Further my education on "truck arm" rear suspension

Caltracs go below the existing leaf spring and be easy to install.

http://www.calvertracing.com/caltracs.html

If you want more help locating a Watts link could be added and not bind / "need to be flexible".

Adrian_Thompson wrote:

Chris_V wrote: You want tire clearance for a lowered Falcon? Mini tubs and move the springs inboard of the frame rails with a cheap weld in kit. It's pretty common and allows for 275s in the back easily. http://www.tffn.net/phpBB3/viewforum.php?f=11&sid=0b7057f2b989c4ea05bca88202e14557 http://www.tffn.net/phpBB3/viewtopic.php?f=11&t=29659&p=218734&hilit=chuckbizkits#p218734 The Crites restorations kit is $169 and moves the springs inboard for lots of clearance.

Those sites require registration to view the threads. I'd avoid moving the springs in board as much as you can. In board doesn't affect straight bump motion as in drag launches or speed bumps, but the further in board yo move a spring, you effectivley reduce it's rate in roll. So if you move them in, you either need to have higher rate springs to keep the roll resistance the same and ruin your ride, or you up the rate to keep the correct roll resistance and end up with a harsh ride in double wheel bumps. Bloody physics, always a sodding trade off!

Well, the guys that do it and daily drive their classic Falcons with wide tires don't seem to have a problem with it at all. I'm going to be doing the same with my '63 Comet (which is just a fancy Falcon). I had no problem with 3" lowering blocks above my leafs on my last Falcon, and that supposedly messes with the roll resistance, too.

If it's really a problem, just add a rear rollbar.

As for the site, if he owns a classic Falcon and isn't registered on that site, he should be...

Chris_V wrote:

Adrian_Thompson wrote:

Chris_V wrote: You want tire clearance for a lowered Falcon? Mini tubs and move the springs inboard of the frame rails with a cheap weld in kit. It's pretty common and allows for 275s in the back easily. http://www.tffn.net/phpBB3/viewforum.php?f=11&sid=0b7057f2b989c4ea05bca88202e14557 http://www.tffn.net/phpBB3/viewtopic.php?f=11&t=29659&p=218734&hilit=chuckbizkits#p218734 The Crites restorations kit is $169 and moves the springs inboard for lots of clearance.

Those sites require registration to view the threads. I'd avoid moving the springs in board as much as you can. In board doesn't affect straight bump motion as in drag launches or speed bumps, but the further in board yo move a spring, you effectivley reduce it's rate in roll. So if you move them in, you either need to have higher rate springs to keep the roll resistance the same and ruin your ride, or you up the rate to keep the correct roll resistance and end up with a harsh ride in double wheel bumps. Bloody physics, always a sodding trade off!

Well, the guys that do it and daily drive their classic Falcons with wide tires don't seem to have a problem with it at all. I'm going to be doing the same with my '63 Comet (which is just a fancy Falcon). I had no problem with 3" lowering blocks above my leafs on my last Falcon, and that supposedly messes with the roll resistance, too. If it's really a problem, just add a rear rollbar. As for the site, if he owns a classic Falcon and isn't registered on that site, he should be...

If you move the leaf in 6 inches and make the tire 6 inches wider to the inside it has the same effect on the suspension in roll as moving the leaf in 3 inches and leaving the tire the same. Completely random numbers for example purposes. So its not as bad as he makes it out ot be, but its still not good. Though you do have to move the coil springs in just as much, if not more than the leafs if you go that way too so, there's that.

Sounds like you need a torque arm.

Adrian_Thompson wrote:

Ditchdigger wrote:

That Alfa system is similar to the early Jaguar C types and early Mk I Lotus Cortinas in that it uses the 3rd link to handle the lateral loads as well. In all cases it puts tremendous strain on the single pivot point of the 'A' (or 'T') arm. The biggest drawback though, other than the loads being put through a single point, is that the arm also dictates the roll center, which for the Alfa and the Jag were very high. Much lower and more manageable for the Cortina. Note both the JAg and the Lotus Cortina soon reverted to more traditional rear suspensions due to issues with the handling (Jag) or fragility (Lotus Cortina) Early C type Lotus Cortina (arly cars top left, later cars lower right)

None of the pix or descriptions in your post is the Alfa system I am talking about.

