Andy J
Hero member
- Location
- Isle of Man
Conrod failures
- Thread starter sfcpiet
- Start date
Mine was so badly bent it lost compression, it was really obvious. Happy it didn't lose the valve head. And yes it let me down and came home in a trailer that 600ks after a solid rescue with a bus trip at 6am from Bemboka to Canberra than a train from Canberra to Sydney a taxi to my place then a trip to Curl Curl to get the trailer then a drive to Bemboka arriving at 2am picking the bike up and dropping it back at Eades at 8am the next day. That's 26hrs of constant travelling, and then I slept really well.
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1200ts
Hero member
- Location
- USA - Riverside CA
Does anyone rebuilding triples, ever magnaflux the rods to look for cracks? I am wondering if the rod was on the way out before the rebuild.
What are the choices today for other brands of rods to use. I know there is Carrillo and what else?
Now I am scared to ride any of my triples!
What are the choices today for other brands of rods to use. I know there is Carrillo and what else?
Now I am scared to ride any of my triples!
Keith Nairn uses UK made Arrow rods, especially commissioned it would seem. Do Carillo still make rods for Laverda?
I have some in my 3C. It's done 66 km without any problems since rebuild.
The rods on my SFC were demagnetised. The important magnetism they showed was very likely a side effect of the heat generated by the fire. It's apparently a current practice in the racing world.
Paul
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I remember stopping going up into the hills during one of the Moto Club Breganze rallies. There was a lot of oil on the road and an RGS with a rod through the cases.
Paul
Jo
Hero member
- Location
- Cologne, NRW Germany
Keith Nairn uses ARROW connecting rods on his engine overhauls (picture borrowed from his site):
Cheers,
Jo
Jo
Hero member
- Location
- Cologne, NRW Germany
Sorry Paul, when I read further I only saw that you'd already mentioned it!
Carrillo are still making conrods and would indeed make as many Laverda conrods as one would want, problem is you need someone to order 100 Laverda Conrods to get the price break that is needed to make them affordable
Wolfgang was the dealer doing the big orders and sharing them out to the other dealers and now he is slowing down he is not ordering anymore Carrillo conrods
So the issue is, who wants to place an order for 100 Carrillo conrods and have $30,000 +/- worth of conrods sitting on their shelf, Wolfgang asked me to take over the Carrillo supply but I decided to go with Keith and Arrow conrods as that way Keith and I only needed to stump up for 54 conrods each so was cheaper
Well sort off, still have a stack of money sitting on a shelf
And don't ask about the $18,000 worth of Ross Pistons sitting next to the Arrow conrods
This all comes back to the diminishing supply chain in regards to our Laverda motorcycles, you can already see the disruption happening
There are a number of shortages now, Speedo drive housings and the alloy main gauge mount are two examples, we are about to machine 30 off each of those items as the world has run out but that alone is going to cost me over $5,000
Left hand triple crank webs, right hand 750 crank webs, list is growing every year
Slaters have closed, looks like Andy is looking to wind down, Wolfgang wants to wind down, I am no spring chicken and would like to stop in a few years
Anyone keen to buy any of the above businesses ?
Jo
Hero member
- Location
- Cologne, NRW Germany
True words. We can really count ourselves lucky that there were (so far) specialists who had parts that were no longer available reproduced, or, reproduced them themselves. Those who did make advance payments and stock expensive components for which they can’t always be sure whether this approach would pay off some day. So is the engineering - many of the revisions or racing projects ended up better than they ever left the factory. I am very grateful for that.
But we're all getting older, I don't want to imagine (yet) what the situation might look like in, say, 10 years. But I'm afraid that then there will be near to no one anymore available who'll be able to support the Laverda community, offspring isn’t in sight.
Cheers,
Jo
But we're all getting older, I don't want to imagine (yet) what the situation might look like in, say, 10 years. But I'm afraid that then there will be near to no one anymore available who'll be able to support the Laverda community, offspring isn’t in sight.
Cheers,
Jo
The situation is clear. It would have been nice if the clubs worldwide could have found a will and a way to group energy and ressources, but Laverda clubs worlwide are going the same way as engineers, dealers, and riders.
Once again, I can only quote an editorial from the then ILOC chairman, sometime in the 90s saying " ride your bikes, wear them out, it's the only way to keep up a demand for spares ".
Be reassured however, the maintenance of a 1912 Humber is much easier than that of a Laverda.
Paul
Once again, I can only quote an editorial from the then ILOC chairman, sometime in the 90s saying " ride your bikes, wear them out, it's the only way to keep up a demand for spares ".
Be reassured however, the maintenance of a 1912 Humber is much easier than that of a Laverda.
Paul
Quite certain all heat treatment on the rods would be performed before polishing. Stock rods show colouring at the big end from treatment there, haven't come across any polished SFC rods that were coloured in that area.
Blue colouring occurs at around 290°C, gets paler and peters out at 360°C, when it turns to whitish grey. Pistons see up to 2500°C during combustion at the crown, surface temps would be around 500-600°C, 300°C underneath and being transferred though the gudgeon pin isn't at all impossible. Lots of burnt oil to be found there too, so definitely hotter than 200°C. Exhaust gases are in the 600-1000°C range
These engines definitely benefit from oil jets aiming at the inside of the pistons (been done and works).
piet
When re-fitting stock rods, I use penetrating dye for crack testing. I have found 1(!) rod that showed signs of a possible crack.
Over the past 30 years I've rebuilt around 150 twin and triple cranks, a good 90% were re-fitted with stock rods. So far, only one of my cranks has returned for servicing, worn out after a further 200000km. A couple have crossed my path since they were fitted, rarely any high mileages, no issues to be found.
piet
Thomas aus LAU
Hero member
From my point of view, this competent and meaningful amount of knowledge suggests, that the cause of the connecting rod cracks is not a long-term permanent crack. This is also supported by the fact that freshly and correctly made engines were also affected.
It must be a sudden, excessive load, that causes the tear.
Thomas aus LAU
chrisk
Hero member
- Location
- Brisbane, Australia
I’m not a mechanic, but I blame harmonics.
A bass guitar player will tell you that at mid F# - D the volume a the string is louder than all other notes played within the scale. Due to harmonics, it allows the string to vibrate violently in comparison to other notes, hence the louder sound.
This mid range harmonic could be considered in rpm, hence a tendency for mid range rev Conrod failures. Further explaining why the middle rod on triples is the most vulnerable.
Perhaps this harmonic issue could be due to crank balance factors?
But what would I know, I’m not a mechanic…..
A bass guitar player will tell you that at mid F# - D the volume a the string is louder than all other notes played within the scale. Due to harmonics, it allows the string to vibrate violently in comparison to other notes, hence the louder sound.
This mid range harmonic could be considered in rpm, hence a tendency for mid range rev Conrod failures. Further explaining why the middle rod on triples is the most vulnerable.
Perhaps this harmonic issue could be due to crank balance factors?
But what would I know, I’m not a mechanic…..
Dellortoman
Hero member
- Location
- Tasmania, Australia
Tacoma Narrows suspension bridge. A required study in any engineering course, as well as the Westgate Bridge collapse. There are plenty of huge engineering failures to learn from. Makes our conrods seem trivial in comparison.
The Westgate story I remember was it was a Box Frame design and it didn't meet in the middle so they loaded it to meet and overdid that loading. That story was from 1980 and 1st year of The Building Certificate Course I did. Was that accurate Cam. I know a bunch of blokes rode it down when it collapsed and a lot were killed. I remember seeing on The News when I was a kid.