Berd polymer spokes

Everything about building wheels, glueing tubs, etc.
TheKaiser
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by TheKaiser

http://www.bikeradar.com/road/news/arti ... kes-51391/

There was a little off topic discussion about these in an Enve rim thread, but I figured they deserved their own. Anyone ever seen them in person, or care to make some wild speculations about them? They have an interesting method of affixing to the hub. On the one hand, it seems like a hack job, but on the other hand it is ingenious how simple it is. Rather than trying to bond on a metal fitting, the spoke has an all fiber eyelet at the end. You simply thread it through the hub, and stick a metal bar through the eyelet to keep it from getting pulled through. The system works with both conventional and straight pull hubs.

Spokes are not aero shaped, but are much thinner (1.8mm) than something like Spinergy Spox, so they at least aren't worse than a conventional steel spoke in that regard. No real info on elasticity.

bm0p700f
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by bm0p700f

interesting. no idea what to make of it. there is no good reason why poly propelene is not a good material but the weak spots are the nipple end and the rod that hooks into the eyelet. that rod is if not made right could be a good source of failures. It is really hard to know how well these spokes would work.

They have 2g over a sapim CX-ray. I think Ti spokes are a similar weight. Also does the 2.3g per spoke include the metal rod?

by Weenie


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F45
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by F45

At least their graphs are clearly made, starting at zero on the Y axis. But strength is not stiffness and they don't mention any of the downsides. I would be interested in their resistance to abrasion and how much a nick decreases their strength. The article reads like an advert. Not really good journalism.

But I think in order to be a journalist, you have to take an intelligence test. Everyone who fails the test gets to be a journalist.

JackRussellRacing
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by JackRussellRacing

To F45's point about abrasion: in my "real job", I sell Ferrari, Maserati and Lamborghini car parts. We have Ferrari bumper skid plates made from UHMW polyethylene -- and the stuff is crazy light and brutally strong. The pieces we offer are designed to bear the brunt of a 2000# vehicle scraping on a concrete curb, and they do it with some amazing durability.

I'm not an engineer, but it sure seems like the same material, albeit expensive, would make a suitable bicycle spoke. The eyelet thing will likely be the most challenging part of the durability equation, but UHMW polyethylene in itself wouldn't worry me.

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F45
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by F45

Looking at the tensile strength of 18-8 vs this stuff, it looks like UHMW polyethylene has a tensile of 48 MPa vs 620 MPa for 18-8. It is 1/8 the density.

FilmAt11
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by FilmAt11

Here’s a shot of the hub connection at their site on the custom page. You can see a “bar”, but it just looks like a segment of the spoke material.

Image

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kavitator
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by kavitator

How much spokes strech at 120kg?

joejack951
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by joejack951

I had to do some reading to understand what's going on here. UMHWPE in its typical form (a block plastic) would make a terrible spoke. It has little tensile strength in comparison to most engineering polymers and it is going to creep when subjected to a constant load. However, Dyneema and Spectra (referencing Wikipedia here: https://en.wikipedia.org/wiki/Ultra-hig ... lyethylene), both oriented strand gels made from UMHWPE, are totally different beasts. They have yield strengths comparable to high strength steel but at a much lower weight. To be honest, I find these spokes very intriguing but I am concerned about the nipple and hub terminations as well as the general recommendation to not use either of those fibers are temperatures approaching 180 degrees F (a common temperature seen inside automobiles on a hot day). Given the constant pulling force these spokes will be under, I am very wary that they'll hold tension on a wheel for long especially on a hot day.

C36
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by C36

F45 wrote:Looking at the tensile strength of 18-8 vs this stuff, it looks like UHMW polyethylene has a tensile of 48 MPa vs 620 MPa for 18-8. It is 1/8 the density.
Not really familiar with the exact type of material used and how it is put in shapes (appears the fibres are at 45ish degree) but looking the stiffness properties (young modulus), except one document mentioning a max above 170gpa they use to vary between 60and 120gpa.
http://www.mse.mtu.edu/~drjohn/my4150/props.html
In absolute that's quite fantastic since for pure traction it represents an amazing stiffness to weight ratio (even if will be degraded with the 45deg pattern)... now looking in the table we see that PBO has better numbers (heavier but a lot stiffer) but spinergy tentatives to deploy PBO spokes had been so so...


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bm0p700f
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by bm0p700f

I am still trying to find reasons why the spokes are an issue. I am going to enquire in the new year and build a test set of wheels and see if nerd will supply the spokes.

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LeDuke
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by LeDuke

bm0p700f wrote:I am still trying to find reasons why the spokes are an issue. I am going to enquire in the new year and build a test set of wheels and see if nerd will supply the spokes.
I exchanged messages them once upon a time a year ago.

I'd like to buy some for my FS MTB. Can't find any way to do it, though.

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ergott
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by ergott

I inquired a while back and was told they aren't ready to offer spoke kits. They want to build in house to control quality. They did say they'd revisit the idea at some point.


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UpFromOne
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by UpFromOne

They emailed me back and said the rim-side section with the poly fiber over the metal was pretty thick, so you can't just slide them into a hub - each end of the spoke has to insert the rim/hub side on its own.

I had suggested they place a ball end or similar head on the hub side, instead of that loop&rod setup, which just isn't right.
Then to allow the spoke to slide through a hub flange w/ std. 2.4mm holes, the rim end metal diameter could be reduced to 15g or even 16g instead of the 14g, so that the fiber wrap over this metal section will be less than 2.4mm OD (i.e. the size of a hub hole). I don't think they considered that; they were so concerned about the material properties that they just grabbed some 14g spokes, cut them very short, slid the poly over them, and glued in place. But that part of the spoke has got to be at least 2.8mm thick, and to me that diameter is a design issue.

In short, I'd slim down the spoke ends, and give them a proper head so they can slide into hubs as they were intended.

bm0p700f
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by bm0p700f

If one end has a loop to attach to the rod then the other end does not need to go through the hub. Place the spokes in the rim all the rods in the hub and attach. Probably fiddly and confusing at first but better than a 1.8mm thick spoke entering the rim.

by Weenie


UpFromOne
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by UpFromOne

Update: in one of my final emails with Brad, he said the loop end is simply secured in the flange with another short piece of the poly.
So it isn't a solid rod, just another piece of fabric. Which given the dynamics and weather exposures, would have me be even less inclined
to ride them. While that short piece through the loop may not dig into the hub, any micro-wear might result in a loss of spoke tension.

So I will watch this product, but not be my usual "early adopter" on this one.

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