Heavy Metal! Part Deux - The Carbon Copy

[Jonny042]

PS - metal delete panel available from our host:

https://www.pelicanparts.com/catalog/shopcart/PERF/POR_PERF_RENN19_pg58.htm?srsltid=AfmBOorUch9-4cX7N8xYtWHwqDOalDaB_LyyEs_oA-GzChMfYqwHnFDH

[Focker]

Jonny, as my dad would say "That panel is slicker than whale ***** on an ice floe"

[chrisbalich]

^^^You Canadians speak this whole other version of English.

[Brookieslayer]

Originally Posted by chrisbalich

^^^you canadians speak this whole other version of english. :d :d

:d:d:d

[nospiners]

This panel is a godsent for someone that needs to do this. I did the metal panel delete 2 years ago on my 86 backdate and it took minimum of 3 full days of work between welding , then smoothing and prepping the metal for filler ,then sanding and more sanding than i care to remember..
Thank you Jonny042 for all you do for this community !!

[Jonny042]

Originally Posted by nospiners

This panel is a godsent for someone that needs to do this. I did the metal panel delete 2 years ago on my 86 backdate and it took minimum of 3 full days of work between welding , then smoothing and prepping the metal for filler ,then sanding and more sanding than i care to remember..
Thank you Jonny042 for all you do for this community !!

You (and everyone else!) are welcome. Really I'm just trying to fill the voids in the market, of which there seemed to by several sunroof sized holes!

I feel like there's a need for nicely made, sturdy, and lightweight bits for these cars. At a reasonable cost, of course.

The decklid hinges are a bit of a diversion - I should probably working on lower hanging fruit, but these have been calling out to me, and will be a perfect accompaniment to the decklid.

Keeping on topic for a technical forum - can it be done? Of course carbon fiber is stronger and stiffer than steel, by weight. And by quite a bit, too. But that's by weight. A figure often thrown around is 10 times as strong. But that's probably a part purely in tension without any bending forces, concentrations of stress around fasteners,, non-ideal load paths, etc.

In other words, who knows. The only way for me to see if this is going to work is to try it! Any the experiment will pay it forward to future Jon when he goes on to try make some other part of questionable benefit and weight savings!

So the hypothesis of the experiment is this. If I reproduce a stamped steel part from carbon fiber, with exactly the same thickness and geometry, it will be 1/5th the weight of the original part. And given that carbon fiber is stronger than steel by some order of magnitude, said part will as strong or stronger than the original one.

I already know the answer to this, and it is "NO". The orientation of the fibers in the cloth would have to be optimized, and most likely the design drastically changed, for it to be so. The material properties are simply too different. For the experiment to be a complete success, stamping the part from a lighter material like titanium would be a better starting point.

BUT!!!! If I change the hypothesis to: If I reproduce a stamped steel part from carbon fiber, with exactly the same thickness and geometry, it will be 1/5th the weight of the original part. And given that carbon fiber is stronger than steel by some order of magnitude, said part will be strong ENOUGH to replace the original one.

In this case these carbon hinges will only ever be used to hold on/up a carbon decklid which is only a fraction of the weight of the original steel one. Amazingly the original steel hinge design from 1965 lasted until 1989, and along the way did more and more work including hold up some fairly ridiculous appendages, plus AC condensers. So it was obviously well overbuilt. Herein lies the opportunity to lighten things up a fair amount.

If you got his far, thank you for you patience. I'm out of coffee, so here is a final teaser pic of the pattern, so we can all get on with our day!

[Edoyle]

Hi Jonny, you're making us Canadians very proud. All artists sign their work so I am glad you have done the same.

I am ready to buy that sunroof delete ''plug'' as soon as you say ready.

[shoooo32]

My Pablito is a fat pig of a targa so it's unlikely I'd notice the weight difference... but I want all these parts anyway. Knowing this level of craftsmanship is bolted on the car is a different type of satisfaction.

[Jonny042]

Originally Posted by Edoyle

Hi Jonny, you're making us Canadians very proud. All artists sign their work so I am glad you have done the same.

I am ready to buy that sunroof delete ''plug'' as soon as you say ready.

Thank you! Comments like that really mean a lot.

I'll DM you about the plug, I do have final fitting to do but am 100% confident that other than minor adjustment of the outer dimension of the boding flange, it's a "go"!

[Jonny042]

Originally Posted by shoooo32

My Pablito is a fat pig of a targa so it's unlikely I'd notice the weight difference... but I want all these parts anyway. Knowing this level of craftsmanship is bolted on the car is a different type of satisfaction.

Let's get him on a diet! I have a whole shelf of IB parts in the queue... starting at the back where these cars need to lose it the most.

[Brookieslayer]

Originally Posted by Jonny042

Let's get him on a diet! I have a whole shelf of IB parts in the queue... starting at the back where these cars need to lose it the most.

