8V cam Pt 2: follow-up

[belfastguzzi]

Well Hubert it is funny that you ask today, because a few hours ago I saw a comment on pictures of the tappets that I have on Flickr.

Someone posted a couple of weeks ago. Unfortunately I didn't see it earlier. He seems to be in Japan. Matti Naskali.

 

He said:

 

"Interesting to see what has happen to the lifters and cams.

My Griso is waiting for call from the importer. Parts should arrive next week. Now I've done 3000km, engine is pretty noisy on left side, though I adjusted the clearances. Can't really understand what makes the noise, sounds like the chain is loose.

I hope Griso can make 500 km trip next week, it is a golden wek holiday here.

Did the engine turn fine after getting new parts?"

 

Yikes! Same story as mine.

Same mileage, same side, same noise.

I would have told him, don't ride it!

I wonder what happened on the 500k trip?

I reckon it didn't get any quieter.

 

Any that I've heard about have gone bad on the LEFT side. Coincidence, or a particular reason????

 

http://www.flickr.com/photos/belfastguzzi/...94037/comments/

 

In a week's time, it will be the Guzzi meeting here that I am organising. So we'll see how it is after that.

[gstallons]

The fact that the lifter did not show a concave wear pattern explains that the camshaft lobe had the poor hardening process or quality of materials. I have no explanation as to why the left side has always failed. Were both sides replaced and did the other side exhibit any signs of wear?

[luhbo]

I'll email him tomorrow. I think on his bike the damage was on the right side, but that's only guessing at the moment. Could be because the sidestand is on the left so you're talking always about the right side while your standing in front of a bike.

I just hope you'll have acceptable weather for your meeting and a real nice time then. I was watching the thread all over winter, but it's too far away for a weekend's trip and I'm in hollidays exactly 2 weeks later (for 2 weeks) so it was not possible for me to come. I has planned it in the same way as Jaap does it now, having seen Cornwall and the Borders mostly just from inside a car so far. Driving is not that funny there. Not because all people are driving on the wrong side, but either you're on boring camera supervised highways or you're easily stuck for hours in so very romantic dense and dark alleys where you see nothing from the landscape at all. I always thought on a bike you must have different horizons, and the pictures posted in the meeting thread proofe that it is possible.

Maybe later this year. If McGuzzi is right with the Mandello gossip about an already cancelled GMG this year then a week or so on the island could be possible. You've to have hope, you know

 

Hubert

[belfastguzzi]

The fact that the lifter did not show a concave wear pattern explains that the camshaft lobe had the poor hardening process or quality of materials. I have no explanation as to why the left side has always failed. Were both sides replaced and did the other side exhibit any signs of wear?

Why are you saying the cam lobe is the soft part, Gene?

The foot of the tappet bowls are very badly worn in a generally concave manner. Not smoothly concave, a bit 'lumpy'!

They are worn much more than the cam lobes.

 

The left side was by far the worst. Right side not bad, but I don't have photos.

Both sides are replaced in the recall.

[gstallons]

When automotive camshafts fail, the lifter wears a LOT along with the lobe of the camshaft. It is a deep concave of the lifter (bottom) foot when it wears out. In the lat 70s and early 80s Chevrolet had a multitude of camshaft failures with no explaination. Replacement parts showed no signs of trouble.

[pete roper]

When automotive camshafts fail, the lifter wears a LOT along with the lobe of the camshaft. It is a deep concave of the lifter (bottom) foot when it wears out. In the lat 70s and early 80s Chevrolet had a multitude of camshaft failures with no explaination. Replacement parts showed no signs of trouble.

 

Nah, it's a tappet issue. Why else would only the tappets be replaced on zero mile bikes? I also took failed parts to the Australian Mint for testing the cam was an acceptable 60 Rw but the tappets were only 39Rw.

 

Hubert. 8 valves, forked rockers, 4 tappets.

 

Pete

[belfastguzzi]

8 valves, forked rockers, 4 tappets.

 

Pete

mmm My tappets were forked too.

