Nook balancing a automotive has been a kind of issues that appeared off-limits to the common automotive DIY fanatic.
You’ll find a variety of digital scales from a velocity store like Summit Racing; nevertheless, a ‘first rate’ set will set you again a minimum of $1,000, and a higher-quality set will value double that.
You should use the lavatory scale hack, the place you jack the automotive up and decrease it on a set of low-cost lavatory scales. I even tried this again in 2020 with Mission Tough, my ER34 Nissan Skyline GT-T, and had… reasonable success.
To do that accurately, you have to guarantee you might be engaged on a wonderfully flat floor. The automotive must be as degree as doable whereas on the scales – i.e., on some kind of platform – and also you want a option to chill out the arms after jacking the automotive as much as transfer the scales into place.
It’s fairly the dance, and there are a number of variables the place issues can go unsuitable. Certainly one of my scales broke as a consequence of going far past the utmost weight restrict of 130kg (286lbs).
So, measuring the load in any respect 4 corners, making any changes, and having to carry out the entire circus once more made this method removed from sensible. It appeared like devoted digital scales have been nonetheless the one viable method.
Or Is It…
Quick-forward a couple of years, and I found a YouTube channel referred to as SuperfastMatt. Matt’s movies are as humorous as they’re insightful, and one referred to as I Invented a Higher Approach to Weigh Your Automobile. And it’s Cheaper, Too. discusses how you need to use leverage and a little bit of math to calculate the load at any given nook.
You’ve got a supporting block through which a beam rests on. The supporting block is a ‘X’ distances away from the lavatory scale. You’ll then place the tire on the beam, and that weight transfers throughout the beam to the size. The burden can be considerably smaller, which shouldn’t max out the size. If the space from the supporting block and the space to the size, you may calculate the precise weight with the worth proven by the size.
Seeing that I nonetheless had my analog scales from the primary try and a workable platform I designed for aligning automobiles, I figured I’d let my inside engineer again out to play and provides this a shot. Earlier than going full ship, I made a decision to check it on a small scale with an previous battery from the household Honda Stepwgn.
I first weighed the battery to know my goal— roughly 9.8kg (21.6lbs). The decision on these scales depart quite a bit to want.
I subsequent created a platform that will have the beam degree with the lavatory scale. I recorded the size (92.2cm). We’ll name this ‘L’.
Then I positioned the battery on the beam and acquired a studying of two.9kg (6.4lbs). Nice! I’ll name that ‘Fa’ for now. Now, to calculate the distances.
In contrast to the drawing, the pressure of the battery isn’t a single level on the beam, thus I made a decision to take the common of utilizing a distance from in entrance of and behind the battery – one closest to the size (L2) and one closest to the supporting block (L1). I might subtract the 2 and divide it by 2.
(L2-L1) /2 = Lm
(39cm-15.5cm) / 2 = Lm
11.75cm = Lm
With what I’m calling ‘Lm’, you may subtract that quantity from L2 and get the battery’s ‘heart’ level of pressure. I’ll name this worth ‘Lf’.
L2-Lm= Lf
39cm-11.75cm= Lf
27.25cm= Lf
With Lf now decided, I can divide it by the whole size of the beam. If the space relative to the beam, you may divide that quantity by the load on the size to calculate the load. I do know it’s getting a bit wild right here…
Fl=Lf /L
Fl=27.25cm / 92.2cm
Fl=.2955
I realized this on the full-size check, however I attempted to maintain as many numbers after the decimal place as doable to extend accuracy. It does make a distinction. With Fl, we will lastly calculate the load of F.
F= Fa / Fl
F= 2.9kg. / 2955
F= 9.81kg
That is an error of 0.10%, which greater than proves the accuracy of this mathematical check. With this stable proof of idea, it was time to scale up.
Full Steam Forward
With Mission Tough able to go, I made a decision to do an alignment, as I might use the identical platform rig for the nook balancing.
For shaken, I needed to reinstall some OEM components, which threw my alignment out of whack.
Bringing the automotive to my home from its storage spot was one of many sketchiest drives of my life. I adjusted my laser degree to degree the platform with shims.
I used to be now able to nook stability Mission Tough. I acquired my lavatory scale out and ensured the beam and platform have been degree…
…And instantly bumped into an issue. Though I had calculated that if my bar have been 184cm lengthy, I might have loads of area to drive on the beam and never max out the lavatory scale, the load deflected the beam a lot that it touched the bottom. Two extrusion bars weren’t going to work.
However how about three? Seeing that I had additional extrusions from numerous initiatives at that very same 184cm size, I made a decision to attempt that earlier than reducing the beams to a smaller measurement. I used to be nonetheless afraid that if I had reduce the beams too brief and pushed too far on the beam, it might max out the size, and I’d threat breaking them.
Even with three beams in place, they nonetheless bowed like loopy. This wasn’t going to work. I then remembered that I might transfer the size nearer to the automotive and use a wedge piece of wooden for the beams to relaxation on to switch the load, successfully shorting the size of the beams. All I wanted to do was zero out my scale and take a look at it.
With my present size (L) now shortened to 108.3cm from 184cm, the beam hardly deflected and will proceed with the experiment. The studying on the size was 42.5kg (93.7lbs) (Fa).
It was now time to calculate the varied lengths as I had completed with the battery. Nevertheless, it was tougher to inform the place the contact patch was on the beam. I used a small sq. ruler and slid it beneath the tire till it couldn’t transfer anymore, after which marked the beam. I did this for each side to get my L2 and L1 calculations.
