From the first time I saw this photo I was intrigued. The unusual frame, well worn and soiled and a very serious chap looking on. A little research led to the discovery that the frame was based on a new design concept ( new for the 1930's) called Tensegrity (tensional integrity). Wires under tension compress the beam to create a very rigid structure.


Curiosity killed the cat ya know...so I went to see Steven, the owner of the Bike Stand my LBS

It is an interesting concept...



That has endured to this day...

After a few visits and lots of questions; it seemed neither of us had a clue as to the working details of the bike but it was interesting. Steven, having a the tools skills the braze frames and my persistance seemed to warrant a go at it! (Experienced frame builders and detail oriented folk should stop reading at this point.....it starts to get ugly.)

I produced some measurements from the photo and from a bike that had been fitted for me. The paper laid on the table for a few weeks until winter hit. In January I had my first look at what was to be the frame; a pile of tubes, some cut others marked. The odd angles meant no lugs other than the fork crown, everything would be fillet brazed. This evening when I visited the shop, the tubes were off the jig and sitting on the floor with a wheel locked into the droputs.

The front wheel will be used for this build, the matching rear will be built up as a flip/flop or an IGH. ( the rear wheel in the photo was borrowed for the pic.) I'm hoping for a few things: to finish the build with a mix of new an older appropriatley styled components, that it will work, and to learn a little in the process. I'm thinking this is going to take a year or so to complete, so as it moves along I'll post pictures and hopefully a ride report here.

Jeepers.

Suhweet !

Outstanding thread.

Cool for sure.

Subscribed! Looks awesome. Have you thought far enough ahead to think about painting/powder?

Very, very cool.
Very.
I want one .

I have seen photos of that wire bike with the wires crossing. Looks like fun.

Have you thought about fenders? Will you show as much seatpost? And look at that interesting stem on the original in the first photo.

WOW. This is seriously cool!

Nice! Will this become your clubman style bike? The handlebar on the original looks almost like a Lauterwasser. I suspect you'll have this together in less time than your post suggested.

I think we're getting ahead of ourselves here folks. Forget fenders, components and what color the thing is going to be, what about the most integral component of all.. the wires.
I'm very curious to see how this turns out, very cool project, this is the kind of stuff I like to see.
How are you going to properly tension the wires? If I were you I would select a wire with a much higher tensile strength than what you'll actually be tensioning it to, like a safety factor of 3. If one of those were to snap, it'd probably be pretty ugly.

probably explains the pissed look of the gent in the first photo...........

A turnbuckle? Plus some split pins?

Lauterwassers, fenders, clubbike; you bet!

The wires? the top and bottom tube wires are crossed. the rear forks and stays are singles. Here's what ive been thinking.

1/16 ss 304 wire has a working load limit of 110lbs which means failure happens around 1000lbs.

2 toptube wires, 2 bottoms = 440lbs with a failure around 4000lbs over the complete frame not counting the structural integrity of the tubes themselves. Please, anyone with an engineering degree, please step in an save me, my family would greatly relieved.

I've also though about 3/32' wire but that seems like overkill and any weight reduction would be lost in the weight of the tackle

The wires will be tensioned with turnbuckles. Tension will be checked by monitoring movement of the tubes and with the use of a spoke tensioner. I have no idea as to the what that tension should be, my guess when the ride is good, that will be the #

SS turnbuckle for tensioning:6 1/4 x 1/4

Very very cool. I'm enchanted! Do let us know how it turns out.

Here's the model railroader in me speaking: Turnbuckles were used in early truss bridges that used steel rods in tension, e.g., for what is called the "bottom chord." You (and the bridge-builder) have to make sure that the wires (and rods) are tight enough that they never slacken during the stress reversals that occur in use. If they go into compression they will fail. (When a heavy locomotive pulling a high-speed train comes onto a bridge, parts of the bottom chord that is normally in tension when the load is just sitting motionless on the bridge will experience compressive stress, sort of like the bottom spoke of a bicycle wheel does.)

Wire can be made to carry very high tension. The weak points I would think will be the attachments to the frame tubing which have to bear that high tension while exposed to the elements. (This was the problem with rod-truss bridges too, and they were too "bouncy" to bear the oscillating impacts of the really heavy steam locomotives that came along in the 1930s.)

@conspiratemus
Good insight, definitely an applicable comparison.

I can't help you with what kind of numbers you should shoot for (for tension) but hopefully someone with some understanding of the tension/compressive forces exerted on a bicycle frame under normal use will chime it. I would agree with Conspiratemus that you will need to avoid letting the wires unload enough to slacken and any failure is likely to happen at the connections as opposed to the wires. I would definitely select high grade hardware, with pins the size of the ones you pictured and eyelet ends on the cables with long swaged sections, which will probably have to be custom made.

This bike on the Bay has a similar stem. Never seen one before. Might justify the purchase of the bike. Haha.

https://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

The priciple of tensegrity is that all the wires are in constant tension to produce a rigid structure. I have to determine or estimate the anticipated force. The trunbuckles and swaged ends are all available through the marine industry. Standing rigging on sail boats deal with incredible forces, much greater than what one would expect from a bicycle.

Oh yeah. This is deserving of the word awesome.

What a great project! I think I actually have one of those 1930s swan-neck steel stems. It came on my '37 Raleigh Sports, and I swapped it right out immediately. It's yours for the cost of mailing, Mr. Gnome, if I can find it. PM me if interested.

Neal

I know it's a little late for this particular comment, but since this is all talk anyway....

In the photo, can anyone reaad what's written on the top of the "top tube"? I can't, but the shape of the lettering suggests to me that the tube itself is ovalized or elliptical, which would make sense-- it has to add lateral strength.

Ahhh, marine hardware. Now yer talkin' big bucks! But very sexy industrial jewelry.

Something like this?


Designed by Frans de La Haye in 1972. Union built a prototype, but there seems to have been a problem with lateral stiffness and it was never taken into production.