The conrod saga

[welleyes]

We have been silent for some time sorting out the broken engine. We have now reached the point where we need a set of rods. We had braced ourselves to get a set of alloy rods made when another almost complete engine became available. Sadly that had three pristine rods and one with a ding in it which we would prefer not to use. The other spare rods we had previously are neither use nor ornament as they all seem to have been kicked around a garage floor! The three intact rods out of the broken engine were not much better. I realise that alloy rods are easily marked but the state of all the rods I have now seen (with exception of the three very good ones) is awful. I have never marked or damaged a rod in  my life; who has worked on these engines, I wonder?

I know it is very unlikely, but if anyone has one unmarked rod sitting on a shelf.... ! The alternative is a set of new rods and we will have to eat bread and dripping for a couple of years.

Stuart

[simonandjuliet]

Might be able to help, will have a look in the morning.

[davidwheeler]

When I tool my engine to serdi, they said "throw the alloy rods away they are too old and will break".  They made a lovely set of steel ones to take thinwall bearings but they are 200g more than the alloys so off to vibration Free!   Cost a grand but rather bread and dripping than a broken rod.

[ben]

This is one of the rods David was told to throw away. He threw it in my direction!

I would not have thought twice about using it again before all the scary stories about inevitable fatigue failures surfaced recently.

Let me know if you want to take a closer look.

[welleyes]

Thanks, Ben! And everyone else.
I think that my brother Andy has decided to bite the bullet and pay for new alloy rods. The rough quote is high enough but not as high as we feared. The blown-up engine had high compression pistons, origin unknown, but I suppose that Cavallito's standard ones are the only available.We had been hoping to get it back in time to drive to Prescott as spectators at the summer meeting. We may have to wait a bit longer and drive it to the MTWC AGM in Malvern. As that is at the Morgan factory this year, at least it will have its front suspension in fitting company.
Stuart 

[DavidLaver]

With steel rods we also have the scary stories of Augusta and Lambda crank breakages, one theory being the "vibration free" method of balancing.

I really like the idea of new alloy rods - or as a second best talking one of the usual steel rod manufactures to make something down to a weight and tell us what that means in terms of a rev limit.

David

[chugga boom]

With steel rods we also have the scary stories of Augusta and Lambda crank breakages, one theory being the "vibration free" method of balancing.

I really like the idea of new alloy rods - or as a second best talking one of the usual steel rod manufactures to make something down to a weight and tell us what that means in terms of a rev limit.

David

David you have basically said exactly what I was thinking about cranks 

[BlueSky]

Stuart you might be interested in looking at this company doing the Ardennes restoration, the engine section (in French) is here http://retro-meca.com/restaurations/Lancia%20ardennes/moteur.htm

They have reused the alloy rods and found some Mitsubishi bearings to fit. Noticed the have new pistons but cannot see where they came from.

I was recently forwarded copies of these two Lancia England documents, that had originally come from Gerald Batt, on tolerances for rebuilding Aprilia engines, very handy information. The question is are there any more factory sheets like this around?
Noel

[welleyes]

Thanks again. A couple of questions, though. What is the problem with “vibration free” balancing? Or is the problem the steel rods? It has already been suggested to us by non-Lancia people that steel rods with the original crank may not be a good idea because the steel ones are too stiff and unforgiving. (I suspect that was an expert’s attempt to explain to a layman.) Are the factory sheets available? If they are, wider access would be very useful.

Stuart (also per pro Andy) Tallack

[DavidLaver]

One concern some have (jump in please anyone with more information) with the "vibration free method" is that the correction weight is applied or removed at the ends of the crank on the flywheel and front pulley. The thought is this (insert Have I Got News For You style "allegedly") sets up a twisting vibration or resonance in the crank which may have been the cause of a couple of crank failures. 

They put the engine as a unit on a rig much like at the tyre fitters.  Perhaps think of it as making each end vibrate to counter the internal vibrations so it doesn't jump about on its mountings so much.  Money no object people have a modern style counterbalanced crank made to match the rod and piston combo.

Recent problems might also have been machining of the crank beyond limits, or stress raisers, or going beyond rev limits either on a "motorway" basis or through the gears or with missed changes or too much blipping with no load on it or any one or more other causes.  In one case hanging a supercharger off the front with its pulsing load could have been a factor along side the increased torque it produced.

Perhaps its as simple as a smooth engine with steel rods gets (relatively) thrashed.  Back in the day a week flat out round a banked track day and night to setup records would be considered an extreme test. Now we have the roads to pound along beyond the design limits as a matter of course.

David

[welleyes]

Another question!
My brother has bitten the bullet and will have new alloy rods made by Thunder Engineering. They will be used with the Series 1 crank from the "new" engine and with its Martlet pistons which had been bought by a previous owner and never fitted. Now for the question: what shell bearings have other people used? Preferably something modern enough or common enough to be obtainable and replaceable.

As always, thanks to everybody for their patient help.

Stuart Tallack

[simonandjuliet]

My engine has Giulietta bigends and looking again at some correspondence from Norman Wilson, he had done the same - using 1st Series rods and a 45mm crank

I have attached a copy of the correspondence and hope it is readable !

The only question is "are they still available" ?

[DavidLaver]

A plug for Thunder Engineering:

http://www.thunderengineering.co.uk/_id_03_Examples_1052_21798_1051.html

[DavidLaver]

A racer says 50 hours, on the road a happy customer at 15,000 miles.  Some discussion on fatigue against load.

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=336127

http://nortonownersclub.org/noc-chat/technical2-heavy-twins-forum/638075052

[welleyes]

i am confused by Norman Wilson's note. I thought the S1 was 45mm and the S2 was 43.5mm. Am I just getting increasingly muddled?

Stuart