chassis jig design

[GMracer]

for example (not mine) just where I got the idea, from there I would put the stock frame on it, jig everything up then pull that frame and build the tube chassis. Just don't want to use 1/8" if people are going to think it's way to thin, just trying to do what's best for a small fortune since it's a one time table, plus I don't have anywhere to store it once I'm done with it.

[Mathius]

Just read something somewhere (maybe PHR?) about Project X, the 57 Chevy GM is building. They had a chassis jig that I thought was very unique. The jig covered the whole floor, and had tracks and you could attach different fixtures within the tracks and move them around. The track held everything in place, but the point was, you could move the fixtures around to wherever you needed them.

There was a name for the type of jig, but I can't recall. Maybe you could build a smaller scale version if you could get a good look of how the tracks work?

Try a search for Project X. Might help.

Mathius

[WGSPEEDSHOP]

heres another one

[Jim Nilsen]

I just saw this thread for the first time and can say that the only important factor is that everything you measure off of or level up to is in the same plane.
I made my own jig out of 2 x 3 rectangular tubing and just used a welded nut and some bolt to level with. Yes I had to check it from time to time to make sure it was level because my floor would shift but it was more than accurate enough as long as I used the same reference points to level back to.

On another note I read an article years back in Car Craft I think that showed how to do a tube chassis and suspension install that just used a wire strung through the car at the center and all measurements started from there. It worked well and it kept it all in the same plane even if you were to have it on a rotisserie or stand it on end.

I also used a laser level for ceilings when I put my quarters on because I could measure up to the red line where it was impossible to measure from the fixture below. This made it very easy to do and you could do it with shims and a tape measure to level the car to start with and you can recheck everytime you start in about 5 minutes. I actually could have done the whole car that way if I would have wanted to. You just can't rely on a bubble level to install things if you are not level to the ground/world.

Hope this gives others a differnet perspective of some less expensive but more time consuming ways to accomplish the same thing. A good laser level can be bought for about $200 or rented from any rental place. Just ask for a drop ceiling laser and you will get the right tool for the job. Sears has a few that are even less expensive now that will also do the job well.

You can go to my cars site and see the basic fixture in some pics. The nice thing was that I could permanently weld my supports in and know that they didn't move. Now I have the extra tubing to build something else someday if I want and it doesn't take up space since it could be unpinned ( dowels so it would be stable) unbolted and stored away.

Goodluck and have patience

[Samckitt]

Hey Nick,
Got any more pics of the Monte on the table?

[WGSPEEDSHOP]

Hey Nick,
Got any more pics of the Monte on the table?

heres a few tell me whatcha think.

[SVTforme]

I just noticed this thread - what a coincidnce as I started build one for myself over the weekend. The goal here was to build something I could use in my garage, and something that could be built on a budget. I ended up making my own since it was clear it would be very expensive to purchase one complete. Since myself and a friend are building identical cars, and both have modern suspensions, this was the best way to make sure everything is in the correct place. This will also make car #2 much easier to set up quickly.

After looking at a couple of other designs out there, this is what we came up with. After looking for some steel, and realizing this would not be cheap to make, a wanted add was placed on Craiglist for steel (this past Thursday). On Friday we received a call from someone who had just taken down a billboard and was looking to sell the material (used of course). Saturday morning the steel was loaded up and in our possesion. The best part here is the budget. The only thing required now was time.

Cost:

~100ft 3"x3"x1/4" steel: $100 (Leftover steel will likely be sold to recover some cost)
Leveling feet for base of legs 5/8x11 & nuts for legs: $70
Paint and misc shop supplies: $35

Total cost: $205

Here is the initial concept in CAD:



Saturday morning after picking up steel.



Sunday just before calling it quits (helps to have access to a surface plate to make sure our version is perfectly flat):



I have not really posted much online as I have not really done much actual fabrication on the car to be able to show major results. I will be posting more often once things get up and running. Now that I almost have the chassis jig completed, things will start falling into place. Most of the time to date has been in collcting parts.

[David Pozzi]

SVTforme, Welcome to our forum! Hope to hear lots more from you.

I have no jig table and haven't really worked on a chassis on one, I've built lots of farm equipment on the floor though! But before taking that jig home, I'd weld some triangulating braces out of smaller tube to hold it flat. A better triangulation would be looking at it upside down in the photo, I'd run a framework parallel to the frame around the top of the legs sticking up forming a box, then add at least one diagonal brace per "box" section.

I would have made it slightly taller in case I needed to get underneath, plus with bracing, you will lose even more room. I wouldn't make it wider than the average car frame rail width, then use cut pieces of tube clamped across the jig to support the chassis or body.
David

Here's a link showing a jig table: http://www.circletrack.com/techartic...ech/index.html

[SVTforme]

Thanks for the input - I really appreciate it!

