Crank Bolt Capture

[M2_MEDUSA]

Originally Posted by MineralWhiteF80

I'm well aware of the claims of what it is supposed to do. Can you elaborate on exactly how? The bolt can still back out with a CBC installed because there is still nothing preventing the crank bolt threads from turning (loosening) inside the crankshaft. Instead of the crank bolt spinning at its own rate, it will just make the crank hub and pully spin along with the bolt at the same amount while still loosening from the crankshaft.

A hexoganol shapped socket is fitted over the bolt and the cbc is torqued with multiple bolts holding it in place, only way for the bolt to back out would be if every single bolt holding the cbc to the crank simultaneously snapped in half

[MineralWhiteF80]

Originally Posted by M2_MEDUSA

A hexoganol shapped socket is fitted over the bolt and the cbc is torqued with multiple bolts holding it in place, only way for the bolt to back out would be if every single bolt holding the cbc to the crank simultaneously snapped in half

The CBC does not bolt to the crankshaft, only through the pulley and into the crank hub body. You can still remove the crank bolt from the crankshaft without breaking any of the CBC bolts. All the CBC is doing is sandwiching the crank bolt between the main crank hub body and dampener pulley forming one solid assembly, all of which are still not connected to anything other than the crank bolt threads that are touching the crankshaft. It would just all spin as one assembly rather than just the bolt spinning and the pulley/crank hub trying to stay in place due to the force of the serpentine belts holding them.

You can still loosen (remove) the crank bolt from the crankshaft even with the pulley and crank hub fastened to the crank bolt. For example: if the CBC capture (like the Kies Motorsport version) has a 32 mm hex head built into the CBC, after everything is installed and running properly, you could still put a 32 mm socket on the Kies CBC and unscrew the entire fixed hub assembly (OEM hub/bolt/pulley/CBC) out of the end of the crankshaft.

I'm trying to understand why the crank bolt is less likely to loosen from the crankshaft by locking the bolt onto dampener pulley and OEM factory crank hub using a CBC. Does the increased mass of the new four-part rotating hub assembly cause enough extra resistance against the timing chain shock load to make it harder for the crank bolt to vibrate loose?

[Track/S]

Originally Posted by MineralWhiteF80

The CBC does not bolt to the crankshaft, only through the pulley and into the crank hub body. You can still remove the crank bolt from the crankshaft without breaking any of the CBC bolts. All the CBC is doing is sandwiching the crank bolt between the main crank hub body and dampener pulley forming one solid assembly, all of which are still not connected to anything other than the crank bolt threads that are touching the crankshaft. It would just all spin as one assembly rather than just the bolt spinning and the pulley/crank hub trying to stay in place due to the force of the serpentine belts holding them.

You can still loosen (remove) the crank bolt from the crankshaft even with the pulley and crank hub fastened to the crank bolt. For example: if the CBC capture (like the Kies Motorsport version) has a 32 mm hex head built into the CBC, after everything is installed and running properly, you could still put a 32 mm socket on the Kies CBC and unscrew the entire fixed hub assembly (OEM hub/bolt/pulley/CBC) out of the end of the crankshaft.

I'm trying to understand why the crank bolt is less likely to loosen from the crankshaft by locking the bolt onto dampener pulley and OEM factory crank hub using a CBC. Does the increased mass of the new four-part rotating hub assembly cause enough extra resistance against the timing chain shock load to make it harder for the crank bolt to vibrate loose?

Anyone who understands a bit of mechanics knows that the cbc is rubbish and is useless, the one who made it thinking that it will save the turn must be a former baker.

[theweebabySeamus]

If it works, it works.

[fivaxis]

Originally Posted by MineralWhiteF80

I'm well aware of the claims of what it is supposed to do. Can you elaborate on exactly how? The bolt can still back out with a CBC installed because there is still nothing preventing the crank bolt threads from turning (loosening) inside the crankshaft. Instead of the crank bolt spinning at its own rate, it will just make the crank hub and pully spin along with the bolt at the same amount while still loosening from the crankshaft.

That would require an amount of torque that will never be reached.

[fivaxis]

Originally Posted by MineralWhiteF80

The CBC does not bolt to the crankshaft, only through the pulley and into the crank hub body. You can still remove the crank bolt from the crankshaft without breaking any of the CBC bolts. All the CBC is doing is sandwiching the crank bolt between the main crank hub body and dampener pulley forming one solid assembly, all of which are still not connected to anything other than the crank bolt threads that are touching the crankshaft. It would just all spin as one assembly rather than just the bolt spinning and the pulley/crank hub trying to stay in place due to the force of the serpentine belts holding them.

You can still loosen (remove) the crank bolt from the crankshaft even with the pulley and crank hub fastened to the crank bolt. For example: if the CBC capture (like the Kies Motorsport version) has a 32 mm hex head built into the CBC, after everything is installed and running properly, you could still put a 32 mm socket on the Kies CBC and unscrew the entire fixed hub assembly (OEM hub/bolt/pulley/CBC) out of the end of the crankshaft.

