| Author | Message | ||
| Matthew F (Mateotnt)
New member Username: Mateotnt Post Number: 47 Registered: 7-2002 |
Does all of this explain why my Schwinn has reverse threaded pedals? I thought it was so I wouldn't unscrew them as I pedaled. | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 87 Registered: 7-2003 |
That's it James, you've got it. And if you race on a clockwise track when the moons in it's 3rd quarter all your wheels will fall off...unless you're in the southern hemisphere when all your wheels will self tighten. I can add, that on the 360 Challenge fleet, if any nut comes loose it's always the LH drive shaft/hub nut....but only if it's not done up correctly in the first place. It has a conventional RH thread and is subjected to similar forces that the centrelock nuts are....but they have RH threads on the LH...so Ferrari's own theory is questioned now..... and on it goes | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2398 Registered: 10-2002 |
Bill Do you by chance have an AUS. Lotus? Perhaps because whirlpools go in different directions on different sides of the equator your manual says rt on rt side. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 501 Registered: 5-2001 |
Phil and JRV, I guessed Phil was pulling my leg on this but also knew the WM was common to all Elans with KO's on this issue. FYIW, I'm researching the axial deformation question under pure torque. So far all the structural types I've questioned are unaware of a change in length due to pure torque, but I'm not done yet. It was suggested however that a good way to model this problem would be to use several beam elements, end to end, fix the end face of the first element and apply a torque or rotational displacement to the end of the last element. The alternative is to do a fine layered mesh of brick elements and apply the same boundary constraints. One would then search for an axial displacement. What do you think Dr. Mike? | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2241 Registered: 11-2002 |
>>Nice try Phil, but the Elan shop manual doesn't differentiate between LHD and RHD cars, although my Elan is RHD.<< It was a joke Bill !!!! {  } But a SKODA now thats different!!!...every 3rd lug nut has opposite theads to insure no loosening when backing up. | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 85 Registered: 7-2003 |
I can't believe you went and checked your manual after what I wrote!!! Gee you Americans are funny guys!! | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 496 Registered: 5-2001 |
Nice try Phil, but the Elan shop manual doesn't differentiate between LHD and RHD cars, although my Elan is RHD. | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 80 Registered: 7-2003 |
Guy's, I've cracked it. Colin Chapmans cars are all Right hand drive for the UK, whereas Enzo's are Left Hand Drive for Europe/US. It must be to do with where the driver sits or something...... | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 722 Registered: 6-2002 |
James G. - quoting Bill S. "James S, Yes, it's possible, that's why I checked my shop manual. It says "RIGHT-HAND threads on right side of the car. LEFT-HAND threads on left side of the car". No kidding, the capital letters are in the manual. Perhaps Enzo had a different view of the consequenses of the physics then did Colin Chapman." Jim S. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2372 Registered: 10-2002 |
Jim That I don't understand. (Lotus) Best | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 721 Registered: 6-2002 |
James G. - sounds like the pins you describe are truly torque bearing. The ones on my Dino are not that substantial, but as I recalled after your observation, the Dino has 5 lug bolts. I find Bill S.'s observation that his Lotus is right-hand thread on the right side of the car very interesting. Jim S. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2370 Registered: 10-2002 |
Jim The pins on my Lola have dealt with 500HP in a 1700lbs car for 37 years so far. The one's in my Duesy are still working after 72 years. (That puppy weighs 7000lbs but only has 260hp.) They mate into the wheel and the nut holds them tight. Tighten to the rear. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 720 Registered: 6-2002 |
James G. - right you are - my Dino has pins, but has 5 lug nuts. HOWEVER, I suspect that friction between wheel and brake drum or hub once the KO is torqued exceeds the shear capabilities of the pin. I'd have to see the pin. Jim S. | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 457 Registered: 10-2002 |
JRV...that's a good one!!!!! | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2364 Registered: 10-2002 |
James S. You be wrong. Pin drive smooth axles. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2233 Registered: 11-2002 |
