Broken Torque Rod Bolt

[MartyNZ]

1 hour ago, p6x said:

Guzzi should have computed the shear force that load bearing component would be submitted to. Usually, you send the blue prints to a specialized company and they tell you what force that component will have to sustain.

That bolt should have been manufactured to precise specifications, using a given metallurgy and maybe thermal treatment. Guzzi would have ordered a large batch to support manufacturing.

The important factor is that, the shearing strength seems inadequate for a normal usage. For such an important component, it would be probably better to have one purpose made; if we knew what the maximum shear force it has to see.

Actually we can be certain that Guzzi calculated the shear strength required correctly. If the bolt failed in shear, then we would see 2 shear planes, as the bolt is in a double shear clevis. Since the bolt usually fails under the head, or at the first thread on the shank, failure is likely caused by stress corrosion cracking or fatigue. These conditions can lead to a break at very low loads compared to simple shear. 

We have to stop the rust, as a rust pit is the initiation point for a crack.

I believe that a new standard bolt assembled with anti-corrosion jointing compound will last a other 20 years.

[docc]

5 hours ago, Speedfrog said:

Screw, 10mm x 59mm - GU01357731  —  AF1 Racing, Austin Texas  —  $2.91

https://www.af1racing.com/GU01357731-Screw--10Mmx59Mm---GU01357731

With these web listings, it is recommended to contact the shop and verify inventory. More likely this part is not in shop inventory, but may be "in North America (as Harper's verified for me), but other times may be in Italy. Or months later learn that it really wasn't available there, either. Again, Harper should have a few of these on hand in a few weeks, assuming they actually are "in North America."

5 hours ago, MartyNZ said:

Actually we can be certain that Guzzi calculated the shear strength required correctly. If the bolt failed in shear, then we would see 2 shear planes, as the bolt is in a double shear clevis. Since the bolt usually fails under the head, or at the first thread on the shank, failure is likely caused by stress corrosion cracking or fatigue. These conditions can lead to a break at very low loads compared to simple shear. 

We have to stop the rust, as a rust pit is the initiation point for a crack.

I believe that a new standard bolt assembled with anti-corrosion jointing compound will last a other 20 years.

This is exactly the type of failure apparently being revealed here, not actual "shear" in the purest most definitive use of that term in the machinist's/mechanical engineering parlance.

KaleV11's failure was apparently at or near"first thread to shank."

Looking forward to more info from LowRyter . . .

[al_roethlisberger]

Well I ordered one of the AF1 bolts, so we'll see how long it takes to arrive and how it compares to what came on the bike originally.

 

It looks like it may be several weeks before it shows up though.

[docc]

Just now, al_roethlisberger said:

Well I ordered one of the AF1 bolts, so we'll see how long it takes to arrive and how it compares to what came on the bike originally.

 

It looks like it may be several weeks before it shows up though.

My recent experience (like, the last ten years) is to call when inventory is shown on these various websites. It is most common that the item is not in store inventory, might be in North America, and could be in Italy, yet might simply be NLA and the website has not been updated to reflect the changes.

I suggest calling AF1 directly and finding out what the actual current availability is.  As in, they say, "They are in North America, but we have to order ten." Or "There were ten in North America, but someone ordered them yesterday."

I am sitting on a six month old invoice from a Moto Guzzi dealer for parts that had to come from Italy. "Be here in a few weeks."   Six months later . . . .

[LowRyter]

1 hour ago, docc said:

With thse web lising, it is recommended to call the shop and verify inventory. More likely this part is not in shop inventory, but may be "in North America (as Harper's verified for me), but other times may be in Italy. Or months later learn that it really wasn't available there, either. Again, Harper should have a few of these on hand in a few weeks, assuming they actually are "in North America."

This is exactly the type of failure apparently being revealed here, not actual "shear" in the purest most definitive use of that term in the machinist's/mechanical engineering parlance.

KaleV11's failure was apparently at or near"first thread to shank."

Looking forward to more info from LowRyter . . .

I might go to the shop tomorrow and look at the new Mandello- if not tomorrow, next week.  I'll try to remember to ask him about the bolt.  I'd guess he threw it out.  But I'll try to ask.

[docc]

10 minutes ago, LowRyter said:

I might go to the shop tomorrow and look at the new Mandello- if not tomorrow, next week.  I'll try to remember to ask him about the bolt.  I'd guess he threw it out.  But I'll try to ask.

Sure would be good to see images of that bolt failure. Also, an idea how much rust and corrosion was involved.

Just a reminder, @LowRyter, to have your technician inspect and service that outboard needle cage. Let us know if it proves also very rusty and needy . . .

