torque tube VS wishbone length

OK, so I was checking out the OSHR website, looking at pictures of their "1 of 10" pickups. I noticed something, though, that I could not understand. All the trucks are using an enclosed driveshaft and what looks like front wishbones on the back. The funny part is that the wishbones look to be about half the length of the torque tube. How does this work without binding; both in terms of the distance and angles changing at different rates? Maybe I have it wrong in my head, or maybe there is a little more play than I thought, but I was always told they had to be the same length and that is why you can't use an enclosed driveshaft with paralell leaves or a 4-link.
I am curious about this because if it works the way they have it, it would solve the problem i am about to run into on my ch***is.

Here is their website (I could not figure out how to post pics here yet) just go to build photos and you can see: http://www.oldspeedhotrods.com/main.html

Thanks, drZ

 

If the bones still attach to the torque tube the lenght doesn't really matter. If they are split and still running a torque tube even if they pivot at the ujoint centerline you will still get some binding. Rear bones split and mounted outboard to the frame even with open drive will still have binding issues if both rear wheels do not move together. To many builders do what they think looks good with no thought for the engineering to work correctly.

 

The torque tube is the suspension locater, and original "radius rods" in back aren't...they are just braces between the TT and axle housings, irrelevant to geometry.
Splitting them will force twist if they are same length as TT to U-joint center, twist and severe binding under all conditions if short.
It is absolutely CRAZY imho to split rear rods with a torque tube...the geometrical issues are at the catastrophic level, a FAR greater problem than front or rear open splits. Since they are braces, they can be shortened and brought back (like a '48 Ford), moved inward on axle, or even made in a different shape to clear severely lowered frame.

 

Yeah, it's got a 3 link in the rear with an enclosed drive line, weird! I think those guys are members, See if they'll chime in on this....

Edit: I just sent them a PM. I can't see how this wouldn't cause problem, maybe they have some info that I can't glean from the pics.

 

the way this is set up, it looks like it would be pushing the engine and trans fore and aft as the rear suspension cycles...

 

chevy used a slip joint in the torque tube, making it a torque tube only and not a suspension locator
with that setup you can split the bones not have the bind when working on a flat plane, but the problem still exists on a twist where the tubular shaped rearend is fighting the tortional forces from the split wishbones

it was done alot on early race cars, but they replaced things more often and were most likely lighter
also it acts as a sway bar so it was beneficial to them in that respect

you could put a rotating slip joint on the ends of the wishbones and it would work, this is how the chevy paralell leaf springs are attached

 

Hard to say, but they appear to be mounted in the stock location...

Not unless it rips the filler panel from below the bed off when the rear cycles...


Hopefully they show up soon to aleviate my speculation.

 

well, it looks like i am not going crazy afterall! thats refreshing. did anybody hear back from them as to how well it works? if they figured out a way, it would solve my problem.
for the record, though, i didn't want to call them out or question there work; it was just a good example of the problem i am facing.
-drZ

 

I saw that in a magazine...I think it is actually going into a small production run!
It looks totall FUBAR, but as in those pictures I cannot see all the details so cannot say.
Appearance is that rear is totally located in the style of a Lotus 7 (lower triangular strut is missing in some of the pics above) and then totally located in a VERY different arc by the torque tube. I kinda thought there might be so much conflict there that the thing might well hold its ride height with the springs removed...
I'd love to be able to look this over without the limits of the photos...there is too much unseen for judgement.
It is a very detailed pro built car destined for some kind of production...so what is really going on in that suspension?

 

The suspension has a total of 3" of travel. We have experienced no binding issues or other types of problems with this set up to date. I know that we would run into these types of issues with more travel. We made a calculated decision on this as well as the front suspension. We have been asked about and reprimanded for running a rack with a beam axle. It works great and lacks the bumpsteer that so many claimed it would have.

We, like most builders somtimes sacrafice some function to gain form. Lowered cars are a good example of this.

How about posting some pics of your ch***is that is about to run into some problems. Your choice to post what you believe to be a problem with our pickups suspension to research for your build is a little suspect.

 

How about you have your lowered car, WITH good geometry?

Move the kick in your frame farther forward, and you'll have room for the standard wishbone that attaches to the torquetube. Sounds pretty simple, so give it some thought.

 

well, according to the site they are selling that rolling ch***is for $29,500 (with the flattie) and i think i heard the complete truck is gonna run about $65,000. OUCH!!!!
-drZ

 

If it works...fine
But WHY build in conflict? Drop the torque tube, and you have a complete suspension system.
Drop the modern stuff, add a '48 Ford panhard, and you have a complete system.
The problem is the multiplicity of arcs.
Is this saved by the crossmember flexing or what?
There really does not seem a need based on lowering, as the torque tube could be braced with a narrower than stock triangulation, leaving forward system at full function, or if the tube were dropped, the rear suspension system would be in the clear.
Sorry. I haven't seen it in person or bounced the suspension...those arcs just look painfully different even for minimal travel. Seems to me something has to be bending and there is no need for it to have to.

 

Guess you missed point with the lowered car comment I made. Every rational person knows that you give away somthing when you lower a car significantly. You also make it look better in most cases.

You are right....what were we thinking. I will call you next time I want to design a frame... Oh wait...Seems like the rest of the rear suspension and body panels and battery tray...etc. wont work anymore. Oh.. I know... I can do what everyone else does. That will solve all of my problems.

How about you build cars the way you want and we will continue to build **** with screwed up geometry that we think looks good. I feel much better now that I have a consultant like you to help out.

