MTFCA Forum

Constantly inspecting and cleaning up parts, I noticed something odd about my fan hub.
The belt hub itself spins true. The fan blades themselves spin true. However, the hub shaft and blade flange are spinning 0.097" off center!! The rivets for the blades were drilled true to shaft center, not with the flange.

Begs the question as to production tolerences, or if this is more common than not, but regardless the belt hub & blades run true. On one hand one wonders whether this much out of balance, miniscule as it may be, causes any issues (bearing wear, vibration, etc). Other hand says it's survived OK for 116 years ya dummy, whatchya concerned about?? LOL
But, just found it curious....

If it were out-of-balance wouldn't the fan belt fall off.

Most any sand cast surface that is not machined will be somewhat irregular. I doubt if Ford balanced the hub casting. If the blade assembly and belt running surface run true, it ought to be OK. The hub casting may have internal irregularities that offset the external irregularity. Any imbalance close to the center of rotation will have far less effect than the same amount of imbalance further away from the center of rotation. For instance, a quarter taped to the hub casting would probably have no noticeable effect at the speeds the hub runs at, but the same quarter attached to the outer edge of one of the fan blades most likely would.

Just kinda hard to imagine a casting/machining process that would be so significantly off center...you'd think 0.10 would be a huge deviation, but obviously not.
But, 116 years ago, that was obviously "AH, it's good enough"

Some of the things I have seen on original parts makes me believe that the quality check @ Ford back then was:
If it starts and drives away, then its good.

For most of the production of the Ford Model T the problem was he could not build them fast enough.
Ford was making over 7000 cars a day 6 days a week and 2 million cars and trucks per year.
He wanted to produce a quality product but at that production speed, things were not always what we expect today.

It's a slow speed fan and a really small distance from the axis to the weight offset.
As bad as it looks I don't think its a very noticeable vibration.
The crankshaft is not balanced, the wheels are not balanced, nothing really is.
It would be interesting to test and see how much vibration it really puts out.
Mike

The part is correct where it needs to be. The "as cast" surface is non-functional. Variations in castings were/are common. Apparently, this hub has been functional for 116 years and I suppose any balance issues have not yet arisen in all that time.

If your fan assembly is the earlier style mounted on a swing arm and tensioned with a spring, any significant radial imbalance at any reasonable speed would be very obvious by reason of shaking of the assembly. If you can afford it, truing and balancing every rotating part and assembly on the car would be nice.... but you'd have Rolls Royce money in the car.

Yes to all that.
Just another fun Ford T observation!
Quirky things that they are!

It does look bad..... maybe it's a "gyp part".....

Daisy Mae wrote: ↑

Fri Jan 09, 2026 10:32 am

Yes to all that.
Just another fun Ford T observation!
Quirky things that they are!

Yes, agreed!

The fans on early cars with the spring loaded arms had brass hubs. Nor has this one seen 116 years of service. That would make it 1910 or earlier, again in the era of brass hubs.
Those cast steel hubs must have been made of stern stuff. Riveting four blades with multiple rivets to such a thin flange and having it serve well is testament to the quality of the material.

Allan from down under.

Oops...oh lord, how embarrassing, my head math is going wonky!! Damn, I'm going senile!!
AAAAAHHHHH!!!