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+--- Thread: Framework for Body Skin (/showthread.php?tid=1531)
RE: Framework for Body Skin - Nigel - 04-08-2018
Hello Jamie,
I used 12mm marine ply for the frames. The first layer of 1.5mm aircraft grade birch ply panels was scarfed and glued to the frame with a quality waterproof wood glue (the cardboard strips are so the staples don't mark the ply). The second layer of 1.5mm A/C birch ply strips was attached with a true industrial grade superglue - no need for clamps or pins. 5 coats of acrylic clear paint (sans pigment) and 11 years later, nothing has moved. I found building the body on an old chassis with legs welded on, very helpful. Good luck.
RE: Framework for Body Skin - Jamie - 04-08-2018
Good morning.
Thank you for all of your extremely helpful replies and suggestions.
Mark: thank you for the offer and I shall probably be in touch soon.
Looking at some of the ideas and methods used here, I think that I have been over complicating the frame in my mind, not least by envisaging larger diameter tubes which would require more substantial equipment to form effectively. Blocks of wood with MDF formers are well within my reach. I have brazing and welding equipment, although I am very rusty on my welding: practice needed, methinks.
My thoughts about using ply were that it seems easier to obtain around here, mid-Bucks, than ash, although I have not searched widely yet. I take the point about the variable quality of ply, though. I skinned the garage side door last year in exterior grade ply and painted it well. It is already delaminating as though I had used corrugated cardboard held together with Gloy paste.
I am curious, and have yet to look into it, but how do people attach the aluminium skin to the metal frames? Is it simply a matter of rolling the edge of skin very tightly around the frame, hammering it around well, or is it more scientific than that? Attaching it to wood seems simple enough, with pins, screws and glue.
I have just picked up a copy of "Austin Seven Specials" from the library, so that may shed some light on some of my questions.
Regards,
James.
RE: Framework for Body Skin - AllAlloyCup - 04-08-2018
Aluminium can be rolled round tubes , for example on the cockpit edges and the bottom
Of the body edges, but you need to anneal the it first.
Probably best to use a section of clamps hammers, hide and steel, etc.
Ok on flat areas but complicated 3d curved panels are very difficult to form
Without serious metal shaping kit and Skills!
Especially pointed or domed tail covers.
I’m still learning!
Regards
Bill G
RE: Framework for Body Skin - "Slack Alice" Simon - 04-08-2018
Odd comments from me:
Bodies for specials are nearly always over-engineered. 2" x 2" is used where 1" x 1" would do, cross bracing where the ali or ply skin will do the job anyway, etc.
Aluminium, in the case of the Cambridge at least, is folded over the corner of the timber and fixed with panel pins. Nothing more fancy than that. If the edge is seen, it is covered by a bit of half round ali screwed on top.
Ok, the Cambridge was very much made down to a price, and a lot of these new bodies are made to last. Which was not the case originally. You were just making a pretty covering for the working bits underneath.
Decide if the body is going to be part of the structure of the car, in particular, used to stop chassis flex. If it isn't, then it can be very light in construction and need not be particularly rigidly attached - ref. Weymann hanging the back end of the body on a central rubber mounting.
Decide if the body is going to take weight - mainly the fuel tank, battery, spare wheel, and luggage.
If not, it can be very light, almost filmsy.
Can someone cleverer than me run through the process of annealing aluminium? I can never remember which way it goes.
Cheers
Simon
RE: Framework for Body Skin - Ian Williams - 04-08-2018
Aluminium is annealed by heating, I apply a layer of Acetylene soot when this burn off the temperature is right, soap or a match stick can also be used, the match stick will leave a burnt line at correct temp.
Check out my building a Special Body thread here, happy to answer questions, armed with a little knowledge and a hand full of tools shaping metal is easier than you might think.
Simon Jansens Blog is also a very good and informative read.
RE: Framework for Body Skin - Jamie - 05-08-2018
Thank you for the additional information and I shall look for the Simon Jansen blog. There were a couple of things raised, which I missed, in the earlier replies.
Mark:
The car will be used for general road use, not racing or trials use.
Simon:
I had not really considered one way or the other whether to use the body specifically to stop chassis flex. If I opt for a lightly constructed tubular frame with an aluminium skin, do I need to add bracing to the chassis? A basic question, really.
At this point, I should like to make something that keeps at least a vestige of a rear bench seat, even if is only only very small. It will keep doors as I cannot envisage my wife wishing to clamber over the side of an open cockpit with low sides. I like the idea of an open car, but prefer the practicality of a saloon. I am mulling over creating something which has a canvas roof on some sort of roller so that the entire roof can be open without having a hood on a frame scrunched up on the rear of the car.
Regards,
Jamie.
RE: Framework for Body Skin - "Slack Alice" Simon - 05-08-2018
Re. Annealing
Heating - and cooling naturally, slowly
Heating, and cooling un-naturally, slowly - like leaving to cool in pre-heated oil
Heating, and cooling quickly - into cold water, for example
?
RE: Framework for Body Skin - Ian Williams - 05-08-2018
Simon, heating and cooling naturally
RE: Framework for Body Skin - Nick Lettington - 05-08-2018
What ever way you go, make sure you look at other people's cars proportions. Some are stunning and some resembe a pig in a poke... I made a 1/4 scsle model of a lwb chassis to start planning mine on, then found my dream shell on a well known internet auction site... Not in dream condition mind.
13 years in... 12 to go?
Anyway... Back to the point... With such a small vehicle it is important to get the balance between the size of the driver and seating position correct. Some 750 specials look more like the driver is riding on rather than in the car... Retaining a rear bench seat may be tricky if you want a sleek low special.
Will be interesting to see where you go with it. Please keep us posted.
Regards
Nick
RE: Framework for Body Skin - Jamie - 05-08-2018
Nick.
I agree with you about the proportions. As a starting point, I have found a really clear cutaway line drawing of a Ruby showing the seating position, a driver, the steering wheel, column, bulkhead etc al. I have printed several copies and am doing a bit of cut and paste to get a basic shape. I shall then use cardboard, string and stiff paper to try and mock up something.
I shall post on here once I get going. It will be a while yet, though, as I am putting up a larger garage for it. At the moment, I am taking time to try and plan it carefully so that I do not make an unnecessary dog’s dinner of it.
I like the idea of a scale model......