L/w Strengthening

[Guest timswait]

Properly designed and built aircraft structures are very strong.

Aircraft structures aren't designed by RHE (thank god ), and are built out of 7075 generally, and have some kind of damage monitoring regime to check for fatigue cracks.

I think the guys who are adding reinforcement are very sensible, it's not just static loads (such as the weight of the engine) the chassis has to support, but cyclic (fatigue) loads, dynamic loads (cornering, braking, accelerating and bump) and crash loads which are by far the more testing.

My main concern from looking at the demonstrator was the lack of anything resembling a safety cell around the cockpit, in fact it looked like the cockpit area would be the weakest link and the first part to crumple in a crash. Make sure when you're reinforcing the engine bay and rear end that you don't make these so stiff that the only crumple zone left in the car is where you're sitting!

On the subject of rivets working loose, I think most people are also bonding the joints, if a joint is well bonded then the rivets will be carrying little load.

[Guest ScotMac]

I agree, cockpit safety is not its strong suit. I was thinking of adding some type of unobtrusive full roll cage around the cockpit...maybe "hidden" underneath the "lip" on the side panel...tho that would take up some of the already very limited seat space. What do others think??

 

Cheers, -sm

[Guest warwick7735]

Hi

Everybody seems to be talking about the structual strength of the car. I'm a biker and when I go out for a ride you take the risk that the next corner you go around might be your last, it's a chance you take. I bought the LW for more sunny day thrills and safety wasn't paramount, if it was I'd of bought a Volvo.

[Guest ScotMac]

I agree that w/ any fast driving and any performance car, you are taking a bit of a chance. But if you can minimize the risk w/out impacting the performance, then you can live to ride that motorcycle another day!!!!

[Guest timswait]

Risk is always a compromise, I think everyone is prepared to accept some extra risk for the performance and thrills a sports car gives, but it's still sensible to minmise this.

There's also a performance aspect in that a strong chassis tends to also be a stiff one, and a stiff chassis will handle better and allow stiffer spring rates to be used than a bendy one. Yes I know Tricky said something along the lines of "I'm amazed how stiff the l/w is", but I think this is more from seeing his dog jumping up and down on it than any quantitative test program!

ScotMac - That's exactly what I had in mind when I looked at the demonstrator. When I saw it the lips around the side panel were just formed by bending the ali over, but not riveting it back on itself, so creating an open section. If you bond/rivet some box section inside these lips then you change them to closed sections. A closed section is typically several times stiffer than an open one in bending and torsion and much more resistant to buckling in compression.

[Guest salty_monk]

Can't be a bad idea... Just got to try not to add too much weight & make sure the cockpit isn't the crumple zone as has been said

 

The biker's attitude of "the next bend might be your last" is a pretty selfish one if you have any family....

 

Most sensible bikers also minimise risk by driving halfway sensibly & wearing the correct leather's, expensive lids etc You always see some dick out in shorts & T shirt though...

 

Dan

[Guest ScotMac]

Besides Warwick, most of the strengthening i have talked about will actually increase the performance of the car. In fact, even the strengthening of the cockpit will create a better handling car (as long as not too much weight)...a good example is that the hard top version of car almost always handles better than the convertible version of the same car.

[Guest salty_monk]

Scot,

 

It's 3 o clock on a Saturday... you should be in the garage not at the puter!!

 

Agree a stiffer chassis is better as long as your mods actually do serve to stiffen rather than just add weight.

 

I too would not be happy with those open boxes at the top of cockpit sides, if you look at all good tubular/square tube chassis's they even have cross bracing down those side panels, could be pretty nasty without them in a side or straight on impact....

 

Having said that, Dave T proved the old stainless monocoque's were plenty strong when he hit that post straight on at Barkston... may be worth comparing designs...

 

Dan

[Guest Battery Bill]

Dan

Having said that, Dave T proved the old stainless monocoque's were plenty strong

 

Good point, but I think Tak should be braking earlier as well after his Barkston experience

 

I was quite keen on the lightweight, untill I saw one at a show. I was put off by the front wishbones being mounted in aluminium square section.. I wouldnt want my wishbones to tear out from fractured moutings braking at 70mph.

[Guest ScotMac]

Dan, i can't do shiit until i get this diff figured/planned out!!! Wish i could!! :angry: :angry:

 

Please see my other post, in the wanted section...maybe i can figure something out..

 

BTW, i am only about 8 feet from the garage...does that count?? ;-)

[Guest salty_monk]

Why don't you plan to make it removeable? You could do something about that, bung anything in there, get it built & mess about with options later on.... maybe less frustrating & would give you more time.

 

The viscous LSD has the Lobro Joints & is generally a 3.62 which should be ok with your power output of the duratec (although I don't know the ratio's of the T5 box you're using in comparison to a Type 9). Easiest way for you for now may be to get one of those shipped over. They're fairly cheap & not that rare.

 

Dan

[Guest ScotMac]

Yes, the removeable Diff would definitely be desirable, in terms of flexibility. However, i am not sure it is possible...well, at least w/out substantially changing the l/w chassis. See the following post that i transplanted from "chit-chat" on the subject.

[Guest ScotMac]

Transplanted from "chit-chat: taking cars stateside":

 

For the removeable diff, here is the shot of the diff ("15") panels that i posted previously, which gives us a pretty good idea how they go together:

 

http://scotmac.com:8080/locost/build/15.panels.jpg

 

Here is shot that gives us a little better idea of the "15" panels relationship to the square structural members, and shows the back area of the diff as a possible access point:

 

http://scotmac.com:8080/locost/15.panels.1.jpg

 

It is key to note that those square members are not only providing structural entegrity for the diff, but also supply the rear suspension mount points. So, w/out totally redesigning the rear end, it will be difficult to move/change them.

 

Note also, they are 11 1/2" apart in the direction of car travel, and 7 1/2" inches apart up and down. Because of that 7 1/2" inches up and down, w/out moving the square members, there is no way the diff can be taken out the front or the back of the diff box (not enough clearance). So, the only possibility is to take it out the top or bottom of the diff box. The bottom has the tunnel bottom, which is a major structural entity of the car. I don't think it is a good idea to cut a trap "door" in it. That leaves the top. And i am not sure even that is really possible. Have to see WHAT the space between the square members lines up w/, in terms of the space above the diff box.

 

The removable diff could be difficult, w/out major changes to the l/w...

[Guest salty_monk]

Looking at the pics I can see what you mean now...

 

Looks like making 15A removeable along with the boot floor or taking it out from the bottom are your only routes.

 

Can you get to the bolts from underneath without moving anything?

 

Common sense tells me out the bottom will be better, how much extra space do we have sideways & front to back? or how much could be created?

 

Enough to build a frame in the lower plate or a frame around the diff itself to put back the strength?

[Guest ScotMac]

Fixed the second pic (link was pointing wrong).

 

In terms of space, see my previous post about the space between the square members. That is really all that matters, in that they are the core entities around the diff.

 

Going thru the bottom is difficult, w/out substantial structural degradation. Take a look at the first picture on Warrick's build photos:

 

http://scotmac.com:8080/locost/warrick.build.lw/index.htm

 

The *length* designed in that tunnel bottom section is what ties a lot of the back of the chassis together. Cutting it up would not be good.

 

Cheers, -sm