TR4/4A TR4 Fan Post Mortem

[Geo Hahn]

To paraphrase Oscar Wilde -- lose one fan, that's misfortune. Lose a second fan and it begins to look like carelessness.

So my question (apart from the ones I asked in another thread) is -- why did this happen again?

The first fan was the original 44 year-old-part so naturally I just chalked that up to age. It may have even suffered some trauma the week before the failure when I drove thru a dry wash and scooped up a load of sand.

The second was a used fan that appeared fine. I balanced the fan itself but did not remove the hub from the engine and balance the pair as a unit.

Bad Karma? Failure to balance? Symptom of something else?

 

[HerronScott]

Geo,

Thanks for the pictures. I was going to ask in your other thread as I had never seen a broken one and wanted to see where they failed.

Sorry can't help on the why though since I can't imagine what would cause the break across the fan blade like that.

Scott

 

[Geo Hahn]

FWIW -- In both cases it appears that the fracture went from right to left (as viewed in the photo) and the last bit to let go (showing signs of flexing & work hardening) was the left hand edge.

 

[vivdownunder]

It's a problem that's been known for 51 years. Fan blade failures ruined the factory TR3S campaign at Le Mans in 1959 when two cars had to retire with damaged radiators. Valuable time was lost removing the fan from the third car, although its eventual DNF was due to a lack of oil pressure.

Viv.

 

[DNK]

George, you been running your car at Le Mans again?

 

[Andrew Mace]

It's a problem that's been known for 51 years. Fan blade failures ruined the factory TR3S campaign at Le Mans in 1959 when two cars had to retire with damaged radiators. Valuable time was lost removing the fan from the third car, although its eventual DNF was due to a lack of oil pressure.

Viv.

All true. However, the TR3S cars were running much higher speeds (and with a very different engine) than any of us is likely to encounter. Also, it is not always mentioned that competitions manager Ken Richardson had fought NOT to have fan blades installed on the Le Mans cars but was overruled by someone higher up. Turned out he was right.

 

[angelfj1]

Geo, one theory that I have heard is that the outer most rivit loosens allowing cyclical movement of the blade at that point. This continues until the blade fatigues at that point and a crack starts.

 

[TexasKnucklehead]

Is the angle (pitch) of each blade exactly the same?

Those failures look very much alike. Is that top rivet loose now?

FWIW, I looked very hard at the pictures, but can not see any carelessness.

 

[KVH]

George, I'm shocked by what I see and what appears to be a pattern.

Your post about the mysterious happenings to your TR4 is precisely your 4440th post over a period of many years. In addition, your 4-bladed fan, which fastens with 4 bolts, appears to have failed in precisely the same spot, in each case with the culprit being the 4th rivet at the top. In addition to these painfully eerie revelations, you chose to share with us that your fan was 44 years old.

I'm sorry, but I'll have to look into this much deeper and report back with my further conclusions.

 

[Andrew Mace]

Might want to check with the Group 44 folks.... :laugh:

 

[hondo402000]

Well you can grind off the rivets, make new blades from some new AL and rivet them back on. I am sure you can get rivets somewhere, heat them up with a torch and pean them down, or bolt them with nylocks, they probably used rivets instead of bolts because rivets were cheaper

Hondo

 

[Geo Hahn]

Well you can grind off the rivets, make new blades from some new AL and rivet them back on...

That was my wife's suggestion though she pointed out that I actually have 3 spare blades to choose from... i.e. remove the best remaining blade from one fan and rivet it on in place of the broken blade on the other fan.

I may actually try that though for now I have sourced a replacement through the kindness of a Forum member.

I did just now check the rivets and it appears to me that they are all nice and tight.