SparkPlug

Having become an expert at building wheels... OK, I've done a couple and got to cheat by measuring the length of the original spokes to get the replacements then making use of Sheldon,

Wheelbuilding

I have foolishly decided to write a Spoke Length Calculator on the basis that I do not have a basic clue and I have just bought a pair of Exal XR2 rims and have a spare, front/rear, pair of Maillard hubs. All I need to do is 'lace them up'.

Of course there are 'loads' of tools available on the Intertubes but I thought I would break my head harder and write a stand alone program to do the job. I will be using FreePascal/Lazarus,

Lazarus Homepage

Initially under Linux but Lazarus is 'cross-platform' and I have an old copy of XP running under VirtualBox so I can hopefully port it to Windows. In any event I will be providing the source code so you can compile for yourselves. It will be FOSS... with disclaimers but you get to look at the source, spot my bloopers and make your own modifications.

I'll need a bit of help in respect of the interface and, perhaps, some of the maths.. but certainly the interface although I might have some 'fixed' ideas about that.

Any Interest...? Shout at me.

mconlonx

Spoke Length Calculator

FBinNY 

No pun intended, but you should know the warnings about reinventing the wheel. Same goes here. There are dozens of free on-line spoke calculators available, so one more isn't going to change anything.

Based on your own words about needing help with both the interface and math involved, I wonder why you even want to bother. However the math is straight forward, and involves a number of triangles and sine functions. For example, you'd use the number of holes and crosses to calculate the angle to the hole, and the sine and flange diameter to calculate how much closer to the rim that hole is. Likewise for the CTF, and other corrections.

SparkPlug

Thanks, Indeed but... as suggested there are loads of these things all over the Intertubes but, apart from a 'method' and in particular how to make measurements, it's not very insightful in respect of the underlying reasoning.

Simplistically let's say I go three cross on a 36 spoke rim/hub. That's 18 spokes per side so I would guess that the hub gets rotated 'back' 20 degrees per spoke or 60 degrees total and that 'guess' let's me do some algebra in order to come up with the required length of the spokes.

Of course that 'wet finger' might be a bit lame. The other 'wet finger' suggests the permutations and combinations are going to be kind of infinite. Perhaps 'experience' gives 'sweet spots' but it strikes me that there is a great deal of opportunity for experimentation.

Willbird

Having looked at the existing ones the nice feature to them is they already have many hubs and rims pre loaded. You will lose that. What would be really useful maybe is a universal database that spoke calculators could all reference :-). Just an idea :-), build it and maybe they will come :-).

SparkPlug

WARNING, I'm from New York. Thin skinned people should maintain safe distance.

Noted, and I cannot claim to be a Yorkshire Man... Otherwise I might wish to 'bother' because there is the remote possibility that I will come up with something that, at least to myself and hopefully others, 'makes sense' rather than being some sort of 'simples.. triangles and sine functions'. delivered over the net using Java Script with no real underlying rhyme or reason.

... This is not an argument I wish to have with you.

Thanks

SparkPlug

We can do that... Or rather there is the opportunity to provide that functionality. It just needs the 'users' to put their data in and share it. Simple case would be.. excuse me whilst I get the declarations wrong

type

HubValues = Record
Name: String;
Val01: String;
Val02: String;
-
-
end;

RimValues = Record
Name: String;
Val01: String;
Val02: String;
-
-
end;

Which would let me/you write these Records to a file once the values have been inserted for later import and use. Of course someone else has to do the hard work in the first place.

I would fight shy of a 'universal database', the concept of records is cross language, but...

https://wiki.freepascal.org/Lazarus_Database_Overview

.. it can be done apart from the fact you have to get into installing something like MySQL and that might break people's heads.

Bill Kapaun

They are always coming up with new wheels, but in the end, they all do the same thing. Roll.
Spoke calculators in general tend to give slightly different results from each other, due to the various "fudge factors" built in.
Most of us typically pick one calculator, learn its nuances, and stick with it.
I think the only users you would get would be new wheel builders, that happened to try yours first, out of the various free choices available.

SparkPlug

"learn its nuances"

Appreciated.. along with the "fudge factors". It might be nice to know what they are and why they exist and also have the opportunity to fudge things for yourself. That can be done.

Prototype.



As I suggest this will be a FOSS program delivered with source code. You will be able, hopefully, to install it on your own computer and fiddle to your hearts content.

Of course I might end up being a bucket of fail but as Willbird suggests. "If You Build It, They Will Come." Just looking for some suggestions about what size of 2 by 4 might be needed.

FBinNY 

OK, I know when my suggestions aren't wanted, but have to wonder.

You have limited wheel building experience, so probably don't know the small considerations that affect final spoke length.
By your own admission you need help with the interface and the math involved.

By process of elimination, I gather (hope) that you know how to write code, but what else do you bring to the table? You've rejected my explanation that the math is basically a number of Trig calculations, which somehow offended you, so I guess you have an alternate approach.

But as I said, I know when I'm not wanted, so I wish you good luck with the venture.

AnkleWork

Hey, you're getting smarter!
Feature request: Please build in a temperature converter, a mm to inch converter, and a four function calculator, because there certainly aren't enough of those around -- oh, and a spell checker.

