Self-tightening wheel spinners?


(Mitchell Andrus) #1

This was posted on an MG forum. I’m pretty sure I wouldn’t try this and I’m surprised at the result. What do you think?

"I have read and heard that wire wheels are self-tightening. Being an experimentalist I decided to see if it is true. I loosened the nut, then gave it 2 hits with my 4lb HF dead blow hammer. Next, I placed a piece of green pin stripe tape across the nut and hub and then cut it. The following picture was taken after about a 2 mile trip with a max speed of 50 mph. Looks like they do self tighten! "

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(67 OTS S1) #2

Having rebuilt my front end and accidentally swapped the hubs, I can assure you that not only are they self tightening, but if you put the hubs on the wrong side they are self loosening!!!


(PhilW) #3

Same thing happened when my father bought a used 140 back in '62. It’s better now that the hub’s are switched around.

Phil.


(Paul Wigton) #4

… which is why, based upon the advice of a now long-gone old Brit car mechanic, I never hammered the knockoffs on, till they wouldn’t turn (an action for which Ive gotten fairly substantial pushback, here).

Seat them, by hand, wiggling the wheel till there was no play, then *** THREE*** solid thwacks…done.


(Robert and Darlene Stevenson) #5

An the exact same reason that they should not be towed backwards or the hubs installed on the wrong side.


(Mitchell Andrus) #6

Someone smarter than I posted this:

"Imagine the wheel spinner is not totally tight such that there is a gap between spinner and wheel effective diameters on their cones, as per the diagram (not to scale as Doc would say, and, drawn for simplicity not accuracy).

Assuming the spinner does not slip on the wheel, both will cover the same linear distance of; Angular rotation x Pi x diameter. If we say the angular rotation of the spinner is ‘A’ and of the wheel ‘B’ (turns, degrees, doesn’t matter)

So; A x Pi x D = B x Pi x d

rearranging, A/B = D/d. i.e. the spinner and wheel travel a different rotational distance in the ratio of D/d. So long as the RH and LH threads are on the correct sides, the spinner will tighten up until the cones on spinner and wheel perfectly match, at which point D = d.

It only works if there is a side load on the wheel (e.g. the weight of the car); jack up a wheel and try it - nothing will happen. Repeat the experiment and drive in reverse and the spinners will loosen. Which is good reason to make sure they are good and tight to begin with."


(Geo Hahn 1969 Series 2 OTS) #7

Before a long trip I usually loosen and re-tighten at least the front knock-offs. I my experience they can tighten to the point of too tight making a road-side flat more of a challenge.

I was under the impression it was the flexing action of the spokes that created the self-tightening feature. But then I also believe a curve ball really curves though I have read ‘scientific’ proof that claims it isn’t so.


(Mitchell Andrus) #8

There could be something to that. As the wheel rolls the spokes at the top pull up on the center causing it to deform just a bit.


(Mark Gordon) #9

Yeah, and I understand that there is scientific “proof” that a bumble bee can’t fly. Maybe it’s an “optical illusion” that makes MLB batters fall backwards onto their butts when thrown a ball that crosses the center of the plate.


(Robert Wilkinson) #10

Alloy centre-lock wheels are self-tightening too. What is required is support of the wheel on inboard and outboard tapers, the outboard one being the knock-off. This support generates an orbital slipping motion as the contact point moves, which tries to tighten the knock-off. In the Rudge-Whitworth design, the tapers are internal to the wheel centre. Another design is to have the tapers external to those on the wheel. This works too, but the orbital tightening force is in the opposite direction. RH and LH threaded knock offs appear on the opposite side of the car compared to R-W centre-locks. IMHO.


(69 FHC ) #11

If you’ve ever hit a golf ball with top spin so the ball travels a short distance and dives to the ground, becoming a worm burner, you understand the principle of the curveball.


(Paul Breen pay palled it) #12

There’s no doubt with a cricket :cricket_bat_and_ball: ball. Just sayin’. Paul


(Mark Gordon) #13

I thought that it was obvious in my last post that I was being sarcastic.


(David Jones) #14

No, the forward motion of the wheel prevents them from becoming loose - they are notionally “automatic locking” hubs in that they they lock where you leave them, not get tighter with use. You set how tight you want them and they stay that way. I did a bit of research on this urban myth.

As Donald Bastow (ex-Rolls-Royce, ex-Bentley, author etc) looking at the Rudge Whitworth design expressed it when asked if they were self tightening - “perhaps more importantly, not self-loosening”. So if one does become loose it will not fall off although how it would come loose in the first place given they are not supposed to I am not sure. The ‘miracle’ of a self tightening nut was a product of the R-W advertising back in the day (although even they were careful to say “It is then impossible for the nut to work loose”), is quoted directly in modern texts without qualification or support and so the legend lives on.

I found this explanation of the way the Rudge Whitworth hub works but I am no wiser as to whether it claims it actually tightens, remains were it was set or does not self-loosen. And if it does tighten, how much torque can be applied in this manner:

“In its essentials the Rudge-Whitworth wheel comprised three key components: a splined hub and two pairs of matching tapers (conical surfaces), one comprising the inboard end of the hub and the inboard wheel centre, and the second the retaining nut and outboard wheel centre. These tapers served three functions. First, they automatically centred the wheel on the hub. Second, they transmitted a significant fraction of the drive and/or braking torque so as to reduce the load on the hub splines. And third, they made the wheel-retaining nut self-tightening. Imagine that the nut loosens slightly so that the tapers on the wheel and nut touch at only one point on their circumferences. Because the male taper is now of smaller effective diameter than the female taper, rotation of the wheel on the hub under braking will cause the nut to rotate on its thread. If this rotation is in the correct direction — which is ensured by using differently handed threads on either side of the car— then the nut will automatically re-tighten itself.”

