AA 45 crankpin breakage

[Rick Pirrone]

Hi all

Here is a picture of my crank that broke of the pin on the weekend this is the second thing to happen first was the small bearing which also scratched the crank a bit so cleaned it up installed new bearings then broke the crank pin

Just wondering if any one else has had this happen to them and what there thoughts are on the possible cause

also would like to hear everyones post race care maintenance tips

I always flush my engines with after run mix and oil generously before next race day

what is everone else doing to after run their engines ????

Your thoughts would be appreciated

Rick

 

[Baxter Walton]

I have never seen a crank pin break? I have broken PTO's from a K&B 45 only because of the mods. You need to talk with Al I'm sure that he can shed more light on it.

 

[Al Hobbs]

I know of two A/A 45 crankpins that have broken out of 200 engines produced.

There could be some more that I don't know about.

On one the big bearing was not pressed in properly, making the engine not square. The other had a non-stock back door installed, again, making the engine not square.

I've had several crankshafts in several different engine brands, break just behind the threads, at the front of the flywheel. But, I have not broken a crank pin in more than 35 years of racing model boats.

I think the big thing about after run maintenance is flushing the engine properly and filling it with oil before you leave the pond. Some people run a blend of 80% mehtanol and 20 castor at the end of the race day to burn out all of the nitro left in the engine, drive out any water left, and coat the inner parts with oil. To run this mix you must keep the glow driver attached.

Then, at home, I take the engine out of the boat and inspect it. If it needs any further work, I can do it then, before the next race date.

Al Hobbs

 

[Duck899]

Hi all

Here is a picture of my crank that broke of the pin on the weekend this is the second thing to happen first was the small bearing which also scratched the crank a bit so cleaned it up installed new bearings then broke the crank pin

Just wondering if any one else has had this happen to them and what there thoughts are on the possible cause

also would like to hear everyones post race care maintenance tips

I always flush my engines with after run mix and oil generously before next race day

what is everone else doing to after run their engines ????

Your thoughts would be appreciated

Rick

I start the engine when I'm done for the day and pull the fuel line off to let the engine run out of fuel. I then add after run oil (air tool oil) to the carb as I'm spinning the engine with the glow plug still tight and turn it untill oil comes out the exhaust. Only add enough oil so the engine does not hydraulic. I then pull the water line off one nipple and flush the water out with oil in the water jacket and fill the water jacket with oil. This has worked for me for alot of years.

What fuel were you running? I run 65% nitro with 20% total oil in my fuel in the AA45 and never have issues with crank pins or big rod end bushings in any engine.

 

[Joe Warren]

A few picco engine had the same problem The fix was to cut the sides of the rod down to allow the rod float on the crank pin with additional clearence. This is a problem especially if the engine has more crank end play than the rod does.... Fixed the picco crank/rods In the east south east we run collet drives that do not control shaft end play. This allows the prop to put tremendous thrust on the crank thrusting & pushing it forward

 

[Duck899]

Another thing to add..... Before you start running an oil filled engine, pull the plug and flush it out with fuel before you start it. Put a rag over the plug and when the rag is soaked with fuel, turn it over some more with out adding more fuel, re-install the plug and your good to go. This stops any chance of a hydraulic lock which is hard on the crank pin or rod. In all my years of racing their were only a few reasons for crankpin failure; A defect in the engine (lack of radius between crank pin and crank), hydraulic lock (running at full throttle and dumping in the water) or low percentage of oil in the fuel. Usually with low oil content the bushing in the big end of the rod goes out.

 

[Rick Pirrone]

thanks all for your reply

i am running a fuel mix of 50% nitro 15% klotz and 3 % castor and hp 7300 plugs after evey club day i flush with 80% meth and 20% castor while running i dribble trannsmission fluid in carby this i do under low revs and not to get to hot .

when after run is done i pump trannsmission fluid through the entire engine by placing a rag over glow hole then replace the plug and lift boat up so oil gets to the small bearing.

i belive that what post race care im taking is ok but i wanted some other thoughts

i have new bits coming so lets hope this dosent happen again

should i up my oil content or it 18% total ok ??????

cheers rick

 

[Duck899]

thanks all for your reply

i am running a fuel mix of 50% nitro 15% klotz and 3 % castor and hp 7300 plugs after evey club day i flush with 80% meth and 20% castor while running i dribble trannsmission fluid in carby this i do under low revs and not to get to hot .

when after run is done i pump trannsmission fluid through the entire engine by placing a rag over glow hole then replace the plug and lift boat up so oil gets to the small bearing.

i belive that what post race care im taking is ok but i wanted some other thoughts

i have new bits coming so lets hope this dosent happen again

should i up my oil content or it 18% total ok ??????

cheers rick

Hey Rick, How much time did you have on this AA45? I've been running mine for 2 years now in a Mutt sport 40 and it see's double duty running sport 40 and 45 hydro against the riggers. We run 4 heats per class so thats 8 heats per race not counting practice runs. We run 8 races per year. My engine still runs strong but will be due for a bearing change at the end of the season.

 

[WIDEBOY]

Rick

I think you had a drive line problem early with this motor did you not keep throwing blades of propellers and keep driving the boat until the whole strut fell of the back of the boat which that could be one cause of the bearing failure.

