hey im building a fully home built boattail roadster. im building it as a guy would have back in the 40s. it has some cool "concept" features on it that i would like to carry onto the front suspension. i have a straight front axle that i was thinking about cutting in half then mounting the center to a plate on the bottom of the frame with two large bolts. seems pretty simple.. so im guessing im wrong. so ANY thoughts, comments, ideas, or concerns would be very appreciated.
The Allards of the 40's and 50's used this type of front suspension. The problem that arises is the large camber variation that occurs due to the arc created by the travel of the stub axle. A stout anti-roll bar would be in order to keep it civilized.
You're better off with the regular straight axle, there are suspension issues that can't be overcome... I'd say spend the time and money on other parts of the build.
**Edit** I have no idea what happened to my images! Grrrr! They just disappeared. They were here when I posted this! I'll look in the couch cusions and in the frig. In the mean time, here's a bunch of words... When you're going around a corner, short axles causes the tires to fold under the car - as seen on the rear end of this triumph. When the tires tilt, you're only using the edges of them instead of their entire width - so you get less traction. Also, it raises the vehicle in the air which causes it to roll more in a corner. With a longer solid axle, the forces which cause the tire to fold under are still there, but now the car's weight has a longer lever to counter act it. The road has a short lever - the tire. The car has a long lever - the axle. So if you cut the car's lever in half to make independant front suspension (IFS) then the road will be able to push the tire under and raise the car in the air because both levers will be about the same length. If you want IFS, a better way to go about it is to use two levers on the tire so it will go straight up and down instead of folding under. http://www.carbibles.com/images/coilspring1.jpg http://www.carbibles.com/thumbnails/coilspring1.jpg Or, if you love the single axle look but want IFS, you could do like they did on Ford F150 trucks and run long axles from the opposite sides of the frame to your wheels. http://www.carbibles.com/images/twinibeamsuspension.jpg http://www.carbibles.com/thumbnails/twinibeamsuspension.jpg If you're stuck on the idea of cutting the axle in half, you can install a "Z" bar that will help counteract the effects of the short axle. They used them a lot on the rear suspensions of some race cars made from VW's. I prefer the simple straight front axle that runs all the way across the vehicle. Although it has it's drawbacks, I like the looks, simplicity, rugidness and "antique traditionalness" of it. There's lots of good websites that explain suspension basics better than I can. There's also some pretty good books made for us non-engineers. I can't remember the name of the one I was going to suggest. If I do, I'll edit this response to include it. Good luck with the project!
Hmmmm... This sounds like a Ford twin-I beam axle. While it has its limitations Ford has used them in F-series trucks and Rangers for decades. While it isn't exactly a beam axle that it is split, it is a little of both ideas.
Fatmann fabrication used to do a kit for this, here's the link to the installation article. http://www.webrodder.com/article.php?AID=283&SID=16&CID=11
and it sucked.... it has been discussed numerous times here... http://www.jalopyjournal.com/forum/showthread.php?t=222743
Morgan's sliding pillar suspension should give you an independent beam axle front end and be period correct. Basically the axle stays fixed and the kingpins are sprung, giving you live hubs I think Lancia had a variation on this on the Aurelia (top pic). Did some playing around with this idea for a hot rod thirty years ago.... Here are a couple of links: <cite>www.[B]morgan[/B]ownersclub.com.au/.../<wbr>OF%20SLIDING%20PILLARS%20AND%20AXLES.pdf</cite> - http://en.wikipedia.org/wiki/Sliding_pillar
I would think (if you just must do it) Cut the ends off 2 axles and pivot them on the opposing sides like ford did on stock pickups. This I believe would make for less camber change over bumps than splitting one in the center.
Z man is correct here. The concept is a fair concept but you really want to use two axles and make them cross each other in the middle. The longer the arc the less noticeable the problem. But the problem never goes away. On a car that only sees going around in a circle to the left the problem can be basically overcome by over correcting but you still have the problem and just have to adjust your driving style to compensate. Anyway not the best idea you had today. Listen to Z man he has the proper solution for it.
Here's a shot of the sliding pillar front suspension on a Lancia Appia.... [FONT=verdana, arial][FONT=verdana, arial][FONT=verdana, arial][FONT=verdana, arial][/FONT][/FONT][/FONT][/FONT]
Flaming River has this system that's closer to the old Ford Twin I-Beam set up. http://www.flamingriver.com/index.php/products/c0007/s0015/FR40010 Less drastic changes than the Allard but still lots of of issues I'd imagine.
Colin Chapman used twin I beams on his first Lotus, the MK6. Probably the best way to deal with the jacking effect of swing axles is to use a 'zero roll' setup like the Formula Vee guys use. Wouldn't look much like something they would have built in the 40s though.
I think that we are actually missing a minor point here, anything with king pins is not considered indepent suspension. I just wanted to say that. carry on.
