Ad: VTT "Spline Lock" Crank Hub Solution Now Available!

fmorelli

Brigadier General
Staff member
Aug 11, 2017
2,864
Virginia
I'd love t see a photo and whatever @GhassanAutomotive and @[email protected] folks determine.

The difficulty with this situation is that a traditional solution is a keyway. That solution is well known - no amount of R&D and testing will supplant the 50+ years of experience running that solution with high horsepower motors. Period. But that said, one can get that solution ... and the cost in the case of our cars, that solution is fairly expensive.

The VTT spline lock is an alternative approach, at far less cost, which can be installed without having the motor apart, etc. It can't be as bulletproof as a keyway solution - obvious to anyone that thinks about it for 50 milliseconds - simply because ... until the spline lock has trek'd the kind of years and abuse stats that the key has ... just can't say with the same level of certainty - and this is a conversation about certainty (failure rates), nothing else. I think the practical question at this point is, as a choice between doing nothing and spending $$$ on a key solution (someone chime in and say how much it costs to get a key solution on an existing built motor) ... is the spline lock a worthwhile consideration? Probably not as bulletproof as a key, I surmise, but this is a trade-offs issue. That seems like the practical place to land - and it would be interesting to see what happened in the Ghassan case.

Filippo
 

Bnks334

Sergeant
Dec 1, 2016
486
New York
Seems odd to claim the crank bolt can "back out" from vibration considering the crank spins clockwise and applied torque should be acting to tighten the crank bolt. That is how I thought it works anyway. I'd lean toward either improper installation of the crank hub bolt in the first place or the splines didn't work as intended. Maybe the interference fit of the spline lock isn't enough? I'd think testing would've figured that out though.

Edit: thinking about this more, the two-piece design of the crank/hub might actually mean the torque of the crank acting on the hub is actually constantly trying to un-screw the hub?

How difficult is it to drive this splined hub into the crank snout? Did VTT do any testing to see how much initial torque it takes to bottom out/seat the crank bolt/hub before the user begins their final stretch of the crank hub bolt? Could the mistake have been that there was so much torque required to drive the splines into the crank that the crank bolt never actually got stretched as intended?

As an example, I am thinking of the kind of resistance/torque you get on a bolt when you drive it in cross-threaded... It then becomes hard to tell if the bolt has bottomed out and it seated or you're just seeing a lot of resistance from creating your own new threads lol...
 
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The Convert

Captain
Jun 4, 2017
1,343
Jeff, could have sworn you asked for a photo months ago and I had it posted, not sure where that went but here it is again.
That’s interesting for sure. As the splines are cut by the splock, they don’t look as clean as a tool broached spline. So, getting consistent pressure face area from crank to crank, install to install, could be a potential failure point. I wonder if a tool could be made that could do the broaching in the car that you would remove and then fit the splock. Or Two or three successive tools for a more consistently sized pressure face.
 
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fmorelli

Brigadier General
Staff member
Aug 11, 2017
2,864
Virginia
That's an interesting idea. For instance, the cutting tools would be a steel significantly harder than the hub face. Maybe they cut by a threaded assembly to the crank, which progressively walks them in and back out. Maybe removing material just several thou shy of the spline?

Filippo
 

GreyNBlueE92

Corporal
Oct 3, 2018
154
OH
Maybe there wasn't enough material in between the splines for them to dig into. Being that the crank was so soft when compared to the splock, I would think there would need to be more material in between the splines to make up for the (lack of) hardness of the crank.
 

veer90

Lieutenant
Nov 16, 2016
973
West Nyack, NY
So the metallurgy from the test / shop car piece is likely different than the production units.

The splines on Ghassan's hub looked like someone smashed the shit out of them. They're too soft.
 
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Bnks334

Sergeant
Dec 1, 2016
486
New York
So the metallurgy from the test / shop car piece is likely different than the production units.

The splines on Ghassan's hub looked like someone smashed the shit out of them. They're too soft.
I would think the splines will look smashed lol, they are being driven into the crank in an interference fashion... What the above picture shows is the grooves the splines cut into the crank... it doesn't show the splines of the hub post install at all. I would imagine it would not look re-usable.

And if Ghassan spun the hub then of course even further the splines on the hub will be destroyed.

The question I still have is was a new seating torque determined? It's very possible the crank bolt wasn't yielded correctly.
 
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Oct 24, 2016
1,111
Scottsdale, AZ
We received one photo from Ghassan, it looked like the splines laid down for one reason or another. Unfortunately we haven't been able to see the product, photos of mating surfaces, etc. Bummer. Based on that limited feedback there is only so much we can postulate on, obviously the splines shouldn't lay down, so something was off, but it's going to just be guesswork until we get the piece back -it'd be easy to inspect, analyze make sure material properties are what they ought to be, and go from there.
 

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