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Strengthening Conrods & Treatments

Submitted by john_hall11 on Sat, 20/06/2020
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Nortons - General

Well, I know this has come up before, Connecting Rod durability and that there is polishing and shot-peening and tuftriding  and Nitriding.

One thing I sussed out long ago and I know this is a broad statement, but generally, it seems the Classic Car fraternity have a lot more experience in the engine tuning arena, cylinder head work, Inlet tract, porting, lightening crankshafts and Connecting rod assemblies and strengthening there engine components, compared to Classic Bike circles.

Considering either Shot peening or perhaps Tuftriding the Connection rods to aid in durability, now that I have two sets of rods.

 

 

John

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Submitted by george_farenden on Sat, 20/06/2020

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Don't forget that nearly all classic cars had steel or iron rods which take the treatments you mention. With alloy, providing it was correctly heat treated when made,  polishing is the best thing you can do. The lightest pistons you can get will help too.

As regards to tuning, you have to remember that bikes, by and large, were in a much higher state of tune than the cars of the time. (40-45bhp/litre was normal, whereas most bikes were in the 70-80bhp/litre area)

Regards, George. 

Submitted by john_hall11 on Sat, 20/06/2020

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Yes George, I forgot my Hillman Imp connecting rods are "H" section steel forgings and considered exceptionally strong for such a small engine! output from  Standard 42 bhp 875 cc, Sports 875 cc 55 bhp, my 930 cc engine somewhere in between 60-70 bhp, equating to around Alas or Commando figures and a bit more!

My Japanese bikes are almost impossible to tune, without specialists manufactured components,  Moriwaki, Yoshimura.

I understand that cars have to be more flexible in power output, more torque at lower rev's.max torque for car engines used to 3,000-3,500 rpm on the old bikes it was around 4,000-4.500 rpm.

Nice article here about Hiduminium RR56.

https://b2b.partcommunity.com/community/knowledge/fr/detail/2403/Hiduminium

 

The story how the inventor of Hidumium, made an agreement with Rolls Royce to use the RR designation is interesting, historically speaking

 

John

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Submitted by ashley_cutler on Sat, 20/06/2020

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Today, hardly anyone uses forged aluminium rods. Norton and some race engines in the US seem to be the only ones. As for weight there is no comparison to a forged alloy rod, yes, titanium are light but not as light as aluminium, but they are stronger by a large margin. If an engine let's go with titanium rods, there tends not to be much left to rebuild. 

RR are alloys are very good and still available, but you need to buy a MOQ. 

 

Submitted by john_hall11 on Sat, 20/06/2020

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Cheers Guys, Ashley what's a MOQ?

Here are two sets of Atlas rods, Early and later with Dominator 88/99 rods in the middle of the picture. The Dominator rods are definitely longer and the Big-End eye is smaller, there pattern is similar to Early Atlas rods which were derived from a similar pattern forged pressing.

The Dominator 88 & 99 rods have bushed little Ends. All three have oil-squirt holes.

Neil, the Three Japanese bikes I have are small to medium sized fours,  ZL 400 rated 54 bhp, ZL600 rated 74 ish bhp and a Z650 rated 64 bhp,  the last one being air-cooled and a decade earlier than the ZL's. The ZL's are faster on acceleration and roll on speeds than the equivalent era  GPZ versions, smaller carbs more efficient gas flow! When I say tuning I really mean efficiency and flexibility rather than just balls-out figures. I have some GPX  parts, pistons,  crankshaft, connecting rods to fit in the ZL600 when i rebuild the engine.

With the Dominator, I just want it to be as efficient and flexible as possible and not blow up! I ride fairly hard, but not like an idiot, where applicable; but having been weaned on Geoff Duke from my Father and Uncle's library, as a weaner I  try and ride thoughtfully and smoothly and be as empathetic to my machines as possible, but using all the rev range and so I definitely, don't poodle around like an old-fart!

Of course money comes into it, but I have long ago, got over queuing for the ferry to the Isle of Man surrounded by Exotica and riders, who look like they have just got off the track at Brands hatch.

Still wear my Black leathers too! Even in Summer!

 

John

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Submitted by ashley_cutler on Sun, 21/06/2020

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MOQ is minimum order quantity. 

The rods above are old type, the area above the big end was changed to strengthen it, you can tell by the shape. 

I have managed to forge aluminium 7068 into a small number of con rods, but as yet Smiths metals or Kaiser's in the US are unable to say how to heat treat it. We were only the second company globally to forge it, it took a day of forge time to figure out how to do it, as the previous company to do it would not tell us how to do it. 

Submitted by stan_thomas on Sun, 21/06/2020

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Shot-peening for conrods, nitriding for cranks and camshafts.

The theory of shot-peening is sound but whether it makes any diffetrence is something we have to take on trust. I had some Commando rods shot-peened by a specialist in Birmingham in the 90s. They're still fine but they probably would have been anyway if I'd just left them as polished.

Dave Nourish used to make rods for the Commando - definitely stronger than original and probably many times better than some post-76 rods. I asked him about shot-peening and he said it wasn't worth the trouble. Done right, it can make a good product better but won't "fix" a bad one.

Incidentally, does anyone have any experience with NRE post-Dave Nourish? Is the quality the same?

 

Submitted by stan_thomas on Tue, 23/06/2020

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Sorry to hijack this thread but, to answer my question about NRE, Nourish Engineering, who bought the business from Dave Nourish in 2014, is no more The new company was "dissolved via compulsory strike-off" in December 2018. And there were/are a lot of unhappy people. This link explains some of what went on:

http://www.cmrf.co.uk/smf/index.php/topic,9186.0.html

Looks like the cranks and rods I bought from Dave Nourish in the late '80s are the last I'll ever see.

There is still a website for Nourish Engineering but please do your research before dealing with Chris Bushell.

Dave Nourish has nothing whatsoever to do with this and it's a great shame his legacy has been tarnished..

 



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