Aluminum bushed rods

[Joe Wiebelhaus]

Didnt want to hijack the 45 VAC thread, so let me ask this,in a racing or testing session, I and we have all broken aluminum bushed rods, anyone ever figure out why sometimes (bottom of the rod) the bottom breaks out, or the top half of the bottom, or like today, split right up the middle ?

Then of course we have the top of the rod, wrist pin lack of lube, over temp, or snap clean off below the wrist pin.

So yes lubrication in number one, also fuel, cooling, low oil content or over reving, but more interested in the location of the break.

Any thoughts ? (yes Joe W, I know your answer, 45VAC)

I have plenty of pics of each break, steel rods too..

 

[Andy Greene]

Here's the last one I broke, granted it was in a kaboom

 

[ALLAN YUEN]

Here's the last one I broke, granted it was in a kaboom

you did pull out cap from beer

 

[Andy Greene]

Yeah, the gap may have grown a tick from that Allan, works perfect

 

[Ray Sametz]

Joe, on some that I have broken the bushing rotated, misaligning the oil holes, cutting off the oil flow. B)

 

[glenng]

Same here, Not a lack of oil in the fuel. Perhaps too lean on the lo end needle and over-rev. Just my theory- Alum and Bronze expand faster than steel and may grip the bushing and spin it. All steel should expand and contract at the same rate.

 

[Terry Keeley]

I started pinning the bushing on alum rods about 20 years ago, except for this Nova I never broke another...

(Believe it had a flaw)

 

[Joe Warren]

Didnt want to hijack the 45 VAC thread, so let me ask this,in a racing or testing session, I and we have all broken aluminum bushed rods, anyone ever figure out why sometimes (bottom of the rod) the bottom breaks out, or the top half of the bottom, or like today, split right up the middle ?

Then of course we have the top of the rod, wrist pin lack of lube, over temp, or snap clean off below the wrist pin.

So yes lubrication in number one, also fuel, cooling, low oil content or over reving, but more interested in the location of the break.

Any thoughts ? (yes Joe W, I know your answer, 45VAC)

I have plenty of pics of each break, steel rods too..

Joe I have raced Alum rod brass bushing motors for years. Many problems are Crankshaft alignment problems or clearence issues. You must maintain Correct crankshaft end play. If the engine is able to increase the crank end play alignment issues will cause a failure. Most engines do not have extra clearence if the crankshaft is shoved forward to backwards excessively. And consider that we Like the Collet type drive lines. We cannot limit the drive line travel due to the gap we leave for shaft wide up....... Most Square drive set ups do not push on the crankshaft the same as the collet drive line set ups... . So the different drive line types did add to some failures due to thrust loads. Also I might add that the machined radius on the Crank pin does Not need to come into contact with the end of the brass bushing. Recesssing the brass bushing end keeps the crank from biting the bushing and turning it in the bore.

 

[Joe Wiebelhaus]

Ok, 2 good thoughts, crank end play / thrust / square drive vs clamped collet thrust, and pinned bushing in rod.

 

[Joe Warren]

You had Mentioned Burnt needles on needle brg rods. Many times we measure the OD of the Needles and find a aftermarket rod needles from a local supplier. But you MUST remember length of the needle is critical & can effect crankshaft end play. Especially if they are too long and are being thrust loaded into a Drum intake they will run hot and turn blue quickly..

 

[Stuart Barr]

Didnt want to hijack the 45 VAC thread, so let me ask this,in a racing or testing session, I and we have all broken aluminum bushed rods, anyone ever figure out why sometimes (bottom of the rod) the bottom breaks out, or the top half of the bottom, or like today, split right up the middle ?

Then of course we have the top of the rod, wrist pin lack of lube, over temp, or snap clean off below the wrist pin.

So yes lubrication in number one, also fuel, cooling, low oil content or over reving, but more interested in the location of the break.

Any thoughts ? (yes Joe W, I know your answer, 45VAC)

I have plenty of pics of each break, steel rods too..

Joe,

I will be in Charleston after all. I will tell you how to make those live.

Stu

 

[Mike Larson]

Terry please describe the pinning process for us... ie: small dimple with a punch, etc, or what?.. and where... the failures I've experienced were largely due to spun bushings..... Stu... I know youre busy, and I'd ask you share also?... Mike

 

[Terry Keeley]

Terry please describe the pinning process for us... ie: small dimple with a punch, etc, or what?.. and where... the failures I've experienced were largely due to spun bushings..... Stu... I know youre busy, and I'd ask you share also?... Mike

I drill a blind hole on the face that touches the crank about 10 o'clock between the bushing and aluminum with a 1/32" drill. Then press in a piece of 1/32" music wire with green locktite and cut the end off with a cut-of wheel.

Never spun a bushing since doing this sometime in the 80's.

 

[dwilfong]

I have read some on where the oil hole should be also. any thoughts?

David

 

[Terry Keeley]

I have read some on where the oil hole should be also. any thoughts?

David

Since the rod's always under compression (at least that's where all the wear is) I think you should have a hole at 12 o'clock feeding the point of contact.

 

[ChrisCapaldi]

Thanks Terry, Do you drill all the way thru the rod for the music wire? Can you post a picture? What size do you make the oil holes? I've seen some that are very small and always wondered if I should open them up.

Thanks,

Chris

 

[RonShaw]

Didnt want to hijack the 45 VAC thread, so let me ask this,in a racing or testing session, I and we have all broken aluminum bushed rods, anyone ever figure out why sometimes (bottom of the rod) the bottom breaks out, or the top half of the bottom, or like today, split right up the middle ?

Then of course we have the top of the rod, wrist pin lack of lube, over temp, or snap clean off below the wrist pin.

So yes lubrication in number one, also fuel, cooling, low oil content or over reving, but more interested in the location of the break.

Any thoughts ? (yes Joe W, I know your answer, 45VAC)

I have plenty of pics of each break, steel rods too..

Joe,

I will be in Charleston after all. I will tell you how to make those live.

Stu

How about a class Stu? I would be interested in hearing your thoughts on curing this problem as well.

 

[Stuart Barr]

Do what Terry recommends on pinning. I did the same. I also reamed the bushing .003" over the crank pin size. Never broke an aluminum rod again.

Stu

 

[dwilfong]

I have read some on where the oil hole should be also. any thoughts?

David

Since the rod's always under compression (at least that's where all the wear is) I think you should have a hole at 12 o'clock feeding the point of contact.

I have seen some say that the hole should be at the bottom? reason being that this is where the gap is to let the oil in. The hole at the top will let the oil out where it is needed most and reduce the oil in the film.

 

[Joe Warren]

Extra Side clearence is always good on a Alum rod application. Make sure the Steel rides on the Steel and dont sqeeeze the alum rod in between. The rod needs to be able to float on both crank pin and piston pin.. ( the crank drive pin always needs to be longer than the rod is wide on the big end... any pinching in this area the rod will get hot and size out ) I have seen some 1/72 brass screws be used that drill thru the bushing into the bore with loctite to secure the bushing. Tight stock clearences are a big problem when the engine is assembled New and the Rod is already loaded forward on the crank pin and the piston pins. These engines normally dont last long.. Drive line & prop thrust is pushing everything forward and trying to misalign your connecting rod at all times. Especially on collet drive drive lines. Square drive, Drive line boats do offer slip fit into the crank and shaft end play has to be determined a different way.