hinged chassis idea

[dbrad]

I had an idea to make a comp crawler style, TVP chassis that hinged to allow either axle to move and extra few inches without that movement contirbuting to the axle's articulation. This would allow a belly draggin, low profile rig to creep over some rocks that require massive clearance and then settle back into fully compressed mode for some low COG cruising.

I had in mind, using droop shocks for both the upper and lower shocks but I guess it would work with sprung shocks in the lower position.

I also figured an MOA setup would be preferable to shaft driven as the shafts would limit the angle that the axle can rotate relative to the chassis (and ultimately the transmission).

Another variation could be only one upper shock and only one (or two) pivot in the chassis.


Basic concept layout.





Showing movement of the upper and lower shocks.





Full droop.




I'd like to hear some of your thoughts?

[adamargue]

that looks sweet

[shadowrejects]

dude thats brilliant!!

[ScaleReady]

That is going to mess with your steering pretty bad I would think. You would be steering into the ground dang near, fully drooped.

Correct me if I am wrong.

[calikingcrawler]

The only problem I see with this is it throwing your tracking all off when one side articulates. The link positions wont be the same thus bringing one tire closer or farther away from the chassis

Unless you plan on tieing the chassis hinge plates together side to side so the droop together.

[BansheeManiac]

Very creative, im going to attempt it also, will see what we come up with.
Lance

[JesterSpec]

squat and anti squat are going too be your enemy.

Good luck getting the link locations, you'd almost be better running around a 6" shock layed down instead of 2-3" shocks on the front and rear.

[rangerboy]

might be alright if you are using a clod style axle... still have to have remember drive shaft angles..

[jwo]

i did something along those lines. i wanted to lower the cog as much as possible while still having the advantages of a high gc chassis. it works quite well .goes every where my old setup did with only 2.5" of gc vs. 4-4.5''. the thing is your springs on the top need to be fairly stiff to hold the towers in the up position until the belly cases out. then the shock towers drop. if you tie your left and right shock hing tower together your regular articulation wont suffer.they will drop as one piece. your link geometry must be taken in account as well to help with keeping the hings upright where you want em til cased out. with the setup i run 2.5'' at normal ride height and i can get a 7-8'' when cased out fully. thats with the top shocks limited a little over half.2 control the front and one for the rear. i say go for it, you maybe able to do better then i did. its thinking outside the box.
rs10 based build

[dbrad]

I agree that having all set of parallel chasis plates tied together would be best. Having each side droop as one unit makes sense.

Originally Posted by jwo

i did something along those lines. i wanted to lower the cog as much as possible while still having the advantages of a high gc chassis. it works quite well .goes every where my old setup did with only 2.5" of gc vs. 4-4.5''. the thing is your springs on the top need to be fairly stiff to hold the towers in the up position until the belly cases out. then the shock towers drop. if you tie your left and right shock hing tower together your regular articulation wont suffer.they will drop as one piece. your link geometry must be taken in account as well to help with keeping the hings upright where you want em til cased out. with the setup i run 2.5'' at normal ride height and i can get a 7-8'' when cased out fully. thats with the top shocks limited a little over half.2 control the front and one for the rear. i say go for it, you maybe able to do better then i did. its thinking outside the box.
rs10 based build

You did it!! That's pretty much what I had in mind. The difference between your rig and my idea (other than it not just being a figmet of your imagination) is the links attatch to the main part of the chassis. I wonder what the differnce would cause in the rig's movement.

I think you did an awesome job. I had an RS10 in mind as the basis for the build too. MOA makes this that much more possible but I don't have any MOA alxes at the moment.


The one thing I wanted this chassis idea to acheive was to allow the front axle to drop down over the peak of a near vertical rock where a normal rig would bottom out. You know when your truck is pointing towards the sky. The bottom/rear wheels have traction but the top/front wheels are up in the air and the chassis skid plate is scraping the peak of the rock. I want it to fold down so the front wheels get traction.

I'm glad many of you seem to think this is a good idea and that one of you has actually done it. I will defintiely try this out once I get me some MOA axles.

[dbrad]

Originally Posted by JesterSpec

squat and anti squat are going too be your enemy.

Good luck getting the link locations, you'd almost be better running around a 6" shock layed down instead of 2-3" shocks on the front and rear.

Would a 6" shock make for wild and untameable axle articulation?

What about using 4 x 6" shocks on each end? I do have some of those...

[dbrad]

Originally Posted by PHILLBILLY

That is going to mess with your steering pretty bad I would think. You would be steering into the ground dang near, fully drooped.

Correct me if I am wrong.

