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What is wrong with this picture?

9K views 51 replies 26 participants last post by  David Taylor 
#1 ·
Simple question, what is wrong in this pic?



And Another:



And Another?



Hmmm - I see a pattern here...



And racers wonder why some of these HUGE axle keep breaking??



Basic Engineering Mistake in all of them.....

Come on, let it fly....
 
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#5 ·
Nice Weasel. Speedway Engineering also cuts to the proper diameter from my experiences.


Speedway also has gundrilled shafts. What's everyones opnions on gun drilled? We had a couple fail and pictures will be below, but heres my opinion: It looks like the shaft was well engineered, and almost the entire length of the axleshaft bent and fractured in absorbing torque before the splines sheared off in the differential. This is where gun drilling makes me wary, we had two axle shafts fail in a similar overall fasion. I don't think the gun drilling made the shaft significantly weaker, but I believe it changed the mode of failure. I think the gun drilling caused it to fracture vertically as shown, and bend as it did. That bend can be (and was) disastrous. One broken shaft we were able to get out with a mini sledge hammer, the other took a torch, full sized sledge and two hours to pull out of the housing, destroying a spindle in the process.

I like the ability to quickly replace shafts, it seems the mode of failure with gundrilled shafts can make that difficult.

Look at the vertical seperation of the splines at the crack


 
#9 · (Edited)
Nice Weasel. Speedway Engineering also cuts to the proper diameter from my experiences.

Speedway also has gundrilled shafts. What's everyones opnions on gun drilled?
Looks like something is bent, like housing?? The only real benefit to gun drilling is some reduced weight. Since most of your shaft stresses are at the surface you can remove the core without significantly reducing the strength of the shaft. There was some previous discussion on gun drilling relieves some of the material stresses at the center but I haven't really read much on that aspect. It doesn't fix the spline/profile issue.
 
#10 ·
whoops



Whoops, was not aware...

I cannot believe that companies are still doing this and advertising it on their website???
 
#13 ·
maybe it's already been said, I don't know the lingo, but when cutting splines aren't you supposed to offset where they end on the shaft.
Not sure how to word it properly, obviously they all start at the outer most part of the shaft, but shouldn't they then be cut varying depths into the shaft.
IE 3.0"-3.1"-3.2"-3.3"-3.4"-3.3"-3.2"-3.1"-3.0" repeat... so there isn't a common spot where all the splines stop.
 
#14 ·
I've seen that done. I personally don't see that it makes any significant difference. A shaft that isn't necked down breaks at the end of the side gear or drive flange, not the end of the splines.
 
#19 ·
Billavista



My apologies that I have obviously posted something that has been discussed heavily before, but I was frustrated race suppliers and manufacturers all over the world manufacture, promote and sell axles with the most basic of engineering flaws and a lot of it makes it's way down here to australia and the poor racer has no idea why his super expensive 300M axle snapped in half and the manufacturer sells him another one exactly the same...

Again, apologies, new to the forum and was only trying to vent my frustrations...



Further reading - lots of references to Carol smith's engineer to WIN - well done billavista... I have a lot of reading to do on the billavista site...

Pirate4x4.Com - Extreme Four Wheel Drive

Another silly thing, we had previously purchased some 35 spline "super strong" series 21 CV stars to increase the size of our front axles. When we received them, the manufacturer had machined the splines in the star to suit a 60 degree involute spline instead of the shallower, stringer, more common 90 degree involute spline. The grooves in our axle splines ended up much deeper (due to the sharper angle of the spline) and by the time we machined lots more off the minor diameter to reduce the stress in the above photo, the minor diameter of the HUGE 35 spline axles ended up similar to the minor diameter of the old 33 spline 90 degree involute spline.

Is it just me finding these problems??? or has the industry lost all the old grey haired engineers that used to know how to make good stuff.

there are some good manufacturers out there that make some really nice stuff, but it takes a lot of searching...



