Broken Modern Motorsports billet stub axle

[jbc3]

BLKMGK, I was on the street, no nitrous when it broke. I have run a few (maybe 10-12) tanks of the spray through it over the past couple of years, both on the track and the street.

 

As far as spline engagement, I am running the MM companion flanges (CF) and there was full spline engagement in the CF. The break occurred just inside the CF, right at the edge of the CF splines. The CF is fine and no damage to the splines.

I'll go back and label the pics to help you get a better idea.

 

Jody

[Sven]

Wow, that is a pretty clean break. Fairly impressive destruction. As already said, it's interesting to see where ductile failure began before it twisted right off. A little more than "interesting" for you, I'm sure .

[Modern Motorsports Ltd]

Jody, firstly congrats on your 650 + foot pounds torque! Secondly congrats on being able to put it down as you have! Few build true power and fewer put it down.

 

Gotta be frank and say I’m quite surprised to not have a single note from you etc on this We’ve got 60 prior correspondence items so I know we’re not shy. Good friend just gave me a buzz and just got thru reading your thread. Few comments to address all posters and viewers.

 

• You broke a fine product and it took immense stress to do so;) (can't find that congrats smiley clanging beermugs!)
  
• Launches/burnouts ARE the main stress’s on these drivetrain parts as Jim says (howdy Jim!). It’s shock loads that typically are the critical factors.
  
• Great validity to how high end ¼ milers work so hard for great launches while minimizing shock load through preload methods/fine tuning etc.
  
• It broke at typical failure location for such assembly so not alarming. Between spline engagement and inner bearing, seen it before with Australian pieces by others.
  
• These were not stated as indestructible (addressing one comment made). They are notably stronger than factory pieces and were intended to exchange directly with factory pieces thus retaining factory shaft diameter. This diameter is the limiting factor for strength achievable.
  
• Breakage is not alarming, anything can be broken depending on inputs etc, these aren’t bought for mall trips. 650+ ft-lbs plus 295 slicks plus repeated clutch drops plus 1.4 60 ft’s plus 10 sec ET’s! Pretty unique language more of us wish we were talking! Our Ozzy’s doing sub 1.4 60’s …

• From your pic it appears the actual fracture occurred earlier, possibly at the track and finally let go on your last burnout effort.
  
• Tomorrow a replacement set with flanges is going out to you (5x4.75 right?, possibly Tues as it’s a custom pattern not on shelf).
  
• We’re issuing a call tag for return of your broken stub axle with paired flange and preferably your other stub axle/flange as well. They’re already in queue for a full failure analysis upon their receipt.
  
• Lastly, we do have a next ‘stage’ stub axle upgrade in the works. It’s notably larger in diameter and not a simple plug’n’play but it’ll go into a Z and it’s already withstood 9 second ET’s adapted into a very similar ride. Your own speedracer Rick’s requested this a while back and been a driving reason for it’s creation, HP/TQ figures I was sworn to secrecy on:cool:

Thanks again to all for their support both vocalized and offline! Jody, look forward to hearing from you.

[JustinOlson]

That is a very commendable vendor!!!

[lbhsbZ]

These were not stated as indestructible (addressing one comment made).

 

 

OK, well they looked pretty indestructable when I opened my box

 

Any ETA or details on the "next stage" stub axles? I'm making 500ft/lbs and I've got 315s under the back. I'm not going to be doing any drag race launches, but I'd hate to have one snap doing 160 down a bumpy road course in Mexico.

 

....And kudos to Ross for handling this in the manner he did.

[stony]

One of the reason i went with a solid rearend was to eliminate the weak link ( rearend)

 

No matter how you build it the stub will still only be 27 spline. Thats fine for a car thats in the 350hp mid to low 11 sec time frame. But it will break eventually. One day the track will be especially sticky or something and it will hook extra hard welll you know.

 

I agree with ross it looks like it probably was ready to go before you did the burnout. it looked exactly like my stock 300z stubs did ( the break that is) when i broke 2 set of those :>

 

I think the only way to make them last longer is to run an automatic. Clutch drops are just to harsh!!!

 

 

Anyways. I like the idea of a bigger diameter stub shaft. In my attempt at a stonger rearend i machined the housing to accept bigger bearings. I think if there was a compatable bearing that would fit in the housing and also hold a 31 spline stub that would be the way to go.

 

Not bashing the stubs in fact i commend the effort that was put forth to make them. good job keep up teh good work.

[jbc3]

Wow,

I will thank Ross publicly and appoligize also. I sent him an e-mail yesterday and should have waited for a response. I fat fingered the address.

I re-sent an e-mail through HybridZ this time.

 

I have no ill feelings about the axles and hopefully none of my posts sounded like I had a bad attitiude. Parts break.... period! I was hoping that these wouldn't be the weak point, but as I said several times, I was not gentle.

 

Everything has it's breaking point and maybe this will help get a stronger piece out there.

