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Bottom rail measurements needed  Rating:  Rating
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 Posted: 12-06-2007 03:31 am
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Art DeKneef
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Location: Mesa, Arizona USA
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For another JH I had (74 #17500) I built a rolling frame out of steel I had so I could move the body around while I worked on it. There were four uprights (one for each corner) that were located at the front and rear positions of the two rails that run under the car. When I measured the old car's rails at the front I got an outside-outside measurement of 32" and an inside-side measurement of 28". The rear points were measured at 31 3/4 outside-outside. Pretty close.

The car I am working on now (74 #19658) is fully stripped down and I am checking out the damage the car has to fix it. While on the rotissiere I measure the rails and the fronts are the same. The backs are not. The back measures 31" out-out and 27" in-in. In checking the body over I do not see anything that could account for the differnce. There is some small creasing near the passenger rear wheel well but that appears to be just at that area. I do not see any other signs to explain the difference. Except if I write it off to the fact that these cars were hand built. But since they were built on a frame to keep things in the right place (hopefully) I'm wondering if this is something to worry about.

Does anyone have any info on this or could measure their cars and let me know the measurements.

I'm also posting this to the Jensen mail list.

Thanks

Art

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 Posted: 12-06-2007 03:10 pm
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Judson Manning
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Art,

Section 'K' in my shop manual has a drawing of the monocoque dimensions entitled "chassis alignment check".  I'm assuming this drawing was meant for body shops with fairly sophisticated measuring equiment.

There is a measurement of 827mm (32.6") for the out-to-out frame rail measurement at the front of the car (agrees with 17500). The drawing doesn't carry these dimensions past the rear suspension pick-up points.

My suggestion is to check the frame rail dimensions from front to back and see if that extra inch is a gradual thing or if it comes on suddenly.  A sudden departure from 32" would indicate where any damage may be located. 

Alternatively, 19658 is pretty late in the production cycle and the tooling may have gotten a bit out of tollerance.  At any rate the critical aspect really is the rigidity of the monocoque and not necessarily its dimensional accuracy.

Judson

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 Posted: 12-06-2007 03:40 pm
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Art DeKneef
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Thamks Judson.

I should have mention I looked at the body specs page. I saw the 827mm measurement at the front, but didn't follow the lines back. Plus I figured I would do the number conversion today. Or go look for a new tape measure that does metric.

The change is gradual. I put a straight edge against the rails and the gap is pretty consistent all the way down. The area around the tunnel is also straight and flat. I figured it was the result of a hand-built car but wanted to make sure.

I just need to redo my rolling frame some so the rails fit into the top holders. That looks like my project for this weekend.

Art

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