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Old 04-02-2020, 04:09 PM
metal manny metal manny is offline
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Default Building a new body for a classic Alfa GT

In the reconstruction of the Alfa GT, I needed to make a buck on which to fit and weld the collection of individually shaped aluminium panels and also perform limited hammer-forming of some details.



The ultimate goal is to build 3 body and chassis reproductions; one for my son, another for myself and a third for an as-yet unidentified customer to offset some of the costs in this project.



As far as bucks go, there is much opinion and debate on which method and material is best. There are many varieties of materials chosen to build various bucks, but after much consideration, in terms of cost, speed, accuracy and adaptability I chose to make a steel frame buck.

Here are the main reasons:

1) Weight - I needed a buck that could be easily picked up and moved if needing the space. Also, I wanted to set the buck on a wheeled scissor lift table to give me optimal working height and access. Ply or MDF would have been too heavy and prone to flexing under its own weight.

2) Adaptability - As I had planned a minor revision to the styling of the rear of the car, I thought it not practical or economical to add or subtract subtle nuances in a wooden buck. Here steel has proven to be fantastic, allowing minor bending tweaks plus additions and subtractions to various aspects of the individual frames. And believe you me, there were plenty of these... On a few occasions, I needed to adjust something by 10mm(3/8") or so, and simply cut and welded in a tiny spacer, chop, chop!


3) Durability - Due to workspace constraints, I needed a buck that could be stored out in the open. Given a coat of paint, steel is ideal!


4) Accessibility - Viewing panel fit to the form from the back side on a steel frame buck is unsurpassed. Also the ability to hold paper patterns and panels with vise grips, crocodile clips and magnets is equally impressive.


5) Cost - Steel wins this category hands-down in my location.



Copying the Alfa’s body proved to be quite simple - especially having the original car to work from.






To do this, I made a simple machine which is a large profile gauge attached to a dolly on rails. The machine tracks parallel to the length of the car and measures one half of the car’s width, with its innermost probe tracking the exact centre line of the body.







The car is propped level and the rails are set level to the base of the chassis, tracking to the longitudinal centre of the body. All linear tracking measurements are referenced from this horizontal plane. For this I used a tape measure fixed to the rail with a laser pointer as indicator.







The dolly & pin method in essence is by no means a new idea; however, for the sake of speed and accuracy, I made the plate in which the pins are located, detachable from the dolly so that said plate can be positioned on the paper plan and all its points traced out precisely.



Usually with this method, individual pin measurements are found and recorded on lofting data sheets. This is time consuming and needs a good attention span to prevent errors in measurement or position and also requires hours to transfer written data back onto final paper patterns.



The pin plate for the machine is made from 16mm MDF, with 45 degree grooves for the pins routed out at 50mm (2") intervals. Pins are made from 8mm ali tube with wooden points, and are secured in position by fabricated 'U' staples screwed to the board.


When a profile has been locked off, the plate with its pins is removed from the dolly and indexed to a 'drawing board' (shown below) at its top right corner. The drawing board has a baseline and perpendicular centre line maked on it. The pattern paper also has a folded centre crease and perpendicular base line which is indexed on the drawing board.






The position of each pin tip is traced with a dot, and when complete, the paper pattern is removed from the board, folded in half and each dot punched with an awl to make a mirror pattern.



Using a flexi-curve, steel ruler, free-hand etc, the shape is then fully drawn on one half side only. Areas of transition, where the pins miss the detail (shown below) are recorded using a small profile bent to shape and traced on the pattern.


Of note here is that when taking a reading off the body, I always referenced the individual pin locations on the car with a Sharpie dot, and also numbered the stations on the car accordingly for quick referral if something looked wrong or confusing. I did refer back to the plotted dots on many occasions to check that a mistake was not in the making.






How the buck is made:

Steel bar is bent to copy the exact contour drawn on one half of the plan. A second shape is then made and checked against the first for similarity. Tools used include a bender, rolling machine, existing circular form items (like wheel rims) and a hammer and anvil for forging tight sections, or for straightening or lightening over-bent curves.







The mirror-image forms are clamped to the paper pattern at the centre and placed over the corresponding dots, welded together, released and adjusted (bent straight) if having flexed from heat. Legs of correct length zeroed to the pattern’s baseline are then welded to the form and reinforcement and triangulating rods added for strength particularly on outriggers which are open-ended.











The forms are then aligned in marked positions on the buck’s ladder “chassis", centred to a longitudinally tensioned centre line then welded in place. Above, I welded in tubes rolled from 1mm steel sheet for the headlight recesses. Final finishing to the contour was done using a flap wheel sanding disk.



Longitudinal steel shapes are then shaped and checked against the car body using my cheap fabricated profile gauge shown below.



BTW, this is a fantastic, highly accurate tool in any shaper's arsenal and only takes a few dollars in materials and an hour or so to make up!





A note regarding choice of steel bar is that I mainly used 3/8" (10mm) square steel, which is easier to bend accurately in a flat plane. However, due to its square profile, careless placement could affect the accuracy of the buck’s final form - depending on where it is positioned relative to the recorded plot point. This will prove particularly critical on a tight curve, as shown in the attached drawing.





