Why not independent susp ?

[builder]

I have a Kyosho USA-1 and I'm in the process of turning it into a crawler. I notice people locking out the suspension arms on I.S. trucks but why ? I have never crawled so maybe it will be obvious when i get out there and play around with others driving solid axle trucks.

I have a suspension idea to increase the wheel articulation by A LOT but if there are other qualities that I need but can't get out of an independent susp truck i'll just keep my Kyosho as a basher and buy something else for serious driving.

[zeroskater9111]

what kind of kyosho i have a mad truck heng long??

[Mnster]

Usa-1 would never hold up to crawling. The suspension has no where near enough travel the drivelines are far to weak. Independent has several downfalls, the most noticable is the loss of ground clearance on compression.

[run2jeepn]

Cut and Pasted:

Independent versus Solid Axles

The debate between Independent suspension and solid axles is a holy war that has raged for years. The truth of the matter is that each design has properties that are both good and bad for different things. For rock crawling, the solid axle offers so many advantages that it's barely a question; very few serious rock rigs even consider using independent suspensions.
Independent Suspension

There are a few ways to do it, but the basic idea of an independent suspension is to make each wheel move up and down separately from any of the others. This reduces the amount of motion in the suspension, which contributes to a more comfortable ride, and helps improve traction on relatively flat surfaces at high speed.
Solid Axles

A solid axle is exactly what it says; a single, inflexible housing that extends from one wheel to the other. If one wheel goes up, the one on the other side goes down. While this can make the ride a little more bumpy on the street, it helps get traction at low speeds by improving the chances your tires are touching. Almost more importantly, a solid axle has fewer moving parts and almost always has a stronger, less exposed design. In short, a solid axle has fewer potential points of failure.
Suspension Travel

To make the comparison, let's consider my solid-axle YJ and a fully independent Hummer (H1). The course includes a large boulder, about twenty inches tall, located on the side of the trail and narrow enough that only one tire will ever be on the boulder at a time. This is a common thing on many trails, so it's perfect for our example.
In our example, our Hummer drives up until the front passenger side tire is on the rock. The ground beneath all three other tires is level, however, because the front tire is on the rock, the vehicle chassis is no longer parallel to the ground. The rock on the passenger side is compressing the suspension, as well as lifting the chassis. On the driver's side, the increased weight because of the angle is causing some compression on that side as well, which actually increases the angle between the chassis and the ground. In the rear of the vehicle, the angle is also compressing the driver's side suspension, but there's no rock to push up on the passenger side. Because there's no force pushing either up or down on the passenger side tire, it remains in a neutral position, several inches in the air.
Next, let's consider my YJ. I approach the rock the same way, and pull my front passenger tire up onto the rock. Like the Hummer, my passenger side suspension compresses. Unlike the Hummer, my solid axle pivots around the differential, so as my passenger side suspension compresses, the driver's side tire is actually pushed down, decompressing the suspension on that side. This reduces the angle between my chassis and the ground. Moving to the back tires, we see that the driver's side rear axle is being pushed up because of the angle of the chassis. Again, the axle pivots around the differential, and my passenger side tire is pushed down. In fact, my rear passenger tire is being pushed down against the ground, despite that side of my vehicle being "light". Unlike the Hummer, all four of my tires are in contact with the ground, affording me better traction. It's also significant to note that my chassis is at a smaller angle to the ground than the Hummer; I'm not as close to my roll-over angle as the Hummer.
Before we dismiss the independent suspension completely as an undesirable rock-crawling system, there is one thing to consider; modern suspension designs allow for a hydraulic, adjustable suspension. A well designed adjustable independent suspension could overcome most of the suspension-travel flaws in the independent suspension design. By the same measure, however, a hydraulically adjustable suspension would be equally capable of providing the same advantages in a solid-axle set-up.
Potential for Damage

