Nook balancing a automobile has been a kind of issues that appeared off-limits to the common automotive DIY fanatic.
You could find a variety of digital scales from a pace store like Summit Racing; nonetheless, a ‘first rate’ set will set you again at the least $1,000, and a higher-quality set will value double that.
You need to use the toilet scale hack, the place you jack the automobile up and decrease it on a set of low-cost lavatory scales. I even tried this again in 2020 with Undertaking Tough, my ER34 Nissan Skyline GT-T, and had… reasonable success.
To do that appropriately, you need to guarantee you’re engaged on a wonderfully flat floor. The automobile must be as stage as doable whereas on the scales – i.e., on some type of platform – and also you want a technique to chill out the arms after jacking the automobile as much as transfer the scales into place.
It’s fairly the dance, and there are a bunch of variables the place issues can go flawed. One in every of my scales broke on account of going far past the utmost weight restrict of 130kg (286lbs).
So, measuring the burden in any respect 4 corners, making any changes, and having to carry out the entire circus once more made this system removed from sensible. It appeared like devoted digital scales have been nonetheless the one viable method.
Or Is It…
Quick-forward just a few 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 Solution to Weigh Your Automobile. And it’s Cheaper, Too. discusses how you should use leverage and a little bit of math to calculate the burden at any given nook.
You’ve a supporting block through which a beam rests on. The supporting block is a ‘X’ distances away from the toilet scale. You’ll then place the tire on the beam, and that weight transfers throughout the beam to the size. The load will probably be considerably smaller, which shouldn’t max out the size. If you understand the gap from the supporting block and the gap to the size, you possibly can 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 interior 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 Earlier than going full ship, I made a decision to check it on a small scale with an outdated battery from the household Honda Stepwgn.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 loads to need.
I subsequent created a platform that might have the beam stage with the toilet scale. I recorded the size (92.2cm). We are going to name this ‘L’.
Then I positioned the battery on the beam and bought 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 drive 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’d 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 possibly can subtract that quantity from L2 and get the battery’s ‘middle’ level of drive. 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 full size of the beam. If you understand the gap relative to the beam, you possibly can divide that quantity by the burden on the size to calculate the burden. I do know it’s getting a bit wild right here…
Fl=Lf /L
Fl=27.25cm / 92.2cm
Fl=.2955
I discovered 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 burden 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 strong proof of idea, it was time to scale up.
Full Steam Forward
With Undertaking Tough able to go, I made a decision to do an alignment, as I’d use the identical platform rig for the nook balancing.
For shaken, I needed to reinstall some OEM elements, which threw my alignment out of whack.
Bringing the automobile to my home from its storage spot was one of many sketchiest drives of my life. I adjusted my laser stage to stage the platform with shims.
I used to be now able to nook stability Undertaking Tough. I bought my lavatory scale out and ensured the beam and platform have been stage…
…And instantly bumped into an issue. Though I had calculated that if my bar have been 184cm lengthy, I’d have loads of area to drive on the beam and never max out the toilet scale, the burden 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 varied initiatives at that very same 184cm size, I made a decision to strive that earlier than reducing the beams to a smaller dimension. I used to be nonetheless afraid that if I had minimize the beams too quick and pushed too far on the beam, it will 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 automobile 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 check out 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 performed 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 underneath 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 little thing that I noticed there was a neater technique 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 technique. Amazingly, this technique matched my numbers for the entrance tires (9.7cm) however was barely increased 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 drive relative to the gap on the beam.
Fl=Lf / L
Fl=10.8cm / 108.3cm
Fl=.0997
Once more, hold as many locations as doable within the calculations. I saved all the quantity on my calculator (0.099722992). Then, we will calculate the drive of the automobile at that nook.
F= Fa / Fl
F= 42.5kg.0997
F= 426.18kg
And similar to that, one nook is completed! Subsequent, roll the automobile again a bit, transfer the size to the following tire, drive up, and crunch these numbers.
When you get the hold of it, every nook takes about 5 minutes. In fact, when you’ve got a number of scales and beams (I used to be nonetheless cautious and determined to not get extra beams to do that), you may do that entire course of in a single shot.
Listed here are the values that I got here up with after all of the calculations. In accordance with the shakensho, my Skyline ought to weigh 1,460kg (3,218lbs). I’m undecided how they bought that quantity (moist, dry, full tank of fuel, and so on.), 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 full calculated weight is fairly rattling shut. Ideally, I’d take Undertaking Tough to a spot the place I can drive and weigh the automobile, however that should wait till it’s handed its shaken inspection.
What can we do with this newfound details about Undertaking Tough‘s stability? A nook stability exhibits your automobile’s weight distribution, which might then be manipulated to optimize dealing with. For individuals who are useless critical about getting the very best lap time, you’ll manipulate this distribution by bodily eradicating weight or including ballast in strategic places 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 similar time, it isn’t doable to vary the entrance, rear, left, and proper weight percentages. So until I bodily take away, shift, or add weight, Undertaking Tough could have these values.
Entrance Weight % =54.06%
Rear Weight % =45.95%
Left Weight % =53.23%
Proper Weight % =46.77%
Observe: I didn’t simulate my physique weight (84kg/185lbs) or disconnect the sway bars. In good apply, you completely ought to do that when organising a race automobile or a automobile with extremely stiff springs. Minor tweaks could have a much bigger impact, and also you don’t need unintended preload within the sway bars. Though Undertaking Tough has adjustable sway bar finish hyperlinks, and I’ve dialed them in for no preload, it isn’t a race automobile. 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 an excellent 50/50 state of affairs. At the moment:
(Entrance Proper (kg) +Rear Left (kg)) / Complete Weight (kg) = Cross Weight %
(351.83kg+340kg) / 1439.27kg =Cross Weight %
48.07% = Cross Weight %
Anytime you will have a cross weight above 50%, you will have a wedge. Something under 50%, like Undertaking Tough, is a reverse wedge. Understanding this, you possibly can observe these guidelines to regulate the trip peak to get nearer to a 50/50 distribution.
RAISING anyone nook will INCREASE the burden on that nook and barely have an effect on all different corners.
LOWERING anyone nook will DECREASE the burden 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 reducing the peak on the Entrance Left – Rear Proper. That is the place every little thing turns into hella-tedious. You additionally must determine how set you’re within the automobile’s trip peak. Once more, the stiffer the springs, the stronger the influence minor changes will make. Nevertheless, in case you are useless set on how the automobile seems, you might need to compromise that fifty/50 distribution.
And that’s so that you can determine. For me, as soon as I get Undertaking Tough again on the street, I’ll do that once more and intention to get that fifty/50 cross weight distribution. I additionally wish to check just a few extra suspension initiatives and experiments.
This goes to point out that should you’re not afraid of slightly little bit of math, you possibly can unlock potential and knowledge that might in any other case be locked behind costly tools. It did take some refinement, and this nonetheless gained’t be as correct as a very good set of digital scales, however not like my first try at nook balancing with scales, it was a hit.
Digital scales would nonetheless be glorious, although…
Ron Celestine
Instagram: celestinephotography
