Hi All,
#1 Dependant has an issue with 78 1275LS. Seat mount nuts have pulled through the crossmember.
Anyone had this issue and have a good repair plan ?

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction

I think I'd be doing something like cutting the section out and welding a couple of pieces of angle with captive nuts inside the crossmember, then plating over it again

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did I tell you that I won a trophy?

i have a crossmember section from a 77 leyland suitable for a repair section
free to a good home

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65 panel van Sprog
73 panel van Iggy

I repaired a few cars by drilling right through front to back with a 12mm drill. Then weld in a piece of 12mm steel bar tapped 1/4" UNF at front. I brazed it in for neatness. Both ends.

Edit
I need to do 2 on my car soon.

Edit 2
This repair method is for Minis with the brackets bolted to front of crossmember. The captive nuts crack out with fatigue because the crossmember is just too thin.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Just to add on this topic.. One of mine has a bad thread. Is there enough meat on the captive nuts to tap out a new thread?

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Probably, but check if its cracked up around the nut, if so see above.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Indeed

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction

Thanks all. Good ideas in there. The section is mighty thin, so it's no surprise they pull through. Will probably need to beef up the rest while I am at it.
My welding skills aren't anywhere near good enough to tackle this, so I / we have some thinking to do.

Thanks for the offer Ian. Might take you up on it. I have a 72 shell about to be disposed of which seems to have thicker material (Haven't really checked). Maybe I'll cut and shut out of that and then weld in nuts for the seats.

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction

Reminds me of the issue with the cross-member not being properly welded to the floor in the factory in 1976. The Drawing Office Instruction below explains.

I wonder how many of those dealer-welded and unwelded (escaped the rework) cars exist today? Do you have one?

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

I would want to work out why on earth it happened in first place?!

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67 Deluxe
Dry suspension
1293cc, 11:1 comp, RE 282 camshaft, 45 Weber, extractors etc
4 synchro close ratio gbox
Cooper S brakes, no booster
Stealth box, as Doc says "goes harder and idles!"
RH tank cos I needed it crossing the Nullarbor etc..

Which seat mounts were fitted to your dependant's car? I thought the seat mounting captive nuts were in the front face of the cross member?

Cheers

... which you can see in the diagram posted above.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Late model Clubmans had a seat mount to the top of the cross member. This is an Aug 78 car. 1275 LS with a different style seat mount (Std from factory). Not sure when they started with this, may have only been the 1275LS model.
There are also captive nuts on the front of the cross member (as per Winabbey diag) which have plugs in them for the original style mount.

PS. Have seen this arrangement on other 1275 LS cars as well.

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction

Poor design. Over time the skin stretches and then cracks as shown. It is thinner than I expected when I had a close look. The original mount has a shear component to its strength so (in my opinion) is a stronger mount.

The captive nut should have more material around it to spread the load. (As for a seatbelt mount)

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction

Here is a pic of the seat and frame. The seat frame rail is a sliding type for front and back adjustment. Luxury

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'78 1275 LS (Under Repair, Dependant #1's car)
'72 GT Powered Clubman (Mine)... Under (re) construction