last updated 6/19/2019
There was an engineer in Italy named Antonio Boschi. He invented, patented, and started a company around a flex joint he invented after WWII. The "giunto Boschi," or Boschi joint, became the basis for the name of the thing, and for the company: GIUnto BOschi, or giubo. (People pronounce it "gee-you-bo" or "gwee-bo.")
Anyway, they don't hold up too well after 60 years. Not because it's not a genius design for a vibration-damping, high-torque flex joint, but because rubber, 60-year-old rubber in particular, stops being rubbery and starts being more like dried Pla-Doh.
I tried to drive the Vespa this week (having installed a new 3.5-10 inner tube in the right rear tire; thank you ScooterWest), and there was a rough noise and a hunk o'giubo fell out in the driveway.
Hunk o' giubo. Two of six sides of the hexagon, three of six of the bolt holes, some sheared screws, and evidence of former mischief (in the stack of washers).
The sheared-off screws mean I'll be hunting up my screw-extractor kit, I think. I have to get under there and see what's what. (Update: screw extractor not required. It's just hex-head screws with castle nuts.)
Thankfully, there are locals with 400s. Wonderful people, willing to help! I have leads on parts.
Half-shaft repaired by weld.
Joint at transmission *minus* the giubo; driver's side. You can sort of see the curvature of the bent half-shaft, especially toward the bottom of the image.
Got a good look yesterday. The giubo must have already been partly gone, because there was only one bolt and one vertex of the hexagon left.The half-shaft is bent, and it doesn't look new damage. And there's an old weld repair to the half shaft. I think it's re-repairable. Nonetheless, I am waiting to hear from a man in France about some new bits! (Update: The man in France is out of touch at the moment. I am working on some home-made remedies... 3-D printing or sections of old tire.)
Took left half-shaft out today... ooh! that's BENT!
It twisted but didn't break! The splines are straight where they were within the mated part.
I still think the damage to this half-shaft and the flex-joint was the reason the car was put away in '76.
Suppose I couldnt get new giubos? I worked on some other possibilities. Some modern BMW flex joints. Way stiffer, but I thought I could machine them to be lighter. And the coolest possiblity: I 3-D printed a prototype out of a rubbery material whose brand name is NinjaFlex. Might get back to that someday, but there was good news from France: I could buy the replacement parts I needed.
Left, 3D printed test version of a giubo. Right, modern replacement part from the BWM 3-series.
Knock wood, screws are unscrewing, bleeders aren't frozen, wheel hubs come off without heat and without solvents, etc., and I am a very thankful mechanic! Spent a few hours checking and working the brake system over the last few days. I disassembled the master cylinder (it was full of varnish-y "fluid" and wasn't rebounding - no surprise after 43 years) and even it cleaned up nicely! Disassembled the slave cylinder on driver's rear (where the half-shaft came out) and it was pretty good! Rubber is still lively, walls smooth and gunk-free, etc.) So I just did a thorough purge of the other three. All the wheels spin freely when they're supposed to, and stop crisply if ordered. Nice.
Big thank you to Nicolas Courtonne! Got me a pair of aftermarket giubos and a replacement half-shaft (*with* the bearing carrier, nice!) and the parts arrived this morning. Tonight at about 9 pm, the car drove for the first time in 43 years. Some tire rot makes for a b'bump, b'bump, b'bump kind of ride, and there's some vibration in the drive train somewhere, but it goes! Speedo even works.
Pretty cool. Pics to follow in Part VI