Rotax 582 Big End Check

[JimG]

Does anyone know of a con rod bearing clearance measuring device similar to the "cyclone conrod bearing clearance checker" being sold in australia.

 

Or perhaps someone makes one locally.?

 

Thanks

 

JimG

 

 

[facthunter]

Conrod clearance indicator.

 

The clearance at the bearing is not a good indicator of the bearing being likely to fail, other that If it has a fair amount you would consider rejecting it. Roller bearings fail by surface fatigue, (pitting) or cage failure. Save your money. Nev.

 

 

[Guest kermet]

Make one

 

Hi JimG,

 

try make one yourself.....very easy,this way works with two plug heads only

 

drill out a spark plug that fits your motor to the size of you DTI shaft (dial test indicator )

 

for a 582 motor think you need a 15 mm extension for DTI to touch the piston at TDC

 

get a rubber bung and approx 50cc syringe from the pharmacy etc

 

drill bung if no hole already and fit tube through it and onto syringe to screw into one plug hole

 

fit DTI and modded spark plug into other hole being careful and rock motor until TDC is found,

 

Suck syringe in and out to get reading, (Not violent)

 

Better instruction are on the net but its simple to do and gives some piece of mind that you can do internal checks from outside and an idea of condition

 

these were the clearance's i had been given but i see on this site they are more cautious

 

.03 new

 

.05 run in and good order

 

.08 slight wear

 

.10 ok but needs checking every 10 hrs Max.

 

.15 check every flight,call bank manger

 

etc

 

Checking con rod bearing wear

 

Cheers

 

Brett

 

 

[facthunter]

Bearing clearance.

 

Since there is a safety aspect to this I make further comment. The method you describe, and most others would not give the big end clearance but the sum of the big end and small end clearances. The clearances that you list are excessive even so, and if used would give a false sense of security. ie. a high hours engine could easily give a good reading on these figures and fail less than one hour later.

 

Roller bearings do not need running in. They do not wear in the normal sense unless there is a lot of dust around. Refer to my previous post.

 

Rotax in their wisdom, life the crank at 300 hours. If they could substantiate a higher figure, I am sure that they would as they would sell more motors. Many individual motors have done much more time than that, but the failure rate over 600 hours (to take a figure) becomes significant, so I would suggest you don't go there unless the country you fly over is good for landing on. Nev

 

 

[Yenn]

Are those figures lnches or mm?

 

 

[facthunter]

Inches or MM?

 

That would make a difference, but they are still misleading (in my view and I have built plenty of them).. Nev.

 

 

[Guest kermet]

Haha like that.... But the link i posted shows mm same as my instruction sheet i received.

 

here it is again

 

Checking con rod bearing wear

 

 

[facthunter]

More..

 

The critical statement comes at the last image. Ie The wear will increase rapidly .... The trouble with this is that when the play does increase rapidly it is not caused by wear in the normal sense but is caused by the hard surface flaking off the crankpin. These hard particles end up through the motor embedding in the piston and scoring the cylinder . They can cause the cage to fail and the big-end will go blue and the conrod may fail dramatically., either by breakage or seizure. You should cease operating the engine long before this is likely to occur, as once the process starts the failure may be as short a time as 10 minutes. Nev..

 

 

[Guest Crezzi]

Interestingly that link quotes a maximum play of 0.08 mm (for a 503). In my limited experience once its run in, the value basically doesn't change throughout most of the engine life.

 

Once it does start increasing its likely to expire pretty soon (Quite possibly within less than the 10 hour check period mentioned previously).

 

Cheers

 

John

 

PS Nev beat me to it & with a much more comprehensive answer !

 

 

[Guest kermet]

Yes i agree....as soon as there was any wear change measured i would be careful