Wheel nuts should be expensive!

[370HSSV]

I figure that any commercial workshop would very be happy to produce 200 nuts to your spec for 100 EUR a piece.

No I wouldn't! What none of you have mentioned is that Ti is a heat resisting Alloy. Remember how hot those brakes get? Well that heat will conduct down through the whole stub axle and nut. Ti wheel nuts are all forged, heat treated and then machined. Screwing an F1 wheel nut onto the axel at room temperature is like putting the round block through the square hole! the threads are so loose you can almost throw it on from the other side of the room.

Simply machinig a nut from bar stock isn't the best way, possible yes, not really very good though. Ti is inherently awkward to machine, requiring more time and specific tooling. Machining of a solid wheel nut to anything like a current nut would be very expensive. (I talking about the pockets that the guns locate into, machining a simple Hex for a regular socket wouldn't be so bad) That is why forging is used, for strength and for less machining. I can see that £850 per nut is a valid price if you account for everything. Design, design of drop-forging tooling, heat treatment on tooling, material, drop-forging, clipping, heat treatment, machining, machine tooling/programming, protective (colour coding) treatment. And of course the major factor time.

Unless you would be happy with 6000-series Aluminium, when cost should be a fraction. Probably lighter too.

Aluminium wheel nuts wouldn't be man-enough for the job. Wouldn't be able to tighten as much due to risk of threads stripping, damage could occur during a race from a prior pitstop that might cost vital seconds in removing the nut. Warm some Al up to about 200 degree C and try using it as a wheel nut!

Ti is the perfect material in everyway, light as Al, strong as Steel, but also resists deformation under load due to heat.

Steel would do the job, just it'll be heavy.


In this picture you can clearly see the pockets where the gun locates to. The surfaces of these pockets are rough and that is the original finish of the part after forging and before machining (It would have been shotblasted at some point also). And as you can remain the only areas of the forged nut that aren't machined.


That's your lot, 3 and a bit threads holds those wheels on. These are 2007/08 SAG wheel nuts.

[xpensive]

370HSSV;
- Die-Forged, bar-stock, HIP'd or cast, what matters is the resulting Yield-strength, where bar-stock Ti Gr.5 holds a minimum of 830 MPa. What's more is that I guess you want a material as isotropic as possible, where die-forging is perhaps not the way to go.
- Density of Aluminum is actually only 60% av Titanium's.
- Yes, Ti Gr.5 is truly a bitch to machine, which is why I gave it 10 minutes. 6000-series Aluminum (the anodizing kind) would perhaps be ok with two minutes.
But on the other hand, if you need that very shape of those "pockets", my money would be on precision-casting or EDM.
- Great picture of that SAG-nut. Looking at the un-machined surface however, I doubt if it's die-forged, again it looks to me very much like precision-cast by lost-wax method.

[PlatinumZealot]

I don't think Yield strength was a deciding factor between steel/Al/Ti though.. because you all know that Some times Al can be stronger than steel.

I think it is weight and surface hardness.

The Ti falls right in place.

I agree with 370HSSV..

[humble sabot]

Bad reasoning, but i can't find fault with the idea that the most likely material in the end be Ti.

Alu stronger than steel? In a bolt? Isotropic? That doesn't make sense to me in a bolt either. If threaded parts were meant to be isotropic, then the majority of nuts and bolts would be cast, and just heat treated after to up the grade. A nut, does not see even stresses.

[safeaschuck]

I'm sure most commercially available nut's would be made the cheapest way possible and simply enlarged to handle the stress that they are unable to withstand due to any manufacturing deficiencies.
I can see the advantages of having isotropic material in the thread area over using solid machined part from bar and I don't really know that much!
I can do science me!

[xpensive]

After a closer look at that SAG-nut, I should be surprised to learn that it was not precision-cast to begin with.
Reason being the smooth surface of those "pockets" and the limited amount of machining on the cylindrical side.

Material is another matter of course, but I don't think that thermal-expansion has very much to do with it, when the difference between steel and aluminium is only 50 microns for a 50 mm (2") object at a 100 C increase and thread-clearance should be far more than that.

If humble sabot is correct however, that this nut only has a locking function and strength is not the primary objective, a Magnesium alloy could be the way to go as its density is only 40% of Titanium's.

[370HSSV]

- Yes, Ti Gr.5 is truly a bitch to machine, which is why I gave it 10 minutes.

