ends of the whatever-you-call-them rails and therefore of different lengths.

There's also trapeze, which I'm assured (from the Continent) was once a common descriptor also in use in Britain. But I'm particularly keen that my bike shouldn't fly...

You might enjoy this for the section about what the name mixte should be reserved for (though American readers had better give it a miss to save their blood pressure):
https://groups.google.com/g/rec.bicycles.tech/c/LqY0UpZTIP0/m/L-2d5vPiSW4J
A mixte is a relatively low stepover frame with two thin rails running from the head tube, passing either side of the seat tube, all the way to the rear dropouts so that in profile the bike looks like it has three stays at the back rather than the usual two.

Andrew Muzi, a notable LBS near Mickeg, uses open frame for any frame without a top tube that isn't for ladies.

The frame that looks like a U to provide an ultra-low stepover is called a wave.

What other frames do you know? What were the names of the unique low stepover frames Thorn offered?
« Last Edit: December 06, 2021, 06:47:46 PM by Andre Jute »

energyman

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Re: What do you call a frame without a top tube?
« Reply #1 on: December 06, 2021, 04:52:29 PM »
It's either "U" or "Non U" as far as I'm concerned.
R&M Nevo is very "U"

j-ms

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Re: What do you call a frame without a top tube?
« Reply #2 on: December 06, 2021, 06:32:42 PM »
To answer the question about Thorn's term, my missus rides a Raven Step-Through mit Rohloff.  Looks like a ladies bicycle but is up to hard touring as well (Africa, Patagonia etc).  She can't get her leg over (no sniggering please) the saddle so the Step-Through is perfect for her.  The attached image shows my standard Raven (post Raven Tour/Sport) and Raven ST (plus the missus) together in Santa Lucia, Chilean Patagonia.
« Last Edit: December 06, 2021, 06:46:13 PM by j-ms »

Andre Jute

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Re: What do you call a frame without a top tube?
« Reply #3 on: December 06, 2021, 08:19:36 PM »
To answer the question about Thorn's term, my missus rides a Raven Step-Through mit Rohloff.  Looks like a ladies bicycle but is up to hard touring as well (Africa, Patagonia etc). 

I'd be tempted to call your wife's bike, a catholic mix of design styles, a blessed cross frame step-through.

Super photo. I've been to Puntas Arenas, though not by bicycle.

It's either "U" or "Non U" as far as I'm concerned.
R&M Nevo is very "U"

At those prices it had better be. My bike has more battery power on board than their base model, and the battery is already hefty. One wonders where they'll put twice that much battery weight on their top bike without unbalancing the bike.

How is the phone controller protected against rain?


martinf

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Re: What do you call a frame without a top tube?
« Reply #4 on: December 06, 2021, 08:50:06 PM »
My wife's current preferred bicycle frame type is known by the name "Col de Cygne" here in France. That translates to "Swan Neck". It is the red bike in the first photo that is (hopefully) attached underneath this message. That frame type is rather fragile, but gives a low stepover height.

The "Mixte" frame in France (and I reckon elsewhere) is one with the twin-lateral tubes running straight from the head tube to the rear dropouts. Our old black "visitor bike" in the second photo is of that type.

Both these photos are old, as those two bikes now have Chaingliders.

The "twin lateral" bike I had back in the 1980's looked like the pink bike in the 3rd photo, but was much tattier (two different sorts of green paint with some assorted rust spots), which helped reduce it's thief-appeal.  The twin-lateral tubes more or less run parallel to the down tube at first, then bend upwards a bit, then bend downwards again after the seat tube to meet the rear dropouts. I don't know what the correct name for that type of frame is, it gives a lower standover height than a true "Mixte" frame, but is less stiff and (probably) a lot more fragile if used hard.




« Last Edit: December 06, 2021, 08:53:25 PM by martinf »

energyman

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Re: What do you call a frame without a top tube?
« Reply #5 on: December 06, 2021, 09:27:34 PM »
How is the phone controller protected against rain?
Dunno, I went for the Bosch Intuvia, keep life simple is my motto.

John Saxby

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Re: What do you call a frame without a top tube?
« Reply #6 on: December 06, 2021, 11:16:55 PM »
In the bike-recycling organization/shop where I volunteer twice a month, we use "Step-through" as a generic non-gendered descriptor, and that seems to work well both in-house and out-house (as it were.) So we're quite comfortable with Thorny nomenclature, without acknowledging it as such. (OTOH, "Step-Thru" would bring forth loud & extreme mockery, as you might guess.)

