OK... I have been reading and looking at pictures and have a question...

what would happen if the two subframes on a mini were somehow welded together (naturally in the same location) such that they were fixed together like a normal car subframe. Would that allow you to cut the roof off a Mini for a potential roadster project..??

second question

with other roadster projects, how does one ensure the structural rigidity of the vehicle? like how is it possible to prevent the front of the car moving upwards over a big bump and thus bending the floor pan upwards? Would welding the doors to the side and making it one piece (similar to the mokes) be suffice?

No its not a project for me... just questions more out of sleepless nights wondering...

See this thread from sc850. Particually the post with the pics down near the end of the page:

http://www.ausmini.com/forums/viewtopic.php?t=990&start=60

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Check out Ebay in the UK. There's a guy selling the plans.

smithy

arnt normal car subframes *NOT* fixed together??

or do they have chassis rails?

I always thought that they were one piece... I am thinking more along the lines of American Hot Rods though... where there is a one piece sub frame that everythign else gets bolted onto and then the body gets placed over the top of it all...

I am probably making very little sense, but i know what I mean...

I am looking up the links... sorry I didnt realise Nathans post went into all that...

not really as the roof is a major strength point in most cars especially mini's and vw's.
you'd still have to strengthen the floor area along the sills.

That is commonly known as a chassis not a subframe.

Also have a look at awdmoke's website, he's got a few pics of the chassis that was made for the moke.

Cheers, Cazmo

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72 Clubbie - Current project - Vauxhall C20XE 2000cc 16v 150hp.
78 Clubbie - Future project.

1 vw floor pans are strong with out the bodie attached ... used to have one as a dune buggy
2 i know someone in sydney who is doing a convertable atm and you need to do some work to get it right but the work he has done is awsome it is as stiff as a sailors penise who has been at sea for twelve months
makka

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If you' re askin these questions you shouldnt attempt a chop top till you understand a little more (read lots of books on the subject) then discuss it with an engineer.

The rear mini subframe has a nice front member to attach to but the rear of the front subframe is not very good.

The reason for a frame is both alignment of components and rigidity. The mini rear sub lacks tortional rigidity and relies on the rear panels, wheel arches for this. The front is better on torsion.

The engineer certing a chop top will load up the (bare shell) car at one corner and measure tortional deflection and you dont get much to play with.

Many American frames use to be flat and look like Ladders layed flat. they were good for front rear deflection but crap on tortional. You can see the older drag cars lifting a front wheel due to engine force and the chasis twisting. This has been identified and some newer (1970+) frames use triangulation to help.

On chasis design.
Larger circumferance tubing with a thinner wall is better then thick wall smaller diameter.
Chasis construction should look like you built the tubeing into a whole series of triangular sections.
Load is only ever transmitted via the tubeing so understand where the loads are coming from and attach your triangulated points to these (suspension mounts, engine mounts, seat location, steering locations)
Shorter tube lengths that form triangles give better rigidity.

My 2c worth

oop's forgot to mention the new frame sit's inside the car in the pasenger compartment the person doing it may do a few for others he already has the engineer lined up
makka

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