Wiped OUT My Mac Crank!!!!??????

[Ron Iaconis]

I have a question for any MAC People.
I have been flying and tesy benching a home made prop.
It weighs almost twice the average prop for a MAC.
I have a prop that weighs between 5 and 6 pounds,,,,that flew well.
For some time I had a prop that weighed almost twice that weight,,,at almost 10 pounds!
I got the weight down to about 8 pounds,,,,
My result is that I never had any CHT over 425 Degrees nor EGT over 1200 Degrees,,,,,BUT I FRIED MY MUMBER 1 Connecting rod Bottom END!!!!!
It was totally cooked...The E-Rod rollers were totally destroyed,,,,I had no indication that anything was wrong untill it was too late. The engine when I returned it to idle,,,,she just quit running,,,,and when I tried to fire her up I heard a grinding noise,,,,That was it ..now I am rebuilding and will reduce my prop weight to closer to the 5-6 pound weight,,,,
ANY THOUGHTS?????????? other that changing to another type of power plant?????????
Thanks

[Harry_S.]

Sorry Ron...no help here at this end.

Way back when I flew the MAC 72, I used the recommended prop.

Would the 90 horse engine make a difference in what you're after?? Same crank I know, but...


Cheers :)

[scottessex]

Put a Rotax 503 and a 52" warp drive on it. :)

[Fl90]

Hi Ron, I can only guess at lubrication being the problem on the bearing. I don't think prop weight is that much of an issue with the rod bearing. Sorry to hear your down for a bit.

Scott, didn't the experts tell you that won't work? With the oppinions flying around this forum, you might get chastized.

Phil.

[cwsandrat]

Hey Ron,
I would be inclined to believe that an overloaded crank would cause the nearest main bearing to fail not a con rod bearing. Con rods should only see the load given by it's individual piston. Maybe this is coincidental to your prop experiment.
I have never seen a Mac crank assembly, however I have seen a mess of snowmobile and VW cranks....
Have a better day.

Peace, CW

[scottessex]

Scott, didn't the experts tell you that won't work? With the oppinions flying around this forum, you might get chastized.


Seems that experts also said bumble bee can't fly, Hmmm..

[Ron Iaconis]

I finally figured out what the heck I did to cause my problem.
Upon the complete tear down and in my re-build process, I saw that I used A Rod and used E-Rod bearings!!!!!?????????
I cannot believe that I was so " STUPID " to have done this!!!!!!!
With the E Rods , the bottom of the Rod is Wider with only ,004 In on either side of the journal to the crand sides.
With the A Rods the Steel cage makes up the slop,,,,but I using the E-Rod bearings the cage being not there and the A Rods are cut narrower,,,,having as much as .016 In on either side of the rod,,,,,and the copper washers at the rist pin is not sufficient to keep the rod from harmonics and that in lies my crank to be gaulded.
I still do not know how and why I let this simple but important criteria out of my building process. I bet I am suffering from " Old Timer's Disease" !!!!!!!
Thanks for the ideas,,,,I appreciate yall's input,,,,and maybe someone out there might be helped from my mistakes.

[Harry_S.]

Brain farts occur more frequently with age, Ron. Not to worry.

Last week, I assembled and installed a ceiling fan for a neighbor. A simple operation...right. Wrong.

I can't believe the number or quantity of loose parts to be assembled, plus the instruction sheet would stop (in print) at a critical step and start in on the next sequence of assembly. No wonder they have phone numbers to call...if you have a problem with the assembly of the item. You'd probably be talking to someone in India.

Like when I have a problem with my ISP, I call knowing I will be talking to someone in India. With their accent, fast rate of speech and high pitched voice...it's a lost cause with me and my bad hearing.:(


Cheers :)

[Rick Whittridge]

I finally figured out what the heck I did to cause my problem.
Upon the complete tear down and in my re-build process, I saw that I used A Rod and used E-Rod bearings!!!!!?????????
I cannot believe that I was so " STUPID " to have done this!!!!!!!
With the E Rods , the bottom of the Rod is Wider with only ,004 In on either side of the journal to the crand sides.
With the A Rods the Steel cage makes up the slop,,,,but I using the E-Rod bearings the cage being not there and the A Rods are cut narrower,,,,having as much as .016 In on either side of the rod,,,,,and the copper washers at the rist pin is not sufficient to keep the rod from harmonics and that in lies my crank to be gaulded.
I still do not know how and why I let this simple but important criteria out of my building process. I bet I am suffering from " Old Timer's Disease" !!!!!!!
Thanks for the ideas,,,,I appreciate yall's input,,,,and maybe someone out there might be helped from my mistakes.

