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Crankshaft Failure - a remedy from 1964? - GK5268 - 06-02-2019
On page 122 of the Austin Seven Companion, G W Meakin wrote in 1964 about a change he made to the crankshaft bearings that he thought might reduce the possibility of a crankshaft breakage, while you all hurry to your copy of the A7C to read his comments, I will summarise:
Basically, G W Meakin was saying that he located the crankshaft at the rear using a heavy-duty ball race and then "pinched" this into place using a suitably thick shim between this and the flywheel. He then removed the front bearing fixings, so that the front pair of bearings were allowed to "float".
G W Meakin said that the modification gives quieter, smoother running, but more power all up the rev range, especially at the top end.
In terms of reducing the prospect of a broken crankshaft, G W Meakin thought that clutch pressure was all concentrated at the rear end of the crankshaft only, now being fully supported, leaving the rest of the crankshaft less stressed, particularly, during whipping.
I thought that it was interesting post and wondered if anyone has ever taken this approach with their engines, and if so, were G W Meakin's results validated?
Responses please!
RE: Crankshaft Failure - a remedy from 1964? - Bob Culver - 06-02-2019
This topic been extensively canvassed before. Judging by apparently infinite fatigue life of normal bearings, the size of bearings in powerful bike engines, the increased ratings of modern bearings, a ball race would be fine. A considerable potential cost saving (and maybe only one front roller need be new). The slight difficulty is arranging for positive clamping of the ball bearing. Other ball race engines such as BSA car adopt the arrangement. Cranks usually crack from the inside radii so the contribution of clutch pressure is questionable? Firing and inertia/centrifugal loads in an engine are vastly greater than most , including mechanics, suppose and tend to dwarf the occasional clutch load. With the front of crank more free I dunno if any hammering action on timing gears may occur.
(Dunno about the model which Edge had access to, but 1923 FN is as Seven)
RE: Crankshaft Failure - a remedy from 1964? - Bob Kneale - 06-02-2019
I too have been interested in this since Charles P raised it as a side issue in a post (Odd Noise) about a year ago. I've sourced the ball race he mentioned as well as a pair of 1 1/8" roller races for the front bearing. My interest is to try to lengthen the life expectancy of that much maligned 3 bearing crank, which must suffer unnecessarily from bending loads when the clutch pedal is depressed. Bearing in mind that the centre webs are only 0.3" thick, is it surprising that so many failures occur in that area?
Having suffered the total destruction (at 20 mph) of the bottom end of a 2 bearing engine I'm keen to try a 2 bearing conversion as well.
The roller races are available from Bearing Services Norwich Ltd who showed interest when I explained what I was planning to do.
MRJ1.1/8C3
Cylindrical Roller Bearing, rollers attached to inner ring full floating outer ring (1.1/8x2.13/16x13/16) (BSA Goldstar crankshaft drive side 1950-1953, OEM 65-1388
Manufactured for us by NKE Bearings Austria
Hope this is helpful and causes others to other interested parties!
Cheers
Bob
RE: Crankshaft Failure - a remedy from 1964? - Alan - 06-02-2019
Like Bob, I'm somewhat sceptical about the influence clutch loading has on crank failure. I'd wonder too about the effect on timing gears. I'm trying hard to visualise what happens to cam and ignition timing as the crank whips. Interesting- it might even be beneficial.
Ever since God was a lad people have been investigating new bearing arrangements for Austin sevens. The one that interested me, years ago was self aligning bearings. Crank whip exerts a far greater force on the engine than clutch loading. Try bending a crank 25 thou and you will see what I mean. I think allowing the crank to bend freely is far more important than absorbing the clutch load.
RE: Crankshaft Failure - a remedy from 1964? - Zetomagneto - 06-02-2019
(06-02-2019, 11:09 PM)Alan Wrote: Like Bob, I'm somewhat sceptical about the influence clutch loading has on crank failure. I'd wonder too about the effect on timing gears. I'm trying hard to visualise what happens to cam and ignition timing as the crank whips. Interesting- it might even be beneficial.My only interest in using a ball rear main is to save repairing a broken lip on one of my crankcases.
Ever since God was a lad people have been investigating new bearing arrangements for Austin sevens. The one that interested me, years ago was self aligning bearings. Crank whip exerts a far greater force on the engine than clutch loading. Try bending a crank 25 thou and you will see what I mean. I think allowing the crank to bend freely is far more important than absorbing the clutch load.
