MOT fail - split lowered floor

[tangomikeromeo]

 

MOT time and all well until I asked him to put it back in the air so I could have a closer look at a crack on the inside of the lowered floor pan. And when I pointed it out he agreed it was an issue and advised of failure.

To be fair it's not a crack it's a split about 8 inches along the inside fold of the flat part of the floor from the rear seat mount forwards. 

Seat and carpet out tomorrow to have a closer look so a few theoretical questions until then.

Is welding going to be an effective repair?

Is there supposed to be more to take the load than just the ally panel? (And before we get personal I'm under 13 stone - I need the SV for height not girth) The new part on the Caterham website looks like not but I had been told there should be a steel strop to secure the seat to the chassis to prevent the ally panel from carrying the weight. 

Is refitting something I should leave to experts? It's not drive able now (and without an MOT) so trailering is another complexity. 

And it looks like the Fish and Chip Run is doubtful

All in all a rubbish days holiday. 

[SM25T]

Just fitted a lowered floor. Chunky ali bracket from front face of chassis box section just forward of the seat down to floor. Riveted to floor with steel rivets. Lowered floor is riveted on every edge. LF is thicker ali than original floor.

[SM25T]

Sounds like ali welding should effect a good repair in situ. No need to remove floor. Perhaps with an ali plate welded over the area afterwards.

[Titanium7]

I've just received a lowered floor and there are 2 thick (4-5mm thick) strips for the flat part of the floor, also the angle cross bracket that fixes on the chassis cross rail at the front of the seat.

[F355GTS]

The lowered floor on my previous 7 split in exactly the same way. They do seem to have added strengthening plates under the seat runners onthe later ones however for yours welding should be more than adequate

[SM25T]

My new one didn't have plates supplied. Maybe latest floor is thicker ?

[6speedmanual]

Give me a call, fella. Peter

[Adrian Williams]

The flat plates for the lowered floor were originaly designed to raise the seat runner up enough to clear the angled sides not to add strength. On that basis they might not be included or indeed required on an SV as the base will be wider in the first place.

I'd get it welded and strengthened with an extra Ali plate if it's a common mode of failure.

[Roger Ford]

It's not drive able now (and without an MOT)

Has the old MOT expired?  If not, it's still valid, in spite of the recent failure.

And even if it has, I believe you're entitled to drive the car to a "place of repair" without an MOT, unless the vehicle is dangerous (which is entirely separate from whether or not it has an MOT).

 

[Ian B]

It's a fairly common mode of failure I'm afraid.

Usual fix is welding and adding another strip.

[Mavic82]

You can still get about according to the gov web site

If your vehicle fails the test

You’ll get a ‘notification of failure’ from the test centre if your vehicle fails the test. The failure will be recorded in the secure central MOT database.

You can still drive your vehicle if it fails the test and its existing MOT certificate is still valid (ie you got it tested before the expiry date). However, you might be stopped by police and prosecuted if your vehicle is unroadworthy.

If the vehicle fails the test and the certificate has expired, you can only drive it to:

have the failed defects repaired
a pre-arranged MOT test appointment

[John Vine]

I believe you're entitled to drive the car to a "place of repair" without an MOT

That's my understanding too -- there's a useful summary here.  Note that this repair trip has to be as a result of an MOT failure, but the place of repair can be a garage, your home, or anywhere you choose to have the work done.

JV

[tangomikeromeo]

Having taken the seat and carpets out I have a crack in the rear corner, tunnel side, running forward to the 5p piece.

And looking at the rear more closely.

No strop to support the seat so I assume the intent is that the floor is sufficient on its own which concurs with the above comments.

Could it be welded in situ?

If it has to come out I think a replacement would be worth the piece of mind.

 

 

 

[tangomikeromeo]

And MOT has expired. 

[SM25T]

I think the weight of that 5p coin was the final straw ! Hopefully a decent ali welder can weld it in-situ with the carpet out of the way. Find one and ask. Replacing the floor is a long-winded job ... even with an air drill and air riveter.

[SM25T]

Maybe ask Bruce at Arch if they can weld it in-situ. Not too far from you.

[tangomikeromeo]

I'm relying on that and the penny I also found to soften the blow of repairs!

[John Vine]

And MOT has expired.