Very interseting to say the least! >>Remembering the 2nd rule of engineering : "Everything works on paper." << Then remembering the last rule of engeneering. "engeneers build their mistakes, mechanics repair them" { } | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 77 Registered: 7-2003 |
Jeff The torque reaction theory doesn't work, because the front wheels receive higher brake loads than acceleration, and the rear wheels receive higher acceleration loads than brake.......so for your theory to be correct, you'd need different threads on each axle, rather than each side..... Drive you nut's trying to figure it out. It's like understanding girls....just when you think you've got it, they get pregnant and it all changes again! | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 719 Registered: 6-2002 |
Dr. Mike - the 3rd Law of Engineering - "Every system is perfectly designed for the results that it achieves." Jim S. | ||
| David Feinberg (Fastradio2)
Member Username: Fastradio2 Post Number: 288 Registered: 4-2002 |
In the FWIW dept, One of my old Alfas had RHT lug bolts on one side..and LHT lugs on the other... David | ||
| Dr. Mike Adams (Drmike)
New member Username: Drmike Post Number: 33 Registered: 5-2002 |
Funny thng is, that I had originally argued against this hypothysis ( almost 20 years ago ). I had said that the rotating contact patch wave, due to minor imbalances and normal/cantilever bending force caused the knockoff to walk. ( kinda like when you spin a coin, just before it stops ). This durring normal forward rotation. But I got shot down becuase, in real life, the effect only seems in play if the brakes are applied repeatedly. It is counterintuitive to me also, that a simple cylidrical section will elongate under torsional loading. Not only THAT, but there may be more applied force in the form of cantilever bending/shearing than from torsional loading! I do remember that more time was spent in school on torsional moments vs. all other forms of stress/strain combined. I have not pulled out Mark's handbook yet. But I don't think they go into enough detail to deal with conical sections and interfaces on stepped shafts, radiused fillets, etc. I THINK I have a Schaum's outline that may go into those details. I have a VAGUE recollection that the axial effects of torsional stress are not constant along the radius of a cylindrical section... maybe this comes into play. I can't make it happen in my brain. Maybe I will have to create a FEA model of the splineshaft. I am pretty damn sure a tubular section would not do it. The probem with FEA is that it is not predictive when you don't have enough elements Except for the damn empirical data, I would have thought it would be the reverse! But just try swapping your splineshafts side to side... and you will see your front wheels preceding you down the freeway. It would be ironic if no one has every really formally described this whole phenomena and that the origins of the reverse threads on the passenger side of the car are just the result of someone noticing that the nuts and wheels on that side of the cars were constantly faling off. So they made a mirror image of the side that worked ! Remembering the 2nd rule of engineering : "Everything works on paper." | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 718 Registered: 6-2002 |
Jeff - don't get serious on me. I was merely trying to provoke exactness - the antithesis to "bunk". Clearly there are forces at play that are significant enough to have manufacturers make left-hand thread. I find it most interesting that the Lotus did it different than the Italians, and other Brits. Bunk is a good thing. My MG (in 1970) had left-hand thread on the right side. By the way - I suspect that the "pins" that James G. and you refer to are for indexing, and not for driving the wheel. By indexing, I mean that one always puts the wheel on in the same way - which allows the balance of the wheel and drum (disk) to stay constant when the wheel is removed and replaced. The pins, as on my Dino, are not of sufficient strength to stop or drive the wheel. I believe it is the KO and associated friction that provides for braking and drive application to the asphalt. Jim S. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2362 Registered: 10-2002 |
Bill The P4 is spline. The Lola is pin. The MK-IV is spline. The duesy is pin. I think Jeff is correct. | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 452 Registered: 10-2002 |
James...I was kidding when I said it's all "bunk". I was just trying to keep things on the lighter side. This physics stuff can wear on you. I still believe that when torque is applied to a cylinder or cone shape that it's length will decrease, or grow shorter. To grow longer would suggest a "stacking" or "wedging" action in the material. Actually both scientific explanations make sense to me, mine (...of course...) and Dr. Mike Adams. I simply need to understand the torque appplied -versus- length change part. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 493 Registered: 5-2001 |
