Build - 9 second drag truck #racegreen

[rockjeep73]

What do you mean by putting the instant center behind the rear axle? I don't ever see a reason to go below 40%.
Maybe I missed it earlier but what are the specs on the tires.

 

[bgreen776]

I'm a little fuzzy on what exactly happens when you place your links so they are farther apart on the frame than they are on he axle, but I believe it would put your IC at axle centerline or behind it. I don't see any reason to ever do that, but I might have to model it and see what happens.

For tires I decided on the Mickey Thompson 3560 34X18.50-16LT M/T ET Street R.

#racegreen

 

[rockjeep73]

Gotcha. You won't ever go there.

You said you were going off of 21" COG height. Where does that put the crank centerline height? If you don't mind me asking.

 

[bgreen776]

The crank height will be around 16" give or take an inch or two.

 

[AHall]

Engine sitting high.

 

[bgreen776]

It's sitting on the steering rack, not sure how its going to get any lower than that.


#racegreen

 

[AHall]

What's your ride height look like?

 

[bgreen776]

It's as low as I can go without building a custom front suspension. Or moving the motor back another foot


#racegreen

 

[jlibert]

The crank height will be around 16" give or take an inch or two.

Is that front, rear or average height?

 

[AHall]

It'll be fine. Save you the energy of building a new oil pan too.

 

[bgreen776]

Is that front, rear or average height?

Average


#racegreen

 

[bgreen776]

Leveled, squared, and 2.5" shorter than stock. I'm either going to cut 2" out of the fenders or make longer control arms... Not a fan of the look with the tire so far forward in the wheel well.

#racegreen

 

[Bodacious]

I'm either going to cut 2" out of the fenders or make longer control arms

I think those third & fourth gens short beds already pretty much have the wheel well centered. That's why a flat bed looks so goofy on them.

We cut a section out of the rear of our bed to shorten it.

Before:

After:

Unfortunately in your case, you'd have to cut from the front and the back to get the look right and those bed sides do not have straight body lines.

Looks like longer control arms will be the easiest fix.

 

[bgreen776]

I had not considered that, thank you.


#racegreen

 

[TheBac]

You guys know far more than I do, so hopefully you can answer my questions. I dont know exactly how to word them, so bear with me.
Since you're building off the shorter OEM frame to that much-taller 4 link bracket crossmember, isnt there going to be a risk of that section "folding" when under extreme stress at launch because it has to "neck down" to the OEM frame??
Are you planning on reinforcing that bracket x-member with gussetts and have tubing connecting to it up higher, maybe using the rollcage rear bars as the upper bracing?
What about the lower tubing? Since its not "level" with the bottom bars, do you have to add extra bracing there, too? I always thought the stresses had to be dealt with in a linear way?
I love your skills and the builds you guys are doing, so please dont take all this the wrong way. I'm just curious (and a bit concerned) b/c I dont know. Thanks.

 

[okie18]

The roll cage will tie into the top bar unless he has some secret squirrel stuff planned :lolly:

 

[bgreen776]

You guys know far more than I do, so hopefully you can answer my questions. I dont know exactly how to word them, so bear with me.
Since you're building off the shorter OEM frame to that much-taller 4 link bracket crossmember, isnt there going to be a risk of that section "folding" when under extreme stress at launch because it has to "neck down" to the OEM frame??
Are you planning on reinforcing that bracket x-member with gussetts and have tubing connecting to it up higher, maybe using the rollcage rear bars as the upper bracing?
What about the lower tubing? Since its not "level" with the bottom bars, do you have to add extra bracing there, too? I always thought the stresses had to be dealt with in a linear way?
I love your skills and the builds you guys are doing, so please dont take all this the wrong way. I'm just curious (and a bit concerned) b/c I dont know. Thanks.

The goal, as I see it, is to build sub assemblies that rely on other parts of the entire assembly, to meet strength requirements. IE: the subframe in question should not be strong enough to support the load all on its own as that would make it heavier than necessary. Ideally everything would tie together in a way that provides the greatest strength and the lightest weight.

There are lots of missing tubes in the drawings below, but as of last night, they represent where my head was at in relation to the back half of the chassis. I'm not happy with the curve in the two bars that come out of the back of the cab right above the rear window, so I'll change that up at some point.

 

[TheBac]

Thank you for that explanation. Makes sense.

 

[bgreen776]

No problem bud. I'd like people to ask more questions, that is a big part of what makes a good build thread. :Cheer:

I just can't get my head wrapped around the standard rear "down" bars (51 A and B), so I'm either going to build the chassis without them and add all the gusseting required by 25.2B or I'm going to bend them the other direction so they dont show at all. (or both) I see two big advantages to this other than looks, the first and most important, is that I can tie the bend points into the rest of the structure resulting in a stronger assembly. The second is that it places the welds in a location I can more easily access. Too bad I already took a hole saw to the back of the cab. :doh:

Edit: With this design, the down bars will exit the cab just below the rear window.

 

[bgreen776]

Just a little update today. I finally bit the bullet and cut out the back of the cab to make welding a little easier, and bars 51 A and B are done.