The other cause could be the way you try to remove the shaft from the drive collet, by hitting the collet with a screw driver would put stress on the rear bearing.

Just a few thing you left out of the post might help others get a better idea of reasons.

Steve

 

[Ray Sametz]

Rick

I think you had a drive line problem early with this motor did you not keep throwing blades of propellers and keep driving the boat until the whole strut fell of the back of the boat which that could be one cause of the bearing failure.

The other cause could be the way you try to remove the shaft from the drive collet, by hitting the collet with a screw driver would put stress on the rear bearing.

Just a few thing you left out of the post might help others get a better idea of reasons.

Steve

:blink: :blink:

 

[Luca Gray]

I Agree with Steve about the cause with the bearing, but crank pin just to clean brake off,

i think that is another problem that need to be looked at.

cheers Luca

 

[SayMikey]

Rick

I think you had a drive line problem early with this motor did you not keep throwing blades of propellers and keep driving the boat until the whole strut fell of the back of the boat which that could be one cause of the bearing failure.

The other cause could be the way you try to remove the shaft from the drive collet, by hitting the collet with a screw driver would put stress on the rear bearing.

Just a few thing you left out of the post might help others get a better idea of reasons.

Steve

:blink: :blink:

:blink: :blink: :blink: :blink: :blink: Ray you crack me up

 

[Tom Foley]

Bearings need to be put in as a redundant service item just like in full size aircraft ..before they blow up !! i'd rather break a crank than do a piston and sleeve . That's Racing !

 

[Rick Pirrone]

thanks all for your reply

i am running a fuel mix of 50% nitro 15% klotz and 3 % castor and hp 7300 plugs after evey club day i flush with 80% meth and 20% castor while running i dribble trannsmission fluid in carby this i do under low revs and not to get to hot .

when after run is done i pump trannsmission fluid through the entire engine by placing a rag over glow hole then replace the plug and lift boat up so oil gets to the small bearing.

i belive that what post race care im taking is ok but i wanted some other thoughts

i have new bits coming so lets hope this dosent happen again

should i up my oil content or it 18% total ok ??????

cheers rick

Hey Rick, How much time did you have on this AA45? I've been running mine for 2 years now in a Mutt sport 40 and it see's double duty running sport 40 and 45 hydro against the riggers. We run 4 heats per class so thats 8 heats per race not counting practice runs. We run 8 races per year. My engine still runs strong but will be due for a bearing change at the end of the season.

duck

the engine was bought back in may this year

as steve said i had thrown a blade once (this i was told as i was unsure i had ) and for the collet it was a pain to let go of flex shat but is now in the bin

knocking on the collet i now know this is not good for bearings

but my reason for this post was to see if anyone else has had this type of breakage and to seek there thoughts and reasons

so i can keep a eye on my maintenance path

main thing is i dont want this to happen again

some say bearings have lasted 2 years others say they change them every six months i use my boat pretty much twice a month so im assuming i will need to check them and change them more offten than not :unsure:

thanks for your thoughts

cheers rick

 

[wayne middlemiss]

hi rick i would consider using a bit more castor oil and less klotz but still 18% oil content to somthing like 10% castor 8% klotz just to make sure its feeding oil evey where, klotz on higher percentil than castor in my opinion wont give you the proper lubrication at rpm .

 

[Tim_Duggan]

Any chance of a close up pic of the point where it failed? might give a clue.

 

[Duck899]

Any chance of a close up pic of the point where it failed? might give a clue.

I see what looks to be a heat mark (brown copper) on the crank pin which means to me some lean runs. It would also be interesting to see what the bushing in the big end of the rod looks like....

 

[WIDEBOY]

The metalurgy in the AA 45 is far superior to any CMB or Picco engine. The tolerances in the fit of the AA are also better which means the performance of the AA will last longer than the CMB or Picco. Not only that, when you buy an AA engine you are helping to support one of our own boaters. The AA45 just so happens to be a powerhouse as well with great parts availability and support from Al Hobbs.

Hows that metalurgy workin out for you now

I think both the Picco and the CMB Vac are better

and the Nova Rossi is another level again

Rick your maintenace routine is just fine as is the fuel

i think you got a bad Motor

Greg

Greg

How do you figure that out when you know how many Picco crankshafts have broken.

CMB i can not comment on.

So if the AA was a bad motor what was so bad about it i am very interested in your comment.

Because of your comment on the Novarossi domination at the 1st Race meeting i think that this Boat motor combination of Ricks won B hydro correct me if i am wrong but to finish first you must first finish.

Steve

 

[Rick Pirrone]

Any chance of a close up pic of the point where it failed? might give a clue.

I see what looks to be a heat mark (brown copper) on the crank pin which means to me some lean runs. It would also be interesting to see what the bushing in the big end of the rod looks like....

 

[camaroboy383]

hard to tell with the pic zoomed in,,,but to me it looks as though that pin had cracked around where the radius is to the wieght,,,then slowly wobbled its way off..if you look at the outside edges of the pin and were it was on the wieght,,,it looks shiny,,as if it was scrubbing for a while before it popped....hence the wobble i stated....

ac