'72 K5 - Greg's @MightAsWellK5 Build

[blazinzuk]

Rear Roll CG is 26.5" (Based on the same assumptions about Vehicle CG as the front suspension)...

That puts my front roll center a couple inches higher than the rear. IIRC, that is supposed to be the more stable way to do it???

That's what the great and powerful interweb says

Although that's also what most race car guys strive for but suspension geometry affects them much more than it does us.


I don't think I have ever done a suspension where the roll center was lower in the rear than in the front.

 

[FrostBite]

The problem is that in the position it's in now, the draglink is going to be REALLY far out in front, so my steering arms are going to be a mile long. My thought was to push the box forward, and move the pitman arm behind it.... If I did it that way, I could get it really close to the PHB heim and keep the draglink setup a lot closer to the front of the axle (and therefore keep the steering arms to a more reasonable length)

Wouldn't rotating the pitman arm 180* on the Scout box cause the truck to steer opposite of the steering wheel? Or would you be changing boxes?

 

[Greg72]

I'm not really sure what to do now....

I didn't realize that the Scout box was a "front swing" setup, so if I want to use it with this setup, it's going to be complicated to install it where it won't hit the PHB frameside mount.

If it were possible to change the rotation of the Scout box to allow it to be a "rear swing" setup (sector shaft swap? ) then the setup should be pretty straightforward... I guess I should call HOWE and get their input.

A conventional Saginaw 2WD box is obviously set up for the "rear swing" that I need. The problem is that on a lot of trucks it ends up in the way of the tire under full-lock (hard right turn) as it cycles. I've seen solutions where the fabricator builds the steering box into a notch in the frame to improve clearance. With portals, I suppose there is a chance that the tire won't rub (due to large scrub radius of wheel/tire) so that may not be necessary.

I could also try to fit a conventional Saginaw box on the inside of the framerail. It would make the draglink quite a bit shorter than usual, and there might be some issues with blocked fittings (for hydro assist).




-G

 

[FrostBite]

I could also try to fit a conventional Saginaw box on the inside of the framerail. It would make the draglink quite a bit shorter than usual, and there might be some issues with blocked fittings (for hydro assist).

I know the 88-98 and 99-07 4WD trucks have the box on the inside of the frame rail with a rear facing pitman arm while Astro vans (not sure on the years) have the box mounted on the inside with a forward facing arm.

 

[Greg72]

Interesting.

Do you happen to know if either of those applications are easily tapped for hydro assist?

My concern with the Astro van (or some other Toyota or Jeep boxes) would be the overall strength and beefiness of the box for a full-size application. I'm not sure they'd be a great choice for 38" tires and 6000+ Lbs.

Those late model Chevy truck box options do sound interesting though.

EDIT: GoogleFu on AstroVan boxes shows them looking a whole lot like a conventional Saginaw box.... is this true? Same design and strength as all other Saginaw boxes?



-G

 

[4X4HIGH]

Greg, all you need to do is turn the input shaft of the scout box (either direction) and see which way the pitman arm moves then translate that into which way it would be pushing the knuckle to know if the box will work with a rear facing pitman arm.

 

[Greg72]

Greg, all you need to do is turn the input shaft of the scout box (either direction) and see which way the pitman arm moves then translate that into which way it would be pushing the knuckle to know if the box will work with a rear facing pitman arm.

Scotty, not sure I understand you. If the box is set up for a front-swing pitman arm, swapping to a rear-swing arm (with no other changes) will make is steer the opposite way.

I'm imagining a really long double-ended pitman arm (one front swing, one rear swing) mounted to the steering box. If I turn left the front arm moves to the left, but the rear swing arm goes the exact opposite way.... unless there is some way to re-work the box internally I'm not sure how to resolve that.


-G

 

[Greg72]

I found a Howe vendor who actually lists all the available boxes...

http://www.offroadwarehouse.com/products/sfID1/9/sfID2/810/sfID3/812

There's some Ford stuff, Scout stuff, and quite a bit of Saginaw stuff (both inside and outside frame mount).... I just need to figure out which ones are front swing / inside mount and this problem should be solved.

The Scout box may end up being more trouble than it's worth, but I can easily sell it and get my money back on that one... maybe even cover my costs for Brakeleen and toothbrushes that I used to degrease it initially.

-G

 

[blazinzuk]

Astro boxes are the same as the Jeep boxes and most other saginaw boxes. Similar in size ( if not exactly the same) as the full size truck boxes.

Ford box is long like a scout box but swings the other way.

Astro box is like the scout box.

So no way to mount it in and around the pahnhard bracket, kind of always what I thought you would do with it.

Look at radiator clearance too for any other box. My axle was far enough forward I ran into steering problems and had to move my box which required moving the rad to one side and cutting out one corner of the side tank

 

[ktmoutfront]

I solved the clearance issue between the PHB and drag link by running the drag link to the right side. Then back down to the drivers side with the PHB following from the right to left also.

