petekeys, this project is about realizing my vision, about creating the machine and executing my plan, and also of course about telling the story. Once I create something I really have little interest in doing it again for someone else, unless maybe if it allows me to be involved in some cool project or enterprise. I don't want to get into a discussion about it, but if someone wants to do such a service, all the photos, drawings, and documents from the project are my own and I am the sole copyright holder, but I release them to the public under the terms of the Fabricators Design License
. The spirit of the license is to allow anyone to use the material for whatever use they want as long as any modifications or improments to the original design are made available to the public at no cost.
As I mentioned in a previous post, the u-joint
of the shaft I extended was going bad so I intended to replace it. I measured the OE joint as 19x44. Here's the joint in the original shaft.
After some searching I found two after market u-joints I thought might work. One is a 19x44 and the other a 19x48. From the left; the 19x44, the 19x48, and the OE joints.
I was interested in the 19x44 because there's not much clearance between the transmission output flange yoke and the swingarm housing when the swingarm is in the bottomed-out position with my 280mm of wheel travel. I thought with this joint there may be enough room to add a circlip to the yoke to hold the joint in place, but when I got the part I found it to be of very poor quality, and I think intended for steering shaft applications. As seen in the photo the bearing inner shaft has a very small diameter and the needle bearings are much shorter then the OE joint.
Here's a comparison of the OE joint on the left and the 19x48 on the right. The OE joint has larger diameter bearing shafts and longer needle bearings than the replacement 19x48. I think the OE joint would have longer service life in the monolever's splash lube application, but the 19x48 should be sufficient for my application. I am still on the lookout for a better replacement, ideally something near identical to the OE joint.
The bigger 19x48 didn't quite fit into the yokes.
I used a die grinder to take a small amount of material off the yokes and the joint cross.
Here are the shaft parts ready for assembly. The photo shows where I ground two ribs off the joint cross to get the needed clearance for assembly. The replacement joint has a grease fitting
and shaft seals, but I didn't install these to allow the gear oil in the swingarm to get to the joint bearings.
The 1st step in assembly is to get the cross in the yokes.
Next is to install the caps. I used a brass hammer and some sockets to get caps in place. The photo shows how I used a socket large enough to pass the cap to support the yoke from below. Some light tapping was enough to get the caps positioned.
I used a depth micrometer to center the caps in the yoke such that there was no play in the joint bearings.
As mentioned, with my increased wheel travel there isn't much clearance between the transmission output flange yoke and the swingarm housing at the bottom-out limit, and with this bigger joint the options for fastening the joint were few. My 1st idea was to make a strap, maybe 5mm wide that would go across the cap and be spot welded to the yokes, but in the end I decided a simpler solution was just to spot weld the cap to the yoke.
I knew that it was somewhat common method, especially in off-road trucks, but wasn't sure if it would work here. To get a better feel for it I cut up a cap from an old joint with an abrasive cut-off tool to see the cross section.
I figured that if I did the welds with minimal penetration there was a lot of material there at the end to take the weld, and also, all the u-joints I've ever seen always wear out at the load bearing sides of the needle bearings, so if I put the weld somewhat perpendicular to that the effect of the weld would be minimized. I setup the welder with a low amperage and the DC pulser at around 5 Hz. I just put one weld at the thicker end of the yoke. I can try putting a second weld at the other side if I find trouble when I put it into use.
There wasn't much else to do other than weld the other caps on. Here's the finished shaft.
And the shaft installed on the bike. This shows the yoke clearance problem. When the shaft turns a few degrees from this position the corner of the yoke will almost touch the arm housing.
I have a spare joint, so when it comes time to replace this joint I'll just need to grind away the spot welds to get the caps out and put in the new joint.