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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 01-17-2017, 05:57 AM   #15
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Originally Posted by wparsons View Post
How would the joint (which is supported and bolted to the body) be a point of failure that would allow the engine to drop?
Like this:


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Originally Posted by Captain Snooze View Post
Ok, here is my not quite sober reply. I have to preface this by saying this is an un-informed opinion.
My impression of cf is that it is incredibly strong for the loads it is designed for and quite fragile otherwise
In longitudinal direction, in case of o tube or similar - now allow me to simplify - almost everything is relatively strong. Even a piece of paper rolled into a tube is quite strong like that.
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Old 01-17-2017, 06:34 AM   #16
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Like this:
Yep, sure (and I am quite sober now thanks!) but I am going to invoke the low risk/ high impact won't happen to me clause.

Yes, there is the chance that in an incident the cf tail shaft is going to cause increased injury because it is not going to fold like the 2 piece tail shaft.

But [1] I am going to ignore the the risk because it won't happen to me.[2]



1. Yes, I have started a sentence with a conjunction.
2. That is, knowing full well that incidents happen all the time but I/we are excellent creatures at dismissing data that doesn't suit our reality. "Pfffft... Head-on collisions? Who cares! I have a cf tail-shaft!"


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My car is completely stock except for all the mods.

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Old 01-17-2017, 09:31 AM   #17
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Pitty that adding extra joint for CF shaft will further rise it's price and weight, making it even harder decision to buy, so probably will not be done by any aftermarket shaft maker.
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Old 01-17-2017, 10:53 AM   #18
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Hey Eric!

What about high RPM Vibrations?

I would really like a lightweight driveshaft, but how good will it be going more than 200kp/h on the german Autobahns for al longer time?

Im mean round 125mph for more than 15min.

Last edited by Falcon; 01-17-2017 at 11:08 AM.
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Old 01-17-2017, 11:44 AM   #19
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Nice work! I heard a rumor about this a while back...glad to see it out!

Now, for the topic of crashing, (although @VeloxEric should this be its own thread to prevent further derailment of this thread?)
what makes you guys think the stock two piece is (1) going to bend down in an accident and not up? (2) Where is the info specifying that the stock driveshaft is a two-piece because of accidents and not NVH? Or simply cost?


fwiw, I have an aluminum driveshaft, so I guess if I get in an accident and become a human kabob I'll report back.
*knocks on wood lol

@Falcon since the driveshaft is balanced properly, it won't matter if you hit 125mph for 1 minute or 100
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Old 01-17-2017, 12:30 PM   #20
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continuecrushing: even if it will bend up or to sides, not much difference, as it's where center console is, i guess main point is that it will bend & won't act as extra support keeping engine in place. Also direction of bending might depend on things like if it already is at slight angle and what/how are it's supports made and where/how engine will start to move initially by front & body crumple zones & mounts design.
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Old 01-17-2017, 02:11 PM   #21
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Originally Posted by JDM4E View Post
One question I always had about these pieces - does this compromise safety at head-on crash? Our car has 2-piece shaft with a joint, and IIRC this joint is designed as a point of failure during crash, so the engine can slide "under the cabin".
My concerns are about road-use since this will be super strong piece.
Thanks.
I was always under the assumption this was for NVH and costs but it could be for safety as well? I honestly have no idea.

No manufacturer of a one piece driveshaft will be testing a driveshaft in a head-on collision fashion, it's far too expensive. So I cannot comment beyond my speculation, which is below. But being a speculation, it is an opinion and from past experiences... not data.

The carbon tube would likely break in a compression loading scenario. I don't see a carbon tube surviving a crash if the engine gets pushed backward in the chassis. Carbon has great strength to weight but it does not buckle and remain intact like steel does when loaded past its yield strength.

Personally, what I see happening if this were to happen, would be the carbon tube disintegrating. Honestly, this would be much safer than a steel or aluminum shaft going downward into the concrete or upward into the cabin. Regardless, I believe the engine would be pushed backward "as designed" from the manufacturer. That's to say the manufacturers even design an engine to move rearward in a head-on collision... I have no idea what failure modes they assume, account for, and try to improve upon...

Regardless, do whatever you feel comfortable with and feel safe doing. I don't have the exact answer for you, beyond what I state above from my experiences with carbon and failure modes.

Thanks,
Eric

Quote:
Originally Posted by Falcon View Post
Hey Eric!

What about high RPM Vibrations?

I would really like a lightweight driveshaft, but how good will it be going more than 200kp/h on the german Autobahns for al longer time?

Im mean round 125mph for more than 15min.
You should be fine .

Thanks,
Eric
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Old 01-17-2017, 03:24 PM   #22
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Thanks, thats a fair and honest answer.
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Old 01-17-2017, 04:16 PM   #23
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This isn't exactly the same scenario as an automobile accident, but is interesting nonetheless.

