"Project Demons Breath"

[Hpindy]

Well folks I have a CCI driveshaft on the car and all is good until about 120 mph then I start to get a vibration . These driveshafts are just too long and hit critical speed early . Too bad the mark Williams Is so damn expensive.

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[2fast4u]

Hopefully the DSS version of the 2 pc will be out soon...

 

[Marc W]

There’s this thing called a welder...... 🤔

 

[Hpindy]

There’s this thing called a welder...... View attachment 17834 View attachment 17835

Lol . Smart a$$
Once I find the sound I'm looking for I plan in have the whole exhaust tig welded and possibly ceramic coated .

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[Hpindy]

Hopefully the DSS version of the 2 pc will be out soon...

I sure hope so .........

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[Speedy!]

Am I an outlier not having any vibration from my DSS 4" aluminum? Been over 160mph.

 

[Marc W]

Am I an outlier not having any vibration from my DSS 4" aluminum? Been over 160mph.

I’ve had three (due to trans and diff changes) and none of them vibrated. Speeds up to 184 mph on the second one and the one now (2 u-joints) up to 155 mph. The vast majority of them are good.

 

[Hpindy]

I’ve had three (due to trans and diff changes) and none of them vibrated. Speeds up to 184 mph on the second one and the one now (2 u-joints) up to 155 mph. The vast majority of them are good.

Am I an outlier not having any vibration from my DSS 4" aluminum? Been over 160mph.

I bought this driveshaft at a screaming deal so Its one of those things . It's great for everyday driving . But after already breaking a driveshaft at the drag strip im a bit leary now . I have been looking at a permanent solution for the future .

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[DemonSRT]

I bought this driveshaft at a screaming deal so Its one of those things . It's great for everyday driving . But after already breaking a driveshaft at the drag strip im a bit leary now . I have been looking at a permanent solution for the future .

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Hey James,
Try this as sometimes it does make a difference.
Undo the driveshaft from either end and turn it 180 degree then reinstall it.
Then take it out and see if the vibration is less or gone.
If it does not improve or the vibration is not completely gone, then do the same on the other end of the shaft
Done it in the past myself and I believe even Bob did that before and it worked for him also.

Still, in the long run, the 2 piece driveshaft is the only way to go to get the critical speed up higher on our cars to be reliable without issues. I know other manufacturers are working on a quallity 2 piece as they have now realized that a 1 pc. just does not work correctly. I myself broke two 1 pc. shafts from DSS in the past in my modified 09 Challenger, (1 Carbon Fiber & 1 Aluminum), before going to a Chromoly shaft from Oliver which were only making them for Arrington Performance before it was sold and moved to Michigan, and it was perfect with no vibrations or breakage even when I gave it hell. Mark Williams and Bad Boyz are the only ones that offer a 2 pc. right now.

 

[Hpindy]

Hey James,
Try this as sometimes it does make a difference.
Undo the driveshaft from either end and turn it 180 degree then reinstall it.
Then take it out and see if the vibration is less or gone.
If it does not improve or the vibration is not completely gone, then do the same on the other end of the shaft
Done it in the past myself and I believe even Bob did that before and it worked for him also.

Still, in the long run, the 2 piece driveshaft is the only way to go to get the critical speed up higher on our cars to be reliable without issues. I know other manufacturers are working on a quallity 2 piece as they have now realized that a 1 pc. just does not work correctly. I myself broke two 1 pc. shafts from DSS in the past in my modified 09 Challenger, (1 Carbon Fiber & 1 Aluminum), before going to a Chromoly shaft from Oliver which were only making them for Arrington Performance before it was sold and was moved to Michigan, and it was perfect with no vibrations or breakage even when I gave it hell. Mark Williams and Bad Boyz are the only ones that offer a 2 pc. right now.

Thanks Ingo. I am going to do the 180 rotation this weekend and see if it makes a difference. I agree the 2 piece is the preferred long term solution.

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[Marc W]

One question I would have.... is the 2-piece going to be stronger because it’s distributing the load or is it just a solution to the vibration issues? I don’t have any vibration issues, so until it breaks I will go with.... it’s working for me. I have the strongest u-joints and Chromoly yokes money can buy, so if it let’s go, it’s probably going to be the shaft itself. If that happens then it’s going to have to be a Chromoly shaft or whatever 2-piece Is “guaranteed” to work regardless of the cost.

 

[DemonSRT]

One question I would have.... is the 2-piece going to be stronger because it’s distributing the load or is it just a solution to the vibration issues? I don’t have any vibration issues, so until it breaks I will go with.... it’s working for me. I have the strongest u-joints and Chromoly yokes money can buy, so if it let’s go, it’s probably going to be the shaft itself. If that happens then it’s going to have to be a Chromoly shaft or whatever 2-piece Is “guaranteed” to work regardless of the cost.

James might want to chime into this as he has researched this issue from talking to several driveshaft manufacturers on this.

Critical Speed:
Critical speed is a situation where the natural frequency is the same as the rotating speed of the driveshaft. When those two coincide vibrations are multiplied and will eventually shake the driveshaft so hard it will fail. When considering a driveshaft, it is extremely important to make sure that the car will operate at speeds lower than the critical speed.
The three factors that change critical speed are, length, diameter, and the ratio of weight to material stiffness. Just like a wind chime, the longer a tube is, the lower its natural frequency is, and the lower the critical speed. likewise diameter and how stiff a driveshaft tube is affects the critical speed. There are a lot of factors that go into critical speed but in general, a larger diameter and lighter tube will allow a driveshaft to spin faster.