Ron, I have used A RODS(wider at crank journal) with E BEARINGS(long cageless) in my motors with great success. I think you have rods mixed up!
The A Rod was used first in the engines & where copper plated. A Rods are wide at the crank journal & centered on the crank by the rod inself. The A ROD has two caged needle bearings pressed into the wristpin end of the rod. There are NO brass washers used on the A ROD as to allow the piston to float in the bore.

The E ROD is narrow at the crank journal & uses long loose E Bearings at the crank. The wristpin end of the E ROD uses one long caged neddle bearing that uses brass washers on each side of the rod to center the rod in the piston. With this E ROD set up the rod follows the piston & is allowed to float on the crank journal.

I hope this helps!

[Ron Iaconis]

Ron, I have used A RODS(wider at crank journal) with E BEARINGS(long cageless) in my motors with great success. I think you have rods mixed up!
The A Rod was used first in the engines & where copper plated. A Rods are wide at the crank journal & centered on the crank by the rod inself. The A ROD has two caged needle bearings pressed into the wristpin end of the rod. There are NO brass washers used on the A ROD as to allow the piston to float in the bore.

The E ROD is narrow at the crank journal & uses long loose E Bearings at the crank. The wristpin end of the E ROD uses one long caged neddle bearing that uses brass washers on each side of the rod to center the rod in the piston. With this E ROD set up the rod follows the piston & is allowed to float on the crank journal.

I hope this helps!
Yes Rick it does help somewhat,,,,
But,,,,I am still not positive in regards to the A Rods/E-Rods.......I thought that I always knew the difference and never would have made a mistake in assembling a Mac Engine,,,,untill I fried my #1 Crank Journal!
Here's what I have in my inventory, Rick.
Two different compositions of E-Rods( One is copper colored,,,and the other is steel in apperance) Both E-Rods have " wavy" bottom ends and are wide enough to allow only .004 in on either side between the rod and the crank side journal. Along with this E-Rod are copper washers to be used at the wrist pin with about .007 in on either side of wrist pin and piston bosse.
Now,,,,I have these " so called" A-Rods that are steel colored, are smooth cut on bottom end and ,,,and are Narrower than the E-Rods ( A-Rod bottom ends have about .016 in on either side of crank journal) Then when I add the " two " piece steel cages, the cages have the .004 in clearance on either side of the crank journal.
RICK,,,,am I confused?????? or is it just that I have very old rods?
My " E-Rods " that I have in my inventory are of two different compositions,,,,One type ( with wavy bottom ends) are copper colored,,,and some are steel colored!
All of my " A- Rods" are steel colored,,,and are straight cut on the bottom ends.
Also, Rick,,,,,at the wrist pin ends,,,,with my " A-Rods" the needle bearings are " Not " as wide as the wrist pin castings. But my " E-Rods " , at the wrist pin castings ,,,,the needle bearings " are wider than the casting of the upper wrist pin castings. NOW all the wrist pin needle bearings are all,,,,,ALL the same width,,,it's just that the castings are of different widths depending on if they are either A-Rods or E-Rods.
Here is what I have installed in my rebuild at the present, Rick.
I have smooth cut steel bottom end Rods , With two piece steel caged bearing assembling ( the rollers at the bottom end are short and flat ended and fit into the steel cages.), and I have at the top,, NO washers( copper washers) No washers,,,,and the piston bosses are not machined out for the acceptance of the copper washers usually done for the E-Rod installations.
Rick,,,,is this an acceptable re-build?
I haven't finished my final assembly yet,,,,I will need to loctite and nut clamp the rod end nuts,
I have machined the " third ring " into all my standard 72 pistons( Bosses "Not" machined for the copper wshers at wrist pin)
I appreciate being able to touch base with you, Rick.
Ron Iaconis

[Rick Whittridge]

Ron, Please reread my post of the desciption of the two rods again.
A rod is wavy at the crank end (Wider) & does not use the washers at the wrist pin.
E rod is narrow at the crank end & uses washers at the wrist pin to center the rod on the crank by the piston.