Lastly, the buck was built as a single unit separable into 2 bolt-together sections. This makes the structure less cumbersome as a whole and allows work on the rear of the bonnet/hood and firewall.







The completed buck, given a coat of self-etch primer and has already seen action, with the back panels of the car about halfway done. I'll post the build progress some other time as a separate thread.
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Old 04-02-2020, 05:11 PM
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Gojeep Gojeep is offline
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Excellent work and like your approach.
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Old 04-02-2020, 06:41 PM
Chris_Hamilton Chris_Hamilton is offline
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Really great info Manny. Thank you for taking the time to post it and share it with us.
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Old 04-02-2020, 10:14 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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Beautiful work on the buck Manny. One though is to make sure your car skin can come off the buck after welding Due to the roll at the bottom of the door area and A pillar, it LOOKS like it could get locked on the buck.

I had that problem with a pedal car buck and had to rework it so I could unbolt sections from inside and remove the buck from the car skin.

Your car may not have that problem but at first glance I can't be sure so I thought I'd mention it.

I'm looking forward to the build. If the skins come out as well as the buck, I can see a MetalShaper of the Month down the road.
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Old 04-02-2020, 11:15 PM
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Awesome job Manny!
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Old 04-03-2020, 03:08 AM
skintkarter skintkarter is offline
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Top stuff Manny! Look forward to seeing progression on the build.
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Old 04-03-2020, 04:07 AM
Jaroslav Jaroslav is offline
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Copying a shape is the most complex. Seeing it is every small mistake manifested. Beautiful work of Manny.
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Old 04-03-2020, 04:22 AM
metal manny metal manny is offline
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Marcus, Chris, Robert, Richard & Kerry, thanks for the compliments.





Quote:
Originally Posted by Kerry Pinkerton View Post
Beautiful work on the buck Manny. One though is to make sure your car skin can come off the buck after welding Due to the roll at the bottom of the door area and A pillar, it LOOKS like it could get locked on the buck.

I had that problem with a pedal car buck and had to rework it so I could unbolt sections from inside and remove the buck from the car skin.

Your car may not have that problem but at first glance I can't be sure so I thought I'd mention it.

I'm looking forward to the build. If the skins come out as well as the buck, I can see a MetalShaper of the Month down the road.

Kerry, you're absolutely correct about the possibility of the body getting trapped on the buck, and I looked very carefully at the Cobra buck build posted here by my friend Kabous, where he built a structure capable of extracting the forms from within itself for this exact reason. It is not impossible that I'll need to still do further work to resolve these and other issues as they present.

The fender rolls are a concern as they roll over 90 degrees plus, but am hoping to only partially roll, say 90 degrees, and "spring" the body off the buck, hand finishing afterwards. The headlight recesses also present an entrapment problem, so will be shaped, fitted and indexed and welded off the buck. Not at that crossing yet, but will update the forum once I get there.
Anyways, whatever I eventually end up doing, the good news is that the steel buck approach allows me flexibility to do a relatively easy fix.
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Old 04-03-2020, 11:50 AM
metal manny metal manny is offline
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Thank you Jaroslav.
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Old 04-03-2020, 01:00 PM
crystallographic crystallographic is offline
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Hi Manny,
Beautiful steel buck. Looking forward to seeing your progress.


For escaping panel entrapment, another common way that I see when restoring the vintage racers, is to break the panels at the water line/equator, and when welding lower sections to upper, the chassis can provide locations for doing this. (I know Dick Troutman did this when building the 3 Scarabs.)

The chassis' really don't offer much to support the body shells with most of the racer designs anyway - probably the most minimal I have seen is the Lotus 11, having a minimal box-shaped tube chassis with an envelope body covering it all up. Seeing the two units apart leave no hint at all that they would ever go together.

Perhaps the Porsche 550/718 cars have the most body shell attach points, and those guys had a lot of tooling to insure that body sections fit the box chassis nicely!

Here is a 1950's car that has the tube chassis with only a few outriggers added to support an envelope body.

335S front 3-4 skin off _chassis c.jpg
Making the upper body skins to break at the equator works very well, and they weld up when the body is set on the chassis. The body skins are flexible enough to spring away when released, and then lift back off the chassis. (Horiz. equator weld visible ahead of taillamp socket ...)
335S rear skin off_chassis c.jpg

335S front skin over chassis c.jpg
You can add whatever temporary outriggers you need to set up your lower sections, and then doing the 3 units will go very simply, smoothly - and repeatably.

335S chassis gray _ skins done.jpg
Here is the image of the chassis all done and in gray, with the finished skins behind. (on and off 27 times, counted by the hash marks on the wall) Assembling skins into finished sections this way is routine - for teams making only 3-plus cars to race with. It's a minimal-thinking exercise.


ps, the sliding frame contour gauge you are using is aka "styling bridge" in the old school Fisher Body world ...
- end of diatribe -
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Last edited by crystallographic; 04-03-2020 at 03:05 PM.
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