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New fed chassis tubing question!

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Jmed795:
Hello all,
Ok so new fed chassis planning in progress, it will be 200" it's based off of mark Williams and Dave Tuttle designs. I am building it to 2.2c for future. Question is on my lower hoop and lower frame rail can I use 1 1/4 .058 from back to front. I know a lot of chassis mark Williams in particular uses 1 3/8 then transitions to 1 1/4 in the engine bay. My shoulder hoop and top frame rail go from 1 1/2 to 1 3/8 in the engine bay to 1 1/4 up front with telescoping joints at the transitions. I am trying to avoid buying new dies for two bends and I like the idea of all the same tubing on the lower rail. So any help would be greatly appreciated.

Thanks
Justin

Jmed795:
or my other idea was just doing the whole lower hoop and rails in 1 1/2. ideas anyone?

dreracecar:
call me 1 310 768 3163
 info takes too long to type

rooman:
Simple answer is that if you use the MW design with the lower rails forming a hoop (joined in the center at the rear upright) you can use 1 1/4" but if you use the Tuttle design (lower rails transitioning into the rear uprights) the rear portion of the frame (from 2" forward of the rear end uprights) to the shoulder hoop must be 1 3/8".
  It is on page 4 of the 2.2C spec, do yourself a favor and spend the $38.
 IMHO using 1 1/2" for the entire lower rail would make the car look clunky and also would tend to make the car a little too rigid --if you want to do that why not step it down like the upper rails--1 1/2 to the rear end uprights, 1 3/8 to the motor and 1 1/4 from there out.

Roo

nostalgic371:
I built my car using a Tuttle plan and the SFI book, and it worked out well for me, the plan gave me working dimensions for a "average" size driver and the SFI book let me know how much I could deviate from the plan if I felt the need too. Also I was confident there would be no problem when it came time to tag the chassis. Getting the relationship of the seat to the rear end housing as ideal as possible to make the car comfortable seemed to be the biggest challenge, the rest was easy. Use an alignment bar, and do one final alignment after the chassis is completely welded and then last drill and ream the rear end mounting holes out to the bolt shank size.  I also tapered the rear end mount plates in at the bottom 1/8 per side to make sure the housing will still go in and come back out, as things may move around a bit during the final weld up.

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