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Rumbling noise from main bearings?

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Seek
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Rumbling noise from main bearings?

Post by Seek »

Hi guys, I'd like your opinion on this one. I am, rebuilding my R69 engine. Crankshaft was professionally done in Germany because the rear main bearing seat was worn out. Big end bearings were deemed to be perfectly allright.

When cold the crankshaft rotates very nicely. When heated up it makes sometimes(!) this weird rumbling noise. It seems to come from the rear main bearing. I used a NOS 20207M C3 bearing. There is no unusual amount of play in the bearing, radial something like 0.01 to 0.02 mm when cold.

What do you guys think? The noise is not always there. Will it disappear? Just some dustspecks in there? Or pull everything apart again and try again with a new bearing?

Link to video. Heated up to 100 degrees. Bearing well oiled. https://www.youtube.com/shorts/8Kkzg9s5ipE

Seek
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Re: Rumbling noise from main bearings?

Post by Seek »

And this is today. 100 degrees again (Celsius). I can hear the gears which have allready been installed but the weard rumbling noise of the bearing is not there. Call me confused....

https://www.youtube.com/shorts/UsuzmyJdMOQ

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vechorik1373
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Re: Rumbling noise from main bearings?

Post by vechorik1373 »

When assembling an R69 - R69S and R50S engine, with the barrel roller bearing it is very important to get the outer race of the bearing positioned exactly over the inner race during assembly. Because of the design of the barrel roller bearing, one can physically push and pull the inner race, with the captive rollers in and out of the outer race quite far. If the bearing is carelessly installed, and the inner and outer races are not aligned, it will cause the barrel rollers to to pinched from this misalignment, the bearing will feel rough when hand turned,and will cause premature bearing failure. This is the tool that must be used to insure that both races are in line with each other, when the crankshaft is drawn forward in the case, after it has been installed in the empty case. After one gets the crank laying in the case, but not yet installed in the rear main bearing carrier, you slip this tool through the carrier, and install it on the end of the crankshaft, and use the bolt that holds the flywheel on the crankcase, to hold the tool in place.
Then the case must be heated, and the crank installed in the case, too deep, on purpose. After the front main bearing carrier is installed, the crank must to drawn as far forward as it will go, and the tool will keep both races exactly in the correct position.

You may want to consider removing the flywheel, and do a depth measurement in the case of the outer race versus the inner race. I they are not both at the same depth in the bearing carrier, you may have to disassemble the whole engine and start over with the reassembly.
If the outer race is higher than the inner, it can be driven deeper tot he correct position without tearing the complete engine back down.
However, if the outer race is found to be in the carrier below the inner race, you have no choice but to take the engine apart and start over.
This is the tool I am talking about.
align.jpg
Vech
Technical Adviser, Former owner, Bench Mark Works
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Seek
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Re: Rumbling noise from main bearings?

Post by Seek »

Yes I have such a tool, made from brass way back in the IBMWR mailinglist days.

But I used a slightly different installation method. Your method seems more logical for the barrelbearings. Overhere in Europe it is now more often advised to use a different method: Put the crank in the case with the rearbearing not in the bearing carier yet. Then first heat up the front bearing carrier with front bearing and install it fully on the crankshaft. Then with a very hot case push the crank back into the rearbearing carier and at the same time the front bearing carier is inserted into the case. This method puts less stress on the front bearing. But it could indeed slide the 20207 bearing out of alignment!

Anyway, I meassured and both races are equally deep (within 1 thou). Maybe they were out of allignment and all my heating and pushing and turning pulled them back into the right position? I don't know, they are precisely alligned now, not the result of sheer luck I'd say.

Greetings and thanks for the good advice as always Vech!

Kees.

agloeckle
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Re: Rumbling noise from main bearings?

Post by agloeckle »

I'm about to try for the 3rd time to to install the crankshaft in the 1968 R69S that I am restoring. The second attempt was as described by Vech - attaching the rear bearing alignment tool to the crank before trying to insert it into the rear of the already heated case. But somehow, the bearing wound up cocked in the rear of the case. Maybe the flywheel nut worked itself loose as I tried to move the crank into position? Anyway, if I read Vech's comment correctly, it sounds like the crank goes in first, the alignment tool is attached and THEN the case is heated. Does that mean that the case, with the crank inside, is put in the oven to come up to 275? Or, is it recommended to heat the rear of the case with a MAAP torch until it reaches 275 and then move the crank rearward?
I'd really like the third time to be the charm and would be grateful for any feedback or opinions.
Thank you.

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Re: Rumbling noise from main bearings?

Post by 808Airhead »

I put the crank in,after heating the block of course, THEN put the rear bearing aligner tool on , and then put front bearing carrier on, put a little heat from Map gas/ electric heat gun (both work) around front and rear of engine if time has allowed it to cool down, and as I pull front bearing carrier down and it bottoms out, then the crank is pulled forward into carrier , and alignment tool will pull rear bearing forward with crankshaft.
Last edited by 808Airhead on Mon Dec 04, 2023 12:34 pm, edited 1 time in total.
Thomas M.
R69S - R60/2 - R67/2 - R51/3 - R69

agloeckle
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Re: Rumbling noise from main bearings?

Post by agloeckle »

Thank you, Thomas.

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Re: Rumbling noise from main bearings?

Post by 808Airhead »

Also, after it is all in I give the crank a rearward, then forward “dab” with a plastic mallet, this tends to “unbind” the crank, I have had it go from a little tight to completely free after this little whack on the crank. It works for me.
Thomas M.
R69S - R60/2 - R67/2 - R51/3 - R69

Seek
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Re: Rumbling noise from main bearings?

Post by Seek »

I just reread my initial post in this thread. I can report, the noise is gone and didn't reappear in use.
But be carefull with smashing on the end of the crankshaft. The pressfit isn't so tight that you can't shift something. I managed to bring the crank out of allignment by stemming the slinger plate screws! Next time I will just use loctite on these screws.

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Rodolfo850
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Re: Rumbling noise from main bearings?

Post by Rodolfo850 »

Hello

Also its good to check how front slinger seats on crank web. Im just rebuilding mine R60/2 and found that slinger rubs against bearing support, due a poor seat of slinger near crank pin.

Still making some measurements, but just found that fixing bolts has different cone profile (new are bigger) having a big and different angle, deforms slinger when fitting tight, but tomorrow will check again with an old bolt pair.

Regards

Rodolfo

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