FBinNY 

Side note to this thread.

I note what may be a correlation between age and perspective about things like spoke tension.

It might be interesting to see if there's a dichotomy between those who were experienced (skilled?) wheel builders before 1981 and those who learned later.

Ryan_M

Not sure if that's sarcasm or not... that plot is horrible if I'm reading it right! Spoke #3 shows ~-48% tension or 52kgf, spoke #1 shows ~-32% or 68kgf. Thats an approximate 30% difference in tension from spoke #3 to spoke #1.

mpetry912 

OK, let's see you do better !

Post your plot when done.

/markp

Ryan_M

OK will do. What software package is that? The Park one wont work for me since the tensionometer reads completely different and I can't define my own conversion.

Duragrouch

I prioritize rim trueness first, with priority of radial first over lateral, and then adjust lateral easily, then try to even spoke tension as much as possible without affecting the rim true. Sometimes it's just a matter of adjusting laterally opposing pairs together, and with the spoke threads being relatively fine, doesn't take much to make them more even tension without noticing any rim runout. (I just ring, no tension meter, but I should get one, though accuracy may be difficult with short, straight-gauge spokes on 20" rims, spokes are inherently laterally stiffer.) My view is, as long as at good minimums so the bottom spokes don't go too loose under rolling, that's not the issue; It's about the other spokes (top and side) bearing the stress/strain as equally as possible. That's always a good thing, as lowering peak stress even a little, can have a big improvement in fatigue life. But if they have to be a bit unequal for a true rim (or a lot for an old rim), I'll accept that. Qualifier: Not a pro, not a wheelbuilder, just an engineer.

FBinNY 

This is not an attack, but a reminder.

If one wants to think like an engineer, one has to start by identifying the problem.

Spokes consistently break at the elbows, and no place else. So, that's where one needs to focus. All the argument about tension are a distraction.

Think about WHY elbows fail, and address that first in order to build lasting wheels.

ScottCommutes

Interesting. Back in the day, robots didn't build wheels, and nobody could make a digital chart of their spoke tension. Yet somehow everybody did just fine by look, feel, and sound. Nobody learned about it on the internet, either.

Edit: Did they even have those spring tension gauges back in the day?

FBinNY 

Yep, we were all too stupid to know you can't do it that way.

ScottCommutes

I posted in another thread about tuning a piano. I can tune a piano - it isn't crazy hard. However, my tuning won't stay in tune, because I inadvertently leave a subtle twist in the pins themselves. I lack the feel to know when I'm twisting a pin vs. when I'm turning a pin. In other words, I leave unnecessary tension that (over time) gradually works itself out. My intuition tells me that a bike wheel would be similar.

Ryan_M

I wonder if this is a reason wheel building had(has?) the reputation of being such a black art. It had to be done mostly by feel and intuition, and needed extensive experience. Now we have better tools, digital tensionometers, and online resources to break down the data. I'm a numbers person so the latter greatly helps me get a feel for what's going on, others it may just confuse the issue. At least it helps someone like me to be able to build a reasonably good wheel.

FBinNY 

Everything has its little quirks that separate experienced technicians from those less so. The twist analogy is especially apt because managing spoke twist is one of those subtle skills.

Twist was more of a problem BITD, when we were using 15g DB spokes for race wheels. So it was SOP to tell a client to ride a few hard miles then come back for a touch up.

These days, twist is less of an issue when building new, but still something one needs to learn to feel, especially when truing older wheels. Basically the spoke initially twists before the nipple actually does anything, then you need to relax it back. So every adjustment is akin to 3 steps forward and two back.

When I taught building, this was thd hardest thing, because it's all about touch.

FBinNY 

I think you've found the essence of the difference between older and newer builders. It's in the culture.

Those who learned before the internet, focused on skills rather than "better tools". Our better tools were the little tricks learned from masters.

In another thread, I posted a method to build quality wheels quickly and easily without the tools many have come to rely on. it's highly abbreviated but the big picture is clear.

Those willing to throw off the training wheels might give it a shot.

ThermionicScott 

Well that's not true. If "everybody" did a great job of building wheels, we would have very few occasions to discuss wheels going out of true and breaking spokes apart from overt damage.

ScottCommutes

This thread is especially timely for me because while my rear wheel is true, the axle and bearings are shot. I'm trying to decide whether I should take the wheel apart and install a new hub (that I have), or go ahead and spread the bike to 135mm to accept a brand new wheel (that I also have).

Ryan_M

Easy now. I delve into building wheels because I like the tools, making my own equipment. And the analytics. It's not always about the fastest route to a end product. I like fussing over it, looking at pretty graphs, and chasing numbers. It gives me my OCD fix. I also make telescope optics by hand and enjoy the analysis and getting as close to perfection as I can where tolerances are measured in the 10s of nanometers. I've made enough of those to last me years, so this is the new thing.

mpetry912 

that is Spoke Service dot CA using the Wheel Fanatyk V2 tensiometer with the digital readout to USB

Not sure if your unit will output a measurement that can be read via USB.