One of the best attributes of an independent suspension in an off-road vehicle is the ability to move the differential up and out of harm's way, increasing center clearance. Unfortunately, the necessity for moving parts to allow for the relocated differential introduces an inherent weakness. In a solid axle set-up, the weakest link is almost always the CV joint in each steering axle shaft. The need for flexibility not only exposes the shaft, but it adds a number of small moving parts. In an independent suspension, every axle shaft, even the non-steering ones, have not one but two CV joints. This not only introduces more potential failure points, but it exposes even more of the axle shaft. Even the best independent suspensions are more prone to failure than a solid axle equivalent, so obtaining equal strength means greater weight.
Solid axle designers have come up with an interesting technique for lifting not just the differential, but the entire axle, up relative to the wheels. This design, known as Portal Axles, uses a set of gears at the outer end of the axle shafts to position the center of the wheels several inches below the center of the main axle shaft. While this does introduce an additional level of complexity, the advantage is that doesn't need flexibility and can be completely enclosed in a solid housing. Another great advantage of portal axles is that the portal gears can be set up at unequal ratios, increasing the final gear ratio to provide even more torque and slower speeds. The Mercedes Benz Unimog stands out as an example of the advantages of a portal axle.
The conclusion, then, is that while independent suspensions may be desirable for high speeds, in the world of rock-crawling, the solid axle is the clear winner.

[asfasasu3]

Thats a very interesting read. I can agree with some of it but not all. I.S. has not done well in off road trucks, but look at what they do in quads. Hands down they beat the solid axle conterparts in the rough stuff. Maybe the right people just haven't figured out the trucks yet.

[jbrandt]

there is also another advantage to a solid axle for crawling vs. Indy susp.

When moving over rocks (as rock crawlers ofter do ), the differential on a solid axle does not move relative to the wheels, meaning its ground clearance remains the same. With IFS, when you move one tire over a rock, your diff actaully get closer to the ground, which increases the chance it will hit something and cause breakage.

With 1:1's IFS setups usually don't offer enough travel at a high enough strenght for serious crawling, so that's another reason 1:1 crawlers go for solid axles.

[builder]

I see it's about ground clearance at the point of compression. I've seen videos of hummers do some impressive shit even with one wheel off the ground. Maybe it's just the sheer size of the thing.

When I finally find or buy the cable that connects my camcorder to my comp i'll send in some pics of my truck with the rear tranny pivoting on a threaded rod allowing it to get impressive susp travel. I can turn either end of the truck 90 degrees in either direction. Also I have telescopic suspension arms I designed for my buggy that allow the wheels to maintain track width as the suspension moves up and down as well as increasing susp travel 30% over a similiar susp setup.

But if it's all about ground clearance I think i'm screwed.

[asfasasu3]

A couple of years ago there was a guy that built and run an independant susp. rig in rock crawling. He done pretty good but did have problems with breakage. Just like most other racing type events, when your running for points, you have to finish. He finally went back to the straight axle. I beleive it could be done, just not sure how.

[defiepilex]

ha this thread is perfect! i just joined the forum and was talking to another forumee about why this isn't standard when i came across this. thanks!

[JeremyH]

Originally Posted by asfasasu3

Maybe the right people just haven't figured out the trucks yet.

The "right" people have tried it:



He switched back to solid axles pretty quickly.

(rest of the story)

[hawnmt]

Originally Posted by builder

I've seen videos of hummers do some impressive shit even with one wheel off the ground. Maybe it's just the sheer size of the thing.

HMMWVs and the original Hummers also have design advantages that most independent suspension setups don't.

They run geared hubs, which means the axles don't come into the center line of the hub. They enter above it, into a gear that drives the wheel. The advantage is the axle is a little higher out of harms way but it also means the diff sits higher with good CV angles for better ground clearance.

Also the the drivetrain is all on one plane inbetween the frame rails so it can drag it's self over obstacles. Mixed in with fact that you sit on the same level as it, makes for a relatively low center of gravity and a very wide vehicle. That in turn is why they can sidehill like nothing else.

[run2jeepn]

Originally Posted by JeremyH

The "right" people have tried it:



He switched back to solid axles pretty quickly.

(rest of the story)

Thats the same rig I was thinking of when he stated that. Many others have tied it aswell.

As for the Quad part. Quads don't Rock Crawl. IS or even IF set ups are for Speed. They are able to soak up those high jumps and wash board area's better then Most Solid axle set ups.

Having a tire in the Air and still moving has nothing to do with the Axle Set up. Thats Lockers that keep you moving. Having all the power going to all the wheels at once.

As for right now Solid axles rule for Crawlers. May not always be that way, but for now it is. So keep trying and thinking of new way to put a new twist on IS set ups. Never now you or someone else may start the next big thing.

