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294mm or 296mm spokes for 36h Open Pros w/ Campagnolo Record Hubs- 3 Cross

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294mm or 296mm spokes for 36h Open Pros w/ Campagnolo Record Hubs- 3 Cross

Old 10-10-13, 09:39 PM
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avhed
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294mm or 296mm spokes for 36h Open Pros w/ Campagnolo Record Hubs- 3 Cross

The hubs are the 1970s version with the oil hole. Front hub specifcations: 70 mm flange to flange. Spoke holes are 38.5 mm apart . Rim ERD is 603-605?
Using the spoke calculators I come up with 296mm on some sites and 294mm on others.

Last edited by avhed; 10-16-13 at 09:19 PM.
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Old 10-10-13, 09:46 PM
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Are those calculators just rounding to the nearest 2mm? If so, that's stupid, and you should find a different calculator. This one has never failed me (although it doesn't seem to be loading right now???) http://leonard.io/edd/

Mr. Rabbit (forum member here) has a very extensive Excel spreadsheet that is also good, but I find the Edd calculator simpler to use.

Bottom line, measure the ERD yourself so you know it's right!
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Old 10-10-13, 11:16 PM
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Welcome to the GIGO world of spoke calculators.

Spoke calculation is a straghtforward formula, and just about every calculator uses the same basic formula, and will have the spoke end near the ERD entered.

But there are subtle variations which some calculators may handle differently

Flange diameter -- most are measured on centers, but the spoke is measured from inside the elbow, so there's a 1mm error for a2mm spoke (plus a bit for the oversize spoke hole)

effect of flange thickness, angle, and interlacing -- the spokes don't go straight from hub to rim, but take a longer route because of the over/under lace at the last cross. That effectively shortens the spoke somewhat.

Shape of nipple -- Some have button shapped heads, while others have conical heads which may settle a bit deeper into the rim hole.

and finally ERD -- here in the USA most folks take the ERD as being the desired height of the spoke in the nipple head. But old timers and many European companies publish specs based on the actual diameter of the rim where the nipple sits (some also forget to adjust the published spec for eyeleted and non-eyeleted rims of the same extrusion), so someone (you?) have to add that to the end result (my preferred method) or double it and add it to the ERD.

Lastly there's an honest difference in opinion about spoke height and which way to err. If building double wall rims with spoke/nipple that allow the spoke to beyond the top of the head by 2mm or so, I prefer to aim close to the top of the nipple (err high). But many spokes and nipples run out of thread just as you reach the top of the head, and therefore need to be erred low.

So you can see that how they handle these small adjustments can change the results for various calculators. A problem made worse by the inconsistency of published specs.

Calculators are very consistent, which is why I suggest always using the same calculator, and confirming the measurements yourself. Once you know how the calculator is biased, you'll know which way to round, and how much to add or subtract to the results for wheels to end up as you want them.
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Old 10-11-13, 05:53 AM
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If you have to pick, go with the slightly longer. It's is hard to add length to spokes if you find they are a little bit short.
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Old 10-11-13, 06:38 AM
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Originally Posted by Homebrew01 View Post
If you have to pick, go with the slightly longer. It's is hard to add length to spokes if you find they are a little bit short.
I also generally go longer. But if the OP is using spokes and nipples that run out of thread and don't allow the spokes to extend above the nipple he has little upside room, and needs to be careful not to go long.
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Old 10-16-13, 09:21 PM
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Originally Posted by FastJake View Post
Are those calculators just rounding to the nearest 2mm? If so, that's stupid, and you should find a different calculator. This one has never failed me (although it doesn't seem to be loading right now???) http://leonard.io/edd/

Mr. Rabbit (forum member here) has a very extensive Excel spreadsheet that is also good, but I find the Edd calculator simpler to use.

Bottom line, measure the ERD yourself so you know it's right!
The calculator above is one I did not try. I put in the mesurements and click on the blue boxes and nothing happens.
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Old 10-16-13, 09:27 PM
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Originally Posted by avhed View Post
The calculator above is one I did not try. I put in the mesurements and click on the blue boxes and nothing happens.
You ever hear the expression about how someone who wears two watches never knows what time it is?

Likewise if you use multiple spoke calculators. Pick a calculator - ANY calculator. Enter your data, an build a wheel using the spokes it comes up with, rounded to the nearest size. Remember which way you rounded, and note where the spokes end up on the nipples. If they're not spot on where you want, add/subtract the difference to all future results from the same calculator.

BTW- if you're building a pair of wheels, build the front first. Front wheels are more forgiving of spoke length error.
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Old 10-17-13, 09:07 PM
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Originally Posted by FBinNY View Post
You ever hear the expression about how someone who wears two watches never knows what time it is?

