Nook balancing a automobile has been a type of issues that appeared off-limits to the common automotive DIY fanatic.
You will discover a variety of digital scales from a velocity store like Summit Racing; nevertheless, a ‘respectable’ set will set you again at the least $1,000, and a higher-quality set will value double that.
You should utilize the lavatory scale hack, the place you jack the automobile up and decrease it on a set of low-cost rest room scales. I even tried this again in 2020 with Challenge Tough, my ER34 Nissan Skyline GT-T, and had… average success.
To do that accurately, it’s essential to guarantee you’re engaged on a superbly flat floor. The automobile must be as degree as doable whereas on the scales – i.e., on some form of platform – and also you want a approach 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 mistaken. One among my scales broke as a consequence 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 had been nonetheless the one viable strategy.
Or Is It…
Quick-forward a couple of years, and I found a YouTube channel known as SuperfastMatt. Matt’s movies are as humorous as they’re insightful, and one known as I Invented a Higher Method to Weigh Your Automobile. And it’s Cheaper, Too. discusses how you should utilize leverage and a little bit of math to calculate the burden at any given nook.
You may have a supporting block wherein 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 dimensions. The burden will likely be considerably smaller, which shouldn’t max out the dimensions. If you recognize the gap from the supporting block and the gap to the dimensions, you may calculate the precise weight with the worth proven by the dimensions.
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 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 need.
I subsequent created a platform that might have the beam degree with the lavatory scale. I recorded the size (92.2cm). We are going to 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.
Not like 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 dimensions (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 may subtract that quantity from L2 and get the battery’s ‘middle’ 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 full size of the beam. If you recognize the gap relative to the beam, you may divide that quantity by the burden on the dimensions 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 realized this on the full-size take a look at, 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 take a look at. With this stable proof of idea, it was time to scale up.
Full Steam Forward
With Challenge 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 components, 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 degree to degree the platform with shims.
I used to be now able to nook steadiness Challenge Tough. I acquired my rest room scale out and ensured the beam and platform had been degree…
…And instantly bumped into an issue. Though I had calculated that if my bar had been 184cm lengthy, I’d have loads of area to drive on the beam and never max out the lavatory 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 further extrusions from numerous tasks at that very same 184cm size, I made a decision to strive that earlier than slicing 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 could max out the dimensions, 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 may transfer the dimensions 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 dimensions was 42.5kg (93.7lbs) (Fa).
It was now time to calculate the varied lengths as I had performed with the battery. Nonetheless, it was harder 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 either 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 thing that I noticed there was a neater approach to decide the tire’s contact patch…
You possibly can press a bit of flat scrap wooden anyplace in opposition to 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 greater within the rear (10cm). These could be the Lm values used within the calculations.
Seeing that I can immediately 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 gap 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 the complete quantity on my calculator (0.099722992). Then, we will calculate the pressure of the automobile at that nook.
F= Fa / Fl
F= 42.5kg.0997
F= 426.18kg
And similar to that, one nook is finished! Subsequent, roll the automobile again a bit, transfer the dimensions to the following tire, drive up, and crunch these numbers.
When you get the dangle of it, every nook takes about 5 minutes. In fact, if 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 might 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 line with the shakensho, my Skyline ought to weigh 1,460kg (3,218lbs). I’m unsure how they acquired that quantity (moist, dry, full tank of fuel, and so forth.), 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 Challenge Tough to a spot the place I can drive and weigh the automobile, however that must wait till it’s handed its shaken inspection.
What can we do with this newfound details about Challenge Tough‘s steadiness? A nook steadiness reveals your automobile’s weight distribution, which might then be manipulated to optimize dealing with. For individuals who are useless severe about getting one of the best lap time, you’ll manipulate this distribution by bodily eradicating weight or including ballast in strategic places to get nearer to that ‘supreme’ 50/50 distribution entrance to again and left to proper.
We will manipulate how a lot weight a nook receives by elevating or reducing it. Nonetheless, as one motion impacts all the opposite corners on the similar time, it isn’t doable to alter the entrance, rear, left, and proper weight percentages. So except I bodily take away, shift, or add weight, Challenge Tough can have these values.
Entrance Weight % =54.06%
Rear Weight % =45.95%
Left Weight % =53.23%
Proper Weight % =46.77%
Be aware: 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 can have an even bigger impact, and also you don’t need unintentional preload within the sway bars. Though Challenge 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 rest room scales no matter what number of variables we restrict.
What we can do is get our cross-weight to a super 50/50 scenario. At the moment:
(Entrance Proper (kg) +Rear Left (kg)) / Whole 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 Challenge Tough, is a reverse wedge. Understanding this, you may observe these guidelines to regulate the trip top 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 (top) on FR/RL or INCREASE weight (top) on FL/RR. – Wedge
Cross weight BELOW 50% = INCREASE weight (top) on FR/RL or DECREASE weight (top) on FL/RR – Reverse Wedge
Thus, I ought to work on rising the peak on the Entrance Proper – Rear Left or reducing the peak on the Entrance Left – Rear Proper. That is the place every thing turns into hella-tedious. You additionally have to determine how set you’re within the automobile’s trip top. Once more, the stiffer the springs, the stronger the impression minor changes will make. Nonetheless, if you’re useless set on how the automobile appears, you might need to compromise that fifty/50 distribution.
And that’s so that you can determine. For me, as soon as I get Challenge Tough again on the highway, I’ll do that once more and goal to get that fifty/50 cross weight distribution. I additionally wish to take a look at a couple of extra suspension tasks and experiments.
This goes to indicate that in case you’re not afraid of a little bit little bit of math, you may unlock potential and knowledge that might in any other case be locked behind costly gear. 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 successful.
Digital scales would nonetheless be wonderful, although…
Ron Celestine
Instagram: celestinephotography