The design of this was based on the smaller version of the one you are referring to (Uni-Jig) as shown here. http://www.unijig.com/ . Is the extra bracing for stiffness to prevent the structure from parallelograming? What you mentioned will definitely stiffen up the structure, I am just trying to determine how much is enough.

The overall height of it was set to around 18", which should give plenty of room to get under the car to work on it (hopefully).

[David Pozzi]

The one in your link appears to have large rectangular main tubes which are more rigid. My worry is the smaller tube (2" square?) you are using may not stay level when on the floor. We bent a similar sized tube just by welding a bunch of brackets on one side. The brackets were about 6" apart but the tube was heavy wall 2X3 tube and you could see a definite bow in it. Just welding on the legs can distort the tube and it won't show up until you release it from being clamped, it will spring back.
The "Y" shaped braces shown below are a nice addition. Personally I"d do something similar but minimize welding area and heat to reduce the of smaller material and only tacked on to the sides of the legs and main tube. Running a brace along the floor connecting the legs (left to right in the photo) would also help along with diagonal braces, but reduce access room underneath. 18" height sounds pretty good. The legs need some kind of height adjustment or you will need to shim them to adjust to the floor.

I altered the photo to show two ideas.
black lines running left/right along the floor are braces you could add to the legs, this forms a "box" section along with the legs and top rail.
1.Then the diagonal line on the right breaks the box into two triangles, this is much stronger and stiffer. Add another on the left side as a mirror image - have it going up and out to the left from the center leg, this forms a truss of sorts, quite strong/stiff.
2.The alternate for more access room would be on the left, two diagonals, three triangles, I kinda like this one the best. The braces could be 1 1/4" square or round tube.

IF the legs are bolted to the floor, then they are constrained from moving and the whole structure is much more rigid, the original frame seems to be intended for that method of installation. What I'm saying is, if you are not going to bolt it to the floor, then more bracing is going to help a lot. I'm not too worried about diagonal bracing when looking down from above, but some diagonal pieces of tube or rod would help if it seemed to be needed. If you do the braces I drew in, then you don't need the braces they are using.

[Jim Nilsen]

I didn't have a lot of room at the time I built mine and I decided to make my jig a bolt together design and used dowels to locate the braces. It was nice to be able to remove the braces once some of the tacking was done to make more room to get comfortable. I weld a lot better when I can get comfortable.

$200 is a great deal for that much steel, that is what I paid for lighter gauge tubing a long time ago before the new increases went wild.

I did not bolt mine to the floor and had to relevel everytime I did something critical but it would only take about 5 minutes to recheck once the routine was down. You do not want to bolt it to the floor unless you have a slab of concrete that won't move, mine changed with the seasons as the foundation expanded and contracted. I also had a crack in the floor that would let me know when it was moving.

I also made mine bolt together so that it could be assembled square and not worry about distortion from welding on it. It also makes it more universal. I bolted to my suspension mounting points which are not the same for another car if you want to reuse the jig and made the supports with a specificaly welded bolt in brace. It wasn't very long working on the frame and I could have put it on jackstands sooner but it was supported at points that allowed a lot of the work to be done before I had to take it off of the jig.

One other thing I did was make the leveling bolts spaced every 2 ft, but my base was right at floor level which made it a bit harder but I did not have any way to raise the car more than 22" anyway without hitting the support beam in the garage. I also had no way to get it out from under the car once I was done and unbolting it made it as easy as putting the car on jackstands and removing the jig from under the car piece by piece. this is an important thing to think about, you don't have a forklift or hoist to move a car around. Do you?

There is a lot to think about before you get carried away and the biggest thing is to keep it simple and just check it more often if you have to. Remember LEVEL is LEVEL no matter if it cost $200 or $20,000 and the car will never know the difference. And it has to just work for you since you won't make a living with it !

Goodluck and I hope some of my obstacles that I had to work around help you design what is best for you.

[gt1guy]

My problem was I needed a body cart, a surface plate, and a chassis jig, but only have room for one. So I made one that I could do everything on. I made mine out of 2x2x.125"wall. Topped it with 3/8"plate. It's 10'x6' and I wish I had made it longer. It has a line down the middle I pull all my measurements from. When I bought the 10x6 plate, it had the outside edges slightly rolled from the milling process as all plate does. I cut the plate down the middle, flipped the halves around, and when butted back together, had a nice straight line down the middle. Beat having to have it machined in.



I was going to put screwjacks every couple feet, but found it didn't need it. Just ended up with them at the four corners, and in the center. And even the center one I don't really use. If I crank on the center jack the whole thing lifts. And it's flat and true. I think I went overkill on the 2x2 frame, but it does what it's made to do very well. Total weight came in around 2500lbs. I think the plate is just under 1000lbs

I mounted the gutted shell to the table (C/L of body over C/L of table, plumb bobs for square, set ride height,etc.) and did my layout of the bottom part of the chassis on the plate. This works out great because if I needed a measurement from the body, it was just above when I'm doing the layout. Welding isn't a problem because the body is high enough not to be in the way.