/markp

mpetry912 

Depending on the hub, maybe you can swap in new axle and cones ? That's cheap and cheerful

/markp

ScottCommutes

Yeah, that is a possibility, I have the parts from the other hub that I could grab. They would work. I think the reason the bike bends axles is because they don't sit squarely in the dropouts, so I need to fix that as well.

Duragrouch

Good point. I've only build one set of wheels 40 years ago as a complete newbie, only truing jobs since then. I can't recall if the Jobst book or somewhere else, where it shows stress relieving the spokes by laying the wheel on the floor and stepping laterally on the spokes with your foot in shoes. I've never done that, just felt a bit imprecise and possibility for damage to me; I know a lateral push on a taut cable, rigidly attached, can increase the tension in multiples.

I do know that on the DeHavilland Comet, the problem was not just a design issue, but failure to detect that issue in pre-production testing, and this was because they used the same sample for both "proof" (over) load testing, and then fatigue testing. The overload stress-relieved the area of design deficiency, thus no failure in fatigue. Actual production airplanes did not undergo that proof loading, put into service, failed in fatigue and explosive decompression. It had been thought that double-testing the same sample would be worst case, but it was not.

So I know there is value in stress-relieving.

I'll look at your link for your wheelbuilding instructions. EDIT: Oh, yes, I had already seen that post.

Ryan_M

Thanks! I'll look into that at some point but I ended up writing my own thing in Excel. It's obviouly not as polished and looks romper roomish but I like being able to manipulate the data. This is what I'm looking at.



FBinNY I'd like to hear your feedback on this - so far. I saw you mentioned in another thread about maintaining length, this is only my third wheel set build and I'm pretty sure I did that in past builds but regardless did it this time, counting turns. It gave me some sporadic tensions but the wheel looked reasonable for a starting point, I doubt the rim has any give to it so that may amplify the tension differences. Just to see what would happen I started going only by numbers, trying to smooth out the tensions. FWIW this is the front wheel with asymetric carbon rims that feels stiff AF. I wanted to get things semi in order before tensionsioning more. The radial true isn't horrible at ~0.6mm. Lateral true is trash at probably 1.5mm but that I will address later. Spoke tension deviation is 11% on the right and 18% on the left. not good, but at least it's not erratic. I thought that was under control enough to start approaching final tension.

I know this isn't how you build wheels but I'd still like to hear your opinion. Thanks!

awac

Try https://www.islandix.com/radar/editor

Then look at Islandix system. Ciao

79pmooney

East solution - build our wheels with bladed spokes. Then your eyes can see the spoke twist. (Might drive you nuts and it does both take longer and require two tool, the spoke wrench and another to hold the spoke from twisting.

Or - build the wheel. Ride it a hundred miles or so. Re-true, making it a point to turn past the (say) quarter turn you need, then back to unwind the spoke. Lots of ways to get correctly tensioned spokes without twist. Some put "flags" on their spokes so they can see it. I like the idea but flagging every spoke and removing them all sounds like a lit of work I don't have patience for.

79pmooney

I'd try to get the tensions more even now, not after more tensioning. Everything is easier with looser spokes. Also, you may be making the nipples of the tightest spokes quite old trying to turn them.

Edit: This is a reason I am such a fan of tensioning by ear. (Granted, I can hear pitch.) I tune pair of spokes to be equal. Go around the rims listening for ones that stand out. All easy and fast just hitting the spokes with the wrench. Sometimes the sound is ambiguous. Then I pluck the spoke with my finger. But even needing to both of those is a lot faster than putting the tension tool on.

FBinNY 

First of all. I've NEVER plotted spoke tensions, so have no basis to have an opinion.

I hate the entire notion of using tension as a basis during the build. (confirming tension on finished, or near finished wheels is perfectly reasonable).

IMO trying to track tension while building is like trying to drive with your wife and mother-in-law in the car.

Whatever you prefer, pick one priority and deal with that. That's not to say that you never want to do a reality check. As I'm finishing a wheel, I'll spin it and ping the spokes (good use of expired Visa card) listening for outliers and sometimes tweak a few.

My experience is that pinging spokes is much faster and comparably accurate to using a tension meter. But, as I keep saying, good shop practice is the key.
‐------------
Since you asked specifically, please don't be offended when I characterize this as a well documented, poorly built wheel.

Put the meter away, spin it pinging the spokes, find the worst outliers, and tweak the crossed pairs to better equalize the tension between them. Don't go nuts, just deal with the low hanging fruits.

Ryan_M

LOL nope, not offended at all. I appreciate you giving me your honest opinion. Before I move on with our discussion, can I ask if you're able to play an instrument?