Water level accuracy for squaring a car frame

[stryped]

I have a 1968 Mustang that I bought at auction from my grandfather's estate it is almost completely apart and I want to rebuild it for him has sadly he ran out of time, I have a reproduction manual from 1968 with frame dimensions in it and some of the dimensions car vertical to a datum line.
I have thought about lasers and things from the local hardware store but to be honest when reading the reviews it seems like there is a lot of variation in them I wondered if a water level would be accurate and if so how accurate I was thinking of using it to level all four wheels and to possibly establish some sort of datum line as well as possibly leveling I beams that I would use to make a sort of cart for the car to ride on just lots of ideas in my head right now so basically my question is is one of those electric water levels you purchase accurate and if so how accurate is there any way to make them more accurate it seems I read they can be accurate to with one sixteenth of an inch but I may be wrong any help is appreciated I just want to make sure this car is square and okay before proceeding

 

[CWatters]

DIY water in a tube levels can be very accurate. Main issue is the miniscus caused by surface tension making it harder to see exactly where the surface is.

A standard check for a spirit level is to turn it around and see if the surface is still level. You could do that by using a water level to make two marks say 10 foot apart on a wall then swap the ends of the tube over and see if the marks still apear to be level.

 

[Ranger Mike]

see these posts o n the Mechanical Engineering forum. Race Car Suspension class
squaring the car page 14 post # 270, page 27 post # 479,
Stringing the car page 14 post # 269
page 15 post # 293

one big thing to check before you do anything...make sure your garage floor is flat.
I once was bench marking a race car in a new garage...the owner had a nice floor drain so we could hose off the race car mud and dirt from the track.
The floor was sloped like 1/4” per three feet...no way could we use it.

 

[Baluncore]

https://www.physicsforums.com/threads/race-car-suspension-class.326355/page-14#post-3731716
https://www.physicsforums.com/threads/race-car-suspension-class.326355/page-14#post-3732057
https://www.physicsforums.com/threads/race-car-suspension-class.326355/page-15#post-3748276

page 27 post # 479, there is a problem. Post #479 is on page 24 not page 27.
https://www.physicsforums.com/threads/race-car-suspension-class.326355/page-24#post-4081365

 

[stryped]

I read that using windshield washer fluid in a water level is more acurate due to surface tension. Is this true.

 

[Ranger Mike]

Baluncore- thanks for catching that..lack of coffee when i wrote it in error

 

[Nidum]

Find someone with a dumpy level and ask them to survey your garage floor . Record the levels at a selection of useful places for future reference .

Use packing or adjustable height stools to level any work in progress .

Optionally skim the garage floor to true level or set in some metal plates to true level .

 

[OldYat47]

You can use a spirit level easily to do what you want. Make two simple stands with well-marked yardsticks on the vertical sections to hold the tubing. Keep one stand stationary at all times. Now you can shim or jack the chassis until four data points are level. Compare the other data points to see if they are at the correct level. The best way to check for out of square is with a steel tape measure, measuring diagonals.

A little soap is all you need to reduce the meniscus, but that sometimes causes bubbling problems. I just use tap water with a little food coloring and read the bottom of the meniscus. Chassis are not that perfect ever, slight error in meniscus reading is not an issue.

 

[Jupiter6]

I have a 1968 Mustang that I bought at auction from my grandfather's estate it is almost completely apart and I want to rebuild it for him has sadly he ran out of time, I have a reproduction manual from 1968 with frame dimensions in it and some of the dimensions car vertical to a datum line.
I have thought about lasers and things from the local hardware store but to be honest when reading the reviews it seems like there is a lot of variation in them I wondered if a water level would be accurate and if so how accurate I was thinking of using it to level all four wheels and to possibly establish some sort of datum line as well as possibly leveling I beams that I would use to make a sort of cart for the car to ride on just lots of ideas in my head right now so basically my question is is one of those electric water levels you purchase accurate and if so how accurate is there any way to make them more accurate it seems I read they can be accurate to with one sixteenth of an inch but I may be wrong any help is appreciated I just want to make sure this car is square and okay before proceeding

Just to get a few things clarified. These cars were unibody with sub-frames in the front. How far is the car torn down?

 

[stryped]

Is there a way I can post a graphic of the blueprint dimensions so as to better understand the best way to do this? Again, I appreciate the help!

 

[Baluncore]

Make sure the picture is compact and in a standard format such as .jpg or as a .pdf
Drag and drop it onto the edit window. It will be attached to that post.

