Things that are OK to change?

[Mike]

I have a few questions that I think I know the answer to but I want to ask first before starting on a new design. Im working with Rorty's R11 suspension geometry which is being scaled and modified in order to fit my needs. Here are my questions.

First, would there be any issues with narrowing up the suspension mounting points on the chassis? As in making the distance between the front bushing and rear bushing narrower on a A arm. I dont see what this would change other than making more room for cabin area and reducing the strength a little in that area.

Second, The mounting points on the R11 are staggered a little but I dont see how it would change the range of motion so can I make the mounting points in line with each other? The upper front arms are mounted a little in front of the lower arms and I want to move the mounting points (not the whole arm) back to where its centers over the lower arm mounting points. This would allow laser cut brackets that have the upper and lower arm mounting points on them as a unit.

Third, how much scrub radius is needed for a good steering feel? Right now my scrub is setup a about .25" I did not draw up all the parts on the R11 plans so Im not sure what the stock built R11 has.

Forth, Would there be any benefit to adding a little rake to the front suspension and would this be as easy as rotating the front suspension back to the desired rake or does this get into a whole new ballgame? Say I take the whole front suspension unit as a whole and give it about 6deg rake, will that screw up the suspension geometry?

Maybe I made my questions clear and if not ask me what im talking about and I can illustrate what im talking about.

Thanks
Mike

[minibajaman]

I've not looked at the R11 plans before but I think I can help with some of these questions.

Originally Posted by Mike\";p=\&quot

First, would there be any issues with narrowing up the suspension mounting points on the chassis? As in making the distance between the front bushing and rear bushing narrower on a A arm. I dont see what this would change other than making more room for cabin area and reducing the strength a little in that area.

That should be ok, but as you said it won't be quite as strong. *How much narrower are you thinking you want to make them?

Originally Posted by Mike\";p=\&quot

Second, The mounting points on the R11 are staggered a little but I don't see how it would change the range of motion so can I make the mounting points in line with each other? The upper front arms are mounted a little in front of the lower arms and I want to move the mounting points (not the whole arm) back to where its centers over the lower arm mounting points. This would allow laser cut brackets that have the upper and lower arm mounting points on them as a unit.

This will most likely mess up the caster. *I don't think Rorty has provisions to adjust caster, so it relies on the mounting points to be correct. *You could compensate by making the upper a-arm offset so that the upright attachment point is still in the same place, but that requires more redesign.

Originally Posted by Mike\";p=\&quot

Third, how much scrub radius is needed for a good steering feel? Right now my scrub is setup a about .25" I did not draw up all the parts on the R11 plans so Im not sure what the stock built R11 has.

There's no definite answer to this, I think Rorty recommends around 3/4", I have used 1/2"-3/4" before and that seems fine. *I wouldn't go less than 1/4".

Originally Posted by Mike\";p=\&quot

Fourth, Would there be any benefit to adding a little rake to the front suspension and would this be as easy as rotating the front suspension back to the desired rake or does this get into a whole new ballgame? Say I take the whole front suspension unit as a whole and give it about 6deg rake, will that screw up the suspension geometry?

Rake is a debated issue, there are many threads about it. *I like a little bit of rake (up to 10 deg) but I have always used ATV tires under 24" dia. *If you are using 30" all terrain tires than it may not be needed. *It's not as easy as just rotating everything back, once again that would mess with the caster and other angles. *If you are using Solidworks or other 3D cad to redesign this stuff than you could figure out the changes necessary, but if you're using 2D then it would be tough to get correct.

[dunerocket]

I'm assuming the R11 are similar to the R16 for the A-arms. *You can move the mounts to be inline with each other (top to bottom, the R16 has the front mounts in the same plane), just be sure not to change the relationship of the ferules that the rod ends thread into. *That would keep the caster the same. *Does that make sense?

[Mike]

Sounds good. I had an idea on most of these but I just wanted to hear it from others before I designed it. The mounting points need to be narrowed up due to the short wheel base of the side x side and the need for more cabin length. The mounting points will be about 12" end to end and I will only be moving the mounting points not the ferules so the geometry will stay the same. I am using 3d autocad for the design work but I dont know much about suspension design so I will just leave the rake out of it and leave it how Rorty has it designed. Im using a 25" ATV tire so maybe I wont have any problems.

Mike

[Gene]

What does Rorty have to say? I'd start with him!

[Mike]

I have not talked with Bob about changing the pivot points but we have talked about scaling the suspension. I guess to get down to it Im just using his geometry which was drawn as per his plans and then scaled down to 94%. After drawing up the suspension and frame pivot points it looks like there is about 6 deg of caster designed into it. Can anyone confirm this for me. I send Bob an email so maybe he will get back with me and let me know something soon.

Mike