subby mounting plates

[dingo]

Hi guy's, thoughts on 6mm thick x 150mm high x 35mm deep mounting to hold a subframe with me @ 86kg and maybe missus 68kg?? am i better off remaking some 10mm plates? figure i ask someone who might know before i glue em on.

[latheboy]

What are you talking about..... the 6x150x35 piece, will this be welded to the frame or used somewhere else?
If thats what your doing i would do it out of 10mm, overkill to the max extreme but if you over engineer it you be safe in the knowledge that it wont fail....

[OZ750L]

Try flipping up a few pics to show what you wanna do.

[dingo]

cheers oz and lathe, have a look in 'your ride' ,'dingo's',pics in there,6mm seemed ok at the time but once i had a play they look flimsy

[Docktor]

I used 10mm. 6 is a bit sus imo

[dingo]

thanks for the input guy's, didnt take much to sway me away from the 6mm, i should have known better and done it right the first time

[OZ750L]

Go 10mm plates.

Make sure you strip the anodising of the frame in the area for the weld.

What welding experience have you got/can you get access to? Be best if you can TIG the plates to the frame. Airbox is coming out to weld it up I'm guessing? You'll need to do it as a double 5mm full penetration fillet weld with a "V" prep on the plate. For the prep, cut back either side of the plate where it butts against the frame 4mm deep and laid back at a 45 degree angle so that when you look down from on top, you see a flat bottomed V where the flat is 2mm wide.

When you go to weld it on, space the plate off the frame by about 1mm. That way you can get full penetration on your weld. Tack it on first with a couple of tack and alternating top left, bottom right, top right, bottom left. When you weld out, don't try to do it with a single pass on either side cause you'll twist it to the shithouse. Put in a 2mm root run by going bottom left, mid right, bottom right, mid left and try to weld it all as vetical up (have checked). When you get the root run done, check it out and see that it's all straight and the weld has good penetration and you haven't missed any. Next, put the first cap on bewteen the root and the frame. Follow the same process as for the root. Last weld is another cap which ties in with the plate and the other 2 welds. Might need extra on the inside edge of the frame. When finished, you can have a look at it and if need be, dress it up a bit to smooth it but don't take much oF the cap weld off as this is where the strength is.

MIG is similar but you put down a lot more weld at once and probably do as a single set of stitch welds without the caps. Weld will be all 3 TIG welds in one.

Don't cool the weld out. Let it cool down it's self. May actually be better to wrap it in a heat blanket and let it cool slower than it would in the air. Last thing you want is embrittlement of the weld. Also, when you start on one plte, keep working on that plate as quick as you can to try to keep the heat in it. Try not to let it cool out then come back to it.

Anyways, that's how I'd do it. Might be overkill but then it would suck to have it crack and break off.

Usual disclaimer here. This is just my opinion. All work should be done by competent professionals. Where it involves any alteration or modification of a structural member, it should be checked and approved by a qualified, authorised engineer.

[OZ750L]

Wondering how stable it would be to put rose joints into the bottom pair of subframe tubes so then can wind the tail up or down as you want to?

Just a thought.........

[Docktor]

a few people have done it , lets ya dick around with angles i guess. but i got it right first time .

[dingo]

i got a mate who's handy with a tig, if hes not available at the time my local alloy shop said he will do both sides for under $50, i doubt hes thinkin of putting the effort you described OZ , however i may look into that prep as you sugested,tack it on with a mig then take it in to get done. i just picked up a length of 10mmx32mm will have a play tonite hopefully. i thought about ajustables, might work on that idea on another subby.
PM your way OZ, thanks guy's