1303 Front End Idea

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Jadewombat
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1303 Front End Idea

Post by Jadewombat » Sat Sep 24, 2016 10:01 am

OK, time to reinvent the wheel on paper again. Sorry, can't help myself after seeing this. It's a Datsun truck that a guy is redoing to incorporate his knowledge of auto-x and all the modern goodies. I can't figure out why he wants to stay with a solid rear end, I know it's 5 link, but still even that momentary non-optimal full contact of the tire patch cornering would bug me.

Anyhoo, the front end is what caught my eye on this truck. He has what looks like a-arms and torsion bar, I'm assuming the bar is indexed to set the ride height, and lay flat shocks. If, on a 1303, one were to weld a spherical bearing and bar (similar to the picture) to the lower arms, replace the stock sway bar and fit with this indexed torsion bar to the very forward part of the bulkhead, then this would free up running lighter front struts and springs (4 or 10 way adjustables to really be able to dial in). Would this be a benefit? Again, we all know the 1303 front end design of struts, single lower arms, and forward sway bar was for economy of the manufacturer to build and to free up space in the trunk, blah, blah.

I know on the rear end of IRS bugs guys have been opting to remove the torsion bars and run coilovers altogether on off-road and road course cars. HOWEVER, the front of 911s had torsion bars, semi A-arms, and separate shocks for years and had great response from them. The basic--the springs control the body (roll) of the car and the shocks control the bumps would apply. So, thoughts?

http://community.ratsun.net/topic/70329 ... 620-build/

This guy really knows his stuff:

http://community.ratsun.net/topic/70329 ... ild/page-4
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Marc
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Re: 1303 Front End Idea

Post by Marc » Sat Sep 24, 2016 10:52 am

There're a number of ways one could improve the stability of the Super front end by providing something better than the stock swaybar/bushings to control fore-and-aft movement. The long single lower control arm is probably the biggest liability of the design. Fiat used a similar arrangement on their 128. Surprisingly it had fewer issues than the Super, even though it was also tasked with putting power down - many competed very successfully in SCCA racing, but when we built one for circletrack (with 11" slicks on the front) it was obvious that it would be inadequate.
First order of business was to remove the swaybar and fabricate an additional link to tie into the control arm so it would be more "A-arm"-like for positive wheelbase control. We didn't need a front swaybar for that application, with a locked differential there was no need to promote understeer ;)

If I understand what you're saying, you would be retaining the basic layout of the stock setup, just replacing the rubber-bushed connection between bar and control arm with a bearing and substituting a more robust & adjustable bar. The only thing I can see which could go wrong with that is that there could be binding as the control arm moves up & down in an arc while the lever off of the swaybar only moves in one plane - you may have to come up with a sexier connection at the bar, perhaps incorporating a Heim end.

Stock Fiat128: http://img.photobucket.com/albums/v202/ ... C04994.jpg

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Re: 1303 Front End Idea

Post by Ol'fogasaurus » Sat Sep 24, 2016 11:06 am

Pile, the rear with the bell-crank shock mounting is reminiscent of some of the Indy car suspensions but I think I see a Panhard ("A Panhard rod [also called Panhard bar or track bar] is a suspension link that provides lateral location of the axle. Originally invented by the Panhard automobile company of France in the early twentieth century, this device has been widely used ever since." Wikipedia. The problem with that bar as it can induce an arc/sway in the rear live axle) bar where I think Watts linkage ("Watt's linkage (also known as the parallel linkage) is a type of mechanical linkage invented by James Watt [19 January 1736 – 25 August 1819] in which the central moving point of the linkage is constrained to travel on an approximation to a straight line. It was described in Watt's patent specification of 1784 for the Watt steam engine. It is also used in automobile suspensions, allowing the axle of a vehicle to travel vertically while preventing sideways motion." Notice the animation and notice that it is a very long travel arc) Again, Wikipedia. Unless the travel is minimal and the Panhard bar is set up very correctly, with the Watts linkage there s/b less side to side movement in a live rear axle this way.) s/b. The Panhard bar is simpler with less moving parts but with all the other fiddly stuff I see, why not go with the Watts linkage. I too wonder why something like a Jag, Corvette or other similar rear suspension isn't used.

