Moss Engineering

33 Kings Lane
South Croxton
Leics. LE7 3RE

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    Scott Long Stroke Cranks

It is not a case of “IF” a long stroke crank will break, only WHEN!

It has been the most significant design flaw in the Scott since 1928 and has been responsible for most of the reputation for being troublesome that the Scott has gathered.

Only in recent times has steel technology developed to the point where an interchangeable crank can be produced that it is virtually unbreakable even under racing conditions.

A typical application of this steel is in critical components of aircraft landing gear, and high performance military aircraft.

Moss Engineering researched and used Titanium for Scott con rods 20 years before Ferrari had them in Mr Schumacher’s Ferrari.

Moss Engineering Researched and first used 300MVAR in 1997 for Scott cranks.

Seven years later the Formula One racing car constructors are starting to use this material in their cars.

If you want to avoid the inevitable crank breakage and with it the attendent crankcase damage, consider the insurance and peace of mind that a pair of high strength cranks will bring.

Please remember that a case that has been damaged in a crank failure must be repaired by welding.

This operation deforms the crankcases, destroying bearing alignment.

The engine, without major expensive surgery, can never be the same again.

If you want to see the Specifications for the 300MVAR Steel used in the Process ... click here

If you want to read the Story of the Development of the Moss Cranks...  Click here


Certificate of origin

This is to certify that between the dates of  1st March 2003 and June 1st 2003, a batch of special high strength crankshafts for Scott long stroke engines was produced.


The total production was limited to 30 sets.  Each crank set carries its own unique number.


This certificate is relevant to set number     


Outline details of crank set.


Description       Set comprises one RH and one LH long stroke crank with matching big end crankpin screws and cap screw type securing bolt.


Design.             Based on standard Shipley crank design,  amended to add thickness and strength where this could be achieved without sacrificing interchangeability.  Exceptions to this principle are

a) provision of an enlarged crankpin with large ground fillet radius.  This requires a matching crankpin bush.

b)  Revised crankpin screw of smaller thread diameter to allow for thicker crankpin wall.  The screw is  manufactured from  the same steel as the cranks and incorporates a driving peg for door mounted ancillaries.  Where this peg is not required, its existence will cause no problems.  If required, it can be removed by grinding.

Material            Manufactured from 300M VAR  Cr-Ni-Mo-V Aircraft quality alloy bar.  Produced by Corus special steels division.

                        This steel is a chromium-nickel-molybdenum alloy similar to 4340, but modified by the addition of vanadium and a higher silicon content.  The silicon acts to displace the 500 degree F temper- embrittlement range to higher temperatures.  The overall alloy content acts to produce higher strength levels without the necessity of increasing the carbon content.  Thus this alloy offers a combination of toughness and ductility at high strength levels.  It is a deep hardening steel with excellent torque properties.  It has high fatigue and creep characteristics and maintains its strength at moderately high temperatures.  The grade used is a consumable electrode vacuum remelted product.  This insures a steel of the highest quality with excellent transverse ductility and toughness at high strength levels.

                        For general information.  When this steel was selected for a previous small batch in 1997, its use was almost entirely confined to critical aerospace applications.  It is noted that during the intervening six years, this steel has been increasingly used in more demanding Formula One applications.


Heat Treatment By Bodycote of Coventry UK.


Heat treatment has been carried out in vacuum furnaces to prevent erosion of the surface of the component.

                        740 +/- 10C for 15 mins

                        870 +/- 10C for 40 mins

                        Gas Fan Quench to below 50C

                        300 +/- 5C for 2 hrs    Air cool

                        300 +/- 5C for 2 Hrs   Air cool

                        Hardness 50 – 53 HRC  to sampling plan based on BS 6001

                        Process in accordance with Rolls Royce PLC RR9000:Sabre Approval No. 1800


(This equates to a tensile strength rating of approx 110TT)


Every effort has been made to ensure that these special crankshafts have been produced to the highest standards of steel technology and workmanship available at this date.


                                                Roger Moss


Availability of crankshafts

Moss high strength crankshafts are expensive to manufacture and we need a batch quantity of twenty sets to be economic at current prices.

We invite any owners who might be interested to purchase a set, when a further batch is manufactured, to add their name and requirements on to our “Register interest” list.  This carries absolutely no obligation to purchase.

When we have interest in more than  20 sets registered, we will contact those interested to establish if they are still interested.  When we have commitment to form a viable batch, we will commence production. © 2003

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