Hotrod Frame Help

Hello Everyone,

I have been reading and considered all ideals from this board and all around. I have come up with a final design and plan to build my first Rat Rod frame.

I plan on using 0.125 wall 2x4 rectangular tubing, hot rolled steel.

I want the stance to be about 4" off the ground. This is my overall look on the vehicle. I confirmed that all scales are correct.



Major components:
30-31 sedan body to be channeled 4" and chopped 5"
9" rear
305cui sbc - TH350
single tube axle A style front suspension
triagulated 4bar rear suspension w/coil overs
Homemade frame - design in question. Huge Z in the rear.


I am hoping to get some feedback from some of you experienced guys:

Can someone tell me if i am on the right page?
Does the frame look like it is within reasonable geometry that with correct welds and aligment will it work?


This is the first time buildng a hotrod and I have read just about everything about 4bar suspension, single axle suspension, drive train and frame building on this forum, but none the less I lack the experience! Thanks for all your help in advance.

 

Frame looks right from the side,
I would probably ether set the motor back another few inches, or move the front axle further forward to gain a bit of space so the axle and rad are not fighting for space, but yeah as a side view for making up some rails its fine.
Have you got a plan view of the project ?

 

Looks like a great start!

Here's a link to a model a frame that Grant Schwartz is building in Bloomingdale... you may be interested in a shop tour on the 28th if you're in the GTA.

Anyways, it looks similar to your drawing... I hope we can help with your project.

http://www.jalopyjournal.com/forum/showthread.php?t=317485

 

Looks good.
You thinking ahead,I like it.The rad out front works here so you have some cooling.
Maybe stretch out the frame horns a bit do keep a stock(ish) look.

The trans tunnel will be big,in the drawing maybe lower the motor/trans just a bit.
You sure do not want anything hanging down with a 4" ride height...so a bit maybe..

And with 4" ride height you don't want much in rear travel,rather bottom out the suspension then have the frame hit the ground..

Great drawing..keep us posted !

 

I usually level out my front frame rails .Looks good also ditch the R%t R%d term you are using blue prints .My 2 cents

 

Thanks for the feedback! I have played with the engine mounting quite a bit. The driveline is basically telling me to put it in that position. The lower I go, the bigger my angles btwn drivesaft and pinion. From What i understand anything over 5 deg. = big trouble.

To address the bottoming out issues. I will have to put in bumpers.

Oh and of course, here is the top view.



Thanks for your responses, confidence in the design is half the battle for me. Stops me from second guessing myself. In the ideal world, I would like to do it right the first time but I am prepared to live and learn.

 

The next thing that I am searching is a tech article for putting the frame together. I have seen 3-4 tech articles on this forum already that give a reasonable outline on what needs to be done.

I am looking for something more along the lines of welding tech that helps newbies put together a straight frame without too much warp and how to end up with a square straight frame.

Can anyone comment on what checks to make while tacking and welding the cross members together?

 

Welcome to the HAMB... now a few quick things.. do an intro.. lose Rat Rod from your vocabulary, try traditional hot rod on for size. The drawings look good and never has that amount of thought gone into a RR. Otherwise come on in...

 

looking at the plan view,
I would suggest the rails need wider apart where the seats mount.
I aim to get the seat fixings inboard of the rails completely,
standard mount centres on seats are 11 1/2 and a seat typicaly 18 wide where it matters, allowing say six inches for the tunnel so I would give myself 36 inches clear between the rails at the front and rear of the seat positions.

I think it's even more noticable in plan view that things would probably be improved by the motor and trans moving aft by a number of inches.
There is no downside to recessing the firewall to allow the motor and trans to move back and gain some space in the front axle radiator area, other than maybe access to dizzy maybe, even that is usually fairly easy to get round with a removeable plate.

I would guess that if you do a rough calc the front axle is carrying far more wieght than the rear, so I would set the motor back further and try and even things up.
I know that may slightly increase the drive line angle, but given a choice I would go for getting the axle loads even and don't worry so much about the angle.
It's easy to get hung up on detail and miss the big picture.
Re-model the oil pan if need be so the motor can sit lower and less tilted, that will sort the drive line angle.

Other than that I would start cutting steel and making those rails, coz it's looking good,
And I still figure that it's cold out in the workshop so it's better to spend time getting the drawing right in the warm.
I know some people don't bother doing a drawing a working out things first,
but it's I still see that as "planing to fail = failing to plan".

 

Thanks Thunderace for your suggestions. Maybe my dwg is a little off with the seats. I dont have them yet so i dont know what size they will be. The subframe is maybe 2" wider than the actual frame. I dont think i can get it any tighter without leaving room to work with. These sedans are pretty tiny... I am definately going to have to get smaller seats.

I have the engine tilted at about 3* which is what seems to be a convention in drive trains. I got the material from this website: http://www.iedls.com/ptsetup.html They have tech manuals and everything makes sense to me.

I never though about weight distrubution... But having people, sedan body, and gas tank... wouldnt that help even it out? I am affraid to move the motor back as the bell housing keeps eating up my pedel space. What is the ideal weight charateristic for a well balanced car? Perhaps I can estimate the center of gravity for my car.

The purpose of this car is not to race or drag but more for cruise and comfort. Safety is the more important than anything, the last thing I want is to spin out of control b/c I built the thing front heavy.

Its almost like every decision has a benefit and sacrifice.

 

Ideal, depends on your selection of wheels and tyres.
If all four were the same then the ideal would be 50/50 front rear split,
if the rears are larger than the fronts then increasing the rear wieght bias accordingly is the way to aim.

Sure fuel, passengers etc are part of the numbers, ten gallons of fuel and two people will give you about 400lbs say, maybe 450, which goes along way toward equalising the axle loads.
Thing is you have a drawing to work from, so doing a few sums to check is no biggy.

As to the angle of the engine and trans, the link says 'approximately' 3 degrees, trust me there is nothing that is going to be upset be a one or two degree change in the tilt of the crank, if this were not the case all roads would have to be perfectly level with no hills ever !
I would suggest that as long as you keep a small upward tilt and as straight a drive line as possible given other constraints everything will be perfectly fine.

Yeah I know what you are saying about the bellhousing eating up space, but even with a manual box with three pedals ten inches width is all you need and you don't need the full ten width all the way back to the firewall, only where the pedals hang in space.

From experience I can say that getting the weight distrubution somewhere near makes by far the biggest diffrence to the way a car behaves, does not have to be spot on, but way off always results in a vehicle which is horible to drive, so it's worth putting in some effort at the design stage.

 

So this is the result from 3 weekends.

You were right about the horns... I had already ordered the material so I could not extend them but they do look kind of short. But other than that, all is per print.

Thanks for your input! Now im going to move on to the body.

Cheers,

Tony