26 replies to this topic

[CharlieBrown]

From looking at photos of crashed mini the steel front end the crumple zone is effectively the front wings, the completely buckle but they must take some of the force before the shell starts to deform.

However I have seen a front end crash on a fibreglass mini and the front end bent and absorbed most of the impact then cracked or at least thats what I assumed happended (this was Al's mini at the ring).

But as someone said, if we wanted to be super safe we would all be driving volvos.

Just my thoughts on the matter

[Down&Out]

cheers so far

[Down&Out]

bumpity

[Andykettle]

People drive round in FULL fiberglass minis. Other cars on the road are made from fiberglass too like tvr's etc. You can put brace bars in and weld as much box section steel you want to strengthen it if your that worried.
I have a fg front and brace bars and just dont plan on crashing in a hurry!

[sweetser]

just dont plan on crashing in a hurry!

Thats how i would look at it lol

[Ethel]

Weight for weight fibreglass is roughly twice as strong as steel: it replaced steel in the bumpers of many cars before ABS started to be used. Of course, a lot will depend on the production quality, Lotus can produce a panel that's not much thicker than your average steel body compared to a 4 or 5mm chop strand hand made lay up. Steel deforms to absorb energy whereas GRP will just flex elastically until it fractures. So GRP stores impact energy, rather than absorb it, if it doesn't break, you'll literally bounce off small bumps - but you'll have nothing left to protect you from any secondary impacts . Fibreglass fronts are made in one piece with no joins to create weak points or stress risers, steel rusts.

The big consideration for any flip front is how you mount it, a couple of hinges from B&Q and two rubber bonnet hooks will fail long before either a GRP moulding or the rust riddled original panels.

Go overboard with bracing up the front and you'll just transfer the steel, and bone, mangling forces back in to the bit of Mini you're sat in.

[Down&Out]

give me an example of over bracing? im not clued up on this kinda thing ya see. although thanks for the advice

[Ouster]

give me an example of over bracing? im not clued up on this kinda thing ya see. although thanks for the advice

You don't want to crash in a fully rigid car without any crumple zones - physics says that force is the rate of change of momentum. As an occupant you want a small rate of change to minimise the force transferred to you, but if you had a car which didn't have any flex at all the rate of change of momentum in a crash would be much larger. Looking at it a different way, imagine driving without any suspension: it's harsh and bumpy. Add in some dampers etc and it's much more smoother.


From what I've read, fibreglass is worse than steel in low speed accidents, but there's little difference at high(er) speeds.

[Ethel]

I'm no automotive engineer...

The brace bars are just supposed to hold the shell to the subby in place of the front mountings and inner wings. On the pre 76 Minis, with subframe bolted directlly to the car, many didn't bother with any bracing and they passed MoT's.

I did once run a flip fronted Mini into the back of a Fiesta at 40mph (less a bit of heavy braking and skidding). The Fiesta ended up shorter than the Mini and I walked away unharmed. The front end fitted on the back seat in about a dozen pieces and the subframe towers were about an inch further back than before, after the engine had a go at knocking the bulkhead back. If I were to build another, I'd look at making the rear latch on to the A panel much more substantial (mine was a step up from rubber hooks with a reasonable locating tab and Dzuz fasteners). I might also add a fairly lightweight frame to locate in the bonnet landing panel area as the bumper section of my front was still attached to my subframe though the rest had ripped off between the corners off the grill aperture and the wheel arches.

Some of the Fibreglass shells with removable fronts look well thought out as the fronts look like they butt on to the flitch panel.

From what I've read, fibreglass is worse than steel in low speed accidents, but there's little difference at high(er) speeds.

Fibreglass survives low speed bumps better because it deforms elastically and will just bounce back, with maybe some crazed gel coat. Of course, that doesn't mean any passengers will have an easier time of it; but that would be down to design as much as materials. As Fibreglass, and more exotic composites, have a better strength to weight ratio there'd be more scope for building a safer structure without tipping the scales in main battle tank territory

[tedmcedd]

what im going on about would be to just take the wings and front panel off and bond the front to the inner wings and a-panels, meaning it would be there like steel panels would. perhaps if i did that with a carbon fibre front it would be somewhat better? its supposed to be stronger than steel i think?

i wonder where that idea came from....

as ethel has said, fibreglass is stronger than steel and it will absorb the shock better... the brace bars will add to the regidity of the front as well as holding the engine steady in its subframe.... i kept my inner wings and bolted my front to them with rivnuts, i also fastemed it to my a panels, its more of a solid front than a flip one, but it can be removed if desired...

[mab01uk]

Go overboard with bracing up the front and you'll just transfer the steel, and bone, mangling forces back in to the bit of Mini you're sat in.

The Mini Seven Racing Club looked into the alternatives for adding bracing / crumple zones but could find no way of adding any crumple zone into the existing Mini front end design/space so instead recommended the drivers protect their necks from crash forces with a Hans Harness as used in Formula 1 and rely on the rigid weld in roll cage bracing to provide a safety survival cell...........not really practical on a road Mini though!
http://www.formula1....f1/safety/hans/


kvQtsMpcWFs

[Down&Out]

what im going on about would be to just take the wings and front panel off and bond the front to the inner wings and a-panels, meaning it would be there like steel panels would. perhaps if i did that with a carbon fibre front it would be somewhat better? its supposed to be stronger than steel i think?

i wonder where that idea came from....

as ethel has said, fibreglass is stronger than steel and it will absorb the shock better... the brace bars will add to the regidity of the front as well as holding the engine steady in its subframe.... i kept my inner wings and bolted my front to them with rivnuts, i also fastemed it to my a panels, its more of a solid front than a flip one, but it can be removed if desired...

thanks loads for the help so far, i think ill just do what tedmcedd has done, know i know they are not as unsafe as i though they where...
thanks!