Mezzanine concept

[troysladeck]

Starting to get into more technical / precise suspension design on my builds and want to start learning cad that way I can design my own parts and send them to get cut. Whats a good entry level program that works best for modeling suspension and steering design? Being able to cycle the parts and plot the data (motion ratios, bumpsteer, caster change) would be awesome. Don't mind paying for a program if its worth it.

Also how much would a 3d scanner cost? Are there tools available for a hobbyist? If so are there certain CAD programs that work better with 3d scanning?

SECONDLY...

The main reason I want to learn CAD is because I want to start designing a mezzanine 4 link setup for my Cherokee. It seems to be the best way to keep the back seats completely in tact, keep the fuel tank in the stock location, and also run a tradiitonal coilover / bypass setup. And since I don't mind putting the shocks into the trunk I think it will work great.

I could do a typical mezzanine with a hard mounted pivot near the bumper, but I've thought up an interesting idea that seems a lot easier and utilizes parts of the leaf spring suspension that I've already upgraded.

Here my proof of concept:

So typical mezzanine setups have the hard pivot in the back and a connecting rod on the axle. This is essentially the same thing but flipped. The trailing arm that houses the shocks connects directly to the axle, then the shackle in the rear is what allows for movement. My shackle box is already reinforced and bolts through the floor (perfect spot to land a cage pillar) and also is tied into the unibody rails and stiffeners. Its beefy and strong. The direction of force would change (compression -> tension shackle) but I think it would still work fine

Its hard to visualize how it would cycle since both sides of the shock arm pivot locations will change. So I would love to model it in CAD and see if it would work. Is it worth investigating? Or should I just plan on doing a typical style mezzanine with the hard pivot in the rear?

Thanks!

 

[gascapkevin]

Back in my college days I remember the suspension guys on the formula SAE team would do their simulation stuff on Solidworks but it would take awhile to load. I believe @the bodj has mentioned scanning parts and using fusion in some of his posts, and I think @Pictafiedesign does this kind of stuff as well. Maybe they can chime in with words of wisdom.

It would seem as though you have stumped the suspension wizards with this design. I think you should try it out... or you could just finish converting your XJ to an explorer and do a spring under setup

 

[the bodj]

I'm all for learning, but what you're wanting to do is advanced CAD work. Get the free version of Fusion or get Solidworks for Makers (it's pretty cheap annually), and start messing around with it. Honestly, it's hard to jump right in with 3D scanning and 3D design/assemblies. I'm not trying to discourage you, but rather help you save money until you feel you're ready to jump to a scanner and expensive paid subscription CAD software. I rarely use my scanner, unless I'm forcing myself for practice. It's so much faster and easier right now for me to make RAM board templates, draw in SW, and plasma cut out.

 

[troysladeck]

@the bodj thanks for your input dude that makes total sense. I'll stick with learning cad for now and just take measurements, then draw by hand.

I have an iMac so kind of limited on options. I ended up trying out Onshape. Nice thing is its web based so I can use it at work and at home. I made some rudimentary drawings just to get a feel what it would look like. Tomorrow I'm going to take measurements of the jeep and make it even more realistic. One thing I didn't think about is how the shackle/arm combo could be limiting the amount of droop. In the first pic you can see how the shackle is close to inverting, but I'll see if it matters with real measurements. Other than that it looks like it could work.

 

[troysladeck]

Alrighty here’s it cycling with real numbers. Obviously don’t have the 4 link mounts on the chassis yet but I based them on a 48” lower link.

12” coilover, 14” bypass
Can cycle a clean 18”

How’s it look?
Anyone see a reason why this wouldn’t work?
View attachment IMG_8396-compressed.mov

 

[troysladeck]

Ride height


Full droop 18" travel


Full compression. Shock angles set up so the spring rate is rising the entire time

 

[NODNARB]

What’s going to happen to the axle end of the mezzanine arm on articulation?

 

[troysladeck]

What’s going to happen to the axle end of the mezzanine arm on articulation?

When you say articulation, are you talking about like flexing out on a rock, or normal up and down movement? Either way I think heim joints on both ends of the mezzanine arm should provide enough side to side movement if there is any

 

[NODNARB]

Yes when the axle is not parallel to the rest of the truck. I found out the hard way you need long “Tierods” connecting the axle to mezzanine arm to allow for both angle change and side to side movement because when the axle is no longer parallel to the chassis, the mounts get closer to the center of the truck.

 

[troysladeck]

Yes when the axle is not parallel to the rest of the truck. I found out the hard way you need long “Tierods” connecting the axle to mezzanine arm to allow for both angle change and side to side movement because when the axle is no longer parallel to the chassis, the mounts get closer to the center of the truck.

Gotcha good point. That’s something I’ll have to look into. I have no idea how to model that in CAD yet haha. If I give myself plenty of clearance from the unibody then I should be good though

 

[Motiracer38]

I was wondering about the articulation effects as well. My cantilever has fairly short links and I haven't found a drawback yet.
When you say rising rate are you calculating wheel travel vs shock travel or just eyeballing 90 degrees? Might want. To plot it out in case it does something weird.

 

[troysladeck]

I was wondering about the articulation effects as well. My cantilever has fairly short links and I haven't found a drawback yet.
When you say rising rate are you calculating wheel travel vs shock travel or just eyeballing 90 degrees? Might want. To plot it out in case it does something weird.

Good to know. Shock is exactly 90 degrees of the arm at full bump, i figured that is what determined the rising or falling of a spring rate. But... there is some forward/ back movement of the shackle that could definitely be altering the spring force. So once i figure out an efficient, practical way to gather that data and plot it, I definitely will!

 

[Motiracer38]

It'll get a little funky with the shock angle but may not be far off. If you look at my Sequoia build thread I have the motion ratio mapped of a seemingly simple cantilever and there were a few surprises affecting the rate.

 

[Giant Geoff]

I would say, raise everything up into the bed area, reverse the shackle to a basic rod on the axle side and it will clear through the body with less to seal up later.

 

[troysladeck]

I would say, raise everything up into the bed area, reverse the shackle to a basic rod on the axle side and it will clear through the body with less to seal up later.

I really like the idea of using my shackle boxes if possible. They’re from ruffstuff and mate perfectly with the frame stiffeners. also have to consider my fuel filler hoses and fiberglass fenders that aren’t removable. So I think i have to keep the arm below the cab because of those aspects. But I could definitely do a traditional mezzanine with the fixed pivot in the back near the bumper if the whole shackle idea doesn’t pan out