Keep on Rolling (Post # 111)

The abrasions on the inside of the Borrani wire wheel rims
show as dots where the brake drums come closest to the
wheel rims. 

The front brake drum profile. Note the four distinct facets

that mimic contours inside the wheel rim. The "furrow"

 shows on the fins of the middle facet.

After putting about 5 km on The Alfatross in preparation for the Arizona Concours d'Elegance I noticed some abrasions on the inside of the front Borrani wheel rims that seemed to be the result of the rims lightly touching the finned drums in some places. There was no interference problems between the rear drums and wheels because the drums there are much smaller in diameter. 

I checked the fins on the drums and observed that every fin on one of the four facets on the perimeter of the drums has a shallow “furrow” in it corresponding to the place on the wheel where the abrasions appear. But the furrow was not caused by contact with the wheel.  It appears to have been evenly and professionally machined into the fins before I got the car, so it may even be a “pre-existing condition”.  


But what was causing the problem and how do I fix it? Time to contact the Alfa 1900 Brain Trust members and Cork Adams, the guy who restored the wheels, for advice. 

Cork opined in an e-mail "It appears to be a wheel that has slightly too much positive off-set and might require some minor adjustment to pull the hub inward. I assume a quarter of an inch should not move the rim outward enough to rub on the fender." (Groan).

Giuseppe Maranghi suggested that I test-fit the car's other wheels to see if perhaps the wheels and drums are supposed to be paired specifically  If not, I should get in contact with Matteo Bosisio at Borrani to get his take on what the problem might be--after all, they are literally the ones who "invented the wheel"!  Then Joost Gompels sent me what appears to be a period Borrani shop drawing with dimensions so I could check my wheels against it and added hopefully, "I will be interested in what you find out."

Design drawing with dimensions for a Borrani wire wheel .  Joost Gompels.

Suddenly, not only did I have a new, totally unanticipated problem, but it was starting to look like it could take a lot of time and money to fix. 

It seemed like the advice and observations I was getting boiled down to only three possible causes:

1. The wheel hub is centered too far to the outside of the wheel rim. If so, the wheels were assembled wrong during their restoration.
2. Some kind of spacer or shim is missing somewhere on the hub. But there aren't any parts left over or any reference to shims in the design drawings and no place to add a spacer anyway. 
3. Wheel hub isn’t tight enough on the spindle. But how do you estimate how much torque you are putting on the knock-off "wing nuts" when all you can do is hit them with a hammer?

The splined spindle that mates with the hub of the
Borrani wire wheel.  Note the dark abrasion around the
tapered base of the spindle indicating a loose fit.

Because possible cause no. 3 was the easiest to address, I decided to start there, just looking for things that . . . didn't look right. Abrasions on the splined front wheel spindles matched wear marks on the insides of the wheel hubs where they made contact, suggesting that they weren't mating properly, so I sanded and polished both surfaces until I was satisfied that all burrs and refinishing residues were removed.  

But the question of how do you achieve the optimum wing-nut torque, preferably without beating them with a lead hammer, remained.  Beating with a hammer--how barbaric! I used to think that you could find the answer to any question on the Internet if you spent enough time.  I don't anymore.  Try to find the "correct" torque values for knock-off wing nuts on line.  You find everything from "hand tight and then 3 good whacks with the hammer" to "250 to 350 Nm" (184.39-258.15 ft/lb). In the end, I decided to just come up with something I could use that would get the damn wheels seated good and tight on their spindles without hammering the wing nuts to death in the process.  

Precisely at that moment, my neighbor Wyatt Fenn showed up with a 6-pack of pretty good micro brew and time to kill.  As I told my predicament while crying in one of his beers he mentioned that he used to be in prototype manufacturing and promptly sketched a simple wing-nut wrench that could be made of  no. 810-A7 nylon stock. Uh, sorry, Wyatt I'm fresh out of 810--but I do have some heavy plywood . . . .  No problem, plywood works too! 

Rube Goldberg "Proof of concept" wing nut wrench.  Note the finely-crafted plywood workmanship, the profligate use of sheetrock screws, the hand-routed recess for the wing nut, and the clever hole in one arm for easy hanging storage.  Wyatt Fenn design.

A couple of hours later the 6-pack was gone and we had our "proof of concept" wing nut wrench.  I used it for several days tightening and loosening the wheels and it proved three things:  First, that it was vastly superior to the hammer technique and, along with cleaning the mating surfaces, solved the problem completely; second, that all it cost was Wyatt's 6-pack and third, that it could be better.  

More searching on the Internet led eventually to Herr Michael Kirchgassler at Oldtimertools (mk@oldtimertools.de) and his product FMB 42-2. It accomplished the same things that Wyatt's proof of concept did, but more elegantly.  Its compact size eliminated the problems created by the long arms of the proof-of-concept design having only a few degrees of movement before contacting the car body, and its hard plastic wing-gripping toggles were even less injurious to the wing nuts.

The Oldtimertools wing nut socket: What it lacks in 
affordability it makes up for in beautifully engineered 
German manufacturing.   No more guessing at how much 
torque you put on your wing nuts!  

So in the end it was a relatively easy problem to solve. The front wheels were restored properly and no shims or spacers were needed.  The wheels just weren't tight enough on their spindles.  A more experienced restorer could have figured that out in a heartbeat,  but in the end I sure learned a lot and acquired new respect for the deceptively simple-looking wire wheel--and the indispensability of a prototype manufacturing neighbor with a 6-pack of pretty good microbrew!