Author Topic: types of chassis (back half)  (Read 561 times)

Offline sawdawg

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types of chassis (back half)
« on: June 01, 2018, 08:12:39 PM »
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?

Offline nostalgic371

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Re: types of chassis (back half)
« Reply #1 on: June 01, 2018, 09:02:00 PM »
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.

Offline rooman

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Re: types of chassis (back half)
« Reply #2 on: June 04, 2018, 04:17:35 AM »
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
Yeah, I am from the south--any further south and I would have been a bloody penguin.

Offline sawdawg

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Re: types of chassis (back half)
« Reply #3 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?

Offline rooman

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Re: types of chassis (back half)
« Reply #4 on: June 05, 2018, 04:29:38 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?

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
Yeah, I am from the south--any further south and I would have been a bloody penguin.

Online wideopen231

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Re: types of chassis (back half)
« Reply #5 on: June 05, 2018, 05:56:17 AM »
 I agree thats its a old school thought thing. I do think that like any other form of drag racing it needs infusion of new blood to keep it going.  I think anything   that draws new folks in is good. Lets face it the crowd who love nostalgia racing because of the great times and memories is getting old and fewer too quickly. Racing as whole has challenge because American youth does not have the love affair with the automobile.  The one that do barely know what a V8 is other than a veggie drink.

 Check rule book and find cpl class' that you can build to run in with LS and go out and have a blast with a Newstalgia set up.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline Oldboy

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Re: types of chassis (back half)
« Reply #6 on: June 05, 2018, 07:38:10 AM »
Sawdawg, check this out...

Offline sawdawg

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Re: types of chassis (back half)
« Reply #7 on: June 05, 2018, 08:24:17 AM »
I like it, I like it, I LIKE IT1111111  My project for the winter is to either sell my Bonneville car without the engine or strip everything off it I can and build a fed for bracket racing. I'm in the research stage now. I need a project every winter that takes up 1,000 hours of my time and is a challenge. Last winter I made a mid engined 50 chev fastback.

Offline nostalgic371

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Re: types of chassis (back half)
« Reply #8 on: June 05, 2018, 05:35:13 PM »
I built the double hoop style for my first try, and as I look back now I felt it was more forgiving for getting the seat angle and shoulder hoop height set up and adjusted. I would look through all the chassis posts here, and let us know how it progresses!

Offline fuel749

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Re: types of chassis (back half)
« Reply #9 on: June 06, 2018, 05:28:30 AM »
I build all mine as the double hoop style unless specifically asked otherwise.  It's what I'm set up for and I always have pre bent upper and lower hoops on hand since I bend enough for 4 cars at a time. I've built them the other way but since I don't do it that way often I find it more time consuming. 

Online wideopen231

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Re: types of chassis (back half)
« Reply #10 on: June 06, 2018, 05:29:19 PM »
I built mine with the Woody Gilmore style. Had no issues with lower tubes,seat position or anything else.Well not related to the lower rails.LOL
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline sawdawg

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Re: types of chassis (back half)
« Reply #11 on: June 11, 2018, 08:28:57 AM »
That brings up another question, I have lot's of them,  what is the angle of the back tubes and how far behind the  axle center line is a good place to start for the rear upright tubes. I guess it depends on the drivers physical size but it seems it would be hard to try to get in and out of a car with just the tubes taped together to get an idea of where things should go. Or should I just get a kit with a blue print?

I tried to post a picture of my Bonneville car, don't know if I was successful or not. The car needs some explanation. How can a Bonneville Lakester only go 160 mph with an LS 3 engine (see my profile) The reason is that the LS3 is the new engine and I haven't run the car with it yet, maybe this year. I only participate in the Bonneville World Finals which takes place in late
September or early October. The August meet is too hot and crowded. The Finals event has been rained out for the past 5 years. The old engine was a Nissan V6 with 154 horse power so 160mph isn't too bad. But my goal was 200mph. I tripled the horsepower to get 40 more mph. No one ever said I was smart.