Ringing Cranks

[Bob Culver]

Whilst hewing path through my basement I stumbled upon my collection of cracked cranks. There has occasionally been mention of ringing so I had a little play. I have rung many Javelin cranks and timed the sound and found wide variation between shafts apparently  all OK and one with small crack. I have hung Seven shafts from the front and rear with no conclusions. This time I rested on a narrow edge at the centre. With the other end held the fronts rang clearly better than the rear where the known cracks are. Has anyone done this with a known good crank and is there a significant difference depending whether the front or rear rung?

[Chris KC]

It's not a direct answer to your question Bob but in my humble opinion crank ringing, although better than nothing, will only find a total dud and is by no means a dependable test of durability. I don't think there is any completely fool-proof crack test method available to the impecunious amateur, but I generally use dye penetrant at home, and if nothing found I pay the man to do a magnaflux test for me (which is better at finding flaws just below the surface). And yes I would 'ring' it first to save wasting dye! It is also my experience that most flaws flagged up by dye penetrant are visible to the eye if you look carefully. Given the cost of an engine rebuild nowadays it seems a false economy not to use every available means to ensure a crank is sound.

[Alan]

I’d rephrase that Chris and say it seems a false economy not to use a new crank.

[Chris KC]

I wouldn't completely disagree Alan - certainly I think it would be nuts to commission an engine build costing thousands with an 80 or 90-year old shaft when new parts can be had off the shelf. On the other hand I wouldn't want to deter those striving for originality (and perhaps with only modest driving ambitions) or those building on a shoestring - there are still a few good used cranks around.

[Bob Culver]

I long ago convinced myself that ringing is of very limited usefulness but just curious not having a perfect one loose. I hunt cracks with a bar magnet and black fluid, starting at the back. The cracks are not visible by eye, except where been built up by welding. From the sheer number of cracked cranks very many engines must have innocently done very many miles flawed. From selected used bits and with patience surprisingly reliable and long lived engines can often be assembled at very low cost; for modest use hard to justify the now huge cost of a Phoenix. Crack free cranks must have 10,000 or 20,000 miles of original type driving in them; more than many cars will ever do.

[David Stepney]

I have recently had my RP's engine to bits to fit new pistons to get rid of a little end rattle that had developed over the time I have owned the car. I have now owned the car for two years and have managed to clock up nearly ten thousand miles in this time. The current mileage is (1)04367 which I have reason to believe is genuine.

Whilst it was in bits, I checked the big ends, which proved to be in good order. As I turned the crank, I noticed for the first time that the engine number is engraved on one of the webs and accords with the cars' engine number. It seems, therefore that, with care, the bottom end of a two bearing Seven engine is, all things taken equally, pretty robust. Indeed, the only attention that the bottom end has received was the replacement of the rear main bearing shortly after I had the car and some 7K miles ago.

Apart from one of Robert Foreman's reworked LC heads, which has improved its' hill climbing ability (essential in the North Wales hinterland) the engine is completely standard.

The little car is running well and I am therefore inclined to leave things alone, or am I courting disaster?

[mk1-mark]

"Ringing" of forged components to discern whether they are cracked or not is a TOTAL WASTE OF TIME.

Most cracks that you would be able to hear would be easily bad enough to see.  Those that are there but invisible to the naked eye would be impossible to hear.

The way to see if a crank is cracked or not is to crack test it.  This can be done either by a professional or using a proprietary 3 stage crack testing kit for the princely sum of under a tenner.

https://www.gas-uk.co.uk/crack-detection-spray-set.html

[Ivor Hawkins]

I have to admit I’ve had cracked cranks that have rung like a bell!

My current box saloon has a rebuilt engine with its original crank (though I would have fitted a new crank if I had built it) nevertheless, my 34 Austin had over 250,000 miles on its original crank, so I’m not overly concerned with the Seven apart from the potential damage to the crankcase if it does go.

I think I’ll leave ringing to the campanologists!