ChefBear
1/2 ton status
Fish a line through and use some drip irigation with one of those small micro srinklers on the end and just pull it through...
CK5
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'72 K5 - Greg's @MightAsWellK5 Build
- Thread starter Greg72
- Start date
This is the build description. I will improve this later. (GB)
Hey Greg, how about installing all of the body mount brackets to the frame then snuggly bolting each frame rail to the body and then do some measurements and square the frame accordingly then build crossmembers to fit between the frame rails?
Scotty,
That's the idea I wanted to use (simplest)... the problem is that the body is sitting on a HUGE wooden dolly now with a 4-ply 2x4" header spanning between the DS & PS body mounts at position #1, and another 2x10" header around position #4.
The entire dolly is on wheels now so I can roll it back and forth, but unless I completely rebuild it there is no way to get the frame rails to bolt to it directly... dropping plumblines is a little tedious, but it should produce the same effect and give me a very accurate set of dimensions to build from.
That's the idea I wanted to use (simplest)... the problem is that the body is sitting on a HUGE wooden dolly now with a 4-ply 2x4" header spanning between the DS & PS body mounts at position #1, and another 2x10" header around position #4.
The entire dolly is on wheels now so I can roll it back and forth, but unless I completely rebuild it there is no way to get the frame rails to bolt to it directly... dropping plumblines is a little tedious, but it should produce the same effect and give me a very accurate set of dimensions to build from.
champsjimmy
Registered Member
There's a place in Chicago that builds utility trailers and dips the whole trailer to galvanize it, so I know it's possible. Unless it's designed for it the heat may warp the frame badly though.
PK
PK
... dropping plumblines is a little tedious, but it should produce the same effect and give me a very accurate set of dimensions to build from.
True, but only if the body is dead level and has no twist to it at all...
Rene
bp71k5
3/4 ton status
Greg,
How tall are those dolly wheels? I wonder if you could remove them and drop the dolly height enough to gain some headroom and then insert the frame rails between wooden dolly and the body. Since your frame is apart, muscling in each side of the frame might not be that bad... I'm going to keep watching either way though.
Brian, as i see it Gregs problem would be with the dolly itself being in his way to do what i suggested, has nothing to do with the wheels themselves.
bp71k5
3/4 ton status
I know the wheels aren't in the way themselves. I was suggesting that the new frame rails go on top of the wooden dolly and then place the body onto the rails like you were suggesting. The problem with that idea looks like the body is already too close to the ceiling light fixtures and can't go any higher. I was asking whether removing the wheels would allow the whole wooden structure to drop down enough to make room at the ceiling.
Wouldn't it be simpler to just get a set of stock frame dimension's and build off of those?
...you sound like an engineer or somethin'
.........................................................
...you sound like an engineer or somethin'
.........................................................
Wouldn't it be simpler to just get a set of stock frame dimension's and build off of those?
...you sound like an engineer or somethin'
Sure, find me a document with the stock Blazer dimensions and I'll be happy to use it. You're "plugged in" over on the 67-72 Boards...maybe people will help you more than they helped me with that request??
Factory Assembly Manual doesn't show frame dimensions for Blazer....only for pickup and 'Burb.
I'm not to proud to accept help. If you (or anyone else here) finds the numbers I'll use 'em.
2009.12.16 - UPDATE! - SCRUB RADIUS CALCULATOR DEBUTS!...
There is a lot of background work going on right now as the crossmember questions are being considered. With a multi-link suspension design in the works, those crossmembers become not just frame supports, but integral connection points for the link ends....so the exact location of the crossmembers needs to make sense based on where the heims are going to land also.
Additionally, I'm still trying to work out the overall track width for the new axles so that I don't end up with a truck that's 90" wide at the tires, AND ideally it should run down the street correctly and be able to make effective u-turns as needed. Portal hubs add a bit more complexity to the front steering geometry so I had to create another "product" to help me calculate things.....so:
I proudly present.... in it's CK5 debut, SCRUB RADIUS CALCULATOR v1.0!!!! [applause]
This program basically shows a cutaway front view of the tire/wheel combination based on tire diameter, width, wheel size and backspacing and then superimposes a vertical yellow line representing the tire centerline.
Next by adding the actual measurements of the portal knuckle (or standard D60 kunckle, this program will do any axle type) it draws the two kingpin locations (shown as large red dots) and draws a second dotted trace line through the SAI points(Steering Axis Inclination) to the ground.
Scrub radius is a measurement (in inches) of the difference between the tire centerline and the SAI line at the ground. In this image, those lines are 1.81" apart...which isn't good. Trust me, with less wheel offset this number can get a LOT worse too. I'm also not thrilled that the upper kingpin appears to be living inside the tire sidewall at the moment!
Right now, from the looks of things I'm not going to be able to correct the scrub radius simply with good wheel selection, so I'm probably going to have to either buy and aftermarket knuckle assembly with more SAI angle, or modify the one I've got to make the angle steeper.
Anyway.... I still need to got back and verify all of my calculations to insure that I haven't made any errors. You know what they say about v1.0 of a new piece of software!!!
