Uas Exchange Conrods

[rob82]

Just wondering if anybody is running these prepped rods at any sort of decent power 350awkw or above??? From the picture it looks as though they have ground off the piston squirter from the side of the rod. I would have though that this would cause a stress location along the side of the rod. I know its not on the thrust side but while one side is in tension the other is in compression via simple elastic beam thoery.

http://www.nismo.com.au/pricelists/General...s/conrodshd.jpg

Edited February 16, 2006 by rob82

[GTRgeoff]

Rob, the squirter puts oil down the thrust side of the piston. It would be of negligible benefit on the compression side without one on the thrust side as well. I would suggest the tensile effects caused by torque loads would be cancelled by the compressive loads during the ignition stroke unless the big end or gudgeon seized. This would be a fairly simple beam loading exercise using superposition of static loads using a basic shape as the stress is highest at the outer edges.

I understand Racepace Motorsport recommend original rods for most street builds of usable power, and UAS are offering an improvement by linishing the rods smooth to remove surface defects and stress concentrators. I would be concerned that the oil is still going in the right place but John seems to know what he is doing there at UAS.

[carl h]

guy here stateside does a simmilar job cept for much less, good work and he fits arp bolts to the rods to suit.

www.speedshopthagard.com

[proengines]

I've beam polished RB26 rods and removed the squirter boss entirely. The only problem is that the way that the holes are drilled for the squirter, once you remove the boss you have a 2mm or so hole instead of a .5mm or so hole. I just braze the hole up from the bearing bore side before I resize the rod. There is plenty of oil spraying up from the piston cooling squirters and you dont need the extra from the rod squirter. I pulled an engine apart today that I did this to that has done 30,000km since and the piston and bore look like new.

If there is anywhere that a 26 rod will break it is around the oil squirter as there are some pretty sharp edged. The engine i pulled apart has gone over 10,000rpm on missed gear changes and the rods held together well.

Saying all that, why bother fiddling with the standard rods when you can buy a set of eagle rods for $800, they're brand new, stronger, have ARP bolts and a much better design and are lighter.

[GTRgeoff]

Nice to know. Thanks mate

[rob82]

Rob, the squirter puts oil down the thrust side of the piston. It would be of negligible benefit on the compression side without one on the thrust side as well. I would suggest the tensile effects caused by torque loads would be cancelled by the compressive loads during the ignition stroke unless the big end or gudgeon seized. This would be a fairly simple beam loading exercise using superposition of static loads using a basic shape as the stress is highest at the outer edges.

How do they cancel? If you look at relative postion of the rod at 90 ATDC of a ignition stroke the forces aren't directly in line with the centre of gravity so they cant cancel. You right in saying that the stresses at the outer edges will be greatest but I cant see how they would cancel. So if the squirter is on the thrust side then that side of the rod would be under compression for an ignition event. Which is probably ok as crack propagation is more likely to occur if it were under a tensile load.

The only stresses that I could see that would cancel (at some optimal rpm and crank position, maybe a harmonic point) each other would be some of the side load associated with the cranks resistence to rotation and the force of the rotation of mass of the conrod itself about is CG.

I may be wrong. THis is just how I see it.

[Amaru]

I pulled an engine apart today that I did this to that has done 30,000km since and the piston and bore look like new.

http://www.skylinesaustralia.com/forums/in...howtopic=106291 <-- Pictures of the internals of said engine here.

The engine i pulled apart has gone over 10,000rpm on missed gear changes and the rods held together well.

<{POST_SNAPBACK}>

Yeah whoops, my bad... I think this smilie sums up my facial expression at the time it happened

[GTRgeoff]

What we have to consider here is each discreet loading at the highest load condition (90degATDC is near enough):

- the vertical load from the force of the piston which is slightly greater than the piston load (due to Pythagoras) and only acts directly along the axis of the rod (since it is a simple pin joint at each end), and

- the rotational load from the resistance of the big end bearing. This can be simplified to a static load in tesion on the thrust side of the rod and compression on the non-thrust side.

- in the case of simple beam theory we consider the inertial forces and can determine that they have limited effect on the outcome in this phase of rotation so apply a safety factor to calculations then ignore them.

In any engine the active forces have to be greater than resistance forces, else we would not have a working engine. So we can extrapolate from that statement that the friction forces from the rotation in the big end are miniscule compared to the piston thrust. This is also borne out by the fact that the bearings do not disintegrate under heat due to friction.

So through superposition of forces the tensile (negative and miniscule) force on the thrust side of the rod + the compressive piston force (positive and very large) gives a slightly smaller but still large compressive load on that side. Additionally the non thrust side will be a compressive + a compressive so will be slightly larger overall.

I hope that helps you understand.

[GTRgeoff]

Nice work Amaru and thanks for sharing. If I didn't already have a macine shop here in Melbourne that I'm happy with I'd be sending my stuff to Queanbeyan.

[Swiper the Fox]

Our well documented engine is using std prepped rods (not UAS)....and has had 2 birthdays.

[carl h]

im glad to hear the std rods are robust as i plan to use the std ones from my rb20 again with cp pistons but prepped as discussed with arp bolts.

very encouraging to ppl looking for mild builds.

[T04GTR]

i think those in the pic are 6 inch vg30 ones.

if your gona make good power get some aftermarket ones.

although dirt has proved its not really nesesary. just insurance.

stress relieving somthing that is on the edge is a good idea. but im pretty sure arp doesnt make bolts for the 26. only the vg30.

i had to get tomie ones.

people use them but the nut doesnt thread on all the way.(dodgy)

[proengines]

but im pretty sure arp doesnt make bolts for the 26. only the vg30.

i had to get tomie ones.

people use them but the nut doesnt thread on all the way.(dodgy)

<{POST_SNAPBACK}>

VG30DETT bolts are actually slightly longer that the factory RB26 bolts and there is plenty of thread, the regular VG30 bolts are nowhere near the right length, SR20 ones are about 2 threads too short. There is nothing dodgy about using the VG30DETT bolts, we use them regularly.

[Swiper the Fox]

VG30DETT bolts are actually slightly longer that the factory RB26 bolts and there is plenty of thread, the regular VG30 bolts are nowhere near the right length, SR20 ones are about 2 threads too short. There is nothing dodgy about using the VG30DETT bolts, we use them regularly.

<{POST_SNAPBACK}>

We use SR20 bolts....good length. Dont know about being "2 threads" too short ??

Only problem is having 4 bolts left over....but after 3 rebuilds you have a full spare set.

Edited February 19, 2006 by DiRTgarage