Broken bottom Yoke / Triple tree

BPHORSEGUY said:
G81 Can Cycle said:
I assumed it was a casting. The look of the material at the fracture had the look of a failed casting. I have looked at the part more closely, and can see it has been machined

I discussed this failure with the parts guy at Norton UK. I told him I was scanning the part and was going to make a billet unit. He explained that Norton made a billet unit and it was for the Domi, so I purchased one. He did not explain that all the yokes were billet.

I did scan the part, and redesigned areas that our FEA (finite element analysis) showed as weak areas. But we never put it into production.

John
Click to expand...

Good to know, Thanks for the info John. What software are you using?
Bob
Click to expand...

Bob

We use SolidWorks for CAD, FEA, and Gear Design. It is not the most powerful for FEA but gets the job done. As you most likely know FEA has a lot to do with input, some input is black and white like material, but some is very gray like assumed loads or stresses. The FEA we ran showed a marked weakness where this yoke has broken. But again some of the data we put into the calculation may be off (but on the other hand, it is where it broke on at least two triple trees)

Our scanner uses a proprietary software to handle raw scanned data. We have additional software that converts the raw scan data into a SolidWorks model for design manipulation or tool path.
 
Hi,

The reality is the FEA is only as good as its inputs and understanding the correct load inputs to represent real world can be very difficult, we have lots of data and lots of experience with this.

Ultimately the area you have pointed out is always highlighted as the weak area, however this does not mean that the part is not designed correctly. We have produced 1000's of bikes over the last 5 years that are out in the world with high mileage and yet these are the only two yokes we know of as having an issue. It is imperative we have the two yokes sent back to the factory for analysis to fully understand and assess the situation.

John , please can you send the yoke back to us that you have and PM me some more details on what happened and when, starting with the VIN of the bike the yoke was originally fitted to.

Trevor, I will be in contact with MCC and ask them to send the yoke back to me, please could you also PM your VIN.

Regards

Simon
 
trevorpacker said:
Bottom yoke clamp broke on my 2015 961.
4000 trouble free miles until this.
Dropped it off at MCC on Wednesday (1000 mile run from Houston) will be interesting to see how long it takes to get the part.


Hi Trevor,

I have just spoken with Bob at MCC and he has confirm the bottom yoke has just arrived with him. Please let me know if you have any further problems.

Regards

Simon
Click to expand...
 
Well finally got the bike back after yoke replacement and other warranty repairs. despite the super fast delivery of the yoke from Norton other issues delayed the work for 2 months.
Had intended to fly to Chicago and ride the bike back to Houston but recent cold weather made me change my mind and take a trailer to pick it up, crazy 2400 mile drive but did get to visit the Mississippi music museum in Hazelhurst, birthplace of Robert Johnson.

Well while getting the Yoke replaced MCC discovered gearbox seals leaking, this probably backs up the posts on this site recommending the transmission vent. Norton tell me there is no factory modification for gearbox breathing.

The new Norton engine breather kit has also been installed and I must say I am impressed with this, now very easy to check oil level, it does not seem to vary much from engine running or not. I guess this is due to the check valves installed in the oil pump and also the new longer dip stick which is now 6 inches long (152 mm) and has fine knurling which makes it easier to see the oil level. system has a catch bottle and what looks like strainers in the oil lines. , some pics below.

After a spirited 90 mile thrash yesterday the smile is back on my face and not a drop of oil in the catch bottle. All is good in 961 land, for now.

[ATTACH=full]67603[/ATTACH][url=https://flic.kr/p/Qeei1m]Untitled by Trevor Packer, on Flickr [/url]

[ATTACH=full]67604[/ATTACH][url=https://flic.kr/p/P3WSRs]Untitled by Trevor Packer, on Flickr [/url]

[ATTACH=full]67605[/ATTACH][url=https://flic.kr/p/QhtXGn]Untitled by Trevor Packer, on Flickr [/url]

[ATTACH=full]67606[/ATTACH][url=https://flic.kr/p/QfRjc1]Untitled by Trevor Packer, on Flickr [/url]

[ATTACH=full]67607[/ATTACH][url=https://flic.kr/p/P3TJn8]Untitled by Trevor Packer, on Flickr [/url]
 