(L2-L1) / 2 = Lm
(20.5cm-1.1cm) / 2 = Lm
9.7cm = Lm
It wasn’t till I completed measuring every part that I spotted there was a better option to decide the tire’s contact patch…
You possibly can press a bit of flat scrap wooden wherever towards the tire and mark out the L2 and L1 of the tire contact patch utilizing the identical methodology. Amazingly, this methodology matched my numbers for the entrance tires (9.7cm) however was barely larger within the rear (10cm). These could be the Lm values used within the calculations.
Seeing that I can straight calculate Lm from the tire contact patch, my new equation is now this.
L2-Lm = Lf
20.5cm -9.7cm = Lf
Lf = 10.8cm
We now take Lf and calculate the pressure relative to the space on the beam.
Fl=Lf / L
Fl=10.8cm / 108.3cm
Fl=.0997
Once more, maintain as many locations as doable within the calculations. I saved your complete quantity on my calculator (0.099722992). Then, we will calculate the pressure of the automotive at that nook.
F= Fa / Fl
F= 42.5kg.0997
F= 426.18kg
And identical to that, one nook is finished! Subsequent, roll the automotive again a bit, transfer the size to the subsequent tire, drive up, and crunch these numbers.
When you get the dangle of it, every nook takes about 5 minutes. After all, in case you have a number of scales and beams (I used to be nonetheless cautious and determined to not get extra beams to do that), you can do that complete course of in a single shot.
Listed below are the values that I got here up with after all of the calculations. In line with the shakensho, my Skyline ought to weigh 1,460kg (3,218lbs). I’m undecided how they acquired that quantity (moist, dry, full tank of fuel, and many others.), however I shouldn’t be too far off.
Consider a brilliant light-weight (learn: barely flimsy) FRP entrance hood, no spare tire, and some different bits right here and there, and the whole calculated weight is fairly rattling shut. Ideally, I might take Mission Tough to a spot the place I can drive and weigh the automotive, however that should wait till it’s handed its shaken inspection.
What can we do with this newfound details about Mission Tough‘s stability? A nook stability exhibits your car’s weight distribution, which may then be manipulated to optimize dealing with. For many who are lifeless critical about getting one of the best lap time, you’d manipulate this distribution by bodily eradicating weight or including ballast in strategic areas to get nearer to that ‘preferrred’ 50/50 distribution entrance to again and left to proper.
We are able to manipulate how a lot weight a nook receives by elevating or decreasing it. Nevertheless, as one motion impacts all the opposite corners on the identical time, it isn’t doable to alter the entrance, rear, left, and proper weight percentages. So until I bodily take away, shift, or add weight, Mission Tough can have these values.
Entrance Weight % =54.06%
Rear Weight % =45.95%
Left Weight % =53.23%
Proper Weight % =46.77%
Notice: I didn’t simulate my physique weight (84kg/185lbs) or disconnect the sway bars. In good follow, you completely ought to do that when establishing a race automotive or a automotive with extremely stiff springs. Minor tweaks can have a much bigger impact, and also you don’t need unintentional preload within the sway bars. Though Mission Tough has adjustable sway bar finish hyperlinks, and I’ve dialed them in for no preload, it isn’t a race automotive. We’re nonetheless doing this with lavatory scales no matter what number of variables we restrict.
What we can do is get our cross-weight to a perfect 50/50 state of affairs. Presently:
(Entrance Proper (kg) +Rear Left (kg)) / Complete Weight (kg) = Cross Weight %
(351.83kg+340kg) / 1439.27kg =Cross Weight %
48.07% = Cross Weight %
Anytime you could have a cross weight above 50%, you could have a wedge. Something beneath 50%, like Mission Tough, is a reverse wedge. Understanding this, you may observe these guidelines to regulate the trip peak to get nearer to a 50/50 distribution.
RAISING anybody nook will INCREASE the load on that nook and barely have an effect on all different corners.
LOWERING anybody nook will DECREASE the load on that nook and barely have an effect on all different corners.
Cross weight ABOVE 50% = DECREASE weight (peak) on FR/RL or INCREASE weight (peak) on FL/RR. – Wedge
Cross weight BELOW 50% = INCREASE weight (peak) on FR/RL or DECREASE weight (peak) on FL/RR – Reverse Wedge
Thus, I ought to work on growing the peak on the Entrance Proper – Rear Left or lowering the peak on the Entrance Left – Rear Proper. That is the place every part turns into hella-tedious. You additionally have to resolve how set you might be within the car’s trip peak. Once more, the stiffer the springs, the stronger the impression minor changes will make. Nevertheless, in case you are lifeless set on how the automotive appears to be like, you might need to compromise that fifty/50 distribution.
And that’s so that you can resolve. For me, as soon as I get Mission Tough again on the highway, I’ll do that once more and intention to get that fifty/50 cross weight distribution. I additionally need to check a couple of extra suspension initiatives and experiments.
This goes to point out that if you happen to’re not afraid of slightly little bit of math, you may unlock potential and knowledge that will in any other case be locked behind costly tools. It did take some refinement, and this nonetheless gained’t be as correct as an excellent set of digital scales, however in contrast to my first try at nook balancing with scales, it was a hit.
Digital scales would nonetheless be glorious, although…
Ron Celestine
Instagram: celestinephotography