James S, I concur this is a complicated subject and we may not solve it here. Judging from the posts, Ferrari and others apparently look at it differently than did Chapman. I am quite sure that my Elan is set up properly according to the factory manual. The Elan is a pin driven example. James G states that all his cars are uniformly set up opposite to mine. Are they all spline drive or a mixture of spline drive and pin drive? Do the Ferrari manuals have anything to say on this matter? | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 717 Registered: 6-2002 |
Great discussion. Bill and Phil - contrary to your general feeling (and mine except for the following experience) there is more to this than "smoke and mirrors" or "bunk." When reversing the spines I witnessed two wheels exit my car on the first application of the brake. I got religion. There is some force at play here. Bill - your explanation is similar to Dr. Mike's. I find it interesting that something as well known as the reverse threads on different sides of the car is not understood by any of us in this esteemed group. Jim S. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 492 Registered: 5-2001 |
Dr. Mike, Thanks for your input on this thread but I wonder if you would be so kind as to clarify an issue for me. Are you saying that a cylindrical member, subject a torque, will lenghten axialy in response to the applied torque? I did a quick search in my Mark's handbook and can find no mention of this phenomenon. Perhaps Roark might have some more in-depth solutions but I don't have a copy handy. Do you suppose an FEA model with one end fixed and an applied torque on the opposite end would show and axial lengthening due to the torque? Thanks, Bill | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 450 Registered: 10-2002 |
I was chatting with one of our engineers and I kind of sketched out the components and told him what was going on. He said two things: 1. Impulse Momentum 2. Coefficient of Restitution. So we kinda figured it this way. Car is going forward. Driver hits the brakes. The wheel and splines do have some clearance. So the first action of the wheel is to slam against the splines in the forward direction. Then as the twisting force acts on the spindle and makes it grow a teensy bit shorter, and at the same time this pulls the lug bolt tighter against the wheel. The wheel has now started it's rebound backwards (bouncing off splines) and as it does so with the added friction to the lug bolt turns it backwards to - tightening it. I say it's all bunk anyways! Boy am I gonna sleep good tonight! | ||
| Dr. Mike Adams (Drmike)
New member Username: Drmike Post Number: 31 Registered: 5-2002 |
Yep. Typo. I just got one of these "split" keyboards and it is driving me nuts as I learn to type the proper way, after 20 years. You'd think I'd double check something s basic a Poisson's ratio though I don't remember the exact properties of Poisson strain under torsional moments. I do remember that it is not nearly so simple as under tensil, compression, and shearing moments, as the forces are not isolated. Hence, the "or not" at the end of the post. It did seem counter intuitive to me that it would elongate. I would have to do the math. But it may even be different for cylindrical and conical sections, etc. I'd have to pull out my Mark's handbook to get a definitive answer. But I suspect that the center portion of the shaft shrinks in diameter under torsion, causing elongation. It seems this is what would happen under plastic deformation. I had to make some strainguage torque transducers several years ago, and remember having to compensate for axial distortion. But, I forget the details. Mike Kumor at seaport mold makes an excellent socket for the 2 & 3 eared and aso the 8 sides spinners. It is bronze with a rubber coating to protect the chrome. It works with a standard 3/4" torque wrench. So you can set the nuts to spec. | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 449 Registered: 10-2002 |
Dr. Mike Adams - Thank You for explaining this most confusing subject...but I do have a quesiton. I remember a bit about Poisson's Ratio and stuff, but not about Poisson's Strain. It seems to me that when something is in torsional strain, the length would get shorter instead of longer. If you take a piece of wire and twist it, it will become shorter. How is it that the spline shaft can get longer? I hope you don't mind me asking...but I'm the type of guy in that if I can't picture it in my brain like animation or something, I just don't get it. Thanks. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2356 Registered: 10-2002 |
Phil I made a wrench with a detachable head that grips the 3 eared KO's on my 3 cars with different inserts (teflon) and works great. | ||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 2043 Registered: 1-2001 |
