Deleted gearcase thread issue 8

[preload]

On Mike's suggestion, I have asked admin of the forum to delete the thread. But we can discuss that here

Desert forx post
"What grade of bolt is it ie whats its proof load? img511 and 514 don't work.
I assume the bolts are in tapped holes?
Could be a number of things like you have already mentioned
vibration;cyclic loading.
If the bolt pre-load is not high enough the bolts can loosen
off under vibration and subsquently fail in fatigue.
Have you any of the failed screws? if so post a pic.
In addition if your truely getting 80% - 90% of proof load on all bolts it doesn't give you much room for increasing
bolt tension unless you use a higher strength material.
Finally the bolts will not see equal tension , shear etc
for a given engine position: but depending on engine position and external force position at a particular point in time the bolts will share the load unequally.
"

Yes the bolts are in tapped holes and the holes are blind. Bolts dont break, they just come loose or missing.

6 Bolts,joint and proof load info

4 perimeter bolts (Bolt 1-4) – 3/8-16 (1.75 in) unc-2A stainless steel plated(tq spec – 27 ft-lb target)-min proof load - 8370 lbs
1 bolt in center- 3/8-16 (3.5 in) unc-2A stainless steel(tq spec – 27 ft-lb target)-min proof load -8716
1 bolt in center– 7/16-14 (3.5 in) unc-2A stainless steel(tq spec – 47 ft-lb target)-min proof load - 9567


Desertfox you saw one of the pic which is been deleted now right.Did that give u an idea about the joint?

 

[preload]

Dimjim,

Yes the hole diameter increases uniformly from under head of the 7/16 bolt to the bottom.

Under the head ID is 0.48 in and the ID of other side of the hole in the picture(3pf9) is 0.58 in. OD is 0.88 in. The depth of the hole in the gear case is 2.71 inch

 

[preload]

Desertfox,

here is the link for the embedment test snaps.

http://img521.imageshack.us/img521/7991/untitledps3.png

Top 2 snaps are the 3/8 perimeter took to proof load
bottom 1 is the 7/16 taken to proof load

does these pics show any signs of embedment? sure we lost paint under the washer which is normal.

 

[desertfox]

Hi preload

I can't see the file till friday I will post then.

regards


desertfox

 

[desertfox]

Hi preload

If you clear the paint away can you feel a step or see a step in the metal surface?


regards

desertfox

 

[preload]

Deserfox,

I looked at the joint and did not find any step or signs of embedment other than the paint scratching off which is normal.

 

[desertfox]

Hi preload

I will look on friday at your picture.
If the paint is getting destroyed during tightening then
the fixing is embedding into the paint work at least.
How did you determine the clamp load by ultrasonic's?

regards

desertfox

 

[desertfox]

Hi preload

Looking at the pics it looks to me that the washer as embedded itself into the material I can see a witness ring
were the washer is on each photo.
But your telling me thats its just the paint work damaged,
well your closer to the component than me, maybe you could try making some joints without paint and see if you get a witness ring under the washer then.


regards

desertfox

 

[adi1]

Desertfox,

For some reason my handle "preload" is not working. It says some registrations problems. So I created a new handle.

Anyway, the witness ring you are seeing is just the washer taking the paint away on the surface. I dint feel or see and step under the washer.

But yes It would be a good idea to run some un-painted parts.