FrankenFerrari - V12 Ferrari 308

In reply to Syscrush :

LOL....but I'm also hoping this tuns out well :)

BTW - I'm the one you emailed you about my CBX. Thanks again for the feedback. :)

A few more renderings. Counterbores fixed and sharp edges broken....I told them to start production.

Odd timing but I got a string or emails from a 308 buddy telling me about braking a stub axle and losing a wheel at an AX last weekend....and wondering how WE are going to fix it. 

Stub axles failures are a known issue....it used to be confined to wide slicks at the track but with DOT tires getting better and better it appears to have entered the "street" car world.  Dead cylinder aside this was supposed to be suspension rebuild year so probably more to come on this topic.

Looks proper. Did you get clarity on how the redraw differs from what you submitted?

Somewhat surprised they ended up with a sort of "cylinder in a cylinder" effect between the spokes and the barrel of the wheel.

MechWrench said:

Somewhat surprised they ended up with a sort of "cylinder in a cylinder" effect between the spokes and the barrel of the wheel.

That's cosmetic, left over from the "must look like an OEM 308 wheel" requirement.  Dead weight for sure, but not a lot of weight.

I suspect the 308 wheels have trying g to make them lot like 3 piece wheels which were state of the art circa 1975.  The GTO in 84 where cost was almost a nonissue got actual 3 piece wheels...that's why I think thats the look the designers were going for as the ring is just dead weight on the factory wheels too.

Syscrush said:

Looks proper. Did you get clarity on how the redraw differs from what you submitted?

nope...still waiting on that.

mke said:

Odd timing but I got a string or emails from a 308 buddy telling me about braking a stub axle and losing a wheel at an AX last weekend....and wondering how WE are going to fix it. 

 

Stub axles failures are a known issue....it used to be confined to wide slicks at the track but with DOT tires getting better and better it appears to have entered the "street" car world.  Dead cylinder aside this was supposed to be suspension rebuild year so probably more to come on this topic.

Right now it looks like there is a plan coming together to use a C5 bearing/hub assembly with an aftermarket stub axle that can be had with a 930 CV ....which is the 308 CV.  About $300 in parts per side, then make custom carriers to bolt it all on... maybe  another couple hundred per side in material.

930 parts would also work but they are more spendy.....and more blastphamus ;)

Syscrush said:

Looks proper. Did you get clarity on how the redraw differs from what you submitted?

They just showed it's and its not completely clear where they made changes. A little more rim thickness in the front, a little less in the rear...they used 3.2mm for both, I used 3/3.5.  The weight is up a light at 25.3/26.2....the front includes what is effectively s spacer stuck on to set the offset right so the 1 piece is lighter than the 550 front plus spacer, the rear is 1/2 lb heavier, again probably in the hub. They they left a little more material on the of the spoke where they meet the rim because their endmill wouldn't reach....that looks small and I approved that request about a week ago but its probably the majority of the weight increase.

it looks like they added a little more meat the the spokes between the ribs.  I had a constant 8mm cross section, they have what looks like about 8 growing to more like 12 near the hub.  this must be the area they were consernd about the strength on.

mke said:

A few more renderings. Counterbores fixed and sharp edges broken....I told them to start production.

I like it.  A nice, classic Ferrari wheel design that's appropriate to the age of the car.

I hate to ask, because the old saying goes that if you have to ask you can't afford it, but waht does a set of china made one off wheels run? Theres some wheels i would love to have, that haven't been made in forever, but not if its going to cost me a grand or more each....

In reply to stuart in mn :

That is what I was going for so THANKS!

Dusterbd13-michael said:

I hate to ask, because the old saying goes that if you have to ask you can't afford it, but waht does a set of china made one off wheels run? Theres some wheels i would love to have, that haven't been made in forever, but not if its going to cost me a grand or more each....

They are shockingly cheap....which is why I risked the deposit and placed an order.  Price depends on the size, how much machine time,  and I assume who is doing the design (or ost of the design) work but the quote for these wheels finished in silver paint (powdercoat is same price) is $255 each plus shipping of $270  The quote for a 17" version was $235 ea.  A 2 or 3 pcs design might be closer to $300-350.  The 17" set I told the guy who asked $500ea + shipping if I do the design work, I don't know what China would charge for the service but as I said they did want to make a few minor changes to what I did on the 18" wheels and ghat seems to be included in the quote....I don't know.