[ame="https://www.youtube.com/watch?v=KZnUp62cN4s"]carbon tube compression test[/ame]
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Old 01-17-2017, 04:19 PM   #24
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This isn't exactly the same scenario as an automobile accident, but is interesting nonetheless.
Your link showed up weird on my end.... but I copied the link and watched it. Edit: Forum fixed itself or you did .

THAT IS COOL!

I wish they gave more information like wall thickness, composition, weight... not really informative but super cool to watch.

Thanks,
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Old 01-17-2017, 04:43 PM   #25
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Quote:
Originally Posted by Falcon View Post
Hey Eric!

What about high RPM Vibrations?

I would really like a lightweight driveshaft, but how good will it be going more than 200kp/h on the german Autobahns for al longer time?

Im mean round 125mph for more than 15min.
Touched on in the OP.
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Old 01-17-2017, 04:45 PM   #26
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Quote:
Originally Posted by continuecrushing View Post
Nice work! I heard a rumor about this a while back...glad to see it out!

Now, for the topic of crashing, (although @VeloxEric should this be its own thread to prevent further derailment of this thread?)
what makes you guys think the stock two piece is (1) going to bend down in an accident and not up? (2) Where is the info specifying that the stock driveshaft is a two-piece because of accidents and not NVH? Or simply cost?


fwiw, I have an aluminum driveshaft, so I guess if I get in an accident and become a human kabob I'll report back.
*knocks on wood lol

@Falcon since the driveshaft is balanced properly, it won't matter if you hit 125mph for 1 minute or 100
The direction of deformation is predicted and even dictated but the fixed angle the joint is set at.
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Old 01-17-2017, 04:57 PM   #27
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Originally Posted by VeloxEric View Post
I was always under the assumption this was for NVH and costs but it could be for safety as well? I honestly have no idea.

No manufacturer of a one piece driveshaft will be testing a driveshaft in a head-on collision fashion, it's far too expensive. So I cannot comment beyond my speculation, which is below. But being a speculation, it is an opinion and from past experiences... not data.

The carbon tube would likely break in a compression loading scenario. I don't see a carbon tube surviving a crash if the engine gets pushed backward in the chassis. Carbon has great strength to weight but it does not buckle and remain intact like steel does when loaded past its yield strength.

Personally, what I see happening if this were to happen, would be the carbon tube disintegrating. Honestly, this would be much safer than a steel or aluminum shaft going downward into the concrete or upward into the cabin. Regardless, I believe the engine would be pushed backward "as designed" from the manufacturer. That's to say the manufacturers even design an engine to move rearward in a head-on collision... I have no idea what failure modes they assume, account for, and try to improve upon...

Regardless, do whatever you feel comfortable with and feel safe doing. I don't have the exact answer for you, beyond what I state above from my experiences with carbon and failure modes.

Thanks,
Eric



You should be fine .

Thanks,
Eric
Id like to put a little insight into the crash scenario and factory driveshaft design. I work in the collision industry. My dad and i run a body shop, and frankly put, if you are in a hard enough collision to worry about the driveshaft puncturing the occupant area, thats going to be the least of your worries. The other damage caused by that violent of an impact would have either long since killed you, ejected you, or if your lucky survived but in critical condition.

The front structure of our cars and other modern cars are designed to deflect an impact outward and around the occupant area. For the engine/transmission to have moved far back enough for the driveshaft to deflect from its mount point, puncture the occupant area and cause bodily damage is a substantial amount and would be measured in feet, not inches. My guess is the engine would come through the firewall before the driveshaft would reach a point to cause harm to the occupants.



Now with all that being said im genuinely excited about this. I fully intend to stay NA with my car and any and all reductions in rotating mass tickle my fancy. I love the attention to detail and clarity you provide about your products.
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Old 01-17-2017, 05:01 PM   #28
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Id like to put a little insight into the crash scenario and factory driveshaft design. I work in the collision industry. My dad and i run a body shop, and frankly put, if you are in a hard enough collision to worry about the driveshaft puncturing the occupant area, thats going to be the least of your worries. The other damage caused by that violent of an impact would have either long since killed you, ejected you, or if your lucky survived but in critical condition.

The front structure of our cars and other modern cars are designed to deflect an impact outward and around the occupant area. For the engine/transmission to have moved far back enough for the driveshaft to deflect from its mount point, puncture the occupant area and cause bodily damage is a substantial amount and would be measured in feet, not inches. My guess is the engine would come through the firewall before the driveshaft would reach a point to cause harm to the occupants.



Now with all that being said im genuinely excited about this. I fully intend to stay NA with my car and any and all reductions in rotating mass tickle my fancy. I love the attention to detail and clarity you provide about your products.
I enjoy learning things! Thanks for your insight.

Thanks,
Eric
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