I'm trying to understand why the crank bolt is less likely to loosen from the crankshaft by locking the bolt onto dampener pulley and OEM factory crank hub using a CBC. Does the increased mass of the new four-part rotating hub assembly cause enough extra resistance against the timing chain shock load to make it harder for the crank bolt to vibrate loose?

To loosen it with the crank bolt capture still attached like you are describing would take 2 to 3 times as much torque at least. Without it you are just dealing with the torque of the tightened fastener. With the CBC, you are adding the torque it would take to rotate the hub (the amount of torque it would take to spin the hub while it is properly torqued down). Now add those together and it’s a lot more than just the torque of the bolt.

[MineralWhiteF80]

Originally Posted by fivaxis

To loosen it with the crank bolt capture still attached like you are describing would take 2 to 3 times as much torque at least. Without it you are just dealing with the torque of the tightened fastener. With the CBC, you are adding the torque it would take to rotate the hub (the amount of torque it would take to spin the hub while it is properly torqued down). Now add those together and it’s a lot more than just the torque of the bolt.

Thanks for your reply! The concept you are explaining is the level of detail I am interested in and is something I can get behind. Without having the parts in my hand, it's hard to understand the surfaces and materials at play.

What you are saying is that without the CBC, the only thing preventing the crank bolt from loosening is mainly due to just the crank bolt's tension (underhead friction and thread friction).

By adding a CBC and locking the crank bolt's head to the main crank hub body together, you are now increasing the total clamp load of the crank hub assembly by adding the crank bolt's friction PLUS the friction provided by the joint compression of the crank hub body, cam sprocket, oil sprocket, and grip discs in between each part, which will require more effort to break loose all joints at the same time.

In summary: Increasing the total clamp load of the joint using a CBC will make it harder for the crank bolt to loosen, thus reducing the likelihood of joint failure (hub slipping). The amount of force being applied to the crank hub joint by the engine valvetrain, clutch, etc. by either a stock or modified car can be large enough to overcome the complete OEM factory design/torque spec, but may not be enough to overcome the new higher clamp load of the joint when a CBC is installed. The hub could still slip even with the higher clamp load, but that typically comes in the form of a higher horsepower or really extreme driving application. At that point, a keyed/pinned/splined hub is the only option to prevent the failure.

[TopJimmy]

Guys…think about it this way:
Regardless of a stock hub (3 piece) or a pinned hub fix (2 or 1-piece) it's still the hub bolt torque+stretch holding the assembly together (hub, sprockets and crankshaft). Obviously we don't want any slippage between these parts, either from under torque of the fastener (bolt) or from over torque of the assembly (kickdown, over rev, money shift, etc). Let's set aside the "what causes the slip?" and focus on "what slips?"…

If there is slippage it's going to be the weakest link, and the hub bolt has the smallest diameter of its gripping surfaces. The bolt flange face against the outer hub face, and the bolt threads are the two areas experience the most leverage towards slipping.

Using a capture plate to hold the bolt head in position against the hub face locks it from slipping relative to the hub. Now the hub bolt can only move inside the crank if the hub moves, so the next weakest links are the hub sprocket washers. These show that properly crushed friction washers hold up to use of around 700-750TQ, but the exact number isn't yet known on our forum. Someone would need to be in the middle of "dyno revisions" with their tuner, where they knew the HP/TQ from a previous run, then their tuner upped their sauce, and a failure happened on the next run.

Also keep in mind that during money-shifts the torque shock runs from the upper valve train down the chain drive to the inner hub sprocket. On a stock hub these sprockets are small in size/mass compared to the hub. Using a fixed hub causes the shock to run into the hub, and the larger mass helps absorb the force better.

I'm not a scientist…but I did stay at a Holiday Inn Express last night!

[MineralWhiteF80]

Originally Posted by TopJimmy

Guys…think about it this way:
Let's set aside the "what causes the slip?" and focus on "what slips?"… If there is slippage it's going to be the weakest link, and the hub bolt has the smallest diameter of its gripping surfaces. The bolt flange face against the outer hub face, and the bolt threads are the two areas experience the most leverage towards slipping.

Thanks TopJimmy!, I agree with your theory. I am mostly interested in the "what slips?" so that I have a better understanding of the situation and why installing a CBC onto the stock OEM crank hub would be of any benefit. I dont want to blindly install something that would not benefit me at all, just because a lot of people are saying "hey, better than nothing!"

[Track/S]

Originally Posted by MineralWhiteF80

Thanks TopJimmy!, I agree with your theory. I am mostly interested in the "what slips?" so that I have a better understanding of the situation and why installing a CBC onto the stock OEM crank hub would be of any benefit. I dont want to blindly install something that would not benefit me at all, just because a lot of people are saying "hey, better than nothing!"

if you had a hub in your hand you would understand.

What really interests me is who was the engineer who decided not to use locked hub, because I have seen so many different ways to block it that sometimes I think the engineer on the day of the construction of crankshaft was drunk.

The CBC is a waste of time and money.

