44 replies to this topic

[Bluemini]

So fitting a removable front weekens the car then, think about it... The inner wings are welded to the underside of the outer wings and bulkhead, but not conected to anything at the bottom so all they do support the outer wing and dont even touch the subframe. The outer wing is held on by the scuttle and A panel (neither of which touch the subframe in any way). The front panel is welded to the wings and held to the subframe by 2 bolts bolted thru a rubber mount which alows the subframe to move.

So those 2 bolts, bolted thru rubber mounts are taking all the 450kg of the front subframe, engine and suspension - I dont think so, they are more likely to be there to provide rigidity for the panels to stop them flapping around. If they were that structural, they would be bigger bolts than 13mm, more like the main tower bolts, or there would be more than one on each side like on the floor mounts and early subframe top mounts.

If you remove the front end and fit brace bars, your actually making it stronger because the brace bars have 2 bolts at each end, 2 to bolt thru the inner wing area and 2 thru the subframe. And to make it even stronger, they are mounted straight to the car - no rubber mounts allowing movement.

I think you'll find, if you had the original steel front end compared to a set of brace bars, there would be more side to side and up and down movement in the steel front than there is in brace bars becase the panels are flimsy.

[bluebottle]

there's almost no strength at all in fibreglass flip/removeable fronts, mates hillclimber has a one piece front, when you remove it, it flaps about all over the place.

there's no doubting the fact a full steel front end will be better in a crash, but i think the mini was designed well before deformable structures and crumple zones, so i dont think you could call the front end a crumple zone.

i've had 2 front end crashes in mini's, both of them low speed, both of them writing off the shell, both of them i was uninjured. the clubman (see pic on the left) i crashed head on with another car, and the front wing ended up inches long, the cars back was broke and the steering wheel ended up on the passenger side, all this was with me only doing about 10mph, and the other car about 40mph.

so it just goes to show you, that even with a good condition steel front, dont have to be doing light speed to totally trash your mini




as for gliders and stealth bombers, to mention these in the same context as fibreglass mini fronts, is a bit silly, as there is nothing in common.

[Cooperman]

There seem to be some basic misconceptions here. As Siggy has pointed out, the front of the car, as originally designed, forms part of the overall structure and carries the stresses in a certain way along defined load paths. The resultant structure was subsequently tested and validated as of sufficient strength.
With 'flip fronts' I really don't believe any properly qualified structural engineer ran a finite element model or performed the necessary stress calculations in the way you do with an aircraft if it is modified. I also doubt that any flip fronts have ever been tested as part of a stress analysis and validation procedure.
Thus, in a frontal impact no-one knows how the resultang high stress levels are resolved into the structure.
For this reason alone I believe they should be banned In a nutshell, they just are not proven safe.
You fit one if you want to, my neck is more valuable to me thanks.
Besides, they really don't improve access and look bloody awful.

[Jamnog]

I never did get all the bending moments and youngs modulus stuff, but i know what you mean. dont think im saying that in a colision your better off with a fibreglass front. If there was a safty isue with them i honestly dont think they would be allowed to sell them. the reason i am talking about plastic planes was to say that they can hold a force along the length of them perhaps that doesnt reflect the strength from say the side. the isues with the engin mount not being able to take any of the force of the impact and the majority of the impace being on the box structure of the wings im partially swayed by the argument as there will be a movement but you have to remeber that the momentum of the engin will provide allot of the force absorbtionbefore the toughened steal bolts start to snap.
The flip fron on the hill climbing car - just cause it flaps about doent mean there isnt an inherant compression strength that would be comparable to a steal front. The metal will bend rather than snap but it also comresses with a different sort of elasticity.
the reason it seems im sticking up for the one peice pannel now is shear bloody mindedness. and i cant stand to see just one side of any argument have there been ay crash tests done with cars? im starting to come round but i think your going to have to find me some examples. im off to look for a kevlar version this topic has turned out to be very interesting thanks.

[bluebottle]

believe me when i say that my mates floppy fibreglass front has almost no stength, and i think in a crash, the reduction of the impact due to the fibreglass would , i'm sure be negligible.


i drive a fibreglass car, and when you see fibreglass that is structural in strength, its a whole different kettle of fish, you have box sections, stengthening ribs, reinforcing etc. fibreglass fronts have none of this, they are usually a few layers of csm and gel coat, and i dare say if you had a paddy on, you could probably smash it up by hand if the mood took you! you only have to go to a few hillclimbs or race meeting to see how weak fibreglass bodywork is when its just a covering, not part of the shell.

i understand what you are saying about plastic aircraft, being designed to take a load in one direction, and being weak in another, but i still dont see the relevance to fibrglass fronts on mini's, as they are worlds apart.

having said all that, i personally think they are ok, if you like them, if i had a rusty mini, i'd be tempted, and if the front is removeable , rather than flip, the improvement in access is brilliant.