 

[stryped]

This is similar to the blueprint to my 68. What would be the most accurate way for a guy at home to check these measurements? Before the measurements are taken, do I need to level the car? If so, do I just put jack stands on the rocker panels, then level the rocker panels. What do I use for the datum line?

I really appreciate the help. Unfortunately I am a little anal and I want to get this as perfect as I can and still do it myself.

 

[Ranger Mike]

Make sure you have a true flat surface ( floor). Once you have this raise car and measure rear spring perch bolt hole ( the front one) so it is 6 1/2 inch from the floor. Actually , you want to measure the "center point" of the bolt hole to the floor. Alternative is to measure the actual bolt hole ( it may be 1/2") find the radius and re-calculate. In this case , the correct distance from the floor to the " bottom edge" of the bolt hole would be 6 1/2" - 1/4" = 6 1/4" ).

Measure the other side to make sure both front bolt holes are same. Next adjust the front cross member "B" to be 12 1/2 inch. If the frame is straight you should have 6 " at the "X" location. You can check the remainder from there. Production cars are off as much as +/- 3/16" as noted in above print ..its sheet metal so do't get to worked up about it.

 

[stryped]

Make sure you have a true flat surface ( floor). Once you have this raise car and measure rear spring perch bolt hole ( the front one) so it is 6 1/2 inch from the floor. Actually , you want to measure the "center point" of the bolt hole to the floor. Alternative is to measure the actual bolt hole ( it may be 1/2") find the radius and re-calculate. In this case , the correct distance from the floor to the " bottom edge" of the bolt hole would be 6 1/2" - 1/4" = 6 1/4" ).

Measure the other side to make sure both front bolt holes are same. Next adjust the front cross member "B" to be 12 1/2 inch. If the frame is straight you should have 6 " at the "X" location. You can check the remainder from there. Production cars are off as much as +/- 3/16" as noted in above print ..its sheet metal so do't get to worked up about it.

I think that is one of the problems. My floor is not flat. (I have a drain in my garage and the floor slopes toward that.)

 

[jfoldbar]

im a builder so i have a lot of practical experience with leveling things

a water level is accurate provided the water and tube is clean( do not put anything in water except mayby food colouring), has no air bubbles, and the temperature is no more than 35 degrees celcius.

a standard spirit level would be accurate to about 10mm over the size of a typical garage, if it is new. expensive onses are more accurate than cheapies.

as nidum said, the most accurate way, and the easiest, is a dumpy or laser level. in a small space like a garage, a dumpy has a slight accuracy over a laser, provided lighting is good. the receivers on lasers are accurate to about 4 mm over 10 meters.
if the car is in the center of the garage, the receiver will be slightly confused by the metal and give a slightly inaccurate reading.(though steel is better than aluminium) this of course, does not affect a dumpy.

 

[Never to Old]

Seems to me you are getting all kinds of advice on how to do things.. Mostly good honest advice but doesn't do much to help your situation.. That said, I may as well throw my 2 cents worth in also excepting I've probably got a little more experience at this than they do having built 5 Pro Street cars and two of my own, door slammer, drag race cars.. First thing you'll have to get used to is the fact that unless you want to spend a pile of money you will never have a flat garage floor to work off of.. Period... The best you can hope to do is set the car flat and level AND securely supported so it doesn't fall off of the stands.. A friend of mine lost his father that way,I'll not give details.. You'll need a solid means of support for the front and rear, a fabricated support with a wide base that BOLTS to the frame/body.. Leveling can be done by shimming under this support stand.. Use just a plain old Bubble Level (a good one, no cheap junk) across the rocker panels, side to side, and along the length of the rocker panel for front and rear.. Do your back a favor, make the stands tall enough that you are not bending over to work on the car.. After you have it leveled place a pair of stands somewhere mid body for general support.. As far as making all sorts of measurements from a datum line goes, don't drive yourself crazy with it... Unless the car has been wrecked you'll have to trust the factory knew what they were doing when they built it, if its been wrecked take it to somebody with a frame machine and let them pull it into shape, you can't do it.. I'm only offering my input to hopefully keep you from killing yourself by pulling the car off of the inevitable cheap jack stands everyone thinks will save them.. Do not get under that vehicle thinking you can pull and pry on it while up on 4 jack stands.. Having the car up of the ground, flat and level, make it worlds easier to work on suspension, set the engine and trans in place, do the wiring and such.. Worry about the doors and deck lids after you have it back on the ground on 4 tires.. Sorry I get a little wordy about safety and how to properly support your project car but the sight of my friends Dad has stuck in my mind for 40 plus years..