Billet Crankshaft

I didn't read all the pages in this post so if this has been covered, I apologize.

MAP Cycle got me 2 billet cranks, a standard of the '72 Commando I built and a 75 degree throw for a '79 T140. They are located in St. Peters Florida and sometimes have them or may still get Falicon to make them, not sure, but worth a call?

Best.
 
On the recommendation of Ro-Dy, I contacted Moldex. They are able to offer a one piece billet crankshaft - at a price.
Lead time is 16 weeks.

- Knut
 
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Back in the day, Moldex are the ones who made one-piece Norton crankshafts for Ron Wood's race bikes., at least for his 80.4 mm 750 short stroke. I'm not sure if Ron also had any made for the standard 89 mm stroke 750. They were very high quality. Before having the Moldex cranks made, Ron's bikes used stock crank halves, with radiused main shaft, steel flywheel, and aerospace fasteners. They were also magnafluxed to check for cracks and shot peened.

Ken
 
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lcrken said:
Back in the day, Moldex are the ones who made one-piece Norton crankshafts for Ron Wood's race bikes., at least for his 80.4 mm 750 short stroke. I'm not sure if Ron also had any made for the standard 89 mm stroke 750. They were very high quality.

Ken
Click to expand...
Ken,
Do you know what kind of surface treatment Ron Wood specified, nitriding (diffusion of nitrogen into the surface) or tuftriding (salt bath nitrocarburise)? Tuftriding provides less finishing work. Each treatment has their pros and cons.

Nitriding

Advantages & Properties​

* The process is conducted in gas (490 - 560 °C) or plasma (400 - 590 °C) for treatment times ranging up to 90 hours.
* Nitriding imparts a high surface hardness which promotes high resistance to wear, scuffing, galling and seizure.
* Fatigue strength is increased mainly by the development of surface compressive stresses.
* Hot hardness and resistance to tempering are improved and corrosion resistance is moderately enhanced.
* The low processing temperature and subsequent slow cooling help minimise distortion.
* Nitriding is most effective when applied to the range of steels containing nitride-forming elements such as chromium, molybdenum, vanadium and aluminum.

Disadvantages and limitations​

  • The process can only be applied effectively to a limited range of appropriate alloy-containing materials.
  • Depending upon process parameters and material, nitrided case depths can range from as little as 0.05mm up to 0.50mm.
  • Surface hardness depends upon process parameters, the material and its original condition. For optimum results, a steel for nitriding should be in the hardened and tempered condition and free from decarburisation. (The tempering temperature should be higher than the nitriding temperature).
  • A fine-turned or ground surface finish is the most suitable for ensuring a satisfactory nitriding response. Pre-nitriding treatments may be required on certain materials subjected to gas nitriding (e.g. acid pickling/vapour blasting of martensitic stainless steels).
  • A stress-relieving treatment ("stabilising") is necessary between the rough and final stages of machining of hardened and tempered high-precision components in order to minimise distortion after nitriding. (The stress-relieving temperature employed should be higher than the nitriding temperature but lower than the tempering temperature).
  • On a hardened and tempered/stress-relieved part, nitriding should produce minimal distortion. However, growth can occur, the amount being a function of the treatment parameters and the material. It is fairly predictable and usually less than 0.05mm on a diameter.

Tuftriding

Advantages & Properties​

  • Gives a very hard (800-1500Hv) wear resistant surface to the metal typically up to a depth of 0.002"(0.05mm) depending upon the material.
  • The surface layer is in compression and so not conducive to crack initiation. This increases fatigue resistance
  • As the process is carried out at 580 °C no phase changes take place as is the case with higher temperature treatments, and so there is little or no dimensional change in the components.
  • When specified with the caustic molten salt quench the surface of the steel becomes very corrosion resistant.
  • The hard wear resistant surface also exhibits self-lubricating & anti-seize properties.

Disadvantages and limitations​

  • The metal must withstand 580 °C. This is particularly important when previously heat treated components that are Tufftrided, as the temperature may lead to softening or distortion.
  • As the process is carried out in molten salt, removing this salt from deep small bore holes or hollow components can be difficult.
  • Care must be taken with thin section components to ensure that the thin sections do not become Tufftrided all the way through & and hence become brittle.
(Source: Wallwork, UK)

- Knut
 
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I wonder about short-stroking Commando engines. I always thought my 850 engine was silly until I actually got it going. I raced a short-stroke four-stroke motor for years. It was fast but not an easy ride. My 850 motor is strong and delivers it's power very smoothly, which means I can ride without anxiety. I just sit there like a blob and operate the controls.
When I first started racing, an old rider told me ' you need a lot of racing miles under your belt, and the bike has to do something for you'. I did not know the truth of that until I raced my Seeley Commando 850.
Some things about Nortons puzzle me. I do not know how they got the featherbed Manx so right, and the Commando motor is also good, but it looks so wrong. - I never thought it would do anything.
I think the close ratio gearbox and high overall gearing is what gets my bike going. On the up-changes, I lose virtually no revs, and the heavy crank creates a surge with it's store of energy. When that crank is spinning high - nothing stops it. When I do an up gear-change, all I do is back off the throttle and stand on the lever. The loss of revs is virtually nil. And coming down is easier.
 