 
#39 ·
Another silly thing, we had previously purchased some 35 spline "super strong" series 21 CV stars to increase the size of our front axles. When we received them, the manufacturer had machined the splines in the star to suit a 60 degree involute spline instead of the shallower, stringer, more common 90 degree involute spline. The grooves in our axle splines ended up much deeper (due to the sharper angle of the spline) and by the time we machined lots more off the minor diameter to reduce the stress in the above photo, the minor diameter of the HUGE 35 spline axles ended up similar to the minor diameter of the old 33 spline 90 degree involute spline.
I may be getting a bit lost in the terminology here. I'm assuming that by "60 degree involute spline" you are referring to "30 degree pressure angle"? Likewise, "90 degree involute spline" implies 45 degree pressure angle? Or, is it a different animal altogether?
 
#22 ·
X2

Cutting/rolling/etc splines into a solid finished bar is MUCH cheaper to mass produce than turning down the ENTIRE bar to the minor diameter, and THEN treating the bar.


Since you posted pics from RCV, in their "defense":confused: , the joint will usually break before the shaft.

That is also usualy the case for (mass producted) U-joint style shafts that are manufactured in the same way also.


CTM and Cone build stuff properly FYI. And, you pay$$ for that likewise.
 
#21 ·
"has the industry lost all the old grey haired engineers that used to know how to make good stuff."

Yep


And to rant; If I say something is a bad idea then I'm not expirienced and time-served, but I am person who needs to become a "team player" :rolleyes:

Grey haired engineers rant over :D
 
#32 ·
Im probably the least knowledgable in this thread. From what I understand:

Rolled splines are better than cut splines.
Proper wasting is better than dia of shaft same as major spline dia
Gun drilling actually does more than save weight, BUT, you need a min "x" dia before it starts to be noticable, ie a 25mm shaft may get no structural benefit from it.
Materials and heat treating play a huge roll.

I have read over the years that some manufactures actually think the non wasted design stronger :confused:

Surface finish, if applied in an appropriate mannor is also functional. I could be wrong, but I thought shot blasting to align grain structure and polishing to reduce the starting points of stress risers.

radius transtion is also important....and if running unequal length axles, their individual design would vary slightly to give equal strength.

Then again, I could be heavily uninformed :homer:
 
#41 ·
Serg, basically this post is a summary of " what to do" steps of how things should be done. Unfortunately some key points are overlooked to save production costs & keep up with demand.
I used to roll threads on large ram equipment. We used a conventional large lathe & yes it took serious loading on the tool to do the job.


brooksy
 
#37 · (Edited)
We just make them ourselves. That way I know what I am getting. I think that I would buy from USGEAR if I had a TT and used standard stuff, but my gear is a bit unusual with all the floater hubs, custom made CV's etc.

We evan make our own CV's now - Ones that are ALL one piece and have the bearings fitted on them as the drive flange...

See the cutaway...

http://sphotos-e.ak.fbcdn.net/hphotos-ak-ash3/539904_443587529021776_455032945_n.jpg

We have a digital hardness tester and we watch our heat treatment lads pretty closely, but they dont usually let us down.

I would love to have access to a Spline Rolling Machine, but hey, we are only a small shop... Rolled splined and Gun Drilled Axles, lovely...

These guys use COLD ROLLING to produce their splines - the forces to create the splines must be amazing..



I really like the US gear stuff also...

 
#36 ·
I broke2 RCV shafts in one trip with a vortex v6 running on 5 cylinders.

Does that help your cause?
 
#50 ·
Wouldn't it be great if axles (most) always broke at the hub instead of the diff. Most manufacturers have spoken, and the ones that do it right are not heard.

Pirate readers like to get informed and share!

Some use the locking hub as a fuse, but good to know the upper end...

Bigger diffs and axles are not the best answer (for a racer) if materials and design can do it otherwise. (Of course I am not going to pop for a Robby G R&P for $40k, either.)
 
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