Drive Shaft Twisting

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
tommylommykins
tommylommykins
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Re: Drive Shaft Twisting

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hmm, I would imagine that for reasonable traction control from the start on any high performance car, you'd need driveshafts that could store enooooooooormous amounts of energy.

With the amount of excess power it'd need to be storing to make it a worthy start-control system, it'd make kers a walk in the park... You wouldn't need the scary, heavy, battery systems that you have nowadays... You could just install an Eddie Jordan Driveshaft, wind it up at the start and unwind it as necessary as you were going along.

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Shaddock
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Re: Drive Shaft Twisting

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bettonracing wrote:Ciro,

Your calculations neglect gear and final drive ratios. Even with a 20:1 total ratio (roughly estimated from the 660mm diamater for 1st gear), we're talking 23 degrees max.

Regards,

H. Kurt Betton

Edit: This assumes the car could get maximum traction and has maximum power output in 1st gear(...). In the higher gears where it does have maximum engine output and full traction, the gear ratios are lower and therefore the multiplication factor is reduced by whatever the relevant gear ratios are.
Still not right, as the calculation assumes that the wheel is 'fixed' and cannot turn (spin). You need to add in the CoF of the tyre to calculate how big a spike of torque the drive shafts actually experience.

bettonracing
bettonracing
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Re: Drive Shaft Twisting

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Shaddock wrote: Still not right, as the calculation assumes that the wheel is 'fixed' and cannot turn (spin). You need to add in the CoF of the tyre to calculate how big a spike of torque the drive shafts actually experience.
Worst case scenario (for the axle): Instantaneous torque spikes. Assumes no slip.

Regards,

Kurt

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xpensive
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Re: Drive Shaft Twisting

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Urban legends can take you a long way, but why would you want a twisting shaft anyway?
"I spent most of my money on wine and women...I wasted the rest"

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Ciro Pabón
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Re: Drive Shaft Twisting

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Well, your mistresses could appreciate it. Talk with them, who knows?

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Dear smaldj,
sorry if it seems that our intention is to blame you somehow for something.

On the contrary, thanks a lot, very interesting, please keep them coming. Allow me to explain a little, will ya?

We do not want to shred things, we want to learn from you. Up to this minute, I've learned a bit, thanks again.

Please, give us more crazy ideas, we love them, specially urban legends, which usually are the most "tasty" (that's why they're famous: they're are credible but improbable).

Besides, in this forum (while I'm alive!), we always think we can be mistaken: I can have the wrong numbers, the wrong equations, or the wrong assumptions and for me is very comforting to know that there is people in this world that shares enough my interests to check them.

You know something? Better yet, from those crazy ideas, specially when criticized with numbers, come the GREAT ideas in engineering.

In five seconds domdogger took your proposition, our contributions to it and found an idea for a launch control system: if you could use the axle as a clutch...

In a few minutes ringo showed that when you make the axle thinner, you reach one degree of twisting, which is A LOT. I think that under one degree, the thing could break, but that requires a couple of calculations more.

Anyway, only when I saw his calculations did I realize that this darn thing of twisting is proportional to the FOURTH power of the diameter of the axle and that maybe strad and his paint lines can have a grain of truth in them.

Mikey_s stated (somehow) that this "launching clutch" should have less resistance than the one the wheels have, which shows you two things: wheels are "natural clutches" under heavy power, which makes you thing about taller wheels with taller sidewalls if you want to exploit this "Mikey_s effect" in drags. Secondly, you could devise a clutch for launching if you, for example, made a section of the axle of rubber, for example, so that it twists by design.

Finally, you want urban legends?

I can give you urban legends. Compared with them, The Legend of The Twisting axle is only a beginning.

Let me explain: all drivers, me included, believe in Voodoo. For example:

- they think green cars bring bad luck
- they do not eat peanuts the day of the race
- they do not eat fried chicken
- they put the left glove first
- they use red gloves
- they think that Corvette bodies end crashing
-

... don't ask me why, I swear to high heaven I've heard that.

Corvette body? No thanks!
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Green Corvette: what could be worse? One with a twisting axle, perhaps?
Ciro

smaldj
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Joined: 22 Feb 2011, 10:38

Re: Drive Shaft Twisting

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Thanks Ciro, I hadn't thought of it that way - dismissing crazy ideas could provide some inspiration for some realistic ones...

