Double dip tube axle on hairpins with quarter ellipticals...

I said I was done with it but if I must repeat myself.

The T-bucket is a much lighter vehicle and because it is a much lighter vehicle the axle sees much less forces in the "X" and the "Y" direction while seeing the same twist forces. This reduction in forces means that the axle will not fatigue as quickly as a car with more weight. it all comes from the culmination of weight or forces applied to the axle. Lighter car, less magnitude of force. Heavier car, larger magnitude of forces applied.

I don't know T buckets, don't like T buckets, and would refuse to ride in a T bucket. They are just not for me. Therefore I have no supporting evidence that T buckets axles fail. Thats just me, go on and build them you are free to do as you wish. I was only answering a question about the possibility of axle failure because of the application of hairpins on a tube axle. I didn't bring up T buckets killing folks you did!

I have never did the calculations to determine the fatigue or failure time expected, this is only a hypothetical situation. You ever think that the failure of the axle under those conditions is something like 20 million cycles which converts to lets say 50 years. How long have they been building buckets? Something to think about, I am pretty sure that the Hot Rodders who did it in the past didn't calculated the fatigue rate either. They just did it, cause they could. Doesn't mean it is right or wrong.

There are alot who state that you should not do it while other say go ahead. I am an engineer who is saying that it is not a good idea to put any member under 3 different destructive forces like you are asking about.

Thats all.

 

Brewsirs right on in my opinion as it relates to using wishbones or Radius arms.
I remember the Harlan posts...clever guy.

Brewsir wasn't talking about the Dave Gale (DG) setup, but just to add to it...with the DG design, any difference between the lengths of the springs and the upper locators would be absorbed by the spring/locator bushings when you consider the amount of articulation you would be likely to see in a street driven vehicle.
Any you DID see at the extreme limits would still be way below the stress levels of a normal Radius arm/tube axle setup at the same limits...

 

Diagram for better explaination.



***uming a person WERE to run pins and quarters, this is why I ***umed inthe beginning that shackles would be needed.

The pins give the axle a certain swing arc, represented here in blue. The longer the pins, the shallower the arc.

The springs, if hard mounted, would have an arc of their own, represented in red.)

If the sprins were hard mounted it would cause a bind because the pins arc would cause the springs to want to flex like a rainbow (for lack of a better explaination).

Sound right?

So, if a person were to mount the shackles in there too it would cancel that bind.

 

...

 

You've already said you're dead set on doing it and you've already gotten opinions before from people before this thread that say they've done it for years with no trouble. (again pointless. Time has no bearing. How much have they driven it in those years and on what kind of roads, etc.) Why bother come on here asking if you aren't going to listen anyway? You said you wanted to hear from a few more people that have done it, looks like you have it. Build it. Pretend fatigue doesn't happen. You might not ever have a problem. Pretend all the parts will work perfectly. You're really not far off from doing it a better way, but when folks mention it, you don't seem to want to hear it. (I'm talking coming from the more experienced folks here, not myself) Driving on smooth even roads aren't going to stress it much anyway.

 

No, I have no problem listening. In fact, I'm in the modst of PM conversations with 3 people who have explained why it's a bad idea, and I'm taking notes so I can find a way around any no no's.

I just don't take kindly to this "engineer>everyone" thing that some people get.

And yes, fatigue is a factor. I have a degree in welding and metal fab... believe me, fatigue is something that I spend more than adequate time thinking about. But it's not a reason NOT to do something... it's a good reason to accept the challenge and find a way to do it BETTER.

Thanks for the concearn.

 

Then take a tip from the torsion bar dragster guys. They slot the suspension mounting holes so as not to bind. But then hole wear will be a problem.

 

As long as the hair pins and a possible panhard are locating the axle a pair of shackles should get rid of bind I think.

Any thoughts?

 

How about an upper slide-a-link on each side, kinda like a rear top slide-a-link on a race car. The springs hold the weight not the hairpins so maybe that'd give you more travel without bind.
I would also like to say I scored a 64 on that mechanical appitude test thing but did get down to one pin on that triangle game at Cracker Barrel...lol

 

You mean run the springs as the lower of the 4 links, and slide-a-links as the uppers?

 

I have no experience with this, but looked into it at one point. Anyway, Posies's sent me the following attachments when I inquired into their setup. Hope they don't mind me posting them here. They indicate use of a Panhard bar.

Tony

 

Oops! Here are the pics.

Tony

 

That's actually really helpful man.

Looks like they do recommend use of shackles for sure.

 

With the 1/4 liptic set up you don't need shackles or a panhard rod. The shackles are the loosest link. Make 'em go away and just put on tabs for the spring mounts.
The best way to do your deal is to just run a beefy single(upper only bar and no shackles) and that way the bones won't take on the task of anti roll bars in turns like a hairpin or split bones do.

 

There is a good thread that has lots of information about Quarter Elliptic installs by your fellow HAMBers

http://www.jalopyjournal.com/forum/showthread.php?t=214929&highlight=posies

As mentioned above and illustrated by the diagram : A shackle takes up the tendency of the leaf spring to elongate allowing the spring to travel through its arc without binding as the hairpin travels through its own arc. Now keep in mind, most straight axles will only travel X inches anyway so you will not see an exaggerated difference in the two arcs. A shackle is still recommended.

