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Type 35 bonnet fabrication
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Author:  longyard [ Tue Jul 19, 2011 12:21 am ]
Post subject:  Type 35 bonnet fabrication
I have been told that a Type 35 bonnet was made from only two pieces of aluminum. The welded seam parallels the top of the bottom row of louvers. A quick examination of the Simeone collection's car seems to confirm this. However, I cannot figure out how the top piece was made to have a compound curve along its length, and then have two different curve profiles at the firewall and the radiator. This is not as simple as it looks.

Does anyone know exactly how these bonnets were/are fabricated? I've spoken to someone who made an excellent reproduction in the 1970s who told me he used 6 pieces welded together, but I've also been in contact with someone who told me he has seen new ones made as the original with two pieces.

Any tips, links, or information would be much appreciated.

Attachments:
File comment: Notice the compound curve along the length of the bonnet. From about 1/3 in front of the firewall in bends noticeably inwards. The profile also changes from the firewall (tight radius) to the radiator shell (more open radius.)
bonnet.jpg
bonnet.jpg [ 100.82 KiB | Viewed 19561 times ]
Author:  nicefloor [ Tue Jul 19, 2011 3:05 pm ]
Post subject:  Re: Type 35 bonnet fabrication
I am in the middle of fabricating a T-35 hood now. First off, explaining years of sheet-metal forming experience is tough, but....

First, I would make a really good wooden form so you know what the shape is, and you know when you have achieved it.

Doing each half in 2 pieces is correct. the weld seem is right above the lower row of louvers as you mentioned. the upper piece (with the compound curve) can absolutely be made of 1 piece.
You need to stretch the aluminum to form the compound curve area.....but not the edge that mates up with the lower piece or the hinge edge.

this is done on a large power hammer (if you have one) or an english wheel. There are methods of stretching the aluminum over a form, but that is much more equipment intensive. You could also do it with a hammer and a sand bag, then use a planishing hammer to smooth it all out, but symmetrical replication is difficult.

The fact is that it is a difficult piece to make if you have never done an metal shaping and don't have a power hammer, planishing hammer, and the appropriate hand tools.

You also need to hem the edges, which can be difficult around curves but is certainly attainable.

Then you have all those louvers !!

I would be happy to talk with you about this some time.....let me know if you would like to do that.

Dan
Author:  Herman [ Tue Jul 19, 2011 3:10 pm ]
Post subject:  Re: Type 35 bonnet fabrication
There is a forum on sheet metal shaping: www.metalmeet.com

A few reads make the process clear. It is all about stretching and shrinking metal.
Author:  longyard [ Tue Jul 19, 2011 3:54 pm ]
Post subject:  Re: Type 35 bonnet fabrication
Dan,

Thank-you so much for your informed response. It is VERY helpful! I have a shot bag, English wheel, Helve hammer, and even a power hammer with shrinking dies, yet before I began to pound metal I wanted to know a good approach. You've given that to me. Anyone who thinks the Type 35 hood is "simple", doesn't understand shrinking and stretching metal! The Type 35 bonnet is a beautiful example of Molsheim art that is often overlooked because of the more obvious charms of the engine and spoke wheels.

SO.... Can you, or anyone, tell me the method Bugatti craftsmen were mostly likely to employ? I doubt they used English wheels, but maybe they did? Certainly shot/sand bags, but what method did they use for planishing? L'Ebe, I believe, noted that her father had "800" major tools at his factory. English wheel? Power planisher? Has anyone ever published an inventory?
Author:  nicefloor [ Tue Jul 19, 2011 4:22 pm ]
Post subject:  Re: Type 35 bonnet fabrication
You probably won't need your shrinking dies for this one .....mostly stretching. the helve hammer is a neat tool.

Check out metalmeet as Herman suggested. Also metalshapers.org.....I have some albums of my Pullmax up there. Tons of information.
Author:  longyard [ Tue Jul 19, 2011 5:34 pm ]
Post subject:  Re: Type 35 bonnet fabrication
Yes, I've been on metalmeet and metalshapers for a number of years. I attended Metal Meet in Oblong, IL two years ago and had a great time. I tend to be more interested in HOW a car is made than how fast it goes, or how much it's worth. Bugatti's building techniques are a fascinating mystery to me.



nicefloor wrote:
You probably won't need your shrinking dies for this one .....mostly stretching. the helve hammer is a neat tool.

Check out metalmeet as Herman suggested. Also metalshapers.org.....I have some albums of my Pullmax up there. Tons of information.
Author:  Jean B [ Tue Jul 19, 2011 5:40 pm ]
Post subject:  Re: Type 35 bonnet fabrication
Hi Guys,

In the Netherlands there also some very good craftsmans who can do the job.

http://www.bensmetalshapingshop.nl/

or

http://www.carrozzeria.nl

or

http://hietbrink.com/

Greetz,

Jean B
Author:  barttore [ Tue Jul 19, 2011 6:54 pm ]
Post subject:  Re: Type 35 bonnet fabrication
Can I add Ton Blankespoor to that list:

check out his work:
http://tonblankespoor.nl/projecten/huid ... racer.html
http://tonblankespoor.nl/projecten/huid ... 500gt.html
http://tonblankespoor.nl/projecten/afge ... -1948.html

And he knows his engines and gearboxes etc. aswell

http://tonblankespoor.nl/
Author:  Herman [ Tue Jul 19, 2011 7:06 pm ]
Post subject:  Re: Type 35 bonnet fabrication
Why not suggesting these addresses on the links section of this site?
Author:  Jean B [ Wed Jul 20, 2011 4:50 am ]
Post subject:  Re: Type 35 bonnet fabrication
Hi Guys,

Don't forget Bert Nijhof as a coachbuilder.
Bert has done some Bugatti's, I have seen some 37 body's in his workshop, at least one 43 and now a Brescia

Jean B
Author:  nicefloor [ Wed Jul 20, 2011 6:51 pm ]
Post subject:  Re: Type 35 bonnet fabrication
Make it yourself - much more rewarding than writing a check.
Author:  longyard [ Wed Jul 20, 2011 7:08 pm ]
Post subject:  Re: Type 35 bonnet fabrication
nicefloor wrote:
Make it yourself - much more rewarding than writing a check.



I totally agree! What I'm making is a replica of the Type 52 for my grandsons. It won't be an exact replica, because I won't be doing castings. I'll also be using some available "C" channel for the chassis instead of forming them out of sheet steel. It will be electrically powered, though. The dimensions are also a little different. I'll be using 10" wheels as the original, but a body whose length is closer to the second version.
Author:  37quest [ Thu Jul 21, 2011 5:54 pm ]
Post subject:  Re: Type 35 bonnet fabrication
the T52 front axels are being made again: http://www.brineton-eng.co.uk/vintage/vintage-main.htm
£475 seems good value to me
Author:  Lazarus [ Thu Jul 21, 2011 6:47 pm ]
Post subject:  Re: Type 35 bonnet fabrication
37quest wrote:
the T52 front axels are being made again: http://www.brineton-eng.co.uk/vintage/vintage-main.htm
£475 seems good value to me

I can supply these for half this price....I have patterns for all T52 parts.
Author:  geodoc [ Sat Jul 23, 2011 6:42 am ]
Post subject:  Re: Type 35 bonnet fabrication
Herman wrote:
There is a forum on sheet metal shaping: http://www.metalmeet.com

A few reads make the process clear. It is all about stretching and shrinking metal.


Great resource here:

http://www.tinmantech.com/html/gallery.php

They have tools, info and classes!

Check out the aircraft stuff .................... beautiful.
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