By the way. I was asked a couple of times to comment on this thread and did so to try to explain why we did what we did. I didnt pose the question or ask for anyones opinion of the truck. The truck speaks for itself just like the 3 hot rods that we are bringing to the Grand National this year will.

 

No problem, glad to help. Just sorry you couldn't think of another way to build your car with proper geometry. And I'll forgive my consultant fee, since you're a first-time customer and all.

As for you not asking for opinions, anytime a builder puts their work out in this madcap internet world, they are gonna get people talking about it. I guess you could take all the pictures off your site.....

 

To each his own, I prefer more suspension travel. This setup would work OK with no issues if you built fore/aft sliding motor/transmission mounts. Then you'd really not be doing what everybody else does......

 

i think i was missunderstood a bit on this thread. it was not meant to question you in front of everyone, i was just curious about it because i have seen it before on other cars and your site had good pictures to use as an example.
as for my ch***is, right now i have 2 bare rails and a big stack of parts. i have made a series of drawings, but am trying to plan it out as best i can before i start welding so i don't run into problems later.
i figured, since you are taking cars to the grand nationals while i am selling parts, there has got to be something you know that i don't.
-drZ

 

The fundamental problem is not lowering or lackof space...it is that the car has two complete suspension locating systems, and it is hard to believe that they are compatible.
If the crossmember is left as is, flex there might well keep the torquetube from ***erting itself. That is getting real close to your sliding mounts idea.

 

I think Bruce figured it out for us lunkheads with no "vision". The aluminum ****** crossmember is FLEXIBLE. Right?

I'm sorry, I should stop now. But I just couldn't leave the old "it doesn't have much travel" excuse sitting there. That's no reason for bad engineering. Granted, I like to build stuff like Henry Ford did (unsplit wishbones), so maybe I am just not a competent imagineer.

 

You are right....what were we thinking. I will call you next time I want to design a frame... Oh wait...Seems like the rest of the rear suspension and body panels and battery tray...etc. wont work anymore. Oh.. I know... I can do what everyone else does. That will solve all of my problems.

How about you build cars the way you want and we will continue to build **** with screwed up geometry that we think looks good. I feel much better now that I have a consultant like you to help out.[



trial and error is fine ....i see lots of messed up stuff on this board when it breaks you learn ....i guess thats about as traditional as it gets , but when you run a SHOP and are charging for builds.... laws of geometry should be well known if you plan on trying to re-invent the wheel...HOTRODS, RACE CARS ,CARS in general, FORM follows FUNCTION,that IS the RULE !!! unless you are just trailering your cars to the fairgrounds ...then it might last for a little while !!!a car is meant to drive and work properly....thats its job! no wonder most the baja race shops think hotrod shops are hacks ....they can build trucks with 3 FEET of wheel travel and go 1000 miles well over 100mph in a race... and somehow guys are struggling with 3" of wheel travel, but yet it looks sooo cool.......screw it im going back to my shop and finish my hemi powered outhouse ..cant drive that either but it sure looks cool!

 

I've seen this car at several shows here in So Cal and I was very impressed with the fabrication. But as an engineer, I couldn't get past the 3 different length suspension.
I looked at it for a long time. I then asked someone that was ***osiated with this build and still did not get an explination about this conflicting set up. The reply was "we haven't driven it much yet".

Based on the replys to this thread by the builder, I still don't see him explaining a rational engineering theory behind his alternitive suspension geometry. In fact as a potential customer, I am diascouraged by his extremely defensive position to a justifyable concern.

My $0.02
.

 

I know nothing about setting up suspensions as such as this,The normal stuff is what I stick to, but I would love to see how this will perform through 10,000 miles, and what the person that puts the 10,000 miles on it looks like after the ride.

looks aint everything if you cant enjoy it..maybe this is only a trailer queen, that would explain alot.

would like to see a video of that set up in action,..

 

It was done as a "this looks cool" deal with lack of understanding of how linkages work, plain and simple. There are numerous books on how to properly design a rear suspension; it would be a wise investment to purchase one when building a ch***is/suspension from scratch.

 

The bizarre thing is that there are two perfectly good linkages; they just put them into too few cars.

 

Whatever happened to people being able to simply talk, discuss stuff, without getting all macho in-your-face aggressive defensive?



You got something you're embarr***ed about?

And the steering rack you have won't cause bump steer.....nope......because the wheels will turn in opposite directions as the axle moves up and down, hence no steering change, just tyre scrub. Simplest of simple steering geometry rules.

Other than that, you have some real nice engineering going on there, shame it is let down by your at***ude.

 

All who have posted questioning this setup are on the right track. You cannnot have two arcs of travel locating the same member (rearend)without having bind. It was stated there is 3" of travel but I suspect that that is the amount of movement until you reach a totally bound up situation in both directions . At this time you're stressing components to their limit. At that point your into destructive territory and something WILL fail or stretch to accomodate the pressure applied if cycled too many times. Neither outcome is good.
Seeing as these builders are young and know everything I say "full steam ahead". It will be tragic if this design ends up in a lawsuit but in this day and age it will if anyone so much as gets a scratch because of it and a "ambulance chaser lawyer" handles the case. If so the court system will have you for lunch. Buy lots of insurance.

Frank

 

There are clearer photos in November's Street Rodder - I just read the feature and I couldn't figure out how it could work. There's the torque tube, the two short radius arms and a wishbone-type track locator as well?

 

Still - the Garamond typeface was quite lovely n' sweet...