smart51
|
| posted on 10/9/06 at 03:54 PM |
|
|
how strong is M5 threaded rod
My gear shift cable has broken and I'm thinking of replacing it with a solid system. I have some M5 rod ends off the old cable.
If I connected them with a 800mm (ish) length of M5 threaded steel rod, would that be stong enough or would it buckle?
|
|
|
|
|
fesycresy
|
| posted on 10/9/06 at 03:56 PM |
|
|
I think that'll buckle.
I used M8 and then covered it with an ally tube so I get no deflection at all.
-----------------------------------------------------------------------------------------------------
The sooner you fall behind, the more time you'll have to catch up.
|
|
|
JoelP
|
| posted on 10/9/06 at 04:10 PM |
|
|
funny that, my rods broke and i considered swapping for cables! I was thinking there would be less play and hopefully less weight with cables.
I doubt m5 is up for it myself, though i asked recently about m6 istr and people thought it might last. Try it and see? Failing that, a really thin
tube, maybe 13mm by 20g, with threaded inserts and male roses would be good, and possibly lighter anyway.
|
|
|
RazMan
|
| posted on 10/9/06 at 04:21 PM |
|
|
Solid M8 worked for me - I put a thread on each end and used spherical bearings on each pivot. It's not the lightest way but it doesn't
flex 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
smart51
|
| posted on 10/9/06 at 04:33 PM |
|
|
I've just gone and looked in my basement and found some m6 rod of the right length. Holding it against the wall and giving it a good shove
makes it flex a bit. A few angry gear changes would probably bend it permenantly. M5 would be no good.
Joel, you think there'd be less play with cables? I'd have thought that good rod ends would be as tight as you could get? My old cable
had quite a bit of play. Perhaps that's because it had started to break though
|
|
|
JoelP
|
| posted on 10/9/06 at 05:56 PM |
|
|
i think its the chinese whispers really, building up the little wobbles into a bigger one. I have wobbles on the actually gear shaft on the engine,
and a little on both the shifter pivot and the pivot at the engine end, adds up to about 15mm of free play at the top of the shifter - pretty
annoying!
I sheared a 1/4 inch bolt, admittedly it had been welded and i was changing gears hard and fast, but i was suprised it went.
Threaded bars are a really easy option but its poor science, as a hollow tube is stronger weight for weight, and im sure the threads act as stress
raisers or similar.
If i had to make a replacement in pieces (i dont, as some nice chap is making it on a lathe!) i would prefer to solder or braze rather than weld it
up.
But you are right smart51, if every last thing was rose jointed it should be very solid, aside from the actual free play at the engine end.
meaning to ask, do you think cables are lighter? i had assumed so...
[Edited on 10/9/06 by JoelP]
|
|
|
smart51
|
| posted on 10/9/06 at 06:18 PM |
|
|
The cable that I have taken out is not heavy, it is certainly lighter than the M12 threaded rod that I used for mounting my engine. The M5 rod ends
on the cable are lighter than M8 rod ends on solid rods too, and you only need 2 of them.
The reason I asked was that I have some rod ends and for the cost of a bit of steel rod I could make up something for nothing. M5 probably
wouldn't be strong enough and with the cost of all the rod ends, I'll just buy a new cable. I've made up a new mount on the lever
so that the end that snapped is much more in line with the outer cable mount. It should last longer now.
|
|
|
givemethebighammer
|
| posted on 14/9/06 at 08:14 AM |
|
|
M5 is probably a bit too thin, but remember thread bar comes in mild and high tensile types like bolts. The stuff you buy at B&Q is mild steel. My
fastener supplier stocks the 8.8 stuff as well. The thinnest threaded bar I'd probably use would be M6.
|
|
|
smart51
|
| posted on 14/9/06 at 09:01 AM |
|
|
Even high tensile stuff won't be stiff enough in compression. In the end I just bought a new cable. Expensive but simple to install. The new
one is massivly better than the old, probably because I made sure everything was dead in line.
|
|
|
.jpg){kind=avatar}
