Atomic billet conrods were designed from scratch with one principle in mind - use aerospace quality materials and sophisticated manufacturing processes to produce extremely strong, light and durable connecting rods, at an affordable price.
Why do Ford XR6-T owners need a better rod?
The XR6-Turbo is very popular with performance Ford enthusiasts, however the standard fitment conrods are not designed for greater than stock power levels. When tuned to produce higher than stock boost levels the factory fitted conrods often fail, resulting in disastrous consequences for the engine. Ford have identified the need for a stronger conrod in the XR6-T’s and now fit their LPG rod into the Typhoons. These rods are only marginally stronger than the original conrod and are also failing when subjected to small increases in boost.
Detonation has also been found as one of the main causes of conrod failure. This is due to the cylinder pressure of abnormal combustion producing compressive loads many times greater than the loads of normal combustion, often causing immediate and catastrophic engine failure. Atomic engineers considered these peak loads in our conrod design to ensure longevity under the toughest conditions, designing them to withstand loads of up to 8000 g's.
Photo shows the comparison between the stock conrod (on left) and the Atomic billet rod #306200 on the right.
The design and evaluation process.
The Atomic engineering team set out to address these problems by designing what many performance engine builders are now calling the finest conrod on the market for the XR6-T engine. Extensive CAD/CAM computer modeling was employed to produce a design with a very high stiffness-to-mass ratio. The next step was to pick the correct materials, heat treatment and surface treatment processes to ensure durability under rigorous performance applications.
Next came FEA modeling (Finite element analysis) to simulate stresses on the conrods. This also entailed weighing every piston, gudgeon pin and ring set on the market and loading this information, plus stroke, rotating and reciprocating conrod values into our computer modeling software to calculate the stresses.
The greatest load exerted on a conrod in an engine producing under 600 Kw comes not from the force of normal combustion, but from the tensile force exerted by the piston at top dead centre (TDC). At 5250 RPM the piston exerts a tensile load on the conrod of 1908 g's (-1693 kgs) at split overlap TDC reversal. If you increase maximum engine speed by only 1000 RPM to 6250 RPM, the TDC tensile load rises by 50.4% to 2870 g's. At 7500 RPM the tensile loading increases to 4132 g's, clearly demonstrating the exponential growth in conrod loads generated. It also shows the Atomic conrod has plenty in reserve.
The reciprocating weight of the conrod/piston assembly is particularly crucial to the amount of load placed on conrod bearings at TDC. Our #306200 conrod weigh 630 grams, whereas other conrods on the market weigh 698-710 grams. At only 5750 RPM, an additional 70 grams of static conrod weight adds 118 g's (233.1kg) of additional load to the conrod bearings at TDC. Multiply this by 6 and rev the motor past the 5950RPM factory rev limit and it is easy to see why these engines suffer crankshaft and bearing problems with heavy conrods.
Excessive loads at TDC are brought about by a high reciprocating mass and/or by increasing engine RPM, so it is essential to design reciprocating engine components with the lowest mass possible to minimise premature lower bearing shell bearing failure. This is particularly relevant to our hard core customers who are turning their engines to 7500RPM+
What about the bolts?
Finally, we needed to hold the whole lot together, and the only choice of fastener that exceeded our requirements is supplied by Automotive Racing Products (ARP) in the USA.
 They carried out reciprocating load calculations for us before recommending the use of a 3/8" 12 point 8740 chrome moly capscrew bolt from their range. Just to be sure, Atomic went beyond ARP's recommendation and fitted bolts made from ARP2000 material, which is stronger and more durable than 8740 chrome moly.
Accuracy of machining.
Finally, sophisticated computer controlled manufacturing techniques were combined with good old hand finishing of critical dimensions on Sunnen honing equipment to ensure all tolerances are held to the highest level.
For example, the sizing of the small end of the conrod is held to a tolerance of .0001" (1/10,000 th's of an inch) - to put this very small measurement into context, a human hair is approximately .002" (2 thousands of an inch) thick. Therefore, the tolerance we hold when machining conrods is the equivalent of splitting the hair into 20 slices - the thickness of each sliver of hair equaling the maximum variation in size allowed. 1/20th the thickness of a human hair is a very small amount, indeed!
Then the rods were installed in engines and tested to their limits.....
Atomic conrods are the most technologically advanced conrod on the market - accept no substitutes!
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Atomic Conrods suit Ford 4.0L inline 6 cylinder engine.
The #306200 conrod represents the pinnacle of engineering for conrods used in the popular Ford inline 6 cylinder SOHC and DOHC engine - but don't just take our word for it....ask the many satisfied customers who use Atomic Performance products for durability and peace of mind in mission critical street, strip and speedway applications.
Machined from aerospace alloy steel, heat treated, shot peened, bushed, Sunnen honed to precise tolerances and fitted with ARP 2000 series 12 point bolts, Atomic conrods are rated to 100kw per cylinder and come in matched sets of 6.
Photo at left of broken standard conrod - makes quite a mess of the block, sump, windage tray and some valves!
Unlike some aftermarket conrods, no additional finish machining is required to install them in the engine, nor is any crankcase machining required for clearance. Many a novice engine builder has been caught with undersize big end tunnels or mysterious knocks in the engine due to conrod bolts hitting the sump rail, but not with Atomic conrods!
Comparison between stock Ford conrod on left and Atomic #306200 on right
Atomic #306200 Conrods – set of 6
Critical Dimensions
Centre to centre length: 6.060"
Big end width: .991"
Big end finished diameter: 2.2394"
Small end finished diameter: .8665"
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| Ford XR6T "FatRod" |
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Atomic billet conrods are widely used in XR6-Turbo engines producing up to 600 Kw, (100kw per cylinder) but due to ongoing engine development programs by front running teams, some professional engine builders are now making in excess of 750kw.
As our original H-beam conrod was not designed for this level of power, there was only one thing to do – design a new rod with the capability to work in the 900kw+ (150kw per cylinder) range – hence the Atomic “FatRod” was born.
Atomic #306200 rod (upper) compared to #302601 FatRod (lower) showing increase in beam thickness by 14%. Note the beam struts are 15% wider also.
Machined from billet alloy steel like its little brother, the FatRod underwent a body building program to ensure it could cope with the enormous combustion shock loads associated with 1200HP+ flywheel figures. Its beefy H-beam construction is retained but the minimum cross section has been increased by a whopping 34%. The beam is 13% wider, 14% thicker and the small end of the rod can accommodate a .927” Chev diameter gudgeon pin, if required.
Atomic #302600 rod (upper) compared to #306201 FatRod showing increase in beam width by 13%
A slightly different type of heat treatment was undertaken to increase durability and, as a final step, every rod is cryogenically treated following shot peening to remove any traces of martensite crystalline structure.
Available in semi finished for finishing by experienced machine shops or finished to middle tolerance, Atomic FatRods are the toughest rods on the block!
Please note: Part #306201 FatRods are scheduled for production in May 2006 and will be available in July 2006.
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