Dr. Mike -- (Forgive a totally minor point on your good post, but) don't know if you just mis-spelled it or if you mis-heard it, but it's "Poisson's strain" (or more usually "Poisson's ratio") in the old tradition of using an individual's name to describe some physical effect and/or numerical constant. Your post was right on though about the friction/relative movement/strain of things wiggling about and acting as a sort of one-way clutch to loosen things (which is the final result even if we can't explain how  ). Rob L. -- I want to nominate Phil H.'s post for "post-of-the-month". Phil -- Do all the F centre wheel nuts have some sort of female tapered cone seat to "squeeze" the end of the (male-tapered) wheel spline onto the hub spline? I noticed in the TR WSM that the centre wheel nuts are (cleverly?) that way. I also recall my father having some mid-50's Mopars where one side had LH threaded lug nuts even though it was a 5-lug design -- quasi-unexplainable IMO! | ||
| Phil Hughes (Ferrarifixer)
Junior Member Username: Ferrarifixer Post Number: 75 Registered: 7-2003 |
It's always interested me too, and until I came to Australia and became heavily involved in motorsport, I didn't have an answer. All Ferrari's with centrelock wheel nuts have undo in DOR (direction of rotation) nuts, regardless of spline, peg, dowel drive or whatever. Now, I've been up close and familiar with the V8 supercar racing series for a while now, and also had many in depth discussions with various highly reputed engineers...... It seems there is no common answer among them. The V8 supercar series has only 2 different cars in it. Ford and Holden(GM). Yet, among the 20 or so different teams, there are all variations of centrelock arrangement, and whenever one of the teams has a wheel fall off, they re-invent it again. Some teams have it based on front axle one way and rear axle the other, some left side or right side, and some have standard RH threads all round, But none have LH threads all round. Gents, it's a gimmic, it's all to do with smoke, mirrors and trapdoors. I think I'm right in saying Aston DBS V8 has 5 wheel nuts, instead of a centrelock, and their theory is the opposite to Ferrari...but is that because of 5 nuts, not one? Who knows? File this one in the x files. In the meantime, the only useful advice I can give is to use a small offcut of carpet to protect the wheel from wayward blows, and on really tight ones you can't get off, just keep pounding it while using as many four letter words per second as you can!! Use a heavy copper or lead hammer and try to follow through each blow, hold the handle at the bottom and don't try to stop the hammer! Sounds silly, but many people create effort for themselves with poor hammer technique!! If your lead hammer is buggered, you can remould them quite easily as it melts at low temperature. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 716 Registered: 6-2002 |
DrMike - excellent discussion. Thanks for clearing that up for me. It makes sense. I will pull my mechanical engineering texts to study the elongation of a cylindrical member under torsion. Do you live in Emerald Bay? I see a black Daytona Spyder exiting from there periodically. Bill S. - there is an unexplained discrepancy regarding your/mine threads and which side of the car they are on. I believe it is worth investigating. Jim S. | ||
| Dr. Mike Adams (Drmike)
New member Username: Drmike Post Number: 30 Registered: 5-2002 |
The curved arrow is usually marked "smonti" ( disassemble ). It should always point in the same direction that the wheel turns during forward travel. | ||
| Dr. Mike Adams (Drmike)
New member Username: Drmike Post Number: 29 Registered: 5-2002 |
Here's how it was explained to me. The left/right hand threads affect mainly the front wheels. In the rear wheels the forces of accelleration and braking, more or less, cancel each other out. That's why it's usually a front wheel that comes loose. The fit of the wheel to the splin is not perfect. There is a degree ( not literally ) of indexing that occurs between the wheel and the spline. The nut is friction coupled to both members. There is a balace of friction that occurs between the threads on the spline/nut vs. the wheen/nut surface. As braking forces and relaxation cause the indexing, the nut scrubs against the spline threads and the seating lip on the wheel hub. Here comes the sneaky part. When the spline is under torsional stress, it elongates due to something called "poison strain". This can be less than a thousanth of an inch. Making the spline shaft longer temporarily decreases the friction during the scrubbing between wheel and nut while braking forces are causing indexing in one direction. But the friction returns to normal when the brakes are released, the shaft re-shortens to normal, and the indexing causes the parts to scrub back to their non-stresses position. The