triumph rods on A65 crank

[DAVE BRADY]

I have asked this in Star and Garter but it may be best to ask here.

I have crank that has been badly reground with no radius on the big end journals.  It is on -20.  Will another grind be enough to restore the radius?  If not recoverable by a -40 what about reducing the size to take a Triumph rod?
I have a pair of Triumph rods.  the length is the same but the big end is wider and does not sit on the A65 journal.  Would it be feasible to machine the rod to fit?

Dave.

[chaz]

Cant tell you for definite but consider the rads  to be .040 then .020 is only half of what you need.
Option 1,  whoever's ground pays for a replacement crank
Option 2, metal spray the throws and regrind, who pays.
Option 3, buy another crank.
Option 4, as both marques were similar, I would expect similar sizes so may need bigger rads anyway.

[Mike Farmer]

 

Firstly I would take the crank to a good engineer and have it measured/assessed. If it has enuf meat on it then simple regrind.

If not I would go for metal spray and regrind back to std size. Even if you obtain another crank you may still(probably) have to pay for a regrind and of course that way you will know exactly what you have in your motor.

Mike

[LightningAndStarfire]

I know Triumph rods have ben used in A65:s coz they were considered to be stronger. But I haven't seen any info about the depth of hardening for the A65 big end journals. In my opinion this should first be researched as the basis for a good mod.

[DAVE BRADY]

Thanks for the replies.

The crank has been in my possession for a while and was like this when I got it so I will have to find the solution rather than go back to whoever did the work.

The BSA workshop manual specifies a radius of 0.115 to 0.120 for all regrinds with only up to 3 grinds listed so -30 is the max.  This could be because of the depth of hardening so perhaps re-hardening is an option after say a -40 grind but would a -40 grind be enough to restore the required radius?  If not then metal spraying looks like the only answer. and then BSA rods could be used.

The Triumph rods would only need a small amount of slimming down to fit and it looks like the shells are a bit wider than the BSA ones - is this a benefit?

Dave.

[LightningAndStarfire]

Ed Valiket of E & V Engineering in the USA is a BSA tuner in high regard. He may know if Triumph rods is a good idea.

[DAVE BRADY]

Thanks for that.  I have sent a message to E&V.

I have tried to find out if the BSA cranks were hardened or if the quality of the steel was good enough considering the softness of the shell material.  So far it looks like they are hard enough but I may eventually have to consult a crank expert.  It does seem, however that the radius is quite important so what ever happens this must be restored.
The later A65 cranks have a much smaller oil gallery so I would think that there is plenty metal in the journal and it is possible to get -040 shells but if my calculations are correct the current surface with almost no radius would have to be ground down by another 0.120 to get the radius correct.  Am I right on this anyone?

Dave. 

[LightningAndStarfire]

I think you would be ok with a 0.100 radius that blends in well and is polished. Then you can use the BSA rods and shells.

[DAVE BRADY]

I have just had a look at a few cranks and non seem to have much of a radius.  The radius in the manual is 0.115 to 0.120 so quite obvious and using something of about 0.240" diameter, almost 1/4 ", should give the right curve.  Checking visually, the cranks I checked where not even close to this.  The use of a 0.100 radius may, as suggested, be acceptable. 
If the crank is currently 1.667 dia., (-20 from std.) so if ground to take -40 (from standard) shells then the diameter of the journal is reduced to 1.647 so the surface in relation to the web is effectively lowered by 0.020".  Is this enough to get anything more than a 0.020 radius?
Again, looking at the cranks I have, the radii do not look much more than this so is the blending of the journal in to the web more important than the actual radius?

Dave.

[chaz]

the reason for the radii in the corners is safety. a square corner is a fracture point. I had a Harley 1988 and the mainshaft broke, Harley re designed the Ironheads shaft for the evo motor the square corner fractured and wrote off 5 of the 8 gears. the repair was to fit the ironhead shaft and 1st gear which had the radius in the corners .
so, for safety the bigger the better. when we made and ground compressor cranks for train brake systems there would have been around .125" rads in the corners and they were slow running cranks, around 500 /1000 rpm and from memory 1.500" dia journals.

[DAVE BRADY]

From what I have been reading I would agree.  I have had a reply from E&V and what I understand is that whilst using Triumph rods is doable it would probably mean removing material from the inner face of the journal only to accommodate the wider rod rather than make the rod narrower.  Considering that the rod would have to reduced by equal amount on each side it would not leave much metal where the location tab goes and even then the wider shall may ride partly on the radius.
SRM can supply -050 shells so that means a bit more radius.  I have put the question to them but suspect that I will be looking to get the journals built back up to standard.
Has anyone had this done and how many miles have been covered?

Dave.

[chaz]

I can only speak from rail compressor experience, bike cranks I just shop around until I find one I can use.
we used to cast our own cast Iron cranks and buy in steel crank blanks to our spec. we would then rough turn initially on a lathe then laterly on a CNC lathe, after which they were milled , rough ground then straightened and finish ground .grinding plain diameters on one grinder and using special offset blocks to grind the throws on another grinder.
we have inthe past , due to machining errors, then on reconditioning compressors had single or multiple throws welded or metal sprayed then returned to re grind to use again. we always use zero shell bearings no -.010 etc undersize shells.
it can be done but dont know who now.

Ive not used personally but a friend has had his rally car cranks done here. http://www.robwalkerengineering.co.uk/

[Mike Farmer]

 

I know a guy who used to do this work. I've emailed him to see if he is still operating. Where are you.

Mike

[Mike Farmer]

 

Hi agen. Greetings

I've just received an answer from the engineer who has previously done a whole bunch of work for me. All sorts of jobs from re=lining A65 cylinders to regrinding a 5.5 litre mid 20's crank. I have always been happy with his work. He is still operating. Let me know if you are interested and I'll send you his details.

Mike

[DAVE BRADY]

Hi Mike,

Yes, his details would be useful, I am in North Lincs.  I have been going through my various A10/A65 manuals and there is another interesting twist on the required radius on the big end journals.
Service sheet 207 refers to the journal radius being 0.085 - 0.090 on small and large journal A7 and A10 cranks.  It also refers to A65 cranks up to '66/'67 having this radius.
In another workshop manual for '66 to '68 (revised edition) it has ambiguous information.  In the text next to the big end diagrams it refers to a radius of 0.085 - 0.090 but on the diagram it states 0.115 - 0.120.  So a bit confusing but it looks like the larger radius is the updated specification.  This is born out by the '71 manual which only has the 0.115 - 0.120 figures.
Did crank failures prompt the bigger and therefore stronger radius?  Would all the cranks, whether small or large journal, benefit, if possible, from a bigger radius? 

SRM do a -0.050 shell so I have asked them if a regrind to this undersize would restore sufficient radius. No reply yet.
I am still hoping to not to have to go this far undersize as it is actually a genuine A70 crank and only on -0.020.

The other way to get the radius is to have a groove ground around the edges of the journal by a specialist.  This is used on some cranks so a proven method.

Dave.