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types of chassis (back half)

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sawdawg:
It looks to me that there are two basic types of chassis construction for the back half of a fed.
1. The shoulder tube forms a hoop (u shape) and the lower tube forms a similar hoop (u shape) see page 9, example 2 of SFI specification 2.4c
2. The shoulder tube forms a hoop (u shape) and the lower rail bends up to meet the shoulder hoop at the drivers back. see page 9 example 1 of SFI specification 2.4c

Is there an advantage or disadvantage to either type?
Is one easier to assemble than the other?
Does one take more material than the other?
Is one stronger than the other?

nostalgic371:
Great question! I built my car with the upper and lower hoop, and I've wondered the same thing. I can tell one thing, getting the seat just right for the intended driver was the most difficult part of the build for me, maybe the two styles have an effect on that. Hopefully someone with experience in both will comment here.

rooman:
All Don Long and most Frank Huzar (RCS) and Roy Fjasted (SPE) cars had the upper and lower loops while Woody Gilmore favored having the lower rails roll up to the shoulder hoop. Back in the day the former may have been a little lighter but with current rules regarding the positioning of tubing to shield the seat from impact both versions weigh about the same. I like the Woody style and build my cars that way even though it involves a bit more work in the area of compound bends and notch alignment. For a first time builder the double loop version is probably simpler.

Roo

sawdawg:
I am a first time builder at least for a dragster. I've built many street rod frames and a Bonneville Lakester using dom tubing. But that tubing was quite a bit thicker .125 thick, and a lot of it. That lakester car is 23 feet long and weighs 2,300 pounds. Currently I drive a door slammer in 1/8 mile bracket racing but need more excitement. I'm quitting Bonneville after this year and will try putting it's engine in a fed this winter. The motor is a Chev LS3 all aluminum engine. I haven't seen any LS engines in fed's, is that because you can't nostalgia race?

rooman:

--- Quote from: sawdawg on June 04, 2018, 08:25:52 AM ---I am a first time builder at least for a dragster. I've built many street rod frames and a Bonneville Lakester using dom tubing. But that tubing was quite a bit thicker .125 thick, and a lot of it. That lakester car is 23 feet long and weighs 2,300 pounds. Currently I drive a door slammer in 1/8 mile bracket racing but need more excitement. I'm quitting Bonneville after this year and will try putting it's engine in a fed this winter. The motor is a Chev LS3 all aluminum engine. I haven't seen any LS engines in fed's, is that because you can't nostalgia race?

--- End quote ---

That may be part of it but I think that the main reason is that most of the racers involved in the nostalgia scene are simply old school and prefer racing against similar cars. There is no rule that says that you can't run an LS and there are plenty of manufacturers making parts to run them with distributors and carburettors so that they look "correct". It does not take much in the way of an LS to go fast. The motorsports program at IUPUI (a joint Indiana/Purdue University college here in Indy) has a Spitzer S/C dragster with a GM supplied LS7 Corvette motor. It is stock apart from a nice set of headers and a conversion to cable throttle (from drive by wire) and with the throttle stop disconnected it runs mid 8's.

Roo

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