Well, this is embarrassing.
I don't know how I overlooked this. I'm usually really fastidious about detail, but today when fitting up the rebuilt steering column into the re-bushed lower bracket, I noticed unacceptable/excessive wear on the steering shaft itself.
I immediately looked at buying and importing another one from the USofA (only 5:1 available) but its a cost prohibitive exercise, so I guess I'll look at repairing this one.
Can it be built up and then ground down?
Alternatively, any Aussies reading, can you come to my rescue with a good replacement?
Why not make and fit a bronze bushing?
I would not weld ad then bodge on the steering shaft. That is looking for crack problems. I think the steering shaft is the same 4/1 and 5/1 anyway, the only difference being the planet gears. The later assemblies have the extended "stop" pin.
Fitting a bushing in the lower bracket would seem straight forward to me. Bore it oversize and press it in. A good grade of bronze will make a long wearing part.
I restore early T columns and encounter the same thing 95% of the time. Yes, you can take the shaft to a reputable blacksmith or welding shop. They can chuck the shaft up in a lathe, build the shaft up with a MIG welder then turn it back down to 0.750 inch diameter. The problem with fitting a new bronze bushing to a worn shaft is that the end with the nut will almost always be larger than the worn section. I think you can imagine the problem with that, to get it over the end you would end up with a loose fit, right back where you started. I suppose you could turn the worn shaft down and then fit a bushing to that too. Mike
I would presume that yes, turn down the lower six inches of the shaft slightly smaller size, being careful not to leave a "step". Fair/blend it out so there is not crack forming line.
It can be done this way:
1. Find two steering gear shafts of about the same vintage. You want the steel in the two shafts to be the same.
2. Cut the end off the one you intend to use several inches above the point where the wear begins.
3. Cut a section out of the middle of the second shaft (donor), above the area where it is worn, but below the area near the top of the shaft and the steering gears are located. The length of this section should be a little longer than the end section you cut off the first steering gear shaft.
4. Both pieces should have the same diameter, about 3/4 inch.
5. Deeply "V" the end of the shaft you are trying save, as well as one end of the section cut from the middle of the second second (donor) shaft.
6. Find the best metal welder in the country and have him/her weld the two pointed ends together. This welder has to be super good, with years of experience, and knowledge of joining two pieces of metal together. Your life will depend on it.
7. After welding, straighten the welded shaft. Turn the welded area in a lathe so it is the same diameter as the rest of the shaft.
8. Cut the joined shaft to the proper length.
9. Machine the new end in a lathe for the taper and thread. Cut a new woodruff key seat in the taper at the bottom of shaft. Drill new cotter pin hole through the threaded portion of the shaft.
Turning down a worn shaft and building it up with a bushing is generally not effective because of the woodruff key seat. It also reduces the diameter of the steel at a point where you need the full diameter of the he steel for strength and safety.
I do not agree at all.
If you must replace the steering shaft, I would go get a new piece of 3/4 inch cold rolled shaft stock, or just cold rolled. Machine the ends properly and weld it to the salvaged top spider. The welding as you point out needs to be the best in the world. this is not the place for high school shop welding.
But these things are not all that rare, finding a good one is not that difficult. Does not seem wise to risk a steering failure.
Erick , Is the shaft different on the 5:1 from the 4:1 ? or are they the same
The main shaft, the three sun gears, and the planet gear / shaft assemblies are all unique to either 4:1 or 5:1 Lorenzo. You cannot change ratios without having all five items.
The main shaft assembly is different lengths for different years so that is also a consideration.
If not mentioned already as an alternative, here's what I have done.
Turn down the end of the steering shaft to a straight, consistent diameter. Don't reduce the diameter of the smallest area, just make it all the same for as far as it extends into the lower mount. Where the reduced diameter meets the rest of the shaft blend the small diameter in gradually, don't leave a square shoulder in other words.
Then make a new bushing suitable to fit the reduced shaft.
Since you're not really making the shaft any smaller than it was at its smallest point, you're not really reducing its strength any more than before it was machined.
I have built the shafts up with braze and then turned it back to original size. NO problems with this in the past thirty years. Still working.
I've just crawled out of bed, (5.50AM here) to see all these responses to my querie.
Thanks to you all for taking the time to answer with all that good advice. Its much appreciated.
I had a shaft repaired by having the worn area spray welded and turned back down. On my shaft, it was only worn down on about one half of the circumference. Simple and worked great. Dave
I would either replace the shaft, or cut and weld the acceptable lower portion from any year donor shaft. Prior to welding, the sections need to be fastened together with steel all-thread.
I just finished replacing the shaft, lower bracket bushing and bored/re-bushed the gear cover. Bought the shaft from Chaffin's for $185.00.
Previously, I replaced the shaft and gear set (Used) with 5/1.
The used gear set fit the new shaft and gear pinion pins perfectly with no modifications required. I really like the 5/1 ratio compared to the original in my 13.
I do not feel the cost for doing this "Is A Cost Prohibitive Exercise" considering the risks involved trying to repair an old worn shaft.
I consider it a wise and affordable investment. Spent much more than that going to a swap meet.