I can't help about the welding, but if the MOT failure report specifically included the crack, you're permitted to drive to a "place of repair" without an MOT for this specific defect to be remedied.  The only provisos are that the repair appointment must be pre-arranged, the car must be roadworthy, and you must have insurance.

JV

[SM25T]

And you don't fall through the floor on the way !!

[Dorset7]

A new floor fitted by ARCH is about £260 - worth doing I reckon. 

[The_ASH]

Interesting that this subject has surfaced again, I remember discussions about the floor cracking on non-lowered floor cars on old-Blatchat 14 or 15 years ago, can't find it with the search function... ISTR that failure was just like this being centred at the rear inner part area of the floor pan and was a loading failure brought on by leverage backwards and downwards from the seat, as the car accelerates your weight pushes back on the seat which pushes down flexing the floor which eventually fails, the floor is also subject to flexing load as you drop onto the seat when getting in and as the car goes up and down as you drive along. As the lowered floor has shape and edges it moves the point of failure to those edges, this points to the floor pan being inadequate to support the seat, really the seat runner needs to be supported in some way from the chassis, I often wondered about being able to attach them to those points (which I think are the 6 point belt attachment points) at the rear which are indeed chassis attachments.

edited to add: thinking about this on the cars with flat floors the failure used to start at the rear inner seat runner mounting hole and crack the aluminium floor backwards and inwards towards the corner of the floor pan, as the crack got longer the floor began to drop and pull/load all the rivets at that and around that corner, it's worth looking closely at yours next time you are under the car or if for any reason you have the drivers seat out, caught early it's just a matter of getting it zapped up/patched/reinforced, if left too long the best fix is a new floor or lowered floor upgrade (if you fancy a bit more headroom or want to sit lower)... just get that reinforced before fitting perhaps :-)

[Jonathan Kay]

Yes. a couple of failures here that sound similar:

http://www.lotus7.club/forum/techtalk/sv-lowered-floor-cracked
http://www.lotus7.club/forum/techtalk/crack-lowered-floor-pan

... with some ideas for solutions. Clearly needs reinforcement, and it sounds as if it could be welded without removal.

Best wishes

Jonathan

[The_ASH]

Thinking about this further I'd bet this problem has only been around since seats with runners have been fitted in Sevens as the loading is concentrated into a couple of areas on the floor whereas on a car with a bench seat the load is spread across the floor more evenly, the same can be said for racers with bag foam seats. Over time the floor might become loose as it is still carrying the same load so the rivets and aluminium might give a bit but to get to the point where the aluminium cracks would take many times longer if ever. So the key to stopping this happening is either spreading the load by reinforcement or supporting the load where it occurs on the floor by providing support to the runners from something more solid.

edited to add: I'd forgotten that the seat runners used to be attached at either end onto chassis tubes (rather than bolted through the floor) which would have suspended or at least reduced the direct load on the floor. See these seats for sale on eBay here picture 2 :- http://pages.ebay.com/link/?nav=item.view&alt=web&id=281648248186

[Steve_K]

I concur with Jonathan. Even if you can get a good welded repair, the loads that caused the original crack are still there, so some form of doubler across the cracked area should be used to reduce the stress. Welding ally in situ can be a problem as the heat can induce weakness around the weld making future cracks more likely. Removal for welding allows the part to be heat treated after the welding is completed. It also makes reinforcement easier.

Steve

[Drumster]

I'm not familiar with the lowered floor pan but my 7 also suffered with floor problems as the seat was mounted directly on the ali floor and it also had the U-shaped strenghtening ali channels (waste of space as these just bowed anyway) underneath.

I noticed that the floor was sagging and although the ali hadn't torn the holes through which the rivets passed had become elongated allowing the floor to sag.

When I rebuilt the car I had some brackets fabricated (a bit lika an elongated top hat bracket) from mild steel (yes, I know hardly adding lightness a la ACBC  ) to fit inside the the cockpit and secured over the front cross-member and the lugs at the bottom of the rear bulkhead. This means that the weight of the seat and its occupant are taken by the support and not the ali floor. I don't have runners on my seats so the seats bolt straight through the support and the floor.

I don't think there is anything revolutionary in this as I believe older sevens had these supports anyway (?)

Photo below is not the best but if anyone wants a clearer shot I'll take a few more photos.