imbalance in friction, caused during the back and forth scrubbing, causes the nut to "walk" in the opposite direction to that of the wheel travel, when the brakes are applied. It's kinda like a ratcheting action. This is compounded by the effects of the toe-in. The toe-in in the alignment tries to force the wheels away form the nuts, and in twords the spline hubs. Also reducing friction between the wheel and the nut. This force is greater durring braking, and causes a futher imbalance in the same direction. That is why the nuts always tighten in the reverse direction. Right hand thread for driver's side. Left hand threads for passenger side. It is also why some cars with independant rear suspensions will spec an toe in for the rear wheels, instead of 0/parallel. ... Or not. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 491 Registered: 5-2001 |
James S, Yes, it's possible, that's why I checked my shop manual. It says "RIGHT-HAND threads on right side of the car. LEFT-HAND threads on left side of the car". No kidding, the capital letters are in the manual. Perhaps Enzo had a different view of the consequenses of the physics then did Colin Chapman. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 715 Registered: 6-2002 |
Bill - is it possible that someone, in the distant past, dismantled your suspension and inadvertantly switched left with right? (As I did in my youth). I'm being serious here. If you noticed that they came loose on your Elan, perhaps it is because they are on the wrong side. All of my knock-off Ferraris have a left-hand thread on the right side of the car (C4, TR, Boxer). Jim S. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 490 Registered: 5-2001 |
James S, That may be true on some cars, but the word UNDO is cast into the face of my KO's, along with the arrow. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 714 Registered: 6-2002 |
Bill S. - I believe the curved arrow is to indicate the direction that the knock-off turns when the car is moving forward. Jim S. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2230 Registered: 11-2002 |
>>JRV What say you?<< Oh No..I'm not in this...{ } | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2355 Registered: 10-2002 |
JRV What say you? | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 713 Registered: 6-2002 |
Bill - yes - good idea to check them periodically. However, the wheels on my MG passed me by as a result of my own incompetence. Once burned... One learns by making mistakes. Make the same mistake twice and your an idiot. Jim S. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 489 Registered: 5-2001 |
One other item I noticed on my KO's is that a curved arrow on the face shows the UNDO direction, top of the KO to the rear. | ||
| JRV (Jrvall)
Intermediate Member Username: Jrvall Post Number: 2229 Registered: 11-2002 |
{ } | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2353 Registered: 10-2002 |
Bill On your car do you tighten to the rear on both sides? | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 488 Registered: 5-2001 |
Napolis, Just to clarify, at least on the fronts, the axle is fixed to the upright. The hub, its attached KO adapter, brake disk, wheel, and KO all rotate as a unit. This combined unit is retarded by application of the brakes. Jselevan, That must have been a very scary moment with the MG. A KO loosened up on my brother's +2 Elan about 2-weeks ago, but he detected it while driving, pulled over and tightened it without damage. I guess it's a good idea to check these puppies from time-to-time with a good whack of the hammer. It's not good to be passed by one of you own tires. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2352 Registered: 10-2002 |
James On ALL my cars you tighten to the rear on both sides. Stop the nut. Turn the axle forward. It's the same thing as stopping the axle (at rest) and turning the nut to the rear. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 711 Registered: 6-2002 |
James G. - first question - relating to Bill S's observation - is your passenger side (right side) spline thread left or right handed? Second - per your description of the wheel having moved outboard to come free of the indexing pins. Let's examine the front wheels first. If the wheel is turning freely against the knockoff, and the vehicle is traveling forward, why would that not tend to loosen the thread? Jim S. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2350 Registered: 10-2002 |
James The wheel is no longer driven. The axle is turning freely inside it. The nut is jammed and it and the wheel are coasting with the axle turning inside them tightening it as the car moves forward. James | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 709 Registered: 6-2002 |
