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Author Topic: Stronger Bottom shaft for Winters Extremeliner.  (Read 22464 times)
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Stainless1
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Robert W. P. "Stainless" Steele Wichita, Kansas



« Reply #15 on: March 19, 2016, 11:59:37 PM »

Rob it would seem to me that it would be hard to apply that much torque to the driveline without excessive wheel slip in your lower gears. If you are looking at salt or dirt, both have a low traction coefficient.  Pavement venues might be a little short for you.
 cheers
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MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
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« Reply #16 on: March 20, 2016, 01:46:33 AM »

Rob,

Since you are modeling this up, have you tried gundrilling the center out?

John
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« Reply #17 on: March 20, 2016, 08:29:59 AM »

I'll throw in my 2 cents just because I have too much experience with drive train failure.

Two common causes for failures like this is fatigue and drive train shock loads. I'll say it is unlikely fatigue in this instance based on my experience. The steady state loads (simple engine torque calculation) are seldom as high as the peak loads due to wheel slip then grab, intermittent engine misfire etc. The peak loads from these is not due to the tire to wheel friction but due to the drive trains attempt to speed up or slow down its rotating mass in a portion of a second. This torque spike breaks stuff and designing in some rotational flex is a way to stop the short duration spike from breaking things. Sizing up the broken part is a good possibility but the risk has been discussed. There is no doubt that your driver is TOP NOTCH but I would suggest to try not to run the engine at full load in lower gears. Then when the peaks happen they may not break things. Also do anything reasonable to eliminate peaks like misfires or power shifting since it first has to accelerate the drive train then the car. This going gentler on the drive train may not be a possibility when going for records.

It's great that you are able to look at this with FEA and I think your approach is spot on. Yes it might move the failure to something else but predicting this is very difficult.
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« Reply #18 on: March 20, 2016, 08:45:44 AM »

Rob,

You may want to give G-Force transmissions a call. They offered to make a custom lower quickchange shaft for my oddball application. I think they make standard winters shafts already. Very nice guys to work with, they also do REM polishing in house and make their own quick change gears.

May be worth a call.

Andy
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« Reply #19 on: March 20, 2016, 11:13:48 AM »


Rob it would seem to me that it would be hard to apply that much torque to the driveline without excessive wheel slip in your lower gears. If you are looking at salt or dirt, both have a low traction coefficient.  Pavement venues might be a little short for you.
 cheers

By the time we get to 5000 rpms and the meat of the torque curve, we are making approx 2500 lbs of down force. Our car is very different from former efforts. I don't think anybody can load (steady state torque) a rearend as hard as we can in the lower gears. Even the high hp four wheel drive cars are dividing their torque between two differentials.
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« Reply #20 on: March 20, 2016, 11:21:28 AM »


I'll throw in my 2 cents just because I have too much experience with drive train failure.

Two common causes for failures like this is fatigue and drive train shock loads. I'll say it is unlikely fatigue in this instance based on my experience. The steady state loads (simple engine torque calculation) are seldom as high as the peak loads due to wheel slip then grab, intermittent engine misfire etc. The peak loads from these is not due to the tire to wheel friction but due to the drive trains attempt to speed up or slow down its rotating mass in a portion of a second. This torque spike breaks stuff and designing in some rotational flex is a way to stop the short duration spike from breaking things. Sizing up the broken part is a good possibility but the risk has been discussed. There is no doubt that your driver is TOP NOTCH but I would suggest to try not to run the engine at full load in lower gears. Then when the peaks happen they may not break things. Also do anything reasonable to eliminate peaks like misfires or power shifting since it first has to accelerate the drive train then the car. This going gentler on the drive train may not be a possibility when going for records.

It's great that you are able to look at this with FEA and I think your approach is spot on. Yes it might move the failure to something else but predicting this is very difficult.

We do "lift to shift" to avoid transient torque spikes and our high down force that we achieve even in lower gears keeps the drive tires on the ground much better than most. Long rear axles also help to absorb transient torque spikes that occur when and if tires leave the ground.
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« Reply #21 on: March 20, 2016, 04:00:43 PM »

Rob,

Per your previous post, Winters said: "Vaughn Winters is convinced that the material change alone has solved the problem. He said that nobody has broken one yet. My math says the problem is not solved. " From this I would assume that Winters changed from some previous material ( my guess would be 4340 aircraft quality steel) to 300M. 300M is nothing more than a very high quality 4340 (it does have some additional vanadium and silicon) that has been double and sometimes triple vacuum remelted in an inert atmosphere. The strength properties are effectively the same  as 4340, the advantage that 300 M brings is its purity provides extended  fatigue life. which allows it to be used in smaller sections, i.e. lighter, at higher hardness levels and still provide sufficient strength and fatigue life. I my way of thinking Winters has not done a sufficient job of properly applying this material. Normal use of 300M is at tensile strength levels of around 280,000 psi which is provided by hardness of around Rc 50-52. At Rc 30 the tensile strength is approx. 140,000 psi so it is possible to literally double the strength of the shaft at the same dimensions by merely doing a correct heat treat and draw. Obviously the advantage of going to a higher heat treat it that you do not have to increase the shaft diameter to get sufficient strength and you will still have the same amount of shock attenuation (shaft wind up) as the standard shaft.

