Patrick's build thread. (IT RUNS!)
12-14-2014, 05:06 AM
#961
Three Wheelin'
Don't like that last photo. Surely that couldn't be the culprit? (surely not?)
12-14-2014, 06:34 AM
#963
Rennlist Member
Thread Starter
Hard to say if it was cause or symptom, just like a bunch of other things that failed.
Order of events were that when Paul went out on the brand new (treated [shaved/heat cycled]) tyres he came straight back into the pits after thinking that the vibration might have been loose wheel nuts. Assured that this wasn't the case he went out and did one hot lap. He came back in and the next session he went out on supposedly less affected tyres. The CV broke straight away and he came back in. We cobbled together a replacement setup and waited for the next session. He then had the first motor hardware failure which was the dry sump pulley. So he drove back to the workshop and made a whole new one out of a block of alu. Came back and fitted this and we thought we were going to be ok but had to come back in immediately after that when the b/shaft pulley sheared in half. Oh, and there was also a big crack in the intake which we also attribute to this high vibration / harmonic issue. We didn't discover that the rear suspension X member was also bent badly to such a point that the car actually had really high rear wheel toe out. It's easy enough to pontificate about what might have been the first domino. I am still not so sure it wasn't issues at the rear of the car that might have transferred down through the torque tube into the motor. There has been a big evil harmonic that has affected many parts but what caused it to start when we seemingly had none of these problems throughout the year. I say seemingly as there would appear to be evidence (metallurgically speaking) that the b/shaft pulley didn't break in one event. It looks like there are different colours in that break which might suggest it was stressing prior to failure.
Order of events were that when Paul went out on the brand new (treated [shaved/heat cycled]) tyres he came straight back into the pits after thinking that the vibration might have been loose wheel nuts. Assured that this wasn't the case he went out and did one hot lap. He came back in and the next session he went out on supposedly less affected tyres. The CV broke straight away and he came back in. We cobbled together a replacement setup and waited for the next session. He then had the first motor hardware failure which was the dry sump pulley. So he drove back to the workshop and made a whole new one out of a block of alu. Came back and fitted this and we thought we were going to be ok but had to come back in immediately after that when the b/shaft pulley sheared in half. Oh, and there was also a big crack in the intake which we also attribute to this high vibration / harmonic issue. We didn't discover that the rear suspension X member was also bent badly to such a point that the car actually had really high rear wheel toe out. It's easy enough to pontificate about what might have been the first domino. I am still not so sure it wasn't issues at the rear of the car that might have transferred down through the torque tube into the motor. There has been a big evil harmonic that has affected many parts but what caused it to start when we seemingly had none of these problems throughout the year. I say seemingly as there would appear to be evidence (metallurgically speaking) that the b/shaft pulley didn't break in one event. It looks like there are different colours in that break which might suggest it was stressing prior to failure.
12-14-2014, 06:43 AM
#964
Rennlist Member
Thread Starter
Something does look odd there. Nobody has ever said anything about that so I assumed it wasn't totally unusual and must have been to do with balancing the crank when it was done initially. Now I look at that and think it doesn't seem right. I'll ask some more questions.
12-14-2014, 06:47 AM
#965
Three Wheelin'
True. Just looking at the radial cracks around that stud, and the fracture plane, and thinking it looks like a hydraulic fracture (trapped oil). Might have initiated previous to your build. Would have made for some weird dynamics which might explain everything else.
Anyway, looking forward: 16V FTW!
Cheers,
Mike
Anyway, looking forward: 16V FTW!
Cheers,
Mike
12-14-2014, 06:51 AM
#966
Looks like it's on the second crank bearing that the block cracked... If a hydraulic fracture, could the dry sump system add more oil pressure than the block can handle?
If yes then perhaps the dry sump pump built so much pressure that it put too much stress on the crank pulley which eventually cracked? There must be a bleed valve somewhere in the circuit?
If yes then perhaps the dry sump pump built so much pressure that it put too much stress on the crank pulley which eventually cracked? There must be a bleed valve somewhere in the circuit?
Last edited by Thom; 12-14-2014 at 07:33 AM.
12-14-2014, 10:47 AM
#967
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Oh a better look at those photos. I'll change my thoughts! I never saw the crank side of the pics. Your pulley actually broke. I thought it sheared the keyway like mine did.
If the oil pump belt was to tight i see that happening.
Picture this. looking in front of the engine, you've got the oil pump on the right where the AC usually sits.
You have the extra pulley extended out from the crank
having the small amount of tightness will cause flex that fatigues the pulleys and causes them to crack.
It's easier to flex a tube of steel if it's 1m long than 200mm long in that sense.
It would be so good if you could run the power steering, alt and oil pump of one belt. IMO.
If the oil pump belt was to tight i see that happening.
Picture this. looking in front of the engine, you've got the oil pump on the right where the AC usually sits.
You have the extra pulley extended out from the crank
having the small amount of tightness will cause flex that fatigues the pulleys and causes them to crack.
It's easier to flex a tube of steel if it's 1m long than 200mm long in that sense.
It would be so good if you could run the power steering, alt and oil pump of one belt. IMO.
12-14-2014, 02:01 PM
#969
Burning Brakes
Wow, spectacular failure!
Perhaps you could use a main girdle reinforcing bridge? Something like this but made for the 951 block;
http://kiggly-racing.com/all/main-girdle.html
Perhaps you could use a main girdle reinforcing bridge? Something like this but made for the 951 block;
http://kiggly-racing.com/all/main-girdle.html
12-14-2014, 05:24 PM
#971
Three Wheelin'
Looks like it's on the second crank bearing that the block cracked... If a hydraulic fracture, could the dry sump system add more oil pressure than the block can handle?
If yes then perhaps the dry sump pump built so much pressure that it put too much stress on the crank pulley which eventually cracked? There must be a bleed valve somewhere in the circuit?
If yes then perhaps the dry sump pump built so much pressure that it put too much stress on the crank pulley which eventually cracked? There must be a bleed valve somewhere in the circuit?
By hydraulic fracture I mean that trapped oil in the stud tapped hole was pressurised (many thousands of psi) when the stud was wound in.
Last edited by mikey_audiogeek; 12-14-2014 at 07:46 PM. Reason: typo
12-14-2014, 06:30 PM
#972
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Well, that's racing. Sorry man! This is a perfect example to folks who don't race these cars, of just how tough racing is on engines. What's next for the car?
12-14-2014, 11:53 PM
#975
Rennlist Member
Something does look odd there. Nobody has ever said anything about that so I assumed it wasn't totally unusual and must have been to do with balancing the crank when it was done initially. Now I look at that and think it doesn't seem right. I'll ask some more questions.