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Used triumph connecting rods

7K views 34 replies 17 participants last post by  Truckedup 
#1 ·
Picked up some cheap used con rods at the swap meet for my '66 T120 build. They appear to have been bead blasted all over including the surfaces where the shell bearings seat. Do you reckon these are usable or likely to have been blasted out of round or outsized. I think even the bolts got blasted
 
#5 ·
Especially for triumphs ,when the Aluminium alloy rod has got to the point of needing to be resized , it has reached the end of its serviceable life and should be chucked
Bead blasted conrods are a disaster waiting to happen , the glass beads put stress risers (in this case , small sharp indents) into what is a highly stressed component ,inviting rod failure.
Cheers R
 
#7 ·
Do you mean shot peening them by blasting ? It compresses the outer surface of the rod , i think they are polished after the blasting. In fairness to the triumph twin engines they never had a reputation for breaking rods like the triple or the nortons.
 
#8 ·
Aluminum is not like steel..A steel rod will last forever if not pushed beyond it's design limits. No so with aluminum, it can fail and will eventually fail even if the design limit is never exceeded.
When the big end measures out of round this is a warning not to use the rod..it's at the end of it's service life.
Many old Triumphs now have an easy life so the rods are not such a big factor.
If you ride a Triumph like the sporting machine it is,think about rods.
 
#9 ·
rdobirdman ,bon is on the money, Bead blasting is not the same as shot peening , Shot peening is a controlled process to give a surface compressed strenght using spherical material
see here http://www.engineeredabrasives.com/what-is-shot-peening.html
Bead blasting is random and the glass bead is abrasive and often leaves sharp nicks in the material.
I often demonstrate to new staff at my work on a hand bender , bending 6mm stainless rod .In polished form it bends with no sign of fatigue cracks , then I bend a glass bead blasted peice of the same stainless and quite often it cracks -by no means a scientific experiment but it gets the message across.
cheers R
 
#11 ·
You are spoilt for choice in regards to seriously well engineered con rods for old bikes these days, MAP in florida, carillo, falcon etc etc. Of course money is a problem as they are not cheap, but they do give you peace of mind if you are riding an old bike hard.
 
#12 ·
I can't believe everyone is dooming these poor little Triumph rods without seeing a picture. What if he is talking about a light cleanup with glass bead? What if the guy is just wrong about the surface being glass beaded. I have used the SHIT out of Triumph connecting rods in harsh racing conditions, I am not speaking from some knowledge out of a book somewhere about stress bullshit and blah blah blah. Not that anyone is blah blah blahing in particular, don't wanna offend all glass beading, stress tester experts out there. But I am just saying back up a little bit and lets get a picture.

Oh and I have glass beaded Triumph rods and then stuck them right in a race motor burning 50% nitromethane at 9000RPMs and have not broken one. Just my little actual experience speaking, nothing you should really pay any attention to.
 
#13 ·
We had a blast cabinet in work that used glass beads, if you look really closely the beads are round and will not cause nicks as someone suggested, i used to blast everything in that cabinet (except oil tanks). Rick parkington who writes in classic bike magazine rasped around the isle of man tt course as hard as he coukd on an old bsa a10 with rods he knew were in bad shape, to see if the rods would break, they didn't.
 
#15 ·
Bit late replying here. Surely if they're not seriously out of round, a resize will just make sure the shells seat OK? For a road bike this surely wouldn't be a problem? I've seen lots of road rods with nicks in them (admittedly, a long time ago...:eek: ). Come to think of it, I've never actually seen a busted rod on a road bike. Drag bikes are a different story!
 
#28 ·
I'm a retired warehouse worker, so what do I know. But what I'm seeing on this rod cap is rust pitting that has been cleaned by some kind of abrasive process.
I've seen lots of guns with this same surface condition.
And, I've been around a lot of automotive rods that were shot peened, but never in the saddles!
 
#21 ·
On the bead blasting.... In this country drag racing is where you find the most common use of aluminum rods in car type engines. Some are the 6000 hp fuel dragsters. All the aluminum rods from different manufacturers I have seen have a polished surface.I have no idea if the rods are machined,then blasted,then polished.Or just polished after machining. Someone was making a dull surface aluminum "racing" aftermarket rods for Triumphs in the recent past.
 
#22 ·
Yeah far be it for me to go against a norm, but I have been blasting rods for a long time now (aluminum and steel) and never had a failure due to the process. I think the most common finish is fully machined (or polished because for older forgings its simply the easiest cheapest to ward off corrosion, stress etc....) but have seen in the past rods shot peened then anodized (RC Engineering Golden Rods for single cam Hondas)
 
#23 ·
I see you have two options but it comes down to cost. After measuring the rod ends and they are within tolerances have them professionally Shot peened, polished and magnufluxed then they can be used keeping in mind that they are used and reconditioned. Other option is buy new quality rods and move forward with build. When cost is factored in youre going to be laying out near the same amount.
 
#27 ·
Have you checked roundness of the big end? We here on the other end of the interwebs are working strictly on your pictures, not actual measurements, so our opinions are really just that. That said, I have a fat stack of rods that are nicked up or stretched....too risky for me to reuse. Your rods, your choice, but measure them so you can make an informed decision.
 
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