Steering Stem Modification

I'm building an 84 VF700F and am attempting to fit an F4i front end on it. Anyways, the 700F has a much longer steering stem but otherwise the dimensions are very close. I have already separated the F4i stem by grinding out the factory weld. So the big question is, am I crazy to use silicon bronze brazing to reattach the 700 stem? I am very adept at brazing.

 

After separation

 

I would not risk it, if you can't weld it find a competent welder to do it. You should also have about a 3/16" 30-45 degree bevel for serious penetration.

There's (up to) several tons of tension with proper bearing preload on that joint.

Even if there remains a decent press fit with the stem, it needs to be checked for distortion afterwards.

And yes, I do have a fabricating background, don't take chances here please

 

Didn't think about preload tension. I cut the f4i one off flush but was considering leaving the stick out on the vf stem. I had to cut the f4 one that way because I had no idea what the diameters and thicknesses were going to end up being.

 

Best bet for keeping everything square is to clamp upper and lower triple clamps to the forks, upside down so that you can have fork tubes standing up with the joint to be welded facing up.

Beveling the ID and OD is a must, and were it me I would TIG weld it, but MIG is acceptable if done by an experienced welder.

This area is no less critical than a bearing spindle on a car wheel, your life absolutely depends on it!

 

Been making these for my friends out of 1144 rod and silicon bronze filler. They are much stronger than the welded Motion Pro or cycle gear units.



Anyways, the factory welds were zero penetration welds, I just ground the bead off and pushed the stem out.

 

It's your neck (pun intended) ,do as you will.

Just want to be clear there will be severe consequences in the event of failure.

 

This is the 700 stem coming apart. Then did the heat and shrink into the new lower. I pressed it out backwards to save the seals from the 700 but the bearings are identical between the bikes.




Now I haven't brazed it yet but tommorow is decision time. I will also have to remove one steering stop and relocate the other.

 

Well, I did it. There is no way that braze is going to fail before something else does but I'm a little unhappy with the amount of heat soak into the opposite side. I would rather not see that band of gray between clamp and the blue.

 

Dija even think about the fork length differences and how much higher or lower the front end will sit ?

 

Thought about it, at least getting the 43mm tree gives me a lot more options for forks. The offset differences are huge so wheel to radiator clearance could be an issue. It was also one of the reasons I want to use conventional forks because the spacing between the clamps is less important.

 

Well I finished it, here it is with the steering stop. The brazing isn't as pretty because this alloy more fluid and harder to shape. I used it because it has high impact strength, it's the same alloy used to join carbide inserts in machine tooling. It also has a lower working temperature for less distortion.

 

It's hard coming onto a new forum because there is always a guy who speaks wisely but knows little. How exactly would you bevel the bottom of a lower clamp redwing750?

 

By post #6 I realized I was wasting my time yet again. Kind of pointless to ask after the fact no?

Will it work? Yeah it might.

May the luck of the Hot Glue Gods be with you.

 

I thought the stem base was tapered to stop it pulling through the T, can you confirm, or are they parallel ?

 

I often wonder why the world has so many unsolved problems when there seems to be an overwhelming proponderance of experts on the internet. :unsure:

 

Aluminum lowers have a flange at the base, these were straight.

 

It's like Knight and day.

 

Money & time, pure & simple. Plus most people are too dumb to want a nice world, they throw litter & generally live in squalor just because they can

 

Used some 1 1/4 pipe wrapped with 0.005" shim to simulate a 43mm fork. Everything fit pretty well, the ignition even bolts in and the steering locks work. I need to adjust the steering stop a bit because the legs hit the frame but it looks like I still get about 25 degrees on each side. Wheel clearance does not appear to be an issue yet.