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  #21  
Old 04-03-2010, 04:00 PM
David Gardiner David Gardiner is offline
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When using a measuring bridge you work from a center line..........
Mark the center line on each board and then the profile is marked on each half of the board giving a full buck. its cheaper and easier to build a half buck especially for a one off. Still a hell of a lot of work and money.

David
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  #22  
Old 04-03-2010, 07:43 PM
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I would think using a full side to side you could get locked in, depending on the contour . Using side to center you could lift, move, jiggle,wiggle what ever to get off the contour without moving any pins to kep the profile.
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  #23  
Old 04-03-2010, 08:55 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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Quote:
Originally Posted by Z5Roadster View Post
...I like your input, I only wish I had the time to go thru all the various threads to increase my understanding of the different ways you guys do the same job....
Tom, if I can give you one bit of advice learned from the school of hard knocks on my roadster. I was in a hurry to get to the metalshaping and shortcut the design and buck process. As a result I've spent considerably more time, money, and effort than if I had studied, engineered, designed, before I put hand to metal.

Your mileage may vary but that was my experience and I'm still dealing with the results of those early bad decisions.
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  #24  
Old 04-04-2010, 03:06 AM
Einar_S Einar_S is offline
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For direct transfer to a the material making a buck RodDoc's way is very simple and would do a good job. I haven't done it, but it seems quite obvious from the (as usual) excellent drawings.

I would however like to keep the "raw data", in other words the position of each pin. Thus it can be recreated anywhere at any time. And it can be imported into a CAD program or even better, a more artistically inclined drawing program.

How? Using the frame shown, but with linear scales. At least 2 of these will be needed, one on the vertical frame arm and one on the horizontal. Adding a scale on the longitudinal axis of the car would make it complete. Although this could easily be done using a ruler and manual entry. I know, it's quite close to the laser measuring method suggested before. But I tried to price a laser similar to the Leica Disto with data output capability, but the price was ruling this out, at least for me.

I already have the scales and the companion card to convert their output signal into 1/100mm increments in the PC. But building the frame with bearings for the scales to move along the frame would add up to my already too long project list.

The scales can usually be found on Ebay, coming off digital readouts for lathes or mills.

This might be a viable project for several participants getting together. You will very seldom be using such a contraption. I would engage if that could be arranged over here. And I would also go into more detail on the electronics if someone else wants to do it.
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  #25  
Old 04-05-2010, 06:46 AM
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Quote:
Originally Posted by David Gardiner View Post
Still a hell of a lot of work and money.

David
David thats very true but we all have to decide how we each spend our hard earned spare cash. I think it is also a factor why we want to do these things, financial gain, a living, because we have time or just because we can. Why I started this thread we because I felt it was too large a project to undertake without the guidance and advice of others that have gone before. The help that is coming in is fantastic. please keep it coming.

Quote:
Originally Posted by HEATNBEAT View Post
I would think using a full side to side you could get locked in, depending on the contour . Using side to center you could lift, move, jiggle,wiggle what ever to get off the contour without moving any pins to kep the profile.
I am thinking that because the Buck slots together we would be able to remove say 1 side to work on the other once the body build-up grows, I don't think we would ever get to the stage where the Buck would be totally enclosed by the shell.

Quote:
Originally Posted by Kerry Pinkerton View Post
Tom, if I can give you one bit of advice learned from the school of hard knocks on my roadster.

Your mileage may vary but that was my experience and I'm still dealing with the results of those early bad decisions.
Kerry we may well be likeminded.

The short course is not always the quickest, and the begining will be at a different point for each of us.

If I form 2 pieces of ally how do I scribe them together without having some sort of model to place them against, 'sometimes eyes tell lies' I know mine do.

Quote:
Originally Posted by Einar_S View Post

I would however like to keep the "raw data", in other words the position of each pin. Thus it can be recreated anywhere at any time. And it can be imported into a CAD program or even better, a more artistically inclined drawing program.

How? Using the frame shown, but with linear scales. At least 2 of these will be needed, one on the vertical frame arm and one on the horizontal. Adding a scale on the longitudinal axis of the car would make it complete. Although this could easily be done using a ruler and manual entry. I know, it's quite close to the laser measuring method suggested before. But I tried to price a laser similar to the Leica Disto with data output capability, but the price was ruling this out, at least for me.

.
Spent a long time looking into this method, goes back some 35yrs when working for a company making crank shaft turning lathes. Large co-ordinate measuring machines. Which then took me onto laser equipment.
A couple of the links I followed:-
http://www.3dengineers.co.uk/index.html

http://metrology.leica-geosystems.co...-Scan_1836.htm

Both very good at what the do, but I think you would need a customer like David Kirkham had to build the all ally Cob. Very deep pockets.

