Component manufacture and physical properties

Connecting rods :

Pistons :

Crankshafts :

acotrel said:

Connecting rods :

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acotrel said:

Connecting rods :

Click to expand...

lets start here.
Titanium rods, two main types, forged or machined from Billet.
Forged as Forged is better for almost everything, as far as performance and weight. It almost always cost more.
There are many manufactures as well, so design as well as how that are made, what bolts are used.
We have used Jet Forged rods, as well as Pankl, and machined rods from a number of makers.
With the pankl rods the design questions start with:
Bore and stroke
CC per cylinder
Red line
Over rev RPM (RPM over redline)
And finally how long do you want them to last?

This was interesting, we used to go with 30 hours, never had one fail.
They made rods for F1 when they were using different motors for qualifying, these were designed to last 15 minutes.
The shorter the life span the lighter the rod.

They used to make the Rods for all the F1 car teams other than McLaren, who made their own. I do not know if that is still the case
OEM rods in Ferrari's Street cars.

Ti rods
advantages light weight
Disadvantages, they stretch more than steel, so piston to valve clearances need to be increased, expensive!!, you must use special care with rod bolts as titanium galls to everything

Steel, many many types, some can be designed to be as light as Titanium, using the best steels and hardening processes, stiffer that Ti or alum, less stretch

Aluminum, very light, less expensive to make, stretches more that steel, a small scratch or mark can cause a rod failure

I was involved in making steel gun barrels using material which has 3% nickel, 1% chromium, 0.3% carbon and 0.6% manganese. The biggest problem was in getting steel which was clean enough. Any which has sulphur and phosphorus above 0.005% each, usually has inclusions in it which can help it fail at lower loads. I believe the American steel is vacuum degassed which can make it better. But if you buy steel con-rods, without intervening personally, how do you know what you are getting ?

One of the things which has a big effect on acceleration, is reducing the reciprocating weight of rods and pistons. Tome long rods made of titanium combined with lighter pistons seems to be good.. Your comments about steel rods are interesting. I have been wondering about whether they are made by CNC from flat billet. That would get rid of the inclusions in the middle, which might occur , if they were ever made from bar stock.

Interesting videos, Al. Thanks for posting them.

In terms of specific strength, i.e. tensile strength divided by density, as Dan mentioned, there are high tech steels that can be used to make rods as light as titanium rods with the same strength, but they are pricey, and require more precise heat treatment and aging techniques. Among the modern maraging steels you can find alloys with tensile strengths as high as 500,000 psi, more than twice that of the high strength alloys typically used for high performance rods, like 4340. There was a lot of buzz about making connecting rods from them a couple of decades ago, but I don't know if anyone is mass producing them today. Probably not very cost effective for Nortons.

Ken

I was involved in crack testing vertol pins for helicopters many years ago. which were made from maraging steel. From memory it was extremely important to make sure there were no stress-raisers on the surfaces.
That other steel I mentioned is sold in Australia as Comsteel 4130. It is too dirty to be used for gun barrels, so you would not use it to make connecting rods.. I don't know how anyone would ever be sure they had bought clean steel these days. We no longer have the testing facilities in Australia. You would probably only need to get one fair sized sulphide inclusion to get a failure.

We need to be careful not to confuse tensile strength with hardness. Some people use hardness as a measure of tensile strength, but some materials can be very hard and brittle rather than tough.

And by the same token, some materials can, like Titanium, can be very elastic. It also has a more finite lifespan than some other materials.

lcrken said:

Probably not very cost effective for Nortons.
Ken

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Yeah I’d say so Ken.

New stock design ones from more than one vendor, Thunder Engineering and various other billet alloy offerings, various steel offering inc Don Pender and MAP, Carrillo of course, JS lightweight Carrillo, etc.

The global market for additional super exotic rods must be... approximately... some where around... 3...

Give or take a couple.

