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Author Topic: Pinged conrod on counterbalance???  (Read 1248 times)

Offline Paul Taylor

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Pinged conrod on counterbalance???
« on: July 01, 2017, 06:11:51 PM »
Has anyone ran across this before.
I picked up a used LA 46.
Has very good compression. I just wanted to take it apart inspect it and clean it up.
i
Someone has been in it before. There is a B on the conrod ( maybe for back) and it looks like the counterbalance has a "ping" in it to prevent the conrod from coming off cause I can't remove it.
Paul
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Offline Paul Taylor

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Re: Pinged conrod on counterbalance???
« Reply #1 on: July 01, 2017, 06:12:37 PM »



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Paul
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Online Brett Buck

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Re: Pinged conrod on counterbalance???
« Reply #2 on: July 01, 2017, 06:28:19 PM »
   Seems pretty hacky, all that staking is going to do is wear out/groove the bushing. It looks like a file has been used for something, there are a lot of places on the conrod that look dinged up, and it also looks like there is some metallic debris. Not good.

    If it was me. I would push the conrod as far "forward" as I could, and try to burnish or even grind/chip/file the staking on the crank pin so you can get it apart without damaging the conrod. If you force it you will put a big depression across the face of the bronze insert. Once you get it apart, then clean up the staking with a file and then a stone, inspect the conrod for damage, and replace. But that it just me.

   Alternatives include:
     
  • Force the conrod off. If you do, turn it so the groove that gets dug is in the side of the rod bushing, rather than the long axis where there is a lot of load. Then clean up the staking as above, and just see if there is a problem with the conrod wearing out.
  • Just clean out the engine thoroughly with your favorite solvent (IPA, soap/water, fuel, Stoddard solvent, kerosene, whatever) to remove any dirt and metal chips, button it back up, and just use it until the conrod wears out. I doubt that the staking has created a very big hump in the crank surface.

   BTW, I can see no other interpretation than yours, that is, someone did it on purpose.

      Brett
« Last Edit: July 01, 2017, 06:55:16 PM by Brett Buck »

Offline Randy Cuberly

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Re: Pinged conrod on counterbalance???
« Reply #3 on: July 01, 2017, 06:36:22 PM »
Yeah, I think what Brett said is about the only option.  The rod looks distinctly like someone who didn't have a clue about taking an engine apart tried to pull the rod off the crank pin with a pair of pliers.

I think this happens sometimes when disassembling because the rod tends to build up muck on the wrist pin that prevents the rod from sliding all the way to the side at the top and there fore won't come off the crank pin.  Cleaning the wrist pin with lacquer thinner etc with a q-tip then light oil usually gets it off.

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Online Brett Buck

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Re: Pinged conrod on counterbalance???
« Reply #4 on: July 01, 2017, 06:42:24 PM »
Yeah, I think what Brett said is about the only option.  The rod looks distinctly like someone who didn't have a clue about taking an engine apart tried to pull the rod off the crank pin with a pair of pliers.

   Oh, I wonder if someone tried to hold the conrod with vice grips or something similar, and then tried to drive it off by hammering on the crankpin with a hammer and a screwdriver?  I have actually heard of cases like that, so it wouldn't be unprecedented.

   Stuff like that is why I am always on about "local engine experts". Nothing would surprise me at this point.

      Brett

Online Brett Buck

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Re: Pinged conrod on counterbalance???
« Reply #5 on: July 01, 2017, 06:57:47 PM »
Paul, If it ain't broke don't fix it. Flush it out with wd40 and put it back together. Judge it on how it runs.

   It is already "broke",  but that's certainly an alternative. If it was a serious contest engine, you wouldn't want to take the possibility that it goes over the hill in the middle of a contest (which Murphy's law will ensure happens at the worst possible time). It might run for 500 flights this way, though.

      Brett

Offline Al Ferraro

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Re: Pinged conrod on counterbalance???
« Reply #6 on: July 02, 2017, 08:44:50 AM »
  To me it looks like the pin is at 11:00 o'clock and has already worn a grove in the rod bushing. I would wash out the engine real good then use a Qtip with air tool oil and clean out all the black residue inside the case, piston, liner (take the head off), rod, ext. After that run a tank full of fuel on the bench with 4 and 2 stroking the engine a couple of times. Now pull the back plate off the engine and check with a Qtip wet air tool oil and swab on the rod and inside the case. If you get no metal you should be good to go. If you see metal order new parts.
Al

Offline Steve Helmick

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Re: Pinged conrod on counterbalance???
« Reply #7 on: July 02, 2017, 03:26:31 PM »
The divot in the crankpin looks like it could have been made with a center drill, perhaps for turning or grinding the pin OD during manufacturing processes. It would be good to clean all the chips out of said divot and look at it with a 10x magnifier. By my once (long ago) calibrated eyeball, the divot looks to be perfectly centered, which isn't likely to happen with a punch and hammer.

Whoever gouged up the rod like that deserves a sound thrashing. Some report good results by using a hex wrench as a pry-bar...but I haven't done that. If I was going to use that conrod again, I'd for sure file all the dings out of it and give it a good sanding/buffing to prevent cracking.

I do know of one OS .46LA rod failure on a new engine. It was reported here on SH by Mike Fitzgerald, and I got him to send me a picture of it. My guess is that the hole for the bushing was undersize or the bushing was oversize when it was pressed in. Check the picture and see if you agree.  One thing I see is that the engine in the picture doesn't have a "center" in the crankpin. Hmmmm. H^^ Steve
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In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.


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