One piece driveshaft

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One piece driveshaft

Post by Esasky's62Lark on Wed Jul 20, 2016 6:42 am

Gents,

If you don't recall, I am currently building a 62 with a 300 out of a 64 LeSabre and a TH350. I recently had a driveshaft made for the car. the driveshaft is one piece; measuring 3" in diameter and 60.5" C to C.

After getting it made, I started to wonder if there would be an issue with the driveshaft critical speed since the DS was so long. Using Dana's RPM calculator, they are saying that my maximum safe operating speed for DS is right @ about 3,600 RPMs.

This concerns me because I know that with a TH350, final gear ratio is 1:1. this means that top safe speed of the car, with my tire size and stock gears in the rear, would be around 80 mph; not to mention that 3,600 RPMs is a low critical speed.

Has anyone on here converted to a one-piece driveshaft that utilizes 1350 yokes and u-joints and hasn't had any issues with vibration at highway speeds or frequency amplification?

Thanks in advance guys!

Chris
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Re: One piece driveshaft

Post by 62cutlassconvert on Wed Jul 20, 2016 10:12 am

Hmmm, something is fishy with this calc or the understanding of it. Doesn't make sense. Where's the experts?

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Re: One piece driveshaft

Post by Tim_D on Wed Jul 20, 2016 1:54 pm

Esasky's62Lark wrote:Gents,

If you don't recall, I am currently building a 62 with a 300 out of a 64 LeSabre and a TH350.  I recently had a driveshaft made for the car.  the driveshaft is one piece; measuring 3" in diameter and 60.5" C to C.  

After getting it made, I started to wonder if there would be an issue with the driveshaft critical speed since the DS was so long.  Using Dana's RPM calculator, they are saying that my maximum safe operating speed for DS is right @ about 3,600 RPMs.  

This concerns me because I know that with a TH350, final gear ratio is 1:1. this means that top safe speed of the car, with my tire size and stock gears in the rear, would be around 80 mph; not to mention that 3,600 RPMs is a low critical speed.

Has anyone on here converted to a one-piece driveshaft that utilizes 1350 yokes and u-joints and hasn't had any issues with vibration at highway speeds or frequency amplification?

Thanks in advance guys!

Chris

I get different numbers using my calculation tool.

First off, I made some assumptions:

1) Tube wall thickness is about 2.5mm (3/32")
2) Tube material is steel (not aluminum or CF)

Based on these assumptions, and using your data above, I get a critical speed of 5265rpm. Using a factor of safety of 0.9, the speed then becomes 4739rpm.

I then made another assumption - tire diameter of 24". If I plug those critical speeds into another tab of the calculator, I get a max vehicle speed of 99.3mph at the safety factor above, or 110mph with no safety factor calculation.

If the tire diameter goes up, the max speed goes up with it.

By the way, I'm a propshaft engineer by trade. I used this calculation tool to design the 1-pc prop in my '62.

PS - where's my $25 for the exhaust manifolds I sent you last year?  Laughing
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Re: One piece driveshaft

Post by Tim_D on Wed Jul 20, 2016 2:03 pm

Full disclosure however - Since completing my car, I've not had it over about 85mph. I didn't have any evidence of propshaft resonance, however, at that speed.
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Re: One piece driveshaft

Post by Esasky's62Lark on Wed Jul 20, 2016 2:17 pm

Tim_D wrote:
Esasky's62Lark wrote:Gents,

If you don't recall, I am currently building a 62 with a 300 out of a 64 LeSabre and a TH350.  I recently had a driveshaft made for the car.  the driveshaft is one piece; measuring 3" in diameter and 60.5" C to C.  

After getting it made, I started to wonder if there would be an issue with the driveshaft critical speed since the DS was so long.  Using Dana's RPM calculator, they are saying that my maximum safe operating speed for DS is right @ about 3,600 RPMs.  

This concerns me because I know that with a TH350, final gear ratio is 1:1. this means that top safe speed of the car, with my tire size and stock gears in the rear, would be around 80 mph; not to mention that 3,600 RPMs is a low critical speed.

Has anyone on here converted to a one-piece driveshaft that utilizes 1350 yokes and u-joints and hasn't had any issues with vibration at highway speeds or frequency amplification?

Thanks in advance guys!

Chris

I get different numbers using my calculation tool.

First off, I made some assumptions:

1) Tube wall thickness is about 2.5mm (3/32")
2) Tube material is steel (not aluminum or CF)

Based on these assumptions, and using your data above, I get a critical speed of 5265rpm. Using a factor of safety of 0.9, the speed then becomes 4739rpm.

I then made another assumption - tire diameter of 24". If I plug those critical speeds into another tab of the calculator, I get a max vehicle speed of 99.3mph at the safety factor above, or 110mph with no safety factor calculation.

If the tire diameter goes up, the max speed goes up with it.

By the way, I'm a propshaft engineer by trade. I used this calculation tool to design the 1-pc prop in my '62.

PS - where's my $25 for the exhaust manifolds I sent you last year?  Laughing

Tim,

Which calculation tool are you using? I was using the one off of Dana's website.

1.) I am guessing the tube wall thickness is 3/32" of an inch as well.

2.) The tube is steel.

The tire diameter is in fact right around 24".

You are the exact person I was looking for to get answers from!

My question is: Did you factor in that you are using CV style joints while I am using standard U joints?

Holy ****! I totally forgot about that! I am so sorry Tim!

Please shoot me a PM with you Paypal info and I will send it right now! I feel like a dumb ass! :-(



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Re: One piece driveshaft

Post by Tim_D on Wed Jul 20, 2016 2:49 pm

Tim_D wrote:
Esasky's62Lark wrote:

PS - where's my $25 for the exhaust manifolds I sent you last year?  Laughing

Hey I never miss an opportunity to take a jab at a fellow rodder!

As far as the calculation tool, it's a proprietary tool in the company I work for, developed by our FEA engineer. The tool does not differentiate between a cardan joint and a CV joint, as they are similar in mass for similar-sized joints.

I have a call into him to see if there are any bugs, but I have used it successfully for years.
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Re: One piece driveshaft

Post by Esasky's62Lark on Wed Jul 20, 2016 2:53 pm

I am serious Tim! I owe you for those!

Great to hear sir! That makes me feel better as the DS was already made.

I appreciate it very much sir!

Chris
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