Bob,
Thank you very much for your informed and detailed comments.
No problem, I love working on trucks and vehicles of all kinds....so much it's been a career that is so intense I am STILL far from a "know it all"....LOL.
My goal with this thread and our web site is to leave a trail that others may follow, specifically to learn from our mistakes as complete novices heading into this project.
Very commendable, I am sure many will learn from your site.
I agree that I was under-researched for this project. I believe that a minimum of 24 months would be required for an undetaking of this nature. Due to our last minute switch from a sailboat and our resulting timeline requirements I only had about 90 days from "we need to use a four wheeled land vehicle" to selecting the FG/camper design.
As a sidebar here, it takes most OEM's about 3-4 years to fully design and develop a commercial cab and chassis...no joke. There actually IS that much work to ensure "it" is a safe and economical vehicle that meets the customer's needs. SOmetimes we miss, sometimes we hit the target exactly.
I was unable to identify any qualified resources to perform an engineering analysis of the type you describe before, during or after this project. I would welcome your referral to any resources who are capable of the measurements and calculations you mention and recommend.
I will not recommend myself, as I feel it is unethical for me to solicit business on a hobby board. Therefore, I would recommend using Google search terms " vehicle suspension consulting engineer" which will return the names of many individuals and companies that provide this very service. Some are Mr. Herb Adams in Detroit, Mr. Andre Reynard, and others.
Specifically, I am interested in getting the vehicle on a tilt table so we can accurately determine our ultimate CG/roll angle/whatever the correct engineering term is with the 3 point pivot frame in operation.
Ohio TRC (Transportation Research Center), NATC (Nevada Automotive Test Center), and others all have commercially available test centers for just this type of work. Not cheap, but you would get the same service that the OEMs receive.These centers are quite well versed in this type of analysis, especially NATC (I had a lot of fun there when I was working with the military vehicles for AMGeneral).
As a sidebar to this, if you are looking to determine what the amount of frame twist is in the FG, you should ask about a wave course test-this is a test where the vehicle is driven over a series of concrete half cones in the roadway that are 3' tall at the outside edge opposite the next cone. The purpose of this is to make the axles and suspension travel to the jounce (upper travel limit) and rebound positions opposite at each end of the vehicle. In other words, the left front tire would move to it's lowest position in travel, the right front would be in it's highest position, the left rear tire would be in it's lowest position, and finally, the right rear tire would be in it's highest position. What this twist does is to maximize the amount of travel the frame flex and suspension is capable of, without turning the vehicle over (ideally, if the design is correct, the body will be perfectly level in this position). If the body is not level in this test, you can see directly where the "binding up" of the vehicle is occuring.
During our tests we had the vehicle reviewed, including test driving off road, by an experienced expedition vehicle consultant, who has extensive experience in the design and implementation of current market vehicles. I encourage this step as a minimal process for those doing custom builds. We made several design changes based on our consultant's input, all of which dramatically improved our vehicle's on- and off-road handling characteristics.
I applaud your efforts to shine some light of knowledge and experience into this area. Those of us who are forced to, through lack of available market offerings, or choose to create our own vehicles of this type could profit greatly from knowing more about the parameters you describe.
Thanks for the kind words, but remember that even with 30 years of doing this job, I STILL do not know everything. That is why I can design and predict in a computer (experience tells me what is generally valid) BUT testing is ALWAYS required to verify what I thought would work, actually does.
In our project we attempted to keep as much mass as we could as low as possible and located between the frame rails if possible. The execptions to this design goal, which will be typical systems in projects such as this, include the diesel genset and two of the house batteries.
We were also limited by the factory camper we ended up with, as we lacked the opportunity of optimally locating systems for a lower center of gravity, etc. that those who build a custom camper box are afforded.
Thanks again for your input. I believe your comments to be valid and continued input of this type can only serve to make future projects better engineered.
Doug
