Has anyone had problems MOTing their minis with grp frontends on? I have a solid mounted subframe but have been told by two mot testers so far that it is dangerous because the front of the sub frame isnt supported properly, they don't seem to realise that the subframe supports the body and not the other way round! has anyone got any ways that they have got round this problem as I am not fitting 'brace bars' when they don't achieve any purpose other than a nice place to mount things on!
If we do anything like that here an engineers certificate of compliance is required which stays with the car and can be sighted each inspection.
This includes even a LHD to RHD conversion, Clubman kit cars, any modifications at all.
I think it would be a wise move to re think your options unless you have worked out the stress factors as I can't see a "solid" subframe hanging off the body is solid.
Sorry mate, but you are quite wrong here. The front bodywork does contribute to the strength of the structure and is not 'supported by the subframe'. The purpose of the subframe is to hold the engine and gearbox and provide mountings for the front suspension - not to provide structural strength to the monocoque. You should not replace it with a GRP flip front without incorporating additional bracing.
Regards, David Betts snipped-for-privacy@minilist.org The Mini Gallery:
Ive fitted a STEEL flip front to the front of my Mini and still installed brace bars, just in case the MOT place has a problem with flip fronted cars. Only so they have one less excuse to fail my car.......
Extract from The Old Testiment by David Vizard.............
For some forms of competition, fiberglass fronts are explicitly banned. This is usually the case for offroad events such as rallycross, autocross and stage rallying where body strength is at a premium. Even when glass fronts are allowed, some scrutineers demand supports from the original body sub frame mounting point on the front of the car, up to the bulkhead. The fitting of such stays may well satisfy the scrutineer's desire for safety, but in actual fact, such a stay does little to nothing to increase the front-end rigidity. It does give a useful mounting point for such things as oil coolers and coils, etc. This business of front stays with fiberglass fronts has been a sore point with many scrutineers for quite some time. The best way to look at it is not to assume that the engine subframe unit, which is very heavy, is fixed to the body by only those mounting bolts through the floor and through the top of the suspension tower, but the other way around, that is, that the body, which itself is pretty light, is fixed to the engine, subframe, suspension assembly via those points. It must be remembered that most of the weight of a Mini is carried within the front subframe itself anyway. Apart from this, if you study the loads subjected during acceleration, braking, and cornering, the fix ing of the subframe to body is perfectly adequately catered for by those bolts through the floor and through the towers. Another area in which body strength is a prime requirement is that of safety in a crash. The standard Mini shell is neither good nor bad at withstanding an impact; it's just about the same as any other unit-construction vehicle. With a front-end collision, it can be a little better than most because of the situation of the engine within the subframe, but to be as safe as possible for competition work of any sort, a roll cage must be fitted inside the car.
Who is going to argue with the words of the great man himself?
Notwithstanding the above I put bars on my steel flip front car (yet to take the test) because I had heard of the problem some folks had had with the MOT.
Cheers
"miniman" wrote in message news:2005090523251475249%edamman2000@hotmail...
Nice one turbojo! Thats what I call a very good explanation on these matters and we all know DV is god!!!! :-)
To further the debate a little more I would like to add that after taking it to the last MOT station which refused to test it and furthermore insisted that the tower bolts go through into the rubber springs and that I had cut out the chassis plate so that he couldn't test it, even though it is a van and never had a chassis plate as it has always been stamped on the scuttle rain channel (which I showed him!), I decided that I really couldn't carry on arguing with someone that is quite so ignorant and drove over to John Cooper Garages (The holy sanctuary to all things mini!) and spoke to one of their team, He took one good hard look at it and said "looks fine to me" , then being the ever so helpful chaps that they are they said that they would phone up the ministry and double check as it seems to be a grey area that no testers can quite get to grips with.
Today I popped in to JC garages and after having a good chat to the head technician, he told me that he had phoned the ministry and they have said ' as long as the body is held securely then there is no problems with the front sub frame being fitted without brace bars, as all the front mounts are doing is acting as mounting points for the body'
Try telling that to an MOT tester, maybe they just don't have the time to phone the ministry if they come across a problem like that!
The great man wrote those words around 1973. That was when a megabyte of computer memory filled a whole floor of a building, and a lot of things have moved on since then, including vehicle safety standards. DV said "The standard Mini shell is neither good nor bad at withstanding an impact; it's just about the same as any other unit-construction vehicle." If that was true then, it certainly isn't true now.