 

[MNorby]

I solved the clearance issue between the PHB and drag link by running the drag link to the right side. Then back down to the drivers side with the PHB following from the right to left also.

Can kinda get your geometry a little flatter too with a swingset like that. 2 birds/1 stone for clearance and geometry.

 

[Greg72]

I solved the clearance issue between the PHB and drag link by running the drag link to the right side. Then back down to the drivers side with the PHB following from the right to left also.

Huh?! You got a photo of that.....?? Post it up here, I'd like to see it.

Astro boxes are the same as the Jeep boxes and most other saginaw boxes. Similar in size ( if not exactly the same) as the full size truck boxes.

Ford box is long like a scout box but swings the other way.

Astro box is like the scout box.

So no way to mount it in and around the pahnhard bracket, kind of always what I thought you would do with it.

Look at radiator clearance too for any other box. My axle was far enough forward I ran into steering problems and had to move my box which required moving the rad to one side and cutting out one corner of the side tank

Eric,

It's just starting to feel like too much of a fight to fit the "oddball" Scout box into this application.... I'm not sure there's enough of an advantage once I'm all done to justify all of the extra effort.

If I can get an inside mount steering box with a forward swing, then I get all the tire clearance I want and I get the "more perfect" steering setup where the pitman arm swings the same way as the knuckles....

Too many options.... like you said before. It almost makes it harder to build when just about "EVERYTHING" is open for disussion. Steering box choices, modify the frame to fit, front swing, rear swing. It almost makes it hard to get started sometimes.


-G

 

[Chevy305]

How are you going to put a steering shaft on an inside frame box? There's gotta be a whole lot of engine, accessories, and headers in the way

Do you have a standard 2wd truck box? If so try it out. Maybe you'll have to move the PHB bracket back an inch or two but it'd be wortg the saved headaches. Just an idea.

 

[ktmoutfront]

Huh?! You got a photo of that.....?? Post it up here, I'd like to see it.

 

[MNorby]

imagine different variations of this: http://www.pirate4x4.com/forum/15180213-post197.html

Also Wally has a similar steering concept: http://offroaddesign.com/K5morph.htm

 

[Greg72]

I like those!

I remember printing out those photos a while back.... it was really impressive the way the ram was integrated into the steering system directly at the pitman arm.

The question I have though is that the GOAT and ktmoutfront setups both incorporate an idler arm which adds some kind of other "ratio" into the steering system. I was already struggling to figure out the pitman arm length vs. steering arm length ratios relative to steering knuckle angles, and now it seems like those would add yet another consideration.

This might be a lot simpler than I realize, and I'm just stressing out too much. There's a good chance that I could bolt a normal Saginaw box in the stock location without any tire rubbing issues... so I'm doing a lot of extra worrying for no reason. Maybe I should assemble one more portal housing and mount it to the driver's side (with the tire & wheel) and just crank it hard right to see if I'm anywhere near the framerail? That might be a good first step for this weekend.

Simplicity is the key

At first glance, this entire build may appear to be the antithesis of simplicity... but I would argue that it truly is attempting to solve problems in the simplest possible ways. Notice, I didn't say "least expensive" ways... I will concede that costs have gotten completely out of hand on this build.


-G

 

[MNorby]

You could make multiple holes for the different steering linkages so it could be adjustable one everything is together to change the ratio or make the two linkage on the idler in the same location side-by-side so there is no ratio change.

 

[ktmoutfront]

What was lost in my pitman arm, I made up for in the drop idler arm. Shorter pitman arm also gives the box more strength.

 

[folkenheath]

This might be a lot simpler than I realize, and I'm just stressing out too much. There's a good chance that I could bolt a normal Saginaw box in the stock location without any tire rubbing issues... so I'm doing a lot of extra worrying for no reason. Maybe I should assemble one more portal housing and mount it to the driver's side (with the tire & wheel) and just crank it hard right to see if I'm anywhere near the framerail? That might be a good first step for this weekend.
-G

I agree, figure out if you even have a problem. Those idler arms are decent solutions for long travel setups, however, using one for 12 - 14" of travel seems like overcomplicating things for no reason. Now if you do have a major tire clearance issue, then its a valid point. However, I think with your limited uptravel do to the portals, you are less likely to have clearance issues anyway.

As for the ratios, if you have two ratios, you just multiply them, easy to figure out the correct one.

If you use an idler on the passenger side, then you need to move your panhard frame mount on the passenger side as well.

 

[ashman]

If you use an idler on the passenger side, then you need to move your panhard frame mount on the passenger side as well.

looking forward to the "hmmm, PS frame rail is too high now, gotta fix that" updates.