Heat treat should be done in a vacuum or inert atmosphere oven and the shaft must be hung vertically. You must use a very reparable heat treat facility with experience with 300M.

I would highly suggest you contact some one like Latrobe Steel, Latrobe,PA and discuss your application and also what they would suggest for the proper heat treat and which one of their several 300M steels they would recommend for your application.

The other option if you are not going to heat treat and just go to the increased diameter would be to use aircraft quality (vacuum melted) 4340, normalized,  which will have the same tensile and yield strengths as 300M but be considerably less expensive.

Rex
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« Reply #22 on: March 20, 2016, 05:09:36 PM »

John, it's obvious you know what you're talking about. I have adjusted the 1.22 diameter so that it "goes red" on FEA the same time that the snap ring grooves and the minor dia of splines do.  The shaft will still torsion twist at the 1.22 dia  a few degrees at max torque. I may actually adjust it to 1.20 dia to make sure it is the weak link.
Even then, 1.20" is substantially stronger than 1.062".
Vaughn Winters is convinced that the material change alone has solved the problem. He said that nobody has broken one yet. My math says the problem is not solved. We can put down way more torque than anybody else in low gear. Even with these changes, I will have to limit low gear boost to 11 psi to keep crankshaft torque under 1300ft/lbs of torque as it will be multiplied by 2.48.
Winters will not be paying the $5000 plus bill to get our car and team back in forth to the salt never mind the heartbreak and labor of fixing it or worse yet a spoiled back up run.
I offered to pay for a run of these shafts to be made with an increased torsion section and an increased  relieved section behind the QC splines (increased to minor diameter). They couldn't be bothered. We are in the meat of race preparation season now so they are crazy busy. I was a little upset that they would not share the spline information so I could have someone else make them. It's not a big deal as I can reverse engineer them but why make it hard for me. It's not like I'm not buying their stuff.

Rob,

Per your previous post, Winters said: "Vaughn Winters is convinced that the material change alone has solved the problem. He said that nobody has broken one yet. My math says the problem is not solved. " From this I would assume that Winters changed from some previous material ( my guess would be 4340 aircraft quality steel) to 300M. 300M is nothing more than a very high quality 4340 (it does have some additional vanadium and silicon) that has been double and sometimes triple vacuum remelted in an inert atmosphere. The strength properties are effectively the same  as 4340, the advantage that 300 M brings is its purity provides extended  fatigue life. which allows it to be used in smaller sections, i.e. lighter, at higher hardness levels and still provide sufficient strength and fatigue life. I my way of thinking Winters has not done a sufficient job of properly applying this material. Normal use of 300M is at tensile strength levels of around 280,000 psi which is provided by hardness of around Rc 50-52. At Rc 30 the tensile strength is approx. 140,000 psi so it is possible to literally double the strength of the shaft at the same dimensions by merely doing a correct heat treat and draw. Obviously the advantage of going to a higher heat treat it that you do not have to increase the shaft diameter to get sufficient strength and you will still have the same amount of shock attenuation (shaft wind up) as the standard shaft.

Heat treat should be done in a vacuum or inert atmosphere oven and the shaft must be hung vertically. You must use a very reparable heat treat facility with experience with 300M.

I would highly suggest you contact some one like Latrobe Steel, Latrobe,PA and discuss your application and also what they would suggest for the proper heat treat and which one of their several 300M steels they would recommend for your application.

The other option if you are not going to heat treat and just go to the increased diameter would be to use aircraft quality (vacuum melted) 4340, normalized,  which will have the same tensile and yield strengths as 300M but be considerably less expensive.

Rex

Rob,

After meeting you @ the PRI show and inspecting the broken shaft, my opinion about the failure remains the same.    I still think that the shaft was overloaded and failed due to "machining" of the OD in the small center section.   Without any inspection instruments, it appeared to my naked eye that the failure precipitated on the coarsely machined outer surface, a surface so coarsely machined, that it appeared to be "finely threaded".    I suggested at the time that you consider a surface treatment such as surface "micro-polishing", in an effort to remove surface defects on any replacement part.    My opinion remains the same.    In the photo you posted, there is an obvious defect at the surface.    I suspect that is where the failure originated.

After reading through this thread, I have some further thoughts.     Some of this is, to me at least, stating the obvious.

1/   Trust your own judgment and engineering.    I think you are in the best position to evaluate a solution using the recommendations of specialists.

