Cheap Scale Option...

SkyHog

SkyHog

Touchdown! Greaser!
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Looking to make some sort of scale setup Super cheap...

Any homebuilders have a setup they can share?
 
I feel like Craigslist may be easier/as cheap as trying to make something, depending on how heavy this scale needs to be.
 
It's for my race car, but let's pretend it's for an airplane I'm building, since it's the same concept (except I'll need 4 datapoints, not 3). I need to grab the 4 corner weights for setting cross weight.
 
Hmm, you could use bathroom scales, and if they won't weigh heavy enough, you could rig a set of offset contact brackets and do the math for the actual weight.
 
How precise of a number do you need? Are the tires on the car? Get the area of each contact patch from the tires, and multiply it by the corresponding pressure in each tire. (did that little experiment in 6th grade once).
 
Sac Arrow said:
Hmm, you could use bathroom scales, and if they won't weigh heavy enough, you could rig a set of offset contact brackets and do the math for the actual weight.
Click to expand...
I tried bathroom weights - unfortunately, the wheels are big enough that I can't read the number on the scale when the car is on it. I was going to construct some sort of levered system to use instead, but figured this has to be a problem that airplane builders face as well.

Purpose built scales for this cost around $1,000, which is a bit hefty for a hobby.
 
Try this. I wrote it a long time ago and have not tried it lately. If you put in corner weights it will calculate the percentages and total for you. Put in the total and your desired percentages and it should calculate the corner weights you need.
 

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EppyGA said:
I used something like this

http://www.rubbermaidcommercialproducts.com/c395/c55/c272/p250s-briefcase-receiving-scale-p1963.html

Mine had remote readouts that I built stands for. Then you use a spreadsheet to put the numbers in and calculate total weight left and right side and cross.
Click to expand...

Only does 250lbs. I'm going to need 350 or so per corner...dang. Also, price is still a bit high - for 4 of those, I'm still looking at like $600.

EppyGA said:
Try this. I wrote it a long time ago and have not tried it lately. If you put in corner weights it will calculate the percentages and total for you. Put in the total and your desired percentages and it should calculate the corner weights you need.
Click to expand...
Thank you! I wrote something similar. The problem is actually getting the weights to input...
 
vkhosid said:
How precise of a number do you need? Are the tires on the car? Get the area of each contact patch from the tires, and multiply it by the corresponding pressure in each tire. (did that little experiment in 6th grade once).
Click to expand...
I thought about doing something like that, but I need to be a bit more precise...
 
Why not buy your friendly A&P a case of beer and use his or her scale set?

Rich
 
vkhosid said:
How precise of a number do you need? Are the tires on the car? Get the area of each contact patch from the tires, and multiply it by the corresponding pressure in each tire. (did that little experiment in 6th grade once).
Click to expand...

The math there is a little more complicated than that. It's doubtfully linear anyway. The only way to practically make that work is to create a table of contact patch vs. weight (I would do rim height above pavement instead) at a specific pressure, at a range of temperatures, and create a graph. You could probably do a curve fit routine and create a function if you wanted to.

But then you'd still need the scales for calibration....
 
Yes, but you can always stack the scales and just add them up, right? :rolleyes::p:D:D
 
SkyHog said:
Only does 250lbs. I'm going to need 350 or so per corner...dang. Also, price is still a bit high - for 4 of those, I'm still looking at like $600.


Thank you! I wrote something similar. The problem is actually getting the weights to input...
Click to expand...
They make a 400lb scale. Buy one and make two ramps that have two cutouts on each side for the scale to sit in. Make three pieces of wood to fit three of the cutouts. Roll the car up on the ramps with the scale in one spot. Get the weight roll the car forward or back and move the scale to another wheel. Repeat until you have all three weights.
 
RJM62 said:
Why not buy your friendly A&P a case of beer and use his or her scale set?

Rich
Click to expand...
I will need to repeat it multiple times in a weekend, every weekend during the summer and fall. That's a lot of beer.
 
I bought big bathroom scale which reads up to 700 pounds for weighing airplanes. It is large enough the display isn't hidden behind the tire. It even has a audible readout you can listen to the weight reading. I don't recall details, but I'll try to remember and look at it see if I can remember where I bought it. IIRC, it was around $70, but I got it on sale for a bit less.
 
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