There is a lot of background work going on right now as the crossmember questions are being considered. With a multi-link suspension design in the works, those crossmembers become not just frame supports, but integral connection points for the link ends....so the exact location of the crossmembers needs to make sense based on where the heims are going to land also.
Additionally, I'm still trying to work out the overall track width for the new axles so that I don't end up with a truck that's 90" wide at the tires, AND ideally it should run down the street correctly and be able to make effective u-turns as needed. Portal hubs add a bit more complexity to the front steering geometry so I had to create another "product" to help me calculate things.....so:
I proudly present.... in it's CK5 debut, SCRUB RADIUS CALCULATOR v1.0!!!! [applause]
This program basically shows a cutaway front view of the tire/wheel combination based on tire diameter, width, wheel size and backspacing and then superimposes a vertical yellow line representing the tire centerline.
Next by adding the actual measurements of the portal knuckle (or standard D60 kunckle, this program will do any axle type) it draws the two kingpin locations (shown as large red dots) and draws a second dotted trace line through the SAI points(Steering Axis Inclination) to the ground.
Scrub radius is a measurement (in inches) of the difference between the tire centerline and the SAI line at the ground. In this image, those lines are 1.81" apart...which isn't good. Trust me, with less wheel offset this number can get a LOT worse too. I'm also not thrilled that the upper kingpin appears to be living inside the tire sidewall at the moment!
Right now, from the looks of things I'm not going to be able to correct the scrub radius simply with good wheel selection, so I'm probably going to have to either buy and aftermarket knuckle assembly with more SAI angle, or modify the one I've got to make the angle steeper.
Anyway.... I still need to got back and verify all of my calculations to insure that I haven't made any errors. You know what they say about v1.0 of a new piece of software!!!
bp71k5
3/4 ton status
Not knowing anything about SAI, is the idea that those two lines need to intersect or be very close at the ground?
Yup the distance between those two lines is the scrub radius. Should be a small positive number to minimize steering effort, tire wear, corner jacking with steering angle, etc.
Greg, when you have the bugs worked out, I am gonna need a copy of that Excel file.
BTW, the best way to reduce scrub radius? Buy taller tires.
Greg, when you have the bugs worked out, I am gonna need a copy of that Excel file.
BTW, the best way to reduce scrub radius? Buy taller tires.
my head hurts
BTW, the best way to reduce scrub radius? Buy taller tires.
Not sure I agree with your assessment on that one....
With all other data remaining unchanged in the calculator, the tire diameter that brings me to a 0.0" scrub radius is 56.7" tall.
OK, we both agree that taller tires will help.... but small changes don't make an appreciable difference in this case. The solution is looking more like a one-off set of custom steering knuckles which I'm not thrilled about ($$$$$$). If anyone has a brilliant solution to this one, I'm all ears.
bp71k5
3/4 ton status
That does appear to be a tough one. With your axle centerline now higher than the tire centerline, is it a crazy idea to shim the knuckle (or the C) to provide a small amount of positive camber, and thereby decrease the scrub radius? It would seem a very small camber change there could translate to a pretty large scrub radius change.
Not sure I agree with your assessment on that one....
With all other data remaining unchanged in the calculator, the tire diameter that brings me to a 0.0" scrub radius is 56.7" tall.
Time to start looking for some XMLs. Think of your diff clearance with 52s and mogs.
I don't think it is worth the effort to get zero scrub radius. I bet very few SFA trucks (or vehicles of any kind) left the factory with zero scrub radius. Plug in your data from a previous incarnation of the truck and see what the scrub radius was. Did that scrub radius ever bother you? Do what you can within reason to minimize it, and then move on to something else.
I think you meant negative camber... but yeah, that's something I was wondering too.
Basically if I can pull in the upper kingpin mount by as little as 1/4" to 1/2" it should have a dramatic effect on the scrub value. A few degrees of negative camber up front probably wouldn't be a bad thing to have anyway.
What do you think a "ballpark" value for acceptable would be? Remember, I intend to drive this a LOT on the street, so this stuff does matter more than if it were just a trail truck. I like the idea that positive scrub is generally considered a better problem to have than negative scrub (especially since that's what I've got now).
bp71k5
3/4 ton status
In doing some research on this stuff, I came across the Axletech portal conversions and their FAQ says that they are maintaining a close to stock scrub radius by using 7" backspace wheels instead of 3.5" backspacing. They don't say what the stock scrub radius is, but it does sound like some amount is inevitable.
I wonder if you can shave off some of the knuckle-spindle mounting surface to move your wheel centerline in a little more. I don't know enough about the portals but it's another way to attack the problem vs making custom knuckles.
Actually, I was assuming positive camber added at the spindle or negative camber at the knuckle. I assume either would achieve the same thing?
I wonder if you can shave off some of the knuckle-spindle mounting surface to move your wheel centerline in a little more. I don't know enough about the portals but it's another way to attack the problem vs making custom knuckles.
Actually, I was assuming positive camber added at the spindle or negative camber at the knuckle. I assume either would achieve the same thing?
Not off the top of my head.
Plug some common combos into your excel sheet and see how they compare.
(looks like I was still editing my previous post when you posted.
)
