V11 Daytona project

[Lucky Phil]

I thought before I get too far into this gearbox stripping and painting I'd better check that the mounts weren't cracked.

First step break out the dye check kit.

Clean down the mount area and apply the dye. Wait for 15 minutes.

Clean it off again with solvent and apply the developer. All good thankfully. Its not hard to see why they can crack here. There is not genuine radius from the vertical machined face to the horizontal area. its just the edge created by the face cutter. I'll create a radius here by hand as there's  a decent amount of material and what you lose will be more than compensated for by the removal of the stress raiser from the machining.

   

Ciao

[Lucky Phil]

So here's the gearbox mount rework. 4mm round file and take it carefully. Finish off with some 800 wet and dry on the file followed by green Scotchbrite. 

Important to make sure the finish of the fillet is smooth and free from surface defects that may cause stress risers.

Ciao

[luhbo]

Consider to rework this area, too.

[Lucky Phil]

1 hour ago, luhbo said:

Consider to rework this area, too.

You mean take that corner off?

 

Ciao

[LowRyter]

For a noob like me, why is taking metal off a casting going to make it stronger?

[luhbo]

3 hours ago, Lucky Phil said:

You mean take that corner off?

 

Ciao

Yes. Along this line  you should see the steepest change in stiffness.

To be on the safe side enlarge the through hole and press in a matching piece of tube. The tube shall bear the clamping forces, so that left for the flange is keeping the gearbox in position(enough a task)

[luhbo]

3 hours ago, LowRyter said:

For a noob like me, why is taking metal off a casting going to make it stronger?

the housing doesn't get stronger, it's just more unlikely to break at this line. As it typically does. It's because the tension distribution in the material is more evenly, smoother. That helps especially under dynamic loads.

[LowRyter]

4 hours ago, luhbo said:

the housing doesn't get stronger, it's just more unlikely to break at this line. As it typically does. It's because the tension distribution in the material is more evenly, smoother. That helps especially under dynamic loads.

So it's variation of 'the least resistance'?  The forces find the weakest area, so remove that area?  (and my thinking the more material the greater strength)

Thanks for the lesson.  

[luhbo]

28 minutes ago, LowRyter said:

So it's variation of 'the least resistance'?  The forces find the weakest area, so remove that area?  (and my thinking the more material the greater strength)

Thanks for the lesson.  

Not so much removing the weakest aerea, more weakening the stiffer areas next to it.

found in Wikipedia

[Lucky Phil]

8 hours ago, luhbo said:

Not so much removing the weakest aerea, more weakening the stiffer areas next to it.

found in Wikipedia

On balance I think I'll leave it the way it is with just the radius done. The above is interesting and I understand the concept but its not quite applicable to the V11 gearbox mount in that no matter what the loads will go through the radiused area. No ability to create a modified load path. To give a lateral steel bush any meaningful wall thickness you would need to open up the mount holes 4mm which I think would be too much but the idea is sound. What you could do is use a tube between the inner faces of the mount lugs that the bolt passes through which would achieve the same results with regards to the crushing/squeezing loads from the bolt. However that would require machining the inner faces of the bosses to square them up and I dont have access to a mill at the moment.The lateral ribs between the mount lugs are also at bolt hole center line as well which will take the mount bolt crush well enough I think on balance.

Considering the occurrence of gearbox cracking, the mileage at which it generally occurs, the fact I now have the supplemental gearbox mount and have done the radiusing and the low mileages I actually do I think as I said I'll leave it there. All good suggestions though and worthy of consideration for those with the box out and access to the machining equipment and the prospect of lots of miles.

Ciao  

 

  

[luhbo]

On my actual bike I have done nothing of the above discussed modifications and the gearbox is still good after at least 80.000 km.

My first one was already sipping when I bought it with 30.000km in 2004. With 200.000 11 years later it did still the same, a few drops per day. Never had to refill any oil.

Based on that the most important thing is to not overtighten this mounting bolt I'd say. Besides that the mentioned tube mod is done quite frequently over here. 

[Tinus89]

On 6/27/2019 at 12:47 PM, luhbo said:

Consider to rework this area, too.

 

That lowest/most right corner is where my gearbox cracked...

[Chuck]

1 hour ago, Tinus89 said:

 

That lowest/most right corner is where my gearbox cracked...

I'm not surprised. Ideally, it would be a big radius from the lower edge to the machined surface.

[Lucky Phil]

12 hours ago, luhbo said:

On my actual bike I have done nothing of the above discussed modifications and the gearbox is still good after at least 80.000 km.

My first one was already sipping when I bought it with 30.000km in 2004. With 200.000 11 years later it did still the same, a few drops per day. Never had to refill any oil.

Based on that the most important thing is to not overtighten this mounting bolt I'd say. Besides that the mentioned tube mod is done quite frequently over here. 

Ok didnt know that. I think I'd still go with a tube insert between the lugs and leave the metal in the holes. Seems the cracking is a bit hit and miss but better to address it if possible. I would go all out if I had the equipment of my machinist friend was still local to me but hopefully the extra gearbox support and radius will be enough to mitigate the risk.

Ciao 

[Lucky Phil]

10 hours ago, Tinus89 said:

 

That lowest/most right corner is where my gearbox cracked...

Ok good to know. I didnt realize they cracked there as well. May need to do some blending there also or remove the whole corner as luhbo mentioned.

Ciao