Here's a pic of where I'm at now. The lowest part of the chassis is set at ride height with the body. I'm doing the rest of the spaceframe out of round tube, just tacking it. When it's time to weld everything I'll lock it back down to the plate.



I've been really happy with it so far. With the castor's, I think I have around $1000-$1100 into it. I do think if I was putting a lot of weight on it, I would need to add more screwjacks.

Kevin

[SVTforme]

Kevin - that is quite the setup!

After doing some welding, I did decide to add some cross braces, just to ensure it does stay true. Amazing what steel will do with heat! The tubing I am using is 3"x3"x .25", so it is fairly stiff. The cross bracing is mainly to ensure the structure keeps its shape after welding, and will provide more stiffness to the system (although not the intent). I will meet you halfway with bracing David . The way I can still get the creeper under the car with no issues. It also worked out with some extra shorter 2"x2"x3/16" material I had on hand. The braces will be stitch welded on, and then the legs will be fully welded after that.



I did run FEA on the original piece, and even if I load up the jig between the posts will 4000lb (1000 each spot), the deflection is a fraction of a mm, and this also takes into account that it is not bolted to the floor and is free to pivot about the floor. I will have to re-run with the new braces.

I have it almost done - I will have to post more pictures. I am hoping to have this under my car within the week.

[David Pozzi]

That looks good.
I'm not so concerned about load, but just the welding heat from welding on the legs causing warping of the main tube. I'd go very easy when welding on any braces, use low heat and just skip weld them on. The braces don't need to be as thick as the main tube.
David

[SVTforme]

Almost there.. there was minimal warping with this method, although there was a bit on the short overhanging end pieces. Will have to reverse this by some heat and force on the ends. Nothing major though. Had to brush up on my MIG skills as I have only been using TIG for while now. TIG would just make the warping much worse.

The braces are thinner walled than the main pieces - just extra material I found sitting around. Should have this up and running under the car within the week.. can't wait. The Carr-Lane leveling feet (part CL-8-SLF) work perfect.



Also set this up so I can put an 1" thick or so sheet of plywood in between the braces to drop the plumb bob on. A 4x4 sheet will fit exactly in between the two middle sections.

[David Pozzi]

That came out very nice, but please paint that thing!
I need to build one.
David

[SVTforme]

No worries there. In a couple of days once I get it back home it will be Miller Blue to match the welders .

I debated back and forth on whether or not to build it, but glad I did. The steel used to be a billboard on the side of the road and someone posted for sale on Craigslist. This helped to make it cost effective. The adjusters were expensive but work excellent and well worth the cost. Not sure what I am going to do with the jig when not in use, aside from having it take up valuable room . Guess that means I will always need a project car on the go.

Hopefully the next post I have will be with a car bolted to it.

[KillerWolf]

Hey guys,

I'll get some pics. up, but I purchased 8 adjustable jack posts (for leveling structural members @ $20 each) & afixed them to the floor w/ concrete anchors. You can put them wherever you need them & they are infinitely adjustable. You can get the car completely level, front to back & side to side, and then tack everything in place to assure nothing moves. It's a nice, simple way to ensure that everything is locked in place before cutting/welding. As I said, I'll get pics up soon.

[scotzilla]

took a little longer than expected- steel is rediculous right now- Il ad fixtures as i can afford them

[scotzilla]

we basically made adjustable legs out of 4x4 1/4 wall which was bigger than needed but we got a deal on it. Then found those adjustable feet on craigslist for $75. The casters are rated at 1400lb a peice and were picked up in a catalog for $100. At first we welded the center leg on but have since cut it off since it bottoms out when you push it in and out of the shop. To make sure the I beams were on the same plane we used our fab table which we thought was flat until the machinist next door let us borow his 8 ft straight edge. After about 5 hours of shimming and adding alot more bolts and shimming some more we finally got it flat and level. THe next hurdle was both i beams were warped. If i had to do it over i would have bought some more 4x4 for the top rails. I wanted to use i beam since it makes clamping things to it easier. Anyway we started with the straighter of the two i beams and tacked it to out fab table and used a portapower and ratchet staps to true it up. We welded the center leg to both i beams and then spent another 5 hours tweaking and muscling the send i beam true to the first. Its not perfect but within 1/16th of an inch. At this point its a good table top to start with. I picked up some 2x6 1/4 wall to lay across the i beams under the wheel base, as well as some huge c chanel my buddy had at his work to make some spindle fixtures. As money permits i would like to plate the surface and have a fixed centerline like the one pictured above.

Thanks to all who posted pics and design ideas. Ill post some updaes as we add to it