Likewise if you use multiple spoke calculators. Pick a calculator - ANY calculator. Enter your data, an build a wheel using the spokes it comes up with, rounded to the nearest size. Remember which way you rounded, and note where the spokes end up on the nipples. If they're not spot on where you want, add/subtract the difference to all future results from the same calculator.

BTW- if you're building a pair of wheels, build the front first. Front wheels are more forgiving of spoke length error.
I have more than one watch, but I am only wearing one at a time.
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Old 10-17-13, 11:00 PM
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Originally Posted by avhed View Post
The hubs are the 1970s version with the oil hole. Front hub specifcations: 70 mm flange to flange. Spoke holes are 38.5 mm apart . Rim ERD is 603-605?
Using the spoke calculators I come up with 296mm on some sites and 294mm on others.
You run the risk of running out of threads using restrictive nipples if you go in blind trusting 603 / 604 / 605 as the ERD for the Mavic Open Pro.

If you view my spreadsheet: http://www.mrrabbit.net/wheelsbyflemingapplications.php

The "rimchart" tab shows multiple entries for the Open Pro and the trend as of late has been closer to 601mm / 602mm.

As we always say here - it's better to measure your own ERD.

=8-)
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2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
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Old 10-23-13, 06:27 PM
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Measuring I get 596 inside the rim. One nipple has 5mm inside the rim, making my ERD 606.
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Old 10-23-13, 06:43 PM
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Here are notes I kept from building my first wheelset, using Open Pros and Record hubs. These were Record Titanium hubs from the late 1990s, not sure they are the same dimensions as your Records. But it might help w/ the thought process. 36 H and 3 cross. I forget the spoke make, I think DT Swiss, double butted. Brass nipples. I erred on the side of shorter, because I didn't want the nipple to bottom out. Turned out fine. Now I always get spokes 1-2 mm shorter.

"Wheel build

for Vitus 992 project

36 spoke 3 cross

Mavic Open Pro
ERD 601

Campagnolo Record Ti '97-'98

Rear
Flange diam 44
Center to flange 40, 13
Calculator says 291.6, 289.2
Chart says 291, 289
Adjust to 289.6 x 18, 287.2 x 18

Front
Flange diam 39
Center to flange 35
Calculator says 292.1
Chart says 292
Adjust to 290.1 x 36

Got 54 x 290 and 18 x 288"

Edit: reading the thread more carefully, it seems my front hub is the same dimension as yours. 39 mm flange (spoke hole ) diameter - not sure why I didn't measure 38.5 mm, maybe I'm just bad with a caliper - 35 mm center to flange. I can't recall if I measured the ERD, but actually I may have, because thus was done in a wheel building class and the bike shop had the measurement tools and the chart that you lay the rim on. Anyway I see that I used a significantly shorter spoke than you were mentioning. I also see that my habit of erring short is contra to what others do. Oh well. I think that you now know you can get away with a spoke as short as 290 mm so if you used, say, 292 mm then that should be pretty safe.

Last edited by jyl; 10-23-13 at 06:56 PM.
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Old 10-23-13, 06:50 PM
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Originally Posted by avhed View Post
Measuring I get 596 inside the rim. One nipple has 5mm inside the rim, making my ERD 606.
You're doing it wrong...

1. Test the nipple and actual thread combo you intend to use. Determine min insertion and max insertion. Decide where you want to aim leaving at least 1.0 to 1.5 mm of overhead. Most folks using 12 mm standard profile nipples will aim for screwdriver flat when using 9.5 mm threads on common boxed spokes.

http://www.youtube.com/watch?v=gCXFKN9JvCQ


2. Using a caliper, measuring rods and desired nipples set to preferred aiming point - measure the rim in 4 locations - take the average. That'll be your ERD (fingers crossed) that'll you'll plug into a spoke length calculator for the ERD or diameter input.

ERD is simply the distance from the end of one spoke to the end of the other spoke at 180 degrees in an already built and functional bicycle wheel. Problem is - you can't step into a time machine to measure your wheel in the future - you are using tools to estimate what it'll be in the present.

=8-)
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Disclaimer:

1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:

Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life
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Old 10-24-13, 04:22 PM
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I have used this one with good results. http://www.sheldonbrown.com/rinard/spocalc.htm
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Old 10-24-13, 04:43 PM
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Originally Posted by FBinNY View Post
I also generally go longer. But if the OP is using spokes and nipples that run out of thread and don't allow the spokes to extend above the nipple he has little upside room, and needs to be careful not to go long.
This is mainly about the spokes. If the spoke has (say) 9 mm of thread and it is thicker past the end of the thread than in the threaded part, it will not screw into the nipple beyond these 9 mm. Though I suppose there may be pathologically designed nipples that achieve the same effect. I have three different kinds of spokes here (one that I got online and two others from two unrelated wheels that I took apart) and all three are like that.
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