hot rod chassis trends

[Tmoose]

It seems like massive crossmembers, severed at the middle, then joined with a wisp of bent tubing or bar stock are popular even in some high end hot rod chassis.
Also popular details are additional longitudinal rails located inboard of the main rails, often by a single crossbeam, which the single main rails are stuck onto sometimes at mid span.
Some of these are intended to go under cars whose bodies offer little or no structural assistance.
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http://www.artmorrison.com/gallery/...ownloadItem&g2_itemId=23937&g2_serialNumber=1

http://www.artmorrison.com/images/49-54Chevy/final/sized/AME-9337.jpg

http://waclark0.tripod.com/sitebuil...ictures/.pond/stus-chassis-2.jpg.w560h420.jpg

http://image.minitruckinweb.com/f/e...idwest_camp_n_drag+custom_rear_suspension.jpg

http://www.minitruckinweb.com/events/midwest/0901mt_2008_midwest_camp_n_drag/photo_13.html#

http://www.precisioncarrestoration.com/wp-content/uploads/2009/11/PB102928-300x225.jpg

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By mere jaded inspection I don't see how they are that appropriate to receive and transmit chassis loads or barely support transmission tail housings.
Details that would do A far better job, using less material seems kind of obvious.
I realize once something is strong/stiff "enough" to roll around town or down the highway for 10-15 years THAT probably is also "good enough"

 

[MikeHalloran]

My uncle found an unmodified '32 Model A 3-window coupe, and was finishing up a restoration of sorts when he died. I got to see it at various stages of (dis)assembly. I was particularly struck by how thin the original metal was was, both body and chassis. ... not from corrosion; it was a lightweight car.

Most hot rodders are craftsmen, not engineers. They tend to copy stuff that looks cool, but are not equipped to judge whether a structure is efficient or even adequate. They engineer by experience; if a hard launch wrinkles the chassis, they fix the wrinkle and reinforce the area around it, and recurse until stuff stops breaking. Then they go into business to try to recover a little of what they have spent on 'development'. ;-)



Mike Halloran
Pembroke Pines, FL, USA

 

[BrianPetersen]

In the first photo, the massive crossmember where the rear suspension arms attach is probably not actually needed at all inboard of the suspension arm attachment points. The stub extending inward from the main frame serves to transfer the load to the frame rails, but the part in the middle likely doesn't do much. The thing that is not known from just that photograph, is whether the body of the vehicle is supported on the middle part of that crossmember, although given that the drive shaft goes through there even on the vehicle that this chassis was designed for, it's unlikely.

Most of those frames are likely stronger than the original frame underneath that vehicle, even if the design perhaps might not be "optimum" from the engineering point of view.

 

[LionelHutz]

The Art Morrison stuff looks like 30's Ford replacement frames and while they don't have much torsional rigidity I don't see much concern running them under such a vehicle. Could a different structure or more bracing help the rigidity? Probably, but they're likely more then capable for their intended purpose.

The truck ones? Well, the first one isn't terrible since the suspension control arms tie into the main frame under the cab and it looks better there. But that 90* bent tube bracing the rear frame rails is useless and some diagonal support for the rear rails wouldn't hurt. The rear rails would have been better extending forward under the cab or I would have put those other tubes further inboard in-line with the rear rails. I would hope the second one is nothing more then a frame for a show truck so it can "lay frame".

The ladder structure down the middle of the last one certainly is a waste with it bending back to the outside rail. It's not completed either.