Yes. I think you are right. I also had in mind that the chassis would hinge only when the skid plate bottoms out. As long as any number of wheels is the only contact, it would be the 'normally placed' shocks that would allow articulation and travel.

I figure in a situation like the one I described 2 posts ago, the front wheels would actually be on a more horizontal surface whereas the rear would be more vertical.

I guess if the front was hanging over the edge of a drop off, the steering would be messed up. But eihter way, I think you just want to get over the big obstacle and if you're stuck on a skid plate, your steering isn't going to help you anyways.

Can you think of a situation where you actually need to precisely steer out of some kind of bottoming out obstacle?

I appreciate all of the feedback. Keep it coming.

[Grizzly4x4]

While I like your thinking; the extra weight, complication, compromised suspension angles, will all outweigh the benefits seen from the extra doop.

Just my opinion and I could be totally wrong though.

[ScaleReady]

Originally Posted by dbrad

I guess if the front was hanging over the edge of a drop off, the steering would be messed up. But eihter way, I think you just want to get over the big obstacle and if you're stuck on a skid plate, your steering isn't going to help you anyways.

Can you think of a situation where you actually need to precisely steer out of some kind of bottoming out obstacle?

I appreciate all of the feedback. Keep it coming.

WHAT!?!? How long have you been wheelin these RC crawlers???? There are plenty of times where steering helps you get over something you might be highcentered on. Work the steering back and forth, while going forwards and reverse, for one.

[rc_pimp]

Originally Posted by PHILLBILLY

WHAT!?!? How long have you been wheelin these RC crawlers???? There are plenty of times where steering helps you get over something you might be highcentered on. Work the steering back and forth, while going forwards and reverse, for one.

Not that I disagree but I believe this design will help prevent ''high centering" . If you find the skid getting hung on something I think the tires facing straight down would still allow you to pull the skid over the peek by rocking the steering and after a couple inches or so of forward motion your steering angle would improve . I think this i a great idea . It will probably take some time to learn how to drive it to its full potential but well worth it .

[badgravity]

It's cool idea - and it has been done before.
The competition problem was with wheelbase and if i remember correcly rules
state that links and shocks have to be mounted statically.
I can be wrong - just dont feel like looking up the rules right now.

[Grimreeper]

I was thinking if you wanted to get all that droop and not have too much articulation could you try using some really long shocks and a stiff sway bar set-up. I have thought about putting a sway bar on my crawler just have not done it yet. i seems to me that you could get all the droop you wanted and be able to limit the articulation with the swaybar. It may be a little less complicated, probably lighter, and could help on some sidehills. Alright theres the idea somebody build it so i can copy.

[ScaleReady]

Originally Posted by Grimreeper

I was thinking if you wanted to get all that droop and not have too much articulation could you try using some really long shocks and a stiff sway bar set-up. I have thought about putting a sway bar on my crawler just have not done it yet. i seems to me that you could get all the droop you wanted and be able to limit the articulation with the swaybar. It may be a little less complicated, probably lighter, and could help on some sidehills. Alright theres the idea somebody build it so i can copy.

It's been done. Both of my brothers are running a swaybar in the rear. Works good

[rmdesignworks]

Heres my $0.02 for what its worth...the added artciulation is a good idea however the problem I see is moving the entire front or rear tvp section. When the section moves outward it will drastically change your link geometry. Keeping the sides plates where the links tie in rigid is a serious need. However,, that being said a rotating upper plate where the shocks mount would change the ride height without changing the relative positions of the links so your KPI (kingpin inclination) would stay the same.The part not shown in your drawing above is how much the axles will rotate outward when the suspension drops out and inward when it compresses (the degree of rotation based on the KPI). You are also lacking your KPI lines. When you drew it up you moved the axle housings downward but did not follow the rotation arc of the links as they relate to the mounted positions on the axles vs. the chassis. The next issue is the USRCCA rules. My understanding is the shock mounting points must be rigidly mounted to the chassis. I have not confirmed this in the rules but I know its been discussed before. Maybe someone on the rules committee could ring in on this. A pivoting shock mount is relatively speaking rigidly mounted to the chassis through it pivot point but the question still stands,,,would it be legal in a sanctioned comp situation. I wonder if the same basic idea applies to this as to Culetto's CANDY-lever rig?????

As stated previously,,a much longer shock would probably be better and to get the same affect use a winch down to preload to ride height, and release for additional clearance.

[Krakker]

The pivoting chassis is a dead horse. It will never be competitive simply becuase of the steering geometry it will affect and it's cumbersome weight transfer.
Do this instead:


Get the idea?