TOPIC:

Hi all,

Has anyone ever removed the steering pin from the bottom yoke? I know it can be removed as it is not one piece, but I have no idea if it is screwed, pressed, welded or otherwise.

Please see the pics.

Is there a separate ring/washer between the pin and the yoke, or is the raised area where the bearing sits part of the yoke, just unpainted?



And why is the inside of the steering pin 'star-shaped'... (see pic taken from the top).



If no one knows I will have to destroy the yoke by cutting out the pin. I need the pin for the new suspension forks/yokes from the Benelli that are going on.... easier than changing the steering brace to accept a larger steering pin I reckon ....

Paul

Any yokes I've heard about where the shaft was removed from the yoke was a press fit. Because of the difference between aluminum and steel coefficient of linear expansion, if you were to put the yoke in an oven @ 350F (175C) and let it heat soak for an hour, you should be able to then put it on an arbor press and it should damned near fall out. Much like changing the liners in the cylinder, there have been reports of guys putting engine cylinder blocks in an oven standing up and then checking it an hour later and finding all the liners had raised up and out of the cylinder block and they didn't know why. "Coefficient of linear expansion" Aluminum will expand more than steel at the same rise in temperature. Use it to your advantage.
Coefficient of linear expansion for aluminum per deg C is 25 x 10^-6 = .000025
Coefficient of linear expansion for steel is 12 x 10^-6 = .000012
So let's say for argument sake that
the bore of the aluminum yoke is 1.248"
the bore of the steel shaft is 1.250" which would be an interference fit of .002" and
let's say that the yoke is at room temperature before heating @ 20 deg. C and we plan on putting it in an oven and raising the temp to 175 deg. C

The calc for the change in diameter of the aluminum yoke bore-coefficient of linear expansion of aluminum (.000025) x rise in temp (175C-20C) x diameter (1.248") = .0048". So the aluminum bore in the yoke would grow to 1.248"+.0048"=1.2528"

the calc for the change in diameter of steel shaft- coeffecient of linear expansion of steel (.000012) x rise in temp (175C-20C) x diameter (1.250") = .0023"
so the steel shaft would grow to 1.250"+ .0023" = 1.2523"
That means the aluminum bore would be larger than the steel shaft by 1.2528" -1.2523"= .0005" at 155 deg C

Thanks Kawboy, but I think both steering pin and yoke are both steel, judging by the weight difference between the old yoke and the new one, which definitely is aluminium. Also not sure if there is a separate ring between the yoke and the pin and if so, what that is made of....

The comment on KZriders was: grind off the bottom weld and press out from top to bottom. If I am going to do that I might as well make two cuts in the yoke to release the pin - thereby destroying the yoke, so that is a last resort.

When I get it out, I certainly will apply the heat/cold science to re-fit the pin into the new yoke. The pin from the new yoke also had a retaining ring halfway embedded in it, and the yoke hole had a slightly smaller diameter at the top, where the ring 'stopped' at the point where it narrowed. I may need to copy that system onto the old pin.

Paul

grind off the bottom weld and press out from top to bottom.

I have no experience with this, but just by looking, this was my take at this as well. Just as start, what after no idea.

I missed the top picture so agreed both are steel BUT I suspect the bearing shoulder on the shaft is a machine diameter of the shaft and you'll need to grind the weld out and press the shaft out of the yoke from the bottom. My thinking here is that the shoulder on the shaft located the shaft in the yoke and the strength of the "joint" would be by supporting the joint from both sides.
Jezzzz, all that math for nothing !! Oh well, it was a good exercise for me to work through (brought back some memories from my days in the nuke plant). Thanks for that !!

Oh dear, sorry about that!

Still, following your 'heat-size' thinking, if I heat up the outside of the yoke, that part should expands whilst the (still) cooler shaft should remain the same diameter, which SHOULD allow some wriggle-room.

I'm still not quite clear on what direction to push the pin out, upwards or downwards. My gut tells me downwards as the whole design should be to get stronger by pulling the pin upwards into the bottom yoke by tightening the bolt at the top of the pin on top op the top yoke.

But Kawboy seems to suggest the bearing shoulder is part of the steering pin (machined down if I read correctly), which means upwards will be the only way....

Maybe grinding the weld at the bottom and then heating the outside of the yoke up, and then trying to see if some gentle taps up as well as downwards reveal which way it wants to go... ?

Any more thoughts?

Paul