[Ron Iaconis]

Rick,
I must be very dense!!!!!!!!
But from my understanding from Dave Prater at a forum in Mentone and from years back that the E-Rods are the newer wavy ones and the straight cut A-Rods use the cages ,,,,,,I will check into the R&D Manuals I have I thought that I understood it,,,,but will do more home work,,,,with the parts catalogue and manuals I have on the Mac Engine

[Fl90]

Ron, A rods are wavy and wide. Rollers w/o cages need brass thrust washers.

[Ron Iaconis]

I cannot believe that I have had it wrong for 22 years ,,,,
Any way I had it correctly when my crank got burned,,,,,
I had E Rods( straight cut bottom ends,,,,free rollers and copper washers up top, and my number 1 rod journal crank got fried!!!!!!!!!!
I now have built an engine incorrectly and I will just see how long it takes to tear itself up!!!!!!!!!!!!!!
I used straight cut bottom E Rods,,, with new AX steel caged two piece steel caged brgs. I fired her up to nite and she runs great,,,Let's see how llong till I burn her up!!!!!!!!!!!!! I will try to drill it into my head that A is new,,,,,AX is New NEW is WAVY Rods
E is old and straigh cut needing free rollers and copper washers up top.....
See for some reason I looked at A as old and E as new,,,,,,but they started out with an old rod calling it E and when the NEW improved Rods were manufactured they called them A ????? huh??????
How screwed up can that be?????????

[Rick Whittridge]

I cannot believe that I have had it wrong for 22 years ,,,,
Any way I had it correctly when my crank got burned,,,,,
I had E Rods( straight cut bottom ends,,,,free rollers and copper washers up top, and my number 1 rod journal crank got fried!!!!!!!!!!
I now have built an engine incorrectly and I will just see how long it takes to tear itself up!!!!!!!!!!!!!!
I used straight cut bottom E Rods,,, with new AX steel caged two piece steel caged brgs. I fired her up to nite and she runs great,,,Let's see how llong till I burn her up!!!!!!!!!!!!! I will try to drill it into my head that A is new,,,,,AX is New NEW is WAVY Rods
E is old and straigh cut needing free rollers and copper washers up top.....
See for some reason I looked at A as old and E as new,,,,,,but they started out with an old rod calling it E and when the NEW improved Rods were manufactured they called them A ????? huh??????
How screwed up can that be?????????

Ron, A RODS are the oldest rods (WIDE - WAVY)centers itself on the crank journal. No need for thrust washers.

E RODS are the newer style ( NARROW WITH LOOSE ROLLERS) & must use thrust washers at the piston to center the rod at the crank journal.

[Ron Iaconis]

what I found just yesterday, I was jetting my carb when I noticed that the " Air Cleaner" assembly bracket that holds the bottom piece to the carb,,,,had CRACKED !!!!! And here in I believe is what transpired,,,
The bracket cracked and a piece of chrome plating came off and got into the crank/rod rollers and tore it up. It's just a guess but I cannot see what else would have done this,,,,because my CHT/EGT all were in spec and all of a sudden she went out on me!!!!!!!
I now have a Mac put together with the narrow( E ) rods and the AX caged steel rollers and " NO " Washers on the top wrist pin area,,,,,,,,
What I should do then is take her apart and get the pistons relieved at the bose and put in the copper washers,,,,
Oh Well or I could just run her like she is and wait for her to " blow" !!!!!!
Ron, A RODS are the oldest rods (WIDE - WAVY)centers itself on the crank journal. No need for thrust washers.

E RODS are the newer style ( NARROW WITH LOOSE ROLLERS) & must use thrust washers at the piston to center the rod at the crank journal.