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- Oct 19, 2005
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hobot's view is -after the Z-plates Norton rods are the toughest Al item and something else must let go first.
I hold there is no fatigue factor until pressing beyond their design doubling or more the loads by piston size/mass and rpm. Then better change em out every so often or buy steel ones. So which is worse on a rod the rpm jerk tension or the combustion shock compression? ================================
Dances with Shrapnel>>
The manufacture of the 1,007cc engine components, Steve Maney, strongly advised against (basically said "don't do it") using aliminum rods. He has broken enough and/or seen enough broken that he now uses steel rods only in the 1,007cc engines when they start tipping 95 RWHP. They race them with steel rods and break them with aluminum rods; sounds like aluminum rods in this application is the weak link. Pistons have not been a problem....Hmmm, must be a different plane or universe we are talking about here. Please do not take my word for it
As an added note, Dave Nourish at one time supplied his engines with aluminum rods but no longer does for some strange reason....hmmmm; makes me think.
I suggest someone start a new thread on the merits of aluminum rods in a Norton if the thread does not already exist or if there is any interest. I understand what you are saying there Steve but from where I stand it looks a bit out of context. Yes, Norton rods have proven fairly durable and reliable in many Norton race applications but let's face it, a 1,007cc Norton engine is really a whole different league. We should then be discussing Norton aluminum rods in a 600 Cubic Inch Donavan race engine; different things start to happen. As for nitro and drag racing I think several on the list have missed the mark on the primary reason for alloy rods - resistance to buckling, but that's a different thread all together.
SeeleyWeslake » Wed Feb 15, 2012 10:14 pm
As an added note, Dave Nourish at one time supplied his engines with aluminum rods but no longer does for some strange reason....hmmmm; makes me think.
As mentioned above I'm not quite sure why conrods are getting a bunch of press in a headflow post but here goes anyway.
I discussed conrods with Dave Nourish since I've run one of his 750s for quite a while. The only reason he stopped using/making his own aluminum rods was because he couldn't get the rod bolts any more. His comment was that he preferred to use the aluminium rods since the little end was generally lighter than the steel ones, even if the overall weight wasn't much different. My conversation with him was sparked by the broken rod shown in the picture. Its out of a 750 engine (70 -75 ish rwhp and a fair bit of detonation ) and it broke after 6 seasons. When asked, Dave said that yes aluminium rods do fatique after a while and he recommended changing them at regular intervals. What that interval was he couldn't really say. I figured that if mine lasted 6 years then I'd change them every 3 to be on the safe side. Given that he used the same rods in his 950 cc 95 hp engines the strength of the rod wasn't really an issue - rather it was just its fatique life. I carried on using the aluminum rods, changing them out evry 2 -3 years until he stopped making them and I switched to Carillos . The 2 rods on the left are slightly different versions of the ones he supplied, the Carillo on the right is out of a shortstroke engine that had a seizure after the oil feed line broke and damaged the little end bush ( and the piston and the bore)
Its a while since I've looked at a standard Norton rod But i believe the Nourish ones are herkier. Hence I'd believe Steve Maney when he says its not a good idea to use Norton alu rods in his 1007s but I would think a suitably sized alu rod would work just fine (but with the understanding that it would have a limited life)
Nourish makes a range of engines sizes from 500 to 950, all using the same components. An intersting question for the maths whizzes out there would be which rod sees more relative stress, the one in the 500c 60 hp shortstroke engine turning 10,000 rpm or the one in the 950cc 95 hp longstoke turning 7000rpm. Strokes are 58.75mm and 93.5 resp
SeeleyWeslake
==============================================
10,000 rpm x 2.13" stroke = Piston Acceleration 115,327 Ft./Sec^2 = 3,584 x's Acceleration of gravity
7000 rpm x 3.68" stoke = Piston Acceleration 108,736 Ft./Sec^2 = 3,379 x's Acceleration of gravity
Need piston or reciprocation mass to calc the poundage load spikes on the rods.
Main reason Al rods used in the world badest dragsters is their dampening of shocks on drive train d/t better elastic deformation than steel. ie: Al is springier than steel but fatigue fractures out faster too.
From another forum cut down to fit:
Yamaha Warrior Stroke=113mm or .370735 feet, at 5000 rpm there is 1012.43. g's on rod, so its 400 gram pistons 'weigh' 892.79 lbs!
