Thread: Articulation

Well, It was going to happen sooner or later, and I couldn't resist the temptation to pull the pin on the wristed radius arm and go looking for trouble. I was lying under the hybrid looking at the arm, trying to visualise the forces,whether torque or gravity induced that would cause the suspension to unload on steep up or downhill off cambers,that could be blamed on the wristed arm and not the lack of roll resistance associated with any type of flexy suspension design. I came up blank.
Now, my property has lots of steep offcambers leading into gulleys and dry water courses, and i have higher than reasonable expectations of what a vehicle should be able to do. I tried everything I could think of to catch it out but failed. I ended up driving along a water course with 45degree banks on both sides and turning sharply right to obliquely climb the bank at an ugly angle until I reached the tipover point at full articulation.Nothing silly happened, so I selected reverse gear and attempted to move.That was when it wanted to tip over, so with the winch of my other vehicle, I pulled the chassis over so that the wrist pin holes lined up, refitted the pin, backed off the winch and noticed the chassis sitting a few degrees more level.I tried reversing again. Same thing happened, propshaft torque wanted to tip it over on the left side. Forward gear, propshaft torque pushes the chassis into the slope. On the Pirate link Serge posted, Sam spoke of the vehicle wanting to fall over when attempting to reverse off an obstacle that he thought he was going to tip over on when driving forward. Based on the results of my fun and games today, IMO it was because the extra articulation allowed the vehicle to obliquely climb the bank until he reached the tip over point.Regardless of the radius arm arrangement, when a vehicle is leaning to the left at the point of overbalancing, then reverse gear propshaft torque will tip it over.

As a funny aside. I tried the same trick with my portalled Landy a bit further along the gully where the bank was a bit steeper and higher because she has a wider wheel track and longer stroke dampers. Unbeknown to me the hose clamps holding the left front spring in place had broken, allowing the spring to fall out on the ground when the left wheel drooped to maximum articulation. All was going well until the left front wheel started climbing the bank, at which point the chassis would lean on the spring.But there was no spring to lean on,so the chassis kept leaning over, until much to my surprise she fell heavily on her side. When I pulled her back on her wheels with the hybrid and refitted the spring and backed off the winch rope, there was no way that I could tip her over by hand again even using the open door as a lever.
My conclusion is that anything we do to gain better front articulation will by necessity reduce roll resistance, and I'm not so certain that the wristed arm is any worse than a 3link, one link or torque tube in that regard.
Wagoo.

Originally Posted by SuperMono

Wagoo, I have just realised who you are

No wonder you know what you are talking about.

Regards
Stephen
LROCV 709

No Stephen,I'm afraid you are mistaken.I'm not the Messiah. I'm just a very naughty boy. According to my wife anyway.
wagoo.