Bill - this is getting VERY interesting. I once rebuilt the front end of an MG, and in my youth, inadvertently switched the right and left side splines. When I took the car out for a test drive and when braking, surprise, both front wheels decided to take the path less traveled. I lost both wheels on a major highway. The moral of the story is, 1) It is important, the left and right hand thread, and 2) THE PHYSICS doesn't care what make car you drive. One of us has a major problem. My passenger side splines are left hand thread. Everyone chime in here. Please. Jim S. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 487 Registered: 5-2001 |
James, Sorry I referred to you as Jeff in my last post. It's getting late here and I'm tired. I apologize. Bill | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 486 Registered: 5-2001 |
Jeff, Interresting observation. I checked my Lotus earlier and confirmed that its right side KO's are indeed right handed and the left side KO's are left handed. Bear in mind that at least on the Elan, it is possible to swap the KO adapters side-for-side as they are bolted to the hub. I just checked my Elan shop manual and it clearly states "RIGHT-HAND thread on RIGHT-HAND side". I don't know if it's possible to miss mount your KO adapters on the wrong side of your car but you should consider this a possibility and check it out. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 708 Registered: 6-2002 |
Bill S. - but the passenger side is a left-hand thread. James G. - Please walk through this scenario again. It appears, after reading it a few times, that the unpinned wheel, jammed against the spinoff, will tend to loosen it. Jim S. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2349 Registered: 10-2002 |
Bill My Lola, my P4, my MK-IV, and my Duesenberg ALL tighten to the rear on both sides of the car. The braking inertia is a non issue as the nut is jammed. | ||
| James Glickenhaus (Napolis)
Intermediate Member Username: Napolis Post Number: 2348 Registered: 10-2002 |
Tighten to the rear. Braking forces which are greater than acc. forces will loosen the nut. But a properely tightened nut will be jammed by the wheel which can't rotate because its splined. If tighten properly they will stay on. (Mine did for 24 at LeMans and for 20K street miles) That said on a pin drive set up if the nut loosens and the wheel falls outwards off of the pins and rejams the nut what will happen? The axle will turn inside the rejammed nut and the unpinned wheel and it will tighten IF it tightens to the rear. It may not engauge the pins but it won't come off. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 485 Registered: 5-2001 |
Jeff, Consider the right front wheel. During forward travel both the KO and wheel are rotating clockwise when looked at from the side of the vehicle. If one then brakes the wheel, the wheel will want to stop rotating while the KO will want to keep rotating. Clamping force on the disk and attached wheel and will tend to oppose the rotation of the KO, yet the rotational inertia of the KO will tend to want to maintain rotation in the clockwise direction. This is the direction of tightening for a right hand thread. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 706 Registered: 6-2002 |
Bill S. - you are correct, except that the right hand side of the car, the passenger side, has a left-hand thread. To tighten the spinners on the passenger side, one turns them counterclockwise. Jeff Green, it appears, has worked with knock-offs. He has it correct. Seems like a simple problem. We all know the answer, we simply can't agree on what it is! Jim S. | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 447 Registered: 10-2002 |
Bill...in reference to your last posting...if the wheel bolt wants to keep rotating at speed during braking it will be loosening - not tightening. The wheels would be slowing down and the bolt wanting to keep rotate faster than the wheel would be the same as removing the bolt. Correct? | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 446 Registered: 10-2002 |
I would tend to agree with you Henry. While the mass of the wheel bolt and it's inertia theoretically can affect how tight it is with changes in the rotation speed of the wheel, it's affect would be small. The only thing I can imagine affecting the bolt is vibrations and lateral load as you stated. Once a bolt starts to loosen, it takes much less force to keep loosening it. Once it's no longer "bottomed out" the friction keeping it in place is lost, and vibrations do the rest. I still think that there must be some "direction" of vibration considered caused by the vehicle's forward motion that affects the bolt. Otherwise they wouldn't have opposit threads side to side. MY THEORY: Vibrations cause "moments" where the bolt sees less friction or resistance to maintain motion with the wheel. When this happens the bolt has less force keeping it in constant motion and it tends to decelerate in rpm. With the car in forward motion, and the bolt experiencing these infinately small moments of deceleration, you would want the bolt to tend to tighten in the opposite direction of the wheels rotation. I hope this makes sense. Side loads would be an extension of this idea in that as forces go from one direction to another (side to side), that bit of a "moment" would occur although to a greater degree then going down the highway. Well, that's what I think....FIRE AWAY BOYS !! | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 484 Registered: 5-2001 |