How well can a straight axle be made to handle ? I have all of the normal things on my 56 F100 ,but I am curious about other cars. I think my next project will be a Model A with a axle but I would like great handling.
depends on who builds your suspension and if you are compairing it to a Lamborgini as being a good handling car or a model A as being a good handling car. They handle fine, they are probably not going to compete with a new rice grinder in an auto-cross but they handle fine for what they are.
I think that we are actually missing a minor point here, anything with king pins is not considered indepent suspension. Old VW Bugs had independent front suspension with king pins. About pre '62 or so. I'm just sayin'.
Mr Beaner.... lots of cars had kingpins and independant suspensions. 1949 - 1954 Chevrolets for one. I'm going to make a guess and say anything with independant front suspensions built before say 1952 had kingpins. could be wrong on that .... but not as wrong as PNB
A beam axle is what it is. There's a reason they haven't been used on passenger cars in 50+ years and Rodger Penske doesn't have them on his Indy cars. Some of the disadvantages are: high unsprung weight, inherent high roll center, lack of independent camber gain and lack of convinent camber adjustment. These can be overcome somewhat by different means, it just depends on how far from "traditional" you want to stray. In the end, when all is said and done, you would probably be money,time, and effort ahead just going IFS.
Check out the front suspension on Allards, Designed by Leslie Bellamy in effect a beam axle cut in two and mounted centrally http://www.thoroughbred-cars.com/cars/UK/allard/Allard%20history.htm Apparently there conversions similar to this were available in the UK in the 50's and 60's to special builders (the next best thing to hot rodders) based on the Ford Pop and Anglias. I have seen adverts for these but I couldn't find anything with a quick search, I may try again later.
I think that Limey Steve has restored an Allard for a customer there was a thread on here, that may help.
Swingaxles on the rear of a car are different from swingaxles on the front. The reason the roll center on a VW ( and others like it ) in the rear is so high, is because the axles needed to line up with the diff. Having the roll center that high with short swing axles gives the jacking effect. And then a unexperienced driver notices that, and gets off the throttle mid corner, it transfers the weight from the rear axle to the front. Unloading the rear suspension, possibly tucking the outside rear wheel under, which can lead to boring little books like the one written my one R.Nader. The rollcenter on the front can be chosen a lot lower, and the pivot points can be offset to lengthen the swingarms. Which will both improve the swing axle IFS setup. The Allards and the twin Ibeam Ford trucks always come up in these discussions, but that is not a good comparison either. Allard used this setup pretty early ( twin Ibeam IFS' have been made to work a lot better since then), and the Ford Trucks are a tall vehicle making it a different kind of animal too. I own a British built racecar, a mid '60s Mallock U2 Mk6. These cars were able to run and compete with the top of the line rear/mid engined single seater cars of their day. ( Formula Ford, Formula Junior, Formula 2, etc) I also own a Ford Truck with twin I beams ( a F250 SuperDuty) Its not even close to the same thing. Modern double A-arm suspensions are still calculated in swing arm length( or they were in the books I own ). The pivot point on those is not an acctual mounting point but something to calculate with. And for the longer swing arm lengths, outside of the acctual car. Knowing what I've learned from my Mallock, I would not hesitate to build a Swing Axle IFS setup for a Trad looking handling Hot Rod... For what its worth, A non IFS Ibeam front suspension can be made to work very well too...
Some more cool Info.... Colin Chapman used twin Ibeam IFS on cars like his MK6, which were short and tucked under like the Allard. But also on his later and super succesful Lotus Eleven. ( Offset pivot points, and low rollcenter) The Eleven got replaced in time by the Lotus Seventeen. It had McPherson IFS which did not work at all, and the Seventeen did not have the succes the Eleven had. ( the struts were too short which was needed because of the low slung bodywork, which made them bind ) That doesnt make McPherson struts bad either. Most small economy cars sold today have them...
True, and yes the geometry on the front can be configured in many ways. but I was refering more to the Allard/Lotus setup which isn't that much different than VW rear geometry. I think both could benefit from a zero roll suspension.
McPherson struts would seem to limit Camber gain just as much as a solid front axle! Why do the modern cars that use them still seem to handle extremely well in spite of that, and can the same tweeks they use be transfered over to help a solid axle car? I always found it interesting a design that, in many ways, goes against commonly accepted handling geometry, still seems to handle just as good as an SLA setup when put to the test.
You get the camber gain on a McPherson with the length and angle of the lower control arm. Manufactures like them because they are cheap to produce and work well. I mentioned the Lotus Seventeen because everybody has seen a McPherson, and knows what it does. But it did not work as good as the swing axle setup it replaced. Same goes for the Mallock U2 Mk6 and the Mallock U2 Mk7. Arthur Mallock told me his Mk7 did not handle as well as the Mk6 ( he had replaced the swingaxles of the Mk6 with double A-arms on the Mk7) So that means that it has happened twice, where the swing arm IFS out performed the more modern setup that replaced it. And these were not backyard builders that were fumbling around. They were well known racecar constructors at the top of their game....
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