[SnoopMaxx]

I had a clod monster ... it was ok at the time
I now have a jug2 an E-maxx and a Wheely King

I have used all 4 for bashing, hill climbe and crawling
all great trusks in there own way

[nj05nismo]

IIRC evans went back to solid axles b/c of some rule infringement and difficulty in tuning (not reliability or amount of flex)...but i could be wrong...

in my opinion a properly set up IFS of FIS system could be made to work, and work well on the rocks. Hell my frontier (with IFS) can go anywhere a jeep can go with similar mods, just as easily and sometimes even easier (i wheel with a lot of jeeps, many of whom are more modded than me). that being said my IFS is weaker and has no parts for it so as soon as im done vet school im throwinga solid axle under the front of it. But i really think that the ifs has potential if your willing to do some major fab work.

[elvis]

This thread took a turn for the real really quicky. Remember whats true for 1.1's doesn't always hold true for 1.10. We all know this. As for weather an I.S. truck would be good for crawling yes and no. Before the tlt was king of the 2.2 rockpile I crawled with a wild dagger for a scale truck. Hey it was the best I could find in a 2.2/scale size that was 4wd. It had a few small issues like at extreme travel the dogbones would sometimes walk out, this could've been easily fixed with pede sliders but I didn't know of them at the time. Other than that I had no issues with breakage. That truck was given to my buddy as an x-mas present to get him started in crawling and he still runs it in the same config I did.

There are some drawbacks to the geometry though for instance say you put a tire on a rock thats side angle is 45deg a solid truck with enough travel will keep the tread of the tire on the surface of the rock at a 45deg angle also meaning your getting 100 percent of the tires traction ( not including lateral slippage and the traction circle)
Where as the indy rig will keep its tire at a constant parallel to the chassis ( assuming there is no built in camber gain) so if the chassis only tilts to say a 25deg angle (because the rear is flexing too) the tread is also at a 25deg angle decreasing the contact area and traction.

To answer your query the usa1 is not really good for this parts are hard to get and they are weak trucks mostly made to go fast and jump at the track.
If it's all you have and can afford go for it just slap on parts that can easily be transfered to a solid rig like good 2.2 tires/lathe motors/etc and see where it can take you. Then try driving a set up solid truck and see which one YOU like better. You may like the usa1 and keep building it. Most likely you will drive the solid and fall madly in love with it.....and have its babies!

Apologies for the novel.

Hope this helps.

[rockwerks]

built 2 indy crawlers. (RC) they jsut simply dont work well but to lack of traction and total articulation. why solid axles work better is LEVERAGE, as one tire climbs the axle twists and causes force to travel to the other side. (much more complicated but the general Idea)

[builder]

I like the building better than the driving to be honest but if the usa-1 is too much of a hassle i'll probably get a tamiya 350 and build a nice scale crawler. Although if i could get by with a "real" crawler that would be good too I only worry about track width on a serious crawler being to wide for most bodies. Also my telescopic arms would work with solid axles but I doubt I would even need them.

[KnutKase]

I simply locked out the ind. suspension and attached the resulting arched solid axles to an aluminum frame using home made links (Du-Bro 4-40 rod-ends aluminum tubing 4-40 allthread) and traxxas shocks, also made up some curved tie rods and mounted the servos to gearboxes with home made mounts... I then removed the stock bumpers, attached the stock body mounts to the new frame, wired it up...

[rockwerks]

Originally Posted by KnutKase

I simply locked out the ind. suspension and attached the resulting arched solid axles to an aluminum frame using home made links (Du-Bro 4-40 rod-ends aluminum tubing 4-40 allthread) and traxxas shocks, also made up some curved tie rods and mounted the servos to gearboxes with home made mounts... I then removed the stock bumpers, attached the stock body mounts to the new frame, wired it up...

That would mean its no longer independent suspension then correct?

[O.C.D.]

I may have missed it but another very important factor is initial ground clearance. All of these Chevy IFS trucks you see running around on 37"-44" boggers or iroks are basically not getting anymore ground clearance from their lifts. They simply lower the transfer case mounts/supports and in turn only lower the whole system. It is still mounted to the frame. They rarely gain more suspension travel as there arms are rarely lengthened. Sure they can run the big tires, but those big tires will not stuff anymore than a stock suspension.

A solid axle lift obviously lowers the entire axle from the frame. When you lower it the axis is dramatically dropped depending on how big the lift is. Now you have that much more articulation to stuff the tires and also max out the suspension.