AnkleWork

That's a great approach. For sure, nobody else ever had the deep insight that spoke length depends on hub rotation (haw!).

AnkleWork

The truth gets more dilute every day; no reason you shouldn't push that process along.

SparkPlug

Sorry. Do not get the impression that you have 'pissed me off' by saying MEH... which seems to be your natural reaction to others not skilled in 'the art'.

After all you are FBinNY and have an immense wealth of experience but apparently I am not going to tap into it because, according to you, 'It's Just Trig' and that should be end of story. Thanks for explaining the Trig.... and the fudge factors.

As to whose table we are sitting at then you might assume I am 'almost' capable of doing this for myself but with a bit of help I might be able to add the bells and whistles as requested or suggested by others. Of course if you do not wish to offer some scraps from your table feel free to apparently 'not be wanted'.

I really did not expect much more from you and it would seem I am correct.

Don't let that prevent you from chipping in.



The Palette is still basically blank.

SparkPlug

OK Clever Dude. Thanks for the contribution.

What if I wanted to break the house rules, whatever they might be, and rotate the hub 50 degrees or 40 degrees.. I'll take a guess that going over 90 degrees might be a problem but given you know the house rules perhaps you might wish to explain them to 'us' lesser mortals... No?

I might guess FBinNY could take a stab at that one.

You? Not so much.

AnkleWork

What "house rules?" Please quote or provide a link.

Clue: you should probably pick a different reference frame.

mconlonx

Can't help with the interface, but the math is google-able.

Perhaps the maths in this paper would be helpful?
https://people.duke.edu/~hpgavin/pape...heel-Paper.pdf

More maths here:
Measurements for Bicycle Spoke-Length Calculations

And here:
https://www.wheelpro.co.uk/support/sp...gth-proof2.pdf

Another one:
Pijin - Spoke Calculator
Ok, here's the formula we use to calculate the spoke length. That trigonometry I learnt at school wasn't so useless afterall! I'm not going to go through the proof of this formula... I'm sure you can search for it on Google if you're really mathematically inclined.

l is the spoke length
rr is the radius of the rim
rf is the radius of the hub flange (measured to the centre of the spoke hole)
f is the offset of the flange from the centre of the wheel
x is the number of times a spoke crosses over another spoke
h is the total number of spokes in the wheel
dh is the diameter of the spoke hole in the hub

I guess there is a slight inaccuracy in the formula in that it assumes the actual diameter of the spokes to be infinitely thin. This will give spoke lengths which are a fraction of a millimetre too short. However, this is balanced out in the real world because the holes in the hub stretch when the spokes bed in, so these 2 factors pretty much cancel each other out...

SparkPlug

Oh Great.. Bwah-Haw. I assumed you knew them but obviously not.

FBinNY 

I read your post No.4 quoting my reference to thin skin, and the general tone to imply that you weren't interested in my help. I did try to point you in the right direction with my references to triangles and Trig --- because that's the required and relevant math --- but even before that, it was as far as I was going because it's your project, and not of interest to me.

As for the reference to my saying "Meh" as a natural reaction to folks who aren't insiders or experts, I think the body of my thousands of posts trying to help people with all sorts of levels of expertise proves the opposite. Of course, I do select what to get involved, and retain that as my option, exercised by simply not posting.

My original and I feel best advice holds. I consider the entire project as described to be a duplication of what's already been done, and a waste of time and effort. Of course it's your time and effort to waste, so not my issue.

You were tight that you weren't going to tap into my knowledge base, not because of what you said, but because your project isn't one I was interested in to begin with.

I'll leave you with one last bit of help on this --- my last --- post here. The most common actual formula for calculating spoke length based on the major variables -- ERD, flange dia, CTF, no. of spokes and crosses has been published a number of times and a bit of research should find it, if you don't want to generate it yourself. There are probably some variations, but the overall math involved is the same.

Best wishes

Edit -- I see that a good soul did the research on your behalf and found a formula for you to work with.

SparkPlug

Thanks and appreciated. I'll have to code some other rubbish as a guess at a starting point and then work through my idiocracy before I get a handle on things.

SOCATOAH!

AnkleWork

Now I understand that you didn't understand anything you wrote about, but I can help. When you referred to "house rules" you were actually groping for the physical properties of the Universe.

AnkleWork

May I suggest a different approach? Rather than poke a few random characters into a smarter* phone and hope the Chatty Cathys will solve your problem, perhaps you might study physics, mathematics, and material science so you can understand the problem from first principles. HTH

mconlonx

Wow. I'm not sure I've ever been called a "good soul."

I do find it funny that a Liberal Arts grad with a BA in English was able to help out some techie with teh maths via a computer...

SparkPlug

Thanks. I guess I will be re-generating it, or something different myself.

FBinNY 

Certainly "good soul" describes someone who goes out of his way to do research that the OP could have done. And it makes perfect sense for a liberal arts grad, since it's about library research (net library) rather than math or engineering. In many ways, one of the key skills for good engineers is library research to find out how people who came before handled a problem. Often they find that the entire issue has been dealt with already and they need only follow the footsteps.