Attachments

  • Broken bottom Yoke / Triple tree
    31654832976_7fd5fe7a9b.webp
    23.2 KB · Views: 136
  • Broken bottom Yoke / Triple tree
    30882108204_4aa188689f.webp
    26.1 KB · Views: 122
  • Broken bottom Yoke / Triple tree
    31691644185_fa98b97158.webp
    18.6 KB · Views: 128
  • Broken bottom Yoke / Triple tree
    31673177486_7592943871.webp
    26.7 KB · Views: 126
  • Broken bottom Yoke / Triple tree
    30881494313_a6dbc9f5e9.webp
    35.6 KB · Views: 130
That's great news, Trevor. My 2013 also went through the mods and I don't lose any oil anymore. Instead of the catch bottle, I have clear tubing and a plug instead of the black hose so I can monitor any loss. Glad you are on the road. Too cold here in NY for a ride although if the sun shines and the winds die down, I can do a town ride.
 
NortonFactoryUK said:
Hi trevorpacker,

We have not seen a warranty claim for this yet, however this is obviously not acceptable and all I can do is apologise for the situation. Please be assured we will get the parts out to your local dealer (MCC I believe) today on express shipment.

We will have the damaged part returned to us for detailed analysis as we have NEVER seen this happen before.

Apologies again

Simon
Click to expand...
Hi Simon, mine broke today too and my bike has only done 250 kilometres! I have email the generic 'info@norton...." but would I would be happy to hear from you too. Regards, Dan, Western Australia.
 
Hi,

The reality is the FEA is only as good as its inputs and understanding the correct load inputs to represent real world can be very difficult, we have lots of data and lots of experience with this.

Ultimately the area you have pointed out is always highlighted as the weak area, however this does not mean that the part is not designed correctly. We have produced 1000's of bikes over the last 5 years that are out in the world with high mileage and yet these are the only two yokes we know of as having an issue. It is imperative we have the two yokes sent back to the factory for analysis to fully understand and assess the situation.

John , please can you send the yoke back to us that you have and PM me some more details on what happened and when, starting with the VIN of the bike the yoke was originally fitted to.

Trevor, I will be in contact with MCC and ask them to send the yoke back to me, please could you also PM your VIN.

Regards

Simon

From Simon . Norton should take care of it.
 
BritTwit said:
That sucks!
The silver lining in that cloud is that you found it before a potentially dangerous situation.
Norton should make it right for you.
Click to expand...
Sadly, the bike is out of warranty (it was in a display for a couple of years) so I'm on my own.
 
Do not assume that . Contact Norton asap directly . Looks like they all have broken in the same place/same side.
 
G81 Can Cycle said:
Same crack, same place, front of lower left tripe tree clamp This happened on the race bike, so I did not file a warranty claim. I was going to make a new one out of billet, but the factory already had billet units for the Domi. I bought one new cast unit and one billet

The radius on the outside of the clamp where it blends to the clamping flange needs to be about 3 time larger. This would not effect the counter bores for the screw heads, as an end mill could easily start the interrupted cut into the radius.

Before we learned that a billet was available from Norton we scanned and redesigned the triple tree with a much larger radius in the area described above
Click to expand...
Hi John, given this was over a year ago, did you ever produce a billet item?
Regards Dan
 
TonyA said:
Do not assume that . Contact Norton asap directly . Looks like they all have broken in the same place/same side.
Click to expand...

Absolutely!
I think a persuasive case can be made that for all intents and purposes this bike was new to you with only 250 Kilometers on the clock.
This fault has appeared in our machines.
 
TonyA said:
Do not assume that . Contact Norton asap directly . Looks like they all have broken in the same place/same side.
Click to expand...

If I am not mistaken , All of the broken fork yokes were 2015's !!! Maybe the same person over torqueing them ??? How about that one folks ? But why that l/h side always ? Same side same person ? Just wondering that's all , but so far all 2015 year.
 
TonyA said:
If I am not mistaken , All of the broken fork yokes were 2015's !!! Maybe the same person over torqueing them ??? How about that one folks ? But why that l/h side always ? Same side same person ? Just wondering that's all , but so far all 2015 year.
Click to expand...

That's truly strange,
Tony are you sure about all the occurrences?
It doesn't seem like they all could simply be coincidences occurring in that manner.
 

Similar threads

DBT
Another broken bottom yoke/triple tree.
Replies
2
Views
1,122
DBT
DBT
C
  • Locked
lower fork yoke/triple tree allen bolt torque setting.
Replies
2
Views
999
Commando74
C
Back
Top