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  #11  
Old 01-09-2015, 03:59 PM
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Z5Roadster Z5Roadster is offline
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Good result, nice to see one finished.

Well done.
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  #12  
Old 01-09-2015, 05:57 PM
SATAUS SATAUS is offline
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Default a question about universal copier

Hi Cobus,

First of all fantastic job of the buck, as someone said
it is a work of art.
Can you please tell me when you have all the steel pointers
resting aganst the car body where do you take the measurements
from on the copier so you can plot the points/measurements.
e.g. from the back of the steel rod to the wood guide?
knowing how long the rods are from point to back face of rods
you could work out where the point is.
Have I got this correct or am I completely off track?
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  #13  
Old 01-10-2015, 12:24 AM
Kabous Kabous is offline
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Hi Scott

As there are some critical steps when measuring for the buck, I will attempt to answer you first and follow up with the rest. Might look complicated but is quite easy, really.

The measurements were taken from the tip of the steel rod where it pressed against the body to where it enters the first wooden post – the second post is only to make sure the rods are perfectly level and lined.

Rail bottom.jpg

Normally it is best to keep things as simple as possible and that is why I used the inner post to measure against as this was both the baseline from the rear of the car to the front (A) and the baseline (B) for any measurements taken vertically of the horizontal wooden arm

Once you have all the measurements, Excel is your friend because you need to subtract and add quite a bit. Before we go into that, first something about the setup because that is very important.

I used two rails for the same reason there are two wooden posts - to make sure the ‘railcar’ runs true and keep the measurements honest

The position of the rails must run exactly parallel from the middle of the car lengthwise and don’t assume the middle of the GT stripes are it. Use a straight edge over the width of the body (level it) and use a builders square or other device and place it at the outside of the rear wheel wells (just touching it) exactly above the middle of the hubs. Measure and middle the straight edge and thus the car. Do the same with the front (do whatever you must but make sure the car is level too).

Position the rails so that the inner post will miss the rear wheel well by say 1/2 inch. The front wheel well will (if rails are placed exactly parallel to the middle of the car) be missed by much more. You can check if it is parallel if the rod (last one on the horizontal wooden arm positioned over the middle of the car) is lowered and land on both the marks you made (rear & front) with the straight edge.

Now you have squared the rails with the car. From that baseline you must put rails in the front and rear of the car at 90 degrees. You have to be creative to measure all the nooks and crannies when doing the front of the car. Very important here is that you mark the car somewhere in the middle of the hood (and boot) when you do your measurements during the length of the car because you need to establish an orientation point to make sense of the measurements taken from the front and rear. By that I mean the distance from the orientation point to the first post when the railcar is positioned in the front or rear of the car.
Another way is to make sure that your baseline (A) when measuring the front or rear is marked off on the long lengthwise rail so that can be used to make sense of the data taken.

Establishing the middle of the car is very important because once you have worked out all the data and transfer it to the whiteboard, the middle of the board then becomes the baseline because there is no other straight line to work from. So when you measure the top areas (boot & hood) make sure you know exactly the measurements from the middle of the car to the (B) baseline.

Baseline (A) would be on the same level as the lowest part of the body of the car that has a straight line (the zero on the first post wasn’t used – the exhaust was in the way but measured from the ground it was exactly the same height. The zero rod length was determined by using a plumb-line from the body to mark the ground and measure it back to the baseline (A).

Don’t use the absolute lowest point (back of rear fender) as this is a once-off point that doesn’t offer anything else. It will have a negative value as it is lower than zero.

Ok so back to making sense of all the measurements taken .

Let’s use the lowest rod in the pic and say for arguments sake its was exactly 6 inches from the tip to the inner post (C)
It was 2 inches from zero (vertical (D)).
The height of the inner post from baseline A to where it meets the horizontal measuring arm is say 30 inches - basically baseline B (E).
From baseline B to middle of the car (last vertical rod) is 32 inches (F)
And lastly, the rod measurement, from the underside of the horizontal wooden arm , 1 foot to the top of middle of the car (G)

On the whiteboard it will look like this:
The line in the middle of the board (top to bottom) determines the height of the middle of the body so because baseline A was the lowest point (zero) on the body, plotting the highest (H) will be like this: H= E-G (30-12) = 18
If your board was marked in inches, count to the 18th inch line from the bottom and mark it.

