Car Body Buck

I couldn’t decide which method to use for constructing the 3D full sized car body buck. The options were endless….

In the end, nasty horrible MDF won. I cracked out the goggles and the dust mask.

I now remember why I never did wood work at school; not that MDF is wood. MDF is a nasty carcinogenic dust ball masquerading as a wood like substance.

The real conundrum I had, was whether to build a buck out of wire, polystyrene, clay or wood. One professional would use one style, whilst another a different one. Having never built a car from scratch, I had no idea of the advantages and dis-advantages of each, apart from:

  • Steel bar tends to bend in nice smooth arcs.
  • Wooden frames have a much more solid appearance and are easier to visualise.
  • Wood burns when welded against.
  • Burning MDF could seriously affect your health
  • Metal frames flex and can be more easily adjusted
  • Body Filler can be applied to in-filled bucks
  • You can weld steel panels over open frames
  • You can clamp part formed panels over open wire-frames
  • Open bucks allow access to both sides of a panel with dolly’s and hammers

Traditional Car Body Bucks

If you look back in time, to when cars were prototyped by small teams of highly skilled craftmen, with access only to traditional tools and no CNC, models were fashioned either from clay or wood. Some of the best looking cars of all time, such as the Jaguar E type & Porsche Speedster, used these methods. As any young child will inform you, clay is easy to model with, but maybe the use of wood has roots partly in tradition. Many vintage cars have timber frames and floors with interiors garnished by hand crafted mahogany. Factory workers would return home to houses filled with polished & in-layed furniture, hand-hewn by the same master tradesmen that sold their wears in every high street. If you wanted a rugged and accurate buck it was the cabinet-makers that got the job.

Wooden bucks still hold their own, but with the use of 3D CAD and modern materials, other methods are now in the running. Many of these methods do not require the level of skill needed for a traditionally crafted wooden frame, or do they require massive tool boxes and wallets. Thats not to say anybody could craft a new car, as I think you agree, even major car manufacturers can get it very wrong, but these new methods do prove a decent proportion of those with a strong will and good patience can produce surprising results.

Metal Frame Car body Buck:

Car Body Buck

Wire Frame Car Body Buck:

Car Body Buck

Cardboard & Polystyrene Car body Buck:

Bailey Blade Car Body Buck

Open wooden Car Body Buck:

Alfa Romeo Sprint Car Body Buck

Semi-Closed wooden Frame Car body buck:

Porsche Speedster Car Body Buck

Clay Car Body Buck:

Clay Car Body Buck

I could see advantages in each and indeed dis-advantages, but which ones are key to me? I spent weeks swinging wildly between methods. I’ve even got quotes on material costs. In the end, it was a video with Ron Covell that swung me. He was building a rear tub for a Model T Ford Hot Rod. It was made mainly from MDF (see here). There were 2 suppliers of MDF within a mile and they both open 7 days early ’til late and even on Sundays.
– I agree, It’s not a scientific way of deciding modelling methods.

With some of the open wire frame cars, unless they are replicas of production models, I have a bit of difficulty in imagining the gaps in-between the bars. Polystyrene / Cardboard models are easier to envisage, but I think these are better suited to fibreglass cars and as I drop stuff all the time, I would be afraid of damaging it. By the time I finished a polystyrene model, it would already look like it had been through the crusher.

CAD Car Body Buck

I used the wire frame from my CAD model to generate a cutting list for the MDF.

To get the shape of some of the infill pieces I used bent welding rod and even the wire from the MIG welder to trace the curves. The welding rod worked quite well, but once you’ve used it once, you have to through it away. However, the thin (0.8mm) welding wire turned out to be really good, as it returned to a large coil shape after every use. I put a piece of duct tape on each end and drew a line along the natural arc that was formed. You could argue, that I used a combination of the wire frame method and the wood method. Ron Covell also suggest masking tape, this might be better for longer arcs, but for now, I’ll stick to my wire.

MDF Car Body Buck

Wooden Hot Rod Buck

One problem I had, was not the plotting of the shape or cutting the MDF; as this turned out to be very easy. The problem was the MDF itself, as it is horrid to work with. The dust can give you cancer and a ton of it is generated. Everything in the garage is covered in seconds. My goggles, being plastic, were static and  fogged over 1/4″ thick. The valve on my mask blocked and the vacuum cleaner attached to the back of my jigsaw also clogged up long before it was anywhere near full. Any exposed skin just itches for hours, so full overals, in a garage approaching 35°C, are needed. Unlike other dust; car body filler for instance; it stays in the air for hours before settling. Maybe I am starting to understand why people prefer wire-frames.

I have an ancient A1 sized plotter that I was going to use to plot out my CAD drawings, but when I doubled checked the printed paper output, the length-wise dimensions were way out. The wing for instance printed over 30mm too short. I tried adjusting scales but this was time consuming, so in the end I simply used a good old fashion set square and pen. Each panel for the wing has 26 plotted points on it. MIG welding wire proved perfect for a guide whilst joining the dots and actually produced a very smooth and controllable arc.