I would think there is more than 10 minutes of machining in that, not too much more but it all depends on machine/tooling/setup and of course the rough part (material allowances left on for machining etc.)

6000-series Aluminum (the anodizing kind) would perhaps be ok with two minutes.

Yes, your 5:1 time ratio for Ti over Al is about correct, but a side note I found 6000 series Al poor at anodising. 2000 series is far, far superior especially where black colour is concerned.

But on the other hand, if you need that very shape of those "pockets", my money would be on precision-casting or EDM.

Both methods would produce the desired effect however EDM would be v. expensive and time consuming.

- Great picture of that SAG-nut.

Thanks, I don't have it in my possession anymore but i certainly had good opportunity to have a play with it and fit it on the stub axel.

Looking at the un-machined surface however, I doubt if it's die-forged, again it looks to me very much like precision-cast by lost-wax method.

You have a point, the surface finish is indicative of Investment Casting, however I feel certain that due to the limitations of casting, (specifically material flaws/strength/grain flow etc.) I fully believe these nuts are forged. The finish is a Shotblast/peened finish and would easily give the finish of a lost wax method.

[xpensive]

I agree that 6082 doesn't give the most decorative finish, but it has a 20% higher yield-strength than 6063, which looks terrific and is often the quality you see in Aluminium nuts with that blue or red finish.
I'm afraid that I don't have a clue what the 2000-series is.

Anyway, according to scarbs, many of those F1 nuts are manufactured by Prankl from Ti or Al. Check it out.
http://www.pankl.com/

[humble sabot]

I'm sure most commercially available nut's would be made the cheapest way possible and simply enlarged to handle the stress that they are unable to withstand due to any manufacturing deficiencies.
I can see the advantages of having isotropic material in the thread area over using solid machined part from bar and I don't really know that much!
I can do science me!

most quality fasteners have their threads rolled, rather than cut or molded in. Since we see that the object in question is down to three threads the toughness of those threads is paramount, hence harder material, hence likelyhood of forging, for the same reason a forged piston is generally thought superior.

[xpensive]

I believe that in this context it is very important to identify precisely the purpose an F1 wheel-nut.

As I understand it, the nut does not convey torque in any way and axial forces should be rather low, all it does is locking the wheel in place and stops it from falling off. The thread looks rather coarse, almost Trapezoidal at that, surely to ease entry more than anything else.

The above could be an explanation to scarbs witness that they are sometimes made from aluminium.

[safeaschuck]

X, I can see where your going there. Here at last is the Toyota nut I was on about, it certainly looks like ally, and if it is, the flimsyness of that punctuated drive spigot would support the idea of a low/no load nut. How else do they keep the wheels on then? and are those big pneumatic guns really set to 'finger tight'?

[safeaschuck]

My thanks to Top Gear, if you would like to read the rest of the article you will have to buy this excellent magazine which is on shelves now in quality retailers, price £3.95.

I hope this excuses me

[xpensive]

Great info sc, thanks. And if you look closely again at the SAG-nut above, you can see the same wear-pattern on the conical-face as the pockets in the back, indicating a rather flimsy component indeed.

[safeaschuck]

Thanks X, I do have some reservation on the accuracy of design and price but it's as good a source of written info as I can find, I don't think were going to get anyone uploading purchase orders onto here! (shame, maybe next year onwards!)
My main reservation about the design would be that Toyota would have supplied prototype parts that didn't end up making into production for one reason or another, it's a common ruse, a place I used to work did it with pitons. It's actually quite a good way of making your rivals try and second guess how you made a design work and try and copy it, which is great if it never worked!
I'm not sure how relevant that is with wheel nuts though, they are pretty visible to all.
Also it seems to be missing the retaining device, perhaps this part engages the punctuated spigot and contains more conventional drive faces?


So there seems to be some consensus forming that current/recent nuts from more than one team are ally, you would be hard pressed to explain the anodizing and score marks it they were Ti??? (i think)
I also think it's fair to say that some teams used to and possibly still do use Ti nuts, having handled one (ahem) I can confirm that it was too heavy for ally.
So there has been a change in fixing systems at some point, from wheels which are torqued on to those which practically float?

[xpensive]

Again looking at that SAG-nut, the coarse thread and thin-walled turning-means tells me that it is not supposed to be very heavily torqued or pre-loaded either.

My guess is still a precision-cast Aluminium alloy, even if scarbs say they are forged, sorry about that.