To plot the side of the car(I): I = F-C (32- 6) = 26
Because I was measured 2 inches from baseline A, on the hardboard go to the second inch line from the bottom, measured 26 inches from the middle and mark the sport.

Do this for all the measurements and duplicate for the other side. Now you have your outline and use a flexible ruler to connect the dots so that the curves are not broken/sharp somewhere.
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Last edited by Kabous; 01-11-2015 at 02:37 PM.
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  #14  
Old 01-10-2015, 02:06 AM
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Z5Roadster Z5Roadster is offline
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Oh so many memories being brought back.
When working on mine I established that absolute zero in the industry was approx. the centre of the gear knob, this is usefull if something moves or you lose your way. When you get to the finish stage lay a straight edge flat side down and press the ends down over the curvature, this will help fine tune the profile and eliminate errors but make sure you check both directions before adding or removing material.
Got to say it's a hell of a lot of work, but you got a result. Still think scanning and digitizing is the way forward.
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  #15  
Old 01-10-2015, 09:55 AM
Kabous Kabous is offline
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Scott - the way you want to measure it - from the rear would give very accurate readings. The only caveat being all the rods must be exactly the same length.

Quote:
Originally Posted by Z5Roadster View Post
Got to say it's a hell of a lot of work, but you got a result. Still think scanning and digitizing is the way forward.
Yes on both accounts. Tried to get someone to scan but that kind of facility is hens teeth over here (and pricey). I have digitized the buck but it being a first effort, did not want to CNC the ribs. Next time around would sure go that route.

Hopefully the hard work done so far would pay off if I can make bodies for others as well somewhere in the future.
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Last edited by Kabous; 01-10-2015 at 09:57 AM.
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  #16  
Old 01-10-2015, 08:07 PM
SATAUS SATAUS is offline
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Hi Cobus,
Thanks you for taking the time to write up such a long explanation.
I had to read it a few times but I got my head around it.
Can you take some more clearer photos of the carriage please eg underneath
where it looks like you have bearings to run on the rail and what bar did you
use for the rails?
Once again thanks for the explanation it is much appreciated.
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  #17  
Old 01-10-2015, 08:33 PM
Oldnek Oldnek is offline
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WOW! Work of art..
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  #18  
Old 01-10-2015, 09:15 PM
fred26t fred26t is offline
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Default Very Nice

One item that might be helpful it to build out the wheel wells and grill opening. Then you can use that part as a hammerform. Fred26t
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  #19  
Old 01-10-2015, 09:25 PM
Kabous Kabous is offline
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Hi Scott

That pic is the only one I have at the moment. I am offshore and will only be able to take some more in about 3 weeks time- if I still have the railcar.

You can place small bearings on the outside and top of the rectangular tubing (100mm x 50mm) ( but not inside) on the front and rear of the railcar (8X bearings). If you can make it adjustable so much the better because if it runs too tight (inside bearings will tend to cause this) the car wants to climb out of the rails and if loose and you will compromise precision.

One thing I would add next time is to have a sliding mechanism that runs on the side of the first post (or posts for accuracy) vertically so measurements can be taken wherever you want as opposed to every 50mm. This will help you track the outside of the wheel well much better and places like the air vent behind the front wheel well. Will be especially useful when doing complicated areas such as the radiator/oil cooler/quicklift.
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Last edited by Kabous; 01-10-2015 at 09:27 PM.
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  #20  
Old 01-31-2015, 06:26 PM
Meeksie Meeksie is offline
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Quote:
Originally Posted by Kabous View Post
Scott - the way you want to measure it - from the rear would give very accurate readings. The only caveat being all the rods must be exactly the same length.



Yes on both accounts. Tried to get someone to scan but that kind of facility is hens teeth over here (and pricey). I have digitized the buck but it being a first effort, did not want to CNC the ribs. Next time around would sure go that route.

Hopefully the hard work done so far would pay off if I can make bodies for others as well somewhere in the future.
You can buy a structure sensor which adapts to your Ipad for less than $400 made by a Kickstart company Occipital. It sure takes a lot less than a full night to scan a whole car and goodness knows how long to punch in all the coordinates. I have not seen what measurement accuracy the sensor is capable of but it is certainly worth investigating for your future 3d measurement needs.
http://www.structure.io/
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