Author Topic: Jr dragster chassis  (Read 3306 times)

Offline samotorsport

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Jr dragster chassis
« on: December 09, 2022, 03:01:11 AM »
Hey guys , my name is Sam , i m 42 , from Luxembourg Europe .
I am currently building a new jr dragster chassis for my son.
We bought a car couple of years back and raced it for 2 years.
This year we decided to give it a major overhaul which ended on finding some bad mods covered under paint.
Therefore i decided to build a complete new car, CrMo instead of mild steel.
Here are the first pics .
Updates will follow .
But to start with , I also have a question.
Does the orientation on the tube joints matter ?
I mean from the cell to the front half . The 45 degrees , beeing the long part on top or bottom.
Thanks in advance
Greets
Sam

Offline samotorsport

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Re: Jr dragster chassis
« Reply #1 on: December 09, 2022, 04:37:05 AM »
First pictures of the build

Offline slingshot383

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Re: Jr dragster chassis
« Reply #2 on: December 14, 2022, 03:11:19 PM »
Long end of the 45 on bottom when sliding smaller tube into larger tube. When doing diagonals, use a 1/4" shim to keep them off the main rails and just on the uprights (also to get a full 360* weld on the tube.
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Offline samotorsport

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Re: Jr dragster chassis
« Reply #3 on: December 15, 2022, 01:32:32 AM »
Thanks a lot , I plan on doing the diagonals this afternoon . So just in time ;) thanks a lot .
Is there a particular reason to have the longer part in the bottom?
I have seen chassis with all 4 in the bottom like i planned to do . But also some chassis where the lower ones where with the bottom ones long , and the upper rails where inverted so the longer bit was on the top parts.
Thanks
Sam

Offline THE FRENCHTOWN FLYER

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Re: Jr dragster chassis
« Reply #4 on: December 16, 2022, 05:29:08 PM »
Thanks a lot , I plan on doing the diagonals this afternoon . So just in time ;) thanks a lot .
Is there a particular reason to have the longer part in the bottom?
I have seen chassis with all 4 in the bottom like i planned to do . But also some chassis where the lower ones where with the bottom ones long , and the upper rails where inverted so the longer bit was on the top parts.
Thanks
Sam
I think it may have to do with the bending moment put on the frame rails. If the frame wants to buckle in its middle from bending (visualize bouncing down from a big wheelie) then the bottom side of the bottom member will be in tension and the load can be distributed over the larger section of the 45 degree bend. Likewise the top side of the top member will see the biggest compression load and then the top of the top rail would be the most highly stressed and hence would benefit from the top side being longer.

Offline samotorsport

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Re: Jr dragster chassis
« Reply #5 on: December 19, 2022, 09:21:44 AM »
Thanks a lot , yes this makes sense ;)
So on the jr not that important , but still , lets make it correct right away ;)
Thanks

Offline samotorsport

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Re: Jr dragster chassis
« Reply #6 on: December 19, 2022, 09:24:17 AM »
Current state
« Last Edit: December 19, 2022, 09:27:09 AM by samotorsport »

Offline wideopen231

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Re: Jr dragster chassis
« Reply #7 on: December 19, 2022, 04:34:47 PM »
Looks good. building yourself should save some cash and be better piece to boot. CM over mild steel is no brainer.Any weight shaved with smal motor is huge.
Relecting obama is like shooting right foot because it did not hurt enough when you shot left foot

Offline samotorsport

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Re: Jr dragster chassis
« Reply #8 on: December 19, 2022, 11:29:58 PM »
Thank you ! I will update this regular .
Next step , welding closed the remaining cell , then additional bars to the rollcage .
After that , front half . But this is only going to happen „next year“ :)