I cut the panels fractionally oversized with an electric hand JigSaw equpped with fume extraction. Although this produced reasonable smooth arcs, I still found the cut board a little hexangonal to the touch. Ron uses a massive, 3 foot wide, disc sander to smooth his, but my little 6″ model made things worse, so I just used a hand rasp. The main arcs are 18mm thick MDF but the smaller in-fill panels are mostly 22mm thick. The thicker material allows for heavier sanding with the flap sander equipped 4.5″ angle grinder. I have glued and clamped up several pieces of MDF in advanced, just in case I need a piece double thick. Wood glue takes a long time to dry properly, so a bit of forward planning might pay off.

One of the biggest reasons I went for MDF / wood was because I wasn’t 100% convinced that my CAD model would actually look OK once scaled up into a real, full scale, 3 Dimensional car.

Wooden Car Buck

Whilst constructing the buck, I found a bottle of really old wood glue that had separated into runny water and a solid mass. The residue or watery resin, was perfect for tipping over the buck to keep the dust down. It bonded the top surface back down hard during and after shaping. There is probably something out there on the market especially for the job, but this glue was heading for the bin, so I used it. I need to find something similar, as my old glue pot is now empty and I still have the rest of the car to start.

Mirror image

Whenever I cut a piece, I cut a mirror item for the other side. So next weekend, if I’m not up to my knees in stuff from an auto-jumble, I’ll be finishing the sanding on this side and then starting the other. So far, I’ve basically constructed up to a small ridge line that runs the length of the wing, crudely shaped the MDF with a flap sander and given it a quick rub. Once each panel is finished, I will locate it onto the base board with dowell pins. These pins will keep the panel in the correct position but allow it to be removed and later returned to exactly the same spot.

Not all of the car, will be solidly in-filled (probably). Just the bits I recon are going to be tricky to get shaped right (visually). The front wings are going to be the trickiest, therefore they are going to be in-filled and sanded.
Who knows… I may even make an open buck as well. Only experience will answer this.

The doors and side panels will be left open framed. Although the swage line does bother me. I might need to see the shape solidly represented in wood.

37 Ford Car Body Buck

In case you are wondering what my car will look like, I took inspiration from an American Hot Rod called ‘Dreamsicle’. This Hot Rod is a custom body inspired by a 1937 Ford ‘Slant Back’ 2 door sedan. My version is therefore going to be a miniature, inspired by a Hot Rod, inspired by the real thing. Evolution right?
1937 Ford Dreamsicle

An original 1937 Ford Slant Back 2 Door Sedan :
Ford 1937 Slant Back 2 Door Sedan

In case you are wondering, Yes I am dropping all this over my Locost chassis. My body will be heavily sectioned, channelled and chopped, but you get the idea.
I’m using 2001 Mini ‘One’ Headlamp units, an MG Midget screen and my 4″ stretched wheelbase as my dimensional starting points.
Super 37 Overlay
Once the wooden car body buck is complete, I will have something that I can use to shape the final metal body. Although some areas of the buck can be used for hammering against, e.g. flanges and panel returns, in general the buck is simply there to have a full size 3D model of something I can offer panels up to: for size and shape etc. The edges of MDF board aren’t great for hammering against, as it will just feather out. Maybe if I double up the edges, or soak it in resin, it will toughen up. – I wait to see.

English Wheel

The English wheel is coming along well in the back-ground. I’ve almost completed the CAD for the new taller frame, top and bottom anvils are sitting waiting on the side. Plus, I’m collecting up all the tools needed for fashioning the steel body. All I need to do now is learn how the panel beat….How hard can it be? Hhhhmmmm

I also have a gantry and surface table to finish. I’ve ordered a dozen 40mW XY cross-hair lasers from China. These will be mounted on a travelling gantry that will encompass the body buck. The gantry and table runners will have long steel rules attached. I should be able to place a pair of laser cross-hairs of onto both sides of the car simultaneous in exactly mirrored positions. The cross-hairs should extend vertically and horizontally along the car high-lighting any differences between each side of the car. I’ve seen numerous different approaches, but if you’re struggling to picture what I mean watch this link. In the olden days, the lasers would have been replaced by a man doing thousands of measurements with a height and depth gauge. When a laser line is shone at a surface, any in-perfections are easy to see and problems seem magnified. A tiny error in the X direction can result in massive errors in the Y or Z directions. A perfectly straight line can appear twisted into an ‘S’ when viewed head on.
Body Buck Gantry

I’ve started with the front wings, but ideally I need to have a central feature to use as a datum. The bulkhead is a favourite starting point, so as my MDF stock is now run-out and I have to buy some full sheets, this is where I start next.

Anyway, enough blogging, I better start clearing up that awful dust – ready for round 2…….

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