Dick, if my understanding of what you're saying is correct, then you're saying the axle rotates around the rear mounting points of the radius rods. That would be true. But, and this is the big but, one radius rod is trying to rotate the axle clockwise while the other is trying to rotate it counterclockwise. The result is a torque applied to the section of the axle between the radius rod mounting points. Think about how a sway bar works on a current vehicle. The central part of the bar is mounted to the frame. Analogous to the axle in our discussion. And the ends are bent roughly 90* and mounted to the lower control arms. The bent ends and their mounts are analogous to split wishbones or hairpins. In roll, one side of the frame moves up while the other side moves down, and the sway bar develops force to resist the roll forces by twisting because its ends are moving in opposite directions. The same thing happens with radius rods and a straight axle, regardless of whether the axle is a beam or a tube. The difference is that a beam cross section is weak in torsion, so it doesn't take a lot of force to twist it, while a round tube is the stiffest of all common sections in torsion and it takes very high forces to twist it. In straight jounce and rebound, such as going over a speed breaker or thru a dip in the road, neither the sway bar nor the tube axle will be subjected to any twisting motion, and in that case the tube axle will, as you say, simply move in a path described by a circle around the center of the rear mount points of the radius rods or hairpins.
Yep, and big old tubes that ain't gonna twist much at all regardless of what sort of forces you throw at them. And that's why the geometry of a 4 link rear suspension has to be designed to avoid trying to twist the axle housing. It won't give, so the result of poorly designed geometry is suspension bind and ultimately breakage of the links or mount brackets. Some front wheel drive cars with solid rear axles get around the problem of torsional stiffness by using a channel shaped axle beam formed from light gage steel. They'll twist like a noodle, and the purpose is to decouple the left and right side as much as possible to emulate independent suspension while maintaining the simplicity and lower cost of a straight axle.
YUP YUP YUP, entirely correct. Mr. Spadaro seems to have lost sight of the fact that the axle stays parallel to the ground while the chassis rolls relative to the ground and the axle. The angle between the chassis and the axle changes. If you draw a line side to side through the front radius rod mounts, and another through the rear radius rod mounts, the lines are parallel at rest or during simple up-down travel, and at an angle to each other during chassis roll. This requires the axle to twist, or the radius rods to bend. Or, something breaks... I don't know how many more ways we can explain this.
You(not meaning YOU personally) cant say that if a front axle doesnt twist it will try and tear/bend/destroy all the other componants,,,, and then turn around and say rear ends are ok because the tubes wont twist.
scrap metal 48, the Super Bell axle from Jim Ewing went hand in hand with Pete and Jake's 4-bar creation. They didn't create it, but were the first to market it and profit from it. That tube axle does not twist at all, but floated in one plane with no strain on bat wings, brackets, or tubes. Just my .03 cents.
The Chemical City coupe and all other similarly-equipped front ends are fighting with physics. These T-buckets you are talking about with these setups are like most T-buckets, very seldom driven.
scrap metal 48, when a tube axle, especially a Super Bell, is tied to split 'bones or hairpins, the welds on the brackets are going to be taxed much more than they would if attached to an I-beam, period. (Please don't call me OBAMA because I said period.
He did not say that. Go back and read it again. All the while I was following this thread I kept thinking, all this has been argued regarding split bones on rear ends, and that is where breakage and bending have been common for some time. Some of the problem on rear ends was due to axle torque applied to inadequate strength rear bones, but as much or more has had to do with exactly what is being discussed in this thread.
I knew as soon as I hit the post key that this would be an issue but installed correctly the axle does not twist. The case has been deemed in roll angle, that the roll of the chassis places a torsional force to cause the axle to twist. No, not on the axle, the twist is 90* to the axle so as the chassis is in roll the torque of the roll is placed upon the wishbone arm component, the same would be true with a 4 bar or hair pin set up. The axle doesnt twist the linkage does. It can also be looked at from a mass stand point which is going to twist first a 2" diameter 1/4" wall tube or a 2" diameter 1/8" wall wishbone. The key is to try and eliminate as much torsional component as possible by the use of an adequately sized ball end on the chassis side. The use of a straight plastic or urethane bushing at the chassis linkage reduces the rotational angle of operation and should be avoided because if its limited rotational range. Disadvantage of bushing use is when the (Y)angle of rotation meets the bushing compliance the fight begins as to which part is tougher the axle or the wishbone arm thus the weakest twists first. Based upon length of the wishbone lever arm it could be the axle but this also means that the suspension is all bound up.
I've often thought about putting a rubber bushing in ONE side where the bone met the axle. Or use bushings from a late model strut rod at the frame end of the bones.
uuuhhh.......you can't say " 'you', not you personally", and then argue that his statement is contradictory......who is "you" if not "him"? Well, of course, you CAN say that...obviously, you did, but it seems to be a disclaimer that doesn't do it's job very well, IMO, of course.
by the time i got the reversed spring, 4" lowered tube axle in my 1939 Deluxe coupe, there is only 2or 3 inchess of travel in the front suspesion before it hits the frame. what the heck is everyone arguing about?? just as well clamp the front axle to the frame and be done with it!! Hell, those weak old frame twist more than any axle, plus, if anything was unsafe, they wouldn't sell it, would they?? Use what you got., the heck with theroies.
I have seen vehicles with hair pins and tube axles. I also saw one this last weekend that had broken a perch bolt and was jacked up. I would not consider that to be safe either end unless the vehicle was setting still and not driven. An alternative would be to use one substantial hair pin or radius rod mounted so that the axle could not rotate from braking or in the case of rear axle, resist rotational force from power. On the other side, use a bearing on the axle that the bat wing would pivot allowing that bat wing to hold the axle in position for and aft, but not be held from rotation. The downside for this would be the appearance because of size necessary the conceal the bearing.
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