Hypothetical: What if ERM Was Used Instead of GRP?

[vwdmc16]

Many years before finally getting my D, i read every book on the car that i could, for the most part I read every article in Chronological order and was really digging the part where Bill Collins was explaining the new experimental ERM Elastic Reservoir Molding process but this was back in the proto 1 and 2 era.

By the time Lotus re engineered everything the ERM was scrapped in favor or more conventional fiberglass GRP that they were well acquainted with. In the end only a few parts ended up being made out of ERM which kinda made all that R&D a waste. One such part is the License plate frame bezel, which at least on my well weathered car was not in great shape. It seemed to dry out and become brittle.


So How do you think the entire car would have fared if the underbody has been made or ERM instead? would it be a 100lbs lighter, stronger, more fragile in a crash, or would car that sat out in the sun just turned to dust after 20 years so instead of frame rot we would have to worry about floor pans falling through?

[content22207]

The license plate surround is the only part I know for sure that is made of ERM (there is a rumor that some early rear closing plates are ERM). Owners can examine their's closely and see if they think an entire car made out of the same stuff (without the benefit of a frame, as flimsy as our's are) would have held together.

Bill Robertson
#5939

[sean]

I thought these were made out of it too:
http://www.delorean.com/store/images/PRODUCT/medium/100370.JPG
4806

[Patrick C]

Taking the rear fascia and closing panel off of Cliff Schmucker's car, there was definitely an ERM sticker on the closing panel.

[Farrar]

Should I look for an ERM closing panel on my car, or is it "not early enough" of an early VIN? I know my car was built prior to some modifications, but I was just curious about this one.

Farrar

[SamHill]

If you believe in markets at all, then someone surely would have sought the licensing for this bright idea. That no one did indicates that it was probably as viable as compressed elephant poop.

[David T]

There were severe time constraints to get the car into production. They were having a lot of problems with the molding process and probably would never have worked them all out. Crashworthiness was a big problem. Lotus went with what they knew and enlarged their "Double Y" backbone frame. The problem with that was the engine package had already been selected for the lower weight car with the moulded body/frame. This resulted in the car being released overweight making the performance anemic. If they DID make the car with the ERM process the car would have been much more competitive with the Corvette which is what DMC was aiming squarely at competing with. Probably DMC would have sold more cars and possibly the company would have stayed in business a lot longer! Like in war, you fight with what you have at the time. It all could have turned out so differently. DMC was not worried about how the car would be in 30 years, that is WAY past the product life cycle. The epoxy paint didn't last. They did try to build an "ethical" car whatever that is and they did want the car to last a long time.
David Teitelbaum

[content22207]

The epoxy paint didn't last.

Epoxy coating the frame was the worst thing DMC could have done. Our frames twist and flex very significantly, but the epoxy coating is totally inflexible. The unfortunate result is cracks and separation, exposing the very vulnerable metal underneath (the frame wasn't even primered). Painted frames would have been 1,000 times better, especially if DMC had layered it on as thickly as the epoxy. I use 10 coats of enamel myself.

Bill Robertson
#5939

[SamHill]

Epoxy coating the frame was the worst thing DMC could have done. Our frames twist and flex very significantly, but the epoxy coating is totally inflexible. The unfortunate result is cracks and separation, exposing the very vulnerable metal underneath (the frame wasn't even primered). Painted frames would have been 1,000 times better, especially if DMC had layered it on as thickly as the epoxy. I use 10 coats of enamel myself.

Bill Robertson
#5939


If you could go back as John Titor during Lotus Development, you would have definitely told them not to use Epoxy, but the nonusage of ERM would be the same. Works great for sugar wafers, not for cars.

[content22207]

Paint flexes.

I use brushed enamel BTW, not rattle can. The properties when dry are totally different. This is what my very flexible sway bar looks like after nearly two years of use:
485848574856

(Please ignore the control arms and springs -- they are currently off the car, getting 10 fresh coats themselves).

Bill Robertson
#5939

[Sidaries]

I read somewhere, that ERM was changed to GRP, because ERM was too rigid and on a 20mph crash, the whole body would have collapsed. Because safety was an important part of the DMC (and its predecessor, the DSV), the ERM was a dead end.

[content22207]

Fiberglass underbodies shatter too (can I hear an "Amen" Louie?).

Bill Robertson
#5939

[Farrar]

This is why in my hypothetical DeLorean build (which died when the other DMCTalk went down) I was talking about a carbon fiber underbody with stainless subframes a la the prototype and a turbocharged flat 4 mounted amidships -- lighter, stronger, faster, and a 50/50 weight bias.

I can't wait to see what Houston has come up with for their new underbody.

Farrar

[Rich]

Here is PJGrady's page referencing Collins' and DeLorean's original ERM-based body-frame concept. It ties in with several of the postings in this thread.

