Hi - Convertible Frame Stiffening

[Carman 1964]

Now I see it, Lee, you reinforced the outside of the chassis with the 1" square beam. I'm afraid something like that was going to be too visible for a KG.
In the post I read from FJ he used an anti-roll bar cage to improve the chassis stiffness, but he also talked about welding on braces under the floor pan, in the jack pickup point area, the braces need to be at least two feet long; but it is not quite clear to me what FJ Camper is referring to. What would those steel braces look like? What shape and thickness of plate? Where would they be welded?

[Carman 1964]

According to Camper the chassis bending line to try to correct is this:

[Ol'fogasaurus]

According to Camper the chassis bending line to try to correct is this:

A good pix showing the difference between the two pans, something I have never seen before and I plan to keep.

What he is doing is supporting the wider floor which, although being different than what I did, should help some.

001.JPG

The forming of the floor as shown here is designed to do similar things. The pan (floor) relies on the tunnel and the mounting flange (that I used to add some additional support to things) so support the floor length wise while the ribbing/beading of the floor is used to support the floor cross-wise.

He is putting some additional support to the floor length wise.

Which is better I don't know but either one should/could do the job.

Lee

Additional info. The beading on the underside of the tunnel of the pan is supposed to help twisting/racking of the pan. I forgot to mention this.

Lee

[doc]

I took the liberty of changing the Post Title to "Hi - Convertible Frame Stiffening" in hopes of drawing in some expertise. Frame stiffening is not a new topic. It has come up before.

[Carman 1964]

Perfect, Doc, thank you very much.

I've found some photos that give an idea of how the rear of the Karmann convertible is reinforced from the factory.
It is possible that with a little reinforcement that structure is enough to have a sufficiently rigid rear; however, perhaps the area that goes from the rear to the front of the car (in essence, the area of the seats and doors) is the weakest and where the bending of the chassis can occur.

[Ol'fogasaurus]

IMG_0288 copy.jpg

Since I have two glass dune buggies that don't have metal tops to spread the different types of loads we get around, that is the reason why I built the body lift around the perimeter of the pan but mine is for off-road use. I then got thinking it over so I then added the doubler under the mounting area for the body to give me roughly the strength of a 4" tall rectangular tube. The body mounting area of the pan is also a structural piece for strengthening the floor of the pan.

I don't think a body lift is what you would need or want but some additional support of some kind (beside a cage) might be a good idea. Again... I don't know much about the pan of a Ghia but if possible, adding a 2" high rectangular tube might help some... assuming it is possible.

One thing to point out is that the body lift connects the side pieces from side to side where something under the pan I don't think would be possible without causing pan to road clearance reduction.

More things to think about.

Lee

[Carman 1964]

Thank you very much, Lee.
Looking at the photo I have no doubt that the rigidity of that chassis is foolproof; but you are right that for the Karmann it is excessive because it would change its appearance, and the line of the car is one of its most attractive features.
I've been thinking that, perhaps, the best way to give rigidity to the part of the chassis where the seats and doors are, and that the junction of the rear with the front can be very solid, could be to put a thin second layer of carbon fiber, as Singer do with the 911. I have to investigate if any manufacturer of carbon fiber parts offers that option.

[Ol'fogasaurus]

I re-read what I said and just to be sure, the 2" tube I didn't mean on top of the pan but underneath and in the body mount tunnel.

Just for giggles, measure the height of the inside of the body mount are is.

[attachment=0]Ghia pan side copy.jpg[/attachment

Just for giggles, could you get me a better copy of this area so I can see just what is going on. The side of the body mount is kind of busy here.

Lee

[Carman 1964]

I got the photos from this link, which explains the restoration of a KG.
Maybe from there you can get some more information.

https://karmannghia.org/Richard/71_KG_c ... ywork.html

[Ol'fogasaurus]

I did a quick look at it and the pix are busy.

One thing that I am not sure about is the distance the flanged holes are from each other. Generally speaking holes should be no closer than 2 1/2 diameters from each other. Stacked holes are the same but the center of the holes are located differently... not in line. They may be that distance but again, it was a quick look.

Interesting things to look at and into.

Lee

[Ol'fogasaurus]

I "think" I see (and read) what was done: the bottom of the "panel" was badly rotted so he built a new structure to stiffen things up; e.g., basically he (might have) removed the rotted out stiffening (and body mount) flange of the pan then replaced it with what is shown... then the inner structure was hidden.

Any pix of where you are at or what you are dealing with?

Lee

[Carman 1964]

I will be able to post it here in a few days, I don't have access to my car at the moment.

[Ol'fogasaurus]

I will be able to post it here in a few days, I don't have access to my car at the moment.

Good to hear. Builds can go quickly or, sometimes like one of mine,... can take years .

Enjoy the site as there is a lot of info here.

Lee

[Carman 1964]

I have been reading a large number of posts in various forums on how to strengthen the chassis, and I have only seen reforms like the one Lee has done, adding square or rectangular section beam at the ends of the chassis (almost always used in buggies) or using roll cage (in competition cars).

None of the options works for me, because I'm not going to use the car for competition (I want it for daily use, and I'm satisfied with having fun on mountain roads some weekends, and that is incompatible with a roll cage that would destroy the line of the convertible). On the other hand, my KG is fully assembled and in use, so I'm not interested in unbolting and detaching the body to reinforce the chassis (in case it could be done without changing its appearance).

That's why I found what FJ Camper commented in a 2007 post so interesting.
viewtopic.php?t=127619&sid=b2a26e129a3f ... 6c613324e5

If you're not racing, you can still add chassis stiffness by welding on braces under the floor pan, in the jack pickup point area, similar to what VW did for its convertibles. Here you'll have to improvise. The braces need to be at least two feet long.

I felt that this is a simple to do and perhaps effective enough for what I'm looking for. So I also looked for an exploded view of a VW convertible and found this:

https://chucksconvertibleparts.com/inde ... 71-79.html

But I can't get out of the doubt, can the reinforcement to which FJ refers be part 7? part 27? any other?

[Ol'fogasaurus]

If (and this is an opinion only) you are going to only do the pan not the mounting area (which for what you want to do... and I understand the reasoning) I would recommend using and angle iron style for a stiffener. Square tube has (and I am using it myself but only as a "doubler" to the body lift) a tendency to allow bending and it seems to like to retain the bend. An "L"-shaped piece of stock seems to work better and not want to hold a bend until you have overcome it then is does want to roll:

A cage is a very important thing when going off-road or just goofing off of any kind. A hoop alone is of close to zero in helping protect the occupants as it can fold to one side or the other plus back and forth. There are some supports to the rear that can help along with at least one diagonal. I have known several individuals who have lost their lives by not having proper protection.

Lee