replacing stearing stems (why bother ?)

[yamaha_george]

hi,
I have been watching a long discussion on another specialist chassis list about using a new triple tree in an another frame.
This is the best answer so far from one of the worlds leading frame designers (he is now a consultant to amongst others Segway )
QUOTE:-
Back when I had a business making chassis, we often had to adapt different
fork yokes and we also made our own magnesium yokes.  In all cases I did
away with a stem altogether and just fitted stubs into each yoke.  Tension on
the bearings was provided by a  rod threaded at each end, locked into the
lower yoke and which passed through a hole in the upper yoke fitted with a bushing where it was
tightened with a nyloc nut.  The rods where either 10 or 8 mm dia. depending
on size of bike.  This simple and easy to make solution worked well and
saved some weight.

The added stiffness of a complete stem is quite minor when compared to the
alignment stiffness of the yokes clamped onto the fork tubes.

This subject has come up on the list before.  The late Hoyt didn't like the
idea but it worked fine in practice which is what engineering is about.

Regards

Tony Foale
info@tonyfoale.com
http://www.tonyfoale.com

UNQUOTE.

Since fitting different forks often appears here I thought this may prove very useful to some of you, afterall as Tony quite rightly says it is the bearings taking the load and it is they that must be set right & torqued down properly.

Such a neat solution in its simplicity !


For the scientists:-
http://thcentral.com/freesoftware/index.htm a computational fluid dynamics program

But -first look at this  http://www.youtube.com/watch?v=P8VcZzgdfSc to see what yer fat a8s does at 100mph to slow you down LoL

web page is  http://slfcfd.sourceforge.net/
#####
http://www.cfd-online.com/Wiki/Main_Page   this looks pretty good

http://www.boatdesign.net/Directory/Sof ... imulation/
 for boats, but maybe helpful for fairing analysis ?
Have fun
Geo

[cad600]

That is a very simple method to make swapping forks work. I haven't had time to look at the other links, but I had a question or two from reading that. Do you know if the threaded rod (which basically becomes your steering stem) is tappered like a stock stem is? It seams that if it was not then there would be fitting issues with either bearings or the top clamp. Still though, this might be a lot easier than other typical solutions.

[yamaha_george]

That is a very simple method to make swapping forks work. I haven't had time to look at the other links, but I had a question or two from reading that. Do you know if the threaded rod (which basically becomes your steering stem) is tappered like a stock stem is? It seams that if it was not then there would be fitting issues with either bearings or the top clamp. Still though, this might be a lot easier than other typical solutions.

The threaded rod he says go thro stubs (infills for the bearing inner diameter ) Ithink there may be apicture on his site if the grey stuff has got it right ?

[YAM93]

Hey George- I noticed this thread is very relevant to the front-end swap thread posted a little while ago, but for all the tea in China I can't find where he says this stuff on his website. Of course there are a lot of unrelated articles also. Do you know if this is from his BOOK ? ...or on the website... ??? and if so, which article ??

[yamaha_george]

Hey George- I noticed this thread is very relevant to the front-end swap thread posted a little while ago, but for all the tea in China I can't find where he says this stuff on his website. Of course there are a lot of unrelated articles also. Do you know if this is from his BOOK ? ...or on the website... ??? and if so, which article ??

YAM93,
sorry none of the above it is from the chassis design list that he and I subscribe to.
As you can imagine if you design frames you need to know what forks fit etc,. His way you can just anything you fancy JUST get the lock stops right :-}

Since I know for a fact it is NOT in any of his three books & I have never come across it on his web site I wrote him today in anticipation for back up pictures etc.
If and when he gets back to me (he is working in the US these days, you lot will be the first to know AFTER me LOL

[megaloxana]

Interesting..This could possibly open up a flood gate of front end swaps.

[yamaha_george]

hi,
Tony Foale put this picture up a steering head he is using this week end at Willow springs



You can see quite clearly the threaded rod steering stem :-}