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mdt-son said:
Ken,
Do you know what kind of surface treatment Ron Wood specified, nitriding (diffusion of nitrogen into the surface) or tuftriding (salt bath nitrocarburise)? Tuftriding provides less finishing work. Each treatment has their pros and cons.

Nitriding

Advantages & Properties​

* The process is conducted in gas (490 - 560 °C) or plasma (400 - 590 °C) for treatment times ranging up to 90 hours.
* Nitriding imparts a high surface hardness which promotes high resistance to wear, scuffing, galling and seizure.
* Fatigue strength is increased mainly by the development of surface compressive stresses.
* Hot hardness and resistance to tempering are improved and corrosion resistance is moderately enhanced.
* The low processing temperature and subsequent slow cooling help minimise distortion.
* Nitriding is most effective when applied to the range of steels containing nitride-forming elements such as chromium, molybdenum, vanadium and aluminum.

Disadvantages and limitations​

  • The process can only be applied effectively to a limited range of appropriate alloy-containing materials.
  • Depending upon process parameters and material, nitrided case depths can range from as little as 0.05mm up to 0.50mm.
  • Surface hardness depends upon process parameters, the material and its original condition. For optimum results, a steel for nitriding should be in the hardened and tempered condition and free from decarburisation. (The tempering temperature should be higher than the nitriding temperature).
  • A fine-turned or ground surface finish is the most suitable for ensuring a satisfactory nitriding response. Pre-nitriding treatments may be required on certain materials subjected to gas nitriding (e.g. acid pickling/vapour blasting of martensitic stainless steels).
  • A stress-relieving treatment ("stabilising") is necessary between the rough and final stages of machining of hardened and tempered high-precision components in order to minimise distortion after nitriding. (The stress-relieving temperature employed should be higher than the nitriding temperature but lower than the tempering temperature).
  • On a hardened and tempered/stress-relieved part, nitriding should produce minimal distortion. However, growth can occur, the amount being a function of the treatment parameters and the material. It is fairly predictable and usually less than 0.05mm on a diameter.

Tuftriding

Advantages & Properties​

  • Gives a very hard (800-1500Hv) wear resistant surface to the metal typically up to a depth of 0.002"(0.05mm) depending upon the material.
  • The surface layer is in compression and so not conducive to crack initiation. This increases fatigue resistance
  • As the process is carried out at 580 °C no phase changes take place as is the case with higher temperature treatments, and so there is little or no dimensional change in the components.
  • When specified with the caustic molten salt quench the surface of the steel becomes very corrosion resistant.
  • The hard wear resistant surface also exhibits self-lubricating & anti-seize properties.

Disadvantages and limitations​

  • The metal must withstand 580 °C. This is particularly important when previously heat treated components that are Tufftrided, as the temperature may lead to softening or distortion.
  • As the process is carried out in molten salt, removing this salt from deep small bore holes or hollow components can be difficult.
  • Care must be taken with thin section components to ensure that the thin sections do not become Tufftrided all the way through & and hence become brittle.
(Source: Wallwork, UK)

- Knut
Click to expand...

I only remember seeing one of Ron's Moldex crankshafts at a visit to his shop, and my memory says it did not have the typical black finish that Tuftriding produces, so I would have to assume they were either nitrided, or maybe just hardened and tempered. I would expect they were nitrided, since Moldex crankshafts were pretty high end products at that time, but the only way to know for sure would be to ask Moldex. I talked to them several decades back about making more Norton crankshafts, and they were pretty cooperative about answering questions.

Ken
 
There are two forms of nitriding - one uses salt, the other uses gas. If I was making a billet crank, I would not use bar stock. Failures in steel usually come from high sulphur and phosphorus contents - inclusions. If you do a sulphur print on the end of a bar, it often shows concentration of sulphide inclusions towards the centre of the bar. Nitriding is a surface effect. I had my billet crank nitrided several times to help it's wear resistance after being reground. I eventually hard chromium plated the journals. Then it never lost oil pressure again. It used to run at 10,500 RPM, and it was always losing oil pressure, until I did that.
To be nitrided successfully, the steel needs nickel in it. I think my crank was made from Vibrac. The original was made in England, but they broke that one in Australia and made another. The sidecar guys were using them. Mine was probably brought to Australia, by Baldo Meli - he used to work for the Triumph factory and helped Les Virtue - one of our better sidecar guys.
 
A lot of my life was spent making better steel for use in 105mm gun barrels. Without heat treatment our steel had a tensile strength of 90 tons per square inch. Low temperature impact values were always a problem Sulphur and phosphorus contents need to be below 0.010 % each. The steel was 1% nickel, 3% chromium, 0.2 carbon, 0.6% manganese.
In Australia Comsteel 4130 has that composition, but it is too dirty. You might have the good stuff in the UK
 
I guess some of you have seen that AN took a billet crank they have had made by Arrow to the Stafford show at the weekend. Good news for a lot of people.
 
If that piece of steel comes out of the hole in my crank, I would probably die. But I will probably die before I use the bike in anger again. So the crankshaft modification is probably safe.
 
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