posted
Just wondering if anyone else has had issues with the rear bearing in their 928????
Mine has split one of the balls and sent bits through the entire engine, destroying the engine.
The engine would have about 5-6 Ltr's of fuel through it, of which 3-4 Ltr's were running it in. I'm running the 2045 pipe, 8mm carb restrictor in a LST with roto-start.
Temps were never higher than 250*F, using the same fuel I have always run, 25%nitro 12%oil.
Will post up some pic's later.
-------------------- Tassie-Devil n. carnivorous marsupial, coloured black with white markings, mainly carrion-eating and of fierce appearance, and occurring only in Tasmania. Posts: 8 | From: Tasmania Australia | Registered: Apr 2006
| IP: Logged
-------------------- Tassie-Devil n. carnivorous marsupial, coloured black with white markings, mainly carrion-eating and of fierce appearance, and occurring only in Tasmania. Posts: 8 | From: Tasmania Australia | Registered: Apr 2006
| IP: Logged
posted
Oxidation is often the start of the degradation of a main-bearing. Once a small piece of metal is teared down from the surface the descruction process starts and ends up as is shown on the pictures.
The only thing you can do to prevent these kind of disaster is to open and clean your engine after each time you use it when you are not planning to use if for a week or so. This operation will then also give you the opportunity to evaluate the state of your main-bearing.
posted
OUCH!!! I dunno about oxidation, as the rear bearing doesn't really look all that rusty. But the ball bearing retainer looks to be pretty wore out, at least on one side. Or at least the ball bearings look to have alot of play where they sit on the race.
I too had to replace my rear bearing, probably about 7 gallons deep(I think). Not very fun, as the tolerances are pretty dang tight, which I think is a good thing as RB probably used the largest bearing possible. Still hard to get out never-the-less
But I caught mine, as I could actually hear the vibration from the engine. I don't think there were any bearings missing or chipped, but the bearing did feel rough when spinning it by hand.
But now that you mention it, I did have a piston score mark, that I could not explain... Luckily, whatever it was must have went straight out, as the top of the piston was still in good shape and the score wasn't into the pinch zone.... Posts: 67 | From: Covington, La. | Registered: May 2006
| IP: Logged
posted
It took me some time..but I did figure out how to get it out... The pic was just a testiment to the trickery it took to get out...
I think of it as a good thing...as RB chose to use the biggest bearings possible for the block... Anyother el'cheapo motor, the bearing just falls out... Posts: 67 | From: Covington, La. | Registered: May 2006
| IP: Logged
posted
I very much doubt that oxidation was the cause of the rear bearing failure.
In my opinion it was more likely the rear bearing started to fail due to a flaw in one of the balls, and as it started to break up the pieces of bearing went through the motor destroying it.
-------------------- Tassie-Devil n. carnivorous marsupial, coloured black with white markings, mainly carrion-eating and of fierce appearance, and occurring only in Tasmania. Posts: 8 | From: Tasmania Australia | Registered: Apr 2006
| IP: Logged
posted
how can you say that is oxidation.... the bearing was a defect its plain as day.... that ball is completely crushed... i can't believe this....
Posts: 215 | From: usa | Registered: Apr 2006
| IP: Logged
posted
Believe it or not but when you have an oxidation(even very small) on the line where the balls are rolling, or even the balls itself. It rips off a very small piece of metal and then the surface has become uneven and at 40.000rpm with the charge it will rip of another piece and another one and so on. The engine of the above broken bearing must have made a very unnatural noise for some time...
posted
It's quite hard to make sure what finally caused the bearing going bad. As well as all bearing defects are caused by dirt, too lean running, oxidation or wrong axial play of the crankshaft. But it's for sure that the splitted piece of the ball was an effect and not the cause.
quote:The engine of the above broken bearing must have made a very unnatural noise for some time...
This engine was pulled down for inspection prior to it's last race meet and was in perfect condition. At the next race meet I ran three 10min heats with no problems at all. I started the 30min final and started to have some problems at the 15min mark. I had two flame outs one after the other on the same corner. After the second flame out my crew fitted a new glow plug which stopped the flame outs but I noticed that the truck wasn't running as strong as it was at the start of the finals. I decided to retire from the race as I was unsure what was causeing the problem and didn't want to damage either the engine or truck any further. Upon pulling the engine down, I found the damage as posted in my first post. It wasn't a problem that was left and could have been prevented, it all happened very quick within two laps of the track.
Guess I'm just the unlucky type.
Well I've got myself a new TM928 running now, same fuel, pipe, glow plug range, air-filter, truck, driver and have not had any issues with it at all. This engine has got about 10ltr's of fuel through it now and goes hard.
-------------------- Tassie-Devil n. carnivorous marsupial, coloured black with white markings, mainly carrion-eating and of fierce appearance, and occurring only in Tasmania. Posts: 8 | From: Tasmania Australia | Registered: Apr 2006
| IP: Logged
UBBFriend: Email this page to someone!
![[Eek!]](eek.gif)
![[Big Grin]](biggrin.gif)
![[Razz]](tongue.gif)
