×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Balanced suspension design

Balanced suspension design

Balanced suspension design

(OP)
I am a member of the Purdue Mini-baja team and I recently began working on our suspension setup for the coming year.  I was looking through Carroll Smith’s latest book, Racing chassis and suspension design and found a very interesting paper from Erik Zapetal SAE # 2000-01-3572
This design allows the four suspension modes to be independently varied and I believe this would be very useful for an off road vehicle such as ours.  I am currently thinking about using a damper at each wheel hydraulically connected to four other pistons on the balance plate similar to what is shown here.

http://www.uspto.gov/web/patents/patog/week10/OG/html/1280-2/US06702265-20040309.html

I am hoping that such a design would decrease the weight compared to our current coil over shocks that each use two large springs stacked on top of each other.
Our mini-baja vehicles typically weigh about 450lbs and have about 12” of suspension travel using fully independent A-arm suspension.  WE are also limited to 10 horsepower.

So I am looking for a more experienced persons thoughts on such a design or any additional information you may have about this system.  I think this system would work well but I’m afraid it might end up being either to heavy, complicated, or expensive when compared to coil overs.

Here is a link I have found that is also related to the topic.
http://members.cox.net/rseike/nowarp/

Thank you for your help
Eric Eveslage

RE: Balanced suspension design

Great stuff. Don't worry about patents, you can't get into trouble if it is a one-off for non-commercial applications.

What sort of modelling software do you have? Could you build a full dynamic model and simulate its performance over 'typical' events?

I have a hard job believing that a 10 hp 220 kg machine with such short wheelbase and narrowish track needs to worry about warp, but then I don't know what you expect to be able to do, and how refined current designs are.

As a practical observation KISS has a lot going for it in off road applications.

Cheers

Greg Locock

RE: Balanced suspension design

(OP)
We use Adams for modeling.  I am going to try to build a full model this year even if it only helps the next year’s team.  Unfortunately I don’t know a whole lot about Adams because the people that learned it previous years graduate without passing much down.

A rock crawling event was added two years ago and all the teams struggle with it.  Our solution last year was to use four-wheel drive.  4wd added about 50 pounds and 8” to the length though.  So I am hoping to get better articulation with the balanced suspension and get rid of the 4wd.

A month ago my plan was to just keep a similar setup but refine suspension points and find better shocks.  Some of the other guys wanted to use inboard suspension but I don’t see any real advantages to it.

I think your last line pretty well sums it up.

Thanks
Eric

RE: Balanced suspension design

4wd is very hard to beat in that sort of application.

If you are using ADAMS/View it should be easy to design your complex spring system from scratch. If you are using Car then it might be rather difficult, as you'll need to modify the template.

If you are using View look at the example for cable controls - it includes a god summary of how to write equation based linkages, which will be easier than modelling the linkage piece by piece.

http://support.adams.com/kb/faq.asp?ID=kb9364.dasp


Cheers

Greg Locock

RE: Balanced suspension design

Wonderful news! I have played with a similar system, so far only at 1/10th scale on a radio controlled model, and with mechanical linkages. I started on the basis that a rock crawler needs to maintain as close as possible to equal load on all four wheels. My model has no spring element at all, and simply allows free warp between the axles. There is no way to overcome load transfer resulting from body angle (i.e. CG shift), but it does prevent load changes due to spring rates. The system allows the use of open diffs at all times. The model has the ability to allow the axles to articulate until they are at almost 90° to one another, giving some impressive obstacle crawling. The scary thing is what happens when you try to manouvre the vehicle at high speeds. It effectively has four 'roll centre' axes forming a diamond shape in plan view. Hrad cornering can cause it to lift an inside front wheel, whereupon it continues to corner, but as a tricycle with the front axle stood on end! Needs some refinement!

RE: Balanced suspension design

Kudos to all thinking outside of the box

RE: Balanced suspension design

Zapetal has an interesting idea here, and I can see the use in something that is for off-road use.  His initial paper was for a road race car, though.  After reading the paper and listening to his presentation, I could only think one thing.  How the hell are you supposed to tune the roll couple distribution on the damn thing?  For it's originally intended use, it's completely useless.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close