Here's a pic, it's not a great picture, hopefully you can see the large training arms. This one uses a rear transaxle and DeDion, but concept is the same, just substitute live rear axle in place of the transaxle and DeDion tube:

https://search.yahoo.com/search;_ylt=AibSdRCoNhIdAhkJ_Db4QqCbvZx4?fr=yfp-t-250-s&toggle=1&fp=1&cop=mss&ei=UTF-8&p=alfa%20de%20dion%20suspension

I have nothing to add to this thread except to say that I find it very interesting. I know little to nothing about any of these rear suspension designs, and I'm really curious about a basic primer on the advantages and disadvantages of each. Can anyone point me to such a primer?

I've seen examples of each design in build threads (especially over at the Locost forum), but don't know anything past that.

In reply to Mezzanine:

Other than picking up a suspension dynamics textbook, not really. Its such a complex(on the theory side), highly opinionated (on the practical side) subject.

The Locost forum is pretty good, it sounds like you've already been primed.

In reply to Mezzanine:

See if you can pick this book up somewhere. It has a couple chapters on different rear suspension designs. It doesn't get too technical but kinda gives a brief synopsis in layman's terms.

erohslc wrote: None of the pix or descriptions in your post is the Alfa system I am talking about. Here's a pic, it's not a great picture, hopefully you can see the large training arms. This one uses a rear transaxle and DeDion, but concept is the same, just substitute live rear axle in place of the transaxle and DeDion tube: https://search.yahoo.com/search;_ylt=AibSdRCoNhIdAhkJ_Db4QqCbvZx4?fr=yfp-t-250-s&toggle=1&fp=1&cop=mss&ei=UTF-8&p=alfa%20de%20dion%20suspension

I was meaning to reference the Alfa 'T' bar system not the DeDion you posted. I've never really seen the point for a DeDion system on a modern, or fabricated car. If you're going to do so much work I don't see why you wouldn't just do a true IRS rather than the complication of an IRS but with the geometry (although less unsprung mass) of a live axle.

Adrian_Thompson wrote:

Ditchdigger wrote:

That Alfa system is similar to the early Jaguar C types and early Mk I Lotus Cortinas in that it uses the 3rd link to handle the lateral loads as well. In all cases it puts tremendous strain on the single pivot point of the 'A' (or 'T') arm. The biggest drawback though, other than the loads being put through a single point, is that the arm also dictates the roll center, which for the Alfa and the Jag were very high. Much lower and more manageable for the Cortina. Note both the JAg and the Lotus Cortina soon reverted to more traditional rear suspensions due to issues with the handling (Jag) or fragility (Lotus Cortina) Early C type Lotus Cortina (arly cars top left, later cars lower right)

The Cortina rear ended up being a early example of the Capri rear. A pair of leaf springs and 2 upper links that controlled wheel hop, etc. On later models (1972 & later) Ford installed a rear sway bar that they tried to use as both a traction link and a sway bay. It didn't work well at either. I owned a number of both 4 & 6 cylinder models back in the day. It wasn't until I fabricated "Shelby Mustang" like upper links that the traction problem was solved. These came through the rear floor and bolted to were the rear seat was. Again similar to the 1965 GT350's.

Kenny & Nick, thanks- I've been meaning to pick up that book for years now and just never got to it. Will do.

Adrian_Thompson wrote: Lotus Cortina (arly cars top left, later cars lower right)

I used a setup like the later model on this car.

I had 3" lowering blocks in the rear and had problems with axle wrap. So I made my own traction bars and brackets. I welded the brackets to the axle and the other end was bolted to the rear floor where the rear seat used to be.