Custom half-shaft sleeve with diameter mismatch?

[nubster]

I mocked up a pair of custom half-shafts for a 2001 Honda Civic with a Tesla Front SDU by splicing some cheapo Model S axles with the stock Honda axles of a smaller diameter. I test-fit everything with the SDU installed, and everything fits well, and there is no binding with the suspension. Ultimately, I'll get some legit ones made.

In the meantime, I would like to sleeve these mock-ups to test-drive the car around the neighborhood, etc. However, I'm unsure how to address the diameter change mid-way down the axle. Should I "shim" the smaller axle with another tube to bring it to the same diameter as the Tesla axle before installing the sleeve, or is that overkill? Can I simply leave a 2mm gap between the sleeve and the Honda axle as long as I weld it up well?



I plan to cut four slots down each end of the sleeve tube, scoring into the axle and welding them in as best as possible. In the pic below the red shows how I was planning to cut and weld the sleeve on.



Here's a link to more pics for more context: https://photos.app.goo.gl/FxQuzYbDE9JYPF5v5

Again, these will be used with a Tesla Front SDU, and I want to ensure I can drive around city streets for testing etc., before getting legit ones made.

[jrbe]

A spacer sleeve to center them would be ideal. It's really hard to weld something like this concentric. Even with the spacer sleeve it won't be perfect.
If you have access to a lathe you could spin up a sleeve. Or search McMaster for sleeves but measure things accurately first. Ideally there would be overlap of the axles and a sleeve inside and outside to help keep it straight and maybe together if the weld let's go.

[arber333]

I mocked up a pair of custom half-shafts for a 2001 Honda Civic with a Tesla Front SDU by splicing some cheapo Model S axles with the stock Honda axles of a smaller diameter. I test-fit everything with the SDU installed, and everything fits well, and there is no binding with the suspension. Ultimately, I'll get some legit ones made.
....
I plan to cut four slots down each end of the sleeve tube, scoring into the axle and welding them in as best as possible. In the pic below the red shows how I was planning to cut and weld the sleeve on.
....

I would advise you to get a custom sleeve made to with one side turned to Tesla dimension and another side turned down to Honda dimension.
Then you make a 8mm or so hole on one end of tube and 25mm further down another hole rotated 90 deg to the plane to better distribute torque spikes. Theory behind this says 90deg welds distribute torque spikes around whole circumference of the shaft on some length which should soften the immediate spike at the point of the weld. On the other side from centerline you mirror the holes. Those holes are rosette welded to the shaft inside so material should be centered. I would suggest to make very tight assembly to have least possibility of mass offset.
The idea is to use correct material which is meant for quenching e.g. 25CrMo4 or C45 steel.
Then when everything is done and joint shafts are welded you would want to anneal to release tensions in material structure after welding.

[P.S.Mangelsdorf]

If these are temporary, the gap could be ok if welded heavily, but I would recommend them being very temporary or having a friend you can call when the welds break a couple miles from home (just speaking from experience).

Unless you are a very, very skilled welder, you should also expect some vibration from imbalances in the welded axle.

[nubster]

A spacer sleeve to center them would be ideal. It's really hard to weld something like this concentric. Even with the spacer sleeve it won't be perfect...

To clarify, the axle halves are already welded together. I'm just trying to add a sleeve to them now.

I would advise you to get a custom sleeve made to with one side turned to Tesla dimension and another side turned down to Honda dimension.
Then you make a 8mm or so hole on one end of tube and 25mm further down another hole rotated 90 deg to the plane to better distribute torque spikes.

If I understand correctly, like this (below)? Is it better to mirror or offset 90 degrees across the center line (purple vs red)?



Getting custom-made sleeves and annealing, etc., sounds more like a permanent/long-term (i.e. expensive) solution, but let me know if that's not the case. I'm just looking for a temporary, cost-effective solution that will be "good enough" to move on to the wiring and integration phase. Once everything is together and I can drive around the block, I'll have legit shafts made. At least, that's how I'm thinking about it.

As opposed to getting custom-made sleeves, I was thinking I could get another tube to act as a bushing/shim for the Honda side and weld it in along with the outer sleeve in the same fashion to fill the 2mm gap. I just wasn't sure if I was overthinking it and the gap won't really matter for my use case.

I appreciate all the input, thanks!

[snelly]

Just fill the 2mm gap.
if you still have leftover tube, just slot it to pinch down to fit inside gap.

[arber333]

To clarify, the axle halves are already welded together. I'm just trying to add a sleeve to them now.
.....

Getting custom-made sleeves and annealing, etc., sounds more like a permanent/long-term (i.e. expensive) solution, but let me know if that's not the case. I'm just looking for a temporary, cost-effective solution that will be "good enough" to move on to the wiring and integration phase. Once everything is together and I can drive around the block, I'll have legit shafts made. At least, that's how I'm thinking about it.

As opposed to getting custom-made sleeves, I was thinking I could get another tube to act as a bushing/shim for the Honda side and weld it in along with the outer sleeve in the same fashion to fill the 2mm gap. I just wasn't sure if I was overthinking it and the gap won't really matter for my use case.

I appreciate all the input, thanks!

Actually that is just what i was telling. When you weld rosette holes at 90deg material under there behaves as one homogenous piece and torque spikes at the seams are lower... that is the theory.

You can simply make a tight fit for both shafts in a lathe. You buy the sleeve to ID of your lower shaft. Then you turn one end on a lathe to accept both side IDs.
You still need to weld that tube at the ends though...

Well the point of annealing is to relieve the weld beads off stress at shaft to shaft welds. But i think since you will use the sleeve you should be good.