Remember though...there is no promise of anything other than it will be to the drawing you give them so everything is on you as the buyer to check and double check. There is no DOT marking/number so they are race only unless you want to do the work to certify them.  Also this assumes the design will fit on an existing forging....this was a bit or a design challenge for my wheels since things in wheel design have changed quite a bit since the 70s/80s making an actual copy of a 308 wheel impossible without a custom forging or casting.

And while we're learning stuff - how does custom forging work? Do they machine forging dies to your spec and use them, or do they forge wheel blanks and then machine them to your spec?

Syscrush said:

And while we're learning stuff - how does custom forging work? Do they machine forging dies to your spec and use them, or do they forge wheel blanks and then machine them to your spec?

They have blanks, you can see the outer profile in the drawing I posted and in a model it looks like this.  The way I do the design is I model the forging first, then makes cuts to end up with a wheel.

Is there any risk of the forged blank distorting after parts are cut away, as internal stresses from the forging process may become unbalanced?

In reply to Syscrush :

That is always a concern with forgings. The solution is a roughing pas and then a finishing pass. That allows the stresses to do their thing before the final (finishing) pass makes it look nice. Same thing happens when cutting tooling from large billets of material, the residual stresses always start to deform the billet, so a plan to make multiple cuts/passes is the solution.

In reply to Syscrush :

Stafford1500 is right on, but when I was running production machining on forgings (another life) we would send the roughed out units for stress relief to our heat treater, usually an anneal, then re-heat treat to spec, before final machining.

Steel forgings usually had the most internal stress, followed by ductile iron, with aluminum having the lowest...but usually internal stress is a function of changes in thickness or radical upsets (90 offsets or necked down a lot).

I truly wish I believed that they take the care with my $255 Chinese wheels (that in all honesty would likely retail at 500-1000 in the US) that a company like HRE does with their 2000-3000 wheels.  I'm sure HRE does rough and finish passes and their forgings are designed in multiple steps to get near optimal cold work into the metal.....I don't believe I'll be getting that. for 10% the price.

They say the forgings are 6061-T6 which means solution treated, then cold worked a specified %, then aged.  I suspect the wheels will met T4 specs and not much more.....as in they most likely buy the billet T0 then hot forge then heat treat....which gets no chance of micro cracking due to over work but is a T4 process.  I might be wrong and they due a 2 step forging....but the only real impact is the metal needs to be a little thicker to product similar strength and these are cosmetic items if I'm being honest so an extra pound isn't going to matter.

Then onto machining and I'd bet money they do it in 1 lathe and 1 mill operation on each side.  I know they lathe first...and the rim there is very little coming off, its pretty balanced  and the wheel and the stresses are round so I bet they ignore any stress related deflection there.  The center might move left or right in below pic  but the exact locations on the right (outside) don't really matter so they probably finish the outside and leave a bit on the mounting surface.  Then to the mill, cut the outside, flip it and cut the inside (left) and face the mounting surface and call it a good enough wheel.  Just guessing but that's probably how I'd try to make it.

I think you're probably right. I have an acquaintance (former coworker) who has worked at several of the big aftermarket wheel companies (started at Boyd's) and he's shown me in-process stuff that 10 years ago would've been $5k, that are now selling for 1/3 that...all custom. Evidently a lot of boutique brands are made by the same couple of shops.

He says that sometimes a forging looks good until you get close to print and then they have to scrap it and start another because of some weirdness in the forged blank, like a cold-shut or foreign material that had been on the die when it was pressed and was consolidated into the blank. He said that it's most common with blanks sourced overseas, but he didn't specifically say China, I got the feeling it was Thailand or Vietnam.

That's a pretty accurate guess and how I'm use to seeing wheels cut. Blank is cut down to final dimensions on the lathe and then any bolt pattern or spoke design is cut on a mill. It's fun when you get a bad forging in and it flies apart on the lathe. This why that lathe has an enclosed cabinet with a fairly heavy door. 

Exciting day....there is now a real wheel just off the mill and I have an appointment this evening for a possible Craig's list score, more to follow on that.

Wow that was fast