James, Thanks for the refresher on rotational inertia. Still, I stand by my post. A right hand thread (tightens clockwise) on the right side, will tend to want to tighten during breaking forces. The KO will rotate with the wheel but when the wheel in is under breaking loads, the KO wants to keep going in the direction of rotation thus tending to want to tighten it. | ||
| Henryk (Henryk)
Intermediate Member Username: Henryk Post Number: 1098 Registered: 8-2001 |
The little off-set of the wheels, due to NORMAL alignment, will put a SLIGHT force on the nut, hence a loose wheel CAN fall off while the car is going straight, but again, it will fall off a lot faster while in a slalom. I think braking and acceleration have very little to do with it. | ||
| Henryk (Henryk)
Intermediate Member Username: Henryk Post Number: 1097 Registered: 8-2001 |
As Jim has stated, the wheel is on grooved spline, therefore there is relatively NO force on the wing nut when the car is in a straight line motion.......unless the alignment is WAY off, or the spline is tapered...which I believe it is not. The only thing I can think of that will put pressure, on the wing nut, must come in a side-to-side force (lateral), and that force can only be achieved when the wheels are turned, while the car is trying to go straight. A loose wheel, as on the Boxer, will fall off MUCH faster while in a high speed slalom, than going in a straight line. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 704 Registered: 6-2002 |
Bill Sebestyen - rotational inertia - remember that the spinners (or octogonal nuts) are "tightened backwards." This is my way of remembering. When tightening these nuts, you rotate them towards the rear of the car (backwards). Thus, when braking from high speed, the wheel is forced to slow by the brake action, however, the spinner's inertia would tend to maintain its rotation FORWARD, thereby loosening it. What's plan B? Jim S. | ||
| Jeff Green (Carguy)
Member Username: Carguy Post Number: 445 Registered: 10-2002 |
Hmmmmm....you know I never really thought about it. This may prevent a few good nights sleep....Thanks A Lot James! The other day I was grinding on a threaded rod that had a nut on it. The vibration from grinding made the nut spin on the rod, although I don't remember which direction it went. I wonder if anything similar happens to the wheel bolts? As far as acceleration and braking forces, it seems that the speed at which these forces are applied may cause some tightening or loosening due to the bolts inertia or tendency to resist a change in rotating speed. You know...object at rest stays at rest...object in motion stays in motion...My buddies '32 Rolls has spine drive wheels, but the wheel bolts engage their own spring-loaded spline ring to prevent movement. The spline ring must be pressed before the bolt can be loosened. It's a cool set up, that old car has so many neat things about it. The machine work and linkages are just unbelievable. But that's another subject. I would really like to know the answer to this riddle! | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 481 Registered: 5-2001 |
James, I'm not sure of the physics on this one but the largest rotational forces are likely to be during braking, especially for the fronts. If you hit a pot hole during breaking, the forces are likely to be even greater. So, right hand thread on right side and left hand thread on left side. Breaking will tend to tighten the the KO's during breaking. | ||
| Henryk (Henryk)
Intermediate Member Username: Henryk Post Number: 1096 Registered: 8-2001 |
I would think it is the "lateral" force, applied when the car is turning (like in a high speed curve), that puts pressure on the nut. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 701 Registered: 6-2002 |
Everyone understands that wing and octogonal nuts used in knock-off wheel splines have left and right hand threads for opposite sides of the car. This is proported to provide "tightening" while the car is moving, or at least to avoid loosening. Question: What are the forces that lead to the tendency for the nut to come loose? Are the forces experienced during acceleration or braking? If the wheel is prevented from turning by the grooved spline, how is force applied to the nut? Is the thread direction designed to tighten should an object hit the wing-nut, or if the wing-nut hits the curb? Conventional wisdom is neither! Thanks. Jim S. |