Rod stretch
The rods do flex and stretch in the motor,that is why we have quench but its multiple clerances and parts flexing/streaching that cotribute to it so there is no answer to this question just R&D
Trending Topics
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Don't run it less than .038". There are way too many other factors to look at besides rod material. You have to figure out much your crank deflects, rod expansion, wrist pin deflection, piston deflection, piston rock, etc-etc-etc. You're not going to see it run any better if you run a .030" gasket or a .040" gasket if your compression stays the same. Even then, the little difference in compression equates to a minute gain if any.
Teching In
Joined: Jun 2014
Posts: 23
Likes: 1
The modulus of elasticity of 4340 is roughly the same as any other steel: ~29x10^6psi.
To get an ESTIMATE of your total elongation, it's going to be complicated. You'll need to take into account the cross-section of the rods at every point along its length, then add the stretch of the bolts, any clearance between the piston and rod and pin, then figure the stretch of the piston... There's a good reason why most folks operate based on rule-of-thumb here. Even if you take the time to do a finite element analysis of the entire assembly under max load (7000RPM), it's still just a guess. When you're playing with clearances in the 0.001" range, you don't have much room for error. Making decisions based on the general experience of quality engine builders is your best option.
Happy spinning!
-Mateo
On The Tree
Joined: Jun 2010
Posts: 120
Likes: 2
you simply cant calculate it exactly because the rod it self will also stretch due to its mass alone. also it will not stretch uniformly because it does not have a uniform cross section area.
stretch (strain) = stress x modulus of elasticity
stress = force / area
( the problem now is the rod don't have a uniform area cross section area ) anyway ....
force = mass x acceleration
max acceleration piston (ft/s^2) = ( RPM^2*stroke / 2189) *1.333
( stroke in inch )
if you really want to calculate the stretch you have to model the rod in some finite element program like ANSYS .
stretch (strain) = stress x modulus of elasticity
stress = force / area
( the problem now is the rod don't have a uniform area cross section area ) anyway ....
force = mass x acceleration
max acceleration piston (ft/s^2) = ( RPM^2*stroke / 2189) *1.333
( stroke in inch )
if you really want to calculate the stretch you have to model the rod in some finite element program like ANSYS .
On The Tree
Joined: Jun 2010
Posts: 120
Likes: 2
I made a mistake above stretch = rod length * strain
In my opinion a well designed rod will not stretch more than its elastic limit ( for steel that is about strain=0.002) so
stretch = 0.002 x 6.125 = 0.01225 inch
now there is stretch due expansion ( because of heat ) , I will write about it later.
In my opinion a well designed rod will not stretch more than its elastic limit ( for steel that is about strain=0.002) so
stretch = 0.002 x 6.125 = 0.01225 inch
now there is stretch due expansion ( because of heat ) , I will write about it later.
