wanted: physics expert/mech engineer.

[cri_ag]

ive been doing some thinking about the radius rod in my sprinter, im keen to replace the stock bush type joint, with a spherical bearing, but in order to select and design the joint i need to know how much load goes through the radius rod - chasis joint. i figured the braking loads would be the highest but can anyone put a rough figure on it?

[fbc100]

Im not a physics expert but cusco make a setup that does exactly what u want aslong as you leave the LCA bush as just that and not rosejointed

[SillyCarS]

Draw us a diagram.

Change title to wanted mech eng or old corollas will derive the universe for u

[cri_ag]

ya im aware of the cusco setup, just think i have a neater way of doing it, retaining more factory parts. also the lca is on borrowed time as well, its not liking the angle its being pulled into by the amout of castor im running.

ill try n ms paint somthing up when i get back to my pc, and not iphone. title change noted!

[jb_22]

Hi,

Shock loads would be higher than braking loads - i.e. hitting a pothole or a gutter. You'd probably be best to design against the strength of the actual radius rod, not by estimating loads that might go through it - that way your spherical bearing is not going to be a weak point. Also, estimating loading is a very tedious exercise and you want to avoid it as much as possible when designing... well, anything.

The radius rod is what, ~12mm solid bar (6mm radius)? Assuming the radius rod is some sort of carbon steel, the yield strength is at minimum ~300 MPa (the grade of steel used in suspension components is most likely higher than this, but it is better to underestimate). The load that the radius rod can withstand is then simply: Pressure * Area = 34kN. This is about 3.5 metric tons - so you should choose a spherical bearing capable of supporting at least 3.5 tons to ensure it is not going to be a weak point in the suspension design. If you want to be more accurate, you could find out what grade steel was used in the suspension components of Japanese cars of the same era and get an exact yield strength.

Also, I used the yield strength of the steel - this is the stress that will cause the radius rod to plastically deform (i.e. bend, not break) so in a theoretical failure situation, the rod could bend and stretch out of shape, and the rose-joint fracture completely before the radius rod fractures. Something to keep in mind, but I'm willing to bet if you have that sort of accident you won't be reusing any suspension components

Cheers, JB

[cri_ag]

cheers mate thats a much beter way of thinking about it. lateral thinking ftw! i will double check the size of the bar ect but your estimations im sure will be close.

[jb_22]

Hi,

A big part of being an engineer is lateral thinking. I just realised my little "better to underestimate" clause is not applicable to this situation. It would be better to overestimate the strength of the radius rod because we need to choose a rose-joint that is stronger & therefore not going to fail first. Just double checked my textbook & most common carbon steels are ~280-340 MPa, giving a maximum load before yielding over 4 tons.

A side note: In the bush & radius rod design, a high percentage of the energy from shock loading is absorbed by the compliant bush. A rose-joint will transfer this shock energy directly to the chassis. So you could potentially wreak havok on your chassis by using a rose-joint.

Cheers, JB

[punkture]

jb_22 mechanical design practice can suck my wang haha i hated that subject, did teach us how to design an engine however =p id agree on the shock loads, but to determine the radius i would have considered the equilibrium and used the cross sectional area? that way theres no material assumption

[Supra967]

Without knowing the setup you want can't you just use the same size as the cusco one?

[MWP]

T3 make them as well:
http://www.technotoytuning.com/productdetail.php?p=665

I have a set at home, i could measure up the rod end if that would help?

[roadsailing]

T3 make them as well:
http://www.technotoytuning.com/productdetail.php?p=665

I have a set at home, i could measure up the rod end if that would help?

I've never understood why they do them like that, what on earth could be the benefit of bolting it where the bush used to be, then having the rose joint some distance away from that, when they could just make a new mount that bolts to the frame of the car? I think Cusco ones do that but they would be more expensive of course.

more like this

[takai]

You hit it on the head there. Cost.
Plus the caster change as the radius rod moves in its arc isnt as huge as say camber change.

[roadsailing]

Plus the caster change as the radius rod moves in its arc isnt as huge as say camber change.

well with the shorter arms you will gain more caster in bump, weather this is a good thing or not I am unsure, but when I don't understand something I leave it as Toyota kinda intended it I guess.

the standard radius rod chassis mounts look so puny they need replacing anyway.

[MWP]

More caster in bump would equal more bump steer wouldnt it?
The hub moves forward which throws off the hub/tierod alignment.

[roadsailing]

More caster in bump would equal more bump steer wouldnt it?
The hub moves forward which throws off the hub/tierod alignment.

could do, it would tend to cause bump "understeer" in a rear rack car, which would exaggerate the problem as I imagine cars already have bump "understeer" designed in (if they had to choose its unlikely they would chose "oversteer")