Cantilever variation.

MNGSX

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I need the area aft of my rear axle for a sub tank on my 80 series land cruiser. I am more than willing to massage the shape of the fenders and even tub the rear fenders a bit but I want to keep the shocks out of the interior. The only place I could have a shock hoop inside anyway would require attaching the bottom of the shock to the axle or close to it reducing travel with a given shock length.

It is not to scale for sure but just the basic concept.

It would allow for a traditional type of lower link and for the mounting of shocks a bit farther forward than a "helmet" link or some of the other cantilever systems I have seen. I also think the two links for the bottom of the shock are a simpler way than a rocker arm.
 

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partybarge_pilot

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The main problem with that is your motion ratio is going the wrong direction. AT full bump your shock would be doing almost nothing. You would be way better off with a bell crank set-up.
 

De Ranged

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It will work but with that design you will find that the shock performance curve is ramping down...
Right at the start of the wheel travel (from bottomed out) the shock will compress at the fastest rate, and the further up the wheel comes the slower the shock compression... just looking at it I'd say the last 4" or so of wheel travel would have next to no shock response

The ride would be harsh on small bumps and it would bottom out aggresivly on large landings

If all you are worried about is locating the shock under the floor of the truck... run fixed pivot pionts off the chassi and a cantilever arm this will make your shock perform the same as dirrectly attacted to the swing arm

Cheers Reece
 

MNGSX

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I look at it now and can see that the where the two links meet would be moving less than the link mounting point to the lower arm...

This was a quick edit... Closer?
 

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Scott_F

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Your last idea may be worse, if that is possible. You need to understand the concepts of motion ratio, rising rate and falling rate.
 

De Ranged

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you havn't changed the design... the motion on the shock will be exactly the same

I was going to draw a pic to show you the motion and how it effects the shock but I've got a couple of clients in the shop so I'll make this quick

hold your hands out infront of you, so you can look at the sides of your hands, fingertips piont to piont, this is where the shock attatches one palm is the chassi the other the swing arm, now keeping your fingers straight move the shock mount a bit... with your fingers near flat notice how your palms dont get closer but you have alot of movement at your tips, so if that was on your truck the shock & spring would be working ALOT for very little wheel travel
Now peak your fingers this is simulating full travel notice how your palms can move in and out easily with no in and out motion at your finger tips.... so you suspension on the last of its travel would be increadably soft bottoming out very harshly

Hope this helped lol

Cheers Reece
 

MNGSX

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Not enough travel.. 12" of travel can be done on the 80 by modifying the existing shock mounts.. 10" is pretty easy to do.. But in either case you need to lower the bump stops to prevent bottoming the shock out. It works out ok for crawling articulation but reduces whooptybility.

As you can see form that shot that a large shock could fit if it was closer to paralleling the frame rail. I kind of like the challenge and think it is all worth it if I can get a bunch of travel out of it.

This is all just the basic concept. Once I have a direction I will use a CAD program and crunch some numbers.. Does this look more like it?
 

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De Ranged

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Can you make that any smaller lol getting better but you need to make your cantilever arm "L" shaped so you shock mounting arm will compress the shock .... at the moment its not really compressing the shock....

Cheers Reece
 

DSRacing

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MNGSX,

Your heading in the right direction with your last design. I would put a little more thought into the design of the bellcrank. I posted some photos of other cantilever designs people have built in the past. Granted most of these are mounted on leaf spring vehicles but the concept is the same. The last photo is the old Baldwin TT. Here's a link to a thread not too long ago which has some good info.

http://www.race-dezert.com/forum/showthread.php?t=50695&page=2&highlight=Cantilever+suspension







 

MNGSX

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DSRacing thanks.

I think the third photo has bell cranks that are the closest to what I need based upon the direction of the shock motion in relation to the axle.
 

MNGSX

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I am also considering connecting the link closer to the axle and building straight DOM tube lower arms. I can get the ratio from the bell crank and it makes packaging easier.


I think I may make a scale model of my frame and axles. Then make scale links and a bellcrank. This ought to make R&D more economical and effective.
 

Cpt_Radical

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The 3rd photo is my cantilever that I designed and built. I love it. It is designed with 22" of travel, but I limited it to 18" with the set of leafs that I have.
 

atomicjoe23

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MNGSX. . .the thread you were referred to was a thread I started about a year ago. . .there is a lot of good information in it, but I will caution you that getting the geometry correct is a LOT of work.

I haven't abandoned the idea of a cantilever suspension, I still love the idea!. . .and they look SUPER trick!

That being said I have decided to tackle some easier projects first and get to really understand everything about how a suspension system works more thoroughly before I tackle a cantilever system. . .my last project really helped me understand wheel rate vs. shock rate and therefore motion ratio a lot. . .that was just setting up the front shocks in the A-arms and trailing arms we made for a single seat race buggy that we made. . .

. . .good luck! and post pic's up of whatever you come up with!
 

MNGSX

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I think the scale mock up of things will really help me get it designed right when it is time to make the real full size version. I will likely make a scale version of the chassis, rear cantilever and front 3 link with panhard (Radius arms going bye bye).
 

atomicjoe23

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I think the scale model would help also. . .especially since this is your first cantilever project. . .seems this is one of those things that the first is VERY difficult to get right, but after the initial steep learning curve it should be a LOT easier.
 
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