I hold there is no fatigue factor until pressing beyond their design doubling or more the loads by piston size/mass and rpm. Then better change em out every so often or buy steel ones. So which is worse on a rod the rpm jerk tension or the combustion shock compression? ================================
Dances with Shrapnel>>
The manufacture of the 1,007cc engine components, Steve Maney, strongly advised against (basically said "don't do it") using aliminum rods. He has broken enough and/or seen enough broken that he now uses steel rods only in the 1,007cc engines when they start tipping 95 RWHP. They race them with steel rods and break them with aluminum rods; sounds like aluminum rods in this application is the weak link. Pistons have not been a problem....Hmmm, must be a different plane or universe we are talking about here. Please do not take my word for it
As an added note, Dave Nourish at one time supplied his engines with aluminum rods but no longer does for some strange reason....hmmmm; makes me think.I suggest someone start a new thread on the merits of aluminum rods in a Norton if the thread does not already exist or if there is any interest. I understand what you are saying there Steve but from where I stand it looks a bit out of context. Yes, Norton rods have proven fairly durable and reliable in many Norton race applications but let's face it, a 1,007cc Norton engine is really a whole different league. We should then be discussing Norton aluminum rods in a 600 Cubic Inch Donavan race engine; different things start to happen. As for nitro and drag racing I think several on the list have missed the mark on the primary reason for alloy rods - resistance to buckling, but that's a different thread all together.
SeeleyWeslake » Wed Feb 15, 2012 10:14 pm
As an added note, Dave Nourish at one time supplied his engines with aluminum rods but no longer does for some strange reason....hmmmm; makes me think.
As mentioned above I'm not quite sure why conrods are getting a bunch of press in a headflow post but here goes anyway.
I discussed conrods with Dave Nourish since I've run one of his 750s for quite a while. The only reason he stopped using/making his own aluminum rods was because he couldn't get the rod bolts any more. His comment was that he preferred to use the aluminium rods since the little end was generally lighter than the steel ones, even if the overall weight wasn't much different. My conversation with him was sparked by the broken rod shown in the picture. Its out of a 750 engine (70 -75 ish rwhp and a fair bit of detonation ) and it broke after 6 seasons. When asked, Dave said that yes aluminium rods do fatique after a while and he recommended changing them at regular intervals. What that interval was he couldn't really say. I figured that if mine lasted 6 years then I'd change them every 3 to be on the safe side. Given that he used the same rods in his 950 cc 95 hp engines the strength of the rod wasn't really an issue - rather it was just its fatique life. I carried on using the aluminum rods, changing them out evry 2 -3 years until he stopped making them and I switched to Carillos . The 2 rods on the left are slightly different versions of the ones he supplied, the Carillo on the right is out of a shortstroke engine that had a seizure after the oil feed line broke and damaged the little end bush ( and the piston and the bore)
Its a while since I've looked at a standard Norton rod But i believe the Nourish ones are herkier. Hence I'd believe Steve Maney when he says its not a good idea to use Norton alu rods in his 1007s but I would think a suitably sized alu rod would work just fine (but with the understanding that it would have a limited life)
Nourish makes a range of engines sizes from 500 to 950, all using the same components. An intersting question for the maths whizzes out there would be which rod sees more relative stress, the one in the 500c 60 hp shortstroke engine turning 10,000 rpm or the one in the 950cc 95 hp longstoke turning 7000rpm. Strokes are 58.75mm and 93.5 resp
SeeleyWeslake
==============================================
10,000 rpm x 2.13" stroke = Piston Acceleration 115,327 Ft./Sec^2 = 3,584 x's Acceleration of gravity
7000 rpm x 3.68" stoke = Piston Acceleration 108,736 Ft./Sec^2 = 3,379 x's Acceleration of gravity
Need piston or reciprocation mass to calc the poundage load spikes on the rods.
Main reason Al rods used in the world badest dragsters is their dampening of shocks on drive train d/t better elastic deformation than steel. ie: Al is springier than steel but fatigue fractures out faster too.
From another forum cut down to fit:
Yamaha Warrior Stroke=113mm or .370735 feet, at 5000 rpm there is 1012.43. g's on rod, so its 400 gram pistons 'weigh' 892.79 lbs!
