pull/pushrod suspension

[gt1guy]

What I meant by the 45* angle was that you want to get that pushrod as close to vertical as you can. I would say that 45* would be the min, anything closer to 90*(straight up and down) would be better. Hope this clears it up.

I've seen link set ups like your building before. But, the distance between the ends of the forked side were always much, much greater. Some have the forked link on top, most have it on the bottom. Basically what your building is a modified version of a Satchell link suspension. And as such, the third link NEEDS to be as wide as possible, the forked legs of said link NEED to be a as close to a 45* angle in plan view as you can get them. Nature likes triangles. This is really not an option, the forces that that link will see are very high to say the least. I can't stress this point enough. Instead of thinking of it in terms of it keeping the rear end under the car, think of it as it has to keep the entire car over the rear end. That's the kind of forces were talking about here. Having the forked side only as wide as the 3rd member won't do it.

Here's a couple pic to show you what I'm talking about:

This is what your building. But like I said, it has the forked link on the bottom,as most do. Notice how wide it is, almost the width of the rear end.




Now hear is JAGs true Satchell link. Again, notice the spread in the lower links. It's no accident that they truly look the same. It's also no accident that they are at 45* angles.



Hope this helps to shead some light onto the point I'm trying to make.

Kevin

[greencactus3]

thanks for the input. ill see what i can do to modify the design to follow your tips better

[Beige]

Beige,
i also have thought about that, but from the pictures of the F1 cars i have looked at, it would seem that they (although they do use much better materials than i will be) have pushrod angles that would seem non ideal. the forces on the pushrod/bellcrank just get higher with a bad angle correct?

It's not only adding stress to the pushrod/bellcrank. The forces are transmitted through most of the rear suspension and the axle. Plus you need stiffer springs since most of the force is misdirected, and that adds even more stress to everything.

Since gt1guy pointed it out. Your 3 link is common for minitrucks, and while I have confidence in some of the places that make them (but none in others), they're intended for bagged cruisers.
While It would probably work, I doubt it's ideal, and I cringe at using differential cover bolts to hold the wishbone mount to the axle, and that's without the high loading that performance driving adds.

[796spdbu]

Greencactus,
I was typing to fast.I am a member over at Sy/ty.net....Sorry
I'll post some pics when I get home tonight.

A friend of mine has a radio controlled 4x4 truck that has a push rod suspension front and rear. At easter i was checking out how it worked and wondered if it would work in a custom tube frame.

I have been to a few indy car races at KY. speedway and have taking notice of how there suspensions worked.

Hope you can figure it out!

[greencactus3]

stress i do see being an issue. i will try to redesign the angles
my wishbone will be at the minimum, safe to use, although its possible it may deflect more than optimal. the link bars and wishbone are the SD beefy ones, so i have no worry about the bars themselves bending. more the bracketry, like the diff cover bolts as mentioned would be the weak spots.
i chose to use SD parts because of budget issues more than anything, and if all else fails, i can make new parts.