So...
I'm swapping my Discovery 300Tdi's 3-bolt rear propshaft for a 4-bolt. However, on arrival, the balance weight on the 4-bolt prop looked like this:
Not great. Rust had got to it such that part of it was missing and the rest was flaky. I didn't want it coming away and causing a vibration that would trash my differential pinion seal and possibly bearings. If it needs it, I'll send it away for balancing, but I figured that I could probably achieve an acceptable level of out-of-balance simply by replacing what was there with good metal. So I marked and measured the old weight, and then prised and chiseled it away, catching it all in a plastic bag. No power tools - I didn't want to lose any of the rusty weight in the process.
Bag of rust, on scales:
I guestimated that that weight represented perhaps 90% of the original balance weight. Mild steel has a density of about 7800kg/m3. 1.5mm thick steel sheet delivered the required weight at close to the original 50mm x 40mm size of the old balance weight:
Then I needed a means of welding it to the shaft. I didn't want to add extra metal in the process, so I drilled some holes in it to plug weld through, before bending it to match the curvature of the shaft:
Then I welded it in and ground off any excess metal:
Finally it all got a coat of paint ready for fitting.
It won't be as well-balanced as a new shaft, but it should be as well-balanced as when it came into my possession, with the added benefit of being balanced with steel rather than rust and hence standing half a chance of holding together for a while without further deterioration.
I'm swapping my Discovery 300Tdi's 3-bolt rear propshaft for a 4-bolt. However, on arrival, the balance weight on the 4-bolt prop looked like this:
Not great. Rust had got to it such that part of it was missing and the rest was flaky. I didn't want it coming away and causing a vibration that would trash my differential pinion seal and possibly bearings. If it needs it, I'll send it away for balancing, but I figured that I could probably achieve an acceptable level of out-of-balance simply by replacing what was there with good metal. So I marked and measured the old weight, and then prised and chiseled it away, catching it all in a plastic bag. No power tools - I didn't want to lose any of the rusty weight in the process.
Bag of rust, on scales:
I guestimated that that weight represented perhaps 90% of the original balance weight. Mild steel has a density of about 7800kg/m3. 1.5mm thick steel sheet delivered the required weight at close to the original 50mm x 40mm size of the old balance weight:
Then I needed a means of welding it to the shaft. I didn't want to add extra metal in the process, so I drilled some holes in it to plug weld through, before bending it to match the curvature of the shaft:
Then I welded it in and ground off any excess metal:
Finally it all got a coat of paint ready for fitting.
It won't be as well-balanced as a new shaft, but it should be as well-balanced as when it came into my possession, with the added benefit of being balanced with steel rather than rust and hence standing half a chance of holding together for a while without further deterioration.
