FrontEngineDragsters.Org Forum
Technical => Roo Man's Room => Topic started by: HOTRODFL on August 20, 2014, 09:34:13 AM
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Roo, slip joint in top tube just in front of motor plate where tubing steps down 1 size, should the angle be on top and angled forward as I was getting ready to do or under and back. Two local chassis builders both go with the under/back method ?.
One more question, 4 tubes going to the front, which set of tubes U/L would you keep whole and which set would you cope to blend to front end assy. Thanks...
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I really don't think that it matters as the main reason for the angle cut is to spread the junction along the length of the tubing. Don Long's in cockpit splice has the angle raked forward from the top and he is way smarter than me so that is how I do mine.
On the second question I presume that you are talking about a torsion bar style frame where the top and lower rails are run straight to the junction and in that case I cope the lower rails. Make sure that you make the overall height of the two tubes taller than the cross member so that they wrap around it. Two reasons for this, first you end up with the torsion bar/cross member being tied into more of the frame rails and second, wrapping the weld further around the cross tube reduces the tendency for it to bow when welded. In the same vein, a tight fit is mandatory for the same reason.
Roo
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Top foward-bottom trim back
I prefer to do the trim on the bottom, reason being that I can easily remove the top tube and trim the bottom in place and then drop the top tube on for fit, repeat as many times to get it fit proper.
Also at the point of where the front torsion attaches to the frame, that the frame ends are at least 3/8" above and below the dia of the torsion tube. That way you will get enough wrap around the TT and the fit and welding of the framerails at the taper isnt too long.
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Both students of Long.
As Don would explain "A runners body is slanted foward, just looks fast"
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Guys, thanks for the input....
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"where the front torsion attaches to the frame, that the frame ends are at least 3/8" above and below the dia of the torsion tube. That way you will get enough wrap around the TT and the fit and welding of the framerails at the taper isnt too long."
So Bruce, do you "heat-and-beat" the 3/8" overhang / underhang at the ends of the frame rails and then weld around the ends? I could see this approach substantially reducing, if not almost eliminating, the coping and weld length of the junction of the upper and lower frame rails, depending on the relative diameters of the torsion tube and the frame rails.
Any pics?
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Does not take that much heat to tap the .058 material. I should explain further that the end of the framerail is just a little past centerline of the TT
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Yes, I wouldn't think the frame rails would wrap all or most of the way around the TT.
Thanks for your reply, I find yours and others willingness to share your expertise and experience most interesting and informative.
Thanks again,
John
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Here it what it looks like in the process. This one as seen in the photo has a little more tubing overhang than normal as it is a "save" of a Cen-Pen car. I wanted to eliminate Worm's clumky deal with the tubes simply stacked and plated over so I coped the lower rail and laid the top one into it. With the rails being .095 wall it was going to take some work to put the notch in for the torsion bar so I left them a little long and used a hole saw, using Worm's side doubler as a guide by hose clamping it to the side of the frame--you can see it laying on the jig cross member. Normally with .058 tubing you can do the notch with a drum sander. The next step is to cut off the excess frame tubing and wrap the rest around the torsion bar tube. And you are correct John, it makes the cope (and subsequent weld) quite a bit shorter.
(http://i156.photobucket.com/albums/t18/aussierooman/9805892b-089b-4427-8dc5-28ea4d2f3f0a.jpg)
Roo
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Looking at Roo's pic you will notice the lenght of the cope, If one were to cope it more so there is no wrap it would add another 8" to the weld joint. You also dont have to do a full wrap around the TT. 1/4" past the top tube upper centerline is plenty.
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On a finished chassis you have fewer options, but if your building, you can cope the lower tube to the torsion tube, and put a slight bend in the uppers and have them cope to the torsion tube just above the lower tube/ torsion tube intersection. Front frame segment is a little taller, but makes a far forward weight box/ fuel cell, blend with the chassis lines really nice.