2/   You might want to have the remains of the old shaft analyzed by a good metallurgist, even if Winters has given you a specification.
      That would:
      A/ Define the failure.
      B/ Determine the material.
      C/ Determine the material condition/heat treat.   In my opinion these are important issues that need resolution, and the cost would be small.
 
3/   A material or size change alone will not solve the issue.   It needs to be a comprehensive solution that includes heat treatment and surface finishing, as Rex has
      suggested.

4/   Increased shaft strength will probably reveal the next weak link, as many have pointed out.    It may be impossible to predict where that next failure will occur, unless
      some part is "designed" to fail.    I'm uncertain of whether designing a "failure link" is a good idea for your vehicle.   It would be paramount to retain control of the vehicle
      in the event of a drive train failure, again stating the obvious.

5/   Since the failure of this part requires so much "down time" for repairs, you are no doubt analyzing a solution that would prevent a repeat.

6/   It is always disappointing when a supplier becomes "uncooperative".    But it is the nature of this business.

I hope you can at least get some "moral support" from the rest of us following along.

 cheers
Mark
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« Reply #23 on: March 20, 2016, 05:20:38 PM »

Re: "We do "lift to shift" to avoid transient torque spikes"

Has anyone experimented with doing this automatically, like a micro-switch on the clutch linkage that retards the spark?
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« Reply #24 on: March 20, 2016, 10:03:53 PM »

Re: "We do "lift to shift" to avoid transient torque spikes"

Has anyone experimented with doing this automatically, like a micro-switch on the clutch linkage that retards the spark?

Yes.
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Michael LeFevers
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« Reply #25 on: March 21, 2016, 08:11:22 AM »

I'm wrestling with the universal problem of "giant torque spike after the shift with turbo". Just killing power comes in too late, and (from what I hear, no personal experience) the BOV capacity has to be near the engine displacement to completely save traction. This is pavement use at high boost with 4L80E, the transmission will take the shock but the tires won't.
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« Reply #26 on: March 21, 2016, 09:39:09 AM »

Re: "We do "lift to shift" to avoid transient torque spikes"

Has anyone experimented with doing this automatically, like a micro-switch on the clutch linkage that retards the spark?



So I'm supposed to LIFT at the SHIFT......... I didn't know...   grin






* rear_with_swingarm lr.JPG (88.33 KB, 778x581 - viewed 205 times.)
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« Reply #27 on: March 21, 2016, 06:58:59 PM »

I know this is off track but I thought I might talk about what actually causes the torque spike when you let the motor rev between shifts.

If we shift gears and let the motor rev, when we snap the clutch out the motor has alot of kinetic energy that it gives to the transmission, driveshaft and third member because they are tuning slower. If we shift from first to second at 8000 RPM and let the motor rev it's maybe goes to 9,000 RPM, but the input shaft to the transmission is maybe turning 7,000 RPM*. If we snap the clutch out, the different RPMs have to match within a portion of a second. This causes a large torque spike in the  drivetrain. One of the things that determines how much the spike is, is how much the clutch slips before the parts are at matched speed. The faster they match the higher the spike. And this analysis does not even consider the engine torque being transmitted.

Of coarse we all know this is how we could make our six cylinder Ford Comet three speed chirp the tires.

* Why is this only 7000 and not the 8000 you just shifted at. Because when you shifted, the synchronizer slowed the input shaft down.

   ________________________________________________________________________________________________________________________________________


Rob thanks for being a good sport while we all "solved your problems" from our easy chairs rolleyes.

I do want to mention what I'm sure you already know and that is the affect of a shaft that varies in diameter such as due to coarse machining like Fordboy said. If this shaft acts like a torsional spring by wrapping and unwrapping based on changes in transmitted torque, there will be adjacent areas of the shaft that flex and next to it, it is more rigid. This will cause serious stress risers. If you still have access to FEA you might see what this does to a shaft that is under high enough torque for the alloy to go into elastic (not plastic) deformation.
« Last Edit: March 21, 2016, 08:27:09 PM by DaveB » Logged

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« Reply #28 on: March 21, 2016, 10:58:11 PM »


Re: "We do "lift to shift" to avoid transient torque spikes"

Has anyone experimented with doing this automatically, like a micro-switch on the clutch linkage that retards the spark?



So I'm supposed to LIFT at the SHIFT......... I didn't know...   grin

No, you don't have to. You have a substantial rearend.
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« Reply #29 on: March 22, 2016, 08:51:00 AM »


Re: "We do "lift to shift" to avoid transient torque spikes"

Has anyone experimented with doing this automatically, like a micro-switch on the clutch linkage that retards the spark?



So I'm supposed to LIFT at the SHIFT......... I didn't know...   grin

No, you don't have to. You have a substantial rearend.  

Some might say He Is A Substantial Rearend!    grin
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Michael LeFevers
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