Link: http://www.pjgrady.co.uk//GenericContent.aspx?PageType=Delorean_Car&ShowContent=Understanding_ERM.html

[vwdmc16]

I read somewhere, that ERM was changed to GRP, because ERM was too rigid and on a 20mph crash, the whole body would have collapsed. Because safety was an important part of the DMC (and its predecessor, the DSV), the ERM was a dead end.



If im not mistaken, the crash test cars were ERM? at least i hope so as they just failed horribly. these were obvious protos with airbags and sliding windows, any have a close date on the crash tests?


http://youtu.be/0mjd2NTJU9g

http://youtu.be/GkRq_hR4W0I

[content22207]

September 20-something 1980:


http://www.youtube.com/watch?v=UnOGXCnTOj0

Bill Robertson
#5939

[David T]

In the beginning the epoxy paint was flexible too. As paint ages it becomes more brittle and eventually cracks. Nothing lasts forever, the intent with the epoxy was to make it last a long time, not more than 10 years. Even undercoating, which is flexible in the beginning, gets hard and cracks trapping moisture between it and the frame. The only viable alternative for a coating is zinc coating aka galvanizing the frame and even that doesn't last forever. BTW that is exactly the direction Lotus went. And ERM was a technological dead end. No one ever tried that again. At least not yet. Now there is carbon fiber but it is still in it's infancy as far as using it in a mass production car's frame. Cost is one of the bigger reasons why. With steel being so cheap and easy to work with it is hard to get something better at a reasonable cost. What we ARE seeing is some manufacturers trying aluminum for frames. Almost as strong but lighter. And it can be protected by anodizing which is better than paint.
David Teitelbaum

[Sidaries]

If im not mistaken, the crash test cars were ERM? at least i hope so as they just failed horribly. these were obvious protos with airbags and sliding windows, any have a close date on the crash tests?


http://youtu.be/0mjd2NTJU9g

http://youtu.be/GkRq_hR4W0I

I'm quite sure, that this crash test car used the later GRP body. The ERM body was much worse. I imagine something like this:

http://www.metacafe.com/watch/1441323/failed_chinese_crash_test/

[nick sutton]

I thought these were made out of it too:
http://www.delorean.com/store/images/PRODUCT/medium/100370.JPG
4806

The rear Louvre is made as a SMC moulding by Ferrozell In Germany as was the Hood cruciform and the engine cover. ERM was used on three parts. The licence plate holder;rear closing panel and a moulding under the hood (plenum closing panel?)

Nick Sutton

[content22207]

Welcome back Nick.

How about it: was the epoxy coating on ours frames flexible from the factory, or was it hard?

(My experience with epoxies has been that they dry extremely hard, which is an asset in some applications but a liability in others).

Bill Robertson
#5939

[sean]

The rear Louvre is made as a SMC moulding by Ferrozell In Germany as was the Hood cruciform and the engine cover. ERM was used on three parts. The licence plate holder;rear closing panel and a moulding under the hood (plenum closing panel?)

Nick Sutton

Thanks for that clarification!

[David T]

The properties of the paint can be controlled to a large extent through chemistry. Flexibility can be achieved but only for a limited time. Eventually as the paint ages it will get harder and flexibility is increased at the cost of reducing other properties such as chip resistance and adhesion. I don't know just how flexible the epoxy coating was originally, it may have been too stiff right from the beginning. Using undercoating again as an example, it is VERY flexible for a long time but eventually it gets VERY hard and brittle. Getting back to zinc coating, it bonds to the steel on a molecular level much stronger than paint and unlike paint it "sacrifices" itself in an electrochemical reaction to prevent the steel from oxidizing. The only other coating close to that is powder as far as longevity and extreme outdoor performance is concerned. \
David Teitelbaum

[nick sutton]

Welcome back Nick.

How about it: was the epoxy coating on ours frames flexible from the factory, or was it hard?

(My experience with epoxies has been that they dry extremely hard, which is an asset in some applications but a liability in others).

Bill Robertson
#5939

Difficult to answer - sorry but it was across betwwen the two - it felt soft at first touch and clearly smooth but applying pressure the plastic coating was hard.

Sorry I can't be more definitive Bill.

Nick

[nullset]

Nick,

I've been wondering how the epoxy was applied. Was the car dipped in a bath of it? Was it sprayed or painted on? How many coats?

If you know the answers to these, I'd love to hear them. It's SO thick in some places….. (like inside the crumple tubes)

--buddy

[content22207]

Steve Stankiewicz found no epoxy inside his (rotten) crossmembers, except where it ran down from the drain holes, so the frames were obviously sprayed, not dipped.

Bill Robertson
#5939

[sean]

Bill's Modified tube can discussion can be continued here:
http://dmctalk.org/showthread.php?1540-Bill-s-modified-crumple-tube&p=18774#post18774

[dmcjohn]

Steve Stankiewicz found no epoxy inside his (rotten) crossmembers, except where it ran down from the drain holes, so the frames were obviously sprayed, not dipped.

Bill Robertson
#5939

They were dipped.

John