One thing I will add to this is that you do not always feel the vibration that maybe happening with the driveshaft over time. You only know that one day the shaft breaks without knowing what caused it which can be from hitting the critical speed limit of the shaft or just from fatigue.

Here's other info from the MW site that you probably already know.
Important Driveshaft Criteria
There are several factors that go into driveshaft selection. In order of importance they are strength, critical speed, and weight. Selecting the proper driveshaft means taking a deeper look at the requirements of every application, because every application is unique. Careful consideration of these three factors will ensure reliable use with the highest performance.
Strength:
The first thing to take into account is the strength of the driveshaft a racer will need. The more power you have and the more a car weighs, the stronger the driveshaft needs to be. The weight of the car is one factor that is often forgotten when selecting a driveshaft. A 4000 lb. car with 1000 hp will be much harder on a driveshaft than a 1800 lb. car with the same power. There are three factors that make a driveshaft strong; material, diameter, and u-joint size.

In terms of material, steel and thicker walls will be the strongest choice, though there are obvious drawbacks with the added weight. Using high strength alloys allows thinner tubing walls to take out extra weight without sacrificing strength. Aluminum, especially when using high quality 7075 tubing and ends, offers a well balanced mix of strength and weight. Carbon fiber is by far the lightest driveshaft material with good strength. Mark Williams Enterprises offers a large array of material choices including: Mild steel, 4130 chrom-moly, 7075, 6061, a proprietary aluminum, and carbon fiber.
Increasing diameter will significantly increase the strength of a driveshaft, no matter the material. For example, increasing diameter from 3" to 4" will increase strength by about 80%. Increased diameter has some other benefits that we will discuss later.

The two most common u-joints used in drag racing are the 1350 and 1480 series u-joints, both offered by M-W. For the most part, 1350 series u-joints will work in almost every situation. They offer the best mix of strength, precision and weight. They are used in every class all the way to pro-stock. 1480 joints are reserved for extra heavy duty applications, mainly used in Pro-Mod and other high power classes especially when tire shake is an issue. U-joints are usually the weakest piece in the system.

 

[Marc W]

Very informative! 👍🏼

 

[Speedy!]

What's odd to me is you used to be able to get a 2 piece. Had a chromoly DSS 2 piece in the old car. Never had an issue but my buddy's failed at the cv joint after many years of use and he went back with a one piece and everyone said one piece was better lol.

 

[Hpindy]

One question I would have.... is the 2-piece going to be stronger because it’s distributing the load or is it just a solution to the vibration issues? I don’t have any vibration issues, so until it breaks I will go with.... it’s working for me. I have the strongest u-joints and Chromoly yokes money can buy, so if it let’s go, it’s probably going to be the shaft itself. If that happens then it’s going to have to be a Chromoly shaft or whatever 2-piece Is “guaranteed” to work regardless of the cost.

What's odd to me is you used to be able to get a 2 piece. Had a chromoly DSS 2 piece in the old car. Never had an issue but my buddy's failed at the cv joint after many years of use and he went back with a one piece and everyone said one piece was better lol.

If you have a drive shaft with zero issues that is great and I'd probably leave it alone too. But after hearing of a lot of people have vibrations from many different manufacturers driveshaft and breaking one myself I became leary ( I have seen a car pole vault at the track) I started researching more and found the 1 piece driveshafts are really long and hit critical speed on us . So a good solution is a 2 piece driveshaft so each shaft is shorter for high critical speed be now we run it to can we get a strong enough carrier bearing . I have called and talk to mark Williams Techs and they said their current hellcat 2 piece driveshaft is good to at least 1000 ftlbs of torque but haven't tested it any higher yet but will. Be looking into it because of how fast the cars are getting and power being produced . I will update everyone as I get more information from various driveshaft manufacturers.

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[moparjim]

The new Wiles driveshaft looks like a nice 1 piece. So far the ones that have installed it have no complaints. The slip joint is now in the rear using a Sonax slip joint from the looks of it.
I will be installing a safety loop shortly.
I don't really care much for hanger bearings and 2 piece ds's. Funny how we change over time. Didn't we used to change from 2pc ds to a 1pc ds for drag racing before?

 

[DemonSRT]

What's odd to me is you used to be able to get a 2 piece. Had a chromoly DSS 2 piece in the old car. Never had an issue but my buddy's failed at the cv joint after many years of use and he went back with a one piece and everyone said one piece was better lol.

CV Joint was one of the weak links on the aftermarket shafts which they do not use on the 2 pc shafts manufactured today.

 

[DemonSRT]

The new Wiles driveshaft looks like a nice 1 piece. So far the ones that have installed it have no complaints. The slip joint is now in the rear using a Sonax slip joint from the looks of it.
I will be installing a safety loop shortly.
I don't really care much for hanger bearings and 2 piece ds's. Funny how we change over time. Didn't we used to change from 2pc ds to a 1pc ds for drag racing before?

The aftermarket 2 pc hanger bearings are a stronger and held in with polyurethane now instead of soft rubber like the factory ones are. My Oliver shaft was polyurethane. That was a major improvement as well.

 

[Speedy!]

I ran a Petty's DS loop on the old car and it was a trick setup that replaced the trans cross member. I really liked it but nothing like that for the Hellcat that I know of. I'd like to put a loop on mine, what are you guys using? The good news is the exhaust will catch the DS if it breaks, but a loop is always a good idea.

 

[Hpindy]

I ran a Petty's DS loop on the old car and it was a trick setup that replaced the trans cross member. I really liked it but nothing like that for the Hellcat that I know of. I'd like to put a loop on mine, what are you guys using? The good news is the exhaust will catch the DS if it breaks, but a loop is always a good idea.

I like the BMR driveshaft loop .

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