Hmmmmm…. A lot of those parts look very familiar, even from waaayyy over here

[Jonny042]

Originally Posted by Brookieslayer

Hmmmmm…. A lot of those parts look very familiar, even from waaayyy over here

Who knew that would be Another Man's Treasure?!

Your donation to the cause is much appreciated!

[Jonny042]

Hello all, quick progress update!

I now have a mold for the decklid hinges!





Also, the original hinges have bushings welded into them which would be difficult to reproduce by by molding. I sent a sketch to a very helpful pal of mine, who is very generous with his time, and his 3D printer...



And he sent me this pic last night:



The plan is to print the bushings from CF reinforced filament and bond them into the hinge arms.

[mike sampsel]

Originally Posted by Jonny042

Hello all, quick progress update!

I now have a mold for the decklid hinges!





Also, the original hinges have bushings welded into them which would be difficult to reproduce by by molding. I sent a sketch to a very helpful pal of mine, who is very generous with his time, and his 3D printer...



And he sent me this pic last night:



The plan is to print the bushings from CF reinforced filament and bond them into the hinge arms.

Jonny_rotten_911,

This reads like a good Asimov novel. Great science fiction indeed! Enjoying it very much staying up late a night to read it all again. Thanks for the great work!

[Jonny042]

Originally Posted by mike sampsel

Jonny_rotten_911,

This reads like a good Asimov novel. Great science fiction indeed! Enjoying it very much staying up late a night to read it all again. Thanks for the great work!

Thanks for that! Although when I think back over the past year and a half, I think it's been more like a horror story than science fiction!!!

Luckily I am (finally) having some better luck, and getting more consistent results, both with pattern making and mold making, and the layup/infusion process.

That said, I failed to infuse a shiny new featherweight pair of hinges today due to a microscopic hole in the vacuum bag. One thing that really helped the learning curve has been to buy a very expensive digital vacuum gauge that reads to a precision of .001 inches of mercury. Like so many other things, it pays to have the right tools!

[Jonny042]

After the vacuum test failure I had a few days ago, I finally got a good infusion on the first prototype hinges!

Here they are, under full vacuum, mid-infusion, with the resin flowing into the cloth from the bottom:



And, baked and cured, fresh out of the mold, with all the layup and bagging materials removed:




A rough trim:



I am really happy with the result. They weigh nothing!!! Some of you might remember that I was hoping to make these 1/5th of the weight of the original hinges, with adequate strength to serve the application. Success on both counts!!!



Less than 1/5th of the weight with a little more trimming to go:





Overkill? Perhaps. Just the way I like it!

[Brookieslayer]

Originally Posted by Jonny042

After the vacuum test failure I had a few days ago, I finally got a good infusion on the first prototype hinges!

Here they are, under full vacuum, mid-infusion, with the resin flowing into the cloth from the bottom:



And, baked and cured, fresh out of the mold, with all the layup and bagging materials removed:




A rough trim:



I am really happy with the result. They weigh nothing!!! Some of you might remember that I was hoping to make these 1/5th of the weight of the original hinges, with adequate strength to serve the application. Success on both counts!!!



Less than 1/5th of the weight with a little more trimming to go:





Overkill? Perhaps. Just the way I like it!

Just enough…..

[chrisbalich]

Man, I need a set of these to stabilize my ducktail.
(for science of course)

[Gonbad]

Originally Posted by chrisbalich

Man, I need a set of these to stabilize my ducktail.
(for science of course)

Ducktail stabilization is way overrated! I kind of like my tail loosey goosey.

[Jonny042]

Originally Posted by chrisbalich

Man, I need a set of these to stabilize my ducktail.
(for science of course)

Sorry, Chris, although the experiment was a success, the carbon hinges are not as stiff as the OG steel ones and not sure if they'll be up to holding up a FG ducktail, that's a pretty hefty load.

Actually that reminds me, I'm supposed to be making a ducktail out carbon. So many parts, so little tooling resin...

I probably should be doing more fruitful things but this is happening instead:



The hinge pivot bolts feel stupidly heavy compared to the 50g hinge. Plus all of this needs to hold up a decklid that's going to be 1850g in its final version. This all gets back to the fact that the factory hinge system is capable of supporting 12 pounds of decklid and 25 pounds of Carrera wing and an AC condenser.

Apparently they beefed up the hinges for the 964, but I feel they may have overdone that version too... (not my car BTW. Or wife/gf/daughter )



Here is the offensively heavy hinge bolt, nut and washer:



And its replacement. I have it on good authority that the pair of these will use 3.39g of filament to print. Each side with the bolt and a flange nut (we don't need no stinkin' washers) should be 10g or so.



Yeah, I know, if I emptied the change out my pockets before I go for a drive it would be a greater savings... but that's not the point