If a shackle is not used and the spring eye is attached directly to the axle, you could experience a bad ride quailty, the bushings gets killed in no time which could lead to other problems included broken mounts. We have tried it without shackles......and changed back to a shackle or swivel system.

We developed the Swivel Shackle to address several different issues and they work great, especially on rear axle applications. We offer them for quarter elliptic front suspensions using an I-beam or tube axle along with a rear axle kit. We also offer and have used the T-Bolt type mounts that allow the shackle to rotate slightly helping to eliminate binding.




Hope this helps,

Todd Fenton
POSIES, Inc.

 

You don't use shackles and a Panhard bar on the same axle.

Unless you want to create a bind.

 

I guess that makes you the most qualified.

 

durr

good point. haha

too much thinking today.

 

if we all waited for the experts(engineers, architects) to tell us if something worked, we'd all still be looking at the drawings

 

Man...SO many opinions on this its almost scary isn't it!?!?

The odd thing is...pretty much EVERYTHING that's listed as being unworkable has been proven to work in other situations.
Like saying that a Panhard can't work with parallel spring setups.

I tend to AGREE and there doesn't SEEM to be a need for one, yet Jeep YJ's have them and so do Dodge Caravans! BOTH with leaf springs!!!
I'm sure things have been altered a little in the design to acommodate them, but THATS the point...things COULD be altered enough to make them work. Nothing is carved in stone.

MPLS...theres a load of stuff to consider here besides the possibility of metal fatigue, but ultimately it comes down to your decision. Can YOU be happy knowing that your possibly on the edge safety wise?

Personally, I just don't have the faith in tubing to drive such a setup without having that little jab of worry always in the back of my mind...especially when so many alternate designs are available that take the workhardening etc right out of the equation.
4 link, 3 link, 1/4 Elip + links, rotator sleeve...on and on. Many have their own set of compromises to deal with. It's a real struggle to pick one over the other sometimes...

I wonder, seeing how you like the radius arm look so much, would the simple addition of rubber bushings in place of the 4 front Heims be enough to allow for the needed amount of street articulation and long term durability?

Thats kinda-sorta how Ford made the early Bronco work without having structural issues.
Sure they're a little tight offroad when you want extreme articulation...but for a normal 4 wheeler it was one of the best handling setups out there.

The Mercedes "G" wagon and some late model Landcruisers use a 2 link with 2 rubber bushings at the axle mounting on either side for flex and they work very well.

There are ways to make things work. You just need to isolate the problem and design a cure thats simple and durable.

Come on now, really...how hard can THAT be!?!? Hahaha

Hope you have fun with whatever you choose...gonna be one dandy little Hot Rod by the description!!!

 

http://www.directimagehost.com/is.php?i=146549&img=100_0715.JPG

here is mine. I am pondering the same questions.

 

I don't have the exact set up you are suggesting. I have 2 rods with quarter elliptics on the front. A '27 roadster with no-shackle springs which act as the upper locater bar (as in a 4-bar) and an EQUAL LENGTH lower bar. Having the bar and spring equal length allows for correct travel. The other rod is a '27 Lakes Modified with springs with shackles and '35 Ford bones, split and mounted parallel to the frame. Both suspensions work very well. While neither axle it a tube, I would build these same set ups with a tube axle in rods of this weight. I doubt you could measure the twist (deflection) in the front axle in either car unless you used a micrometer.

 

Check the end of page one/beginning of page two of this thread. That exact topic was discussed.

 

Sounds like you've got some serious experience Bob. Awesome.

Would love to see the cars sometime. :thumbup:

 

Here is my setup with shackles being used on a 34' pickup. The rear is being setup the same also.

 

Here is the setup of the rear. Both the front and rear are only mocked up at this point.

 

Looks good on paper but, about 35 to 40 years ago, I was building a 32 and was in the process of putting the ch***is together. I was going to use rear radius rods down the frame sides. I happened to be playing with a piece of welding rod shaped in a U. All sides being about the same length and the corners square. Lay it on the floor. Pick up one of the corners and see what happens. It will also pick up the entire side or rear. It can not just pick up the corner unless you either twist the tube which is not going to happen, or twist the frame.
I used a 4 bar made up of 58 Chev panard rods which eleminated the problem. This was before 4 bars were the rage.
Just try for your self.
Good luck

 

D'oh! Hahaha
Well...it wasn't discussed MUCH! []

 

True, bvut it didn't take much discussion for me to see that it was an obvious upgrade from the heim/clevis' used on most hairpins.

 

I plan to use a double-dip, with hairpins, with the Speedway brackets and bushings posted above. This will be on a '27 Ford modified. I'm not worried at all. The bushings are the key. They are an automotive-style bushing. There is a reason that every car manufactured uses rubber or poly bushings. They flex just enough. They absorb the vibrations and impacts that cause things to break.