[TopJimmy]

Originally Posted by Prodrive_X

if you had a hub in your hand you would understand.

What really interests me is who was the engineer who decided not to use locked hub, because I have seen so many different ways to block it that sometimes I think the engineer on the day of the construction of crankshaft was drunk.

The CBC is a waste of time and money.

Should I go get my stock hub out of the box in my garage? I'm pretty familiar with it.

The reason they didn't use a locked hub is because they engineered in the failure point. If the sprocket slips then the VANOS and Valvetronic have a chance to save the engine. If the timing chain breaks it typically gets chewed up inside the engine case, and the engine has to completely stop for the chewing to end.

[Track/S]

Originally Posted by TopJimmy

Should I go get my stock hub out of the box in my garage? I'm pretty familiar with it.

The reason they didn't use a locked hub is because they engineered in the failure point. If the sprocket slips then the VANOS and Valvetronic have a chance to save the engine. If the timing chain breaks it typically gets chewed up inside the engine case, and the engine has to completely stop for the chewing to end.

I did not understand your comment, if the sprocket slips, there is a possibility that the engine can be saved, if the chain breaks the engine chews the chain until it stops, if the hub is locked is something different going to happen if the chain breaks?


The sprocket spuns not because the screw loosens, you can weld it if you want against the hub, it will rotate anyway.

I know it because I work with turbochargers and the same thing happens with them, for this reason in some racing turbos the shaft of the turbine wheel before the thread are hexagonal or triangular, and in the compressor wheels they have the same shape, in this way it remains fixed on the shaft and can never rotate about it and cause unbalance.

[theweebabySeamus]

Originally Posted by Prodrive_X

if you had a hub in your hand you would understand.

What really interests me is who was the engineer who decided not to use locked hub, because I have seen so many different ways to block it that sometimes I think the engineer on the day of the construction of crankshaft was drunk.

The CBC is a waste of time and money.

I might agree if it actually was much time or money. Lol

[Track/S]

Originally Posted by theweebabySeamus

I might agree if it actually was much time or money. Lol

"Hey, better than nothing"

[biigcj]

Since I never found an answer to this when I looked- I’ll help you out. The vendors certainly have more experience than me but keep in mind, they also are in the business of selling parts.

I have been running the VTT crank hub bolt capture for about ~1500 miles now on stage 2 BM3 and e30 tune (depending on my moods) with ZERO issues. I don’t launch the car but frequently let it have it from a roll for fun. I’m in a 16’ f82 DCT with 10k miles, and rarely let the car kick down unless overtaking but love to push the car to the limits.

My buddy also runs the VTT capture on his f80 DCT and has for ~20-25k miles. This guy BEATS on his car, full e85 tune, digs, rolls, slicks, you name it, and has never had a single issue since he tuned it at 40k miles.

Two cases among many others on the forums with absolutely zero issues because of the capture. Can we say it for sure solves it? No. But it certainly seems to help.

[M2_MEDUSA]

Originally Posted by biigcj

Since I never found an answer to this when I looked- I’ll help you out. The vendors certainly have more experience than me but keep in mind, they also are in the business of selling parts.

I have been running the VTT crank hub bolt capture for about ~1500 miles now on stage 2 BM3 and e30 tune (depending on my moods) with ZERO issues. I don’t launch the car but frequently let it have it from a roll for fun. I’m in a 16’ f82 DCT with 10k miles, and rarely let the car kick down unless overtaking but love to push the car to the limits.

My buddy also runs the VTT capture on his f80 DCT and has for ~20-25k miles. This guy BEATS on his car, full e85 tune, digs, rolls, slicks, you name it, and has never had a single issue since he tuned it at 40k miles.

Two cases among many others on the forums with absolutely zero issues because of the capture. Can we say it for sure solves it? No. But it certainly seems to help.

It definitelly helps the bolt from backing out, For 1 hour job and $100 it removes one of the weakpoints but not all, This modification is totally worth it because of that, But if your bolt is already backed out preety good the cbc wont help. If you can slap one on prior to 30,000 miles you should be solid, Since its almost 2023 for most owners those miles have come and gone lol. I spun my crankhub at 12,000 miles on the dash. I had nothing. I went with the Vargus v2 splinelock and cbc together after that, Been about a year now knocking on 6's 60-130

[Marioec]

Bringing back this thread from the dead but has anyone spun the crank hub with the CBC only ?

[imperfectluck]

Originally Posted by Marioec

Bringing back this thread from the dead but has anyone spun the crank hub with the CBC only ?

On the phone at the moment but I did see a thread that was recent about the hub bolts shearing off I believe? Don’t quote me but I’ll try to search if someone doesn’t post it before I do. Can’t say I’m surprised as Track/S has voiced his thoughts on this a year ago and I agreed when reading through this thread.

Edit: This was the one I was referring to
here

[wheela]

Originally Posted by Marioec

Bringing back this thread from the dead but has anyone spun the crank hub with the CBC only ?

I know of an n54 guy that spun his hub with only VTT CBC.