PSA: Wrenching Skills Challenge Jan 15- March 1st

I really like this idea. Mostly because it drives me crazy to go to the LBS when my bike won't shift.

I found the downloads for the tri bike and mountain bike so maybe i'll get both and use my MTB as the guinea pig...

Ok, I lied, kinda. I do have the MTB book electronically but can't find the TT bike electronically yet. Maybe I'll start with the MTB and as I gain confidence I'll tri the TRI

Great!  Thanks Dave:)

I suggest this for anyone.  I honestly believe there almost no reasons to take a bike to your LBS.  They are very simple mechanical devices and just about anything can be fixed with some basic tools and some courage/knowhow.  In MOST cases, fixing a part is worthless, so learn how to swap parts out and making small adjustments can save TONS of money.  Also, you can always give it a try and if you don't get it?  Take it to the LBS anyway.  It's not like you can mess things up SO bad that you would cost yourself more money. (like doing a bad job on your own home electrical or plumbing)

Enjoy the experience.

Originally posted by switch

Originally posted by rrrunner

Ok, I lied, kinda. I do have the MTB book electronically but can't find the TT bike electronically yet. Maybe I'll start with the MTB and as I gain confidence I'll tri the TRI

You're a brave soul!  I am going to play with a bike I don't care about

Yeah.... this is the MTB.  The one that throws me at any given opportunity

x2  About the only things I would consider taking my bike to the LBS for would be for bottom bracket or headset work, and only because I don't (yet) have the proper tools.

I'm planning on doing pretty much a complete tear down and inspection of my bike over the holidays.

Mark

I'll put this out there:

* Have my torch skills honed enough to braze up my wife's 1x10 "all-road" bike frame. It'll be built on 24" wheels (507's, for those that speak ERTRTO), disc brakes, a fairly upright position, and loads of front-center and trail.

Dude, are you trying to intimidate me?

It's working :)

BTW, does this mean you're offering to field questions for the group?

You can ALWAYS ask. Doesn't mean you'll get an appropriate answer....

Strong work!

I used to love to tinker with stuff when I was a kid too. 

My husband and I just took apart our washing machine.  It was a front loader that had a horrific smell we couldn't get rid of, and it was making all of the clothes unwearable.  Ryan, moondawg14, totally had our back.  We got it apart, thoroughly cleaned it, put it back together, and voila!  No more smell, and it totally boosted our confidence. 

I like home projects and DIY building, but anything mechanical has made me nervous in the past.  It really was a thread in COJ with Ryan that made me think I just needed to get over it, and try fixing stuff, or (his suggestion) taking apart broken stuff.

My plan for the bike project is to try to build one from salvaged parts.  We'll see.  I bet, if nothing else, it will be entertaining :)

I may have something that may be interesting to this group.  I am working on a Wheel Truing Algorithm.  It may be ready by January for beta testing.  The idea is that the user measures the difference from round in a truing stand using dial indicators for radial and lateral displacement, measures the spoke tension using a meter of some sort (I like the iPhone Spoke Tension Meter app.),  and inputs the data into a computer.  The truing algorithm calculates the number of turns of each spoke to bring the wheel to true and equally tensioned.  The algorithm is based on a structural model the wheel that simultaneously solve bending equations for the the rim laterally and radial  and a model of stretching the spokes.  It is some very cool math and physics. 

I think this model will help beginning professional wheel builders and do-it-yourselfer get a feel for how much to turn a spoke to get the wheel truer each time rather that out in a different direction.  It lowers the skill level required to produce a really well-built wheel. 

The model works and I have tried it on one wheel.  The first sample was a wheel that was bent in an accident so it was not a great candidate.  The algorithm told me that the tension in the spokes would be too high to get the wheel true.  This was exactly what happened.  I need to set up to do some more wheels.

Here are some pictures of my setup.

The top picture is a cardboard protractor that I slip over the spoke with a pointer attached to the spoke wrench.  I also clip a paper clip to the spoke so I can see how much the spoke twists.  

The middle picture is the Spoke Tension Meter app.  It works by detecting the frequency of the plucked spoke and converting the frequency to tension.  It works pretty well.  By that I mean that the measurement is reproducible.  I don't have any way to calibrate against a standard.  Reproducible is probably most important for building wheels.  It reads about 10% higher consistently than a Park Tension Meter.   

The bottom picture is my truing stand with digital dial indictors replacing the Park mechanical dial indictors.  I can read down to .01 mm.  Having the digital readings rather than a big dial and one or two small dials to combine is much easier.

I have a very lengthy paper on the mathematical method for the truing algorithm for anyone who is interested.  70 pages mostly equations.

The computer program currently runs under a freeware program called Scilab that is very similar to Matlab.  It is only 3 pages.

TW

(Spoke protractor.jpg)

(Spoke tension meter.jpg)

(Dial indicators and truing stand.jpg)

Funny you mention all that and one of the few things I have done myself is re-cable my bike.  Shifter cables that is, not the brakes.  Maybe the brakes will be my project.

That's impressive and ambitious.  It's also one thing I have not tried and just buy my wheels built for me.

If I ever got into the fixie or single speed for recreation, I would try it just for the ability to come up with some really cool lacing patterns.

The algorithm is basically done. I have run a lot of numerical tests that all work. Now, I am just in the first phase of experimental testing the algorithm on real wheels.  The hardest part is measuring the amount I turn the spoke nipple into the thread as opposed to twisting the spoke with the spoke nipple fixed on the thread.   My paper clip on the spoke and pointer on the spoke wrench technique works but is easy to flub up and mess up the measurement.

I have done a lot of reading on the modeling subject.  I think my model is something new because it is analytical (not a finite element solution) and a nice addition to the engineering mechanics.  I have been working on applying the model to buckling limits for spoke tension and max spoke tension for various road loads.  These would be useful calculations to use the model for wheel design.  t

The method treats the rim as a circular beam with point loads representing each spoke.  The rim bending is uses Euler-Bernoulli assumptions applied to the circular beam in the lateral and radial directions of bending.  The most complicated thing is the set of formulas for the geometry of the spokes.  The are a lot of spoke patterns to represent even if I limit it to wheels I own.  

The data are pretty simple to get.  Right now the only fuzzy data parameter in the model is the bending stiffness coefficient.  I don't have a good way of estimating the second moment of area for the rim cross sectional area.  I hope I can get some help from wheel manufacturers or from academics who have the money to cut up some rims and measure their cross-sectional areas.   It has been a fun project.   

With my current bike that I ride I started with a Quintana Roo frame and built up from there.  I did all work except for running the cables.    Since then I have swapped handlebars and that required me to change out the brake and shifter cable housings, along with the cables.    I have also built my current set of wheels.   Laced the spokes to the hub and rim and trued them up myself.   I built a jig to get tight tolerances.    

Have wrench, can do.    

It has to do with that improvise, adapt, overcome attitude that was instilled in me long ago.

Good Golly woman, are you trying to poke the bear?!? Your timing on this is perfect, as I am nearly done with the tear down on what will be a SS/Fixie with a flip-flop hub. My tool collection is slowly building and a stand is on the list for soon. I can't see the pic, but I have the Big, Blue Book from Park as my guide and I've gotten a lot out of it already.