 

Jody

[sweetleaf]

I'd have to say thats the best response I've ever seen from a vendor.. I'm definately going to have to go with his parts for my build... Very Commendable.

[Daeron]

I'd have to say thats the best response I've ever seen from a vendor.. I'm definately going to have to go with his parts for my build... Very Commendable.

 

I also say thats a good response from the OP.

 

Can you feel the love?

[Mikelly]

You know, Sometimes I just don't get some of these responses... Especially some of the "reactions".

 

Jody, You broke a part and posted pics and your experience... You didn't trash Ross, or his product. In my mind you owe nobody an apology. If one is expected from the other side of the fence, well...

 

Mike

[Pop N Wood]

That part looks like it gave plenty of warning it was failing.

 

Can't help but feel if you had been an advocate of JohnC's monthly race car inspections you would have found it before it went.

 

I guess if you want to run with the big boys you have to play like them.

 

Good to know what the failure point is.

[johnc]

As Ross has said, despite the better metallurgy and maufacturing, its still just a 27 splint sub axle originally designed for a 2,800 lb. 150 horsepower 280Z.

 

Again, the part began ito fail long before it actually went BANG! A stress riser started at a surface imperfection and then propogated in steps as the stub axle was subjected to load. Some of these were small steps, some of these were big steps. Finally, the last burnout induced a step in the cracking processes that took the strength limit of the part below the load it was experiencing. BAM!

 

Shot peening and polishing will reduce the surface imperfections and help reduce these kinds of failures.

[johnc]

BTW... there is no such thing as a failure free race car. Even Audi, with their $550M Le Mans race budget designed their R8s and R10s so that the rear half of the car (including the transmission, brakes, suspension, wing, bodywork etc.) could be removed and replaced in 6 minutes.

[JMortensen]

BTW... there is no such thing as a failure free race car. Even Audi, with their $550M Le Mans race budget designed their R8s and R10s so that the rear half of the car (including the transmission, brakes, suspension, wing, bodywork etc.) could be removed and replaced in 6 minutes.

Speaking of Audi and their Le Mans team, they damaged what I suspect in the R10 would be called the stub axle in the race, which caused the wheel to exit the vehicle at 190+ mph, taking the lead car out...

[jbc3]

Here is a picture of both the broken stub axle and the "good" one together. It will help show exactly where the break occurred.

 

[BLKMGK]

Picture helps a great deal, thanks!

 

I asked about the nitrous because of the extreme torque rush that occurs when activated. That on top of everything else (been running them for years??) just added up. I'd also agree that an inspection would probably have caught this but yeah that is a PITA and I'd probably not have done it either

 

Glad to see Ross is on this and that he has plans for something even stronger in the works as it seems some of us are certainly going to need it. The failure analysis, which I hope he shares, could prove enlightening. Looking at it and "guessing" that's pretty much where I think most would think it would break so not a big shocker that it did. A straight axle could certainly fix this once and for all but man that's a pile of work! I'm still waiting for a bolt-in R30 mount (lol). Hopefully other folks who have been abusing these axles hard will inspect them and this will turn out to be a fluke...

[v8dats]

i think it was of inferior material!!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

it should have been made from kryptonite! even superman cant mess with that!

just kidding guys dont kill me!

parts fail!

[nat0_240_chevZ]

can you take an end view shot, sort of angled down to look squarely at where the failure would occur on the good (well nearly farked) stub (similar shot but from the left side of the last posted pic.), think i have identified an area ross can improve on, if he hasnt done so already.

 

looks like the spline cutting comes to a point near/where the splines end, i can see somewhat a rad there but if the spline suddenly finnishes at a sharp point then this would definately a stress raiser.

im able to do a full FEA analisys of the stubs if Ross would allow the stubs to be CAD/CAM modelled or something similar, but of the resultant manufactured item, not the design, as manufacturing is a leg and an arm away from our original design usually. Will need some more details but, engine torque, rear end ratio, 1st gear (or launch gear if you launch i 2nd)

rough amount of hard launches etc etc etc.

 

let me know

nato

[DemonZ]

You know, Sometimes I just don't get some of these responses... Especially some of the "reactions".

 

Jody, You broke a part and posted pics and your experience... You didn't trash Ross, or his product. In my mind you owe nobody an apology. If one is expected from the other side of the fence, well...

 

Mike

 

 

 

I totally agree, and I for one appreciate news hitting the board first, in it's un-edited purity. Obviously such happenings would be better for business taken off line, but I don't think that's in the spirit of the board (I could be wrong). Being an enthusiast, while I do care if it's the best product out there, I care even more if there's been a documented breakage. We all like making informed decisions, isn't that what sites like this are all about?

 

 

Hopefully others won't feel as if they shouldn't speak up about product limitations...

[deja]

Bummer and it is surprising for sure. Then again your car is a beast and these have no doubt been stressed more than once. Even the pro's break stuff that cost more than our cars, nothing lives forever.