You would need to make up a spacer to go between the flywheel and inner track.
(06-02-2019, 10:42 PM)Bob Kneale Wrote: I too have been interested in this since Charles P raised it as a side issue in a post (Odd Noise) about a year ago. I've sourced the ball race he mentioned as well as a pair of 1 1/8" roller races for the front bearing. My interest is to try to lengthen the life expectancy of that much maligned 3 bearing crank, which must suffer unnecessarily from bending loads when the clutch pedal is depressed. Bearing in mind that the centre webs are only 0.3" thick, is it surprising that so many failures occur in that area?These are the bearings used in the earlier engines, nothing special about them, readily available from our cherished suppliers, check prices before buying, Jamie does RHP.I wouldn’t use cheap bearings.
Having suffered the total destruction (at 20 mph) of the bottom end of a 2 bearing engine I'm keen to try a 2 bearing conversion as well.
The roller races are available from Bearing Services Norwich Ltd who showed interest when I explained what I was planning to do.
MRJ1.1/8C3
Cylindrical Roller Bearing, rollers attached to inner ring full floating outer ring (1.1/8x2.13/16x13/16) (BSA Goldstar crankshaft drive side 1950-1953, OEM 65-1388
Manufactured for us by NKE Bearings Austria
Hope this is helpful and causes others to other interested parties!
Cheers
Bob
RE: Crankshaft Failure - a remedy from 1964? - Bob Culver - 06-02-2019
For the deflections involved I doubt if the bearings and crankcase offer significant restraint. If you assemble the bearing at one end only can spring the crank a long way with just a few pounds pressure and there are many hundreds loose in an engine. Other 2 brg makes with plain bearings were not hopelessly prone to failure. A.C races adjusted for slight preload are relatively rigid but the front of cranks do not snap off.
The arithmetic is now beyond me but I suspect the plane of the spinning crank offers notable resistance.
For the average amateur the Companion book would be improved with many of the musings deleted!
I think the self aligning bearings were more aimed at reducing wear. Esp with older oils this was a problem, probably worsened by the tilting
RE: Crankshaft Failure - a remedy from 1964? - Zetomagneto - 06-02-2019
(06-02-2019, 11:44 PM)EBob Culver Wrote: For the deflections involved I doubt if the bearings and crankcase offer significant restraint. If you assemble the bearing at one end only can spring the crank a long way with just a few pounds pressure and there are many hundreds loose in an engine. Other 2 brg makes with plain bearings were not hopelessly prone to failure. A.C races adjusted for slight preload are relatively rigid but the front of cranks do not snap off.
The arithmetic is now beyond me but I suspect the plane of the spinning crank offers notable resistance.
For the average amateur the Companion book would be improved with many of the musings deleted!
Bob, as you know the companion has been around well prior to Phoenix cranks.
For 2 bearing engines Phoenix, or if you can afford it or think it necessary Hadley cranks are the way to go.I know a number of Phoenix have broken, due to poor regrind or abuse but unusual.
RE: Crankshaft Failure - a remedy from 1964? - Bill Sheehan - 06-02-2019
(06-02-2019, 11:44 PM)Bob Culver Wrote: For the deflections involved I doubt if the bearings and crankcase offer significant restraint. If you assemble the bearing at one end only can spring the crank a long way with just a few pounds pressure and there are many hundreds loose in an engine. Other 2 brg makes with plain bearings were not hopelessly prone to failure. A.C races adjusted for slight preload are relatively rigid but the front of cranks do not snap off.
The arithmetic is now beyond me but I suspect the plane of the spinning crank offers notable resistance.
For the average amateur the Companion book would be improved with many of the musings deleted!
Without getting involved in the technical considerations, my memory says that the then consensus was that in practice it was a failure after a short time. Cheers, Bill in Oz
RE: Crankshaft Failure - a remedy from 1964? - AustinWood - 07-02-2019
Pinching the bearing in place with the flywheel raises the likelihood the the flywheel isn't pull tight on the taper. If it isn;t the flywheel we come loose.
RE: Crankshaft Failure - a remedy from 1964? - Geoff Harrison - 07-02-2019
Geoff. Meakin was an RAC ( as it was in the 1960 - 70's ) scrutineer mainly at Brands Hatch . and a senior engineer with London
Transport . He will probably have known what he was talking about from his own competition experience in 750 events at the time.
He died quite suddenly in the late 60's .
As his article was pre the stiff cranks that are now available , time , experience and personal preference etc., changes the bearing picture.