It sounded, to a non-mech engineer like myself, to be a bit plausible. By saying this, I mean that the axle could twist (ever-so-slightly) to reduce wheel-spinning so that when the wheels gripped, this stored energy could be released and would thus provide a little bit of extra power to get off the line with.
Also, (another crazy idea coming) I thought that the driveshaft could be slightly concave so that the centre would have a bit less resistance (thus allowing the twisting) than either end... you'd have to do a fair bit of testing to ensure that the resistance was just right - too much and there'd be no twisting and too little and you'd snap the shaft.

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strad
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Re: Drive Shaft Twisting

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and that maybe strad and his paint lines can have a grain of truth in them.
GEE, thanks..Since I've seen it.
Try it yourself..pull an axle,,paint a line down the length..use it for a year.pull it out....SEE...slowly but surely it twists...under normal use I imagine it reaches some point where it slows or stops but it twists....I don't think you'd want to twist a driveshaft...most are hollow and bad things happen.
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss

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Tim.Wright
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Joined: 13 Feb 2009, 06:29

Re: Drive Shaft Twisting

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There's no way this could work because the release of energy is completely uncontrolled.

Imagine axle tramp under braking but during acceleration and on a much larger scale. Thats what you would acheive by making springy axles.

On a somewhat related note; The axles on the Aussie V8s can twist upto 45deg permanently after a race, though that is because they have no diff.

Tim
Not the engineer at Force India

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strad
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Re: Drive Shaft Twisting

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TaDa =D> ,,bet they're a bitch to pull as the splines get all preloaded with the twist. ;)
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss

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Ciro Pabón
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Re: Drive Shaft Twisting

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strad wrote:
and that maybe strad and his paint lines can have a grain of truth in them.
GEE, thanks..Since I've seen it.
Well, I'm not saying you were lying. However, you race, don't you? So, I was just wondering how strong that day's hangover was.
Tim.Wright wrote:On a somewhat related note; The axles on the Aussie V8s can twist upto 45deg permanently after a race, though that is because they have no diff.

Tim
mmmm... so, you say the material creeps? That's a tad more plausible.

I would love to make the calculations but first, we should estimate the temperature of the thing.

Anyway, googling a bit, if the yield strength is around 24 ksi (sorry, working with american tables) AND the axle reaches, I don't know, 700 degrees centigrades (less than 400 and the strength is practically the same) strength goes down to 18.5 ksi. So...

Darn, again, the same thing. I'd say that it shouldn't be noticeable. I'm estimating from a table for turbine shafts: do not believe me until someone in this thread pulls out the EngFit module for creep.

However, I still cannot believe the Aussie thing. I get a total strain of 0,0025 mm before the axle breaks. I'll spare you the boring tables, because there are no equations involved in this, everything is empirical.

What are those axles made of? Plasticine? You cannot strain steel more than 1 per cent or so before it fails. Unless it goes over 600 or 700 degrees, I cannot see plastic accommodation happening (or so the table says).

So, in English, how hot are those shafts? (xpensive, no jokes).
Ciro

tommylommykins
tommylommykins
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Joined: 12 May 2009, 22:14

Re: Drive Shaft Twisting

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What is the unit of measurement that governs how creep forms?

Is it (unit of force) / (time) ? Is it (enegry) / (time)

If so, what is the overall force/energy that goes through a driveshaft during a race, compared to the force/energy that has gone through the suspension coils of a ford mondeo over the period of 10 years, causing it to squat?

I assume that the springs on such an old car have experienced much more (instances of the unit of measurement for the thing that causes squat/creep) than would go through a driveshaft in one race

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strad
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Re: Drive Shaft Twisting

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Actually I'm suprised more of you have run into axle twist. At times it can make it a bear to remove the axles because of it. Twisting the splines is pretty common in offroad and drag racing,,and I bet if I pull the axles on my Cobra there will be some twist.
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Image
To achieve anything, you must be prepared to dabble on the boundary of disaster.”
Sir Stirling Moss

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Ciro Pabón
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Re: Drive Shaft Twisting

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So, it gets pretty hot. I wish I had the books here, I don't. I'll revisit the thread as soon as I can say something about the temperatures that could explain this amount of twisting.

I would love for a mechanical engineering to say something. All I know is structures.
Ciro

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flynfrog
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Joined: 23 Mar 2006, 22:31

Re: Drive Shaft Twisting

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Ive seen the before too in stock cars. The rear isn't that hot maybe a couple hundred degrees F.

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flynfrog
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Re: Drive Shaft Twisting

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Ciro Pabón wrote:So, it gets pretty hot. I wish I had the books here, I don't. I'll revisit the thread as soon as I can say something about the temperatures that could explain this amount of twisting.

I would love for a mechanical engineering to say something. All I know is targets.

fixed it for you