[Jamnog]

well that said then I admit I am wrong perhaps a one peice roll cage combined with all fibreglass would be safe then.

[redmini]

:wales: just a thought but has anyone considered the midus mini? Complete fibreglass body shell if I remember correctly, at the end of the day a mini doesn't compare to the modern day car ie. the crash tests which is why it was dis-continued along with the engines emissions that is.

[Madmax]

brace bars on a flip front conversion make the front end about 3 times as strong as a normal metal fronted mini, flappyplastics got a metal flip front, its way sturdier than even a standard car. nuff said, body panels on a minis front end are practically cosmetic, subframe and bulkhead is where the strength lies.

[siggy]

Sorry but gotta say this, what a load of bo££ocks. There is no way on this or any other planet that a flip front is stronger than a steel one.

The point about a steel front is its ability to absorb an impact. A glass front will distort and not absober any impact.

midus or other glass shells are strong, BUT they have built steel box section steel and are of monocoque construction. Not a sheet of fiber glass.

Siggy

[bluebottle]

i drive a mini jem, thats a fibreglass monocoque, it has steel plates where things like the front shockers mount, no actual steel box sections , but wood, and proper structural grade fibreglass.

i can testify first hand as to the strength of the car after having a crash in it ten years ago, a cavalier pulled out on me and i t-boned him, the jem had a split in the nose, not even damaging the radiator, the cavalier had a pushed in door and front wing, and the door post was quite distorted, and after talking with the owner some months later,he told me it was nearly written off.

my point being fibreglass is as good as steel when properly designed, and is of structural strength, flip fronts are little more than thin engine covers, so whilst making access easier, there is a trade off, just be aware of that.

[Alburglar]

Fibre glass is extremely strong when it's a full monocoque but not as a bolt on to the front of your mini for the reasons that siggy and cooperman have already been saying.

And the roll cage - raised insurance issue is simply because it makes it more desirable to be nicked. And so if it does get nicked then they would have to cover the cage too so they make you pay extra.

[Cooperman]

I reckon Siggy, Alburglar and I have covered this very fully.
To summarise:
If you fit any type of flip-front onto a Mini or Clubman you will reduce its resistance to a frontal impact by a significant, but unquantified amount - so, unless you want to risk getting a very nasty headache, DON'T DO IT.
No amount of bulls**t from others who have their own agendas is going to change the truth. They just ain't safe. End of message!

[mighty_mini]

i had a head on, and if i didnt have a flip front, i think i probably might not be here, or at least they'd be picking 400kilo's of engine off my legs....


when i have the chance i will flipfront my car again... theres no way it wuda held up to the impact it did, with the steel front end...

[Sfanatic]

i had a head on, and if i didnt have a flip front, i think i probably might not be here, or at least they'd be picking 400kilo's of engine off my legs....


when i have the chance i will flipfront my car again... theres no way it wuda held up to the impact it did, with the steel front end...

Bearing in mind what Siggy, Cooperman and others, whoa er obviously all experts and understand the structure and stresses in a Mini body, I don't see how you can say that.
Why do you think your safer in a weaker bodyshell? I dont make sense to me, and ive had minis for the last 15 years.
I would never put a flip front on cause I value my life too much.

[Woody]

I have "flip fronted " 2 minis (for my own use) and i can tell you the quality of the mouldings varies a lot , the clubman front i got 2nd hand was heavy duty and i doubt it was any lighter than the steel panels but it was very tough and i think it would have taken a heavy knock and added to the streanth of the front end , this of course depends on the method of mounting the front end , its no good if it flys off when impacted !
however , i had a round front mini and after my brother rammed a wall flatening the front i chiseled the panels off and started saving up , then i saw an add in the paper for a fiberglass front cheap (it was new) , this front was very flimsy and trying to be possitive i thought " ah.. lightweight" , big mistake , I was sat in the mini on day and a bloke reversed an escort van into it :sad: the front broke in half , right up the middle ( he jumped out and screamed at me "WHAT THE F**K ARE YOU DOING PARKED THERE " and drove off before i could get his number !)
it took me loads of duct tape and bungees so i could drive home .
So i wouldent use one on the road again , but i would on a lightweight hillclimb or sprint car , with proper subframe suports :grin: