Ideas for new rear subframe on Skorp

[Spanner]

I'm planning on some mods to my Skorpion - the first of which is to replace the tubular mild steel rear subframe which supports the seat, oil tank and exhaust silencer. I want to replace it with a lighter unit which I intend making up myself.

I intend to keep the geometry of the thing essentialy the same, i.e. a pair of cross braced "V"'s on their sides with the two "horns" of the "V" bolted to the existing brackets on the main frame.

I would have liked to make them out of an aluminium alloy but I don't have the facilities to weld alloy.

So I plan on using a smaller diameter (and wall thickness?) of either round or square (oblong) section mild steel (or other grade steel?)

Has anyone done this kind of thing?

I am going to have to fabricate 4 lugs of mild steel which will accept the main fastening bolts and which will be welded to the subframe. Any ideas how to do this and not have them weigh too much yet still be strong enough?

I am also looking for ideas on the minimum diameter / wall thickness I can get away with - bearing in mind that the existing subframe is probably cabable of supporting far greater loads than will be expected in normal riding life. Otherwise I shall go with "mmm that looks about right" approach unless anyone can advise a more scientific or experience based answer.

I plan on using a mig welder I have (ESAB Smashweld 190) ,cos its what I have to hand. Any thoughts on advantages or otherwise of brazing?


Thanks, Spanner

[fozzymz]

you ever plan on carrying a pillion?

[Bill Jurgenson]

here is a nice special I saw at the Dutch meeting.

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You can see some of his one-off space frame of small diameter tubes.

Lots of other goodies on this one as well, especially the Astralite wheels!!

[FUTURE]

What swingarm would that be?

[fozzymz]

SZR660 Swinger, and adjusters I reckon.

I've got one for sale.

[ZzerO]

i'd like to have a aluminium subframe too, the original one is pretty heavy. but welding alu it is the problem

@ Bill: that skorpion has a lot of goodies indeed, do you perhaps know what the axle is between the rear caliper and the frame?

that bike looks great altough i dont like the space between the tank and the rear panels