Chassis Jig Frame Table discussion

[javajoe79]

How much sag do you get in the center of the 20' I beam? We used a 26' tapered ex steel sq.tube light pole and had to put a jack in the center to take out about 1/2" sag.

 Very little at this point. The beam itself is 12" tall and 3/8" thick. We planned for some though so we have leveling screw along it's length to support the middle once it's on the ground.

[Koncretekid]

I have only built a bike jig, which didn't require the same degree of resistance to twisting that a car jig would require. But I beams or the more commonly used wide flange H beams are not good at resisting torque (twisting).  Hollow structural square, rectangular, or even round would be a better starting point.  However, you have a start, so you may be able to box in the beam to make it much better in resisting twisting, if the welding doesn't warp it. Whatever you use, you still need to constantly check it and the frame you are building for level and square.  You can always shim to level, but if your jig is not stiff in torsion, welding up your frame could pull it.

FYI, I met an ex machinist who built an absolutely beautiful Triumph powered special build bike. He said he built it on a piece of 3/4" plywood, reinforced to keep it from twisting.  

Tom
Tom

[Rex Schimmer]

This is the "ultimate" build jig: a floor mill floor plate. This one is 6ft x x22 ft 15 inches thick, cast iron with tee slots. This is what most of the NASCAR guys use. They are amazingly reasonable, usually the price of steel/pound. Probably cost more to have it moved plus once you put it some place it isn't going to be moved.
Rex

[Tman]

This is the "ultimate" build jig: a floor mill floor plate. This one is 6ft x x22 ft 15 inches thick, cast iron with tee slots. This is what most of the NASCAR guys use. They are amazingly reasonable, usually the price of steel/pound. Probably cost more to have it moved plus once you put it some place it isn't going to be moved.
Rex

That is cool Rex. Our problem in my area is that we have NEVER had any manufacturing so this type of stuff is unobtanium. 

[javajoe79]

 No more progress yet. We are moving shops soon so we mainly wanted to get this thing mobile. We will be adding braces to stiffen the setup as well as connect the outriggers and add leveling screws to the outriggers.

 Keep up with the pics and suggestions.   I will have more pics when we make more progress.

[Peckerwood]

 I use 2 x 4 3/16 tube with a 2x3 spaced under as in a space frame chassis, rectangular shape.

 There is no sagging.

 I use a Starrett square .0005 in a foot increments on the bubble.new app. 600 dollars.

 You cannot use a carpenter square they are not accurate enough.

 If it is not ridged and square and you have to use leveling screws to jack it into shape it is not going to be satisfactory.

 If you put a high precision square and level on what you have I think you are going to be unhappy with what you have.

 I have been building machines and fixtures for 40 years, you cannot do good work without good tools.

          J Y/B

[Peckerwood]

 
  I said Starrett square, I meant level, you also need a good machinist square.

              J Y/B

[Seldom Seen Slim]

Howdy, Peckerwood. I burn lots of your namesake fuel in our wood boiler.  But that's beside the point.  I don't see your location in your avatar spot.  Would you please be so kind -- and let us know where you're located?  Thanks.

[Peckerwood]

 
 Slim, I meet you at B Ville a few years back, I was with Courtney Hizers group, Buick C/BFA car no. 80.

 I am in NW. Ga. Adairsville not far from Courtney,s place Rome ga.

 I knew Hizer for 45 years there will not be another like him.


 Additional info on jig.You can have a steel plate Blanchard ground at a reasonable cost.

 In Atlanta Withers Machine can do a 12 foot plate, the will furnish the steel if you want.

 It does not take long to Blanchard a large plate, is not perfect but normally within .010 on a
 10 foot plate.

 I used them for machine bases in the past.You can get same day service, these are monster machines.

 Even a 3/4 inch plate needs some reinforcing  on the back to keep it from sagging.

          Jim Youngblood aka Peckerwood

[Seldom Seen Slim]

I think I've put your location in place for you.  As for meeting you a few years ago -- gee, I think I remember -- but the years do sorta add up and the memory gets fuller and fuller, too.  Best wishes and thanks for signing up for the forum.

[Rex Schimmer]

In So Cal Shaffer Grinding can blanchard really big stuff. If you happen to have something done be sure to do both sides as if you only do one side it can cause the plate to bow from the inducing and relieving of stresses. Try not to do cold rolled plate on one side only as it will look like a potato chip when you're done.

Rex

[floydjer]

As much fun as it would be to have a jig that cost more than my house..................I build on a shop -made table.    16 ft. long, 40 in. wide and 36 inches in height , 2X4 3/16 tube with cross tubes  spaced evenly . Around the periphery are 1 1/2 angles placed ( you guessed it) 1 1/2 " down from the top w/ leg facing inboard.  1 1/2  sq. tubes drop in place from above and can be located anywhere along the length.   Large steel casters on the corners ( do yourself a favor and make it steer from one end) and leveling jacks in the legs. Voila`..Made many a hot rod frame on it .

[tauruck]

"( do yourself a favor and make it steer from one end)". Right, mine still doesn't but I don't move it much. Mine is sort of similar to what you describe and the cool thing is that you can build all sorts of other cool projects on it as well.

[Stainless1]

"( do yourself a favor and make it steer from one end)". Right, mine still doesn't but I don't move it much.

I find swivels on all the corners is sometimes a really good thing...  two of those should have swivel locks to you can make it steer from one end when you want as well.
The cart I built for the little car has these
http://www.northerntool.com/shop/tools/product_363217_363217
 

[javajoe79]

We got our casters on craigslist for a killer deal. They all swivel and lock. So far it rolls real nice.