The front is missing too much info on the mechanism the coil overs hook through (a gear case?) but again, it is reminiscent of Indy shock mounting. It seems to me that for some reason they stopped using horizontal and low angle coil overs shocks a while back but I haven't kept up on what they are doing for a long time. It's mimic was popular in street/show rods for a while but now there are other things they are doing.

The art work on this is top line though.

My opinion. In this case it is worth much less than it would take to blow it to hell.

Lee

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Re: 1303 Front End Idea

Post by Jadewombat » Sat Sep 24, 2016 3:02 pm

Marc wrote: If I understand what you're saying, you would be retaining the basic layout of the stock setup, just replacing the rubber-bushed connection between bar and control arm with a bearing and substituting a more robust & adjustable bar. The only thing I can see which could go wrong with that is that there could be binding as the control arm moves up & down in an arc while the lever off of the swaybar only moves in one plane - you may have to come up with a sexier connection at the bar, perhaps incorporating a Heim end.
Correct, I've always thought the sway bar on a 1303 when pushed to it's limits under racing could use some help controlling the lower arm from moving front and back. Also true, because of the arc of movement of the lower arm up and down (which translates to diagonal movement), either a heim joint to connect the (let's call it a torsion arm) to the stock lower arm OR two beefy tabs welded on the lower arm which sandwich around the torsion arm and a spherical bearing with a bolt through it.

I'm not so much interested in the lay-flat shocks (although they work awesome on racing Porsches and the infamous T1 Race Taxi microbus!) because on an '03 all that hacking of the side of the strut tower would weaken the chassis too much, you'd have to reinforce the holy hell out of that area to mount the shock pivots, and then you'd have essentially nowhere to fit the fuel tank, etc.

This torsion tube and torsion arms on an '03 could either fit in the stock sway bar location, or in the interest of moving heavier stuff towards the CoG just behind the lower arms, M/C, etc. extending the torsion arms forward.

This is on one of their 70s Camaros (same guy as the Datsun, different car) showing the torsion arms connected to the A-arms and the torsion bar.

https://youtu.be/2wDAfm82J_w
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Re: 1303 Front End Idea

Post by Jadewombat » Sun Sep 25, 2016 2:37 pm

Something like this, maybe with uniball connections, etc.
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Re: 1303 Front End Idea

Post by Marc » Mon Sep 26, 2016 12:23 am

I'm sure you're aware that moving the attachment point that far inboard would reduce the ASB's effectiveness by ~40%, so a bigger bar would be req'd to compensate. It would reduce the angularity problem somewhat though.

You mentioned the possibility of mounting the ASB behind the control arms (see: GTI Rabbit). If your ride height is sufficient to allow for that the idea's worth pursuing...if for no other reason than it would isolate wheelbase control from the "crumple zone" at the nose (a big deal in roundy-round, perhaps not so much for you).

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Re: 1303 Front End Idea

Post by Jadewombat » Mon Sep 26, 2016 4:31 pm

Yeah, I should've looked at the picture again before posting. Attachment point the middle of the lower arm instead out at the corners would be less effective. The torsion arms would have to be a 'S' shape in either case if the tube is mounted in front of or behind the torsion tube. Thanks again.

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Re: 1303 Front End Idea

Post by Piledriver » Tue Sep 27, 2016 2:10 am

If I had a super I'd look at grafting in 914 or 911 front arms/struts torsion bars and all ~kinda like Aircooledtechguys Square.
Would probably be ~a cakewalk as there is structure and strut towers already present.
I strongly considered doing ~similar with he arms reversed and an upper A-arm, chopping the struts down ~to spindles and sticking a ball joint on top of the spindle.

Annoyingly the 911 and 914 bars are splined different.

Rear steer tho... would make things ...interesting.
There are different struts/spindles you could use with the 911 arms etc I imagine.
I, for one, regularly embrace our new robot overlords, as I am the guy fixing the robots...

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Re: 1303 Front End Idea

Post by Jadewombat » Fri Aug 11, 2017 12:33 pm

The idea is catching on elsewhere, too. This is a '70 Cuda drift build. They bent the control arms out to the side also. About 6mins into this video-

https://www.youtube.com/watch?v=-mocix-KcI8

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