What is drc ST19 effective rim diameter?

Sares · Post by **Sares** » 4 Apr 2007, 7:51pm

I have a spoke calculator, but it doesn't have this rim in it, and that's the one I bought. Can anyone tell me what the effective rim diameter is? Or, the spoke length for a cross-3 wheel with the DH-3N71 Shimano dynamo hub?

Many thanks!

Post by **Mick F** » 4 Apr 2007, 8:29pm

Hi, I built my own wheels. I read bit and pieces, and looked on the net finally setting on:
http://www.dtswiss.com/index.asp?fuseac ... popup=true
If you click on Accept the terms, then click on "user instructions" it tells you how to measure your rims and hubs.

Also try:
http://www.wheelpro.co.uk/spokecalc/
and input your dimensions as a check between the two sites.

Then follow Sheldon Brown on how to build a wheel:
http://sheldonbrown.com/wheelbuild.html

It works, I did it. I'd never built a wheel before!

andrew_s · Post by **andrew_s** » 4 Apr 2007, 10:57pm

To measure it:
Take two spokes cut down to 200mm (cut off the elbow side). Glue on a nipple so that the top of the spoke is flush with the bottom of the slot in the nipple.
Place in opposite holes in the rim and hold taut (do not apply so much force that the rim deflects). Measure between the ends and add 400mm. Average several diameters.

Doesn't help much if you haven't got the rims yet

CJ · Post by CJ » 5 Apr 2007, 11:07am

Here's my CTC Spoke Length Chart, which provides a simple graphical method for looking up spoke length that you can pin onto the workshop/garage/shed wall.

The ST19 measures 19mm deep. That's 5mm more than my "assumed" 14mm, so simply subtract 5mm from the length given by that chart. I've always found the result was near enough the same as I got from a computer after the abovementioned measuring and calculating palaver. So nowadays I just use the chart and one simple measurement.

PW · Post by PW » 14 Apr 2007, 6:52pm

Imeasured the *Radius* at 303mm for calculating longhand using Brandt's formula in the back of the bible. That worked out fine for every one I've ever built, so you can take the *Diameter* as 606mm.

hubgearfreak · Post by **hubgearfreak** » 15 Apr 2007, 6:17pm

put a nipple in a hole, and measure the distance between its head and the very outside of the rim. measure the very outside diameter and reduce it by double the first number.

i.e.
20mmx2=40mm
645mm-40mm=605mm

do it at different places accross the rim to make sure

stephen · Post by **stephen** » 16 Apr 2007, 12:01am

Yes, much easier than the normal method of measuring between two cut down spokes. Wish I'd thought of that. Now there's intelligence for you.

Stephen

hubgearfreak · Post by **hubgearfreak** » 16 Apr 2007, 3:29pm

stephen wrote:Yes, much easier than the normal method of measuring between two cut down spokes. Wish I'd thought of that. Now there's intelligence for you.

Stephen

intelligence maybe..but not mine. i had read it here
http://www.bikeschool.com/spokes/

just click on a ?

this is the best online one i've found

Sares · Post by **Sares** » 29 Apr 2007, 7:59pm

Thanks for all your help! Spokes arrived last week, and wheel is now in one piece! It actually is quite easy.

-Sares