The same probably applies to bits for any classic racing motorcycle. But Bruce Verdon is still in business in New Zealand, making TTI gearboxes. Success is all in the mind - if you have a victim's mindset, you will be a victim. One of the things which has almost killed classic motorcycle racing in Australia, has been the negative defeatist mindset. Also the inability to think outside the square. Motorcyclists whom you would think would be tear-aways , are often very conservative.

Where does Andy Molnar buy his con-rods ?

acotrel said:

The same probably applies to bits for any classic racing motorcycle. But Bruce Verdon is still in business in New Zealand, making TTI gearboxes. Success is all in the mind - if you have a victim's mindset, you will be a victim. One of the things which has almost killed classic motorcycle racing in Australia, has been the negative defeatist mindset. Also the inability to think outside the square. Motorcyclists whom you would think would be tear-aways , are often very conservative.

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So, to be clear, you are putting your name down for a pair of new, super exotic rods, at a few thousand $ per pair then Al ??

acotrel said:

Where does Andy Molnar buy his con-rods ?

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All of our Manx engines are enhanced with the ultimate crankshaft assembly, 2kg lighter than standard, manufactured from EN36 forgings, hardened & ground all over, with pressed up 40mm needle roller big end, Carillo Con Rod, lightweight 2 ring Omega piston & nitrided rings.

Carrillo is misspelled.

Bernhard said:

And by the same token, some materials can, like Titanium, can be very elastic. It also has a more finite lifespan than some other materials.

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Elastic!!, the word I should have been using, thanks

The lifespan is part of the design, the longer you want it to last the heavier it will be.

The 1990 thru 2007 Honda NSX all had Ti rods stock, as did the 1988-1992 Honda RC30
Many more cars have it now. including the Corvette in 2006



Some interesting info.

From 2007, so dated https://cdn.ymaws.com/titanium.org/resource/resmgr/ZZ-WCTP2007-VOL2/2007_Vol_2_Pres_121.pdf



I just liked the look of this piston (scroll down) https://pankl.com/en/products/engine-turbosystems/

Fast Eddie said:

So, to be clear, you are putting your name down for a pair of new, super exotic rods, at a few thousand $ per pair then Al ??

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I am thinking that Jim Schmidt's long con-rods and light pistons might be the most sensible way to go. The must be plenty of guys on this forum who race commandos. In the end, the limiting factor must be the crankcases. Even with a high balance factor, high revs probably kills them. The valve gear in a Commando engine should cop 10,000 revs if lightened and a gentler cam profile is used. But not much else in the motor would go there. A lightened crank is not the answer in my opinion - you get more vibes and the motor performs differently. Personally, I think the best stroke would be 75mm.. That is what was used in the Honda RS750D and one model of Triumph Thunderbird.
My problem is that these days I am not usually playing with money, but sometimes money arrives. I usually try to think ahead. It is really funny - what I have already in the Seeley, is enough to do all I need. But with me it has never been about winning - only ever about improving the bike. What my Seeley 850 can do, really surprises me. I have never believed in it - only a two-stroke responds as well to a dose of methanol - low compression ?

Fast Eddie said:

So, to be clear, you are putting your name down for a pair of new, super exotic rods, at a few thousand $ per pair then Al ??

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Nigel, Do you use Jim's rods and pistons and his lightened valve gear in your 920 motor ? To my mind, bigger pistons are a backward step. Quite often a smaller motor revving faster, can be better that a bigger motor revving slower. But with a bigger motor, you usually have more torque, and torque wins races if you can use it properly. A lot depends on the gear box which converts torque into speed. It is no good having a very powerful motor, if you cannot use it to good effect. When building a race bike, the first thing to consider is the gearbox. 5 speeds is enough, but the 4 upper gears need to be close. I only bought the 6 speed box to get into the first two corners faster. What you lose there, is very difficult to regain.

Yes Al, I’ve got JS pistons and rods in the 920, but Maney cam and valve gear in that motor. I used JS rods & pistons along with cam and valvetrain in the 850.

IIRC the JS 920 pistons are same as, or slightly lighter than, stock 750 pistons.