This is from the Rudge Whitworth article which explains the system as “self-locking” - the cone centres the wheel and the spinner self tightens but requires a spanner or hammer to get it to that position. I think that is possibly where the confusion comes from - the spinner does indeed self tighten but only does so when whacked with a hammer:

Here is another explanation of the Rudge Whitworth hub which seems to confirm it:

In 1913 the Rudge Whitworth coned locking device was introduced. The parallel splines are a loose fit on the inner hub and a proportion of the car’s weight is carried by the nut itself. The nut tightens on the male coned surface of the end of the outer hub, and has a mating female cone machined in it. If the nut is loose there will be a gap between these two cones, allowing the wheel to wobble slightly. The car weight will now be carried at a single line of contact between the coned surfaces of nut and wheel. As there is a gap between the cones, the effective diameter of the cone on the hub is smaller than that of the nut.

The line of contact therefore rolls relative to hub and nut as the car moves. This, the theory says, can be likened to an epicyclic gear. In this arrangement, with the planet gear (i.e. the outer hub) rotating, and the planet carrier fixed (i.e. in this case always vertical), the outer gear (i.e. the nut) will tend to rotate backwards. By placing left hand threads on one side of the car, and right hand threads on the other, this tendency is used to tighten up the nut. The weight is also carried by the threads at the bottom of the nut, and the relative motion between the nut and the inner hub induced at this point is in the same direction, and also adds to the tightening action. Once the nut has tightened, the clearance between the cones is taken up and the rolling action stops. (my underline).

So confident were Rudge Whitworth of this theory that one of their patents describes a nut in which ball bearings are added to enable it to tighten itself more easily. It was only necessary to fit the nut hand tight, and after 1/2 mile or so (forward) it would require a spanner to release it.The early Rudge tapered‑cone wheel nuts were circular, and were removed with a special spanner. I don’t believe theories like this so I always knock my wheel nuts up tight, especially on the wheels with dodgy splines.The knock‑on ears did not appear until much later.

Here are the Dunlop official period instructions on the use of Dunlop Rudge Whitworth pattern hubs:

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I am prepared to be educated if anyone can come up with a plausible mechanical or scientific explanation of how two masses rotating in the same direction can tighten beyond 220lb/ft rather than remain static with relation to each other. Also if the system is self tightening just how does the spinner come loose so it can self tighten again?

Interestingly, and something I did not know, after Rudge Whitworth went bust in 1936 Jaguar acquired the rights to Rudge’s wheel business and together with Dunlop continued to exploit the design for both wire and disc wheels although by then the system was termed ‘fail-safe’ rather than self-tightening.

David


(Paul Wigton) #15

As stated in their literature— and confirmed a couple of times, using a Sharpie— they are indeed self-tightening.

I believe that is an unequivocal statement.


(David Jones) #16

A Sharpie test is not scientific confirmation nor offers an explanation of how self tightening would work. Jaguar themselves make the unequivocal statement “The lock nuts are designed to be self locking” and specifically say “not be permitted to run un-tightened”.

The RW italicised descriptions above are taken from period advertising publications so need to be taken with a pinch of salt as they were product promotion.

David


(Geo Hahn 1969 Series 2 OTS) #17

That sounds a bit like ‘It works in practice but not in theory’.

I have also used a Sharpie to mark the wheel and the knock-off after tightening well (several good blows). After driving a couple of days, movement of the marks is noticeable - about a half inch as I recall.


(Mitchell Andrus) #18

I think this is being discussed at a level that is unwarranted as the explanation is far more simple:

As the wheel moves forward, a new set of spokes at the top of the rim is put under tension. As this tension pulls up on the inner hub, the inner hub moves upward and if in contact with the spinner drags the spinner along with it. The spinner turns til tight.

The real-world model is the hoola-hoop. As it orbits it ALSO ROTATES, but always in solid contact with the body.


(David Jones) #19

So, if I have this right, two of you tightened the spinners with hefty wacks so there was no further movement and then found, magically, the spinners were able to tighten themselves up another half of an inch. How on earth is that possible? I checked the actual torque on my wheels after three blows with the hammer by using a torque wrench and spinner removal tool to a) remove the spinner and found the force at which it clicked and b) tighten the spinner then using the mallet to see if the spinner moved. Finally I found some screw torque tables which indicated for a screw of 52mm and 8 TPI the recommended force was between 180 and 220 lb/ft which is what I set the torque wrench to.

As I said the spinners are self locking and will stay where you put them. My personal experience of a loose spinner was on my Lotus Elan. A mechanic had failed to tighten it sufficiently and the wheel started knocking on the motorway at 80mph. It did not tighten itself! For that I needed a hammer (and a change of underwear). Oh, and said ace mechanic had forgotten to put the Thor hammer back in the boot. Feel free to try loosening a spinner and taking your car for a high speed run !

The self tightening spinner story is an urban myth and a dangerous one at that.

David


(Geo Hahn 1969 Series 2 OTS) #20

Yes. Certainly a loose wheel is not going to tighten itself but one that is tight will get tighter.

Urban myth? Perhaps the only way you will know for sure is to try it.