Occasionally, we receive donations with mixte frames--a frame I always liked, even before I knew it was a thing--and we call them that amongst ourselves ('cos we're In The Know, y'know).  I've noticed that some customers aren't so sure about that, however, so unless someone asks if we have any bikes with mixte frames for sale, I avoid the term.
« Last Edit: December 06, 2021, 11:20:05 PM by John Saxby »

Andre Jute

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Re: What do you call a frame without a top tube?
« Reply #7 on: December 06, 2021, 11:30:12 PM »
Thanks for the photos, Martin.

I get Col de Cygnet. It does look like Swan Neck; a graceful style.

The last style, the semi- or modified-mixie with the 3D rails curved over the seat tube, I suspect is likely eventually to become a victim of its own cleverness. You can eyeball it and then eyeball the two Thorn step-through bikes, and know without further information which is the serious touring bike with considerable frame stiffness. But it is an appealing bike to those who would paint it pink, so there is at least one I know of still in production and selling well enough to keep it in production.
« Last Edit: December 06, 2021, 11:33:37 PM by Andre Jute »

martinf

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Re: What do you call a frame without a top tube?
« Reply #8 on: December 07, 2021, 10:00:17 AM »
Our current "small" visitor bike has one of the older Thorn Raven Step Through 390 frames, very small and short. Chosen because I reckon this frame is tough and should resist anything that careless visitors throw at it. The current Thorn Nomad Step Through frames are longer, with a higher standover height, and they are much stiffer for better luggage carrying capability.

This Raven Step Through 390 is best suited for small people, and set up for a VERY upright position.

I can (and sometimes do) ride it with the saddle near the maximum height (2nd photo) but unlike the bikes shown in my previous post it isn't very comfortable as the frame is much too short for me.

Not what I got it for, but it is a much better load carrier than the 1st and 3rd bikes in my previous post, and a bit better than the black "Mixte" frame bike.

j-ms

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Re: What do you call a frame without a top tube?
« Reply #9 on: December 07, 2021, 11:07:55 AM »
Martin, your Raven ST looks very different from my wife's Raven ST which was bought in 2016.  What vintage is yours ?

martinf

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Re: What do you call a frame without a top tube?
« Reply #10 on: December 07, 2021, 12:51:19 PM »
Bought fairly recently, but these small frames predate the change from Raven Tour and were advertised at bargain prices as clearance items.

Andre Jute

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Re: What do you call a frame without a top tube?
« Reply #11 on: December 07, 2021, 02:58:01 PM »
j-ms & martinf:
The Thorn's 390 and 420 step-through frames, when I looked at them about a dozen years ago when I was preparing to be old(er), had different tube sets and different cross-framing, and therefore different profiles. They were fundamentally different bikes. Also, I seem to remember that (it was said on the forum or perhaps in the literature) that the 390 was the smallest bike for the smallest people that Thorn catered for (and over the years we had several small people who queried the forum about a source for a suitable bike, and some who stayed around after they found their dream Thorn), while the 420 was capable of accommodating a range of sizes up to quite tall people. Compare Martin's photo of the 390 above with the 420 S-T photo below:

At the time I was looking at a lot of easy-mounting bikes and went into the history of the cross frames and wasn't surprised to discover that the 420 was rated for greater weight of rider and touring luggage than the 390. Just eye-balling the frames and counting the lateral bulkheads in substantial tubes already tells you these are both stiffer frames than the common shopping step through, with the 420 stiffer than the 390. Finite element analysis would probably be a bit frustrating but is hardly necessary to conclude the obvious.

John Saxby:
If the purpose of the organization you volunteer for is raising money for a charity rather than getting local people on bicycles, you could advertise the mixte you get on California's Pacific coastline. There was a report by a Californian who keeps his eye on such matters that second hand bikes, and especially mixte, were snapped up the moment they were advertised.

John Saxby

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Re: What do you call a frame without a top tube?
« Reply #12 on: December 07, 2021, 05:32:06 PM »
Thanks, Andre. 

www.Recyclore.org is a neighbourhood organization, wholly voluntary.  We accept donated bikes, bring them to roadworthy status, and sell them at below-market rates -- most are in the $100 - $250 range.  We're essentially a bike-recycling operation, making bikes available for people who may not be able to pay market rates, or don't want to.  We do advertise our higher-end bikes on Kijiji, a regional marketplace.