Nook balancing a automotive 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 price 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 Challenge Tough, my ER34 Nissan Skyline GT-T, and had… reasonable success.
To do that accurately, you need to guarantee you might be engaged on a wonderfully flat floor. The automotive must be as stage as potential whereas on the scales – i.e., on some type of platform – and also you want a approach to calm down the arms after jacking the automotive 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 fallacious. One among my scales broke as a result 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 method removed from sensible. It appeared like devoted digital scales have been nonetheless the one viable method.
Or Is It…
Quick-forward a number 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 Automotive. And it’s Cheaper, Too. discusses how you need to use leverage and a little bit of math to calculate the burden at any given nook.
You will 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 load might be considerably smaller, which shouldn’t max out the dimensions. If you understand the space from the supporting block and the space to the dimensions, you’ll be able to 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 vehicles, I figured I’d let my internal 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 Earlier than going full ship, I made a decision to check it on a small scale with an outdated battery from the household Honda Stepwgn.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 go away lots to want.
I subsequent created a platform that may have the beam stage with the lavatory scale. I recorded the size (92.2cm). We’ll name this ‘L’.
Then I positioned the battery on the beam and received 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 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’ll be able to 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 overall size of the beam. If you understand the space relative to the beam, you’ll be able to 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 discovered this on the full-size check, however I attempted to maintain as many numbers after the decimal place as potential 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 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 automotive 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 Challenge Tough. I received 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 house 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 varied tasks at that very same 184cm size, I made a decision to strive that earlier than slicing the beams to a smaller measurement. 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 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 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 accomplished 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 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 all the things that I spotted there was a neater approach to decide the tire’s contact patch…
You’ll be able to press a chunk 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, hold as many locations as potential 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 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 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 line with the shakensho, my Skyline ought to weigh 1,460kg (3,218lbs). I’m undecided how they received 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 overall calculated weight is fairly rattling shut. Ideally, I’d take Challenge Tough to a spot the place I can drive and weigh the automotive, however that must wait till it’s handed its shaken inspection.
What can we do with this newfound details about Challenge Tough‘s stability? A nook stability exhibits your car’s weight distribution, which might then be manipulated to optimize dealing with. For many who are useless critical about getting the perfect lap time, you’d manipulate this distribution by bodily eradicating weight or including ballast in strategic places to get nearer to that ‘best’ 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 reducing it. Nonetheless, as one motion impacts all the opposite corners on the similar time, it isn’t potential to alter the entrance, rear, left, and proper weight percentages. So except I bodily take away, shift, or add weight, Challenge Tough may 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 organising a race automotive or a automotive with extremely stiff springs. Minor tweaks may have a much 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 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 super 50/50 scenario. Presently:
(Entrance Proper (kg) +Rear Left (kg)) / Whole 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 beneath 50%, like Challenge Tough, is a reverse wedge. Realizing this, you’ll be able to comply with 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 lowering the peak on the Entrance Left – Rear Proper. That is the place all the things turns into hella-tedious. You additionally must resolve how set you might be within the car’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 automotive seems to be, you might need to compromise that fifty/50 distribution.
And that’s so that you can resolve. For me, as soon as I get Challenge 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 number of extra suspension tasks and experiments.
This goes to indicate that should you’re not afraid of a bit little bit of math, you’ll be able to unlock potential and knowledge that may 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 a hit.
Digital scales would nonetheless be wonderful, although…
Ron Celestine
Instagram: celestinephotography