I knew somebody that got the engine and gearbox in his and his wife's laps when the subframe folded up and back in a head on accident, and that was with a full steel front. I really think you should put braces on it, regardless of what your local MOT man thinks. If in doubt, try to visualise that engine coming through the windscreen.
I won't argue with DV concerning a race car that is inspected regularly but on a street car there are other considerations.
Here's a little thought experiment to illustrate why the front of the subframe needs some means of location at the front.
On a flip front Mini with no "front stays" disconnect the subframe mounting bolts from the floor. You now have a front subframe that hinges around the tower mounts in the vertical axis of rotation, and to a smaller extent in the horizontal axis of rotation. Reconnect the floor mountings and motion in the horizontal axis of rotation is easily eliminated with very little stress on the mountings. Motion in the vertical axis of rotation is also reduced.
The reason I say reduced is because the towers are attached to the most ridged structure in a Mini. This is why I chose to think of this as a hinge point. The bulkhead crossmember isn't going to move. The floor mounting is, well... , attached to the floor. This is not a particularly ridged structure and it is now being subjected to reversals in stress on every acceleration / deceleration cycle. It is common for light steel structures subject to stress reversals to quickly work harden and develop stress fractures. Front stays will help reduce the load on the floor, not as well as fully welded front sheet metal but it will help. Either way, those with flip front Minis should inspect their floors regularly. If they have rubber mounted subframes I would suspect that the rubber mountings will be beaten to death in short order.
The standard steel front sheet metal provides excellent location for the front of the front subframe and takes significant stress off of the floor mount. Much better than most of the stay structures I've seen. Each wing and flitch panel form a channel style box structure with two channel cross members connecting them at the front. This is a very ridged structure in both the vertical axis of rotation and the horizontal axis of rotation. It also provides energy dissipation, crumple zones, in a crash. This is an experiment I've done on two occasions. The structure works well.
Sorry I forgot to mention that I had plated the floor area where the subframe lower mounts are with some reasonably thick steel plate to dissipate the loads a little better, my idea of solidly mounted along with all the usual metal replacements for the rubbery bits everywhere! and I have also seam welded and gusseted the whole thing just for safety's sake :-) I am still under the impression that the subframe being the heaviest part of the car is just pulling along a very light shell by all the aforementioned mounts and If I was going to worry about crashing the thing then I would fit a roll cage and bolt that through to the subframe as well!
Is there any crash test data available for old minis that anyone knows of? how does a clubby do?
Anyway, I got my MOT today (minus brace bars) and am happy that after four years of serious abuse nothing has cracked, snapped, bent, deformed, or otherwise gone a bit weird, if it had then that would be when I question my octane abuse habits!
That looks far better than some of the dodgy aftermarket ones that are doing the rounds at the moment, a lot of them just seem to be a bent bit of tube that has no real strength under compression as they would bend even more under load! I was looking at the VTEC and vauxhall conversions and noticed that they recommend fitting a removable front to make access easier for fitting, what they don,t seem to supply as part of the box section sub frames is a bracing bar to the top mounts, which seems a bit silly if they are really neccessary, have any VTEC engined mini owners had problems with subframes falling out of their cars?
Does anyone still use rubber mounts? As they never seem to last more than a year on most minis!
By definition, no one ever plans to have an accident... a roll cage in a Mini doesn't really make it safer. It just moves your head closer to a piece of steel tube. My rule is no helmet, no roll cage. You're free to make your own rule.
Plating the floor will help a bit but you still have considerable leverage working against you. It's not clear to me what you've seam welded and gusseted. If it's the subframe it doesn't help the problem I would anticipate since I expect the subframe to move as a unit. Keep in mind that I don't expect you to have a short term problems with your plan other than the lack crumple areas in case of a crash.
I don't know where you get the idea that the drivetrain and front subframe are the heaviest part of the car. The drivetrain and subframe weigh about 400 lbs. The entire Mini weighs about 1500 lbs. That leaves about 1100 lbs. for the drivetrain to pull along. This of course doesn't count occupants.
I have to agree, that's the nicest structure I've seen.
The crash effectiveness could probably be considerably improved by adding a brace from the top bend in the top bar of the side structure to the lower bar. It would keep the bend from collapsing on impact.
For all of the structure that's been added there is still a lot of room around the engine.
Don't weld it to the subframe (you have two) or attach it either. The stress is more evenly distributed through the body shell when plated and bolted in.
Structural considerations should be taken into account when welding anything to a certified body as this will alter the loadings, which in the result of an accident, my not be favorable.
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