Internal longs - The product, Product Options

[TimT]

I am an engineer as well however I dont play one on TV and I havent stayed in a Holiday Inn (lately)

To keep them from flexing in a vertical direction, the place to add strength is on top rather than on the side as your part does

This is true for beams, that only see forces in one axis..

It will create a HEZ or heat effected zone where they WILL fail.

It depends on if the welds are transverse to the heat AFFECTED zone or perpendicular to it..

Rosette welds in a top flange probaly act as stress risers, at the root of every weld ever made there is a micro crack just waiting to grow..

I think more is going on in the longitudinals than simple beam models...914s are flexible flyers. This reinforcing is beneficial.... can more be done to make the car more rigid?

Yes

Im down for a set when they go into production

[TimT]

I have an FEA program siting on my PC somewhere... maybe Ill do a simple model of a 914 for shits and giggles (wtf does that mean anyway LOL)

[Qarl]

I agree... adding a Z-fold would add additional strength. Overlap to the top of the door frame sill and overlap to the floor pan. A lot of additional strength in the angles.

Perhaps it could be laser or water jet cut then bent afterwards with a sheet metal bender thingy (I can't remember what it's called, I'm tired).

Anyways... this and a Brad Meyer Clamshell or Resto Design longitudinal kit and this car aint gonna twist for nothing...

You wanna see something really neat? All aluminum (except for steel motor and tranny mounts), epoxy bonded chassis (no welding). One of the stiffest (torsional rigidity) cars on the planet for one of the best handling cars on the planet. This chassis weights 190 lbs. The longitudinals are box-beams...

(IMG:http://www.uselise.com/gallery/la_show/photos/tub.jpg)

[914MF]

If you added a z-fold would it be fesible to epoxy-bond it to the car and have it be as strong as welding it in without the drawbacks of welding?
Is that the frame of your lotus? (IMG:style_emoticons/default/wub.gif)

[Qarl]

I have no idea about the epoxy. I didn't even think about epoxy as a solution to the heat/stress problems of welding.

I wonder how the "glue" that some people use to attach flares to cars would work?

You could JBWeld the enforcements to the car.... (IMG:style_emoticons/default/laugh.gif)

[vortrex]

my uncle is a painter/fabricator/restoration guy. the shop he works deals a lot with concept cars. when I was thinking of patching up my rusted 914 he suggested epoxy opposed to welding. he said it is very strong. now, I would imagine you need to get the appropriate epoxy and not something from home depot!

[GWN7]

They glue 1/4 panels on now. I have been told it's stronger than welding. I'll let you know how it works on my 68 Impalla in a month when it warms up enough here to do it.

[joea9146]

Yes why not add the overlap to the top and glue/bond the panel into place.... Will also look a lot
neater when done.... Make 2 versions a solid panel for the guys that want to bond them and the
version like you have for those that want to weld them. The soild one should take less time to fabricate.

Hold the Holes on mine please....... (IMG:style_emoticons/default/smash.gif)

[eresener]

This thread has been very interesting. I am not an engineer..but a few posts ago to this thread... I asked for a lip on the bottom of these pieces to attach to the floor pan... as I looked at the rusted away portions of the inner longs, on my sons 914 project, I had envisioned a z-shaped piece that would overlay the top of the long...approx 1" wide... great minds work in strange ways.

The epoxy idea is even better... I would assume this can be done with other areas that need replacement ... even the non-stressed areas.

Remember what they used to say..."a little dab will do ya!"

Ed

[sunfloweryellow914]

It doesn't make any sense to prefabricate any pieces when you can simply free form carbon fiber or other less high modulous fabric to be laminated directly to the existing structure with epoxy. I still contend that the top of the box beam is the most critical area, but there is nothing to stop you from continuing it down the side and across the pan for a space. That would be even better.

With regards to twisting, you can think of a 914 like a box with the top removed. If you take such a box and play with it, you will notice that it is easy to twist. what happens is that the angles between the corners changes as you twist the box. One way to counteract this effect is to strengthen the corners so that the angles can't change. On a 914 the front corners are already well beefed up, but the rear corners could use some help. Again that is a prime area to add lots of lamination.

[joea9146]

Some 3M Bonding Agents.

3M Bond

3M Structural


These are just a couple of the many that are available

[Gint]

Mark,

This is interesting. Nice work. I may be in the market for one of these kits when production starts up. When do you expect that to happen? Timing is a factor, and I want to hear Brad weigh in on this again, especially since his shop would be doing the installation.

[rhaas]

I would not apply carbon fiber directly over the steel. If there is any moisture in the steel it will start a galvanic corosion of the steel. The steel will rust out from the carbon fiber. You have to at least apply a layer of fiberglass as an isolation ply before the carbon fiber.

[Brad Roberts]

Damn.. look at the "BIG BRAIN" on the 914 club. We have real true to life engineers on this BBS.. COOL.

You guy's rock.


Jake.. be quiet. I dont tell people your flow numbers...LOL

The whole idea is to make money doing something you like.


MikeG.. your tub goes to dip on Thursday.


B

[andys]

Interesting thought using epoxy and /or fiber re-enforced epoxy. It does however add a whole new set of issues that would require some testing of the bond interface. Things that come to mind would be differentials in the CTE's, shock loading, joint design, and probably some other things in the mix. Selecting the proper adhesive would be most important, I would think.

Perhaps a single piece structural fiberglass pan you'd drop into the cabin onto the pan/inside longs with the appropriate shape, cut-outs, ribbing, etc. bonded in place might be a nice solution; just a thought

Andy

[Katmanken]

I usta do a lot of military and aircraft,-spacecraft stuff.

We used a lot of 3-m aircraft structural adhesive ( the green stuff) and rivets to build very lightweight aluminum structures. The glue holds the structure together and the rivets rivets pull the pieces together to ensure the glue joint is thin enough for maximum strength.

Problems with glue joints are:
A glue joint is no better than the surface it is adhered to. This means the surface must be absolutely clean before bonding. Wipe fingerprints across it and you are bonding to finger oil.

Clean the surface, CLEAN THE SURFACE, CLEAN THE SURFACE!!!!!!

Make the glue too thick and you are passing the stress through the glue, not the metal.

Glue needs large surface areas to work

The above apply to bonding fiberglass or carbon fiber to metal. Both use resin and resin is a glue.

Actually, not keen at all with fiberglass or carbonfiber to metal bonds. Each material has a different rate of expansion and temperature and or shock changes might cause delamination when you don't want it.

Ken

[crash914]

Way back when I was a rocket scientist...

I used to use hysol 934 adhesive...great stuff.

here is the web site for hysol stuff. It looks like they have been bought out by Loctite...


http://www.loctiteaero.com/index.cfm?ID=143
aerospace adhesives

There are lots of great aerospace adhesives..go look for them

[Qarl]

Yes, I think a combination of aerospace-type epoxy designed specifically for bonding the materials being used, copious cleaning and surface prep, and riveting would be ideal!!!!!!

You could have the metal piece pre-perforated (laser drilled) with small holes for the rivets. Pre-tap the rivet holes in the car body, apply adhesive and then pop-rivet away.

Yes, keeping the amount of the adhesive to a thin film is key. Otherwise, the weak link becomes the epoxy itself.

So... who's gonna be first?

[sunfloweryellow914]

If someone can figure a way of making the doors become part of the structure (and still be operable) then you've really licked the problem. I'll give a nickel to the whoever solves this one.

[Brett W]

You have just hit on the modern dilemna of chassis design. Can't make the doors a fully structural member. Wish I could figure it out, probably make a fortune doing it.