[luhbo]

....

Hubert. 8 valves, forked rockers, 4 tappets.

....

 

Sorry, I forgot to add the "Irony" or "Dumbass" icon in the mentioned posting.

 

Hubert

[gstallons]

Nah, it's a tappet issue. Why else would only the tappets be replaced on zero mile bikes? I also took failed parts to the Australian Mint for testing the cam was an acceptable 60 Rw but the tappets were only 39Rw.

 

Hubert. 8 valves, forked rockers, 4 tappets.

 

Pete

I'm not up on metallurgy(sp). How close in hardness do two metals need to be so that do not wear?

I assume Rw means Rockwell hardness?

[mike wilson]

Any that I've heard about have gone bad on the LEFT side. Coincidence, or a particular reason????

 

My guess would be a particulate reason.

[mike wilson]

Driving is not that funny there. ..........................stuck for hours in so very romantic dense and dark alleys where you see nothing from the landscape at all................................

 

Only true anywhere south of about Yorkshire. After that, the countryside is high up with good views.

[mike wilson]

I'm not up on metallurgy(sp). How close in hardness do two metals need to be so that do not wear?

I assume Rw means Rockwell hardness?

 

It's a "horses for courses" thing, with one answer not being applicable to all scenarios. In this case, however, both parts need to be both hard and similar. On top of that, there needs to be a designed-in manner of spreading the wear as evenly as possible across the system. Because of how cams work, most wear would accrue at the point where the cam starts to work if there was not a system to "shuffle" that point about. Normally, this involves a way of getting the tappet to rotate a little each time it is lifted by the cam.

[gstallons]

The lifter is made with a concave and the lobe is made with a slight taper to cause the lifter to spin. Roller camshaft/lifter setups are made square (at right angles) to keep the roller and lobe surfaces in equal contact.

I thought that metals with the same hardness would wear whereas steel/bronze will not wear?

[Skeeve]

I thought that metals with the same hardness would wear whereas steel/bronze will not wear?

 

You're confusing galling w/ wear: steel on bronze will (generally, barring special circumstances) wear the bronze.

[Skeeve]

I'm not up on metallurgy(sp). How close in hardness do two metals need to be so that do not wear?

I assume Rw means Rockwell hardness?

 

Answering in reverse order:

 

Generally written R_C for Rockwell C scale [A, B, C scales are progressively harder, with overlap; iirc, 100 R_B is about 20 R_C.] Then there's other [usually older] standards like Brinell, etc.

 

The Rockwell scales all use pretty much the same procedure, an anvil is pressed into the test material under a set pressure & time, & the resulting crater is measured. The only real difference is the test anvil: hardened ball, diamond point, etc.

 

As far as how "close" in hardness the materials need to be, it's going to depend upon the application. Ideally, you want them as hard & smooth as you can get: the harder the surface, the less prone to wear it is, and the smoother the less chance to catch on another surface sliding by. But the harder something is the more brittle it will be, generally speaking. Carbide cams & lifters would disintegrate in a few thousand? hundred? dozen? miles w/ all the hammering they take.

 

Steel can be case-hardened, which will leave a nice, malleable core underneath a hard long-wearing face. The lifter's Pete spoke of being so soft really aren't all that soft: 39 R_C is about the temper of high-powered rifle actions/barrels. But that's through hardened, which would be strong but still tough. The lifter face, being a surface that would be exposed to a lot of pressure and sliding abrasion from the cam surface, coulda/woulda/shoulda been cased up to a hardness matching that of the cam, say high 50s [softer than the cam so they wear before the cam, and tougher because they aren't quite so hard to take the hammering against the cam face.]

 

Note: IANAE [i am not an engineer], this is just the sum total of a lifetime of making inquiry into how stuff works and a few welding classes*.

 

Ride on!

 

 

* - My friends were always amazed that I took welding classes, apparently thinking that was too "blue collar" for someone of my refined character. I was always amazed at their amazement: new & better ways of playing w/ fire? OF COURSE I would take welding classes!