Dynamo wheel re-build

[honesty]

Ok this is a really stupid question, and I'm sure I know the answer, but....

If I were to re-build my current front wheel with a dynamo hub would I need to get new, different length, spokes? Current hub is a Shimano Ultegra one.

[jags]

yes  the flnge will be bigger on the new hub so shorter spokes needed. often wondered would it be possible to cut the spokes and rethread them

[JimK]

here is a fun site for figuring lengths:

http://www.nabendynamo.de/service/speichenrechner_en.html

[Danneaux]

...often wondered would it be possible to cut the spokes and rethread them

Yes to rethreading, no to re-using them.

Jags, Phil Wood make a wonderful spoke-threading and cutting machine, as do Morizumi. Hozan make a less expensive one that really just threads. I've used them and owned one. Mine worked by roller-forming new threads, rather than cutting them with as die as you might use to make bolt threads. These things work a treat -- the Morizumis make even better threads than OEM -- but unless you have real need for one (and the volume to justify purchase) they're a costly solution compared to buying new spokes infrequently. You can see what they look like here:
http://www.philwood.com/products/tools/spokemach.php
http://www.youtube.com/watch?v=TI3OCyazcYM
http://www.mpgear.com/item/TL2425/Hozan-C-700-Spoke-Threader-14-and-15-Gauge/1.html?utm_source=googlebase&utm_medium=CSE&kw=%7Bkeyword%7D&utm_term=Hozan+C-700+Spoke+Threader%3A+14+and+15+Gauge&utm_campaign=balanced

For those wishing to get more into the science and esoteric nature of whelbuilding, see Ric Hjertberg's "Wheel Fanatyk" site, here: http://wheelfanatyk.blogspot.com/ If you're hankering after a Morizumi cutter/threader, Ric has slashed USD$300 from the usual price, making them a relative bargain at USD$2900 for the basic unit. He also has the stuff to setup a "proper" threading/cutting workstation. The stuff Danneaux Dreams are made of....

Ric has been a good source for Ghisallo medallions, too!

Best,

Dan.