[Speedfrog]

My experience with AF1 is that their inventory showed on the product page is pretty accurate(unlike Harper's) and when an item is not in stock, the delivery time showed will pretty much tell you whether the item in the US (3 to 4 weeks) or in Italy (2 to 3 months). If an item is NLA it is simply not listed.

Of course it doesn't hurt to ask if you want to make sure of the availability of a part.

Note that AF1 doesn't take phone calls anymore, which I can't blame them for as it can waste a lot of resources answering questions all day, but they are very responsive through email and you will most likely get an answer within 24h directly from Ed Cook, the boss there.

[al_roethlisberger]

According to the item description on the AF1 website for the part:  

Quote

Availability: Expected to arrive at our warehouse in mid April if ordered today

 

We'll see 

[docc]

3 minutes ago, al_roethlisberger said:

According to the item description on the AF1 website for the part:  

Availability: Expected to arrive at our warehouse in mid April if ordered today

We'll see 

Sounds like North American availability, then.

As you say, we shall see . . .

[p6x]

4 hours ago, MartyNZ said:

Actually we can be certain that Guzzi calculated the shear strength required correctly. If the bolt failed in shear, then we would see 2 shear planes, as the bolt is in a double shear clevis. Since the bolt usually fails under the head, or at the first thread on the shank, failure is likely caused by stress corrosion cracking or fatigue. These conditions can lead to a break at very low loads compared to simple shear. 

We have to stop the rust, as a rust pit is the initiation point for a crack.

I believe that a new standard bolt assembled with anti-corrosion jointing compound will last a other 20 years.

When I was working at my battle tank factory, all the components affixed to the chassis and exposed to the environment where treated against corrosion. I think Cadmium plated. Support wheels, road wheels, sprockets, tension pulleys...

Quote

 

Cadmium plating is an attractive, soft coating that can be deposited on various base materials, up to and including steels, copper and different types of iron. Moreover, it is one of the few deposits that is sacrificial, excelling in corrosion protection.

With natural lubricity, Cad plating also provides anti-galling and low friction properties.

 

 

[docc]

1 hour ago, p6x said:

When I was working at my battle tank factory, all the components affixed to the chassis and exposed to the environment where treated against corrosion. I think Cadmium plated. Support wheels, road wheels, sprockets, tension pulleys...

 

 

It appears the current replacement fastener is nitrided, phosphated, or otherwise surface treated? (I realize this is not cadmium plated.)

Is this coating/treatment, perhaps, the more pointed purpose of the new fastener rather than the tensile strength change or the change of thread pitch?

Is this all about the corrosion vulnerability?

[MartyNZ]

5 hours ago, docc said:

It appears the current replacement fastener is nitrided, phosphated, or otherwise surface treated? (I realize this is not cadmium plated.)

Is this coating/treatment, perhaps, the more pointed purpose of the new fastener rather than the tensile strength change or the change of thread pitch?

Is this all about the corrosion vulnerability?

Black oxide conversion coating is good for corrosion protection, cheaper than cadmium plating, but not as good. Still, it is good enough.

[LowRyter]

Docc, went to the shop.  Don sent me this photo of the failed bolt.  Regarding the needle bearings, I noticed there was fresh grease in it.  He told me that he inspected and regreased it.  Of course I request the he service the driveshaft as well.  

[docc]

48 minutes ago, LowRyter said:

Docc, went to the shop.  Don sent me this photo of the failed bolt.  Regarding the needle bearings, I noticed there was fresh grease in it.  He told me that he inspected and regreased it.  Of course I request the he service the driveshaft as well.  

Thanks, @LowRyter! This is exactly how @kalev11 described his fail to me and suggestive of the failure @MartyNZ noted . . .

"Actually we can be certain that Guzzi calculated the shear strength required correctly. If the bolt failed in shear, then we would see 2 shear planes, as the bolt is in a double shear clevis. Since the bolt usually fails under the head, or at the first thread on the shank, failure is likely caused by stress corrosion cracking or fatigue. These conditions can lead to a break at very low loads compared to simple shear. "

 

[p6x]

12 hours ago, MartyNZ said:

Black oxide conversion coating is good for corrosion protection, cheaper than cadmium plating, but not as good. Still, it is good enough.

If my life may be at stake, I usually don't settle for cheaper. Now I don't necessarily go for overkill, but generally speaking, the usual "better safe than sorry" is sound with me.

I don't want my fastener to snap while I am in the Chihuahua desert.

In any case, getting a single screw cadmium plated is probably cost prohibitive. Maybe Copaslip should do the job.

By the way, just as an afterthought, wasn't the CARC system a replacement to the additional Torque Rod of the previous generations?