My personal problem with cad data is that once I have it I cant use the programmes to get the best from it. Also unless you have a cam system to send the data to, you still end up with a pencil and tape measure.

Many thanks for all the input.
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  #26  
Old 04-05-2010, 07:59 AM
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Default pantograph

Anyone tried a 1 to 1 ratio pantograph? Run the styus across the body line in a fixed plane and have it draw a line on paper,metal,or plywood.
Also, I have had in mind the old mechanical drawing tables where the t-square stayed parallel by using a string/cable and pulley system. Several thoughts have come to mind in this regard. (1) I have a very large digitizing tablet that I have had for more years than I care to admit that I have considered using for making body contour templates. It is probably at least 4x6 feet.
(2)along the lines of the t-square cable system, one could wrap that cable a couple of turns around the shaft of an encoder that would put out digital position information that could be useful.
(3)last night I was laying in the rack trying to get to sleep and was pondering the use of a touch screen to transfer part contours to digital coordinate vectors. I have a 19" touch screen that i just bought for my CNC setup. That is wonderful to use. To be able to just touch the screen to make selections instead of moving the cursor with mouse or ,in my case, a trackball. I need to install my cad/cam program to that computer and give it a try in sketch mode.
Touch screen overlays can be had for less than a C-note on ebay. Mine is a 19' NEC lcd monitor with touchscreen. I sniped it for $66 on ebay. I like it. I like it a lot! I find myself touching the screen on the computers in the house. I might have to try screen kits on those.
Anyway there's a couple more options to ponder.

Last edited by mr.c; 04-05-2010 at 08:07 AM.
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  #27  
Old 04-05-2010, 08:07 AM
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A few years ago I ran across a freeware program that was a "Ray Tracing" modeling program. It involved running a string line from the center of an "object" and taking photos (as many as needed to capture all details of the object) then load the photos into the program and it would creat a 3D mesh of the "object" that was converted into cad/cam. If i remember correctly they used the program to make foam "molds" for the reproduction of a 40 Willies coupe. I'll try to find it again. Not all Ray Tracing programs will export to cad/cam. It may not be as accurate as laser measurements but could be a good low budget alternative.
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  #28  
Old 04-05-2010, 08:09 AM
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Kerry Pinkerton Kerry Pinkerton is offline
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Quote:
Originally Posted by mr.c View Post
....I have a very large digitizing tablet that I have had for more years than I care to admit that I have considered using for making body contour templates. It is probably at least 4x6 feet.
....
Carey, are you thinking you could use a panograph mounted on a bridge (scaled down to 1:2 perhaps so you could do a larger panel), to capture the data digitally using a pen from the panograph on the digitizing tablet and the other end against the car?

Wow, that is an INTERESTING idea. Hummmmmmmmmm

The reason I'm so interested in making a copy buck is that if I ever finish the roadster, I'd like to make a coupe version of it....
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  #29  
Old 04-05-2010, 08:36 AM
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Kerry: That has been my plan for many years. It is just a ways down on my unending project list.
The pulley encoder setup may be a good avenue to explore. There is some affordable software that could make all of this doable. I just changed over my controller software to Mach3 and am liking it a lot. It has a probing system for digitizing parts which can then be cut on a variety of equipment. Fun stuff. I have been using a cnc lathe to make parts for years and I am still amazed at the technology. My TuckPucks are all within very close tolerances even with UHMW poly. They don't even remotely need to be close tolerance but that is what the machine cuts. I love it. What a generation that I have lived in. It is amazing how technology has advanced in these few(6+) decades. I remember when I bought my first electronic calculator. It was $85 back when that was a huge amount of money. Then along came the computer. I remember when a 30 meg hard drive was huge. 30 meg won't do anything these days. Shoot! I got lost on memory lane. Sorry. Carey
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  #30  
Old 04-05-2010, 10:40 PM
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Default photo modeler

this is the type of program I was talking about. this is not the freeware ( I'm still looking) but you can see what this type of program can do. take a look at the Plant and Engineering tour http://www.photomodeler.com/producttour.htm#
I'll keep looking for the freeware
downloaded the trial program, there is a Ferrari in the tutorial, should be interesting to see how long it takes to render and export to cad (DXF). Once I learn the program a little better I'll try some of my own photos. looks to me like it's going to be a good bit of work to get an accurate digital reproduction this way. But then I've never tried any of the other ways either.
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Last edited by 87hdrush; 04-06-2010 at 12:36 AM. Reason: update
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